U.S. patent application number 10/786049 was filed with the patent office on 2005-02-03 for autonomous control system apparatus and program for a small, unmanned helicopter.
Invention is credited to Fujiwara, Daigo, Hazawa, Kensaku, Matsusaka, Keitaro, Nonami, Kenzo, Shin, Jin Ok.
Application Number | 20050027406 10/786049 |
Document ID | / |
Family ID | 33115241 |
Filed Date | 2005-02-03 |
United States Patent
Application |
20050027406 |
Kind Code |
A1 |
Nonami, Kenzo ; et
al. |
February 3, 2005 |
Autonomous control system apparatus and program for a small,
unmanned helicopter
Abstract
An objective of the invention, focusing on these issues involved
in the use of a small, hobby-type, unmanned helicopter, is to
develop an autonomous control system comprising autonomous control
systems for a small unmanned helicopter, to be mounted on said
small unmanned helicopter; a servo pulse mixing/switching unit; a
radio-controlled pulse generator; and autonomous control algorithms
that are appropriate for the autonomous control of the
aforementioned small unmanned helicopter, thereby providing an
autonomous control system that provides autonomous control on the
helicopter toward target values. The autonomous control system for
a small unmanned helicopter of the present invention comprises:
Sensors that detect the current position, the attitude angle, the
altitude relative to the ground, and the absolute azimuth of the
nose of the aforementioned small unmanned helicopter; A primary
computational unit that calculates optimal control reference values
for driving the servo motors that move five rudders on the
helicopter from the target position or velocity values that are set
by the ground station and the aforementioned current position and
attitude angle of the small unmanned helicopter that are detected
by the aforementioned sensors; An autonomous control system
equipped with a secondary computational unit that converts the data
collected by said sensors and the computational results as numeric
values that are output by said primary computational unit into
pulse signals that can be accepted by the servo motors, Such that
these components are assembled into a small frame box, thereby
achieving both size and weight reductions.
Inventors: |
Nonami, Kenzo; (Tokyo,
JP) ; Shin, Jin Ok; (Seoul, KR) ; Fujiwara,
Daigo; (Kasukabe-shi, JP) ; Hazawa, Kensaku;
(Hitachi-shi, JP) ; Matsusaka, Keitaro;
(Hiroshima, JP) |
Correspondence
Address: |
HAUPTMAN KANESAKA BERNER PATENT AGENTS, LLP
Suite 310
1700 Diagonal Road
Alexandria
VA
22314
US
|
Family ID: |
33115241 |
Appl. No.: |
10/786049 |
Filed: |
February 26, 2004 |
Current U.S.
Class: |
701/3 ;
244/17.13 |
Current CPC
Class: |
G05D 1/0033
20130101 |
Class at
Publication: |
701/003 ;
244/017.13 |
International
Class: |
G06F 017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 26, 2003 |
JP |
2003-049549 |
Claims
1. In a system that allows the autonomous control of a small
unmanned helicopter, an autonomous control system for a small
unmanned helicopter comprising: sensors that detect the current
position, the attitude angle, the altitude relative to the ground,
and the absolute azimuth of the nose of said small unmanned
helicopter; a primary computational unit that calculates optimal
control reference values for driving the servo motors that move
five rudders on the helicopter from target position or velocity
values that are set by the ground station and the aforementioned
current position and attitude angle of the small unmanned
helicopter that are detected by the aforementioned sensors; and a
secondary computational unit that converts the data collected by
said sensors and the computational results as numeric values that
are output by said primary computational unit into pulse signals
that can be accepted by servo motors.
2. In a system that allows the autonomous control of a small
unmanned helicopter, the autonomous control system for a small
unmanned helicopter of claim 1, wherein said sensors, said primary
computational unit, and said secondary computational unit are
assembled into a small frame box, thereby achieving both size and
weight reductions that permit the mounting of the frame box on said
small unmanned helicopter.
3. In a system that allows the autonomous control of a small
unmanned helicopter, the autonomous control system for a small
unmanned helicopter of claim 1, wherein the system has a ground
station host computer that has the same functionality as said
primary computational unit and wherein the autonomous control
system can also use said ground station host computer as it
performs said autonomous controls as necessary.
4. In a system that allows the autonomous control of a small
unmanned helicopter, the autonomous control system for a small
unmanned helicopter of claim 3, wherein when using said ground
station host computer as the primary computational unit for the
performance of said autonomous controls, the autonomous control
system outputs the computational results that are output by said
ground station host computer to said servo motors through a manual
operation transmitter.
5. In a system that allows the autonomous control of a small
unmanned helicopter, the autonomous control system for a small
unmanned helicopter of claim 4, wherein when said ground station
host computer is used as the primary computational unit for the
performance of said autonomous controls, for the process of
directing the computational results that are output from said
ground station host computer to said servo motors through a manual
operation transmitter, the autonomous control system is equipped
with a pulse generator that converts said computational results as
numerical values into pulse signals that said manual operation
transmitter can accept.
6. In a system that allows the autonomous control of a small
unmanned helicopter, the autonomous control system for a small
unmanned helicopter of claim 1, wherein, for the performance of
said autonomous controls, the autonomous control system is equipped
with a servo pulse mixing/switching apparatus as an external device
to said autonomous control system that receives control signals
that are output by said primary computational unit through said
secondary computational unit and that outputs them to said servo
motors.
7. The autonomous control system for a small unmanned helicopter of
claim 6, wherein the servo pulse mixing/switching apparatus, on all
said servo motors for said small unmanned helicopter, permits the
switching of manual operation signals and said control signals that
are output from said autonomous control system, or mixing thereof
in any proportion.
8. The autonomous control system for a small unmanned helicopter of
claim 6, wherein the servo pulse mixing/switching apparatus shares
the power supply system for said servo motors.
9. The autonomous control system for a small unmanned helicopter of
claim 6, wherein the servo pulse mixing/switching apparatus is
equipped with a safety feature that automatically restores the
computational unit for said switching and mixing that detects
anomalies if an anomaly occurs in the computational unit for
switching and mixing.
10. The autonomous control system for a small unmanned helicopter
of claim 6, wherein the servo pulse mixing/switching apparatus
automatically recognizes the connection status of signal wires and
whether or not a signal is present, and transmits appropriate
signals to said servo motors based on the recognition.
11. The autonomous control system for a small unmanned helicopter
of claim 6, wherein the servo pulse mixing/switching apparatus is
provided with a function that outputs manual operation signals that
are input into said servo pulse mixing/switching apparatus to said
autonomous control system.
12. The autonomous control system for a small unmanned helicopter
of claim 4 comprising: for the performance of autonomous control, a
servo pulse mixing/switching apparatus as an external device to
said autonomous control system that receives control signals that
are output from said primary computational unit through said
secondary computational unit and that outputs them to said servo
motors; wherein the servo pulse mixing/switching apparatus has the
function of directing the output of manual operation signals, which
are input into said servo pulse mixing/switching apparatus, to said
autonomous control system, and wherein, using this function, the
manual operation transmitter can be used as a target value input
apparatus for autonomous control purposes.
13. The autonomous control system for a small unmanned helicopter
of claim 1, wherein the primary computational unit calculates
optimal control reference values for the driving of servo motors
that operate the rudders for the small unmanned helicopter and the
primary computational unit performs tri-axial attitude control for
said small unmanned helicopter.
14. The autonomous control system for a small unmanned helicopter
of claim 13, wherein the primary computational unit uses the
following mathematical model for the transfer function
representation including pitching operation input and pitch axis
attitude angles in the tri-axis attitude control for said small
unmanned helicopter: 15 G ( s ) = - Ls K n s 2 ( s 2 + 2 ??? s s s
+ n s 2 ) ( T s + 1 ) s ( 13 ) such that the primary computational
unit calculates control reference values based on said model
equation.
15. The autonomous control system for a small unmanned helicopter
of claim 13, wherein the primary computational unit uses the
following mathematical model for the transfer function
representation including rolling input and roll axis attitude
angles for tri-axis attitude control: 16 G ( s ) = - Ls K n s 2 ( s
2 + 2 ??? s n s s + n s 2 ) ( T s + 1 ) s ( 14 ) such that the
primary computational unit autonomously controls said small
unmanned helicopter based on said model equation.
16. The autonomous control system for a small unmanned helicopter
of claim 13, wherein the primary computational unit uses the
following mathematical model for the transfer function
representation including yawing input and yaw axis attitude angles
for said tri-axis attitude control: 17 G ( s ) = - Ls K n s 2 ( s 2
+ 2 ??? s n s s + n s 2 ) s ( 15 ) such that the primary
computational unit autonomously controls said small unmanned
helicopter based on said model equation.
17. The autonomous control system for a small unmanned helicopter
of claim 13, wherein the primary computational unit uses the
following mathematical model for the transfer function
representation including pitch axis attitude angles and
longitudinal speeds in the translational motion control: 18 Vx = g
T s + T a s - a ( - ) ( 16 ) such that the primary computational
unit autonomously controls said small unmanned helicopter based on
said model equation.
18. The autonomous control system for a small unmanned helicopter
of claim 13, wherein the primary computational unit uses the
following mathematical model for the transfer function
representation including roll axis attitude angles and lateral
speeds in the translational motion control: 19 Vy = g T s + T a s -
a ( 17 ) such that the primary computational unit autonomously
controls said small unmanned helicopter based on said model
equation.
