U.S. patent application number 14/499203 was filed with the patent office on 2016-03-31 for distributed torque generation system and method of control.
The applicant listed for this patent is Dean Drako. Invention is credited to Dean Drako.
Application Number | 20160090005 14/499203 |
Document ID | / |
Family ID | 54016558 |
Filed Date | 2016-03-31 |
United States Patent
Application |
20160090005 |
Kind Code |
A1 |
Drako; Dean |
March 31, 2016 |
Distributed Torque Generation System and Method of Control
Abstract
An apparatus for an electrically powered terrestrial vehicle
applies electrical energy to front wheels and to rear wheels. A
control system receives desired acceleration inputs and provides
target torque requirements to a plurality of adaptive
field-oriented motor control circuits. One or more three-phase
alternating current synchronous motors receive voltage magnitude
and voltage frequency to generate torque, which is applied through
a reduction gear. The reduction gear may be coupled to one wheel or
a pair of wheels. Forward acceleration is favored over deceleration
by a chosen ratio between reduction gearing of the front axle
versus reduction gearing of the rear axle.
Inventors: |
Drako; Dean; (Austin,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Drako; Dean |
Austin |
TX |
US |
|
|
Family ID: |
54016558 |
Appl. No.: |
14/499203 |
Filed: |
September 28, 2014 |
Current U.S.
Class: |
701/22 |
Current CPC
Class: |
B60W 2710/083 20130101;
Y02T 10/7005 20130101; B60W 2720/26 20130101; B60K 17/145 20130101;
B60L 15/2036 20130101; Y02T 10/7258 20130101; B60L 3/106 20130101;
B60L 2240/423 20130101; Y02T 10/646 20130101; B60W 50/085 20130101;
Y02T 10/70 20130101; B60L 15/025 20130101; B60L 2240/427 20130101;
B60L 3/102 20130101; B60W 10/16 20130101; B60L 15/36 20130101; B60L
15/2045 20130101; B60W 2710/12 20130101; B60L 50/51 20190201; Y02T
10/72 20130101; Y02T 10/64 20130101 |
International
Class: |
B60L 15/20 20060101
B60L015/20; B60L 11/18 20060101 B60L011/18; B60K 17/14 20060101
B60K017/14; B60L 15/02 20060101 B60L015/02 |
Claims
1. A system comprising: a plurality of wheels, each wheel being one
of a front wheel and a rear wheel; a plurality of reduction gears,
each reduction gear being one of a front reduction gear and a rear
reduction gear; a plurality of alternating current electric motors
(AC motors), each motor mechanically coupled to at least one wheel
by at least one reduction gear; a plurality of adaptive
field-oriented motor control circuits (AF-OC), each AF-OC
electrically coupled to one or more AC motors to provide voltage
magnitude and voltage frequency and communicatively coupled to a
vehicle control unit (VCU) to receive digitally encoded signals
which specify voltage magnitude and voltage frequency; and the
vehicle control unit to budget torque among one of all wheels,
front wheels, and rear wheels according to indicia for desired
acceleration received from an operator.
2. The system of claim 1 wherein a pair of wheels are coupled to
one reduction gear coupled to one AC motor.
3. The system of claim 1 wherein each front wheel is coupled to one
front reduction gear coupled to one AC motor, and each rear wheel
is coupled to one rear reduction gear coupled to one AC motor.
4. The system of claim 1 wherein each AC motor is a 3-phase
electric motor.
5. The system of claim 1 wherein a front reduction gear has a first
reduction ratio and a rear reduction year has a second reduction
ratio.
6. The system of claim 5 wherein the first reduction ratio is
greater than the second reduction ratio.
7. The system of claim 5 wherein the first reduction ratio is less
than the second reduction ratio.
8. The system of claim 1 further comprising sensors to measure
wheel rotational speed (spin).
9. The system of claim 1 further comprising sensors to measure
wheel slip relative to a surface.
10. The system of claim 1 further comprising one or more generators
or stores of direct current electricity coupled to each AF-OC.
11. A method for optimizing energy efficiency and improving vehicle
performance executing instructions in a processor to receive
indicia for desired acceleration from an operator; receive
measurements of wheel slip and wheel spin; read stored values for
each reduction ratio and maximum slip, determine positive or
negative torque for each wheel; and, transmit digitally encoded
voltage maximum and voltage frequency to each AF-OC.
12. The method of claim 11 wherein more energy is provided to rear
wheels when accelerating forward.
13. The method of claim 11 wherein more energy is provided to front
wheels when not accelerating forward.
14. The method of claim 11 wherein the voltage maximum and voltage
frequency are limited to enable no more than A % slippage when
accelerating and -D % slippage when decelerating.
15. The method of claim 11 wherein all positive torque is provided
to rear wheels when forward acceleration is desired.
16. The method of claim 11 wherein all negative torque is provided
to front wheels when only deceleration is desired.
17. The method of claim 11 wherein all positive torque is provided
to front wheels when only air and road resistance needs to be
overcome.
18. An apparatus for controlling an adaptive field-oriented
electric motor comprising: a current speed determination circuit; a
desired acceleration determination circuit; a torque generation
distribution circuit; and a voltage magnitude and voltage frequency
determination circuit; whereby only front wheel adaptive
field-oriented motor control circuits receive voltage magnitude and
voltage frequency torque generation signals when a threshold speed
has been attained and no further acceleration is desired, and
whereby only rear wheel adaptive field oriented motor control
circuits receive voltage magnitude and voltage frequency torque
generation signals when acceleration is desired and a threshold
speed has not been exceeded.
19. The apparatus of claim 18 which controls only one wheel at any
forward or reverse speed below a threshold.
