PATENT DOCUMENT

Publication Number: US-11498561-B1
Application Number: US-201916378674-A
Country: US
Kind Code: B1

Title: Vehicle deceleration system

Abstract:
A vehicle includes a control system, a sensing system that senses an environment of the vehicle, and a propulsion system, a braking system, and a steering system that are operated by the control system to navigate the vehicle according to the sensing system and without direct human control. The propulsion system and the braking system are operated by the control system to cooperatively decelerate the vehicle. The braking system includes an inboard friction brake that is associated with one or more wheels of the vehicle and does not form unsprung mass of the vehicle.

Claims:
What is claimed is: 
     
       1. A vehicle comprising:
 a control system, a sensing system that senses an environment of the vehicle, and a propulsion system, a braking system, and a steering system that are operated by the control system to navigate the vehicle according to the sensing system and without direct human control; 
 wherein the propulsion system and the braking system are operated by the control system to cooperatively decelerate the vehicle, and the braking system includes an inboard friction brake that is associated with one or more wheels of the vehicle and that does not form unsprung mass of the vehicle. 
 
     
     
       2. The vehicle according to  claim 1 , wherein the control system limits operation of the vehicle according to a condition of the inboard friction brake, the condition including one or more of a temperature or a time from a high deceleration, and the vehicle being limited by one or more of preventing movement or limiting speed;
 wherein the vehicle further includes an active suspension system that includes actuators that are operated by the control system to move the wheels up and down relative to a body of the vehicle; and 
 wherein the wheels of the vehicle include front wheels and rear wheels, and the vehicle does not include outboard friction brakes that form unsprung mass at one or more of the front wheels or the rear wheels. 
 
     
     
       3. The vehicle according to  claim 1 , wherein the control system limits operation of the vehicle according to a condition of the inboard friction brake. 
     
     
       4. The vehicle according to  claim 3 , wherein the condition of the inboard friction brake includes one or more of a temperature of the inboard friction brake or a time from a high deceleration event using the inboard friction brake. 
     
     
       5. The vehicle according to  claim 4 , wherein the vehicle limits operation of the vehicle by one or more of preventing movement of the vehicle or limiting a speed of the vehicle. 
     
     
       6. The vehicle according to  claim 1 , wherein the vehicle further includes an active suspension system that controls movement of the wheels relative to a vehicle body of the vehicle. 
     
     
       7. The vehicle according to  claim 6 , wherein the active suspension system includes actuators that are operated by the control system to move the wheels up and down relative to the vehicle body. 
     
     
       8. The vehicle according to  claim 1 , wherein the wheels of the vehicle include front wheels and rear wheels, and the vehicle does not include outboard friction brakes that form unsprung mass at one or more of the front wheels or the rear wheels. 
     
     
       9. The vehicle according to  claim 8 , wherein the vehicle does not include outboard friction brakes at the rear wheels. 
     
     
       10. The vehicle according to  claim 1 , wherein the propulsion system includes a motor-generator and a gearbox having an output shaft that transfers torque to one of the wheels and an intermediate shaft that transfers torque between the motor-generator and the output shaft, and the inboard friction brake is coupled to one of the motor-generator, the output shaft, or the intermediate shaft. 
     
     
       11. The vehicle according to  claim 1 , wherein the inboard friction brake includes one of a momentum brake, a drum brake, or a rotor and a caliper. 
     
     
       12. The vehicle according to  claim 1 , wherein the braking system includes four of the inboard friction brakes, each of the inboard friction brakes being associated with one of four wheels of the vehicle. 
     
     
       13. A vehicle comprising:
 a body; 
 four wheels that include a first driven wheel and a second driven wheel; 
 a suspension system supporting the body on the four wheels; 
 a propulsion system having one or more motor-generators and one or more gearboxes, the first driven wheel and the second driven wheel being driven by one of the motor-generators via one of the gearboxes, a drive shaft, and a constant velocity joint; 
 a braking system having an inboard friction brake for decelerating one or more of the first driven wheel or the second driven wheel and being located inboard of the constant velocity joint associated therewith; and 
 a control system that cooperatively operates the propulsion system and the braking system to decelerate the vehicle. 
 
     
     
       14. The vehicle according to  claim 13 , wherein the vehicle includes a first motor-generator and a first gearbox that drive the first driven wheel, and a second motor-generator and a second gearbox that drive the second driven wheel. 
     
     
       15. The vehicle according to  claim 14 , wherein the first motor-generator and the second motor-generator each drive only one of the four wheels. 
     
     
       16. The vehicle according to  claim 14 , wherein the braking system includes a first inboard friction brake for decelerating the first driven wheel and a second inboard friction brake for decelerating the second driven wheel. 
     
     
       17. The vehicle according to  claim 16 , wherein the first inboard friction brake is one of coupled to the first motor-generator or positioned in the first gearbox, and the second inboard friction brake is one of coupled to the second motor-generator or positioned in the second gearbox. 
     
     
       18. The vehicle according to  claim 13 , wherein the vehicle includes a first motor-generator and a second motor-generator that are coupled to one gearbox by which the first driven wheel and the second driven wheel are separately driven by the first motor-generator and the second motor-generator, respectively. 
     
     
       19. The vehicle according to  claim 13 , wherein the control system operates the propulsion system and the braking system cooperatively to decelerate the vehicle without human control. 
     
     
       20. The vehicle according to  claim 13 , wherein one of the one or more motor-generators applies a first torque to the first driven wheel for decelerating the vehicle, and the inboard friction brake applies a second torque to the first driven wheel for decelerating the vehicle; and
 wherein in a low deceleration event, the control system operates the one motor-generator to apply the first torque and does not operate the inboard friction brake such that the second torque is zero, and in a high deceleration event, the control system operates the inboard friction brake for the second torque to be at a constant level and operates the one motor-generator for the first torque to supplement the second torque. 
 
     
     
       21. The vehicle according to  claim 13 , further comprising one or more supplemental motor-generators, wherein each of the supplemental motor-generators is associated with one of the motor-generators and selectively provides supplemental torque to assist decelerating the vehicle. 
     
     
       22. A vehicle comprising:
 a body; 
 four wheels that include a first driven wheel and a second driven wheel; 
 a suspension system supporting the body on the four wheels; 
 a propulsion system having a first motor-generator, a differential, and a torque vectoring system, wherein the first motor-generator provides a first torque to the differential for transfer to the first driven wheel and the second driven wheel, and the torque vectoring system includes a second motor-generator that provides a second torque to a torque vectoring gearbox for distribution between the first driven wheel and the second driven wheel during normal operation and provides the second torque to the differential to supplement the first torque during a high deceleration event. 
 
     
     
       23. The vehicle according to  claim 22 , further comprising a braking system having a first friction brake that applies a first braking torque to the first driven wheel and a second friction brake that applies a second braking torque to the second driven wheel. 
     
     
       24. The vehicle according to  claim 23 , wherein the first friction brake and the second friction brake are inboard brakes, and the differential and the torque vectoring gearbox are provided as a single gearbox that contains the inboard friction brakes. 
     
     
       25. The vehicle according to  claim 22 , further comprising a braking system having friction brakes, wherein the first driven wheel and the second driven wheel are rear wheels, and the four wheels include front wheels and the friction brakes apply braking torque to the front wheels. 
     