19. The autonomous control algorithm for a small unmanned
helicopter of claim 13, wherein the primary computational unit uses
the following mathematical model for the transfer function
representation of vertical speeds in the translational motion
control for said small unmanned helicopter: 20 Vz = k s t (18)such
that the primary computational unit autonomously controls said
small unmanned helicopter based on said model equation.
20. The autonomous control algorithm for a small unmanned
helicopter of claim 13, wherein the primary computational unit
autonomously controls said small unmanned helicopter by executing
independent autonomous control algorithms on the six physical
quantities of said small unmanned helicopter: pitch axis attitude
angle, roll axis attitude angle, yaw axis attitude angle,
longitudinal speed, lateral speed, and vertical speed.
21. The autonomous control algorithm for a small unmanned
helicopter of claim 13, wherein the primary computational unit
autonomously controls said small unmanned helicopter by
constituting the respective autonomous control algorithm as a type
1 servo system so that for the respective physical quantities of
said small unmanned helicopter, the steady-state deviation from any
target value will be zero.
22. The autonomous control algorithm for a small unmanned
helicopter of claim 21, wherein said small unmanned helicopter is
autonomously controlled by applying either linear quadratic
Gaussian (LQG) theory or linear quadratic integral (LQI) theory to
the autonomous control algorithms that are constituted as a type 1
servo system, by treating the respective autonomous control
algorithms as uncoupled transfer function representation
mathematical models.
23. The autonomous control algorithm for a small unmanned
helicopter of claim 13, wherein the primary computational unit
represents dynamic characteristics consisting of longitudinal
speeds and lateral speeds as mathematical models for which pitch
axis attitude angles and roll axis attitude angles are input
quantities, and by calculating the respective attitude angles that
are necessary for the effecting of arbitrary longitudinal and
lateral speeds.
24. The autonomous control algorithm for a small unmanned
helicopter of claim 13, wherein the primary computational unit
autonomously controls said small unmanned helicopter, in order to
move the position of said small unmanned helicopter to an arbitrary
position, by representing longitudinal target values, lateral
target values, and vertical target values as
follows:Vxref=.alpha.(Pxref-Px) (19)for a longitudinal target
value,Vyref=.alpha.(Pyref-Py) (20)for a lateral value,
andZref=.beta.(Pzref-Pz) (21)for a vertical target value.
25. The autonomous control algorithm for a small unmanned
helicopter of claim 13, wherein the primary computational unit for
said autonomous control system treats the mathematical model for
transfer function representation that describes the dynamic
characteristics of said servo motors that are contained in said
Equations 13 through 15 as 21 G s ( s ) = n s 2 ( s 2 + 2 s n s s +
n s 2 ) ( 22 ) by entering M-series signals (pseudo-white signals)
into said servo motors, by applying a ptechnologies ial space
identificaton method based on input/output relationships, by
determining the unknown parameters .omega..sub.ns and .zeta..sub.S
in Eq. 22, and by designing autonomous control algorithms based on
those values.
26. An autonomous control program for a small unmanned helicopter,
wherein the program causes the primary computational unit for the
autonomous control system for the small unmanned helicopter to
execute the following steps and causes it to compute optimal
control reference values in order to drive the servo motors for
said small unmanned helicopter: a step that receives detection
signals from sensors that detect the current position, attitude
angle, ground altitude, and absolute nose azimuth of the small
unmanned helicopter; a step that receives position or speed target
values that are transmitted from the ground station; a step that
determines optimal control reference values for driving the servo
motors that move a plurality of rudders for said small unmanned
helicopter from the current position and attitude angle for said
small unmanned helicopter that are detected by said sensors; and a
step that causes translational motion control and tri-axis attitude
control on the small unmanned helicopter based upon the results of
said computational processing.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to an autonomous control system for
small unmanned helicopters, and autonomous control algorithms that
control rudders for said small unmanned helicopter based on the
aforementioned mathematical models.
[0003] 2. Description of the Prior Art
[0004] Helicopters are flying bodies that have operating ranges
such as longitudinal motions, lateral motions, vertical motions,
and hovering, which are not exhibited by an aircraft; as such, they
have the advantage of being able to flexibly respond to various
situations. This advantage has led to the expectation of the
construction of small, unmanned helicopters for use in places that
are difficult or dangerous for manned operations, for example in
high-altitude work, such as the inspection of power transmission
lines, or in emergency rescue operations or the detection of land
mines. Previously, an autonomous control system using an unmanned
helicopter for agricultural chemical spray applications was
described in Patent Reference 1 listed below:
[0005] [Patent Reference 1]
[0006] Patent Disclosure 2000-118498
[0007] First, let us provide a logical explanation of the mechanism
of autonomous control for helicopters. Helicopters are the objects
of control; they are flying bodies that are capable of changing
their orientation by means of servo motor actions and are capable
of three-dimensional motions. The purpose of flying by autonomous
control is to move the helicopter according to positional and speed
target values. The required maneuvering follows the computational
results generated by calculation computer. In order to delegate the
piloting of a helicopter to a computer, the calculation computer
must have sensing and actuation functions. Devices that have the
function of sensing the various flight conditions of a helicopter
are called sensors. Actuators that move the helicopter's rudders by
receiving autonomous control signals that are generated by
determining control reference values based on computational results
from the computer and by converting these results into signals are
referred to as servo motors. The helicopter can be autonomously
controlled toward a given target value by means of a feedback
control loop that links "(sensor)--(calculation computer)--(servo
motor)--(helicopter), Reference FIG. 1".
[0008] Following is a description of autonomous control for a small
unmanned helicopter described in Patent Reference 1, with reference
FIG. 2 to drawings. This system can be divided into a mobile
station, which includes the helicopter and a ground station.
Mounted on the ground station are a helicopter body 101; a sensor
102 that detects the current position and attitude angle of the
helicopter body 101; servo motors 103 that move the rudders for the
helicopter body 101; a backup receiver 104 that receives manual
maneuver signals from a backup transmitter 110; and a wireless
modem that communicates with the ground station.
[0009] Employed in the sensor 1021 are the GPS (not shown in the
figure) that detects the current position of the helicopter body
101 and tri-axis orientation sensors (not shown in the figure) that
detect the tri-axial attitude angles of the helicopter body 101.
Installed on the ground station are a computer CPU 108 for the
input of reference values on which speed reference values are
entered; a computer CPU 109 for internal computation purposes; and
a backup transmitter 110 that permits the operator to perform
manual operations in the event of the occurrence of a dangerous
situation. The CPU 109 calculates position and attitude angle
reference values from target speed values, compares the results
with the current position, speed, and attitude angle obtained from
the sensors 102, and based on these results, calculates control
instruction values that bring the helicopter to the reference
values. By forming a feedback control loop by linking "(sensors
102)--(CPU 109)--(servo motors 103)--(helicopter body 101)"
(intervening components omitted), it is possible to effect the
autonomous control of the helicopter toward its reference
values.
[0010] Following is a description of the operation of the system.
The operator sets four speed reference values (Vx*, Vy*, Vz*,
.omega.*) consisting of longitudinal, lateral, vertical, and
rotational speeds, on the CPU 58. The CPU 59 integrates these speed
reference values with respect to time, obtaining a longitudinal
target position X*, a lateral target position Y*, a vertical target
position Z*, and a rotational target position (yawing angle)
.psi.*. Similarly, the CPU 59 differentiates the four speed
reference values (Vx*, Vy*, Vz*,.omega.*) and multiplies the
results by coefficients to calculate a target pitching angle
.theta.* and a target rolling angle .phi.*.The differences between
the target values that are set in this manner and the detected
values (.theta., .phi., .psi., .omega.) for the body attitude,
speed (X, Y, Z, Vx, Vy, Vz) that are detected by the sensors 52
consisting of the GPS and tri-axis attitude sensors that are
installed on the helicopter body 51 are calculated as follows:
.DELTA.X=X*-X
.DELTA.Y=Y*-Y
.DELTA.Z=Z*-Z
.DELTA.Vx=Vx*-Vx
.DELTA.Vy=Vy*-Vy
.DELTA.Vz=Vz*-Vz
.DELTA..theta.=.theta.*-.theta.
.DELTA..phi.=.phi.*-.phi.
.DELTA..psi.=.psi.*-.psi.
.DELTA..omega.=.omega.*-.omega.
[0011] Based upon these differences (errors), the CPU 109
calculates control reference values for the servo motors 103 that
move the rudders for the helicopter body 101. Four types of control
reference values are computed: elevator servo (longitudinal)
instruction, aileron servo (lateral) instruction, corrective servo
(vertical) instruction, and rudder servo (rotational) instruction.
After computing these four types of control reference values, the
CPU 109 supplies them to the aforementioned servo motors 103, and
performs feedback control on these operations until the differences
become zero (0).
[0012] Helicopters that are used in the aforementioned conventional
autonomous control system were originally intended for the spraying
of agricultural chemicals, with a maximum weight of approximately
30 kg. Although the aforementioned sensors and computational unit
for the aforementioned conventional autonomous control system are
large and heavy, the helicopter can adequately fly even when
carrying these items. The unloaded helicopter used in the
aforementioned conventional autonomous control system weighs
approximately 60 kg, and approximately 90 kg when fully loaded.
