Electronic limited slip differential control system

Abstract

An electronic limited slip differential control system is provided. An eLSD control system includes: an eLSD configured to adjust a torque of an axle to an axle of a vehicle; a preemptive plane coordinator module configured to determine a target of eLSD clutch torque and generate a first clutch torque request based on the target; a direct yaw feedback control module configured to track a target yaw velocity of the vehicle, determine a yaw velocity error, and generate a second clutch torque request to reduce the yaw velocity error; a wheel stability control module configured to generate a third clutch torque request to minimize at least one of i) slip between wheels of the axle and ii) slip on one of the wheels experiencing higher traction; and a core arbitration clutch response module configured to control an eLSD clutch torque of the eLSD based on the first clutch torque request, the second clutch torque request, and the third clutch torque request.

Description

Technical Field

[0001] The information provided in this section is for the purpose of generally presenting the background of the present disclosure. To the extent described in this section, the work of the presently named inventors, and aspects that may otherwise not qualify as prior art at the time of filing, are neither explicitly nor implicitly admitted to be prior art to the present disclosure.

[0002] The present disclosure relates to an electronic limited slip differential (eLSD). Background Art

[0003] A vehicle may include one or more axles having one or more eLSDs. The eLSD determines the amount of torque to be provided to each drive wheel of the axle and provides the determined amount of torque to the drive wheels to improve vehicle stability. The amount of torque may be provided to adjust the amount of slip at each wheel and / or to adjust the amount of slip in a smooth and measured manner. The eLSD maintains a safe level of traction by adjusting the level of torque to each wheel of the axle, thereby improving handling on various surfaces and in various operating conditions. Summary of the invention

[0004] An electronic limited slip differential (eLSD) control system is provided and includes: an eLSD configured to regulate torque to an axle of an axle of a vehicle; a preemptive plane coordinator module configured to determine a target for an eLSD clutch torque and generate a first clutch torque request based on the target; a direct yaw feedback control module configured to track a target yaw rate of the vehicle, determine a yaw rate error, and generate a second clutch torque request to reduce the yaw rate error; a wheel stability control module configured to generate a third clutch torque request to minimize at least one of i) slip between wheels of the axle and ii) slip on one of the wheels experiencing higher traction; and a core arbitration clutch response module configured to control the eLSD clutch torque of the eLSD based on the first clutch torque request, the second clutch torque request, and the third clutch torque request.

[0005] In other features, the preemptive plane coordinator module is configured to determine a longitudinal target, a yaw moment transient target, and a yaw moment steady-state target, and generate the first clutch torque request based on the longitudinal target, the yaw moment transient target, and the yaw moment steady-state target.

[0006] In other features, the preemptive plane coordinator module is configured to determine a traction limiting target and generate the first clutch torque request based on the traction limiting target. The target includes the traction limiting target.

[0007] In other features, the preemptive plane coordinator module is configured to determine the longitudinal target based on wheel speed, wheel acceleration, vehicle suspension speed, vehicle suspension acceleration, and vehicle ride height.

[0008] In other features, the preemptive plane coordinator module is configured to determine the longitudinal target as a baseline target that is a function of the torque request for the axle and a vehicle speed.

[0009] In other features, the preemptive plane coordinator module is configured to determine the longitudinal target based on a steering angle gain and a tire temperature gain.

[0010] In other features, the preemptive plane coordinator module is configured to determine the yaw moment transient target based on at least one of a yaw acceleration error or a target yaw acceleration of the vehicle.

[0011] In other features, the preemptive plane coordinator module is configured to determine a yaw moment steady-state target to relate a transfer function between a steering angle and a yaw moment of the vehicle.

[0012] In other features, the preemptive plane coordinator module is configured to select a maximum of the longitudinal target, the yaw moment transient target, and the yaw moment steady-state target as the first clutch torque request.

[0013] In other features, the eLSD control system further includes a power jump module configured to detect a power jump event and generate a fourth clutch torque request to minimize a duration of the power jump event. The core arbitration clutch response module is configured to control an eLSD clutch torque of the eLSD based on the fourth clutch torque request.

[0014] In other features, the core arbitrated clutch response module is configured to prioritize the fourth clutch torque request over the first clutch torque request, the second clutch torque request, and the third clutch torque request.

[0015] In other features, the eLSD control system further includes a clutch temperature module configured to generate a scalar value based on a temperature of a clutch of the eLSD. The core arbitration clutch response module includes: a first multiplier configured to multiply the scalar value by a first clutch torque request to provide a first product value; a second multiplier configured to multiply the first product value by a fourth clutch torque request to generate a second product value; a first adder configured to sum the second clutch torque request and the third clutch torque request to provide a sum value; and a second adder configured to sum the second product value and the sum value to generate a command to control the eLSD clutch torque of the eLSD.

[0016] In other features, a method of controlling an electronic limited slip differential (eLSD) of a vehicle is provided. The method includes: determining a target for an eLSD clutch torque and generating a first clutch torque request based on the target; tracking a target yaw rate of the vehicle; determining a yaw rate error; generating a second clutch torque request to reduce the yaw rate error; generating a third clutch torque request to minimize at least one of i) slip between wheels of an axle of the vehicle and ii) slip on a first wheel experiencing higher traction; and controlling the eLSD clutch torque of the eLSD based on the first clutch torque request, the second clutch torque request, and the third clutch torque request.

[0017] In other features, determining the target includes: calculating an amount of wheel torque spillover of a second wheel experiencing a lower amount of traction; calculating an initial amount of wheel torque at a first wheel based on the wheel torque spillover; calculating a maximum coupling torque of a clutch of the eLSD; calculating a maximum torque of the first wheel based on the maximum coupling torque; and calculating a first clutch torque request based on the initial amount of wheel torque and the maximum torque of the first wheel.

[0018] In other features, the method also includes: determining whether the initial wheel torque amount is greater than the maximum torque of the first wheel; when the initial wheel torque amount is greater than the maximum torque of the first wheel, calculating the first clutch torque request based on the overflow torque of the first wheel, wherein the overflow torque of the first wheel is greater than 0; and calculating the first clutch torque request based on the minimum value of the initial wheel torque amount and the maximum torque of the first wheel.