     
       26. The vehicle according to  claim 25 , wherein the friction brakes do not form unsprung mass of the vehicle. 
     
     
       27. The vehicle according to  claim 25 , wherein the braking system does not include friction brakes associated with the rear wheels.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62/654,704, filed Apr. 9, 2018, the entire disclosure of which is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to vehicles and, in particular, deceleration or braking systems thereof. 
     BACKGROUND 
     A human-operated vehicle is subject to conditions consequential to the human operator&#39;s limited ability to comprehend conditions external to the vehicle, comprehend capabilities of the vehicle within such conditions, and control the vehicle according to the external conditions and the vehicle capabilities. This means that human-operated vehicles are subject to extreme usage scenarios due to the human operator&#39;s imprecise control (e.g., hard braking, delayed responses, etc.) and, consequentially, include a limited number of human-operated inputs and are engineered to account for the extreme usage scenarios. For example, the human-operated vehicle is typically limited to three primary control inputs, which include an acceleration input (e.g., accelerator pedal for controlling output of a propulsion system of the vehicle and, thereby, acceleration and speed of the vehicle), a braking input (e.g., brake pedal for controlling output of a braking system of the vehicle and, thereby, deceleration and speed of the vehicle), and a steering input (e.g., steering wheel for changing direction of wheels of the vehicle and, thereby, changing direction of the vehicle). A braking system that is human-operated, for example, may be engineered to handle repeat emergency braking maneuvers in close succession, which may require use of certain materials and/or handling of excessive thermal loads. 
     Human-operated vehicles may include various automated controls, which operate in limited usage scenarios and are often to correct for limitations of human operation. For example, an antilock braking system may control brake application when wheel slip is detected (e.g., with hard braking by the user in slippery road conditions), or a lane keeping assist system may prevent a vehicle from drifting outside a lane of a public roadway (e.g., if the human operator fails to recognize the curvature of a road). 
     SUMMARY 
     In an implementation, a vehicle includes a control system, a sensing system that senses an environment of the vehicle, and a propulsion system, a braking system, and a steering system that are operated by the control system to navigate the vehicle according to the sensing system and without direct human control. The propulsion system and the braking system are operated by the control system to cooperatively decelerate the vehicle. The braking system includes an inboard friction brake that is associated with one or more wheels of the vehicle and does not form unsprung mass of the vehicle. 
     The control system limits operation of the vehicle according to a condition of the inboard friction brake, which may include one or more of a temperature or a time from a high deceleration. The control system may limit operation of the vehicle by one or more of preventing movement or limiting speed. The vehicle may further include an active suspension system that includes actuators that are operated by the control system to move the wheels up and down relative to a body of the vehicle. The wheels of the vehicle may include front wheels and rear wheels, and the vehicle may not include outboard friction brakes that form unsprung mass at one or more of the front wheels or the rear wheels. 
     In an implementation, a vehicle includes a body, four wheels, a suspension system, a propulsion system, and a braking system. The four wheels include a first driven wheel and a second driven wheel. The suspension system supports the body on the four wheels. The propulsion system includes one or more motor-generators and one or more gearboxes. The first driven wheel and the second driven wheel are driven by one of the motor-generators via one of the gearboxes, a drive shaft, and a constant velocity joint. The braking system includes an inboard friction brake for decelerating one or more of the first driven wheel or the second driven wheel, which is located inboard of the constant velocity joint associated therewith. The control system cooperatively operates the propulsion system and the braking system to decelerate the vehicle. 
     In an implementation, a deceleration system for a vehicle includes a motor-generator, a friction brake, and a control system. The motor-generator applies a first torque to a wheel for decelerating the vehicle. The wheel forms part of an unsprung mass of the vehicle. The friction brake applies a second torque to the wheel for decelerating the vehicle. The friction brake does not form part of the unsprung mass of the vehicle. The control system controls the first torque and the second torque. In a low deceleration event, the control system operates the motor-generator to apply the first torque and does not operate the friction brake such that the second torque is zero. In a high deceleration event, the control system operates the friction brake for the second torque to be at a constant level and operates the motor-generator for the first torque to supplement the second torque. 
     In an implementation, a vehicle includes a body, four wheels that include a first driven wheel and a second wheel, and a propulsion system having a first motor-generator, a differential and a torque vectoring system. The first motor-generator provides a first torque to the differential for transfer to the first driven wheel and the second driven wheel. The torque vectoring system includes a second motor-generator that provides a second torque to a torque vectoring gearbox for distribution between the first driven wheel and the second driven wheel during normal operation and provides the second torque to the differential to supplement the first torque during a high deceleration event. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not to-scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. 
         FIG. 1  is a schematic view of a vehicle according to an exemplary embodiment. 
         FIG. 2  is another schematic view of the vehicle of  FIG. 1 . 
         FIG. 3  is a plot of a wheel slip curve and wheel deceleration torque vs. time provided by embodiments of a propulsion system and a friction braking system of the vehicle of  FIG. 1 . 
         FIG. 4  is a plot of a wheel slip curve and wheel deceleration torque vs. time provided by further embodiments of a propulsion system and a friction braking system of the vehicle of  FIG. 1 . 
         FIG. 5  is a schematic view of a portion of the vehicle of  FIG. 1 . 
         FIG. 6  is a partial cross-sectional view of an embodiment of a propulsion system of the vehicle of  FIG. 1 . 
         FIG. 7  is a partial cross-sectional view of another embodiment of the propulsion system and an embodiment of a friction braking system of the vehicle of  FIG. 1 . 
         FIG. 8  is a partial cross-sectional view of another embodiment of the propulsion system and another embodiment of a friction braking system of the vehicle of  FIG. 1 . 
         FIG. 9  is a partial cross-sectional view of another embodiment of the propulsion system and another embodiment of a friction braking system of the vehicle of  FIG. 1 . 
         FIG. 10  is a partial cross-sectional view of another embodiment of the propulsion system and another embodiment of a friction braking system of the vehicle of  FIG. 1 . 
         FIG. 11  is a partial cross-sectional view of another embodiment of the propulsion system and another embodiment of a friction braking system of the vehicle of  FIG. 1 . 
         FIG. 12A  is a partial side view of a friction brake mechanism of any of the friction braking systems of  FIGS. 7-10 , which is in a first state. 
         FIG. 12B  is a partial side view of the friction brake mechanism of  FIG. 12A  in a second state. 
         FIG. 13A  is a front view of another friction brake mechanism of any of the friction braking systems of  FIGS. 7-10 . 
         FIG. 13B  is a side view of the friction brake mechanism of  FIG. 13A . 
         FIG. 13C  is a cross-sectional view of the friction brake mechanism taken along line  13 C- 13 C in  FIG. 13B . 
         FIG. 13D  is a cross-sectional view of the friction brake mechanism taken along line  13 D- 13 D in  FIG. 13B . 
         FIG. 13E  is s partial cross-sectional view of the friction brake mechanism taken along line  13 E- 13 E, which omits brake shoes of the friction brake mechanism. 
         FIG. 14A  is a partial cross-sectional view of another embodiment of the propulsion system and another embodiment of a friction braking system of the vehicle of  FIG. 1 , which is in a first state. 
         FIG. 14B  is a partial cross-sectional view of the propulsion system and the friction braking system of  FIG. 14A , which is in a second state. 
         FIG. 15A  is a schematic view of a deceleration system in a first state. 
         FIG. 15B  is a schematic view of the deceleration system of  FIG. 15A  in a second state. 