Therefore, such a helicopter cannot easily be carried. In addition,
in order to use the system, the helicopter must have a flight range
sufficiently larger than the actual helicopter, which limits the
range over which the helicopter can be deployed. In some cases,
manned helicopter operations involve a narrow space in which the
aforementioned conventional helicopter cannot negotiate. On the
other hand, the small unmanned helicopter of the present invention
refers to a helicopter that is comparable to, and compatible with,
commercially available hobby small-scale radio-controlled
helicopters in size and weight.
[0013] Although the above problem can be solved by effecting
autonomous control in such a helicopter, the smaller the weight of
a helicopter, the more difficult it is to control. In other words,
the autonomous control system is subject to stringent constraints
in terms of size and weight, and small helicopters tend to be
unstable in terms of dynamical properties. Therefore, with the
aforementioned conventional autonomous control system, it is
impossible to mount the autonomous control system on the
aforementioned small unmanned helicopter as is. Further, applying
the autonomous control algorithms for the aforementioned
conventional autonomous control system to the aforementioned small
unmanned helicopter as is does not guarantee adequate control
performance. Further, the calculation of a control instruction
value is a time-consuming process due to the large number of
computational steps involved in the determination of servo motor
control reference values; consequently, when one attempts to
achieve size reductions in the autonomous control system, one must
contend with the conflicting requirements of accommodating a large
number of computational steps and the stringent constraints imposed
on the capabilities of the computational equipment and the size of
the control program. Further, beyond the computational equipment,
the sensors are also subject to stringent constraints on size and
weight, which clearly adds difficulties to the construction of
small and lightweight autonomous control systems. There has not
been a successful development of an autonomous control system that
can be mounted and flown on the type of small unmanned helicopter
for which the present invention is intended.
[0014] The aforementioned conventional autonomous control system
does not include a ground altitude sensor that detects the altitude
of the helicopter with respect to the ground.
[0015] In such a case, it is impossible to detect the relative
distance between the helicopter and the ground in real-time.
Because a helicopter is a flying object that floats by rotating the
main blade at high speeds to blow the wind toward the ground, it
has the characteristic that its flying behavior netechnologies he
ground is significantly different from that in the sky.
Specifically, netechnologies he ground, compared with its behavior
in the sky, the helicopter tends to be unstable in terms of
orientation dynamic characteristics. Therefore, without a ground
altitude sensor, it is impossible to smoothly control the
helicopter's altitude so that its distance from the ground will
remain constant or to perform automatic landing/take-off controls
involving lifting off from the ground or descending to the
ground.
[0016] For the implementation of autonomous control for an unmanned
helicopter, it is desirable to install all of the minimum set of
devices necessary for autonomous control on the aforementioned
unmanned helicopter, which is a mobile station. The reason is that
if a ptechnologies of the minimum necessary equipment is not
mounted on the helicopter and intervention by the ground station is
required, a feedback control loop would have to be provided between
the ground station and the mobile station, which would require the
provision of wireless communication intervals within the feedback
loop. In such a case, if the wireless communications are cut off
for any reason, the logical structure of the control system would
collapse, which would not be desirable from the standpoint of
safety during flight operations. On the other hand, the small
unmanned helicopter addressed by the present invention is subject
to stringent constraints on payload, which rules out the use of a
sophisticated computer in the aforementioned computational unit for
the aforementioned autonomous control system. Although the use of
complex algorithms may be required as autonomous control
algorithms, in such a case, it would be fortuitous if a
sophisticated computer provided on the ground station can be used
in conjunction with the aforementioned computational unit. However,
there have not been cases where autonomous control systems that
permit the combined use of a computational unit built into an
autonomous control system and a computer on the ground station for
autonomous control algorithm computation purposes have been
developed.
[0017] The hobby radio-controlled helicopter of the class including
the small unmanned helicopter addressed by the present invention
incorporates commercially available servo motors and manual
operation transmitters/receivers that have been in use for a long
time and that have adequate track records. For the implementation
of autonomous control for the aforementioned small unmanned
helicopter, it is also advantageous from safety and compatibility
standpoints to use these commercially available servo motors and
manual operation transmitters/receivers. However, for hobby
radio-controlled helicopters, such products are designed based upon
the assumption that an operator maneuvers the helicopter manually.
Although manual operation is essential for backup purposes to deal
with dangerous situations, the implementation of autonomous control
requires that the servo motors receive autonomous control signals
from the aforementioned autonomous control system. In other words,
switching between manual operation signals and autonomous control
signals is essential. However, no switching devices have been
developed that specifically address the aforementioned servo motor
for hobby-type products. The manual operation transmitter for hobby
purposes is provided with a function of receiving external
operation signals that permit beginning operators to practice
piloting. When a ground station computer is used for the
computation of autonomous control algorithms in the autonomous
control system for the aforementioned small unmanned helicopter, it
is possible to drive the aforementioned servo motors for the
aforementioned small unmanned helicopter by providing autonomous
control computation results as external operation signals to the
aforementioned manual operation transmitter. However, the
aforementioned manual operation transmitter can only accept the
aforementioned external operation signals that are encoded in pulse
format. Therefore, the aforementioned autonomous control
computational results need to be converted into the pulse format.
However, no conversion equipment that can be directly connected to
the aforementioned ground station computer have been developed.
[0018] The so-called hobby-oriented radio-controlled helicopter,
which belongs to the class of small unmanned helicopters addressed
by the present invention, incorporates off-the-shelf servo motors
and a manual operation transceiver, which have been in use for
years and which have an adequate track record. For safety and
compatibility, it is beneficial to use these off-the-shelf servo
motors and manual operation transceivers in implementing autonomous
control in the aforementioned small unmanned helicopter. However,
hobby-oriented radio-controlled helicopters as products are
designed under the assumption that they are manually operated by
the operator. Since manual operation is the life line in the event
of an emergency situation during autonomous control, it is
essential for backup purposes. On the other hand, the
implementation of autonomous control requires the severance of
manual operation signals so that autonomous control signals are
transmitted from the control unit to the servo motors. However,
physically cutting off the signal line in order to sever manual
operation signals would completely disable manual operation.
Therefore, it is essential to be able to switch between the manual
operation signals and the autonomous control signals. However,
there have been no examples of switching units being developed for
switching the aforementioned servo motors as hobby-oriented
products.
[0019] Whereas the conventional unmanned helicopter provides a
similar switching function internally in a system that is mounted
on the helicopter, employing similar means in the present invention
would result in disadvantages in terms of the safety and
reliability of the autonomous small unmanned helicopter and the
compatibility with the hobby-oriented radio-controlled helicopter.
A prerequisite to solving this problem is the concept of treating
the aforementioned autonomous control unit as an add-in unit for
the hobby-oriented radio-controlled helicopter, and separating this
unit from the aforementioned small unmanned helicopter and from its
aforementioned manual operation system. To this end, the
aforementioned servo pulse mixing/switching unit, which would be
functionally highly related to the hobby-oriented manual operation
system, should be implemented as a stand-alone external unit
separate from the aforementioned autonomous control unit.
[0020] With the conventional autonomous unmanned helicopter, the
sole objective is to provide autonomous control of the helicopter;
no consideration is given to situations in which autonomous control
is inserted into manual operation by a human operator. The present
invention is based on the concept of using an autonomous control
unit as an auxiliary system for manual operation, i.e., as an
operator-assist unit, beyond simply implementing autonomous
controls. Various objectives and techniques can be considered for
achieving operational-assist. For example, if the objective is to
help the human operator to achieve step-wise improvements in manual
operation, in the initial stages of practicing helicopter
maneuvering, the percentage of autonomous control should be set
large, and this percentage should be reduced gradually so that, at
the end, maneuvering by complete manual operation with the absence
of autonomous control should be achieved. Therefore, in the
aforementioned servo pulse mixing/switching unit, it would be
convenient to provide and mix manual operation signals and
autonomous control signals in an arbitrary proportion, to be output
to the aforementioned servo motors. However, there have been no
cases of developing devices or software capable of mixing manual
operation signals and autonomous control signals in any proportion
in this manner.
[0021] The aforementioned servo pulse mixing/switching unit is the
key system in the operation system for the aforementioned small
unmanned helicopter. If the power for the system is stopped during
the flight, drive signals could not be output to the aforementioned
servo motors, even if the power is being supplied to other units,
such as the aforementioned autonomous control unit, the
aforementioned manual operation receiver, or the aforementioned
servo motors, with result that the crashing of the helicopter would
be unavoidable, leading to a potentially fatal accident. Essential
to the development of the aforementioned switching unit is the
installation of a computer for pulse processing and computation
purposes. It might appear that for improved reliability of the
system, stable power supply batteries for the system should be
provided independently. However, an increase in the number of
batteries can lead to human error, such as overlooking a dead
battery, forgetting to turn on the power supply switch, or wiring
errors due to increased wiring complexity. Flying the helicopter
under such conditions can directly result in an accident. In other
words, the safety and reliability necessary for practical
operations could not be assured. Therefore, at a minimum, the
possibility of accidents occurring due to human error related to
the power supply must be eliminated.
[0022] Since the aforementioned servo pulse mixing/switching unit
is a key unit in the operation system for the aforementioned small
unmanned helicopter, if the operation of this unit stops during the
flight, the crashing of the helicopter will be unavoidable,
potentially leading to a fatal accident. Therefore, barring
physical damage, in other cases, consistent, normal operation of
the unit must be guaranteed.