20. The apparatus of claim 18 which controls all four wheels on the
condition of inclement weather, poor road quality, or aggressive
cornering.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a non-provisional of Ser. No. 61/950,229
filed 10 Mar. 2014 "Adaptive Torque Budgeting and Electric Motor
Control System" which is incorporated by reference in its entirety
and receives the priority date thereof. Other related applications
are dockets R-PTNTR201411-15.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT
[0003] Not Applicable
INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISK
OR AS A TEXT FILE VIA THE OFFICE ELECTRONIC FILING SYSTEM
(EFS-WEB)
[0004] Not Applicable
STATEMENT REGARDING PRIOR DISCLOSURES BY THE INVENTOR OR A JOINT
INVENTOR
[0005] Not Applicable
BACKGROUND OF THE INVENTION
[0006] 1. Technical Field
[0007] The field of the invention is within motor vehicles, and
more specifically the control over distribution of torque
generation by a plurality of electric motors located throughout the
vehicle structure.
[0008] 2. Description of the Related Art
[0009] It is known that torque vectoring is provided to all wheel
drive vehicles. Torque vectoring is a known technology employed in
automobile differentials. A differential transfers engine torque to
the wheels. Torque vectoring technology provides the differential
with the ability to vary the power to each wheel. This method of
power transfer has recently become popular in all-wheel drive
vehicles. Some newer front-wheel drive vehicles also have a basic
torque vectoring differential. As technology in the automotive
industry improves, more vehicles are equipped with torque vectoring
differentials.
[0010] Differentials are known to refer to a particular type of
simple planetary gear train that has the property that the angular
velocity of its carrier is the average of the angular velocities of
its sun and annular gears. This is accomplished by packaging the
gear train so it has a fixed carrier train ratio R=-1, which means
the gears corresponding to the sun and annular gears are the same
size. This can be done by engaging the planet gears of two
identical and coaxial epicyclic gear trains to form a spur gear
differential. Another approach is to use bevel gears for the sun
and annular gears and a bevel gear as the planet, which is known as
a bevel gear differential.
[0011] The fundamental concept of torque vectoring depends on the
principles of a standard differential. A differential shares
available torque between wheels. This torque sharing ability
improves handling and traction. Torque vectoring differentials were
originally used in racing. The technology has slowly developed and
is now being implemented in a small variety of production vehicles.
The most common use of torque vectoring in automobiles today is in
all-wheel drive vehicles.
[0012] The main goal of torque vectoring is to vary a share of
torque between or among wheels coupled to a motor or engine.
Differentials generally consist of only mechanical components. A
torque vectoring differential often includes an electronic
monitoring system in addition to standard mechanical components.
This electronic aspect is only to direct the mechanical
differential when and how to share the torque.
[0013] Torque vectoring differentials on front or rear wheel drive
vehicles are less complex than all-wheel drive differentials. The
two wheel differential only shares torque between two wheels.
[0014] A front-wheel drive differential must take into account
several factors. It must monitor rotational and steering angle of
the wheels. As these factors vary during driving, different forces
are exerted on the wheels. The differential monitor these forces,
and adjusts torque accordingly. Many front-wheel drive
differentials can increase or decrease torque transmitted to a
certain wheel by changing the ratio between the two wheels. This
ability improves a vehicle's capability to maintain traction in
poor weather conditions. When one wheel begins to slip, the
differential can reduce the torque to that wheel, effectively
braking the wheel. The differential also increases torque to the
opposite wheel, helping balance the power output and keep the
vehicle stable. A rear-wheel drive torque vectoring differential
works the same way as a front-wheel drive differential, but doesn't
monitor the steering angle.
[0015] Most mechanical torque vectoring differentials are on
all-wheel drive vehicles. A first torque vectoring differential
varies torque between the front and rear wheels. This means that
under normal driving conditions, the front wheels receive a set
percentage of the engine torque, and the rear wheels receive the
rest. If needed, the differential can transfer more torque between
the front and rear wheels to improve vehicle performance.
[0016] For example, a vehicle might have a standard torque
distribution of 90% to the front wheels and 10% to the rear. Under
harsh conditions, the differential changes the distribution to
50/50. This new distribution spreads the torque more evenly between
all four wheels. Having more even torque distribution increases the
vehicle's traction.
[0017] There are more advanced torque vectoring differentials as
well. These differentials build on basic torque transfer between
front and rear wheels. They add the capability to share torque
between a pair of front wheels or a pair of rear wheels.
[0018] The differential monitors each wheel independently, and
distributes available torque to match current conditions. One known
mechanism first transfers power between front and rear pairs and
subsequently shares the amount of torque transmitted to each rear
wheel by a second differential in series. The front wheels,
however, do not receive different amounts of torque. Another known
torque vectoring system adds a third mechanical differential to
share torque provided to the front pair of wheels.
[0019] Another known system supports 4 electric motors coupled by
gearboxes and axles to individual wheels. Negative torque is
produced electrically rather than applying brakes as mechanical
systems do.
[0020] As is known, Mercedes Benz has provided a purpose built
electric vehicle with four synchronous independent electric motors.
The engines make a total of 740 (750 PS) and 1,000 Nm (737.5
lb-ft), which is split equally among the four wheels in normal
driving conditions. Because all four motors are
electrically-powered independently of one another translates into
potentially high speed wheel control.
[0021] The conventional Mercedes approach are still mechanically
linking each motor to its wheel by a reduction gearbox and axle. A
much more economical Tesla utilizes a single 3 phase AC induction
motor and has a conventional mechanical power train. A conventional
mechanical power train provides three differentials and reduction
gearboxes. A conventional power train must have the same reduction
ratio from engine to the front axis as well as to the rear axis to
enable all wheel drive.
[0022] It is known that torque vectoring is particularly suited to
electric vehicles. Lotus has been evaluating and developing new
systems and approaches. When a driver turns the steering wheel,
they expect the vehicle to change direction (yaw). The vehicle does
not, however, respond immediately because tires take time to build
up lateral forces, and the actual vehicle response may not be
exactly what is required, or expected.
