Vehicle control system for coordinated vehicle dynamics handling balance control using torque management

Abstract

Chassis control system (102) of a vehicle (100, 200), wherein the chassis control system (102) comprises: a first torque source (206) configured to supply torque to a first axle (210) of the vehicle (100, 200); a second torque source (208) configured to deliver torque to a second axle (212) of the vehicle (100, 200) independently of the first torque source (206); and a vehicle control module (104) configured to control the first torque source (206) and the second torque source (208); characterized by the fact that the vehicle control module (104) is configured to control the first torque source (206) and the second torque source (208) based on a wheel torque redistribution threshold, a wheel torque limit of the first axle (210) and / or the second axle (212), and a torque limit of one of the first torque source (206) and the second torque source (208) in order to switch between a torque redistribution mode and a torque limiting control mode, wherein the torque redistribution mode refers to the selective delivery of torque to the first axle (210) by the first torque source (206) and torque to the second axle (212) by the second torque source (208), and the torque limiting control mode refers to the limitation of torque to the first axle (210) and the second axle (212); the vehicle control module (104) is further configured as follows: (i) to increase a torque on the first axle (210) at a first rate and on the second axle (212) at a second rate until the torque on the second axle (212) reaches the wheel torque limit of the second axle (212), and then to increase a torque on the first axle (210) at a third rate and on the second axle (212) at a fourth rate, the third rate being lower than the first rate and the fourth rate being lower than the second rate; or (ii) during operation in torque limiting control mode, limit the torque supplied to the first axis (210) based on a torque limit of the first torque source (206) and refrain from increasing any torque at the second axis (212); or (iii) to determine a lateral acceleration of the vehicle (100, 200), a torque quantity requested by a driver of the vehicle (100, 200), a speed of the vehicle (100, 200) and a road surface condition; to determine an operating limit for the understeer angle versus the understeer speed based on the vehicle's lateral acceleration (100, 200), the amount of torque requested by the vehicle's driver (100, 200), the vehicle's speed (100, 200), and the road surface condition; and to adjust the torque to the first axle (210) and the second axle (212) in order to keep the operation of the vehicle (100, 200) within the operating limits; or (iv) to determine whether a torque requested by a driver is greater than the wheel torque redistribution threshold; to deliver, in response to the fact that the amount of torque requested by a driver is greater than the wheel torque redistribution threshold, an amount of torque equal to a torque limit for the first axle (210), from the second torque source (208) to the second axle (212); and to switch from operating in torque redistribution mode to torque limiting control mode in response to the fact that the amount of torque requested by a driver is not greater than the wheel torque redistribution threshold.

Description

INTRODUCTION

[0001] The present invention relates to a chassis control system according to the preamble of claim 1, as is known essentially from US 2002 / 0105188A1.

[0002] Further details of the state of the art can be found in the documents DE 100 49 567 A1, DE 10 2020 216 118 A1, US 2019 / 0 077 258 A1, CN 1 07 640 062 A, CN 1 08 909 529 A, CN 106 314 204 A and DE 10 2012 201 250 A1.

[0003] Conventional chassis control systems include traction control systems (TCS), electronic stability control systems (ESC), and all-wheel drive systems (AWD). TCS detects wheel slip (or tire slip) and brakes one or more wheels and / or reduces the torque delivered to that wheel or those wheels. ESC detects a loss of steering control and brakes to improve vehicle stability. An AWD system delivers power to all wheels simultaneously or as needed. SUMMARY

[0004] According to the invention, a chassis control system for a vehicle is presented, characterized by the features of claim 1.

[0005] In other features, the vehicle control module is configured to switch from a normal torque-shaping mode to a torque-boosting mode based on a torque amount requested by the vehicle's driver and the wheel torque redistribution threshold. During torque-boosting mode, the vehicle control module simultaneously increases torque on the first and second axles.

[0006] In other features, the vehicle control module is configured to switch from torque redistribution mode to torque limiting control mode when the torque at the second axle reaches the wheel torque limit of the second axle. This involves increasing torque to the first axle at a fifth rate and to the second axle at a sixth rate. The fifth rate is lower than the third rate. The sixth rate is lower than the fourth rate.

