Controlling a vehicle brake system

Abstract

Aspects of the invention relate to a control system (110) for controlling a brake system (101) of a vehicle (10) when a motor brake (122) of the brake system (101) is in a clearance region. An allowable torque that is less than the available torque of the motor brake (122) may be calculated such that the motor brake (122) is limited during the lash. In this manner, the motion of the vehicle (10) may be smoother when the requested braking torque increases rapidly.

Description

Technical Field

[0001] This disclosure relates to controlling a vehicle braking system. Aspects of the invention relate to a control system for controlling a vehicle braking system, a system including a control system, a braking system, a vehicle including a braking system, and a method for controlling a vehicle braking system. Background Technology

[0002] A motor for a vehicle is known to reverse its polarity during vehicle deceleration in order to function as a generator that converts the vehicle's kinetic energy into electrical energy. This is known as regenerative braking. During this change in torque direction, each motor can pass through a gap. This gap, sometimes called backlash, is a point where the mechanical system can move without transmitting force to a second part of the system due to clearances in gears, elasticity in mounting components, etc. When the motor is in the gap region, a rapid increase in torque demand from the motor can cause shunting and slippage. Similar drivetrain disturbances can occur outside the gap region when a rapid increase in torque occurs.

[0003] The purpose of this invention is to address one or more of the disadvantages associated with the prior art. Summary of the Invention

[0004] Various aspects and embodiments of the present invention provide control systems, systems, vehicles, methods for controlling braking systems of vehicles, and computer-readable instructions as claimed in the appended claims.

[0005] According to one aspect of the invention, a control system for controlling a braking system of a vehicle is provided, the vehicle having a motor arranged to function as an electric motor brake of the vehicle, the control system comprising one or more processors, said one or more processors being jointly configured to: determine an allowable torque for the electric motor brake when the motor is in a gap region, wherein the allowable torque is less than or equal to the available torque for the electric motor brake; and output the determined allowable torque to the electric motor brake.

[0006] According to another aspect of the invention, a control system for controlling a braking system of a vehicle is provided, the vehicle having a motor arranged to function as an electric motor brake of the vehicle, the control system comprising one or more processors, said one or more processors being jointly configured to, when the motor is in a gap region: receive a signal indicating a vehicle braking request; receive a signal indicating an available torque of the electric motor brake; determine an allowable torque for the electric motor brake that is less than or equal to the available torque; and output a determined allowable torque signal representing the determined allowable torque to be applied by the electric motor brake.

[0007] The terms relating to the motor or torque command entering, being in, or leaving a gap can be interpreted as the torque generated by the motor decreasing to a value below the gap threshold, remaining below the gap threshold, and increasing above the gap threshold, respectively. While the gap threshold is generally symmetrical about the zero torque point, it should be understood that asymmetrical gap thresholds can also exist, and that the gap threshold for positive torque can differ from the gap threshold for negative torque. Furthermore, it should be recognized that gaps can exist throughout the powertrain, such as in the transmission, differential, motor mount, and drive shaft. However, for ease of reference, it is said that the motor experiences a gap, rather than referring to each or every component of the associated powertrain.

[0008] The ability of a powertrain to perform Category B regenerative braking depends on the capability of the electric motor brake. A rapid increase in torque demand requested from the electric motor brake can cause slippage and shunting in the powertrain. This can be avoided by determining the available torque that the electric motor brake can deliver without causing shunting and slippage. The permissible torque can then be determined as a torque value less than or equal to the available torque, and the permissible torque can then be applied by the electric motor brake. In this case, "less than" refers to the magnitude of the signal, and the braking signal can generally be considered a negative torque value.

[0009] One or more processors can also be configured to repeatedly determine the allowable torque to gradually increase the allowable torque.

[0010] The allowable torque can be determined such that it increases steadily as the motor brake's capacity increases, while still remaining less than or equal to the available torque.

[0011] One or more processors may also be configured to: receive an allowable torque signal; repeatedly determine an available torque that maintains or reduces the difference between the available torque and the allowable torque signal; and output the determined available torque signal.

[0012] This prevents any subsequent abrupt step changes in the permissible torque of the output, which could otherwise cause shunting. The available torque can be calculated within the motor brake controller, and the permissible torque can also be calculated within the brake controller.