[0023] Particularly at high vehicle speed, after an initial delay
period (a fraction of a second) the vehicle yaw rate can overshoot
and oscillate before settling on a steady value. At very high
speeds, or if the vehicle's suspension is poorly tuned or the
operator poorly skilled, the oscillations can increase and the
vehicle can go out of control. Even at lower speeds, the
oscillations can make the vehicle feel less stable and the driver
may need to make multiple steering adjustments to successfully
follow the intended path.
[0024] Conventional vehicle suspension is tuned through bump steer,
static settings, etc, to minimize the oscillations and to give a
stable response at all vehicle speeds and loading conditions, but
any increase in stability is at the expense of vehicle agility and
the vehicle response can become disappointing.
[0025] It is known that when a vehicle has independent control over
the drive and braking torques to each wheel (for instance, electric
hub motors), there is an opportunity to improve the vehicle yaw
response.
[0026] One approach has been by increasing the drive torque to a
pair of tandem wheels (e.g. port), and creating an effective
braking torque at the opposite pair of tandem wheels (e.g.
starboard). These drive torques are in addition (or subtracted
from) to the normal drive torques required to control vehicle
speed. In other words, turning or yaw occurs when one side of a car
is traveling faster than the other side.
[0027] Maximum Yaw Turning Moment (Torque)
[0028] Independent of the steered angle of the wheels, a yaw moment
is generated when the resultant vector of the tire forces is
perpendicular to a line through the center of gravity. The
resultant force is the vector sum of lateral force and
driving/braking force. The maximum yaw moment (if required) is
obtained when the resultant of the tire forces is perpendicular to
a line from the center of the tire to the vehicle center of
gravity.
[0029] There are two main advantages in using these resultant
forces to control vehicle yaw (as opposed to purely tire lateral
forces): [0030] a. The resultant force can act at a greater lever
arm, increasing the maximum moment available. [0031] b. Yaw rate
can be controlled without requiring any steering.
[0032] If the forces are correctly controlled, the vehicle can be
made to respond more quickly to a steering input and instability
can be reduced.
[0033] To do this, the control of the wheel torques needs to
consider: [0034] a. Increasing torque on the one side must be
balanced by a reduction on the other side to avoid unnecessary
acceleration. [0035] b. Vertical load on each wheel--particularly
as the vehicle corners, [0036] c. the vertical load on the inner
wheels reduce and drive/braking torque may cause wheel spin or
wheel lock-up. [0037] c. The addition of drive or braking torques
at the rear may result in loss of rear grip--leading to loss of
control. [0038] d. Any response must be safe and predictable.
[0039] Therefore, simply distributing the torque based on steering
wheel angle would achieve more yaw response (for the same steering
input), but it may not create any improvement in stability. It
could even make the vehicle behavior less predictable.
[0040] One known approach is yaw rate feedback. For any steer angle
and forward velocity, an ideal yaw rate can be calculated by
assuming no tire slip, and using the wheel geometry to approximate
the turn radius. The measured yaw rate is then used as feedback,
giving a yaw error. A differential term (yaw acceleration) is
included for damping. The output is used to control the
distribution of drive torque; i.e. for a left turn, an additional
torque is applied to the right, with an equal braking torque
applied to the left. These torques are in addition to the `normal`
drive torque that maintains the vehicle forward velocity.
[0041] A limitation to conventional feedback control is that the
system relies on measured yaw rate as an input signal. This
measured response data will also include `noise` (high frequency
waves created by road inputs and general vibration). In order to
use the signal, the signal must be filtered. This unfortunately
creates a time delay in the signal, and the feedback becomes too
late creating overshoot and oscillations in the response.
Electric Motor or Traction Drive Controls
[0042] Transmitting positive or negative values in Newton
meters.
[0043] It is known that Direct Torque Control provides used in
variable frequency drives to control the torque (and thus finally
the speed) of three-phase AC electric motors. This involves
calculating an estimate of the motor's magnetic flux and torque
based on the measured voltage and current of the motor.
[0044] See patents by Depenbrock, takahashi and Noguchi direct self
control and direct torque control.
[0045] U.S. Pat. No. 4,678,248 discloses a method for controlling a
rotating-field machine supplied from an inverter, the output
voltage system of the inverter being variable with respect to
amplitude, phase and frequency includes supplying amplitudes of
stator flux components formed from measured stator current
components and stator voltage components as actual value of a flux
control loop, and changing the phase and frequency of the inverter
output voltage system with a flux control as a function of a
predetermined stator flux reference value by directly setting-in
the switching state of the inverter and an apparatus for carrying
out the method.
[0046] It is known that Vector motor control or field-oriented
control provides control over three-phase AC electric motors by
adjusting the output current of a VFD inverter in Voltage magnitude
and Frequency. FOC is a control technique that is used in AC
synchronous and induction motor applications that was originally
developed for high-performance motor applications which can operate
smoothly over the full speed range, can generate full torque at
zero speed, and is capable of fast acceleration and deceleration
but that is becoming increasingly attractive for lower performance
applications as well due to FOC's motor size, cost and power
consumption reduction superiority. Not only is FOC very common in
induction motor control applications due to its traditional
superiority in high-performance applications, but the expectation
is that it will eventually nearly universally displace
single-variable scalar volts-per-Hertz (V/f) control.
[0047] What is needed is an improved apparatus and method to enable
dynamic wheel control for energy and torque budgeting for each
wheel.
