U.S. patent application number 12/772791 was filed with the patent office on 2010-08-26 for user input for vehicle control.
This patent application is currently assigned to DEKA Products Limited Partnership. Invention is credited to Robert R. Ambrogi, John D. Heinzmann, Richard Kurt Heinzmann, David Herr, Dean L. Kamen, John B. Morrell.
Application Number | 20100217497 12/772791 |
Document ID | / |
Family ID | 22414659 |
Filed Date | 2010-08-26 |
United States Patent
Application |
20100217497 |
Kind Code |
A1 |
Kamen; Dean L. ; et
al. |
August 26, 2010 |
USER INPUT FOR VEHICLE CONTROL
Abstract
A user input for controlling acceleration of a vehicle. The user
input has a movable member capable of deflection by a user such
that a degree of deflection corresponds to a specified velocity
commanded by the user. The correspondence between the degree of
deflection and the specified velocity may include a plurality of
zones, each zone characterized by a distinct sensitivity that may
be capable of customization for a specific user. The user input may
also include a neutral position of the movable member, wherein a
substantially sudden motion of the movable member to the neutral
position causes a slewed slowing of the vehicle.
Inventors: |
Kamen; Dean L.; (Bedford,
NH) ; Ambrogi; Robert R.; (Manchester, NH) ;
Heinzmann; John D.; (Manchester, NH) ; Heinzmann;
Richard Kurt; (Francestown, NH) ; Herr; David;
(Golden, CO) ; Morrell; John B.; (Manchester,
NH) |
Correspondence
Address: |
MCCORMICK, PAULDING & HUBER LLP
185 ASYLUM ST., CITY PLACE II
HARTFORD
CT
06103
US
|
Assignee: |
DEKA Products Limited
Partnership
Manchester
NH
|
Family ID: |
22414659 |
Appl. No.: |
12/772791 |
Filed: |
May 3, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12102104 |
Apr 14, 2008 |
7708094 |
|
|
12772791 |
|
|
|
|
10947122 |
Sep 22, 2004 |
7357202 |
|
|
12102104 |
|
|
|
|
10166553 |
Jun 10, 2002 |
6799649 |
|
|
10947122 |
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|
09524931 |
Mar 14, 2000 |
6443250 |
|
|
10166553 |
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60124403 |
Mar 15, 1999 |
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Current U.S.
Class: |
701/70 |
Current CPC
Class: |
A61G 2203/14 20130101;
B62K 11/007 20161101; G05B 13/042 20130101; A61G 5/04 20130101;
G05G 9/047 20130101; A61G 5/061 20130101; G05G 2009/0474
20130101 |
Class at
Publication: |
701/70 |
International
Class: |
G06F 7/00 20060101
G06F007/00 |
Claims
1. A vehicle propelled by a motorized drive for transporting the
vehicle across a surface, the vehicle comprising: a user input for
controlling movement of the vehicle including a movable member
capable of deflection by a user such that a degree of deflection
corresponds to a specified velocity commanded by the user, the
correspondence between the degree of deflection and the specified
velocity having a plurality of zones, each zone characterized by a
distinct sensitivity; and a balance-maintaining controller for
maintaining balance of the vehicle on the basis of a servo loop
governing the motorized drive in accordance with user commands of a
specified velocity.
2. The vehicle according to claim 1, wherein the distinct
sensitivity of each zone is capable of customized specification by
the user.
3. The vehicle according to claim 1, wherein the distinct
sensitivity of each zone is capable of customized specification for
a specified user.
4. The vehicle according to claim 1, wherein the distinct
sensitivity characterizing each zone is acceleration.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of copending application
Ser. No. 12/102,104, filed Apr. 14, 2008, which is a continuation
application of copending application Ser. No. 10/947,122, filed
Sep. 22, 2004 and issued as U.S. Pat. No. 7,357,202 on Apr. 15,
2008, which is a divisional application of copending application
Ser. No. 10/166,553, filed Jun. 10, 2002 and issued as U.S. Pat.
No. 6,799,649 on Oct. 5, 2004, which claims priority from U.S.
application Ser. No. 09/524,931, filed Mar. 14, 2000 and issued as
U.S. Pat. No. 6,443,250 on Sep. 3, 2002, which, in turn, claimed
priority from U.S. Provisional Application Ser. No. 60/124,403,
filed Mar. 15, 1999, each of which applications is incorporated
herein by reference in its entirety.