[0013] Based on the available torque for the motor brake, one or more processors can repeatedly determine the permissible torque for the motor brake until the braking system leaves the gap region; and output the permissible torque to the motor brake.

[0014] The permissible torque can be repeatedly redefined until it is no longer needed. The increment of the permissible torque can be monotonically (of the same magnitude) or increase steadily.

[0015] One or more processors may be configured to: determine the required vehicle braking torque to satisfy the vehicle braking request; determine the difference between the required vehicle braking torque and the determined permissible torque; and output a signal indicating the required friction braking torque to the friction brake based on the difference.

[0016] The remaining portion of the required braking torque can be absorbed by the friction brake to ensure that the vehicle's braking request is met, while the capacity of the electric motor brake is increased.

[0017] The clearance region can be defined as the torque value of the motor brake within the non-zero tolerance band near zero torque.

[0018] The ability of an electric motor brake to withstand sudden increases in torque demand, including both negative and positive torque, within the range of drivetrain torque values ​​may be limited. This ability may be related to inverter or power supply constraints, or to undesirable noise, vibration, or roughness within the drivetrain or mounting system.

[0019] The permissible torque can be determined based on the instantaneous torque capability of the motor brake within the above constraints.

[0020] The permissible rate of increase in desired torque varies depending on several factors, including current vehicle speed and drivetrain torque. Providing instantaneous torque capability helps ensure optimized performance of the electric motor brakes in regenerative braking.

[0021] One or more processors may be configured to: determine the required vehicle braking torque to satisfy a vehicle braking request; determine the distribution of the required vehicle braking torque among one or more motor brakes in a first group associated with a first axle of the vehicle and one or more motor brakes in a second group associated with a second axle of the vehicle, wherein the distribution of the required vehicle braking torque to each motor brake is determined based on a corresponding permissible torque rate for each motor brake; and output the corresponding determined permissible torque to each motor brake.

[0022] The distribution of braking torque requested by an electric motor brake can be affected by the capabilities of other electric motor brakes. For example, once one of the electric motor brakes leaves the clearance region, the requested braking torque from all the electric motor brakes can increase. Other factors may also affect braking torque distribution, such as maintaining vehicle stability.

[0023] The control system includes one or more controllers, which collectively include: at least one electronic processor having an electrical input for receiving an input signal; and at least one memory device electrically coupled to the at least one electronic processor and having instructions stored therein; and wherein the at least one electronic processor is configured to access the at least one memory device and execute instructions thereon to perform the operation of the control system as defined with reference to the foregoing aspects of the invention.

[0024] According to another aspect of the present invention, a system is provided, the system comprising a control system and a powertrain control module, the powertrain control module being configured to: determine an instantaneous torque capability for one or more motor brakes based on the configuration of the motor brake in a gap region; output the instantaneous torque capability as an available torque signal to the control system; and wherein the control system is configured to determine that the permissible torque for the motor brake is less than or equal to the available torque signal for the motor brake.

[0025] The powertrain control module can be configured to calibrate the permissible rate of increase of the instantaneous torque capability of the electric motor brake, so that the latest permissible value can be determined based on the current capability of the electric motor brake according to the current vehicle parameters.

[0026] The permissible torque of an electric motor brake can depend on the vehicle's speed and the torque of the powertrain.

[0027] The parameters for determining the permissible torque of an electric motor brake can be based on various factors, including vehicle speed and powertrain torque.

[0028] According to another aspect of the present invention, a braking system is provided, the braking system comprising: a control system or system; at least one friction brake; and at least one electric motor brake.

[0029] According to another aspect of the present invention, a vehicle including a braking system is provided.

[0030] The vehicle may include a first powertrain and a second powertrain. Each powertrain may drive one wheel of the vehicle or a pair of wheels. The first powertrain may drive a first axle, which in turn drives the front wheels of the vehicle, and the second powertrain may drive a second axle, which in turn drives the rear wheels of the vehicle. Alternatively, the first and second powertrains may drive individual wheels, such as a first wheel located on the left side of the vehicle and a second wheel located on the right side of the vehicle.