BRIEF SUMMARY OF THE INVENTION
[0048] An apparatus for an electrically powered terrestrial vehicle
applies electrical energy to front wheels and to rear wheels. A
control system receives desired acceleration inputs and provides
target torque requirements to a plurality of adaptive
field-oriented motor control circuits. One or more three-phase
alternating current synchronous motors receive voltage magnitude
and voltage frequency to generate torque which is applied through a
reduction gear. The reduction gear may be coupled to one wheel or a
pair of wheels. Forward acceleration is favored over deceleration
by a chosen ratio between reduction gearing of the front axle
versus reduction gearing of the rear axle. An electrically powered
vehicle has diverse reduction gear ratios for front axle wheels and
rear axle wheels. Torque is budgeted to improve energy efficiency
when accelerating in favor of the axle with greater reduction
ratio. Torque is budgeted to improve energy efficiency when
cruising in favor of the axle with lesser reduction ratio.
[0049] A system for deep autonomous vehicle control allocates
positive and negative torque to each wheel. A sensor system,
navigation system, and control system generally control speed and
direction of a vehicle and the an adaptive torque control system
replaces conventional throttle and braking systems improves
performance and reduces reliance on the steering system for
skidding and slipping conditions due to dynamic traction and
loading.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0050] To further clarify the above and other advantages and
features of the present invention, a more particular description of
the invention will be rendered by reference to specific embodiments
thereof which are illustrated in the appended drawings. It is
appreciated that these drawings depict only typical embodiments of
the invention and are therefore not to be considered limiting of
its scope. The invention will be described and explained with
additional specificity and detail through the use of the
accompanying drawings in which:
[0051] FIG. 1 is a block diagram of a conventional processor used
for performing method steps in an apparatus;
[0052] FIG. 2 is a block diagram of an apparatus.
[0053] FIG. 3 is a flowchart of steps in a method performed by a
processor; and
[0054] FIG. 4 is a schematic of a system embodiment.
DETAILED DISCLOSURE OF EMBODIMENTS OF THE INVENTION
[0055] Reference will now be made to the drawings to describe
various aspects of exemplary embodiments of the invention. It
should be understood that the drawings are diagrammatic and
schematic representations of such exemplary embodiments and,
accordingly, are not limiting of the scope of the present
invention, nor are the drawings necessarily drawn to scale.
[0056] Referring now to FIG. 2, an embodiment of an apparatus for
controlling voltage magnitude and voltage frequencies at one or
more AC motors. A one wheel determination circuit 292 is coupled to
a data bus 270. A two wheel determination circuit 294 is coupled to
the data bus 270. A four wheel determination circuit 296 is coupled
to the data bus 270. Depending on the determination of the torque
generation distribution circuit 250, the addressable Adaptive
Field-Oriented Control circuits associated with each AC motor will
receive a digital indicia of voltage magnitude and voltage
frequency to be provided to their respective attached motors. The
determination of the torque generation distribution is based on
receiving a desired acceleration determination 210 from the
operator, and current speed determination 230 from sensors. The
current speeds may include the wheel spin, the while slip, and
other environmental conditions.
[0057] Referring now to FIG. 3, one embodiment of the present
invention is a method performed by a computer processor when
executing instructions stored in non-transitory computer readable
media, the method for operating the vehicle control unit is
described. At slowest speeds, only one wheel may need to be
powered. When accelerating from low speed, the wheels with the
maximum reduction gear may be optimally powered. When a threshold
of speed has been attained, the wheels with lower reduction gear
ratios may be optimally powered. Under certain conditions of
aggressive handling or poor conditions inferred from slip
measurements above a threshold, all four wheels may receive
separate voltage maximum and voltage frequency instructions. The
method comprises the steps receiving desired acceleration indicia
from the operator 310; receiving measurements of wheel slip and
wheel spin from sensors 320; reading stored data values for
reduction ratios of the front and rear wheels and the maximum allow
slip for retaining traction for the wheels 330; determining a
positive or negative desired torque for each wheel 340; and
transmitting a digital voltage maximum and voltage frequency 350 to
the respective control circuits.
[0058] Referring now to FIG. 4, a schematic is shown for an
exemplary system embodiment. A plurality of wheels are either front
wheels 411 412 or rear wheels 417 418. Each wheel is coupled to a
reduction gear which have a first reduction ratio 421 422 or a
second reduction ratio 427 428. Each reduction gear is powered by
an AC motor 431 431 437 438. The motors are provided with voltages
at magnitudes and frequencies controlled by Adaptive Field-Oriented
Control circuits 440 447 448. The illustration shows that in one
embodiment two wheels on one axle may receive the same torque or
each wheel may receive a unique torque. The voltage magnitude and
voltage frequencies for each wheel are determined and distributed
from a vehicle control unit 490.
[0059] One aspect of the invention is a 4 wheel power train for a
terrestrial vehicle comprising: a plurality of electric motors;
each electric motor coupled directly to a wheel, each electric
motor coupled to an Adaptive Torque Control or an Adaptive
Field-Oriented motor control circuit which receives a positive or
negative torque command from a vehicle control unit and provides
the electric motor with voltage magnitude and voltage frequency.
Advantageously, a vehicle control unit budgets to torque to two
forward wheels, two rear wheels, or among all four wheels according
to traction and desired acceleration.
[0060] In an embodiment the at least two electric motors are
coupled to the four wheels by at least two reduction gears, a first
of two reduction gears having a first reduction ratio of first
motor speed to first wheel speed; a second of two reduction gears
having a second reduction ratio of second motor speed to second
wheel speed; and at least one variable frequency drive control
circuit coupled to the plurality of electric motors.
[0061] In an embodiment, each of the front axle positioned wheels
are coupled to one of a pair of reduction gears coupled to one of a
pair of 3 phase AC electric motors which when the terrestrial
vehicle has been accelerated to a cruising speed receives current
having voltage magnitude and voltage frequency from the variable
frequency drive control circuit to overcome air drag and surface
resistance.
[0062] In an embodiment the first reduction gears have a lower
reduction ratio relative to the second reduction gears and are
coupled to the wheels positioned on the front axle of the
terrestrial vehicle.