         FIG. 16  is a schematic view of a controller. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed herein are various embodiments of a vehicle  100  and functional subsystems thereof, which are autonomously controlled. With autonomous control, a user may, for example, specify a destination or route, while the various functional subsystems of the vehicle  100  are controlled autonomously for traversing public roadways and other environments to achieve the destination or route. As a result of autonomous control, the vehicle  100  and the various functional subsystems may be subject to substantially different usage scenarios than those of conventional human-operated vehicles, which may allow for substantial departures in conventional arrangements and operation of functional subsystems traditionally found in human-operated vehicles. The present disclosure is more particularly directed to various embodiments of a deceleration or braking subsystem, which may include friction brakes at inboard locations, may subject such friction brakes to significantly less frequent operation than friction brakes of human-operated vehicles, and may eliminate friction brakes at outboard locations as are found in human-operated vehicles (i.e., proximate vehicle wheels). For example, outboard friction brakes may not be included for rear wheels, front wheels, or both. 
     Referring to  FIG. 1 , the vehicle  100  generally includes a vehicle body  102  and an autonomous drive system  120  connected to the vehicle body  102 . The vehicle body  102  may, for example, include or define a passenger compartment for carrying passengers. The autonomous drive system  120  is configured to move the vehicle  100 , including the passenger compartment, autonomously between locations without direct human control of the various subsystems described below (e.g., a current location and a destination location specified by a user, such as one of the passengers). The autonomous drive system  120  includes various functional subsystems, including a propulsion system  130  (i.e., for propelling the vehicle  100 ), a friction braking system  140  (i.e., for slowing the vehicle  100 ), a steering system  150  (i.e., for directing the vehicle  100  in different directions), a suspension system  160  (i.e., for supporting the vehicle  100 ), a sensing system  170  (i.e., for sensing various aspects of the vehicle  100 , including the various subsystems and the external environment), and a control system  180  (i.e., for controlling the various other subsystems individually or in a coordinated manner). The control system  180  may operate the various other subsystems, for example, by executing instructions for controlling output of the various subsystems according to related sensing (e.g., detecting roadways for driving therealong to a requested destination without further using input and detecting obstacles for avoidance thereof, for example, by accelerating, decelerating, and steering the vehicle  100 ). Various components, functions, and/or other aspects may be shared or integrated between these various subsystems. For example, as discussed in further detail below, deceleration may be provided cooperatively by the propulsion system  130  and the friction braking system  140 , which may be considered individually or cooperatively deceleration systems of the vehicle  100 . 
     Referring to  FIG. 2 , the vehicle  100  includes wheels  104  (e.g., four wheels, such as two front wheels and two rear wheels) that are coupled to and support the vehicle body  102  (e.g., on a public roadway). The wheels  104  may be coupled to the vehicle body  102 , for example, with the propulsion system  130 , the steering system  150 , and the suspension system  160 . The wheels  104  may include tires (not separately shown or labeled), such that each wheel  104  may be considered a subassembly of a wheel rim and a tire. 
     The propulsion system  130  generally includes one or more motors  232 , one or more gearboxes  234 , and drive shafts  236  (e.g., half-shafts) operatively connecting each wheel  104  to one of the gearboxes  234 . Broadly speaking, the motors  232  provide torque to the gearboxes  234 , the gearboxes  234  alter the output torque (e.g., increase) and output speed (e.g., decrease) of the motors  232 , and the drive shafts  236  transfer torque from the gearboxes  234  to the wheels  104 . The motors  232  may provide positive torque for propelling the vehicle  100  in a forward direction and for decelerating the vehicle  100  when moving in a rearward direction, and may provide negative torque for propelling the vehicle  100  in a rearward direction and for decelerating the vehicle  100  when moving in a forward direction. The motors  232  may also function as generator, when receiving torque from the wheels  104 , and function to recharge a battery (not shown) or other energy storage system of the vehicle  100 . As shown, the propulsion system  130  may include a front propulsion system  130   f  and a rear propulsion system  130   r  that each include two motors  232  coupled to a single gearbox  234  and associated with one drive shaft  236  and the one wheel  104  coupled thereto. Variations of the propulsion system  130  are contemplated, which may include a different number of driven wheels  104  (e.g., only front or rear wheels being driven), a different number of motors  232  associated with the wheels  104  (e.g., one motor  232  associated with two wheels  104 ), and a different number of gearboxes  234  associated with the wheels  104  (e.g., one gearbox  234  dedicated for each wheel  104 ). 
     The friction braking system  140  generally provides deceleration torque via friction for decelerating the vehicle  100  when moving in the forward direction and/or when moving in the rearward direction. The friction braking system  140  may be configured according to various different considerations, including functionality with other subsystems, location within the vehicle  100  or other subsystems, and operating principles and related components, as discussed in further detail below. 
     The steering system  150  generally includes one or more steering actuators  252  and steering linkages  254  operatively coupling each wheel  104  to one of the steering actuators  252 . Broadly speaking, the steering system  150  controls the pivoted position of the wheels  104  about generally vertical axes. The steering actuators  252  move the steering linkages  254  in inboard and outboard directions relative to the vehicle body  102  to, thereby, pivot the wheels  104  about the vertical axes. As shown, the steering system  150  may include a front steering system  150   f  and a rear steering system  150   r  that each include one steering actuator  252  that is associated with two steering linkages  254  and the wheels  104  coupled thereto. Variations of the steering system  150  are contemplated, which may include a different number of steering actuators  252  associated with the wheels  104  (e.g., one steering actuator  252  for each wheel  104 ). 
     The suspension system  160  generally includes a suspension actuator  262  and a suspension linkage  264  associated with each wheel  104 . Broadly speaking, the suspension system  160  controls vertical motion of the wheels  104  relative to the vehicle body  102 , for example, to ensure contact between the wheels  104  and a surface of the roadway and to limit the influence of roadway conditions on undesirable movements of the vehicle body  102 . The suspension system  160  may, for example, be an active suspension system in which the suspension actuators  262  provide positive and negative displacement of the wheels  104  relative to the vehicle body  102  (i.e., the suspension actuators  262  may move the wheels  104  up and down relative to the vehicle body  102 , as opposed merely constrain motion of the wheels  104  caused by external forces). As shown, the suspension system  160  may include a front left suspension system  160   fl , a front right suspension system  160   fr , a rear left suspension system  160   rl , and a rear right suspension system  160   rr , each of which include one suspension actuator  262  and one suspension linkage  264 . 
     The sensing system  170  includes sensors for observing external conditions of the vehicle  100  (e.g., location of the roadway and other objects) and conditions of the vehicle  100  (e.g., acceleration and conditions of the various subsystems and their components). The sensing system  170  may include sensors of various types, including dedicated sensors and/or functional components of the various subsystems (e.g., actuators may function as sensors). 
     The control system  180  includes communication systems and components (i.e., for receiving sensor signals and sending control signals) and processing components (i.e., for processing the sensor signals and determining control operations), such as a controller. The control system  180  may include various control subsystems, for example, associated with (or as part) of one or more of the various other subsystems described herein (e.g., the propulsion system  130 , the friction braking system  140 , etc.). 
     Referring to  FIG. 16 , a hardware configuration for a controller  1681  of the control system  180  is shown, which may be used to implement the apparatuses and systems described herein (e.g., to detect an impact upon occurrence thereof and/or predict an impact in expectation thereof, and to control the movement mechanisms). As an example, the controller  1681  may output a command, such as a voltage value, to the various subsystems of the autonomous drive system  120  in response to signals received from the sensors of the sensor system  170 . 