[0007] In other features, the vehicle control module is configured to proactively increase torque to the first axle and the second axle based on a torque request from the driver of the vehicle.

[0008] In other features, the vehicle control module is configured to transition from a preventive increase in torque to the first axle at a first rate and to the second axle at a second rate to a torque increase mode, which involves increasing torque to the first axle at a third rate and to the second axle at a fourth rate. The third rate is lower than the first rate. The fourth rate differs from the second rate.

[0009] In further features, the vehicle control module is configured to switch from a torque increase mode to a torque rate reduction mode, the torque rate reduction mode comprising refraining from increasing the torque to the second axle and keeping a torque amount at the second axle below a wheel torque limit of the second axle.

[0010] In other features, the vehicle control module is configured to switch from torque redistribution mode to torque limiting control mode when a torque to the first axle reaches a wheel torque limit for the first axle.

[0011] The vehicle control module is configured with further features: to switch to a feedback wheel slip control mode during the torque limiting control mode, and during the feedback wheel slip control mode, to adjust the torque of the first axle based on the rotational speeds of the wheels of the first axle and the second axle, to allow the wheels of the first axle to slip, to prevent the wheels of the second axle from slipping, and to maintain a torque on the second axle at a level below the wheel torque limit of the second axle.

[0012] In other characteristics, the first axle is a front axle. The second axle is a rear axle. The vehicle control module is configured to relate the operating limit to a front-to-rear wheel slip target curve and to adjust the slip of the first axle and the slip of the second axle based on the front-to-rear wheel slip target.

[0013] In other features, the vehicle control module is configured to provide an increase in the slip amount of the first axle during an oversteer event and then to decrease the slip amount of the first axle in order to bring the vehicle to neutral steering.

[0014] In further features, the vehicle control module is configured, based on the lateral acceleration of the vehicle, the amount of torque requested by the driver of the vehicle, the speed of the vehicle and the road surface condition, to: i) increase the torque to the second axis to a first level, ii) decrease the torque to the second axis from the first level to a second level and iii) then increase the torque to the second axis from the second level to a third level.

[0015] In further features, the vehicle control module is configured to: determine whether the amount of torque delivered to the second axle is greater than a wheel torque limit for the second axle; in response to the fact that the amount of torque delivered to the second axle is greater than a wheel torque limit for the second axle, send excess torque to the first axle via the first torque source, where the excess torque is a difference between a total torque threshold of the first axle and the wheel torque limit of the second axle; and in response to the fact that the amount of torque delivered to the second axle is not greater than a wheel torque limit for the second axle, switch from operating in torque redistribution mode to torque limiting control mode.

[0016] In further features, the vehicle control module is configured to: determine whether the sum of the torque supplied to the first axle and the excess torque is greater than a wheel torque limit of the first axle; distribute the remaining torque between the first axle and the second axle using the first torque source and the second torque source in response to the sum being greater than the wheel torque limit of the first axle; and switch from operating in torque redistribution mode to torque limiting control mode in response to the sum not being greater than the wheel torque limit of the first axle.

[0017] Furthermore, a chassis control procedure is described which includes: determining a vehicle's lateral acceleration, a torque quantity requested by the vehicle's driver, a vehicle speed, and a road surface condition; determining an operating limit based on the vehicle's lateral acceleration, the torque quantity requested by the vehicle's driver, the vehicle speed, and the road surface condition; and controlling a first torque source of a first axle of the vehicle and a second torque source of a second axle of the vehicle to, based on the operating limit and a wheel torque redistribution threshold,to switch between a torque redistribution mode and a torque limiting control mode based on a wheel torque limit of the first axle and / or the second axle and a torque limit of one of the first torque sources and the second torque source, wherein the torque redistribution mode refers to the selective delivery of torque to the first axle by the first torque source and to the second axle by the second torque source, and the torque limiting control mode refers to the limitation of torque to the first axle and the second axle.

[0018] The chassis control procedure also includes the following features: relating the operating limit to a wheel slip target and adjusting the wheel slip of the first axle and the wheel slip of the second axle based on the wheel slip target.