[0063] In an embodiment, each of the rear axle positioned wheels
are coupled to one of a pair of reduction gears coupled to one of a
pair of 3 phase AC electric motors which when the terrestrial
vehicle is being accelerated toward a cruising speed receives
voltage magnitude and voltage frequency from the variable frequency
drive control circuit to overcome inertia, air drag and surface
resistance.
[0064] In an embodiment the second reduction gears have a higher
reduction ratio relative to the first reduction gears and are
coupled to the wheels positioned on the rear axle of the
terrestrial vehicle.
[0065] A method for optimizing electrical power consumption in a 4
wheel power train for a terrestrial vehicle by receiving
acceleration, wheel spin, and wheel speed data from sensors and
dynamically budgeting current between motors coupled the rear
wheels and motors coupled to the front wheels according to the
reduction ratio of the reduction gears when the terrestrial vehicle
is being accelerated to a threshold.
[0066] A circuit budgets stored electrical power to front wheels
and rear wheels of a vehicle according to reduction gear ratios and
according to vehicle speed and acceleration.
[0067] Non-limiting illustrations of the subject matter
include:
[0068] A system which includes: a plurality of wheels, each wheel
being one of a front wheel and a rear wheel; a plurality of
reduction gears, each reduction gear being one of a front reduction
gear and a rear reduction gear; a plurality of alternating current
electric motors (AC motors), each motor mechanically coupled to at
least one wheel by at least one reduction gear; a plurality of
adaptive field-oriented motor control circuits (AF-OC), each AF-OC
electrically coupled to one or more AC motors to provide voltage
magnitude and voltage frequency and communicatively coupled to a
vehicle control unit (VCU) to receive digitally encoded signals
which specify voltage magnitude and voltage frequency; and the
vehicle control unit to budget torque among all wheels, front
wheels, or rear wheels according to indicia for desired
acceleration received from an operator.
[0069] In an embodiment, a pair of wheels are coupled to one
reduction gear coupled to one AC motor.
[0070] In an embodiment, each front wheel is coupled to one front
reduction gear coupled to one AC motor, and each rear wheel is
coupled to one rear reduction gear coupled to one AC motor.
[0071] In an embodiment, each AC motor is a 3-phase electric
motor.
[0072] In an embodiment, a front reduction gear has a first
reduction ratio and a rear reduction year has a second reduction
ratio.
[0073] In an embodiment, the first reduction ratio is greater than
the second reduction ratio.
[0074] In an embodiment, the first reduction ratio is less than the
second reduction ratio.
[0075] In an embodiment, the apparatus further has sensors to
measure wheel rotational speed (spin).
[0076] In an embodiment, the apparatus also has sensors to measure
wheel slip relative to a surface. That is, the distance the wheel
travels is slightly more than or slightly less than its
circumferance.
[0077] In an embodiment, the apparatus further has one or more
generators or stores of direct current electricity coupled to each
AF-OC.
[0078] Another aspect of the invention is a computer-implemented
method for optimizing energy efficiency and improving vehicle
performance by executing instructions in a processor to: receive
indicia for desired acceleration from an operator; receive
measurements of wheel slip and wheel spin; read stored values for
each reduction ratio and maximum slip, determine positive or
negative torque for each wheel; and, transmit digitally encoded
voltage maximum and voltage frequency to each AF-OC.
[0079] In an embodiment, more energy is provided to rear wheels
when accelerating forward.
[0080] In an embodiment, more energy is provided to front wheels
when not accelerating forward.
[0081] In an embodiment, the voltage maximum and voltage frequency
are limited to enable no more than A % slippage when accelerating
and--D % slippage when decelerating.
[0082] In an embodiment, all positive torque is provided to rear
wheels when forward acceleration is desired.
[0083] In an embodiment, all negative torque is provided to front
wheels when only deceleration is desired.
[0084] In an embodiment, all positive torque is provided to front
wheels when only air and road resistance needs to be overcome.
[0085] Another aspect of the invention is an apparatus for
controlling an adaptive field-oriented electric motor which
includes: a current speed determination circuit; a desired
acceleration determination circuit; a torque generation
distribution circuit; and a voltage magnitude and voltage frequency
determination circuit; whereby only front wheel adaptive
field-oriented motor control circuits receive voltage magnitude and
voltage frequency torque generation signals when a threshold speed
has been attained and no further acceleration is desired, and
whereby only rear wheel adaptive field oriented motor control
circuits receive voltage magnitude and voltage frequency torque
generation signals when acceleration is desired and a threshold
speed has not been exceeded.
[0086] In an embodiment, the invention controls only one wheel at
any forward or reverse speed below a threshold.
[0087] In an embodiment, the invention controls all four wheels on
the condition of inclement weather, poor road quality, or
aggressive cornering.
[0088] Applicant also discloses another aspect of the invention as
an adaptive torque control or field-oriented control (AF-OC)
circuit to control three-phase AC motor output by providing current
or voltage magnitude and voltage frequency to single motor coupled
to a wheel, either directly or in an embodiment through a reduction
gear: the adaptive torque control or AF-OC circuit comprising: DC
power input circuits; AC power output circuits; at least one
microprocessor coupled to computer-readable non-transitory media;
and data signal interface circuits, wherein the AF-OC circuit
receives target torque commands, slip data, skid data, stability
data, accelerometer data, and transmits via a network interface
attainable torque; whereby adjustments to achieve target torque are
provided by changes in current, voltage magnitude, and frequency
rather than throttle control for positive torque and brake
application for negative torque and whereby amended torque requests
controlling current, voltage magnitude, and voltage frequency
outputs are controlled when slip data, skid data, or stability data
are received which cause the circuit to determine that a target
torque cannot be attained or sustained.
[0089] In an embodiment, the propulsion apparatuses each receive a
desired delta torque and control their own frequency, amplitude,
phase, voltage, current, etc as needed.
[0090] In an embodiment a motor controller receives the delta
torque values and supplies the propulsion apparatuses with current
or voltage at the necessary phase, frequency, amplitude, or complex
number.