[0019] In other features, the method further includes tracking a lateral motion error based on a yaw rate error and a lateral velocity of the vehicle; and calculating a second clutch torque request based on the lateral motion error.

[0020] In other features, the method further includes: determining whether there is a slip difference between the wheels; determining whether the first wheel is experiencing excessive slip; in response to the existence of a slip difference between the wheels and in response to the first wheel experiencing excessive slip, activating eLSD slip control and determining a third clutch torque request based on at least one of a change in slip error and a slip error in the first wheel; and setting the third clutch torque request equal to zero when there is no slip difference between the wheels and when the first wheel is not experiencing excessive slip.

[0021] In other features, the method further includes determining a longitudinal target, a yaw moment transient target, and a yaw moment steady-state target; and generating a first clutch torque request based on the longitudinal target, the yaw moment transient target, and the yaw moment steady-state target.

[0022] In other features, the method further includes determining a traction limit target and generating the first clutch torque request based on the traction limit target, wherein the target includes the traction limit target.

[0023] In other features, the method further includes detecting a power jump event and generating a fourth clutch torque request to minimize a duration of the power jump event; and controlling an eLSD clutch torque of the eLSD based on the fourth clutch torque request.

[0024] The following solutions are disclosed:

[0025] 1. An electronic limited slip differential (eLSD) control system, comprising:

[0026] an eLSD configured to regulate torque to a plurality of axles of a vehicle;

[0027] a preemptive plane coordinator module configured to determine a plurality of targets for eLSD clutch torques and generate a first clutch torque request based on the plurality of targets;

[0028] a direct yaw feedback control module configured to track a target yaw rate of the vehicle, determine a yaw rate error, and generate a second clutch torque request to reduce the yaw rate error;

[0029] a wheel stability control module configured to generate a third clutch torque request to minimize at least one of i) slip between wheels of the axle and ii) slip at one of the wheels experiencing higher traction; and

[0030] A core arbitrated clutch response module is configured to control an eLSD clutch torque of the eLSD based on the first clutch torque request, the second clutch torque request, and the third clutch torque request.

[0031] 2. The eLSD control system according to Scheme 1, wherein the preemptive plane coordinator module is configured to: determine a longitudinal target, a yaw moment transient target, and a yaw moment steady-state target, and generate a first clutch torque request based on the longitudinal target, the yaw moment transient target, and the yaw moment steady-state target.

[0032] 3. The eLSD control system according to claim 2, wherein:

[0033] The preemptive plane coordinator module is configured to determine a traction limiting target and generate a first clutch torque request based on the traction limiting target; and

[0034] The plurality of objectives includes a traction limiting objective.

[0035] 4. The eLSD control system of claim 2, wherein the preemptive plane coordinator module is configured to determine the longitudinal target based on wheel speed, wheel acceleration, vehicle suspension speed, vehicle suspension acceleration, and vehicle ride height.

[0036] 5. The eLSD control system of claim 2, wherein the preemptive plane coordinator module is configured to determine the longitudinal target as a baseline target, wherein the baseline target is a function of the torque request for the axle and the vehicle speed.

[0037] 6. The eLSD control system according to claim 2, wherein the preemptive plane coordinator module is configured to determine the longitudinal target based on a steering angle gain and a tire temperature gain.

[0038] 7. The eLSD control system according to claim 2, wherein the preemptive plane coordinator module is configured to determine the yaw moment transient target based on at least one of a yaw acceleration error or a target yaw acceleration of the vehicle.

[0039] 8. According to the eLSD control system of scheme 2, the preemptive plane coordinator module is configured to determine the yaw moment steady-state target to associate the transfer function between the steering angle and the yaw moment of the vehicle.

[0040] 9. The eLSD control system according to claim 2, wherein the preemptive plane coordinator module is configured to select a maximum value among the longitudinal target, the yaw moment transient target and the yaw moment steady-state target as the first clutch torque request.

[0041] 10. The eLSD control system of claim 1, further comprising a power jump module configured to detect a power jump event and generate a fourth clutch torque request to minimize a duration of the power jump event,

[0042] The core arbitrated clutch response module is configured to control an eLSD clutch torque of the eLSD based on a fourth clutch torque request.

[0043] 11. The eLSD control system of claim 10, wherein the core arbitrated clutch response module is configured to prioritize the fourth clutch torque request over the first clutch torque request, the second clutch torque request, and the third clutch torque request.

[0044] 12. The eLSD control system of claim 11, further comprising a clutch temperature module configured to generate a scalar value based on a temperature of a clutch of the eLSD,

[0045] The core arbitration clutch response module includes:

[0046] a first multiplier configured to multiply the scalar value by the first clutch torque request to provide a first product value;

[0047] a second multiplier configured to multiply the first product value by the fourth clutch torque request to generate a second product value;

[0048] a first summer configured to sum the second clutch torque request and the third clutch torque request to provide a summed value; and

[0049] A second adder is configured to sum the second product value and the sum value to generate a command for controlling an eLSD clutch torque of the eLSD.

[0050] 13. A method of controlling an electronic limited slip differential (eLSD) of a vehicle, the method comprising:

[0051] determining a plurality of targets for eLSD clutch torques and generating a first clutch torque request based on the plurality of targets;

[0052] Tracking the target yaw rate of the vehicle;

[0053] Determine yaw rate error;

[0054] generating a second clutch torque request to reduce a yaw rate error;

[0055] generating a third clutch torque request to minimize at least one of i) slip between wheels of the vehicle axle and ii) slip at a first wheel experiencing higher traction; and

[0056] An eLSD clutch torque of the eLSD is controlled based on the first clutch torque request, the second clutch torque request, and the third clutch torque request.

[0057] 14. The method of claim 13, wherein determining the plurality of targets comprises:

[0058] calculating an amount of wheel torque spillover for a second wheel experiencing a lower amount of traction;

[0059] calculating an initial wheel torque amount at the first wheel based on the wheel torque spill amount;

[0060] Calculate the maximum coupling torque of the clutch of the eLSD;

[0061] calculating a maximum torque of the first wheel based on the maximum coupling torque; and

[0062] A first clutch torque request is calculated based on an initial wheel torque amount and a maximum torque at the first wheel.