TECHNICAL FIELD
[0002] The present invention pertains to methods for control of the
configuration and motion of a personal vehicle, equipped with one
or more wheels or other ground-contacting members, by a person
carried on the vehicle or by an assistant.
BACKGROUND OF THE INVENTION
[0003] Personal vehicles (those used by handicapped persons, for
example), may require stabilization in one or more of the fore-aft
or left-right planes, such as when no more than two wheels are in
ground contact at a time. Vehicles of this sort may be more
efficiently and safely operated employing control modes
supplementary to those described in the prior art. A personal
vehicle may be referred to in this description, interchangeably, as
a "transporter."
SUMMARY OF THE INVENTION
[0004] In accordance with a preferred embodiment of the invention,
there is provided a vehicle for transporting a payload over a
surface that may be irregular and may include stairs. The vehicle
has a support for supporting the payload and a ground contacting
element movable with respect to a local axis, where the local axis
can be moved with respect to some second axis that has a defined
relation with respect to the support. The vehicle also has a
motorized drive arrangement for permitting controllable motion of
the ground contacting element so as to operate in an operating
condition that is unstable with respect to tipping in at least a
fore-aft plane when the motorized drive arrangement is not powered.
The vehicle also has an input device for receiving an indication
from an assistant who is not disposed on the vehicle of a direction
of desired motion of the vehicle.
[0005] In accordance with other embodiments of the invention, the
input device for receiving an indication from an assistant may be a
handle coupled to the support, and the handle may be
extensible.
[0006] An input device may be provided for receiving an indication
from a user specifying a configuration of the vehicle, the
specified configuration including at least one of seat height,
vehicle lean, vehicle direction, and vehicle speed. The input
device may further include a user command device for receiving an
indication from the user of at least one of a desired movement and
a desired configuration of the assembly.
[0007] In accordance with further alternate embodiments of the
invention, the vehicle may also include an assistant-override for
disabling the user command device while the vehicle is controlled
by an assistant. The user command device may include a
joystick.
[0008] In accordance with another aspect of the invention, in
accordance with preferred embodiments, there is provided a method
for enabling a subject to ascend and descend stairs with assistance
by an assistant. The method has a first step of providing a device
having a support for supporting the subject, a ground contacting
element movable with respect to a local axis, the local axis being
movable with respect to a second axis having a defined relation
with respect to the support, and a motorized drive arrangement for
permitting controllable motion of the ground contacting element so
as to operate in an operating condition that is unstable with
respect to tipping in at least the fore-aft plane when the
motorized drive arrangement is inoperative. The method has
subsequent steps of maintaining wheel torque against each riser
successively and changing the relation of the local axis with
respect to the support so as to maintain the center of gravity of
the device and the subject between specified limits in forward and
rearward directions of rotation of the device.
[0009] In accordance with other embodiments of the present
invention, there is provided a user input for controlling
acceleration of a vehicle. The user input has a movable member
capable of deflection by a user such that a degree of deflection
corresponds to a specified velocity commanded by the user. The
correspondence between the degree of deflection and the specified
velocity may include a plurality of zones, each zone characterized
by a distinct sensitivity. The user input may also include a
neutral position of the movable member, wherein a substantially
sudden motion of the movable member to the neutral position causes
a slewed slowing of the vehicle. The specified velocity may have
fore-aft and lateral components.