[0023] As described above, the aforementioned servo pulse
mixing/switching unit shares the power supply system with the
hobby-oriented servo motors and the manual operation receiver and
it is always used in an integral manner with these components.
Therefore, it is desirable for the unit to have a high degree of
affinity to the manual operation system comprised of such
components. Specifically, it is desirable that even when the
aforementioned autonomous control system is not powered on or there
is no wire connection between the aforementioned autonomous control
system and this unit, manual operation is always possible by means
of the same operating procedures as the hobby-oriented
radio-controlled helicopter, and this is also necessary from the
standpoint of maintaining compatibility with the hobby-oriented
radio-controlled helicopter. However, there have been no examples
of cases of development of an autonomous small unmanned helicopter
capable of supporting manual operation without an autonomous
control system.
[0024] Since manual operation is intrinsically independent from
autonomous control, it can be thought of as being completely
unrelated to autonomous control. However, in some cases, the
process of designing an autonomous control algorithm may require
the measurement of manual operation signals. The creation of
mathematical models in the present invention involves the use of
what is called system characterization, wherein the input signals
that are entered into the aforementioned servo motors for the
aforementioned small unmanned helicopter are associated with the
output signals indicating the flying condition of the
aforementioned small unmanned helicopter, the output signals being
measured by the sensors that are installed in the aforementioned
autonomous control system, and analyzing these data so as to obtain
a mathematical model. The system characterization process requires
the collection of input/output data while the aforementioned small
unmanned helicopter is flying, and this process is called a
characterization experiment. Conducting a characterization
experiment requires the operation of the aforementioned servo
motors by means of characterization input signals that are well
suited for system characterization. In such a case, the use of
characterization input alone can cause a significant tilt in the
attitude of the aforementioned small unmanned helicopter or a
sudden acceleration, potentially leading to an accident. Therefore,
it is necessary to stabilize the motion of the aforementioned small
unmanned helicopter by actuating the correction rudders by manual
operation. However, because correction rudders are also considered
to be a part of characterization input, the aforementioned manual
operation signals must also be obtained as measurement data during
the system characterization process.
[0025] As stated above, the present invention also takes into
consideration the use of the aforementioned autonomous control
system as an auxiliary system for manual operation, i.e., an
operator assist unit. As an objective and technique of operation
assistance, manual operation signals, for example, could be
associated with target value input signals for the aforementioned
autonomous control algorithm, so that drive signals that are
actually output to the aforementioned servo motors are all used as
autonomous control signals, which are the results of computation by
the aforementioned autonomous control algorithm. In other words,
although the human operator may have the illusion of operating the
helicopter himself, in actuality, all the human operator does is
provide motion commands, which are target values, to the
aforementioned autonomous small unmanned helicopter, and in this
method, the aforementioned autonomous control algorithm is computed
upon receipt of the target values, and autonomous control is
effected. Because this method permits the provision of target
values to the aforementioned autonomous control algorithm without
using the aforementioned ground station computer, it provides the
significant benefit of enabling persons not versed in computer
operations to safely fly the aforementioned small unmanned
helicopter in a manner that takes advantage of autonomous control.
Such an approach requires the new technique of associating the
aforementioned manual operation signals with target values.
[0026] The development of autonomous control algorithms for the
autonomous control of the aforementioned small unmanned helicopter
requires mathematical models that describe the dynamic
characteristics of the helicopter. The use of mathematical models
permits the application of various control theories, which have
been improved in recent years and whose effectiveness has been
recognized, to the development of autonomous control algorithms,
which should improve flight performance in situations in which the
aforementioned small unmanned helicopter is controlled
autonomously.
[0027] However, the dynamic characteristics of a helicopter are
subject to a complex interplay of dynamic action and fluid dynamic
action, which makes analysis an extremely difficult task. Although
a detailed analysis of the dynamic characteristics of manned
helicopters has been pursued aggressively, but little detailed
analysis has been performed with regard to helicopters of the size
addressed in the present invention. In addition, there have been no
reports on the dynamic characteristics of the aforementioned servo
motors.
[0028] Even if a mathematical model that describes the dynamic
characteristics of the aforementioned small unmanned helicopter in
detail exists, if the mathematical model is highly complex, the
development of an autonomous control algorithm will also be
difficult. Autonomous control algorithms developed and based on
complex mathematical models are generally complex and may not
necessarily be appropriate for execution by a computer that is
subject to stringent restrictions on its computational capabilities
due to weight limitations.
[0029] There is a system identification method that avoids
theoretical analyses and draws inferences on the dynamic
characteristics of a given physical system based on its
input/output relationships. System identification requires the
input of signals containing frequency components encompassing a
broad bandwidth into the physical system. However, entering such
signals into the aforementioned small unmanned helicopter involves
risk. In addition, such a system will also require devices for the
measurement of the aforementioned input/output signals and an
instrumentation system. There have been no cases in which system
identification is run on the type of small unmanned helicopter
addressed in the present invention and in which the soundness of
the characterization model thus obtained is validated.
SUMMARY OF THE INVENTION
[0030] An objective of the present invention, focusing on these
issues involved in the use of a small, hobby-type, unmanned
helicopter, is to develop an autonomous control system comprising
autonomous control systems for a small unmanned helicopter, to be
mounted on said small unmanned helicopter; a servo pulse
mixing/switching unit; a radio-controlled pulse generator; and
autonomous control algorithms that are appropriate for the
autonomous control of the aforementioned small unmanned helicopter,
thereby providing an autonomous control system that provides
autonomous control on the helicopter toward target values.
[0031] The autonomous control system for a small unmanned
helicopter of the present invention comprises: sensors that detect
the current position, the attitude angle, the altitude relative to
the ground, and the absolute azimuth of the nose of the
aforementioned small unmanned helicopter; a primary computational
unit that calculates optimal control reference values for driving
the servo motors that move five rudders on the helicopter from the
target position or velocity values that are set by the ground
station and the aforementioned current position and attitude angle
of the small unmanned helicopter that are detected by the
aforementioned sensors; an autonomous control system equipped with
a secondary computational unit that converts the data collected by
said sensors and the computational results as numeric values that
are output by said primary computational unit into pulse signals
that can be accepted by the servo motors, such that these
components are assembled into a small frame box, thereby achieving
both size and weight reductions.
[0032] A ground station host computer that can also be used as the
aforementioned computational unit for the aforementioned autonomous
control system;
[0033] if the aforementioned ground station host computer is used
as the aforementioned computational unit for the aforementioned
autonomous control system,
[0034] in the process of directing the computational results that
are output from said ground station host computer to said servo
motors through a manual operation transmitter, a pulse generator
that converts said computational results as numerical values into
pulse signals that said manual operation transmitter can
accept;
[0035] a servo pulse mixing/switching apparatus, on all said servo
motors for said small unmanned helicopter, that permits the
switching of manual operation signals and said control signals that
are output from said autonomous control system or mixing thereof in
any ratio;
[0036] An autonomous control algorithm wherein the mathematical
model for transfer function representation encompassing pitching
operation input through pitch axis attitude angles in the tri-axis
attitude control for said small unmanned helicopter is defined as 1
G ( s ) = - Ls K n s 2 ( s 2 + 2 ??? s s s + n s 2 ) ( T s + 1 )
s
[0037] such that the aforementioned small unmanned helicopter is
controlled autonomously based on the aforementioned mathematical
model;
[0038] an autonomous control algorithm wherein the mathematical
model for transfer function representation encompassing rolling
input through roll axis attitude angles for the aforementioned
tri-axis attitude control is defined as 2 G ( s ) = - Ls K n s 2 (
s 2 + 2 ??? n s s + n s 2 ) ( T s + 1 ) s
[0039] such that the aforementioned small unmanned helicopter is
controlled autonomously based on the aforementioned mathematical
model;
[0040] an autonomous control algorithm wherein the mathematical
model for transfer function representation encompassing yawing
input through yaw axis attitude angles for the aforementioned
tri-axis attitude control is defined as 3 G ( s ) = - Ls K n s 2 (
s 2 + 2 ??? s n s s + n s 2 ) s
[0041] such that the aforementioned small unmanned helicopter is
controlled autonomously based on the aforementioned mathematical
model;
[0042] an autonomous control algorithm wherein the mathematical
model for transfer function representation encompassing pitch axis
attitude angles through longitudinal speeds in the translational
motion control for the aforementioned small unmanned helicopter is
defined as 4 Vx = g T s + T a s - a ( - )
[0043] such that the aforementioned small unmanned helicopter is
controlled autonomously based on the aforementioned mathematical
model;
[0044] an autonomous control algorithm wherein the mathematical
model for transfer function representation encompassing roll axis
attitude angles through lateral speeds in the translational motion
control for the aforementioned small unmanned helicopter is defined
as 5 Vy = g T s + T a s - a
[0045] such that the aforementioned small unmanned helicopter is
controlled autonomously based on the aforementioned mathematical
model;
[0046] an autonomous control algorithm wherein the mathematical
model for the transfer function representation of vertical speeds
in the translational motion control for the aforementioned small
unmanned helicopter is defined as 6 Z = k s t
[0047] such that the aforementioned small unmanned helicopter is
controlled autonomously based on the aforementioned mathematical
model;
[0048] an autonomous control algorithm wherein the longitudinal
speed target value for the aforementioned small unmanned helicopter
is defined as
Vxref=.alpha.(Pxref-Px)
[0049] such that the aforementioned small unmanned helicopter is
controlled autonomously;
[0050] an autonomous control algorithm wherein the lateral speed
target value for the aforementioned small unmanned helicopter body
is defined as
Vyref=.alpha.(Pyref-Py)
[0051] such that the aforementioned small unmanned helicopter is
controlled autonomously; and
[0052] an autonomous control algorithm wherein the vertical speed
target value for the aforementioned small unmanned helicopter body
is defined as
Vzref=.beta.(Pzref-Pz)
[0053] such that the aforementioned small unmanned helicopter is
controlled autonomously.