[0063] 15. The method according to claim 14, further comprising:

[0064] determining whether the initial wheel torque amount is greater than the maximum torque of the first wheel;

[0065] When the initial wheel torque amount is greater than the maximum torque of the first wheel, calculating the first clutch torque request based on a spillover torque of the first wheel, wherein the spillover torque of the first wheel is greater than 0; and

[0066] The first clutch torque request is calculated based on a minimum of an initial wheel torque amount and a maximum torque at the first wheel.

[0067] 16. The method according to claim 13, further comprising:

[0068] Tracking a lateral motion error based on a yaw rate error and a lateral velocity of the vehicle; and

[0069] A second clutch torque request is calculated based on the lateral motion error.

[0070] 17. The method according to claim 13, further comprising:

[0071] Determine if there is a slip difference between the wheels;

[0072] determining whether the first wheel is experiencing excessive slip;

[0073] In response to a slip difference between the wheels and in response to the first wheel experiencing excessive slip, activating eLSD slip control and determining a third clutch torque request based on at least one of a change in slip error and a slip error in the first wheel; and

[0074] The third clutch torque request is set equal to zero when there is no slip differential between the wheels and when the first wheel is not experiencing excessive slip.

[0075] 18. The method according to claim 13, further comprising:

[0076] determining a longitudinal target, a yaw moment transient target, and a yaw moment steady-state target; and

[0077] A first clutch torque request is generated based on the longitudinal target, the yaw moment transient target, and the yaw moment steady-state target.

[0078] 19. The method of claim 18 further comprising determining a traction limit target and generating the first clutch torque request based on the traction limit target, wherein the plurality of targets includes the traction limit target.

[0079] 20. The method according to claim 18, further comprising:

[0080] detecting a power jump event and generating a fourth clutch torque request to minimize a duration of the power jump event; and

[0081] An eLSD clutch torque of the eLSD is controlled based on the fourth clutch torque request.

[0082] Further areas of applicability of the present disclosure will become apparent from the detailed description, claims and drawings.The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] The present disclosure will become more fully understood from the detailed description and accompanying drawings, in which:

[0084] Figure 1 is a functional block diagram of a vehicle including an example eLSD control system according to the present disclosure, the vehicle having a vehicle control module having a power jump module, a model-based preemptive plane coordinator (MbPPC) module, a direct yaw feedback control (DYFC) module, and a wheel stability control (WSC) module;

[0085] Figure 2 is a functional block diagram of an example vehicle including a first torque source and a second torque source according to the present disclosure, having an eLSD controlled via a vehicle control module;

[0086] Figure 3 is a functional block diagram of another example of a vehicle including multiple torque sources and an eLSD controlled via a vehicle control module according to the present disclosure;

[0087] Figure 4 is a graph including different example driving conditions suitable for use with the eLSD control system disclosed herein;

[0088] Figure 5 According to the present disclosure Figure 1 Functional block diagram of the eLSD control system;

[0089] Figure 6 According to the present disclosure Figure 1 and Figure 5 Functional block diagram of the MbPPC module;

[0090] Figure 7 is a graph showing the lateral forces experienced by the front and rear wheels of a vehicle;

[0091] Figure 8 An example traction limit target method according to the present disclosure is shown;

[0092] Fig. 9 An example DYFC method according to the present disclosure is shown; and

[0093] Fig.10 An example WSC method according to the present disclosure is shown.

[0094] In the drawings, reference numerals may be repeated to identify similar and / or identical elements. DETAILED DESCRIPTION

[0095] Controlling a vehicle with multiple objectives, such as balancing body stability and wheel stability, presents significant challenges due to the interaction between the vehicle and the road and the inherent nonlinear dynamics in vehicle behavior. This complexity is further highlighted by the potential presence of conflicting control commands that simultaneously resolve different control requirements. This is especially true in high-performance vehicles.

[0096] The examples set forth herein include an eLSD control system that ensures vehicle and wheel stability. Such vehicle and wheel stability is provided by controlling the state of one or more eLSDs during high-performance driving conditions. The eLSD control system includes seamless integration and operation of four sub-control modules to provide a control architecture and corresponding methods that mitigate conflicting control commands and coordinate various control requirements. The control architecture and methods control one or more eLSDs to significantly enhance vehicle body control and wheel stability control.

[0097] The control architecture includes the integration of four sub-control modules, namely, a power jump module, an MbPPC module, a DYFC module, and a WSC module. This control structure provides precise torque distribution to the drive wheels to improve overall vehicle stability. The sub-control modules (or sub-controllers) can be merged into a single vehicle control module (or controller) with prioritization capabilities based on a disclosed arbitration process. As an example, a power jump event can be given the highest priority relative to other performance events, allowing a quick and effective response to the power jump event. A power jump event refers to an event when a vehicle accelerates too quickly on, for example, a rough surface and the vehicle wheels jump at a high frequency while accelerating.

[0098] The MbPPC module establishes a baseline target level for the eLSD clutch torque. For the rear axle of a vehicle with an eLSD, this baseline target level for the eLSD clutch torque can be determined when the authority of the DYFC module is reduced and when the wheels of the axle experiencing a higher level of traction (e.g., the outer rear wheels of the rear axle during a turn) experience slip. The WSC module is configured to influence the MbPPC module to ultimately determine the final eLSD clutch torque arbitration amount based on the outputs of three sub-control modules (i.e., the outputs of the MbPPC module, the DYFC module, and the WSC module). These outputs can be combined as described below and used to provide a final eLSD clutch torque arbitration amount. Through the integration of the sub-control modules, the disclosed control method provides precise torque distribution and prioritizes key events.

[0099] The examples disclosed herein enhance both body control and slip control. The control architecture systematically provides eLSD clutch torque to improve overall vehicle stability. These examples provide a hybrid strategy that combines preemptive and reactive control algorithms to effectively arbitrate different torque requests and establish real-time priorities for control targets. These examples provide wheel and body control allocation through precise coordination between sub-control modules to determine the final eLSD clutch torque and eLSD clutch torque regulation. This coordination is effective and includes gain scheduling and real-time determination of the slip target for each wheel of the vehicle. Gain scheduling can refer to the output torque amount of a torque source (e.g., an internal combustion engine, one or more electric motors, etc.).