[0010] In accordance with other alternate embodiments of the
invention, a user input may be provided having a movable member
capable of deflection by a user such that a degree of deflection
corresponds to a specified velocity commanded by the user, the
correspondence between the degree of deflection and the specified
velocity having a plurality of zones, each zone characterized by a
distinct sensitivity. The distinct sensitivity of each zone may be
capable of customized specification by the user or for the
user.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The invention will be more readily understood by reference
to the following description, taken with the accompanying drawings,
in which:
[0012] FIG. 1 is a side view of a prior art personal vehicle of the
type in which an embodiment of the invention may be advantageously
employed;
[0013] FIG. 2 is a diagram of typical components of a personal
vehicle of the type in which an embodiment of the invention may be
advantageously employed indicating the variables used in the
description of specific embodiments of the present invention;
[0014] FIG. 3a is a plot of commanded velocity of a vehicle as a
function of the displacement of a joystick or other user input,
showing a variable transmission input control in accordance with an
embodiment of the present invention;
[0015] FIG. 3b is a plot of commanded acceleration as a function of
time showing discontinuities corresponding to deadband regions;
[0016] FIG. 3c is a plot of the effective acceleration in response
to the commanded acceleration of FIG. 4b, in accordance with an
embodiment of the present invention;
[0017] FIG. 4 is a rear view of the personal transporter of FIG. 1
showing an extensible handle used in an assist mode of vehicle
control in accordance with an embodiment of the invention;
[0018] FIG. 5 is a side view of a personal transporter indicating
the use of an assist mode of vehicle control in accordance with an
embodiment of the invention;
[0019] FIGS. 6A-6D show successive steps in the sequence of
climbing stairs with the aid of a personal transporter operated in
an assist mode of vehicle control in accordance with an embodiment
of the invention;
[0020] FIG. 7 is a side view of a personal transporter employing an
individual cluster leg configuration in accordance with an
alternate embodiment of the present invention;
[0021] FIG. 8 illustrates the control strategy for a simplified
version of FIG. 1 to achieve balance using wheel torque; and
[0022] FIG. 9 is a block diagram showing generally the nature of
sensors, power and control with the embodiment of FIG. 1.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0023] Personal vehicles designed for enhanced maneuverability and
safety may include one or more clusters of wheels, with the cluster
and the wheels in each cluster capable of being motor-driven
independently of each other. Such vehicles are described in U.S.
Pat. Nos. 5,701,965, 5,971,091, 6,302,230, 6,311,794, and 6,553,271
and in copending U.S. patent application Ser. No. 09/325,976, all
of which patents and which application are incorporated herein by
reference.
[0024] Referring to FIG. 1, the personal vehicle, designated
generally by numeral 10, may be described in terms of two
fundamental structural components: a support 12 for carrying a
passenger 14 or other load, and a ground-contacting module 16 which
provides for transportation of support 12 across the ground, or,
equivalently, across any other surface. The vehicle further
includes a motorized drive arrangement 21 for driving the ground
contacting elements 18. The passenger or other load may be referred
to herein and in any appended claims as a "payload." As used in
this description and in any appended claims, the term "ground" will
be understood to encompass any surface upon which the vehicle is
supported.
[0025] A simplified control algorithm for achieving balance in the
embodiment of the invention according to FIG. 1 when the wheels are
active for locomotion is shown in the block diagram of FIG. 8. The
plant 61 is equivalent to the equations of motion of a system with
a ground contacting module driven by a single motor, before the
control loop is applied. T identifies the wheel torque. The
remaining portion of the figure is the control used to achieve
balance. The boxes 62 and 63 indicate differentiation. To achieve
dynamic control to insure stability of the system, and to keep the
system in the neighborhood of a reference point on the surface, the
wheel torque T in this embodiment is governed by the following
simplified control equation:
T=K.sub.1(.theta.+.theta..sub.0)+K.sub.2{dot over
(.theta.)}+K.sub.3(x+x.sub.0)+K.sub.4{dot over (x)} (Eqn. 4)
where:
[0026] T denotes a torque applied to a ground-contacting element
about its axis of rotation;
[0027] .theta. is a quantity corresponding to the lean of the
entire system about the ground contact, with .theta..sub.0
representing the magnitude of a system pitch offset, all as
discussed in detail below;
[0028] x identifies the fore-aft displacement along the surface
relative to a fiducial reference point, with x.sub.0 representing
the magnitude of a specified fiducial reference offset;
[0029] a dot over a character denotes a variable differentiated
with respect to time; and
[0030] a subscripted variable denotes a specified offset that may
be input into the system as described below; and
[0031] K.sub.1, K.sub.2, K.sub.3, and K.sub.4 are gain coefficients
that may be configured, either in design of the system or in
real-time, on the basis of a current operating mode and operating
conditions as well as preferences of a user. The gain coefficients
may be of a positive, negative, or zero magnitude, affecting
thereby the mode of operation of the vehicle, as discussed below.
The gains K.sub.1, K.sub.2, K.sub.3, and K.sub.4 are dependent upon
the physical parameters of the system and other effects such as
gravity. The simplified control algorithm of FIG. 8 maintains
balance and also proximity to the reference point on the surface in
the presence of disturbances such as changes to the system's center
of mass with respect to the reference point on the surface due to
body motion of the subject or contact with other persons or
objects.