[0031] Each powertrain may include an electric motor brake associated with each corresponding wheel. Each wheel may be associated with a corresponding friction brake, which is configured to apply friction braking torque to the wheel.

[0032] According to another aspect of the invention, a method is provided for controlling a vehicle's braking system when the electric motor brake of the vehicle's braking system is in a gap region, the method comprising: receiving a signal indicating a vehicle braking request; receiving a signal indicating an available torque for the electric motor brake; determining a permissible torque for the electric motor brake, wherein the permissible torque is less than or equal to the available torque; and outputting the determined permissible torque to the electric motor brake.

[0033] The ability of a powertrain to perform Category B regenerative braking depends on the capability of the electric motor brake. A rapid increase in torque demand requested from the electric motor brake can cause slippage and shunting in the powertrain. This can be avoided by determining a permissible torque that is a positive torque value less than the available torque that the electric motor brake can deliver without causing shunting and slippage.

[0034] The method may further include: repeatedly determining an increase in allowable torque that is less than or equal to the available torque; and outputting the determined allowable torque to the motor brake.

[0035] The permissible torque can be determined to increase steadily as the capacity of the motor brake increases.

[0036] The method may further include: repeatedly determining an available torque that maintains or reduces the difference between the available torque and the permissible torque; and outputting the determined available torque.

[0037] This prevents the available torque from increasing when the permissible torque does not increase, and thus prevents any subsequent abrupt step changes in the permissible torque of the output, which could otherwise lead to shunting.

[0038] According to another aspect of the invention, a computer-readable instruction is provided, which, when executed by a computer, is arranged to perform the method.

[0039] Within the scope of this application, it is expressly intended that various aspects, embodiments, examples, and alternatives set forth in the preceding paragraphs, claims, and / or the following description and drawings, and in particular their various features, may be adopted independently or in any combination. That is, all embodiments and / or features of any embodiment may be combined in any manner and / or combination unless such features are incompatible. The applicant reserves the right to amend any originally filed claim or accordingly file any new claim, including the right to modify any originally filed claim to incorporate any feature dependent on and / or incorporated into any other claim, although not initially claimed in this manner. Attached Figure Description

[0040] One or more embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

[0041] Figure 1 A vehicle according to an embodiment of the present invention is shown;

[0042] Figure 2 A block diagram illustrating components of a vehicle according to an embodiment of the present invention is shown;

[0043] Figure 3 A flowchart illustrating a method according to an embodiment of the present invention is shown.

[0044] Figure 4 A graph indicating the increase in permissible torque for an electric motor brake according to an embodiment of the present invention is shown;

[0045] Figure 5 A graph indicating the limit of permissible torque for an electric motor brake according to another embodiment of the invention is shown;

[0046] Figure 6 A block diagram illustrating components of a vehicle according to another embodiment of the present invention is shown; and

[0047] Figure 7 A flowchart illustrating a method according to another embodiment of the present invention is shown. Detailed Implementation

[0048] This article refers to Figure 1 A vehicle 10 according to an embodiment of the present invention is described.

[0049] Vehicle 10 includes a control system 110, a powertrain 120, and a friction braking system 130. The control system 110 is arranged to control the powertrain 120 and the friction braking system 130. The powertrain 120 and the friction braking system 130 form part of the vehicle braking system 101 of vehicle 10, as will be further explained below. Vehicle 10 may be a battery electric vehicle (BEV) powered by only one or more electric motors, or a hybrid electric vehicle (HEV) having an electric motor and an internal combustion engine, both arranged to drive the vehicle's wheels.

[0050] Figure 2A schematic diagram of the components of vehicle 10 is shown. The control system 110 of vehicle 10 includes multiple processors. The processors are collectively configured to receive data from various sensors, systems, and input devices of vehicle 10, process the data, and output commands for controlling vehicle 10. Each processor may individually or collectively include a processing device and a memory device. The processing device may be one or more electronic processing devices capable of executing computer-readable instructions in an operable manner. The memory device may be one or more memory devices. The memory device is electrically coupled to the processing device. The memory device is configured to store instructions, and the processing device may be configured to access the memory device and execute the instructions stored thereon.

[0051] The control system 110 is arranged to control the power system 120. The power system 120 includes one or more motors 122.