[0054] such that the aforementioned five rudders are moved by
independently controlling the aforementioned respective servo
motors. By using this autonomous control system, it is possible to
effect the complete autonomous control of a small unmanned
helicopter, comparable to a hobby-type small radio-controlled
helicopter, according to target values.
[0055] Because complete autonomous control can be implemented in a
hobby-type small radio-controlled helicopter, the helicopter is
convenient to carry, and can be adapted to narrow spaces that are
difficult to deal with on the basis of manned operations, which
could not be accommodated by the autonomous control for
conventional unmanned helicopters. In this manner, the use of such
a helicopter can be expanded.
BRIEF DESCRIPTION OF THE DRAWING
[0056] The features and advantages of the present invention will be
apparent from the following description of an exemplary embodiment
of the invention and the accompanying drawing, in which:
[0057] FIG. 1 is a feedback control loop system
[0058] FIG. 2 is a configuration of autonomous control system using
conventional unmanned helicopter system
[0059] FIG. 3 is a configuration of autonomous control system using
autonomous control device of small, unmanned helicopter of the
invention
[0060] FIG. 4 is a coordinate system of small, unmanned helicopter
of the invention
[0061] FIG. 5 is a simulated and experimental results of pitch axis
of the invention
[0062] FIG. 6 is a simulated and experimental results of roll axis
of the invention
[0063] FIG. 7 is a simulated and experimental results of yaw axis
of the invention
[0064] FIG. 8 is an experimental results of pitch angle, roll angle
and yaw angle with control of the invention
[0065] FIG. 9 is a relation between attitude angle and body
acceleration
[0066] FIG. 10 is a simulated and experimental results
[0067] FIG. 11 is a configuration of position control loop in the X
and the Y directions
[0068] FIG. 12 is an experimental result of trajectory following
control by control algorithm
[0069] FIG. 13 is an experimental result of fixed hovering
control
[0070] FIG. 14 is an experimental results of lateral and
longitudinal velocity control
[0071] FIG. 15 is an experimental results of altitude control
[0072] FIG. 16 is an internal structure of servo pulse
mixing/switching device
[0073] FIG. 17 is a configuration of control system using manual
piloting signal transmitter as reference input device
[0074] FIG. 18 is a Configuration of convert system to the control
signal from control referenece signal using pulse generator
device
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0075] The inventor of the present invention has consistently
pursued autonomous control research from the design of the
requisite hardware through the development of autonomous control
algorithms. The inventor developed the aforementioned autonomous
control system, the aforementioned radio-controlled pulse
generator, the hardware for the aforementioned servo pulse
mixing/switching unit, and the software on a novel and independent
basis. In addition, the inventor conducted flight experiments for
the characterization of the aforementioned mathematical models,
derived mathematical models from the experimental results, and
developed autonomous control algorithms for the small unmanned
helicopter using the mathematical models. By using the autonomous
control system, the inventor successfully achieved the complete
autonomous control of a small helicopter body, with an unloaded
weight of approximately 9 kg, according to target values.
[0076] In what follows, we provide a logical explanation of the
hardware for the autonomous control of the small unmanned
helicopter, and then describe research accomplishments on the
tri-axial attitude control of the helicopter body and autonomous
control algorithms for cruise speed/position control.
[0077] The helicopter body used in this invention is a helicopter
with a size and weight comparable to those of small
radio-controlled helicopters that are commercially available for
hobby purposes. Its empty weight is approximately 9 kg. Using this
small unmanned helicopter, the present invention can be applied to
operations that are performed at a high altitude, such as the
inspection of power transmission lines, to emergency rescue
operations, to the detection of land mines, or to operations
performed in narrow spaces that are too difficult or dangerous for
human operators to perform. The small unmanned helicopter, which is
the object of control, is a flying object whose orientation can be
changed by the operation of five servo motors and which can be
moved three-dimensionally.
[0078] The purpose of flight based on autonomous control, as in the
aforementioned prior technologies, is to move the helicopter
according to position and speed target values, and the maneuvering
of the helicopter obeys the autonomous control algorithms based on
mathematical models that have been developed by the inventor. The
aforementioned autonomous control algorithms are installed on the
calculation computer for the autonomous control system developed by
the inventor, wherein the results of computations generated by the
aforementioned calculation computer provide control signals for the
respective servo motors.
[0079] In order to delegate the piloting of a helicopter to a
computer, the calculation computer must be endowed with sensing and
actuation functions. Devices that have the function of sensing the
various flight conditions of a helicopter are called sensors.
Actuators that move the helicopter's rudders by receiving
autonomous control signals that are generated by determining
control reference values based on computational results from the
computer and by converting them into signals are referred to as
servo motors. By building an autonomous control system comprised of
these components and mounting it on the helicopter body, it is
possible to form a feedback control loop that links
"(sensor)--(calculation computer)--(servo motor)--(helicopter)", as
shown in FIG. 1.
[0080] The inventor of the present invention has developed an
autonomous control system, which is a piece of hardware, as a
platform that permits the autonomous control of the aforementioned
small unmanned helicopter. Because the aforementioned servo motors
among the pieces of hardware that make up the autonomous control
system are incorporated into the body of the aforementioned small
unmanned helicopter, the aforementioned autonomous control system
contains built-in sensors and computational units. Sensors that are
incorporated into a conventional autonomous control system include
tri-axis attitude sensors that detect the orientation of the
helicopter and the Global Positioning System (GPS) that detects the
current position of the helicopter. In addition, the autonomous
control system of the present invention incorporates a ground
altitude sensor that detects the distance between the body of the
aforementioned small unmanned helicopter and the ground surface,
and this permits the use of an autonomous control algorithm that
utilizes the altitude with respect to the ground as sensor
information. The autonomous control system also incorporates the
primary computational unit, which is a computation CPU used for the
implementation and calculation of autonomous control algorithms, as
well as a secondary computational unit, which is a CPU that
collects and processes data from the aforementioned sensors, and
converts the aforementioned computational results into control
signals. Efforts to reduce the size and weight of the autonomous
control system create a problem of stringent restrictions on the
functionality and processing speeds of the computational unit. We
solved this problem by diving the computational unit into two
ptechnologies, the primary computational unit and a secondary
computational unit, wherein the secondary computational unit is
assigned the role of all computations with the exception of
autonomous control algorithms, and the primary computational unit
is allowed to concentrate on the computation of autonomous control
algorithms. In addition, the autonomous control system incorporates
a power supply unit that outputs power with a voltage required by
the aforementioned sensors and the aforementioned computational
units, as well as a wireless modem that communicates with the
ground station. The aforementioned power supply unit takes a DC
power supply of a positive voltage as input and can supply power at
three voltages, including a negative voltage. The aforementioned
wireless modem comprises two sets, wherein one set is used for the
exchange of control information with the ground station host
computer, and the other set for the exchange of supplementary
information that improves the accuracy of GPS current position
information. The autonomous control system of the present
invention, which is designed under the assumption that it would be
installed on the aforementioned small unmanned helicopter, must
necessarily be small and lightweight. The aforementioned small
unmanned helicopter of the present invention has an approximate
maximum payload of only 5 kg. Therefore, in constructing the
autonomous control system, the inventor of the present invention
excluded any extraneous components that would lead to an increase
in weight or size. Based upon this consideration, the inventor
assembled the aforementioned sensors, the aforementioned
computational units, the aforementioned power supply unit, and the
aforementioned wireless modem into a small frame box of W 190
mm.times.D 290 mm.times.H 110 mm, and thus succeeded in the
development of an autonomous control system with an approximate
weight of 2.9 kg. For batteries, we adopted a commercially
available high-capacity lithium ion battery, approximately 700 g in
weight, for notebook personal computers, which assured a continuous
operating time of approximately 1 hour when fully charged.
Including stays and other accessories for installing the unit of
the aforementioned small unmanned helicopter, a weight reduction
extensive enough to fall within the aforementioned maximum payload
was accomplished for this autonomous control system.
[0081] Although the aforementioned autonomous control system of the
present invention has an adequate autonomous control algorithm
computational capacity, to provide for the future possibility of
loading more complex autonomous control algorithms that cannot be
handled by the aforementioned primary computational unit, the
inventor of the present invention made provisions for the use of a
ground station host computer for the computation of autonomous
control algorithms so that a computer significantly more powerful
than the aforementioned primary computational unit can be employed.
This arrangement permits various operating modes, such as a mode in
which, for example, attitude control is loaded on the
aforementioned primary computational unit of the aforementioned
autonomous control system and everything else is loaded on the
aforementioned ground station host computer, and a mode in which
only the autonomous control algorithm related to some of the servo
motors is loaded on the aforementioned primary computational unit
of the aforementioned autonomous control system and autonomous
control algorithms for any other servo motors are loaded on the
aforementioned ground station host computer, in addition to the
operating mode in which all autonomous control algorithms are
loaded on the aforementioned ground station host computer, thereby
substantially improving the expansion potential of the
aforementioned autonomous control system.