[0019] Further features of the chassis control method include planning based on driver torque request inputs and sensor feedback of non-linear control gains to adapt torque from the first torque source to the first axis and torque from the second torque source to the second axis.

[0020] Further applications of the present invention will become apparent from the detailed description, the claims, and the drawings. The detailed description and the specific examples serve only for illustration. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be more fully understood from the detailed description and the accompanying drawings; these show: Fig. 1 a functional block diagram of a vehicle comprising an example chassis control system comprising a vehicle control module with a phase plane module and a wheel slip and yaw module according to the present invention; Fig. 2 a functional block diagram of an example vehicle containing independently controlled torque sources which are controlled by means of a vehicle control module according to the present invention; Fig. 3 a functional block diagram of another example of a vehicle containing independently controlled torque sources which are controlled by means of a vehicle control module according to the present invention; Fig. 4 an exemplary graphical representation of the understeer angle versus the understeer speed, illustrating three different operating limits based on different sets of operating parameters and road conditions according to the present invention; Fig. 5 an exemplary graphical representation of the front axle wheel slip versus the rear axle wheel slip, which includes exemplary understeer, neutral steering and oversteer curves based on various sets of operating parameters and road conditions according to the present invention; Fig. 6 an exemplary graphical representation of the understeer angle versus the understeer speed, which includes exemplary torque amounts to be supplied to the front and / or rear axles according to the present invention; Fig. 7 an exemplary graphical representation of a torque against time illustrating a transition between a torque redistribution and a torque limiting control mode for a curve exit event with a road surface condition of high friction and a drivetrain system that is substantially driven by the rear wheel according to the present invention; Fig. 8 another exemplary graphical representation of a torque against time illustrating a transition between a torque redistribution, a torque limiting control and a feedback wheel slip control mode for a straight-line acceleration event with a low friction road surface condition and a drivetrain system substantially driven by the rear wheel according to the present invention; Fig. 9 a chassis control method comprising a transition between a torque redistribution and a torque limiting control mode according to the present invention; Fig. 10 an exemplary graphical representation of the understeer angle against time in relation to an exemplary operating limit for various exemplary operating modes according to the present invention; Fig. 11 An exemplary graphical representation of the understeer angle versus the understeer speed in relation to an exemplary operating limit for the exemplary operating modes of Fig. 10 according to the present invention; Fig. 12 An exemplary graphical representation of the steering angle against time for the exemplary operating modes of Fig. 10- Fig. 11 according to the present invention; Fig. 13 An exemplary graphical representation of a front axle torque against time for the exemplary operating modes of Fig. 10- Fig. 12 according to the present invention; Fig. 14 An exemplary graphical representation of a rear axle torque against time for the exemplary operating modes of Fig. 10- Fig. 13 according to the present invention and Fig. 15 a control diagram that illustrates an exemplary use of the graphical representation of Fig. 6 illustrated according to the present invention.

[0022] Reference symbols can be used multiple times in the drawings to identify similar and / or identical elements. DETAILED DESCRIPTION

[0023] Maintaining consistent vehicle handling (balance) with a human driver in the loop is a complex problem, especially in highly dynamic driving scenarios such as driving on a racetrack and / or driving on low-friction road surfaces (e.g., surfaces covered with ice or snow). A TCS system and an ESC system essentially employ torque-limiting control to manage a vehicle's wheel slip and yaw stability. An AWD system typically manages vehicle dynamics using torque-redistribution control. These systems have limited control and operate independently.

[0024] The examples presented here include a chassis control system and methods for seamlessly bridging gaps between conventional TCS, ESC, and AWD systems. The disclosed chassis control systems provide smooth transitions between a TCS and / or ESC system providing torque limiting control and an AWD system providing torque redistribution. This is done to enable improved handling dynamics and enhanced driving behavior on and off a racetrack. The disclosed examples aim to provide a consistent and tunable driver-centric vehicle handling balance by providing coordination between torque limiting control and torque redistribution.