[0032] In order to accommodate two wheels instead of the one-wheel
system illustrated for simplicity in FIG. 8, separate motors may be
provided for left and right wheels of the vehicle and the torque
desired from the left motor and the torque desired from the right
motor can be calculated separately.
[0033] In the block diagram of FIG. 9 it can be seen that a control
system 51 is used to control the motor drives and actuators of the
embodiment of FIG. 1 to achieve locomotion and balance. These
include motor drives 531 and 532 for left and right wheels
respectively. If clusters are present, actuators 541 and 542 for
left and right clusters respectively. The control system has data
inputs including user interface 561, pitch sensor 562 for sensing
fore-aft pitch, and wheel rotation sensors 563, and pitch rate
sensor 564. Pitch rate and pitch may be derived through the use of
gyroscopes or inclinometers, for example, alone or in
combination.
[0034] It should be noted that although many of the embodiments
described herein utilize separate motors individually controlled, a
common motor may be used for a number of functions, and the
separate control may be achieved by appropriate clutch or other
power transmission arrangement, such as a differential drive. The
term "motorized drive" as used in this description and the
following claims means any device that produces mechanical power
regardless of means, and therefore includes a motor that is
electric, hydraulic, pneumatic, or thermodynamic (the latter
including an internal combustion or an external combustion engine)
together with any appropriate arrangement for transmission of such
mechanical power; or a thrust-producing device such as a turbojet
engine or a motor-driven propeller.
[0035] Referring further to FIG. 1, the modes of operation
described herein apply to vehicles having one or more
ground-contacting elements 18, where each ground-contacting element
is movable about an axis 20 and where the axis corresponding to a
ground-contacting member can itself be moved. For example,
ground-contacting element 18 may be a wheel, as shown, in which
case axis 20 corresponds to an axle about which the wheel
rotates.
[0036] Motion of axes 20 of respective ground-contacting elements
is referred to in this description and in any appended claims as
"cluster motion." Wheels 18 may be movable in sets, with the moving
assembly referred to as a cluster 36. Cluster motion is defined
with respect to a second axis 22, otherwise referred to as a
"cluster joint." Additional driven degrees of freedom may be
provided, such as motion of the second axis about one or more
pivots which may, in turn, allow the height of seat 28 to be varied
with respect to the ground. Alternatively, seat height may be
varied by means of a telescoping post, or by means of any other
mechanical artifice. Pivot 26 (shown in FIG. 2) may also be
referred to herein as a "knee joint." An actuator (not shown) may
be associated with each driven degree of freedom and controlled
using control strategies discussed in detail below. In preferred
embodiments of the invention, the actuators include wheel
servo-motors and cluster servo-motors, with current supplied to the
respective motors by servo amplifiers. Additionally, non-driven
wheels may be provided, such as casters 30 coupled to footrest 32
or otherwise to support 12.
[0037] For purposes of the following description, variables
describing the orientation and configuration of personal vehicle 10
are shown schematically in FIG. 2. It is to be understood that the
configuration of FIG. 2 is shown by way of example and not by way
of limitation. The configuration of FIG. 2 includes an additional
linkage 34 between the second axis 22 and support 12, where linkage
34 may also be referred to herein as a "calf." As shown in FIG.
2,
[0038] frame_pitch is the angle, measured from the center of
gravity CG to the vertical axis, designated g. In balancing mode
(see below), frame_pitch is measured between the CG and the contact
point on the ground. In 4-wheeled modes, frame_pitch is typically
the angle of the CG with respect to cluster joint 22 and may be
derived from a measurement of theta_calf (see below) and knowledge
of the machine configuration.
[0039] theta_calf is the angle of calf 34 with respect to
gravity.
[0040] RelClusterPos is the position of cluster 36 relative to calf
34.
[0041] phiC is the angle of cluster 36 with respect to gravity,
which may be obtained by adding theta_calf to RelClusterPos.
[0042] Other variables may be derived for purposes of description
and control algorithms:
[0043] theta_ref.sub.-4_wheels is the angle of calf 34 with respect
to gravity that would place the estimated CG directly over cluster
joint 22. This angle changes when the seat height changes since
calf 34 may move in order to keep the CG over the cluster joint 22.
theta_balance is the balance angle, and equals the calf angle
(theta_calf) required to place the estimated CG over one wheel.