[0082] The manual operation transmitter for hobby purposes is
provided with a function of receiving external operation signals
that permits beginning operators to practice piloting. When a
ground station computer is used for the computation of autonomous
control algorithms, it is possible to drive the aforementioned
servo motors for the aforementioned small unmanned helicopter by
providing autonomous control computation results as external
operation signals to the aforementioned manual operation
transmitter. Further, by using the aforementioned servo pulse
mixing/switching unit, it is possible to drive the aforementioned
servo motors by first transmitting the aforementioned external
operation signals to the aforementioned autonomous control system
to generate another computational processing, instead of driving
the aforementioned servo motors directly by means of the
aforementioned external operation signals.
[0083] The aforementioned manual operation transmitter can only
accept the aforementioned external operation signals that are
encoded in pulse format. Therefore, the aforementioned autonomous
control computational results need to be converted into the pulse
format. However, no conversion equipment that can be directly
connected to the aforementioned ground station computer has been
developed.
[0084] In view of this fact, the inventor of the present invention
developed a radio control pulse generator unit that converts
computational results, in the form of numerical values that are
output from the aforementioned ground station host computer, into
the aforementioned pulse signal format that can be accepted by the
aforementioned manual operation signal transmitter. This unit uses
the RS-232C type serial communication method on the input side,
which is a common data communication technique, and thus can be
used on almost any existing computer. For the power supply, the
unit uses the power that is supplied by the aforementioned manual
operation transmitter, which eliminates the need for providing a
special power supply for the operation of the unit, thus
facilitating the handling of the unit. In addition, the unit is
endowed with functions that feed the number of maneuvering
operations and switching states of the aforementioned manual
operation transmitter to the aforementioned computer.
[0085] For the present invention, we developed a servo pulse
mixing/switching unit that permits a switch over to manual
operation in the event of an emergency situation during autonomous
control so that the aforementioned small unmanned helicopter can
fly safely. The following is a description of how the
aforementioned servo pulse mixing/switching unit works, with
reference to FIG. 16. The servo pulse mixing/switching unit 7, by
means of a pulse-processing computation CPU71 that is built in the
unit, processes the pulse signals that are transmitted from the
manual operation receiver 6 and the secondary computational unit 42
of the autonomous control unit, and generates servo pulse signals
to be output to the servo motors 3. The pulse signals that are
input from the manual operation signal receiver 6 into the servo
pulse mixing/switching unit 7 are composed of manual operation
signals, switching instruction signals between the manual operation
and autonomous control modes, and mixing ratio instruction signals
between manual operation and autonomous control signals. On the
other hand, the pulse signals that are input from the secondary
computing unit 42 of the autonomous control system into the servo
pulse mixing/switching unit 7 are autonomous control signals. The
servo pulse mixing/switching unit 7 recognizes the switching
instruction signals and the mixing ratio instruction signals. Based
on these signals, the servo pulse mixing/switching unit mixes
manual operation signals and the autonomous control signals that
are generated in the secondary computing unit 42 in an arbitrary
ratio, generates servo pulse signals based on the ratio, and can
output the results to the aforementioned servo motors 3.
Construction of the servo pulse mixing/switching unit 3 in this
manner has made it possible to switch between manual operation
signals and autonomous control signals dynamically at any time
during the flight. In view of the essential requirements for size
and weight reductions for this unit, as in the case of the
aforementioned autonomous control system, we achieved a weight
reduction to a final weight of only 250 g.
[0086] In the present invention, the aforementioned servo pulse
mixing/switching unit 7 is provided with the function of mixing
manual operation signals and autonomous control signals in an
arbitrary ratio. This will be described with reference to FIG. 16.
To mix manual operation signals and autonomous control signals, a
mixing signal instruction signal that provides a mixing ratio is
also input into the unit. As may be understood from the figure, the
mixing ratio instruction signal can also be supplied by the manual
operation signal transmitter. The pulse-processing computational
CPU71 recognizes the mixing ratio instruction signal, determines
the mixing ratio, and based on this ratio, performs calculations
for mixing manual operation signals and autonomous control signals,
generates the aforementioned serve pulse signals, and can drive
each of the servo motors 3. In this manner, the present invention
permits the use of the aforementioned autonomous control system as
a manual operation assist unit, endowed with a function for the
step-wise development of manual operation skills. Because the
mixing can be accomplished in any ratio, when the operator is not
versed in the operation of the radio-controlled helicopter, the
relative weight of autonomous control signals and manual operation
signals can be adjusted in favor of autonomous control so that
autonomous control signals can take recovery action if the operator
performs unskilled maneuvering to prevent the helicopter from
crashing, and as the operator becomes used to the operation of the
radio-controlled helicopter, the relative weight can be adjusted in
favor of manual operation. In this manner, the invention permits
gradual improvements in the manual operation of the
radio-controlled helicopter.
[0087] The present invention is designed so that the aforementioned
servo pulse mixing/switching unit is permitted to draw its power on
a shared basis from the power supply for the manual operation
system. In FIG. 16, the power supply for the manual operation
system is the battery 61. The power is supplied to the
aforementioned servo pulse mixing/switching unit 7 through the
signal lines for the manual operation signal, the switching
instruction, or the mixing ratio instruction that is input from the
manual operation signal transmitter 8 into the aforementioned servo
pulse mixing/switching unit 7. In addition, the power is supplied
to the aforementioned servo motors 3 through the inside of the body
of the aforementioned servo pulse mixing/switching unit 7. This
eliminates the need for excessively increasing the number of
batteries, prevents the problem of missing a dead battery by
oversight, forgetting to turn the power switch on, or
mis-connecting the wires due to increased complexity of wiring and
other types of human error, and thus enhances the safety of the
autonomous control system for the aforementioned small unmanned
helicopter at the practical level. With regard to the sharing of
the power supply, there is a basis for sharing the power supply for
the aforementioned manual operation system rather than the
aforementioned autonomous control unit. The reason is that if the
power supply for the aforementioned manual operation system runs
down, the aforementioned servo motors 3 will also cease to operate,
with the result that even when the power is being supplied to the
autonomous control unit, the aforementioned small unmanned
helicopter will become inoperable. Also, to maintain compatibility
between the small unmanned helicopter and the hobby-oriented
radio-controlled helicopter, it is necessary to keep manual
operation enabled even when the power for the autonomous control
unit is cut off.
[0088] In addition, in order to maintain the reliability of the
manual operation system also through the introduction of the
aforementioned servo pulse mixing/switching unit into the manual
operation system, the present invention incorporates into the
aforementioned servo pulse mixing/switching unit 7 a mechanism that
automatically detects any malfunction of the pulse-processing
computational CPU71, which is the key to the aforementioned servo
pulse mixing/switching unit that automatically restores the CPU,
and immediately returns it to the original operating condition.
Built into the aforementioned pulse-processing computational CPU71
is a timer unit 72 with the function of resetting the
aforementioned pulse-processing computational CPU71, and this timer
is used actively. The pulse-processing computational program, which
is written into the aforementioned servo pulse mixing/switching
unit 7 inputs at fixed time intervals a normal operation
notification signal indicating the state of normal operation into
the aforementioned timer unit 72. Malfunctioning of the
aforementioned pulse-processing computational CPU71 disables the
input of the aforementioned normal operation notification signal
into the aforementioned timer unit 72. If a certain length of time
elapses in this condition, the aforementioned timer unit 72
automatically inputs a reset signal to the aforementioned
pulse-processing computational CPU71, and effects a recovery
through a process similar to the power-on process. The reliable
operation of this function required the development of the
processing structure for the aforementioned pulse-processing
computational program under the assumption that the function will
be used. Specifically, we developed a program having a structure
wherein the processing component that transmits normal operation
notification signals to the aforementioned timer unit is completely
separated from the pulse input/output data unit which has a high
priority level and which has the potential of being called even in
the midst of a malfunction of the pulse-processing computational
CPU71. This permits the reliable detection of abnormal operating
conditions of the pulse-processing computational CPU71. It should
be noted that the length of time between the occurrence of a
malfunction to the issuance of a reset signal can be specified in
the aforementioned pulse-processing computational program. All
operations from the time a reset signal is input to the time the
system is recovered are performed automatically and
instantaneously. In this manner, the aforementioned
pulse-processing computational CPU71 can be restored in a matter of
dozens or hundreds of milliseconds from the time a malfunction
occurred. The assurance of continuously normal operations in terms
of software ensures the safety and reliability of the
aforementioned servo pulse mixing/switching unit.