[0025] The examples include i) interpreting a driver-intended vehicle handling equilibrium, ii) preventive torque control, and iii) integrated feedback control to simultaneously manage wheel slip and vehicle understeer dynamics. The interpretation of the driver-intended vehicle handling equilibrium includes i) defining a vehicle handling equilibrium operating limit based on parameters such as lateral acceleration, road surface condition, propulsion torque requested by the driver, and vehicle speed; ii) relating the operating limit to a wheel slip target; and iii) scheduling nonlinear control gains (i.e., torque to each axle) based on driver inputs and feedback from vehicle sensors.A preventive control system includes i) a seamless transition between a torque redistribution mode and a torque limiting control mode to achieve a target vehicle handling equilibrium state, and ii) a transition to a feedback wheel slip control system, as further described below.

[0026] Fig. Figure 1 shows a vehicle 100 containing a chassis control system 102, which includes a vehicle control module 104. The vehicle control module 104 contains a phase plane module 106 and a wheel slip and yaw module 108. The phase plane module 106 operates based on a relationship between an understeer angle and an understeer speed. The phase plane module 106 controls the yaw dynamics (or yaw behavior) of the vehicle 100 and its chassis by maintaining the yaw behavior of the chassis within set, driver-controllable limits, thus enabling the vehicle 100 to be driven with maximum controllability. Enhanced vehicle control is provided at actuator authority limits to maintain the vehicle 100 in a symmetrical handling state.The wheel slip and yaw module 108 intelligently switches between managing i) a relative slip target between a front axle and a rear axle (or front axles and rear axles) and ii) a single wheel slip to maximize handling performance. In one embodiment, modules 106 and 108 are software modules executed by the vehicle control module 104. Operations performed by modules 106 and 108 are further described below.

[0027] The vehicle 100 further includes sensors 110, a memory 112, an accelerator pedal actuator 114, a steering system 116, and a propulsion system 118. The sensors 110 can include wheel speed sensors 120, a vehicle speed sensor 122, a yaw rate sensor 124, an inertial measurement unit (IMU) 126, acceleration sensors (e.g., longitudinal and lateral acceleration sensors) 128, and other sensors 130. The memory 112 can store sensor data 132, operating limit information 134, applications 136, parameters 138, etc. The sensor data 132 can include data collected by the sensors 110 and / or other sensors, such as an accelerator pedal 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 pedal position sensor 140 and / or other devices to which reference may be made herein are connected to the vehicle control module 104 via a controller area network (CAN) or another network bus 143. The operating limit information 134 may contain equations, tables, etc., for determining the edges, magnitudes, and shapes of operating limits. The operating limits relate to understeer angles, understeer speeds, and understeer angle versus understeer speed limits, which are described below. The vehicle control module 104 can control the propulsion system 118, based on the sensor data, to maintain operation within a selected operating limit. The applications 136 may include modules 106, 108, and / or other applications.

[0028] The propulsion system 118 can include two or more torque sources, such as one or more motors and / or one or more power units (e.g., internal combustion engines). In the example shown in Fig. As shown in Figure 1, the vehicle 100 includes a power unit and one or more motors 152. The torque sources are controlled independently. The propulsion system includes an engine control system 154, which contains the one or more motors 152, and an engine control module 156, which can control the operation of the one or more motors 152 based on signals from the vehicle control module 104.

[0029] The vehicle control module 104 may also contain a mode selection module 160 and / or a parameter setting module 162. Modules 106, 108, and 160 can select various operating modes, such as a redistribution mode, a torque limiting control mode, a transition mode (or a partial torque redistribution and partial torque limiting control mode), a normal torque shaping mode, a front and / or rear axle torque increase mode, a front and / or rear axle torque rate reduction mode, a dynamic torque shaping mode, a preventive torque distribution mode, a feedback wheel slip control mode, a neutral steering mode, an understeer mode, an oversteer mode, a countersteering mode, a drift mode, a throttle lowering mode, a recuperation mode, etc. The vehicle can operate in two or more of these modes simultaneously.The torque redistribution mode refers to the selective delivery of torque to the front and / or rear axles of the vehicle. The torque limiting control mode refers to the limitation of torque to the front and / or rear axles. The specified operating modes are further described below.