[0100] Figure 1 A vehicle 100 including an example eLSD control system 102 is shown, the vehicle 100 having a vehicle control module 104 having a power jump module 105, an MbPPC module 106, a DYFC module 107, and a WSC module 108. The power jump module 105 is configured to minimize wheel jump due to a power jump event. The MbPPC module 106 establishes a baseline eLSD clutch torque target, including calculating longitudinal, transient, steady-state, and traction limiting targets. These targets are determined to provide an eLSD clutch torque arbitration baseline within an integrated overall control framework. The DYFC module 107 controls the yaw rate and the sideslip rate. The DYFC module implements a feedback control process to control vehicle states, including the yaw rate and the sideslip rate. The MbPPC module 106 and the DYFC module 107 enhance overall vehicle stability by accurately distributing torque to the wheels of the corresponding axles.

[0101] The WSC module 108 controls wheel stability and minimizes slip between the left and right wheels of the axle. The WSC module 108 is also configured to minimize slip in a wheel with high (or higher) traction (or friction between the wheel tire and the road surface). This wheel is called a high mu wheel. High mu refers to a road surface with a high associated friction level and therefore a high tire traction force, such as when driving on a dry asphalt road. Medium mu refers to a road surface with a medium associated friction level and therefore a medium tire traction force, such as when driving on a gravel or wet road. Low mu refers to a road surface with a low associated friction level and therefore a low tire traction force, such as when driving on an ice or snow covered road. The WSC module 108 can also affect the output of the DYFC module. The WSC module 108 coordinates vehicle control by implementing appropriate gain scheduling and determining the slip target for each wheel.

[0102] The vehicle control module 104 determines the final arbitrated eLSD clutch torque based on the result of combining the outputs of the power jump module 105, the MbPPC module 106, the DYFC module 107, and the WSC module 108. When controlling the eLSD clutch torque, the vehicle control module 104 prioritizes the power jump event over other events that warrant a change in the eLSD clutch torque. The operation of the modules 104-108 is further described below.

[0103] The vehicle 100 also includes sensors 110, memory 112, an accelerator pedal actuator 114, a steering system 116, and a propulsion system 118. The sensors 110 may include wheel speed sensors 120, wheel acceleration sensors 121, suspension acceleration sensors 122, vehicle speed sensors 123, yaw rate sensors 124, inertial measurement units (IMUs) 125, suspension speed sensors 126, ride height sensors 127, acceleration sensors (e.g., longitudinal and lateral acceleration sensors) 128, and other sensors 130 (e.g., eLSD clutch temperature sensors). The memory 112 may store sensor data 132, algorithms 134, applications 136, parameters 138, etc. The sensor data 132 may include data collected from the sensors 110 and / or other sensors, such as an accelerator position sensor 140 of the accelerator pedal actuator 114 and a steering angle sensor 142 of the steering system 116. The accelerator pedal actuator 114 and the accelerator position sensor 140 and / or other devices mentioned herein may be connected to the vehicle control module 104 via a controller area network (CAN) or other network bus 143. Algorithms 134 include the algorithms implemented by modules 104-108 mentioned herein. Applications 136 may include modules 105-108 and / or other applications.

[0104] The propulsion system 118 may include one or more torque sources, such as one or more motors and / or one or more engines (eg, internal combustion engines). Figure 1 In the example shown, the vehicle 100 includes an engine 150 and one or more motors 152. The torque sources are independently controlled. The propulsion system 118 includes a motor control system 154, which includes one or more motors 152 and a motor control module 156, which can control the operation of the one or more motors 152 based on signals from the vehicle control module 104.

[0105] The vehicle control module 104 may also include a mode selection module 160 and / or a parameter adjustment module 162. The modules 105-108 and 160 may select different operating modes.

[0106] Figure 2A vehicle 200 is shown including a vehicle control module 202 that controls operation of a first torque source 204 , a second torque source 206 , and an eLSD 208 . Figure 2 A vehicle 200 is shown that includes independently controlled torque sources controlled by a vehicle control module 202. Each of the torque sources 204, 206 may be implemented as an engine or a motor. The vehicle control module 202 may be coupled to a Figure 1 The vehicle control module 104 of the embodiment is similarly configured and operated. The vehicle control module 202 controls the operation of the torque sources 204, 206 to control the amount of torque received by one or more front axles (or shafts) 210 and one or more rear axles (or shafts) 212, and thus controls the amount of torque to the left front wheel and the right front wheel 214 and the left rear wheel and the right rear wheel 216. The vehicle control module 202 controls the distribution of torque to the left rear wheel and the right rear wheel 216 by controlling the clutch torque of the eLSD 208, which adjusts the pressure of the clutch 220 of the eLSD 208.

[0107] Figure 3 A vehicle 300 is shown, which includes a vehicle control module 302, torque sources 304, 306 and corresponding eLSDs 308, 309, which are controlled by the vehicle control module 302. The eLSDs 308, 309 include respective clutches 310, 311. The vehicle control module 302 may be coupled to a Figure 1 The vehicle control module 104 is similarly configured and operated. The vehicle control module 302 controls the operation of the torque sources to control the amount of torque received by one or more front axles 314 and one or more rear axles 316 and, therefore, the amount of torque to the front wheels 318 and rear wheels 320.

[0108] Figure 4 Shown includes applicable Figure 1 Graph 400 of different driving conditions of the eLSD control system 102. The eLSD control system 102 may be applied to lane changes 402, acceleration and braking along a linear path 404, traction forces of the wheels of a disengaged axle while traveling along a linear path 406, and traveling along a linear path and in a steady state 408. A disengaged amount of traction (or disengaged mu event) may occur when a first wheel of an axle is on a different surface than a second wheel of the axle. For example, when the first wheel is on an asphalt road and the second wheel is on a gravel road. As another example, when the first wheel is on an icy surface and the second wheel is on an asphalt road.