[0052] In the acceleration drive mode of vehicle 10, motor 122 can be used as a power source 122 configured to power one or more axles 140 of vehicle 10, wherein the axles 140 are arranged to drive the wheels of vehicle 10. Control system 110 is arranged to output a motor torque demand signal 121 to powertrain 120 to cause motor 122 to generate the required amount of torque to meet the requested acceleration. Powertrain 120 includes transmission 124, which is arranged to receive torque 125a from motor 122, convert the torque, and provide the converted torque 127a to axles 140. Control system 110 is also arranged to receive data 123 from powertrain 120. The received data 123 may include performance data related to powertrain 120.

[0053] In the deceleration drive mode of vehicle 10, negative torque 127b from axle 140 is provided to transmission 124, and torque 125b from transmission 124 is transmitted to motor 122. In this mode, motor 122 acts as a generator to convert torque into electricity, and in doing so, decelerates vehicle 10. This can be referred to as regenerative braking, and motor 122 in this drive mode is referred to as motor brake 122.

[0054] Vehicle 10 includes a friction braking system 130, which can supplement the deceleration provided by the electric motor brake 122. The friction braking system 130 is arranged to receive commands 131 from control system 110 and transmit data 133 to control system 110.

[0055] Friction braking system 130 includes a brake actuator 132 and a friction brake 134. The term "friction brake" is generally used herein to refer to any friction brake that can decelerate a vehicle by converting kinetic energy into heat through friction. Alternatively, friction braking system 130 may be referred to as a basic braking system. Brake actuator 132 may be a hydraulic pump or electromechanical actuator for moving components of friction brake 134, the components of friction brake 134 being arranged in frictional engagement to provide braking torque. Thus, brake actuator 132 can apply force 135 to friction brake 134. Friction brake 134 can be any friction brake, such as a brake disc with movable brake calipers or a drum brake with movable brake shoes. By moving the components of friction brake 134 into engagement, friction braking system 130 can provide frictional braking torque 137 to axle 140 to decelerate the vehicle.

[0056] It will be understood that the control system 110 may consist of multiple separate controllers or processors, and the signals typically described as being received or output by the control system may be published on a central CAN bus, or may be output by only one part of a computer program and received by another part of the computer program. The received signals may also be retrieved from internal memory or determined by a program within the control system 110. Other vehicle networks are available and are equivalent to the CAN bus herein.

[0057] The control system 110 is arranged to receive acceleration or deceleration requests 103 from a driver input device 102, such as an accelerator pedal or a brake pedal. In the transition between an acceleration mode in which the motor 122 drives the drivetrain 124 and a deceleration mode in which the motor 122 is driven by the drivetrain 124, the torque direction of the motor 122 changes. In other words, the motor 122 changes from generating positive torque to receiving negative torque. Requests for braking can originate from the brake pedal, or can be provided in a manner similar to over-limit braking in a vehicle with an internal combustion engine when the accelerator pedal is depressed below a threshold position. Braking requests can also originate from driver assistance systems, such as cruise control.

[0058] During at least a portion of this transition, the motor 122 will traverse a transition region known as a gap region. Gaps may occur when the torque applied through the components of the powertrain 120 is removed and subsequently reapplied during the transition, due to idling caused by clearance or gaps between the components of the powertrain 120 when the applied torque reverses direction. Gaps can cause slippage, diversion, bumping, or other generally undesirable disturbances to the vehicle 10 that can be perceived by the occupants of the vehicle 10.

[0059] It is generally desirable to minimize frictional losses caused by the use of the friction braking system 130, so that deceleration is provided entirely or primarily by the powertrain 120 (via the electric motor brake 122), thereby maximizing the utilization of regenerative braking. However, with the reduced over-limit operating levels in new-generation electric vehicles, regenerative braking of the vehicle 10 in coasting conditions has become more challenging. In particular, the electric motor brake 122 is more likely to be in a gap region during coasting. In this gap region, the electric motor brake 122 cannot deliver rapid changes in torque demand without causing slippage, shunting, and other disturbances.

[0060] To mitigate these disturbances, the permissible torque of the motor brake 122 can be limited. Typically, the limit may include a slope, where the rate of change of the permissible torque is calibrated.