     The controller  1681  may include a processor  1681   a , a memory  1681   b , a storage device  1681   c , one or more input devices  1681   d , and one or more output devices  1681   e . The controller  1681  may include a bus  1681   f  or a similar device to interconnect the components for communication. The processor  1681   a  is operable to execute computer program instructions and perform operations described by the computer program instructions. As an example, the processor  1681   a  may be a conventional device such as a central processing unit. The memory  1681   b  may be a volatile, high-speed, short-term information storage device such as a random-access memory module. The storage device  1681   c  may be a non-volatile information storage device such as a hard drive or a solid-state drive. The input devices  1681   d  may include any type of human-machine interface such as buttons, switches, a keyboard, a mouse, a touchscreen input device, a gestural input device, an audio input device, the sensors of the sensor system  170 . The output devices  1681   e  may include any type of device operable to provide an indication to a user regarding an operating state, such as a display screen or an audio output, or any other functional output or control, such as the propulsion system  130 , the friction braking system  140 , the steering system  150 , and/or the suspension system  160 . 
     As referenced above, the friction braking system  140  may work in conjunction with other subsystems of the autonomous drive system  120  and, in particular, the propulsion system  130  to decelerate the vehicle  100 . More particularly, the propulsion system  130  is configured to decelerate the vehicle  100  in nearly all conditions, while the friction braking system  140  is actuated in limited (i.e., infrequent) circumstances to supplement the propulsion system  130  to decelerate the vehicle  100 . For example, the friction braking system  140  may be actuated in high deceleration scenarios (e.g., avoiding errant movement of an object into the roadway, such as an animal, a pedestrian, or cargo dropped from another vehicle) and/or to act redundantly to the propulsion system  130  (e.g., if having reduced deceleration capacity). As will be discussed in further detail below, the propulsion system  130  and the friction braking system  140  may be configured to control deceleration (e.g., deceleration torque) of each wheel  104  individually. 
     Referring to  FIG. 3 , in high deceleration scenarios, deceleration is limited by friction between the wheel  104  and the roadway.  FIG. 3  depicts a slip curve  304 ′ of deceleration (e.g., shown as deceleration torque) vs. slip for a single wheel  104 , and further depicts the deceleration (e.g., deceleration) provided by the propulsion system  130  and the friction braking system  140  over time and in various conditions. 
     During normal conditions (e.g., low deceleration events), deceleration torque of the propulsion system  130  (depicted as curve  330 ′) may provide deceleration torque in a range equivalent to approximately +/−0.2 g. Note that  FIG. 3  depict deceleration torque as positive, thus forward acceleration torque appears as negative. 
     During a high deceleration event, the propulsion system  130  may provide higher deceleration torque (depicted as curve  330 ″), while the friction braking system  140  provides supplemental deceleration torque (depicted as curve  340 ′). The cumulative deceleration torque (depicted as curve  306 ) is the sum of the deceleration torque provided by the propulsion system  130  (i.e., curve  330 ″) and the friction braking system  140  (i.e., curve  340 ′). 
     The deceleration torque of the propulsion system  130  and the friction braking system  140  may be controlled to maintain maximum deceleration (i.e., the peak of the slip curve  304 ′). In the implementation shown in  FIG. 3 , the friction braking system  140  is configured to maintain a substantially constant level of deceleration torque during the high deceleration event, while the propulsion system  130  is additionally configured to modulate (i.e., vary) the deceleration torque provided thereby, so as to maintain the amplitude of the cumulative braking deceleration torque (i.e., curve  306 ) near the peak achievable deceleration torque of the wheel  104  (i.e., the peak of the slip curve  304 ′). Alternatively, as shown in  FIG. 4 , the propulsion system  130  may be configured to maintain a substantially constant level of deceleration torque (depicted by curve  430 ′), while the propulsion system  130  is configured to modulate the deceleration torque  440 ′ provided thereby, so as to maintain the amplitude of the cumulative braking deceleration torque (i.e., curve  306 ). In each of the scenarios described in  FIG. 4 , the control system  180  is configured to control the propulsion system  130  and the friction braking system  140 , which cooperatively form a deceleration system, to output the torque from the propulsion system  130  (e.g., one of the motor-generators described below) and the braking system  140  (e.g., the inboard friction brakes as described below) to apply torque to the wheels to achieve the required (e.g., peak available) deceleration torque. For example, the control system  180  may receive, as inputs, torque measurements from the sensors  130  for the wheels, axles, motor-generators, and/or friction brakes. 
     Friction brake mechanisms  541  of the friction braking system  140  may be arranged at various locations. As shown in  FIG. 5 , which depicts the portions of the propulsion system  130 , the friction braking system  140 , the steering system  150 , and the suspension system  160  for one corner of the vehicle  100  (e.g., a front left corner), the friction brake mechanism  541  may be arranged at an inboard location relative to the wheel  104 , components of the propulsion system  130 , components of the steering system  150 , and/or components of the suspension system  160 . 
     The wheel  104  is functionally and structurally supported by the steering system  150  and the suspension system  160 . The wheel  104  may be coupled to a knuckle  504   a , which rotatably supports the wheel  104  with a bearing  504   b . The knuckle  504   a  is in turn pivotally supported and/or controlled by the steering system  150  and vertically supported and/or controlled by the suspension system  160 . The steering linkage  254  is coupled to the knuckle  504   a , while the steering actuator  252  is coupled to the vehicle body  102  to pivotally support and control pivotal motion of the wheel  104  relative to the vehicle body  102 . Similarly, the suspension linkage  264  is pivotally coupled to the knuckle  504   a  (or intermediate member), while the suspension actuator  262  is in turn coupled to the vehicle body  102  to support and control vertical motion of the wheel  104  relative to the vehicle body  102 . 
     The wheel  104  is additionally coupled to the propulsion system  130 . More particularly, constant velocity joints  536   a  (e.g., CV joints) are arranged between the wheel  104  and the drive shaft  236  and between the drive shaft  236  and the gearbox  234 . The constant velocity joints  536   a  allow the propulsion system to transfer torque to the wheel  104  as the position and orientation of the wheel  104  changes relative to the gearbox  234 . 
     The friction brake mechanisms  541  of the friction brake system  140  are arranged inboard of the wheel  104  (i.e., toward a center of the vehicle  100 ), further inboard of the outboard constant velocity joint  536   a  (i.e., that between the wheel  104  and the drive shaft  236 ), and still further inboard of the inboard constant velocity joint  536   a  (i.e., that between the drive shaft  236  and the gearbox  234 ). By arranging the friction brake mechanisms  541  at inboard locations, unsprung mass may be reduced and space in or near the wheel  104  may be freed for other uses, as compared to human-operated vehicles with conventional friction brakes located in the wheel. The friction brake mechanisms  541  at inboard locations may be particularly advantageous with the active suspension system having the suspension actuators  262 , which provide positive and negative displacement of the wheels  104  relative to the vehicle body  102 , by reducing the unsprung mass that the suspension actuators  262  may move up and down with the wheels  104  up and down relative to the vehicle body  102 . The friction brake mechanisms described herein (e.g.,  541 ) that are located at inboard locations (e.g., inboard of the constant velocity joint and/or not forming unsprung mass) may be referred to as inboard friction brakes. 
     Thus, in various embodiments, the vehicle  100  includes friction brake mechanisms  541  of a friction brake system  140 , which are arranged at locations inboard of the constant velocity joints  536   a  connecting the wheels  104  to the gearbox  234 . The vehicle  100  may additionally include no friction brake mechanisms at locations outboard of the constant velocity joints  536   a  (e.g., proximate or surrounded by wheels  104 ) for one or more (e.g., all) of the wheels  104 . The vehicle  100  may also include friction brake mechanisms  541  that do not form unsprung mass, and may further include no friction brake mechanisms that form unsprung mass. In each variation, the vehicle  100  may include an active suspension mechanism (e.g., suspension actuator  262  and suspension linkage  264 ) associated with each wheel  104  for which friction brake mechanisms  541  are arranged at an inboard location and/or are not arranged at an outboard location. 