[0091] In an embodiment, an adaptive torque control or AF-OC
circuit is communicatively coupled to a plurality of other adaptive
torque control or AF-OC circuits and to a torque budgeter circuit,
whereby target torque commands are generated for each AF-OC circuit
according to operator controls in combination with attainable
torque from each AF-OC, stability data, and accelerometer data.
[0092] In an embodiment, each adaptive torque control or AF-OC
circuit adjusts its torque by control over current, voltage
magnitude, and frequency magnitude output when any other AFOC
circuit determines a target torque cannot be attained or sustained,
or transmits substantially large slip data, skid data, or stability
data.
[0093] In an embodiment, a rear wheel AF-OC circuit adjusts its
voltage magnitude and frequency magnitude output when a front wheel
AFOC circuit determines a target torque cannot be attained or
sustained, or transmits substantially large slip data, skid data,
or stability data.
[0094] In an embodiment a torque budgeter circuit adjusts the
target torque for rear wheel AF-OC circuits when at least one front
wheel AFOC circuit determines a target torque cannot be attained or
sustained, or transmits substantially large slip data, skid data,
or stability data.
[0095] In a conventional system a central engine throttle and one
or more hydraulic brake pistons is engage to modify vehicle yaw
torque. Electrically controlled wheels offer more dynamic positive
and negative torque with far fewer mechanical linkages. Sensors
locally attached to each wheel can provide slip and skid
information directly to an adaptive field-oriented control (AF-OC)
circuit. Each AF-OC circuit determines what its attainable torque
can be for current conditions and transmits it to a torque
budgeting circuit. The torque budgeting circuit can readjust its
target torque commands in consideration of attainable torque for
each wheel, user operations (steering), and lateral acceleration
and stability data.
[0096] In an embodiment, sensors locally attached to each
electrically powered wheel provide slip and skid information
directly to an adaptive torque control or adaptive field-oriented
control (AF-OC) circuit. Each adaptive torque control or AF-OC
circuit determines what its attainable torque can be for current
conditions and transmits it to a torque budgeting circuit. In an
embodiment, the torque budgeting circuit readjusts all target
torque commands in consideration of attainable torque for each
wheel, user operations (steering), and lateral acceleration and
stability data.
[0097] There are multiple ways to determine slip angle--some can
use prediction based on RPM data from the wheel, some can use
external sensors for tire deflection etc. In an embodiment a
vehicle sensor measures land surface velocity and estimates RPM
equivalents for each wheel. In an embodiment, the estimated RPM is
compared by the torque control circuit with the actual RPM to
determine when slip exceeds a maximum slip target.
[0098] One aspect of the invention is a method operable by a
processor performing steps encoded as instructions on a
non-transitory media, to control distribution of electric energy to
at least one traction drive coupled to a wheel comprising: sensing
the steering direction and speed of the vehicle; on the condition
of speed below a threshold, distributing power to one or more
wheels associated with only one axle and if turning to only one
wheel of the only one axle; on the condition of speed above a
threshold and when not turning, distributing power to wheels
associated with only one axle; on the condition of aggressive
cornering applying yaw controlled power to budget torque among at
least four wheels; on the condition of inclement weather applying
yaw controlled power to budget torque among at least four wheels;
and on the condition of poor road conditions applying yaw
controlled power to budget torque among at least four wheels.
[0099] The network communicates inputs such as measured yaw,
vertical loading of each wheel, measured torque, wheel orientation,
wheel speed, and tire slip. In an embodiment, the network
distributes these inputs to each other wheel and to the yaw control
apparatus.
[0100] The network communicates a desired torque value or a delta
torque value for each traction drive and returns a confirmation or
error message from each motor control circuit. Each traction drive
may calculate parameters for its own motor configuration.
[0101] Drive parameters include a current, voltage, frequency, or
phase for each wheel calculated by the yaw control apparatus. The
drive parameters may be transmitted to each wheel if the wheel's
control circuit does not calculate from the desired torque. In
addition the network receives and distributes a yaw prediction for
future delta torques from a user interface such as a gps or map or
heads-up display or goggles.
[0102] A digital yaw control apparatus is communicatively coupled
to a user interface and to a network. The network connects at least
one control drive for each wheeled electric motor and provides a
digital torque packet to said control drive. The control drive
provides current or voltage to the wheeled motor. The control drive
modulates the amplitude of the current or voltage. The control
drive modulates the frequency or phase of the current or voltage.
The wheeled electric motor has a torque sensor and transmits the
resulting torque back to the digital yaw control apparatus. An
authentication circuit ensures that the correct wheeled motor
receives the digital torque packet and that the packet was
transmitted by the correct control drive.
[0103] In an embodiment, a digital signal processor, or hardware
discrete cosine transform (DCT) or software algorithm can filter
noise and high frequency clutter from a feedback loop.
[0104] In one embodiment for two wheel control, the invention
controls torque at a left and at a right rear wheels or at a left
and a right front wheel, which eliminates the needs for at least
one mechanical differential gear or any electronically controlled
differential. Depending on the steering angle, steering speed,
throttle pedal position, yaw velocity and vehicle speed, the
apparatus applying negative torque to the left or right wheel, as
required.
[0105] In one embodiment, this means that when entering a corner at
high speed, moderate negative torque values are transmitted to the
inside rear wheel. Simultaneously positive drive torque values
transmitted to the outside rear wheel supports the steering motion
of the car.
[0106] One aspect of the invention is a system including a
processor coupled to non-transitory computer readable media and
communicatively coupled to an operator interface and
communicatively coupled to one or more electrical powered
propulsion apparatuses.
[0107] The system determines a difference between desired vehicle
yaw and measured vehicle yaw to determine a value for delta torque
for each propulsion apparatus.
[0108] The system determines a value for positive or negative
desired torque for each of the one or more electrically powered
propulsion apparatuses and transmits the desired target torque to
each of the one or more electrically powered propulsion
apparatuses.