[0030] Fig. Figure 2 shows a vehicle 200 containing independently controlled torque sources, which are controlled by a vehicle control module 202. The torque sources include a motor 206 and a power unit 208. The torque sources can include further torque sources (e.g., two or more motors). The vehicle control module 202 can accordingly be referred to as the vehicle control module 104 of Fig. 1 be configured and operate. The vehicle control module 202 controls the operation of the torque sources to control the amounts of torque received by one or more front axles 210 and one or more rear axles 212, and thus to the front wheels 214 and rear wheels 216. This specified control includes torque-based control, as described below, for the various disclosed operating modes.

[0031] Fig. Figure 3 shows a vehicle 300 containing independently controlled torque sources controlled by a vehicle control module 302. The torque sources include one or more front motors 304 (two are shown) and one or more rear motors 306 (two are shown). The vehicle control module 302 can accordingly be referred to as the vehicle control module 104 of Fig. 1. The vehicle control module 302 is configured and operates. The vehicle control module 302 controls the operation of the torque sources to control the amounts of torque received by one or more front axles 310 and one or more rear axles 312, and thus to the front wheels 314 and rear wheels 316. This specified control includes torque-based control, as described below for the various disclosed operating modes.

[0032] Fig. Figure 4 shows a graphical representation of the understeer angle versus the understeer speed, illustrating three different operating limits based on various sets of operating parameters and road conditions. Three example limits, 400, 402, and 404, are shown for three different sets of operating parameters and road conditions. The operating parameters include a vehicle speed (Vx), a propulsion torque requirement (Torq), and a lateral acceleration (Ay). The road conditions refer to the level of friction experienced between the tires of the respective vehicle and the road surface. A high Mu refers to a road surface with a high associated level of friction and thus a high amount of tire traction, such as when driving on a dry asphalt road.A medium Mu refers to a road surface with a medium associated friction level and thus a medium amount of tire traction, such as when driving on a gravel or wet road. A low Mu refers to a road surface with a low associated friction level and thus a low amount of tire traction, such as when driving on an ice- or snow-covered road. Limit 400 is associated with low Ay, low Mu, high Torq, and low Vx. Limit 402 is associated with high Ay, high Mu, high Torq, and medium Vx. Limit 404 is associated with high Ay, high Mu, medium Torq, and high Vx. Numerous other limits can be determined and / or selected based on the values ​​of Ay, Mu, Torq, and Vx.

[0033] A vehicle control module (e.g., one of the vehicle control modules from Fig. 1- Fig. 3) Determines the parameters Ay, Mu, Torq, and Vx and, based on these, determines parameters and / or selects an operating limit. The edges, magnitudes, and shapes of the operating limit can be determined using equations, lookup tables, etc., and / or can be selected from pre-stored limits. The operating limit can be determined as a non-linear function of Ay, Mu, Torq, and Vx. The operating limit includes understeer angle limits and understeer speed limits within which the vehicle control module remains. The vehicle control module adjusts torque levels to the front and / or rear axles to remain within the specified understeer angle and speed limits. Fig. 4. Positive understeer angles refer to understeer levels, an understeer angle of 0° refers to neutral steering, and negative understeer angles refer to oversteer levels.

[0034] Assuming the vehicle is a bicycle model, the understeer phase profile can be estimated using equations 1 and 2, where α Under the understeer angle is, ∝ F the front tire slip angle is, ∝ R the rear tire slip angle, δ the steering angle, L a distance between the centers of a front wheel and a rear wheel, aYCG,max a maximum lateral acceleration experienced through the center of gravity (CG) of the vehicle, L f a distance between the center of a front wheel of the vehicle and the CG is, L rwhere is a distance between the center of a rear wheel of the vehicle and the CG, ṙ is a yaw rate, µ is a forward rate, and g is the force of gravity. αUnder=(∝F−∝R)=δ−1Vx2(L⋅aYCG,max) daUnderdt≈(Lf−Lr)r˙Vx,aYCG,max=min(aYCG,μg)

[0035] Fig. Figure 5 shows a graphical representation of front axle wheel slip versus rear axle wheel slip, including an example understeer curve 500, an example neutral steering curve 502, a first example oversteer curve 504, and a second example oversteer curve 506. The curves are determined based on Ay, Mu, Torq, and Vx. Neutral steering refers to a one-to-one relationship between front wheel slip (of the front wheels or tires) and rear wheel slip (of the rear wheels or tires). Understeer refers to a higher front wheel slip than rear wheel slip. Oversteer refers to a higher rear wheel slip than front wheel slip.