     As discussed in further detail below, the friction brake mechanisms  541  may be arranged at inboard locations associated with various components of the propulsion system  130 , including various components of the motor  232  and the gearbox  234 . 
     Referring to  FIG. 6 , which is a partial cross-sectional view, the front propulsion system  130   f  includes two of the motors  232 , one gearbox  234  with two functional halves, and two of the drive shafts  236  coupled to the gearbox  234 . The rear propulsion system  130   r  may be configured similar to that shown and described for the front propulsion system  130   f . Further, as noted above, the propulsion system  130 , including the front propulsion system  130   f  and the rear propulsion system  130   r , may be configured in different manners (e.g., by having one gearbox associated with each wheel, having one motor drive two wheels, etc.). 
     Each of the motors  232  is a motor-generator that draws current from an electric power source (not shown or labeled; e.g., a battery  638 ) to produce an output torque and may produce current when receiving an input torque (e.g., to recharge the power source). Each motor  232  generally includes a stator  632   a  and a rotor assembly  632   b . The motor  232  may be coupled to the gearbox  234  with the stator  632   a  being stationary relative thereto and the rotor assembly  632   b  rotatable relative thereto. For example, the gearbox  234  may include a bearing shaft  632   c  that is fixed to (e.g., grounded) to the gearbox  234  and protrudes therefrom, and which is received within the rotor assembly  632   b . Bearings may be arranged between the bearing shaft  632   c  and the rotor assembly  632   b.    
     Each half of the gearbox  234  is associated with one of the drive shafts  236  and is configured to transfer torque between the motor  232  and the drive shaft  236  and may also change the torque and rotational speed between the motor  232  and the drive shaft  236 . Each functional half of the gearbox  234  generally includes an intermediate shaft assembly  634   a  and an output shaft assembly  634   b , which may be supported by bearings (not labeled) of a housing  634   c  of the gearbox  234 . The intermediate shaft assembly  634   a  transfers torque between the motor  232  and the output shaft assembly  634   b , which in turn transfers torque between the intermediate shaft assembly  634   a  and the drive shaft  236 . Torque is transferred between the rotor assembly  632   b , the intermediate shaft assembly  634   a , and the output shaft assembly  634   b  via gears (shown; not labeled) that engage each other and may change the torque and speed between the motor  232  and the drive shaft  236 , as referenced above. The drive shaft  236  may be coupled to the output shaft assembly  634   b  with the constant velocity joint  536   a  (e.g., CV joint) that allows the drive shaft  236  to pivot off-axis from the output shaft assembly  634   b , while still transferring torque therebetween. The gearbox  234  may be configured in various other manners, for example, including a different number of intermediate shaft assemblies and/or by transferring torque from one motor  232  to two drive shafts  236 . 
     As is also illustrated in  FIG. 6 , the propulsion system  130  may also include supplemental motor-generators  650 , such as one supplemental motor-generator  650  for each of the motor-generators  232  (e.g., referred to as primary motor-generators). The supplemental motor-generators  650  selectively transfer torque to the driven wheels  104  to provide additional torque for acceleration or deceleration of the vehicle  100 . For example, during high deceleration events, such as when require deceleration torque exceeds a torque capacity of the primary motor-generators  232 , as may be limited by the mechanical and/or electrical properties thereof or of the power source  638  associated therewith, the supplemental motor-generator  650  may provide supplemental torque to help achieve the required deceleration torque and assist decelerating the vehicle  100 . The supplemental motor-generator  650  may be associated with the same power source as the primary motor-generator  232  (e.g., the power source  638 ) or another power source/storage (e.g.,  652 ). The supplemental motor-generator  650  may be coupled to the gearbox  234  (e.g., permanently) to which the primary motor-generator  232  transfers torque. For example, the supplemental motor-generator  650  may be engaged with the intermediate shaft  634   a  thereof (e.g., engaging the same gear as the primary motor-generator  232  at a different circumferential location). The motor-generator  232  is selectively operated (e.g., by the control system  180 ) to selectively transfer the supplemental torque to the driven wheels  104  via the gearbox  234  to thereby supplement the torque (e.g., drive torque) provided by the primary motor-generator  232 . 
     Referring to  FIGS. 7-11 , the friction braking system  140  includes various friction brake mechanisms that are positioned inboard relative to the wheels  104 , for example, being coupled to or incorporated into the propulsion system  130  in various manners. The friction braking system  140  may include one friction brake mechanism for each wheel  104 . 
     As described above, the propulsion system  130  provides adequate deceleration torque in nearly all circumstances, such that the friction braking system  140  may be infrequently used. As such, consequences normally associated with friction brakes (e.g., wear, debris, replacement, and heat) in human-operated vehicles may have limited effect when incorporating the friction braking system  140  into or proximate the gearboxes  234  of the propulsion system  130 . Moreover, autonomous control may prevent operation of the vehicle  100  in manners that might otherwise consequential operation of the friction braking system  140  (e.g., preventing usage scenarios in which high deceleration events might occur in close time proximity to each other or based on temperature, such as by operating at lower speeds and/or preventing movement of the vehicle  100 ). 
     Referring specifically to  FIG. 7 , which depicts the front left half of the front propulsion system  130 ′, the friction braking system  140  includes friction brake mechanisms  741  (e.g., a front left friction brake mechanism  741   fl ) that provide deceleration torque to one of the wheels (e.g., a front left wheel). The friction brake mechanism  741  is operationally coupled to a back side of the motor  232  (i.e., opposite the side transferring torque to/from the gearbox  234 ), for example, to the rotor assembly  632   b  (as shown). The friction brake mechanisms  741  are arranged external to the gearbox  234  but may be coupled thereto and/or contained in a distinct housing therefrom. 
     Referring to  FIG. 8 , the friction braking system  140  includes friction brake mechanisms  841  (e.g., a front left friction brake mechanism  841   fl ) that provide deceleration torque to one of the wheels (e.g., a front left wheel). The friction brake mechanism  841  is operationally coupled to the intermediate shaft assembly  634   a  (e.g., to the shaft thereof). The friction brake mechanisms  841  are arranged internal to the gearbox  234 . 
     Referring to  FIG. 9 , the friction braking system  140  includes friction brake mechanisms  941  (e.g., a front left friction brake mechanism  941   fl ) that provide deceleration torque to one of the wheels (e.g., a front left wheel). The friction brake mechanisms  941  are operationally coupled to the output shaft assembly  634   b  (e.g., to the shaft thereof) of the gearbox  234 . The friction brake mechanisms  941  are arranged internal to the gearbox  234 . Alternatively, as shown in  FIG. 10  the friction braking system  140  may include friction brake mechanisms  1041  (e.g., friction brake mechanism  1041   fl ) that are also operationally coupled to the output shaft assembly  634   b , but arranged external to the gearbox  234 , for example, between the housing  634   c  and the constant velocity joint  536   a . The friction brake mechanism  1041  may, for example, be incorporated in a separate housing that is coupled to the housing  634   c  of the gearbox  234 . 
     Referring to  FIG. 11 , the friction braking system  140  may include friction brake mechanisms  1141  that are incorporated into the motors  232  (e.g., a front left friction brake mechanism  1141   fl ) and provide deceleration torque to one of the wheels (e.g., a front left wheel). The friction brake mechanisms  1141  are operationally coupled to the rotor assembly  632   b  and the bearing shaft  632   c  that is grounded to the gearbox  234  (or to another portion of the gearbox  234 ). The friction brake mechanisms  1141  are arranged internal to the motor  232  (e.g., within a housing thereof) radially inward of both the stator  632   a  and the rotor assembly  632   b . This arrangement may be advantageous for packaging purposes to limit the combined lateral size (i.e., inboard-outboard direction) of the motors  232  and the gearbox  234 . 