There may be two balance angles for some cluster orientations, such
as when four wheels are on the ground.
[0044] theta_des_user is the correction applied to the control loop
to accommodate a user-commanded change in CG or pitch.
[0045] RelClusterPos_dot is the velocity of the cluster relative to
the calf. Generally, "_dot" refers to the time-rate-of-change of a
variable, and "hat" refers to a filtered variable.
[0046] Input of user instructions, whether of a person being
conveyed by the personal vehicle or of an attendant, may be
provided by means of an input device 8 (shown in FIG. 1) such as a
joystick or other device for directional control, and buttons or
switches for other commands. User instructions inputted via the
input device may include commands with respect to both the motion
of the vehicle, such as its direction and speed, as well as
commands with respect to the configuration of the vehicle, the
operational mode, the height of the vehicle seat or the angle of
lean of the seat. In accordance with a preferred embodiment of the
invention, the input device may be joystick that may be mounted on
the vehicle, or may be detachable, as described in U.S. Pat. No.
6,405,816. Alternatively, the input device may be a force handle
providing for control of the vehicle by a person currently
dismounted from the vehicle, such as a person preparing to transfer
to the vehicle from an automobile, for example.
[0047] Joystick Processing
[0048] Preprocessing of commands provided by a user for control of
a vehicle by means of a control input device are now discussed with
reference to FIGS. 3a-3c. Such commands may be applicable in any of
various modes of operation of a mechanized vehicle. Description
with respect to a "joystick" is by way of example only, however
other input devices are within the scope of the present invention
as described herein and as claimed in any appended claims.
[0049] Referring to FIG. 3a, a commanded velocity 40 is plotted as
a function of displacement x as depicted along the horizontal axis
of plot 42. The control provided by a control input is well-defined
as long as each displacement of a member which may be varied by the
user is mapped to a unique commanded velocity. In fact, a more
general displacement-to-commanded velocity law may be provided in
which hysteresis is allowed and the correspondence of a commanded
velocity to displacement of the member depends on the past history
of the joystick displacement, x(t), where t is time. In accordance
with an embodiment of the present invention; the commanded velocity
may be implemented by the vehicle over time, with the acceleration
slewed within the confines of specified limits, as known to persons
skilled in the control arts. Such slewing advantageously eliminates
the need for tremor damping of the vehicle.
[0050] In accordance with the control law depicted in plot 42,
three regions of distinct linear mapping laws are shown. In regions
44 and 46, commanded velocity 40 varies as a more rapid function of
displacement of the joystick, or movable member, while in central
region 48, commanded velocity varies more slowly with joystick
displacement, thereby allowing improved control of the vehicle in
tighter environments. The joystick thereby exhibits an effectively
variable transmission ratio, with the ratio configurable by the
user, for example, for operating parameters customized for indoor
and outdoor operation. Similarly, all joystick modes described
herein may be separately customized for different operation in the
various control modes of a vehicle. The control law may be any
specified functional relationship within the scope of the present
invention.
[0051] Referring to FIG. 3b, in which commanded acceleration 50 is
shown for a typical time-sequence of joystick motion, regions 52
correspond to a deadband wherein joystick displacement occurs and
no joystick output is produced. In accordance with an embodiment of
the present invention, deadband region 52 is removed from the
joystick command so that smooth transitions out of the deadband
area are produced, as shown in FIG. 3c. Thus, for example, if the
deadband region is 20 units large, a requested joystick command of
30 units results in an acceleration equal to 10 units.
[0052] Displacement of the joystick may occur in both fore-aft (x)
and lateral (y) directions, resulting in corresponding components
of a commanded velocity and/or acceleration. In accordance with an
embodiment of the invention, commanded x and y components may be
coupled so as to limit the x component based on the current y
component, for example. Thus, velocity may be limited during sharp
turns.
[0053] In accordance with other embodiments of the invention, user
input displacements may be overridden, and commanded velocities
limited, via software of otherwise, on the basis of specified
vehicle parameters. Thus, for example, commanded velocity may be
limited on the basis of battery voltage, seat height, frame angle,
or other parameters. Similarly, the return of the joystick to a
neutral position may be programmed to result in a gradual braking
of the vehicle, whereas hard braking may be achieved by deflection
of the joystick backwards past the neutral position.