[0036] A vehicle control module (e.g., one of the vehicle control modules from Fig. 1- Fig. 3) Determines the parameters Ay, Mu, Torq, and Vx and, based on these parameters, determines whether to follow and / or target an understeer curve, a neutral steering curve, or an understeer curve such as one of the curves shown. Curve 500 can be chosen as a regenerative slip target for examples. Curve 502 can be followed and / or targeted if Ay is high, Mu is high, Torq is medium, and Vx is high. Curve 504 can be followed and / or targeted if Ay is high, Mu is high, Torq is high, and Vx is medium. Curve 506 can be followed and / or targeted if Ay is low, Mu is low, Torq is high, and Vx is low.

[0037] The specified and / or selected operating limit is related to a front-to-rear slip target, such as one of the example curves 500, 502, 504, 506, or another front-to-rear slip curve. The slope of the selected curve defines the vehicle dynamics characteristics for understeer versus oversteer. As an example, if the target is curve 506, the vehicle control module allows a large amount of initial rear slip (as shown by the lower left portion of curve 506) to turn the vehicle into a corner and, as wheel slip develops, shifts the vehicle's balance from oversteer to neutral steering to improve traction and driver confidence, as shown by the upper right portion of curve 506.

[0038] Fig. Figure 6 shows a graphical representation 600 of the understeer angle versus the understeer speed, which includes exemplary torque values ​​that are applied to the front and / or rear axles of a vehicle (e.g., one of the vehicles of Fig. 1- Fig. 3) are to be supplied. The graphical representation establishes a method for scheduling non-linear control gains (or a non-linear magnitude of the output torque from torque sources) based on driver inputs (e.g., accelerator pedal position and steering angle) and actual vehicle feedback from sensors. An operating limit 602 is shown together with i) negative torque values ​​relating to one or more torque sources of one or more rear axles supplying torque to the rear wheels, and ii) positive torque values ​​relating to one or more torque sources of one or more rear axles supplying torque to the rear wheels. These torque values ​​are supplied based on Ay, Mu, Torq, and Vx values. Positive torque values ​​relate to shifting torque to one or more front axles.Negative torque values ​​refer to a torque offset to one or more rear axles. A zero torque value refers to no torque offset between the front and / or rear axles. Torque can be supplied to both front and / or rear axles when the vehicle control module is operating in operating limit 602.

[0039] Under certain conditions, the vehicle control module can transition from operating near the upper end of the operating limits to a lower end. This can occur, for example, when the vehicle is exiting and accelerating out of a curve. As the vehicle control module moves from the upper to the lower end of the operating limits, the torque values ​​increase, decrease slightly, and then increase again. The large initial increase in torque (or torque offset) from one or more rear axles to one or more front axles serves to stabilize the vehicle and mitigate the initial breakaway event. If the oversteer persists, the vehicle control module determines that the oversteer is intentional on the part of the driver.

[0040] Although the following Fig. 7- Fig. Since operations described in section 8 are essentially rear-wheel drive for a vehicle, similar operations can be performed for a vehicle that is essentially front-wheel drive. Operations described with respect to the rear axle would be performed for the front axle and vice versa. Furthermore, the limits and thresholds would be adjusted accordingly. The operations described with respect to Fig. 7- Fig. The operations described in section 8 are carried out by one of the vehicle control modules disclosed herein.