[0109] Driving conditions also include when the vehicle is entering a corner (or turn) and braking (labeled 410), when the vehicle is moving near a corner (or turn) and the vehicle's throttle is depressed (labeled 412), when the vehicle is in the middle of a corner (or turn) and the throttle is closed (labeled 414), when the vehicle is in the middle of a corner (or turn) and the throttle is open (labeled 416), when the vehicle is leaving a corner (or turn) (labeled 418), when the vehicle is leaving a corner (or turn) and experiencing a disengaged mu event (labeled 420), and when the vehicle is experiencing a drift condition (labeled 422). An example of driving condition 420 is when one wheel is on a curb and the other wheel of the same axle is not on the curb. During events 412, 414, 416, the disclosed control can reduce understeer when the vehicle is turning by opening the eLSD clutch to allow the wheels to spin. During event 420 , the disclosed control may determine the appropriate amount of left and right coupling to provide inboard and outboard wheel stability and balance.

[0110] Figure 5 Shows Figure 1 The eLSD control system 102 includes modules 105, 106, 107, 108, and also includes a clutch temperature module 500 and a core arbitration clutch response module 502. The eLSD control system 102 is applicable to each eLSD included on the corresponding vehicle. If more than one eLSD is included, a reference can be performed for each eLSD. Figure 5-10 The vehicle control module 104 receives outputs from the sensors 110. Each of the modules 105-108 and 500 receives at least some of these outputs as inputs, and may receive other inputs as mentioned below.

[0111] Each of the modules 105-108 may receive inputs including i) an estimate of the propulsion torque of the torque source, and ii) an estimate of the braking torque at each wheel of the corresponding front or rear axle. These inputs may be estimated by the vehicle control module 104. The power jump module 105 may receive outputs from the wheel speed sensor 120, the wheel acceleration sensor 121, the suspension speed sensor 126, the suspension acceleration sensor 122, and the ride height sensor 127. Based on these outputs and the inputs, the power jump module 105 generates an eLSD clutch torque output (or clutch torque request, which may be in Newton meters (Nm)). The power jump module 105 has arbitration priority.

[0112] The MbPPC module 106 may receive outputs from the wheel speed sensor 120, the steering angle sensor 142, and the IMU 125. The MbPPC module 106 generates an eLSD clutch torque output (or clutch torque request, which may be in Nm) based on these outputs and the inputs. The MbPPC module 106 provides longitudinal, steady-state, and transient targets for the eLSD clutch response, as described below with reference to Figure 6 Further described.

[0113] The DYFC module 107 may receive the outputs of the steering angle sensor 142, the IMU 125, and the vehicle speed sensor 123. The DYFC module 107 generates an eLSD clutch torque output (or a clutch torque request, which may be in Nm) based on these outputs and the inputs. The eLSD clutch torque output may be referred to as an eLSD clutch slip control torque output. The DYFC module 107 tracks the desired (or target) yaw rate and provides an eLSD clutch torque to reduce the yaw rate error. The yaw rate error is the difference between the target yaw rate and the actual yaw rate of the corresponding vehicle.

[0114] The WSC module 108 may receive the outputs of the wheel speed sensors 120. The WSC module 108 generates an eLSD clutch torque output (or clutch torque request, which may be in Nm) based on these outputs and the inputs. The WSC module 108 provides clutch torque to meet two objectives. The clutch torque is provided to i) minimize slip between the left and right wheels of an axle (e.g., a front axle or a rear axle), and ii) minimize slip on the outer and / or high mu wheels. The WSC module 108 minimizes slip in the clutch of the eLSD and gives priority to the high mu wheels to maintain traction at the high mu wheels.

[0115] The clutch temperature module 500 determines the temperature of the clutch of one or more eLSDs. This may be accomplished by an eLSD clutch temperature sensor. The clutch temperature module 500 indicates whether the eLSD clutch is overheated and generates a scalar value based on whether the eLSD clutch is overheated. The scalar value is changed to allow an overheated eLSD clutch to cool down. For example, the scalar value may be decreased to reduce the amount of torque applied to the clutch of the eLSD, thereby allowing an overheated eLSD clutch to cool down.

[0116] The core arbitration clutch response module 502 i) multiplies the outputs of modules 106 and 500 via multiplier 504 to provide a first product value, ii) multiplies the first product value by the output of the power jump module 105 and a constant M via a second multiplier 506 to provide a second product value, iii) adds the outputs of modules 107, 108 via a first adder 508 to provide a first sum value, iv) and adds the second product value and the output of the first adder 508 via a second adder 510 to provide a final eLSD clutch torque command value, which is provided to the eLSD 512. The final eLSD clutch torque command value may be provided to a controller or actuator of the eLSD 512.

[0117] Figure 6 Shows Figure 1 and 5 The MbPPC module 106 may include a longitudinal target torque module 600 , a yaw moment transient target torque module 602 , a yaw moment steady-state target torque module 604 , a traction-limiting target torque module 606 , and a maximum torque determination module 608 .

[0118] The longitudinal target torque module 600 determines a longitudinal baseline target eLSD clutch torque as a function of i) a torque request for a corresponding axle (e.g., a front axle or a rear axle) of a corresponding vehicle and ii) vehicle speed. The longitudinal baseline target eLSD clutch torque can be based on a steering angle gain and a tire temperature gain. The steering angle gain is a function of the front wheel angle and vehicle speed. The tire temperature gain is a function of tire temperature and lateral acceleration. The longitudinal baseline target eLSD clutch torque can be a steady-state preload target eLSD clutch torque for high-speed and highway driving. The longitudinal baseline target eLSD clutch torque provides a minimum amount of eLSD clutch torque to minimize response time when the driver implements dynamic operations (e.g., accelerating the vehicle or turning the vehicle at high speed). The longitudinal baseline target eLSD clutch torque is primarily used in situations where the vehicle is traveling along a linear path.

[0119] The yaw moment transient target torque module 602 determines the yaw moment transient target eLSD clutch torque to tune the vehicle balance during highly transient maneuvers (e.g., lane changes). This is most effective during the initial turn-in when the tires experience delays in generating lateral forces (i.e., slack length). The yaw moment transient target eLSD clutch torque is based on at least one of a yaw acceleration error and a target yaw acceleration. The yaw acceleration error is the difference between the target yaw acceleration and the actual yaw acceleration of the vehicle. For a given vehicle speed, if the steering angle changes rapidly, the vehicle has a tendency to slide. When a rapid change in the steering angle is detected, the yaw moment transient target torque module 602 increases the amount of the eLSD clutch torque to improve vehicle stability and prevent the vehicle from sliding. If the steering angle changes smoothly and does not change too rapidly, the yaw moment transient target torque module 602 does not increase the amount of the eLSD clutch torque. The operation of the yaw moment transient target torque module 602 is particularly suitable for lane changes.