[0054] Remote Mode
[0055] A remote mode is used to facilitate the transfer of the user
to and from the vehicle. The vehicle is controlled, via a remote
control device, without the user being seated in the vehicle. In
accordance with preferred embodiments of the invention, the remote
device is the user control interface 8 itself, which may be
decoupled mechanically from the vehicle as described in detail in
copending U.S. application Ser. No. 09/325,463. Communication of
data between user control interface 8 and vehicle 10 may be via
extensible cable, for example. Alternatively, communication of data
may be via wireless electromagnetic waves, including radio or
infrared waves, for example. In a preferred embodiment of the
invention, the user command interface 8 is readily disconnected
from the armrest of the vehicle by means of an asymmetrical quick
disconnect mechanism.
[0056] A sensor may be used to verify that the user is not seated
in the vehicle. In remote mode, the controller resets the gain to a
very low value and resets the configuration parameters such as
maximum speed and acceleration to values lower than the default
values. The low gains allow the vehicle to be moved and positioned
with less force than would be required were the gains set to their
default values. The remote control device may additionally require
the activation of a failsafe device such as the depression of a
specified button, which may be disposed on the control device, in
order for the command to be accepted by the controller while in
remote mode.
[0057] Assisted Stair Mode
[0058] The stair mode allows a user to climb stairs independently,
as described in detail in copending U.S. Pat. No. 6,311,794, or
with the assistance of an able-bodied person. The ascent may be
controlled by the user leaning and/or pulling on a handrail, and
the user may specify the seat height and lean angle of the
supporting vehicle. Cluster rotation is controlled on the basis of
the position of the CG, whether governed by action of the user or
of an assistant.
[0059] In stair mode, the wheel control loop and cluster control
loop are substantially decoupled. The goal of the wheel loop is to
drive the wheels back against the stair risers without excessive
torque, keeping the transporter in position while preventing motor
or amplifier overheating. The goal of the cluster loop, in
accordance with this embodiment, is to keep the center of gravity
of the vehicle, including the user, between the front and rear
wheels at all times. An additional goal, subsidiary to that of
stabilization, is to reduce the force needed by the user to travel
up and down stairs.
[0060] The control law applied by both wheel and cluster controls
in stair mode uses a high-bandwidth control loop modified by lower
frequency inputs. This ensures that the controller remains stable
in the presence of various environmental disturbances.
Additionally, the dynamics of the wheels and clusters may be
decoupled, for control purposes, into a number of identifiable
configurations, and appropriate correction terms may be applied to
the control law within the scope of the invention, so as to
provided improved performance under various operating
conditions.
[0061] Operation of the cluster controller is now described with
reference to the stair climbing mode. The force required to perform
stair climbing is related to how close the user can put the overall
center of gravity of the transporter and user over the wheel that
is currently stationary or that leads to the desired direction of
travel. If the user can keep the CG over this wheel (either by
trunk lean or cluster deflection) then the requisite forces are
lower.
[0062] The act of climbing may be viewed as a gait with four
distinct dynamic phases: Initiation, Swing, Relaxation, and
Placement. During Initiation, stair climbing is initiated. At
first, the transporter has four wheels on the surface. As the
cluster starts to rotate, one pair of wheels leaves the surface,
defining Initiation.
[0063] Swing is the phase of stair climbing wherein the cluster
rotates through the first half of its trajectory, i.e., between the
stair tread and vertical position of the cluster, such that, on
ascending stairs, potential energy increases. It begins at
Initiation and ends when the cluster is vertical. Potential energy
decreased during Relaxation--between the point at which the cluster
is vertical and the point at which all four wheels again contact
the stairs. During Placement, four wheels are on the stairs, and
the frame of the transporter is being repositioned to begin another
step.
[0064] The basic cluster control law,
ClusterVoltage=K.sub.p*PitchError-K.sub.d*ClusterVelocity
[0065] is modified, in accordance with a preferred embodiment of
the stair climbing mode, to address the following issues: [0066] a.
The user CG needs to be held over the back wheel while the
transporter is ascending. [0067] b. Similarly, the user (or
assistant), on descent, needs to place the frame sufficiently in
the forward direction as to move the CG over the front wheel.
[0068] c. A single mode for both ascent and descent is preferred.
[0069] d. Friction compensation may be provided to reduce the
effect of stick-slip chatter in the cluster transmission.