     It should be noted that, while the various different friction brake mechanisms  741 ,  841 ,  941 ,  1041 ,  1141  were discussed in the context of a front propulsion system  130   f  having two motors  232  (i.e., one for each wheel  104 ) and one gearbox  234  with two halves, the friction brake mechanisms may be incorporated in similar manners (e.g., locations) in propulsion systems  130  having different configurations. For example, in propulsion systems having one motor and one gearbox associated with two wheels, the friction braking system may include friction brake mechanisms operationally coupled to a back side of the motor (as with friction brake mechanism  741 ), operationally coupled to an intermediate shaft (as with friction brake mechanism  841 ), or be provided within a motor (as with friction brake mechanism  1141 ) and provide deceleration torque for the two wheels cooperatively. Friction brake mechanisms may also be operationally coupled to an output shaft assembly associated with each wheel inside or outside the gearbox (as with friction brake mechanisms  941  and  1041 ) to provide deceleration torque for the two wheels  104  individually. 
     Each of the different friction brake mechanisms  741 ,  841 ,  941 ,  1041 ,  1141  may be any one of the specific friction brake mechanisms discussed in below, including friction brake mechanism  1241  (e.g., a momentum brake mechanism), friction brake mechanism  1341  (e.g., a drum brake mechanism), friction brake mechanism  1441 , or another type of brake mechanism (e.g., having a brake caliper and rotor). 
     Referring to  FIGS. 12A-12B , the friction braking system  140  includes one or more friction brake mechanisms  1241 . The friction brake mechanism  1241  is a momentum brake, which uses inertia of the vehicle  100 , as transmitted through various shafts of the propulsion system  130 , to generate clamping or braking force. 
     The friction brake mechanism  1241  generally includes a rotor  1242  (e.g., screw nut), a friction body  1244 , and a clamping device  1246 . 
     The rotor  1242  generally includes a central portion  1242   a  (e.g., body) and an outer portion  1242   b  (e.g., rim, radially-extending, flange, or disc portion) extending radially outward from the central portion  1242   a . The rotor  1242  is threadably engaged to a shaft corresponding to one of the locations of the friction brake mechanisms discussed above (e.g., to the rotor assembly  632   b  with either of the friction brake mechanism  741 ,  1141 ; to the intermediate shaft assembly  634   a  with the friction brake mechanism  841 ; to the output shaft assembly  634   b  with either of the friction brake mechanisms  941 ,  1041 ). Hereinafter with reference to the friction brake mechanism  1241 , the shaft is identified as the shaft  1243 , but should be understood to be any of the rotor assembly  632   b , the intermediate shaft assembly  634   a , or the output shaft assembly  634   b.    
     The threaded engagement between the rotor  1242  and the shaft  1243  may, for example, be direct engagement between the rotor  1242  and the shaft  1243  as with a lead screw or with intervening rolling members as with a ball screw. As an alternative to threaded engagement, the rotor  1242  may function as a barrel cam having internal tapered slots in which are received rollers that are circumferentially fixed to the shaft  1243  (i.e., such that relative rotation causes the rollers to act on the tapered slot to bias the barrel cam and, thereby, the rotor  1242 ). In a still further alternative, the rotor  1242  may function as a ball ramp or face cam in which case an annular member (e.g., flange) is rotationally fixed to the shaft  1243  and axially engages a complementary annular member coupled to (or formed by) the rotor  1242 . The annular members have tapered (e.g., ramped surfaces) that engage each other (or via intervening rolling members or balls), such that relative rotation biases the annular member of the rotor  1242 . 
     While the threads are depicted as having a constant taper over the shaft  1243 , the threads may have varying tapers and/or be confined to the axial region of the shaft  1243  in which the rotor  1242  moves. Furthermore, the taper may vary in different manners, for example, by reducing in angle (i.e., for quick initial movement of the rotor  1242  and subsequent slower movement with higher force) or increasing in angle (i.e., for high initial force and subsequent reduced force). Varying tapers may also be used with the barrel cam and face cam configuration described above. 
     The friction body  1244  includes a friction material  1244   a  that faces the central portion  1242   a  of the rotor  1242  with an axial face shaped in a complementary manner (e.g., planar, as shown, or cone shaped, corrugated) to engage the central portion  1242   a  of the rotor  1242 , which functions as a friction surface of the rotor  1242 . The friction body  1244  is grounded (rotationally fixed) to the vehicle body  102  (e.g., through the housing  634   c  of the gearbox  234 ). The shaft passes through the friction body  1244  (inner periphery indicated by dashed lines) or clearance is otherwise provided therebetween to allow the shaft  1243  to rotate and the friction body  1244  be stationary. As an alternative to the rotor  1242  and the friction body  1244  directly engaging each other, a series of interleaved friction plates with appropriate friction material are alternatingly splined to the shaft  1243  and to ground (e.g., a clutch pack) and arranged axially between the rotor  1242 , which acts as an apply or compression plate to compress the interleaved friction plates. 
     The clamping device  1246  (e.g., caliper or rim brake) is configured to selectively clamp the outer portion  1242   b  of the rotor  1242  to slow rotation thereof. The clamping device  1246  is grounded to the vehicle body  102  (e.g., through the gearbox  234 ) to be rotationally fixed relative thereto. The clamping device  1246  is additionally configured to slide axially parallel with the shaft  1243  on which the rotor  1242  is threaded, for example, being mounted via an appropriate sliding bearing. The clamping device  1246  may, for example, be a caliper, such as an electro-mechanical caliper (e.g., actuated with a motor and ball screw or lead screw) or a hydraulically-actuated caliper (e.g., having master cylinder in fluidic communication with the clamping device  1246  and itself actuated by a motor-generator). 
     As an alternative to a caliper or other physical clamping device for slowing rotation of the rotor  1242 , the friction brake mechanism  1241  may instead incorporate an eddy current brake. The rotor  1242  includes brake fins (e.g., made of a conductive material, such as copper or aluminum), while coils are selective energized to produce a magnetic field that passes through the brake fins. Resultant eddy currents generate a torque opposed to rotation of the rotor  1242  (i.e., causing screw leads of the shaft  1243  to force the rotor  1242  toward the friction body  1244 ) and also dissipate energy. As a further alternative to a caliper or other physical clamping device for slowing rotation of the rotor  1242 , the friction brake mechanism  1241  may instead include linear actuator (e.g., motor and ball screw or lead screw) that presses axially on the outer portion  1242   b  of the rotor  1242  thereby creating friction therebetween (i.e., to slow rotation of the shaft  1243 ) and also biasing the rotor  1242  toward the friction body  1244 . 
     During normal operation (see  FIG. 12A ), the rotor  1242  is biased away from the friction body  1244  and rotates with the shaft  1243  that it is threaded on. For example, a spring  1248  (e.g., a wave or Belleville washer) may be interposed between the rotor  1242  and the friction body  1244  to bias the rotor  1242  away from the friction body  1244 . Axial movement of the rotor  1242  may, for example, be limited by an axial stop  1249  against which the rotor  1242  is pressed. Suitable bearings (not shown) may be arranged between rotating and grounded components to reduce friction and prevent wear. 
     During a high deceleration event (see  FIG. 12B ), the clamping device  1246  clamps the outer portion  1242   b  of the rotor  1242  to stop rotation thereof relative to the vehicle body  102 . As the shaft  1243  continues to rotate relative to the vehicle body  102  (e.g., from inertia of the vehicle  100  transferred through the wheel  104  and various components of the propulsion system  130  to the shaft  1243 ) and, thereby, the rotor  1242 , threads of the shaft  1243  force the rotor  1242  axially toward the friction body  1244  to overcome force of the spring  1248 . As a result, the central portion  1242   a  of the rotor  1242  engages the friction material  1244   a  of the friction body  1244  and, in turn, induces a deceleration torque on the shaft  1243 . As the rotor  1242  moves axially on the shaft  1243 , the clamping device  1246  slides axially with the rotor  1242 . 
     The friction brake mechanism  1241  generates a lateral force F brake  between the rotor  1242  and the friction body  1244  that multiplies clamping force F clamp  applied by the clamping device  1246  to the rotor  1242 . The lateral force F brake  of the rotor  1242  against the friction body  1244  is equal to 2×pi×T rim /1, where T rim  equals the torque applied by the clamping device  1246  to the rotor  1242  (i.e., to the rim or outer portion  1242   b  thereof) and 1 equals the lead of the shaft  1243  (i.e., F brake =2×pi×T rim ×1). The rim torque T rim  is equal to F rim ×R rim ×μ rim , where R rim  is the radius at which the clamping force F rim  is applied to the rotor  1242  and μ rim  is the friction between the clamping device  1246  and the rotor  1242  (i.e., T rim =F rim ×R rim ×μ rim ). Thus, the lateral force F brake  may be calculated as a function of the clamping force F rim  with known inputs of the screw lead  1 , radius R rim  at which the outer portion  1242   b  of the rotor  1242  is clamped, and the friction μ rim  between the clamping device  1246  and the outer portion  1242   b  of the rotor  1242 . Using, as an example, 1 (0.005), R rim  (150 mm), and μ rim  (0.4) as examples, the lateral force F brake  is 75 times the clamping force F rim . 