[0120] The yaw dynamics of the vehicle can be expressed by Equation 1, where I z is the yaw inertia, r is the yaw angular velocity, is the yaw rate gradient, l f and l r is the distance from the vehicle's center of gravity to the vehicle's front and rear suspension, F yLE and F yRF are the left and right lateral tire forces on the front axle of the vehicle, F yLR and F yRR are the left and right lateral tire forces at the rear axle of the vehicle, and M z is the yaw moment.

[0121]

[0122] During the initial turn entry, there is a certain delay between the driver turning the steering wheel and the vehicle generating a yaw moment. Therefore, in transient conditions, due to this delay, direct yaw moment (torque vectoring) is used to meet the driver's desire. Therefore, in this condition, Equation 1 can be simplified to provide Equation 2, where, is generated by taking the derivative of the driver's desired yaw rate.

[0123]

[0124] The dynamics of the driver's desired yaw rate (or lateral acceleration) and steering wheel rate (or rate of change of steering wheel angle) are similar and can be expressed by Equation 3, with the derivative expressed by Equation 4, where δ and is the steering wheel angle and its gradient, L is the total distance between the front and rear suspension, and V and is the longitudinal velocity and its gradient. Yaw Torque The transient target eLSD clutch torque may be determined based on the desired yaw rate and / or its derivative.

[0125]

[0126]

[0127] The yaw moment steady state target torque module 604 determines the yaw moment steady state target eLSD clutch torque. The yaw moment steady state target torque module 604 is primarily designed for steady state handling balance of the vehicle during partial or closed throttle conditions, such as when the vehicle is in the middle of a turn and is experiencing the maximum level of lateral acceleration. When the vehicle is in a turn, the yaw moment steady state target torque module 604 balances the vehicle. When the steering angle stops changing and the yaw is in a steady state during the turn, the vehicle control module 104 transitions to providing the output of the yaw moment steady state target torque module 604 and the corresponding yaw moment steady state target eLSD torque. As the vehicle becomes stable and in a steady state, the more eLSD coupling, the more understeer. The steady state target can be provided during the middle of the turn based on the geometry of the turn and the speed of the vehicle through the turn to adjust the amount of understeer. This can be based on a vehicle model. The steady state target is particularly effective during high speed and high acceleration (or high g) turns. The steady state target is related to the transfer function between the steering angle and the external yaw moment of the vehicle. For a given vehicle speed, the output of modules 602 , 604 may be based on how quickly and to what extent the steering angle changes.

[0128] Figure 7 A diagram showing the lateral forces experienced by the front and rear wheels of a vehicle. The lateral dynamics of the vehicle can be expressed by Equations 5 and 6, where β and is the sideslip angle and its gradient.

[0129]

[0130]

[0131] Based on Equations 7-10, the lateral force can be modeled as a linear function of the lateral slip, where C f and C r are the front and rear suspension corner stiffnesses, and α F and α r are the front and rear wheel slip angles.

[0132]

[0133] F yLR / RR =C r α r (8)

[0134]

[0135]

[0136] The linear model in state space form can be defined by Equation 11, where m is the vehicle mass.

[0137]

[0138] The effect of various actuators on the total vehicle yaw rate can be expressed as Equation 12, where δ f and δ r are the front and rear steering wheel angles, and is the steady-state gain of yaw rate with respect to front steering, rear steering and external yaw moment.

[0139]

[0140] Considering that the vehicle is in steady state, the state derivatives can be set to 0 and the steady-state gains can be calculated using Equations 13-15, where is the steady-state gain for sideslip with respect to front steering, rear steering, and external yaw moment, and is used to provide a yaw moment steady-state target eLSD clutch torque.

[0141]

[0142]

[0143]

[0144] The traction limited target torque module 606 determines the traction limited target eLSD clutch torque. The traction limited target torque module 606 is designed to achieve vehicle and wheel stability with the throttle open (e.g., when exiting a turn). The traction limited target is used when the vehicle is exiting a turn and reduces the lap time that the vehicle travels around the track. The algorithm of the traction limited target torque module 606 uses a model-based traction limit estimate that is coupled with redistribution logic to allow for improved traction between the left and right wheels of the axle. The traction limited target torque module 606 adjusts the amount of coupling between the left and right axles of the axle so that the wheels with less traction (or grip) do not spin. The amount of eLSD clutch torque is limited to limit the amount of torque received at the high mu wheel.

[0145] The maximum torque determination module 608 receives the target eLSD clutch torque outputs from modules 600, 602, 604, 606 and determines which output is the largest. The largest (or maximum) output is provided to Figure 5The core arbitrated clutch response module 502. The maximum output is provided to the multiplier 504. By finding the maximum output, the maximum torque determination module 608 satisfies the goals of the modules 602, 604, 606 and provides a baseline clutch torque response.

[0146] The eLSD feedforward clutch torque provided by the maximum torque determination module 608 establishes the longitudinal target, transient target, and steady-state target as a baseline for the clutch coupling torque response. Torques that provide lateral acceleration and slip control are added to or subtracted from the baseline.

[0147] Figure 8 It shows that Figure 1 and 5 The traction limit target method implemented by the traction limit target torque module 606 of the MbPPC module 106 of -6. At 800, the traction limit target torque module 606 calculates the low mu wheel torque overflow amount Ofl_lo, which may be equal to i) 0.5*T_Axl-TL_Lo, where T_Axl is the total axle torque and TL_Lo is the traction limit of the low mu wheel, or ii) the maximum of CT_Lo and 0, where CT_Lo is the coupling torque of the low mu wheel. At 802, the traction limit target torque module 606 calculates the initial amount of high mu wheel torque Tin_Hi. This may be equal to 0.5*T_Axl+Ofl_Lo.