[0041] Fig. Figure 7 shows an exemplary graphical representation of torque versus time, representing a transition between a torque redistribution and a torque limiting control mode for a corner exit event with a high-friction road surface condition and a drivetrain system that is substantially rear-wheel driven. A driver total torque request curve 700, a rear axle torque curve 702 for a vehicle having a single rear axle, and a front axle torque curve 704 for the vehicle having a single front axle are shown. A rear engine torque limit (or first torque source limit) 706, a rear wheel limit 708, a rear wheel redistribution threshold 710, a front engine torque limit (or second torque source limit) 712, and a front wheel limit 714 are shown.

[0042] The example of Fig. Figure 7 illustrates a transition from a torque redistribution mode to a torque limiting control mode, as represented by bar 719. This involves a transition from first a normal torque-shaping mode 720 to a front and / or rear axle torque increase mode 722, to a front and / or rear axle torque rate decrease mode 724, and then to a dynamic torque-shaping mode 726. Modes 720 and 722 can refer to torque redistribution modes. Mode 724 can refer to a partial torque redistribution and torque limiting control mode (or transition mode).

[0043] During Mode 720, the amount of torque requested by the driver increases at an initial rate. The vehicle control module increases the rear axle torque (or the torque to one or more rear axles) to accommodate the increase in driver-requested torque. The vehicle control module transitions to Mode 722 when the rear axle torque reaches the rear axle redistribution threshold.

[0044] During Mode 722, the vehicle control module increases both the rear axle torque and the front axle torque (or the torque to one or more front axles). The rear axle torque is increased at a second rate. This second rate is lower than the first rate experienced during Mode 720. The front axle torque can be increased at the second rate or at a different rate. The torque is increased at both axles to prevent an imbalance. At the end of Mode 722, the rear and front axles begin to slip simultaneously. Mode 722 begins when the amount of rear axle torque reaches the rear axle redistribution threshold, which can be preset and / or adjusted. In one embodiment, the rear axle redistribution threshold is arbitrarily set.

[0045] At the end of mode 722, the front and / or rear axles may begin to slip. Front axle slip causes understeer. Rear axle slip causes oversteer. If both axles slip simultaneously by the same amount, neutral steering occurs.

[0046] During Mode 724, the rear and front axle torque are increased. The rear axle torque is increased at a third rate, which is lower than the second rate. The front axle torque can be increased at the third rate or at a further rate. The front axle torque is increased at a lower rate than during Mode 722. During Mode 724, the vehicle control module switches between torque redistribution mode and torque limiting control mode (or torque limiting mode).

[0047] During mode 726, the rear axle torque is increased at a fourth rate, which is lower than the third rate. The front axle torque is not increased during this mode. The front axle torque is limited to the front engine limit. The rear axle torque is limited to the rear engine limit.

[0048] In the example shown, the normal torque-shaping mode is implemented when the vehicle begins to exit the curve, operating in modes 722 and 724 during a mid-section of the exit event, and in dynamic torque-shaping mode at the end of the curve exit. After exiting the curve, if the amount of driver torque requested decreases, the vehicle control module can then operate in modes 720, 722, 724, and 726 in reverse order.

[0049] In one embodiment, the transition phase into and out of threshold values ​​for mode 724 is calculated based on a predicted time to achieve maximum engine performance or tire limit (before slippage) on the front axle, whichever comes first.

[0050] Fig. Figure 8 shows a graph of torque versus time, representing a transition between a torque redistribution, a torque limiting control, and a feedback wheel slip control mode for a straight-line acceleration event with a low-friction road surface condition and a drivetrain system that is substantially rear-wheel driven. A driver total torque request curve 800, a rear axle torque curve 802 for a vehicle having a single rear axle, and a front axle torque curve 804 for the vehicle having a single front axle are shown. A rear engine torque limit (or first torque source limit) 806, a front engine torque limit (or second torque source limit) 808, a rear wheel limit 810, a front wheel limit 812, and a rear wheel redistribution limit 814 are shown.

[0051] The example of Fig. Figure 8 illustrates a transition from a torque redistribution mode to a torque limiting control mode. This involves a transition from initially being in a preventive torque distribution mode 820, to a front and / or rear axle torque increase mode 822, to a front and / or rear axle torque rate decrease mode 824, and then to a dynamic torque shaping mode 826. Modes 820, 822, and 824 can refer to torque redistribution modes. The beginning (or first section) of mode 826 can refer to a partial torque redistribution and partial torque limiting control mode (or transition mode). The second section of mode 826 can refer to a torque limiting control mode.