     The friction brake mechanism  1241  may be provided as a dry application (i.e., without oil) or as a wet application (i.e., with oil), for example, within the gearbox  234  or other housing. In the wet application, the friction materials may be partially bathed in the oil (e.g., that otherwise lubricating the gearbox  234 ), the friction body  1244  may be configured as multiple discs (e.g., the interleaved plates as described above), and/or the friction discs may be corrugated to entrap more oil. 
     Additional variations of the friction brake mechanism  1241  are contemplated. In one variation, the arrangement of the rotor  1242  and the friction body  1244  are reversed in which case the rotor  1242  grounded to the vehicle body  102 . The friction body  1244  is threaded on the shaft  1243  and displaced axially by the shaft  1243  when slowed by the clamping device  1246 . 
     Referring to  FIGS. 13A-13D , the friction braking system  140  includes one or more friction brake mechanisms  1341  configured as drum brakes. The friction brake mechanism  1341  generally includes a brake drum  1342  and brake shoes  1344  (shown in  FIGS. 13C and 13D ). The brake drum  1342  is rotatably fixed to a shaft  1343  that may extend through the friction brake mechanism  1341 . The brake shoes  1344  are pivotably grounded to the vehicle body  102 , for example, via a backing plate  1346  of the friction brake mechanism  1341 , which may be coupled to the gearbox  234 . The brake shoes  1344  are pivotable relative to the backing plate  1346 , so as to move into and out of engagement with an inner periphery of the brake drum  1342  and slow rotation of the shaft  1343 . The friction brake mechanism  1341 , by being a brake drum, may be self-energizing and may further be self-energizing in only one direction of rotation (as indicated by arrows of the shaft  1343  and the brake drum  1342  in  FIGS. 13C and 13D ). 
     The shaft  1343  is an appropriate shaft corresponding to the locations of the friction brake mechanisms discussed above (i.e., the rotor assembly  632   b  with either of the friction brake mechanism  741 ,  1141 ; the intermediate shaft assembly  634   a  with the friction brake mechanism  841 ; the output shaft assembly  634   b  with either of the friction brake mechanisms  941 ,  1041 ). Hereinafter with reference to the friction brake mechanism  1341 , the shaft  1343  is identified as the shaft  1343 , but should be understood to be any of the rotor assembly  632   b , the intermediate shaft assembly  634   a , or the output shaft assembly  634   b.    
     Referring to  FIGS. 13C and 13D , the brake shoes  1344  are pivotable between a disengaged position (see  FIG. 13C ) and an engaged position (see  FIG. 13D ) in which the brake shoes  1344  engage the brake drum  1342 . Each brake shoe  1344  is coupled to the backing plate  1346  and is pivotable about a pin  1346   a  thereof or other hinge point. Rather than a pin  1346   a , for example, the brake shoes  1344  and the backing plate  1346  may form sliding interfaces with complementary curvatures, which may shift the pivot point radially outward to optimize engagement (e.g., pressure distribution) of the brake shoes  1344  to the brake drum  1342 . For example, the brake shoes  1344  may have concave outer curvatures, while the backing plate  1346  forms complementary bosses that protrude radially inward to be received within the recesses. A sliding interface is formed therebetween with a pivot point nearer, coextensive with, or radially outward of the inner periphery of the brake drum  1342 . Furthermore, rather than pivoting, the brake shoes  1344  may be fixed to the backing plate  1346 , and be compliant to be movable into engagement with the brake drum  1342 . 
     The brake shoes  1344  are pivoted by actuation members  1348   a  (e.g., actuation bars, or linkage members). Each actuation member  1348   a  operatively couples each brake shoe  1344  with an opposing brake shoe  1344  (i.e., forming a pair of brake shoes  1344  on opposite sides of the brake drum  1342 ). The actuation member  1348   a  may slide radially relative to the brake drum  1342 , which ensures that equal force is applied from the actuation member  1348   a  to each brake shoe  1344  of the pair. Force is, thereby, balanced force from the brake shoes  1344  to the brake drum  1342 . As shown, the friction brake mechanism  1341  includes two pairs of brake shoes  1344  and two associated actuation members  1348   a ; however, the friction brake mechanism  1341  may include any suitable even number of brake shoes  1344 . The actuation members  1348  may also be viewed in  FIG. 13A , which is a partial cross-sectional view of the friction brake mechanism  1341 , which omits the brake shoes  1344 . 
     The actuation member  1348   a  functions as a cam member that is rotated in a small range of motion to bias the brake shoes  1344  radially outward into engagement with the brake drum  1342  and radially inward out of engagement with the brake drum  1342 . For example, as shown, the actuation member  1348   a  includes cam slots  1348   a ′ at each end thereof, which have received therein slide members  1344   a  (e.g., pins) of the pair of brake shoes  1344 . As the actuation member  1348   a  is rotated in one direction (e.g., clockwise as shown), a radially inward surface thereof engages a radially inward surface of the slide member  1344   a  to bias the end of the brake shoe  1344  outward and pivot the brake shoe  1344  outward into engagement with the brake drum  1342  (see  FIG. 13D ). As the actuation member  1348   a  is rotated in another or opposite direction (e.g., counterclockwise as shown), a radially outward surface thereof engages a radially outward surface of the slide member  1344   a  to bias the end of the brake shoe  1344  inward and pivot the brake shoe  1344  inward out of engagement with the brake drum  1342  (see  FIG. 13C ). 
     An angle of the radial inner surface of the cam slot  1348   a ′ relative to a tangential direction determines the radial force applied by the actuation member  1348  to the brake shoes  1344  and, in turn, the brake shoes  1344  to the brake drum  1342 . The radial inner surface of the cam slot  1348   a ′ may have a constant angle or may vary, for example, to initially move the brake shoes  1344  toward the brake drum  1342  and subsequently with high force, or vice versa (i.e., initially with high force, and subsequently with quick movement). As an alternative to the cam slot  1348   a ′ having two sides, the cam slot  1348   a ′ may instead be one-sided, engaging the slide member  1344   a  with only the radially inner surface, while a spring functions to return or bias the brake shoe  1344  away from the brake drum  1342 . As an alternative to the cam slot  1348   a ′, the actuation member  1348  may instead be rotated to engage a radially inward surface of the brake shoe  1344  to bias the brake shoe  1344  outward into engagement with the brake drum  1342 , while a spring biases (e.g., pulls or rotates) the brake shoe  1344  inward and out of engagement with the brake drum  1342 . 
     The actuation members  1348   a  are rotated by an actuation shaft  1348   b . The actuation shaft  1348   b , for example, includes protrusions  1348   b ′ that extend into radially-extending slots  1348   a ″ of the actuation members  1348   a . As the actuation shaft  1348   b  is rotated in either direction, the protrusions  1348   b ′ engage outer surfaces of the radially-extending slots  1348   a ″ to pivot the actuation members  1348   a . As force is balanced between the pair of brake shoes  1344  operated by the actuation member  1348 , the actuation member  1348  may move radially as the protrusions  1348   b ′ of the actuation shaft  1348   b  slide within the radially-extending slots  1348   a ″. The actuation shaft  1348   b  operates (i.e., pivots) all actuation members  1348   a . Additionally, the shaft  1343  passes through central apertures of the actuation members  1348  and a central bore of the actuation shaft  1348   b.    
     The actuation shaft  1348   b , and thereby the actuation members  1348   a , are rotated by a motor-generator (not shown) with appropriate gear reduction for increased torque. The motor-generator may be direct drive, or geared (e.g., planetary, spur, or helical) for increasing torque output. It should be noted that the actuation shaft  1348   b  pivots in a short range of motion that is dictated by the length and radial location of the cam slots  1348   a ′ of the actuation members  1348   a . The range of motion may, for example, less than 15 degrees. In one example, the actuation shaft  1348   b  may include or be coupled to a sector gear that is engaged by a pinion of the motor-generator to be rotated thereby. In another example, a belt may extend between an output of the motor and pulley of the actuation shaft  1348   b  for the motor to rotate the actuation shaft  1348   b . In yet another example, the motor-generator may be coupled to a linear actuator (e.g., lead screw, ball screw, or roller screw), which is in turn coupled to the actuation shaft  1348   b  via a linkage (e.g., lever). As a still further alternative, the motor-generator may be concentric with the shaft  1343  (e.g., as a hollow motor) with the stator being coupled to the actuation shaft  1348   b  and the stator being coupled to ground. 