[0109] In embodiments, the system transmits a value as a digital
value; or in another embodiment as an amplitude; or in another
embodiment as a phase angle or as a frequency. In embodiments the
system determines and transmits the value as a complex number. In
an embodiment, the system further has at least one yaw sensor. In
an embodiment, the system further has at least one pitch sensor. In
an embodiment, the system further has at least one roll sensor. In
an embodiment, the system further has at least one acceleration
sensor.
[0110] In one embodiment of the invention, an electrically powered
propulsion apparatus has one or more wheels, one or more electric
motors, a motor controller and at least one sensor. The
electrically powered propulsion apparatus further includes a
surface sensor to report a vector of actual travel direction and
speed. In an embodiment the system also has an edge of pavement
sensor.
[0111] Applicant also discloses another aspect of the invention as
a method to control an apparatus by executing instructions and
parameters which control dynamic vehicle responsiveness and reflect
an operators personality are accessible by an application
programming interface (API). In an embodiment torque controlled
electric motors may attached to non-wheel traction mechanisms such
as fans, propellers, airscrews, caterpiller drives, paddles, and
powered legs.
[0112] DriveApps would be loaded either on the central computer
(VCU) or a separate user-provided computer that joins vehicle
CANbus
[0113] DriveApp architecture allows multiple apps. Examples
include:
1. Sports car
[0114] 2. A tow trailer
3. AWD ATV
4. AWD SUV
[0115] 5. multiple-motor water or ice/snow vessel 6. multiple-motor
aircraft 7. dual powered wheelchair or personal transporter
API:
[0116] All API calls are performed via sending a controller area
network (CAN) command into the traction CANbus. CAN ID defines
recipient of the command--each inverter also called an Adaptive
Field-Oriented Controller (AF-OC) circuit has a CAN ID, as does
Vehicle Control Unit (VCU) apparatus and Battery Management System
(BMS) circuit. All other subsystems are controlled from within
these modules (e.g., wheel #2 load actuator is controlled from
inverter #2 e.g. AF-OC-2, etc.)
1. Low-level (per-inverter) a. setTorque(wheel, torque,
duration_ms) i. requests torque output of <torque> N*m from
<wheel> wheel for <duration_ms> milli-seconds ii.
returns 0 on success, non-0 on error (error codes TBD) b.
setSlipLevel(wheel, level)--sets level of aggressiveness of slip
control (low=street car use, high=race track) c.
getTorque(wheel)--return torque value actually delivered d.
getLoad(wheel)--get wheel loading in Newtons e. getRPM(wheel)--get
RPM of the wheel f. getSlipAngle(wheel)--get actual sleep angle
[0117] Method of operation includes at a field oriented motor
controller coupled to a network, receiving a set torque command
which specifies a wheel identifier, a value of target torque, and a
duration wherein torque is in units of Newton*meters, and duration
is in units of milliseconds; receiving a set slip level as an
acceptable percentage of rotation; determining a voltage magnitude
and voltage frequency for a motor; providing 3 phase electric
current at said voltage magnitude and voltage frequency, receiving
slip and skid measurements from the identified wheel; and returning
success or error codes, which include the attainable torque at
acceptable slip.
[0118] Mid-level (traction system--level)
[0119] Rate of change in vehicle position in 3-dimensional polar
coordinates
[0120] getYawRate( )--get yaw rate in degrees/second from yaw
sensor
i. getRollRate( )--get roll rate in degrees/second from roll sensor
ii. getAttitudeRate( )--get attitude rate in degrees/second from
attitude sensor 1. getAccel( )--get vehicle acceleration in mm/s
2(1 g=9,800 units) 2. getLoad( )--get total vehicle weight
(dynamic, can be different from weight at rest due to aerodynamic
lift etc) 3. get[max/min][params]( )--get min and max values of the
parameters from the per-inverter level. Example:
[0121] int getMaxSlipAngle( )
4. setAccel(accel)--request acceleration of the vehicle in mm/s 2
(can be positive or negative)
[0122] A method for control of a vehicle by a processor performing
the steps of a process including transmitting commands and
receiving measured or stored data. In an embodiment, each sensor
responds when it is addressed. In an embodiment, all sensors having
the requested data respond in order when no address is specified in
the command. In embodiments the commands and resulting data
including at least one of the following: getYawRate--get yaw rate
in degrees/second from yaw sensor; getRollRate--get roll rate in
degrees/second from roll sensor; getAttitudeRate--get attitude rate
in degrees/second from attitude sensor; getAccel--get vehicle
acceleration in mm/s 2(1 g=9,800 units); getLoad--get total vehicle
weight (dynamic, can be different from weight at rest due to
aerodynamic lift etc); and get[max/min][params]( )--get min and max
values of the parameters SlipAngle, Torque, SlipLevel, RPM, and
Load.
[0123] In an embodiment, an operator control transmits to a vehicle
control unit a command to setAccel(accel)--request acceleration of
the vehicle in mm/s 2 (can be positive or negative). In an
embodiment, an autonomous vehicle control system is coupled by an
API to the vehicle control unit to request acceleration and
vectored torque.
[0124] High-level (car-level)
0. Battery Management System (BMS) functions
[0125] getMaxBattPower( )--get max battery power in kW. Used in VCU
(Vehicle Control Unit) to understand how much power is available to
distribute into wheels
i. getBattSOC( )--get state of charge of the battery in % ii.
getBattAH( )--get remaining energy in the battery in AH (amp-hours)
iii. getBattKWH( )--same in KWHrs iv. getBattV( )--get current
battery voltage--used by VCU to predict maximum possible power band
v. getBattIR( )--get current internal resistance of the
battery--used by VCU to predict maximum possible power band
[0126] A method for operating a vehicle by a processor in a vehicle
control unit coupled by a network to a battery management system
includes transmitting commands to read parameters including at
least one of the following: to get maximum battery power in kW:
getMaxBattPower; to get state of charge of the battery in percent:
getBattSOC; to get remaining energy in the battery in ampere-hours:
getBattAH; to get remaining energy in the battery in kilowatthours:
getBattKWH: to get current battery voltage: getBattV; to get
current measured internal resistance of the battery: etBattIR.