[0148] At 804, the traction limit target torque module 606 calculates the maximum coupling torque CT_Max. CT_Max may be equal to 0.5*T_Axl+Cal Offset, where Cal Offset is a calibration offset value. At 806, the traction limit target torque module 606 calculates the maximum torque TMax_Hi of the high mu wheel. TMax_Hi may be equal to the minimum of TL_Hi and CT_Max, where TL_Hi is the traction limit of the high mu wheel and CT_Max is the maximum coupling torque.

[0149] At 808, the traction-limited target torque module 606 determines whether the torque request input Tin_Hi of the high mu wheel is greater than the torque request maximum value Tmax_Hi of the high mu wheel. If yes, operation 810 is performed, otherwise operation 812 is performed. If no, the overflow torque Ofl_Hi of the high mu wheel may be equal to 0. At 810, the traction-limited target torque module 606 calculates the overflow torque Ofl_Hi of the high mu wheel. Ofl_Hi may be equal to the maximum value of 0 and the difference between Tin_Hi and TMax_Hi. In an embodiment, Ofl_Hi is multiplied by an overflow calibration ratio.

[0150] At 812, the traction limited target torque module 606 calculates the initial torque request output TOut_Hi for the high mu wheel. TOut_Hi can be equal to the sum of Ofl_Hi and the minimum of Tin_Hi and TMax_Hi. At 814, the traction limited target torque module 606 calculates the clutch torque coupling target CT_Tgt for the eLSD. CT_Tgt can be equal to 2*(TOut_Hi–0.5*T_Axl), where TOut_Hi is the torque request output for the high mu wheel. At 816, the traction limited target torque module 606 sends the clutch torque target to the core arbitration clutch response module 502.

[0151] Fig. 9 The DYFC method is shown. Figure 1 and Figure 5 The DYFC module 107 may perform the following operations. At 900, the DYFC module 107 tracks the lateral motion error, including tracking the yaw rate error and the lateral velocity of the vehicle. At 902, the DYFC module 107 calculates the eLSD clutch torque value to correct the yaw rate error. The eLSD clutch torque value is determined based on the yaw rate error and the lateral velocity.

[0152] In an embodiment, during operations 900 and 902, the DYFC module 107 tracks the yaw rate error (the difference between the desired (or target) yaw rate and the actual vehicle yaw rate) and operates as a proportional derivative (PD) controller and corrects the yaw rate error. The yaw rate error is multiplied by the slip gain, the clutch torque adjustment gain, and the tire temperature gain to determine the torque vectoring yaw rate error target. The eLSD clutch torque value is generated based on the yaw rate error target.

[0153] At 904 , the DYFC module 107 sends the eLSD clutch torque value to the core arbitration clutch response module 502 .

[0154] The described yaw control is provided by the eLSD to simultaneously maintain vehicle yaw rate and stability. This prevents undesired yaw motion when torque bias is implemented in the eLSD.

[0155] Fig.10 The WSC method is shown. Figure 1 and Figure 5The WSC module 108 may perform the following operations. Operations 1000 and 1002 may be performed simultaneously. At 1000, the WSC module 108 determines whether a change in slip has occurred between the wheels of an axle (e.g., a front axle or a rear axle) of the vehicle. If so, operation 1004 is performed, otherwise operation 1006 is performed. At 1002, the WSC module 108 determines whether the high mu wheel is experiencing excessive slip. Excessive slip may be when the slip is positive and greater than a predetermined amount, for example, when greater than 6-7%. If so, operation 1008 is performed, otherwise operation 1006 is performed.

[0156] At 1004, the WSC module 108 activates the eLSD slip control and operates as a proportional integral derivative (PID) controller to determine the eLSD clutch torque for the slip error change. At 1006, the WSC module 108 sets the eLSD slip control clutch torque equal to 0. At 1008, the WSC module 108 activates the eLSD slip control and operates as a PD controller to determine the eLSD clutch torque based on the high mu wheel slip error.

[0157] At 1010, the WSC module 108 sums the results of one or more of the operations 1004, 1006, and 1008 being performed to provide a summed eLSD slip control clutch torque value (or eLSD clutch torque request of the WSC module 108). At 1012, the WSC module 108 sets a limit on the maximum eLSD clutch torque based on the summed eLSD control clutch torque value. At 1014, the WSC module 108 sends the summed eLSD slip control torque value to the core arbitration clutch response module 502.

[0158] The eLSD slip control provides clutch torque to reduce the variation of slip error and high mu slip error. This control provides smoothness between how much clutch coupling is added to mitigate this slip error variation while limiting the additional torque to not sacrifice traction at the high mu wheel. The WSC module 108 monitors the wheel torque limits and maximizes the torque provided to the high mu wheel without causing excessive slip at the high mu wheel. This may be the outside wheel when the vehicle is in a turn. If the high mu wheel is experiencing excessive slip, the WSC module 108 adjusts the gain to reduce the coupled torque to the high mu wheel, thereby reducing the amount of slip.

[0159] The foregoing description is merely illustrative in nature and is by no means intended to limit the present disclosure, its application or use. The broad teachings of the present disclosure can be implemented in various forms. Therefore, although the present disclosure includes specific examples, the true scope of the present disclosure should not be so limited, because after studying the drawings, the specification and the appended claims, other modifications will become apparent. It should be understood that one or more steps in the method can be performed in different orders (or simultaneously) without changing the principles of the present disclosure. In addition, although each embodiment is described above as having certain features, any one or more of those features described with respect to any embodiment of the present disclosure can be implemented in the features of any other embodiment and / or combined with the features of any other embodiment, even if the combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and the replacement of one or more embodiments with each other is still within the scope of the present disclosure.

[0160] Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including "connected," "engaged," "coupled," "adjacent," "next to," "on top of," "above," "below," and "disposed." Unless explicitly described as "direct," when describing the relationship between a first and a second element in the above disclosure, the relationship can be a direct relationship between the first and second elements with no other intervening elements, but can also be an indirect relationship between the first and second elements with one or more intervening elements (spatially or functionally) present. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or, and should not be construed to mean "at least one of A, at least one of B, and at least one of C."

[0161] In a diagram, the direction of the arrow indicated by the arrow generally indicates the flow of information (such as data or instructions) of interest to the diagram. For example, when component A and component B exchange various information, but the information transmitted from component A to component B is relevant to the diagram, the arrow may point from component A to component B. This one-way arrow does not mean that no other information is transmitted from component B to component A. In addition, for information sent from component A to component B, component B may send a request or a receipt confirmation of the information to component A.