[0089] In this invention, we developed for the aforementioned servo
pulse mixing/switching unit a function that automatically
recognizes the line connection status of the manual operation
signals, switching instruction signals, mixing ratio instruction
signals, and autonomous control signals for the signal lines that
are connected to the aforementioned servo pulse mixing/switching
unit 7, and the presence or absence of pulse signals that are input
into the aforementioned servo pulse mixing/switching unit through
these signal lines, as well as a function that generates
appropriate servo pulse signals according to the conditions that
are detected. The pulse-processing computational CPU71 continuously
measures the manual operation signals, switching instruction
signals, mixing ratio instruction signals, and autonomous control
signals of the pulse signals that are input. If measured values on
these pulse signals indicate an abnormal value, the
pulse-processing computational software determines whether the
signal line associated with the pulse signal is loose or the pulse
signal has become extinct. Specifically, if switching instruction
signals cease, all servo motors are forced to turn to the manual
operation mode; if autonomous control signals cease, the affected
servo motor 3 is forced to turn to the manual operation mode; if
mixing ratio instruction signals cease, no arbitrary-ratio mixing
is performed and the servo pulse mixing/switching unit operates
solely in the switching function; and if manual operation signals
cease, the affected serve motor is forced to turn to the autonomous
control mode. Moreover, if all signals cease to be supplied, the
software is programmed so that the servo motors will maintain the
last operating status that was in effect. In this manner, even when
the aforementioned autonomous control system is in a power-off
condition, i.e., in a condition where no autonomous control signals
are being supplied, the helicopter can be operated manually,
similar to a hobby helicopter, provided that the power is supplied
to the manual operation system. In addition, in the event of
failure to supply autonomous control signals due to a dead power
supply battery for the aforementioned autonomous control system in
the midst of autonomous control by the aforementioned autonomous
control system, the extinction of the autonomous control signals is
instantaneously recognized and the system is switched over to
manual operation. In this manner, helicopter crashing accidents can
be prevented by means of manual operation by the operator. In other
words, the manual operation system does not depend on the presence
or absence of the autonomous control system, and the autonomous
control system does not affect the manual operation system at all.
Thus, the use of this functionality has permitted the
implementation of the separation of the two signal systems in a
safe manner.
[0090] In this invention, the aforementioned servo pulse
mixing/switching unit is provided with a function that converts
pulse measurement data on the manual operation, switching
instructions, and mixing ratio instruction signals of the signals
that are input from the manual operation signal receiver 6 to the
aforementioned servo pulse mixing/switching unit into numerical
data and outputs the results to the aforementioned autonomous
control unit (in the figure, numerical data of manual operation
signals. (rudders). The pulse-processing computational CPU71 of the
aforementioned servo pulse mixing/switching unit 7 constantly
measures manual operation, switching instructions, and mixing ratio
instruction signals.
[0091] The servo pulse mixing/switching unit is provided with a
mechanism that outputs these measured data as numerical data to the
aforementioned autonomous control unit through RS-232C serial
communications, which are a general-purpose interface. The data
that can be output in the form of numerical data is by no means
limited to the types of data mentioned above; any input signals and
output signals to and from the aforementioned servo pulse
mixing/switching unit 7 can be output. The aforementioned
autonomous control unit treats this data in a manner similar to
handling data from other sensors. This function permits the
recording and storage of the aforementioned manual operation
signals similar to other sensor data, thereby allowing the
implementation of safe, system characterization experiments using
correction rudders for manual operation, and system
characterization based in the input/output data that is obtained
from system characterization experiments.
[0092] In addition, in this present invention, we devised a
function capable of providing target values from the manual
operation signal transmitter 8 to the aforementioned autonomous
control algorithm implemented in the aforementioned primary
computer of the aforementioned autonomous control unit, and this
function was implemented in the aforementioned primary computer.
This is described with reference to FIG. 17. Using the function,
incorporated in the aforementioned servo pulse mixing/switching
unit 7, that outputs manual operation signals as numerical
measurement data to the aforementioned autonomous control unit,
target values are generated by multiplying the manual operation
signals by a constant of proportionality, and in this manner, the
autonomous control of the aforementioned small unmanned helicopter
was achieved. It should be noted that the aforementioned constant
of proportionality need not be a fixed number; it can be any
quantity that associates manual operation signals with target
values. In this manner, it is possible to use the manual operation
signal transmitter 8 as a target value signal input unit for the
autonomous control algorithm. Using the manual operation signal
transmitter 8, the operator can intuitively provide target values,
such as the direction of motion and velocity, to the aforementioned
small unmanned helicopter, and can accomplish given objectives by
safely maneuvering the helicopter as if manually operated. In this
method, even though the operator may be under the illusion of
performing manual operations, autonomous control signals that are
provided to the aforementioned servo motors 3 are actually computed
by the autonomous control algorithm. The operation of
the<autonomous control algorithm>.fwdarw.<autonomous
control signal>.fwdarw.<servo pulse mixing/switching unit
7>.fwdarw.<servo motor>.fwdarw.<small unmanned
helicopter 1>.fwdarw.<sensor data>.fwdarw.<autonomous
control algorithm>feedback loop ensures the safety of the
aforementioned small unmanned helicopter at all times, and in this
manner, extremely safe flying can be realized.
[0093] Following is a description of the results of research on
tri-axial attitude control for the body of the helicopter and
autonomous control algorithms for cruising speed/position
control.
[0094] (Tri-axial Attitude Control)
[0095] First, we explain tri-axial attitude control using the
control system for the small unmanned helicopter.
[0096] We define a coordinates system as in FIG. 4. The attitude
angles .theta., .phi., and .psi. represent the pitching angle, the
rolling angle, and the yawing angle, respectively. In this
coordinates system, the positive X direction is the forward
direction from the body, the positive Y direction is the direction
to the right of the body, and the positive Z direction is the
direction downward from the body.
[0097] (Modeling of Servo Motors)
[0098] Servo motors similar to those used in a small hobby-type
radio-controlled helicopter are used as actuators for the body of
the helicopter, wherein the input pulse width is equal to the
rotational angle of a servo motor. Parameters .zeta..sub.S and
.omega..sub.ns were determined by the partial space identification
method by assuming the characteristics of a servo motor as in Eq.
(1) using a transfer function and by entering M-series of signals
as pulse widths into the servo motors. 7 G s ( s ) = n s 2 s 2 + 2
??? s n s s + n s 2 ( 1 )
[0099] (Pitching Rolling Model)
[0100] The autonomous control system used in the present invention
includes sensor delay time and delay time in the wireless space.
Such delay time represents three times the sampling time.
Therefore, the transfer function representation from an elevator
servo (longitudinal direction instruction to the pitch axis
attitude angle .theta., as in Eq. (2), takes the form of the
following transfer function equation (3) from an aileron servo
(lateral direction) instruction to the roll axis attitude angle
.phi.: 8 G ( s ) = - Ls K n s 2 ( s 2 + 2 ??? s n s s + n s 2 ) ( T
s + 1 ) s ( 2 ) G ( s ) = - Ls K n s 2 ( s 2 + 2 ??? n s s + n s 2
) ( T s + 1 ) s ( 3 )
[0101] (Yawing Model)
[0102] The system incorporates a yaw axis speed stabilization rate
gyro unit similar to that used in a small hobby-type
radio-controlled helicopter. The unit performs controls by treating
the input data as a yaw axis rotational angle speed. The helicopter
body used in the present mode of embodiment also incorporates an
angular velocity servo controller that uses an angular velocity
gyro sensor. This sensor is assumed to be a second-order delay
system. Therefore, the yaw axis rotational motion model takes the
form of a system that includes delay time, a second-order delay
system, and one integrator, as shown in Eq. (4): 9 G ( s ) = - Ls K
n s 2 ( s 2 + 2 ??? s n s s + n s 2 ) s ( 4 )
[0103] where the model gains (K.sub..phi., K.sub..theta.,
K.sub..psi.) and the time constants (T.sub..phi., T.sub..theta.)
are adjusted and determined by comparing experimental and
simulation data so that the two sets of numerical data will
agree.
[0104] In the present mode of embodiment, the LQG optimal control
theory is applied to the above three mathematical models to design
an autonomous control algorithm. In addition, a first-order servo
system was constructed to eliminate steady-state deviations. An
optimal feedback gain is determined by assuming that the pitching
angle .theta., the rolling angle .phi., and the yawing angle .psi.
are either single-input, single-output (SISO) systems or uncoupled
systems, respectively. FIG. 8 shows experimental results that were
produced by the controller thus obtained.
[0105] In this section, we explain translational motion controls
using the control system for a small unmanned helicopter.
[0106] (Longitudinal/Lateral Motion Model)
[0107] From a simple dynamical analysis, the following equation on
the lateral speed Y of the body can be obtained: 10 Vy = g 1 s ( 5
)
[0108] where g denotes the acceleration due to gravity; and .phi.,
the rolling attitude angle. The derivation of Eq. (5) is based on
the assumption that the helicopter body is at a fixed altitude and
that .phi.<<1. The experimental data shown in FIG. 9 suggests
the existence of some motion properties between the attitude angle
of the body and the acceleration. By approximating these properties
in terms of a first-order delay and by comparing experimental
results with simulations, we added one instability pole to Eq. (5),
and used the following transfer function representation
mathematical model in the final design of the control system: 11 V
y = g T s + T a s - a ( 6 )
[0109] A similar mathematical model was also used for the
longitudinal speed of the helicopter body: 12 Vx = g T s + T a s -
a ( - ) ( 7 )
[0110] where .THETA. denotes the pitch attitude angle of the
body.