[0061] Figure 3 The illustration depicts a method 200 according to an embodiment of the present invention. Method 200 involves braking a vehicle 10, for example, when the electric motor brake 122 of the vehicle braking system 101 is in a gap region. Figure 1 The method for controlling the vehicle braking system 101 of the vehicle 10 illustrated herein. In this document, the clearance region includes the zero torque value of the electric motor brake 122, although the clearance region will generally be included in a non-zero tolerance zone near zero torque, such that the clearance region is defined between a positive (upper) torque threshold and a negative (lower) torque threshold. Furthermore, the ability of the electric motor brake 122 to withstand sudden changes in torque demand (both positive and negative torque) can be encompassed within the range of the drivetrain torque values. While the clearance threshold is generally symmetrical about the zero torque point, it will be understood that asymmetrical clearance thresholds can also exist, and the clearance threshold for positive torque can differ from the clearance threshold for negative torque.

[0062] Method 200 can be derived from Figure 1 and Figure 2 The control system 110 illustrated herein executes the method. In particular, the control system may include a memory that may include computer-readable instructions that, when executed by a processor, perform the method 200 according to an embodiment of the invention.

[0063] At step 201, the control system 110 is configured to receive a signal 103 indicating a vehicle braking request (i.e., a deceleration request signal). The vehicle braking request can be received from a driver input device 102, such as the brake pedal. Alternatively, the vehicle braking request can be received from an automated driving system or an advanced driver assistance system (ADAS), such as emergency braking or adaptive cruise control. In some driving modes, the vehicle braking request can also be inferred from the removal of an acceleration request, i.e., when the driver releases pressure on the accelerator pedal.

[0064] At step 202, the control system 110 is configured to determine the required vehicle braking torque to satisfy the vehicle braking request. The required vehicle braking torque is a combined braking torque required from the powertrain 120 and the friction braking system 130 to satisfy the requested deceleration of the vehicle 10 received at step 201.

[0065] At step 203, the control system 110 is arranged to receive a signal indicating the available torque for the electric motor brake 122. The available torque can be considered as the maximum capacity of the electric motor brake 122 during normal operation. In situations where the powertrain 120 and thus the electric motor brake 122 need to generate torque in the clearance region, full utilization of the available torque may, in some cases, cause disturbances to driving performance, such as slippage and shunting. Therefore, the control system 110 is arranged to control the permissible torque for the electric motor brake 122.

[0066] At step 204, the control system 110 is arranged to determine a permissible torque for the motor brake 122 that is less than or equal to the available torque for the motor brake 122. The permissible torque is determined to be a value that will avoid or substantially reduce interference that might otherwise occur when fully utilizing the available torque. When the motor brake 122 is in the clearance region, the permissible torque will be a non-zero, non-negative value less than the available torque. In this case, the non-negative value refers to the braking torque.

[0067] Return to Figure 2 The powertrain 120 includes a powertrain control module 126, which can be arranged to determine the instantaneous torque capability for the electric motor brake 122 and continuously feed this instantaneous torque capability 129 to the control system 110. In this way, the latest permissible value can be determined based on the current capability of the electric motor brake 122 according to current vehicle parameters. For example, a powertrain torque value 128 can be sent to the powertrain control module 126. The instantaneous torque capability can depend on several parameters, including vehicle speed and battery level, and includes tolerances based on the condition of the components of the powertrain 120. For example, a battery nearing its maximum capacity may require a reduced charging rate, which may limit the braking torque that can be obtained from the electric motor brake.

[0068] At step 205, the control system 110 outputs the determined permissible torque of the motor brake 122. This provides an upper limit for the torque request from the vehicle braking system 101 to the powertrain 120. To meet the required vehicle braking torque, the utilization rate of the permissible torque is compared with the required vehicle braking torque, wherein the difference indicates the required friction braking torque to be sent to the friction braking system 130.

[0069] At step 304, in order to make the most efficient use of the motor brake 122, the control system 110 is arranged to determine another permissible torque. It is anticipated that the power system 120 will move toward a threshold of the gap region in order to leave the gap region, and therefore the other permissible torque will generally be greater than the permissible torque determined at step 204.