[0162] In this application, including the definitions below, the term "module" or the term "controller" may be replaced with the term "circuit". The term "module" may refer to part of or include: an application specific integrated circuit (ASIC); a digital, analog or mixed analog / digital discrete circuit; a digital, analog or mixed analog / digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated or grouped) that executes code; a memory circuit (shared, dedicated or grouped) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system on a chip.

[0163] The module may include one or more interface circuits. In some examples, the interface circuit may include a wired or wireless interface connected to a local area network (LAN), the Internet, a wide area network (WAN), or a combination thereof. The functions of any given module of the present disclosure may be distributed between multiple modules connected by the interface circuit. For example, multiple modules may allow load balancing. In another example, a server (also referred to as a remote or cloud) module may perform some functions on behalf of a client module.

[0164] The term code used above may include software, firmware, and / or microcode, and may refer to programs, routines, functions, classes, data structures, and / or objects. The term shared processor circuit encompasses a single processor circuit that executes some or all code from multiple modules. The term group processor circuit encompasses such a processor circuit, which is combined with additional processor circuits, to execute some or all code from one or more modules. References to multiple processor circuits encompass multiple processor circuits on discrete dies, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above. The term shared memory circuit encompasses a single memory circuit that stores some or all code from multiple modules. The term group memory circuit encompasses such a memory circuit, which is combined with additional memory, to store some or all code from one or more modules.

[0165] The term memory circuit is a subset of the term computer-readable medium. The term computer-readable medium as used herein does not cover transient electrical or electromagnetic signals propagated through a medium (e.g., on a carrier wave); thus, the term computer-readable medium may be considered to be tangible and non-transitory. Non-limiting examples of non-transitory tangible computer-readable media are non-volatile memory circuits (e.g., flash memory circuits, erasable programmable read-only memory circuits, or mask read-only memory circuits), volatile memory circuits (e.g., static random access memory circuits or dynamic random access memory circuits), magnetic storage media (e.g., analog or digital magnetic tape or hard drive), and optical storage media (e.g., CD, DVD, or Blu-ray disc).

[0166] The apparatus and methods described in this application may be implemented in part or in whole by a special-purpose computer, which is created by configuring a general-purpose computer to perform one or more specific functions embodied in a computer program. The functional blocks, flow chart components and other elements described above act as software specifications, which can be translated into computer programs by the routine work of a skilled technician or programmer.

[0167] The computer program includes processor executable instructions stored on at least one non-transitory tangible computer readable medium. The computer program may also include or rely on stored data. The computer program may include a basic input / output system (BIOS) that interacts with the hardware of the special-purpose computer, device drivers that interact with specific devices of the special-purpose computer, one or more operating systems, user applications, background services, background applications, etc.

[0168] A computer program may include: (i) descriptive text to be parsed, such as HTML (Hypertext Markup Language), XML (Extensible Markup Language), or JSON (JavaScript Object Notation); (ii) assembly code; (iii) object code generated by a compiler from source code; (iv) source code executed by an interpreter; (v) source code compiled and executed by a real-time compiler, etc. By way of example only, the source code may be compiled using languages ​​including C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Fortran, Perl, Pascal, Curl, OCaml, HTML5 (Hypertext Markup Language Fifth Revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Visual Lua, MATLAB, SIMULINK, and The grammar of the language is used to write it.

Claims

1. An electronic limited slip differential (eLSD) control system, comprising: an eLSD configured to regulate torque to a plurality of axles of a vehicle; a preemptive plane coordinator module configured to determine a plurality of targets for eLSD clutch torques and generate a first clutch torque request based on the plurality of targets; a direct yaw feedback control module configured to track a target yaw rate of the vehicle, determine a yaw rate error, and generate a second clutch torque request to reduce the yaw rate error; a wheel stability control module configured to generate a third clutch torque request to minimize at least one of i) slip between wheels of the axle and ii) slip on one of the wheels experiencing higher traction; as well as A core arbitrated clutch response module is configured to control an eLSD clutch torque of the eLSD based on the first clutch torque request, the second clutch torque request, and the third clutch torque request.

2. The eLSD control system of claim 1, wherein the preemptive plane coordinator module is configured to: determine a longitudinal target, a yaw moment transient target, and a yaw moment steady-state target, and generate a first clutch torque request based on the longitudinal target, the yaw moment transient target, and the yaw moment steady-state target.

3. The eLSD control system according to claim 2, wherein: The preemptive plane coordinator module is configured to determine a traction limiting target and generate a first clutch torque request based on the traction limiting target; and The plurality of objectives includes a traction limiting objective.

4. The eLSD control system of claim 2, wherein the preemptive plane coordinator module is configured to determine the longitudinal target based on wheel speed, wheel acceleration, vehicle suspension speed, vehicle suspension acceleration, and vehicle ride height. 5 . The eLSD control system of claim 2 , wherein the preemptive plane coordinator module is configured to determine the longitudinal target as a baseline target that is a function of the torque request for the axle and the vehicle speed. 6 . The eLSD control system of claim 2 , wherein the preemptive plane coordinator module is configured to determine the longitudinal target based on a steering angle gain and a tire temperature gain. 7 . The eLSD control system of claim 2 , wherein the preemptive plane coordinator module is configured to determine the yaw moment transient target based on at least one of a yaw acceleration error or a target yaw acceleration of the vehicle.

8. The eLSD control system of claim 2, wherein the preemptive plane coordinator module is configured to determine the yaw moment steady-state target to relate a transfer function between a steering angle and a yaw moment of the vehicle. 9 . The eLSD control system of claim 2 , wherein the preemptive plane coordinator module is configured to select a maximum of the longitudinal target, the yaw moment transient target, and the yaw moment steady-state target as the first clutch torque request.

10. The eLSD control system of claim 1 , further comprising a power jump module configured to detect a power jump event and generate a fourth clutch torque request to minimize a duration of the power jump event, The core arbitrated clutch response module is configured to control an eLSD clutch torque of the eLSD based on a fourth clutch torque request.

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