[0111] (Vertical Motion Model)
[0112] The helicopter performs vertical motions by varying the
blade corrective pitch, thus varying the rotor lift. According to
blade wing element theory, the lift due to a rotor can be
represented as follows: 13 T = b 4 a 2 R 3 ( t + t ) c ( 8 )
[0113] where b denotes the number of rotor blades; .rho., the
density of air; a, the slope of the two-dimensional lift; .OMEGA.,
the rotor rpm; R, the radius of the rotor blade; .theta..sub.t the
corrective pitch; .phi..sub.t, the inflow angle; and c, the chord
length. Assuming that all of these variables with the exception of
.theta..sub.t are constants, the following transfer function
representation mathematical model for the velocity in the Z
direction can be formulated: 14 Z = k s t ( 9 )
[0114] (X-Y Direction Autonomous Control Algorithms)
[0115] For the models represented by Eqs. (6) and (7), we designed
independent velocity control algorithms for the X, Y, and Z
directions based on LQI control theory. FIG. 11 shows an overall
image of the X and Y position control loops. The velocity control
algorithms for the X and Y directions are computational algorithms
that calculate the attitude angle of the body to yield the required
vehicle speeds when certain, respective, target speeds for the
vehicle are given.
[0116] To move the body to an arbitrary target position, the
respective target velocities are calculated according to the
following equations:
V.sub.xref=.alpha.(P.sub.xref-P.sub.x) (10)
V.sub.yref=.alpha.(P.sub.yref-P.sub.y) (11)
[0117] where Vxref and Vyref denote target velocities in the X and
Y directions, respectively; Pxref and Pyref denote target positions
in the X and Y directions, respectively; Px and Pydenote the X- and
Y-coordinates of the body, respectively; and .alpha. is an
arbitrary constant.
[0118] The control loop has a structure in which the attitude
control ler, the velocity controller, and the position controller
are arranged serially. Compared with a single controller, this
structure has the following advantages: (1) the ability to limit
the attitude angle within a safe range; (2) an improved position
control overshooting through the application of a velocity limiter;
and (3) a controller internal state that is not dependent on
positional coordinates.
[0119] The third advantage avoids the use of a complex algorithm
for coordinate transformations when the yawing angle .psi. is
varied in an arbitrary coordinate system.
[0120] In view of the fact that the position and velocity for each
axis can be observed by means of high-precision RTK-DGPS, one state
quantity in the 3D model shown in Eqs. (6) and (7) is estimated by
means of a minimum-dimension observer. Because the dynamics for the
orientation servo systems are assumed to be sufficiently faster
than the translational motion, their properties are not taken into
considerations in the design of the control system.
[0121] (Z-direction Autonomous Control Algorithm)
[0122] The velocity control algorithm for the Z direction was
designed by comparing experimental results with simulation results,
by adjusting and determining the value of k in Eq. (9) so that the
two sets of numerical data agree, and by using the resulting value
and applying LQI control theory. The velocity control algorithm
with respect to the Z direction is a computational algorithm that
calculates the corrective pitch necessary to implement the required
speed of the vehicle when a target speed value in the Z direction
is given.
[0123] To move the body to an arbitrary target position, the target
velocity in the Z direction is calculated according to the
following equation:
V.sub.zref=.beta.(P.sub.zref-P.sub.z) (12)
[0124] where Vzref denotes a target velocity the Z direction;
Pzref, a target position value in the Z direction ; Pz the
Z-coordinate of the vehicle; and .beta., an arbitrary constant.
[0125] FIG. 12 shows the reference trajectory following control
results, and FIG. 13 shows the experimental results of the hovering
control. FIG. 14 shows the lateral and longitudinal velocity
control results and FIG. 15 shows the altitude control results.
Following is a description of a mode of embodiment of the
autonomous control algorithm based on the aforementioned servo
pulse mixing/switching unit, the aforementioned radio-controlled
pulse generator unit, and the aforementioned mathematical models,
such that the autonomous control algorithm is implemented on the
aforementioned small unmanned helicopter. The configuration of the
system can be divided broadly into a mobile station, wherein the
aforementioned autonomous control system and the aforementioned
servo pulse mixing/switching unit are installed on the
aforementioned small unmanned helicopter; and a ground station
wherein the state of autonomous control is monitored and target
values are input. Installed on the mobile station are a helicopter
body 1; sensors 2 that detect the current position and the attitude
angle of the helicopter body 1; servo motors 3 that operate the
five rudders for the helicopter body 1; a CPU4 that independently
calculates control reference values on optimal motion and direction
for each of the servo motors 3 by using the aforementioned
autonomous control algorithm, from the current flight state of the
helicopter obtained from the sensor 2, and the target values that
are set by the ground station; a wireless modem 5 that communicates
with the ground station; a radio-controlled receiver 6 that
receives manual operation signals from the radio-controlled
transmitter 8; and a servo pulse mixing/switching unit 7. The
aforementioned autonomous control system is built upon the sensor 2
and the CPU 4. In addition to its computation function, the CPU 4
is also endowed with the function of exchanging signals with the
wireless modem 5 to permit monitoring of the sensor information
obtained from the sensor 2 on the ground station and entering
target values that are established by the ground station. Included
in the sensor 2 are the GPS (not shown in the figure) that detects
the position of the helicopter body 1; a tri-axial orientation
sensor (not shown in the figure) that detects the orientation
states of the three axes; a ground altimeter (not shown in the
figure) that determines the altitude of the helicopter body; and a
magnetic azimuth meter (not shown in the figure) that measures the
azimuth. The servo pulse mixing/switching unit is a unit that can
switch between manual operation signals and autonomous control
signals, and can mix manual operation signals and autonomous
control signals in any proportion. For example, if the autonomous
control system for the helicopter fails during flight for some
reason or the CPU 4 fails, disabling the autonomous control of the
helicopter body, the aforementioned servo pulse mixing/switching
unit will automatically switch to the manual operation mode, thus
preventing the helicopter from crashing. In addition, the provision
of the aforementioned servo pulse mixing/switching unit 7 permits
the use of the autonomously controlled aforementioned small
unmanned helicopter for training in the use of a radio-controlled
helicopter. When the operator is not proficient in the operation of
a radio-controlled helicopter, the ratio between autonomous control
and manual control can be set so that it is heavily skewed in favor
of autonomous control, such as 9:1 and 8:2, so that even if the
operator maneuvers the helicopter unskillfully, the autonomous
control signals transmitted by the CPU 4 will perform recovery
operations to prevent crashing. As the operator gains familiarity
with the operation of the radio-controlled helicopter, the ratio
can be changed in favor of manual control, thereby improving the
operator's skill in performing manual operations on the
radio-controlled helicopter.
[0126] Provided on the ground station are a manual operation
transmitter 8 that enables the operator to perform manual
operations; a target value input unit 91 for the input of position
or velocity target values; a CPU9 equipped with a monitoring unit
92 that monitors the state of the helicopter body 1; and a wireless
modem 10 for communication with the mobile station. Also provided
is a pulse generator unit 11 that generates control signals.
[0127] Following is a description of the operation of the system.
The operator enters position or velocity target values from the CPU
9 of the ground station. The target values, through the wireless
modems 11 and 5, are entered into the CPU 4 that performs
calculations. Based on the target values that are entered and the
current flight status of the helicopter body 1 obtained from the
sensors 2, the CPU 4 performs computations of the autonomous
control algorithms that are designed based on aforementioned
mathematical models (2), (3), (4), (6), (7), and (9). Based on the
results of these computations, five types of control instructions
involving optimal motion and direction for each of the servo motors
3 are determined. If full autonomous control is on, the servo pulse
mixing/switching unit 7, not under the influence of manual
operation signals, controls each of the servo motors 3 based on the
controls signals having computed control reference values, thus
achieving the fully autonomous control of the motions of the
rudders for the helicopter body 1 according to target values. If
manual operation signals are to be mixed by the servo pulse
mixing/switching unit 7, control signals, mixed according to a set
proportion, are transmitted to the servo motors 3.
[0128] As described above, according to the autonomous control
system for the small unmanned helicopter based on this mode of
embodiment, the implementation and installation of the autonomous
control algorithms designed based on the above-described
mathematical models (2), (3), (4), (6), (7), and (9), as well as
the CPU 4, the sensors 2, and the servo motors 3, on a hobby
helicopter body permit the calculation of control reference values
that specify the optimal motion and direction for the respective,
corresponding servo motors 3 from the current flight state obtained
from the sensors 2 and from given position and velocity target
values, by using the aforementioned autonomous control algorithms,
thus achieving complete control of the helicopter body according to
target values.
[0129] It should be noted that, as another mode of embodiment, the
autonomous control of the aforementioned small unmanned helicopter
can be similarly achieved by installing a computer similar in
computational capabilities to the CPU 4, on the ground station.
However, in this case, the feedback control loop that is formed
would contain two wireless sections in the wireless modem and in
the manual operation transmitter/receiver. In such a case, if
wireless communications break down, the logical structure of the
control system will collapse, thus posing a risk of instability of
the flight of the aforementioned small unmanned helicopter. From a
flight safety standpoint, it is not desirable to implement all of
the aforementioned autonomous control algorithms on a host computer
installed on the ground station. In such a case, the CPU 4 and the
aforementioned ground station host computer can be used in
combination for control computation purposes by combining the
aforementioned servo pulse mixing/switching unit and the
aforementioned radio control pulse generator unit. Many widely
different embodiments of the present invention may be constructed
without departing from the spirit and scope of the present
invention.It should be understood that the present invention is not
limited to the specific embodiments described in the specification,
except as defined in the appended claims
* * * * *