[0070] At step 305, the control system 110 outputs the determined additional permissible torque to the electric motor brake 122. It will be understood that the control system 110 will repeatedly determine the additional permissible torque for the electric motor brake 122 until the vehicle braking system 101, and in particular the powertrain 120, leaves the clearance region.

[0071] This process is in Figure 4 The diagram shows an example of the variation of the required vehicle braking torque 401, the permissible torque 402, and the friction braking torque 403 with time. Specifically, it can be seen that the required vehicle braking torque 401 increases according to the deceleration request 103 from the driver input device 102. The permissible torque for the electric motor brake 122 lags behind the required vehicle braking torque 401, depending on the instantaneous torque capability of the electric motor brake 122. The remaining portion of the required vehicle braking torque 401 is taken into account by the friction braking torque 403 of the friction brake 134.

[0072] What will be understood is that, although Figure 4 The diagram shows a portion of the allowable torque for the electric motor brake 122 increasing linearly; however, the allowable torque can vary non-linearly, for example parabolically, and can be observed as a step change in the allowable torque. This step change can be monotonic or it can increase over time to most effectively utilize the regenerative braking of the vehicle 10.

[0073] In some cases, it may be necessary to limit or cap another permissible torque. The control system 110 is arranged to receive a signal indicating the utilization rate of the permissible torque for the motor brake 122. If the utilization rate is below a predetermined threshold, an increase in the permissible torque (i.e., another permissible torque) can be capped. In this way, the permissible torque can remain substantially constant until the utilization rate reaches the predetermined threshold.

[0074] exist Figure 5An example is shown where the utilized torque 504 of the electric motor brake 122 is less than the permissible torque 502. In other words, the permissible torque 502 is not being fully utilized. The permissible torque 502 can continue to increase relative to the utilized torque 504 when the required vehicle braking torque 501 is met. This large difference between the permissible torque 502 and the utilized torque 504 could, for example, result in a large step in the requested torque from the electric motor brake 122 in the event of a sudden increase in the required vehicle braking torque 501, potentially leading to shunting and slippage.

[0075] In the event of underutilization of the allowable torque 502, the control system 110 is arranged to limit the allowable torque 502, as indicated by the platform area 502a. In this way, another allowable torque equals the previous allowable torque. Therefore, the underutilization of the allowable torque remains at or below the maximum utilization value. A minimum utilization rate can be set below which the allowable torque 502 is prevented from increasing; for example, the minimum utilization rate can be set to greater than or equal to 90%, or greater than or equal to 80%.

[0076] Although the above examples relate to a single powertrain 120 and friction braking system 130 of vehicle braking system 101, it will be understood that vehicle 10 may have multiple powertrains 120a, 120b and multiple friction braking systems 130a, 130b, each controlled by a separate control system 110, such as... Figure 6 As illustrated in the diagram, each of the individual powertrains 120a, 120b and friction braking systems 130a, 130b can control individual wheels and axles 140a, 140b. For example, a first pair of wheels associated with the first front axle 140a of vehicle 10 can be controlled by the first powertrain 120a and the first friction braking system 130a, and a second pair of wheels associated with the second rear axle 140b of vehicle 10 can be controlled by the second powertrain 120b and the second friction braking system 130b.

[0077] In this example, the control system 110 determines the distribution of the required vehicle braking torque among the corresponding powertrains 120a, 120b and friction braking systems 130a, 130b associated with each axle 140. Each powertrain 120a, 120b includes corresponding electric motor brakes 122a, 122b and drivetrains 124a, 124b, and each friction braking system 130a, 130b includes corresponding brake actuators 132a, 132b and friction brakes 134a, 134b. Figure 7 As illustrated in the figure, the method is the same as except that step 202 is replaced by step 208. Figure 3 The diagrams shown are basically the same.

[0078] At step 208, the control system 110 is arranged to determine the distribution of the required vehicle braking torque between a first set of motor brakes 122a associated with the first axle 140a of the vehicle 10 and a second set of motor brakes 122b associated with the second axle 140b of the vehicle 10. It will be understood that each set of motor brakes 122a, 122b may include one or more motor brakes 122a, 122b. Similarly, the control system 110 is arranged to determine the distribution of the required vehicle braking torque between a first set of friction brakes 134a associated with the first axle 140a of the vehicle 10 and a second set of friction brakes 134b associated with the second axle 140b of the vehicle 10.