[0070] The augmented control law, in accordance with a preferred
embodiment of the invention, is:
ClusterVoltage=K.sub.p*PitchError-K.sub.d*ClusterVelocity+K.sub.p1*RearE-
rror+K.sub.p1*FrontError,
[0071] where RearError and FrontError are zero when the CG is
between the front and rear angle limits, which are shown in FIG. 8.
RearError and FrontError become non-zero when the CG pitch angle
crosses either angle limit. The pitch gain, K.sub.p1, for the limit
errors is much larger than the ordinary pitch gain K.sub.p. Thus,
in effect, the spring which holds the frame upright becomes much
stiffer when one of the angle limits is crossed. This causes the
cluster to rotate. By moving the front and rear angle limits as a
function of cluster position, the placement of the CG may be
controlled. When the rear limit and the front limit come together,
then the cluster moves to a precise location based on the calf
angle. When the limit angles are further apart, the cluster becomes
more passive and the system is more dissipative.
[0072] With respect to the wheel controller in stair mode, the
wheel controller acts as a one-way clutch, or, alternatively, as an
electronic ratchet, with a dead band which prevents excessive
torque from being developed against successive stair risers.
[0073] In an assisted stair mode, a personal vehicle may be
controlled by an assistant who may apply external guiding signals,
thereby supplanting the role of input provided by a subject being
transported by the vehicle. The mode of operation has been
described with reference to the stair mode to which the assist mode
is identical, with lean input being provided by the assistant. In
assist mode, the gains used in the enhanced mode are reduced and
configuration parameters such as maximum speed and acceleration are
lowered. This allows the vehicle to be moved and positioned with
less force from the assistant or the rider. In addition, an assist
mode safety device (such as an electric switch) may be provided
such that the safety device must be activated by the assistant
before the mode may be entered. The safety device may be, for
example, a button 96 (shown in FIG. 4) disposed on the rear of the
seat backrest such that the assistant may easily press the button
and activate the mode, while making it difficult for the rider to
do the same. In another embodiment, the button may be placed on an
assistant seat handle.
[0074] An assistant may, for example, guide a person, seated in a
personal vehicle, up or down a flight of stairs. Referring now to
FIG. 4, the input of an assistant may be via mechanical guidance of
the vehicle, such as via extensible handle 90 coupled to support
12. Handle 90 is shown in a retracted position 92 and in extended
position 94 as designated by dashed lines. FIG. 5 shows a side view
of personal vehicle 10 after assistant 100 has raised extensible
handle 90 to a comfortable level, in preparation for ascending
steps 102.
[0075] The sequence of assisted stair ascension in accordance with
a preferred embodiment of the invention is now discussed with
reference to FIGS. 6A-6D. In FIG. 6A, assistant 100 is shown
applying rearward pressure to handle 90 in order to move the center
of gravity (CG) of vehicle 10, including subject 14, to a position
over or aft of point of contact 110 between rear wheel 112 and
surface 114 (which may be referred to herein and in any appended
claims as the "ground"). Referring now to FIG. 6B, vehicle 10
responds to the shift of the CG to a position above or aft of
contact point 110, vehicle by rotating cluster 36 in a direction
(clockwise in the figure) as to ascend step 102. FIG. 6C shows
assistant 100 applying a forward force on vehicle 10 via handle 90
so as to move the CG of the vehicle in a forward direction. FIG. 6D
shows wheel 116 in contact with step 102, whereupon the process may
be repeated for ascending subsequent steps.
[0076] Individual Cluster Legs
[0077] Referring now to FIG. 7, an alternate embodiment is shown of
a personal vehicle of a sort which may be controlled by the control
modes described herein. In accordance with this embodiment, wheels
120 and 122 are not jointly rotated about a cluster joint but may
instead be mounted on members 124 individually rotatable about one
or more axes at one or more pivots 126 which may be fixed with
respect to support 12. The functionalities described above, and in
the preceding transporter patent applications incorporated herein
by reference, with respect to cluster motion may be achieved,
alternatively, by a loop controlling the scissor action of wheel
support members 124.
[0078] The described embodiments of the invention are intended to
be merely exemplary and numerous variations and modifications will
be apparent to those skilled in the art. All such variations and
modifications are intended to be within the scope of the present
invention as defined in the appended claims.
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