[0127] Applicant also discloses another aspect of the invention as
a system for predictive torque budgeting which receives traction
estimates for impending road conditions. Traction measurements from
previously recorded measurements can be retrieved using global
positioning coordinates. Road geometry and incline is predicted
from a stored 3D map. Traction measurements may be received from
another vehicle in a peleton. Road conditions can be forecast from
forward looking sensors on the vehicle itself. Wheel slip and wheel
skid measured by a front wheel is transmitted to the adaptive
field-oriented motor control of the tandem rear wheel. Wheel
loading sensors and actuators provide direct feedback on attainable
torque.
[0128] In an embodiment, the system receives predicted yaw events
from a map, gps system, user goggles or heads up display.
[0129] Intelligent traction prediction engine--data sources: [0130]
maps (curve ahead, etc) and GPS waypoints. [0131] GPS waypoints and
prior experience on same route [0132] photo sensors before the
front wheel to predict surface traction (camera looking out 1 foot
ahead will give us 10 ms time at 60 mph to modulate front wheel)
[0133] traction information from the front wheel fed into torque
commands to the rear wheels (that will see the same part of
pavement in .about.100 ms at 60 mph) [0134] wheel loading sensors
& actuators (to actively manage instantaneous wheel
loading)
[0135] Results: Based on the traction prediction method, the
apparatus provides target torque requests. The results include
matching a rear wheel to its corresponding front wheel; placing
more energy on the rear axle wheels and less on the front axle
wheels for climbing, anticipating tighter cornering and providing
positive torque to a left side or providing negative torque to a
right side or vice versa or both. In some cases, negative torque is
provided to one rear wheel while positive torque is provided to the
diagonally opposite wheel. The system anticipates desired yaw
moments for the route and road conditions.
[0136] In an embodiment, a rear wheel AF-OC circuit adjusts its
voltage magnitude and frequency magnitude output when a front wheel
AFOC circuit determines a target torque cannot be attained or
sustained, or transmits substantially large slip data, skid data,
or stability data.
[0137] In an embodiment a torque budgeter circuit adjusts the
target torque for rear wheel AF-OC circuits when at least one front
wheel AFOC circuit determines a target torque cannot be attained or
sustained, or transmits substantially large slip data, skid data,
or stability data.
[0138] Applicant also discloses another aspect of the invention as
a method, which provides through an API, a process to adaptively
control thrust instead of throttle and brake operation. The vehicle
control unit receives acceleration requirements from the higher
level autonomous systems and determines positive or negative torque
for each electric motor driven wheel.
CONCLUSION
[0139] The claimed subject matter is easily distinguished from
conventional power train differentials by electrically reallocating
power from one set of reduction gears to another set of reduction
gears when the operator calls for improved forward acceleration to
overcome inertia. The effect is to dynamically exchange the
performance characteristics of the vehicle among front wheel drive,
rear wheel drive, and all wheel drive.
[0140] The techniques described herein can be implemented in
digital electronic circuitry, or in computer hardware, firmware,
software, or in combinations of them. The techniques can be
implemented as a computer program product, i.e., a computer program
tangibly embodied in an information carrier, e.g., in a
machine-readable storage device or in a propagated signal, for
execution by, or to control the operation of, data processing
apparatus, e.g., a programmable processor, a computer, or multiple
computers. A computer program can be written in any form of
programming language, including compiled or interpreted languages,
and it can be deployed in any form, including as a stand-alone
program or as a module, component, subroutine, or other unit
suitable for use in a computing environment. A computer program can
be deployed to be executed on one computer or on multiple computers
at one site or distributed across multiple sites and interconnected
by a communication network.
[0141] Method steps of the techniques described herein can be
performed by one or more programmable processors executing a
computer program to perform functions of the invention by operating
on input data and generating output. Method steps can also be
performed by, and apparatus of the invention can be implemented as,
special purpose logic circuitry, e.g., an FPGA (field programmable
gate array) or an ASIC (application-specific integrated circuit).
Modules can refer to portions of the computer program and/or the
processor/special circuitry that implements that functionality.
[0142] FIG. 1 illustrates an exemplary programmable processor
comprising a bus or communication channel 111 coupling main memory
104, static memory 106, mass storage memory 107, and a processor
circuit 112 for executing instructions, and in embodiments at least
one interface to couple a display device 121, a selection command
data input 123, and/or a wireless interface 125.
[0143] Processors suitable for the execution of a computer program
include, by way of example, both general and special purpose
microprocessors, and any one or more processors of any kind of
digital computer. Generally, a processor will receive instructions
and data from a read-only memory or a random access memory or both.
The essential elements of a computer are a processor for executing
instructions and one or more memory devices for storing
instructions and data. Generally, a computer will also include, or
be operatively coupled to receive data from or transfer data to, or
both, one or more mass storage devices for storing data, e.g.,
magnetic, magneto-optical disks, or optical disks.
Computer-readable storage media suitable for embodying computer
program instructions and data include all forms of non-volatile
memory, including by way of example semiconductor memory devices,
e.g., EPROM, EEPROM, and flash memory devices; magnetic disks,
e.g., internal hard disks or removable disks; magneto-optical
disks; and CD-ROM and DVD-ROM disks. The processor and the memory
can be supplemented by, or incorporated in special purpose logic
circuitry.
[0144] A number of embodiments of the invention have been
described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the invention. For example, other network topologies may
be used. Accordingly, other embodiments are within the scope of the
following claims.
* * * * *