[0079] At steps 203a and 203b, the control system 110 is arranged to receive signals indicating the available torque for each set of corresponding motor brakes 122a, 122b.

[0080] At steps 204a and 204b, the control system 110 is arranged to determine the permissible torque for the respective motor brakes 122a and 122b.

[0081] At steps 205a and 205b, the control system 110 outputs the determined permissible torque to the corresponding motor brakes 122a and 122b.

[0082] At steps 304a and 304b, the control system 110 is arranged to determine another permissible torque for each of the respective motor brakes 122a, 122b.

[0083] At steps 305a and 305b, the control system 110 outputs the determined additional permissible torque to the corresponding motor brake 122.

[0084] The required vehicle braking torque distribution between the corresponding powertrain 120a, 120b and the friction braking system 130a, 130b can be determined based on the instantaneous torque capability of each motor brake 122a, 122b. For example, one motor brake 122a, 122b can compensate for the performance of the other motor brake 122a, 122b.

[0085] It will be understood that various changes and modifications can be made to the invention without departing from the scope of this application.

Claims

1. A control system for controlling a braking system of a vehicle having a motor arranged to function as an electric motor brake of the vehicle, the control system (110) comprising one or more processors configured collectively to: Receive a signal indicating a vehicle braking request; Receive a signal indicating the available torque of the motor brake; Determine the permissible torque for the motor brake that is less than or equal to the available torque; and The output represents a determined permissible torque signal representing the determined permissible torque to be applied by the motor brake.

2. The control system according to claim 1, wherein, The one or more processors are also configured to repeatedly determine the allowable torque to gradually increase the allowable torque.

3. The control system according to claim 1 or 2, wherein, The one or more processors are further configured to: Receive the permitted torque signal; Based on the difference between the available torque and the permissible torque signal, the available torque that maintains or reduces the difference is repeatedly determined; and Output the determined available torque signal.

4. The control system according to claim 2 or 3, wherein, The one or more processors are jointly configured to repeatedly determine the allowable torque for the motor brake until the braking system leaves the gap region; and output the available torque to the motor brake.

5. The control system according to any of the preceding claims, wherein, The one or more processors are configured together to: Determine the required vehicle braking torque to satisfy the vehicle braking request; Determine the difference between the required vehicle braking torque and the determined permissible torque; and Based on this difference, a signal indicating the required friction braking torque is output to the friction braking controller.

6. The control system according to any of the preceding claims, wherein, The gap region is defined as the torque value of the motor brake within a non-zero tolerance band near zero torque.

7. The control system according to any of the preceding claims, wherein, The one or more processors are configured together to: Determine the required vehicle braking torque to satisfy the vehicle braking request; The distribution of the required vehicle braking torque among one or more motor brakes in a first group associated with the first axle of the vehicle and one or more motor brakes in a second group associated with the second axle of the vehicle is determined, wherein the distribution of the required vehicle braking torque to each motor brake is determined based on the corresponding permissible torque for each motor brake; and The determined permissible torque is output to the motor brake or each motor brake.

8. A braking system, the braking system comprising: The control system according to claims 1 to 7; At least one friction brake; And at least one motor brake.

9. A vehicle comprising the braking system according to claim 8.

10. A method for controlling a vehicle's braking system when the electric motor brake of the vehicle's braking system is in a clearance region, the method comprising: Receive a signal indicating a vehicle braking request; Receive a signal indicating the available braking torque for the motor brake; Determine the permissible torque for the motor brake, wherein the permissible torque is less than or equal to the available torque; as well as The determined permissible torque is output to the motor brake.

11. The method for controlling a vehicle braking system according to claim 10, the method further comprising: Repeatedly determine the increased allowable torque that is less than or equal to the available torque; as well as The determined permissible torque is output to the motor brake.

12. The method for controlling a vehicle braking system according to claim 10 or 11, the method further comprising: Based on the difference between the available torque and the permissible torque Repeatedly determine the available torque to maintain or reduce the difference; as well as Output the determined available torque signal.

13. A computer-readable instruction, which, when executed by a computer, is arranged to perform the method according to any one of claims 10 to 12.

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