     To facilitate cooling, the brake drum  1342  may include fins, for example, to increase surface area and/or to function as a fan to pull air through the fins and around the drum. 
     Referring to  FIGS. 14A-14B , the friction braking system  140  includes one or more friction brake mechanisms  1441 , which are passively operated (i.e., without direct actuation) with onset high deceleration torque transferring through the propulsion system  130 . More particularly, the propulsion system  130  utilizes helical gears to transfer torque between components, such that when the magnitude of torque transfer is increased (e.g., during a high deceleration event), various components are biased axially into contact with grounded friction elements. 
     Each friction brake mechanism  1441  is provided within the gearbox  234 , and multiple friction brake mechanisms  1441  may be associated with each wheel  104 . For example, as shown in  FIGS. 14A-14B , two friction brake mechanisms  1441  are provided for the front left wheel  104 . 
     The friction brake mechanism  1441  generally includes a friction member  1442  and a spring  1444 , while the various shafts of the propulsion system  130  (e.g., the rotor assembly  632   c , the intermediate shaft assembly  634   a , and the output shaft assembly  634   b ) include helical gears (shown; not labeled). The friction member  1442  is grounded, for example, being coupled to the housing  634   c  of the gearbox  234 . 
     Each spring  1444  (e.g., a Belleville washer) biases one of the shafts of the propulsion system  130  axially away from the friction member  1442 . For example, the spring  1444  may be compressed between the friction member  1442  and the gear (or other annular member) of the shaft. Appropriate bearings may additionally be arranged between the friction member  1442 , the spring  1444 , and the gear (or other portion of the shaft) to reduce friction and wear. 
     During normal driving conditions, low levels of deceleration torque are transferred between the helical gears of the various shafts. As a result, low levels of axial force act between the helical gears. These low levels of axial force are insufficient to overcome the force of the springs  1444 , such that the shafts do not move axially (see  FIG. 14A ). 
     During a high deceleration event, high levels of deceleration torque (e.g., generated by the motor  232  and transferred to the wheel  104 ) between the helical gears the various shafts. These high levels of axial force are of sufficient to overcome the force of the springs  1444  and compress the spring  1444 , such that the respective shafts translate axially. As a result, axial faces of the helical gears (or other annular members) of the rotor assembly  632   c  and the intermediate shaft assembly  634   a  engage the friction members  1442  (see  FIG. 14B ) to generate deceleration torque. 
     The output shaft assembly  634   b  if fixed axially in the gearbox  234  (e.g., having a thrust washer) to provide an axial reaction force  FR . The reaction force  FR  is ultimately transferred as axial braking forces F B1  and F B2  to the friction brake mechanisms  1441  to both generate deceleration torque and overcome the forces of the spring  1444 . These axial reaction force  FR  and the axial braking forces F B1  and F B2  are a function of the input torque (i.e., the deceleration torque introduced by the motor  232  and transferred to the wheel  104 ) and the geometry of the helical gears (e.g., relative diameters and tooth geometry). 
     Referring to  FIGS. 15A and 15B , a propulsion system  1530  is configured to provide additional deceleration torque in high deceleration events using another motor of the vehicle (e.g., of the propulsion system  1530 ). The motor may, for example, primarily have another function (e.g., torque vectoring) but may be selectively operated to provide added deceleration torque in high deceleration situations. 
     The propulsion system  1530  (e.g., a rear propulsion system) generally includes a drive motor  1532  (e.g., a motor-generator), a differential  1534 , and a torque vectoring system  1536 . The drive motor  1532  transfers torque to/from the differential  1534 , for example, via intermediate reducing gears (e.g., a gear train). The reducing gears may, for example, include an input drive gear  1538   a , which transfers torque to/from a pinion of the drive motor  1532 , and an output gear  1538   b , which transfers torque to/from the differential  1534 . The differential  1534 , in turn, transfers torque from the drive motor  1532  to the driven wheels  104  coupled thereto, while allowing unequal rotation therebetween. The input drive gear  1538   a  and the output gear  1538   b  are rotatably fixed to each other via a shaft  1538   c . The output gear  1538   b  has a smaller diameter than the input drive gear  1538   a , so as to reduce rotational speed and increase torque from the drive motor  1532 . 
     The torque vectoring system  1536  normally operates to distribute torque between wheels  104  (e.g., a rear left wheel  104 , and a rear right wheel  104 ). The torque vectoring system  1536  generally includes a torque vectoring gearbox  1536   a  and a torque vectoring motor  1536   b . The torque vectoring gearbox  1536   a  may, for example, include a planetary gear set, which receives input torque from the torque vectoring motor  1536   b  for applying differential torque between the driven wheels  104  for stability of the vehicle  100 . For example, the torque vectoring motor  1536   b  may selectively apply torque to a planet carrier  1536   a ′ of the torque vectoring gearbox  1536   a  (or other suitable input). The differential  1534  and the torque vectoring system  1536 , including the various gears thereof, may be provided as a combined gearbox (e.g., the gearbox  234 ). Furthermore, braking system  140  may be used in conjunction with the propulsion system  1530  with the inboard friction brakes configured and/or located as described previously (e.g., as with the friction brake mechanisms  541 ,  741 ,  841 ,  941 ,  1041 ,  1141 ,  1241 ,  1341 ,  1441 ). In one example, the differential  1534  and the torque vectoring gearbox  1536   a  are provide as a single gearbox with an inboard friction brake contained therein. 
     In one example, the propulsion system  1530  is a rear propulsion system with the rear wheels being driven wheels. The braking system  140  may include friction brakes for applying braking torque to the rear wheels, which may be outboard brakes or inboard brakes as described previously (e.g., within the single gearbox forming the differential and/or not forming unsprung weight). Instead, or additionally, the braking system  140  may include friction brakes for applying braking torque to the front wheels, which may be outboard brakes or inboard brakes as described previously (e.g., not forming unsprung weight). 
     During normal operation, the torque vectoring motor  1536   b  is engaged with the torque vectoring gearbox  1536   a  to provide torque thereto (i.e., for distributing torque between the wheels  104 ) (see  FIG. 15A ). For example, a pinion gear  1536   c  of the torque vectoring motor  1536   b  may be engaged with an input of the torque vectoring gearbox  1536   a.    
     During a high deceleration event, the torque vectoring motor  1536   b  is instead engaged with the output gear  1538   b , which otherwise transfers torque between the differential  1534  and the drive motor  1532 . For example, the pinion gear  1536   c  of the torque vectoring motor  1536   b  may be moved axially (e.g., by an actuator; not shown) on an output shaft  1536   d  of the torque vectoring motor  1536   b  out of engagement with the torque vectoring gearbox  1536   a  and into engagement with the input drive gear  1538   a . As a result, both the drive motor  1532  and the torque vectoring motor  1536   b  may simultaneously provide deceleration torque via the input drive gear  1538   a  to the differential  1534  and, ultimately, the wheels  104 . In such case and if friction brakes are provided for applying deceleration torque to the driven wheels  104 , the friction brakes, instead of the torque vectoring motor  1536   b , may provide unequal torque to the driven wheels for vehicle stability. The torque vectoring motor  1536   b  may be connected to the input drive gear  1538   a  in the same manner to provide additional drive torque to the differential  1534  provide supplemental drive torque for accelerating the vehicle. 
     A synchromesh unit may be used to ensure proper engagement (e.g., receipt) of the pinion gear  1536   c  of the torque vectoring motor  1536   b  with the input drive gear  1538   a . Alternatively, the positions and/or speeds of each of the input drive gear  1538   a  and the pinion gear  1536   c  of the torque vectoring  1536   b  may be known/detected and/or controlled (e.g., by the sensing system  170 ) to ensure proper engagement (e.g., receipt) of the pinion gear  1536   c.    
     While the disclosure has been described in connection with certain embodiments, it is to be understood that the disclosure is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.

Metadata:
Filing Date: 20190409
Publication Date: 20221115
Grant Date: 20221115
Priority Date: 20180409
Inventors: MADHANI, AKHIL J.
THOMASSON, DILLON J.
AUGENBERGS, PETERIS K.
HITZINGER, ALEXANDER
Assignee: APPLE INC
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Family ID: 84000688