[0052] During Mode 820, the amount of torque requested by the driver increases at an initial rate. The vehicle control module increases the rear axle torque and the front axle torque to accommodate the increase in driver-requested torque. Preventive torque is sent to the front axle (or axles) in addition to the torque sent to the rear axle (or axles). The rate of increase of torque to the front axle can be the same as, or different from, the rate of increase of torque to the rear axle. In the example shown, the amount of torque delivered to the front axle is less than the amount of torque delivered to the rear axle. The rate of increase of torque delivered to the front axle is also less than the rate of increase of torque to the rear axle.

[0053] During Mode 822, the vehicle control module increases both the rear axle torque and the front axle torque. The rate of increase for the rear axle torque is lower than the rate of increase for the rear axle torque during Mode 820. The front axle torque is increased to a level slightly below the front axle limit 812. For example, the front axle torque might be 95-98% of the front axle limit 812. During Mode 822, the front axle torque can change at various rates, as shown. During Mode 822, the torque on both axles is increased to prevent an imbalance. At the end of Mode 822, the rear and front axles begin to slip simultaneously. Mode 822 begins when the amount of rear axle torque reaches the rear axle redistribution limit.

[0054] During mode 824, the rear axle torque is increased while the front axle torque remains constant. The rate of increase of the front and / or rear axle torque can be reduced. The rate of increase of the rear axle torque can be equal to or less than the rate used during mode 822. The rate of increase of the front axle torque is reduced to zero.

[0055] When the rear axle torque reaches the rear wheel limit torque, mode 826 is executed, and the vehicle control module transitions from torque redistribution mode to torque limiting control mode. The vehicle control module operates in a dynamic torque-shaping mode and transitions to closed-loop wheel slip control. This transition occurs at the beginning of torque limiting control mode 826, as shown by area 828. At the end of the transition, the vehicle control module operates in a feedback wheel slip control mode, as shown by area 830. Fig. 8 is represented. During feedback wheel slip control mode, the rear axle experiences a low slip level, and the front axle outputs a torque amount slightly less than the amount required to cause slip at the front axle. The torque level delivered to the front axle is provided to maintain steering. During feedback wheel slip control mode, the control is performed with a closed-loop system. The vehicle control module can monitor rotational speeds between the front and / or rear wheels and operate to maintain a target torque amount at the rear wheels.

[0056] In one embodiment, the rear axle torque is kept above the rear wheel slip limit (the torque level at which the rear wheels begin to slip). The front axle torque is kept below the front wheel slip limit to promote neutral handling and steering feel for the driver. A similar control system can be implemented for a vehicle that is essentially front-wheel drive.

[0057] Fig. Figure 9 shows a chassis control procedure that includes a transition between a torque redistribution and a torque limiting control mode. The following operations can be performed iteratively. The following operations can be performed by the vehicle control module 104 and / or the wheel slip and yaw module 108 of Fig. 1 and / or further modules disclosed herein. The following operations are applicable to the vehicle, which has one or more front axles and / or one or more rear axles. A front axle reference refers to one or more front axles, and the torque supplied to the front axle is distributed to the one or more front axles. A rear axle reference refers to one or more rear axles, and the torque supplied to the rear axle is distributed to the one or more rear axles. Operations 900, 902, 904, 906, 908, 910, 912, 914, and 916 are associated with torque redistribution control. Operations 918, 920, and 922 are associated with torque limiting control. In operation 900, the vehicle control module 104 determines the total torque requested by a driver. This can be based on a throttle position.

[0058] In operation 902, the vehicle control module 104 determines whether the total torque requested by a driver exceeds a rear torque redistribution threshold. If so, operation 904 is performed; otherwise, operation 918 is performed. In operation 904, the vehicle control module 104 provides a total rear threshold torque level to the front axle. The total rear threshold level refers to a torque output limit of a rear axle torque source.

[0059] In 906, the vehicle control module 104 determines whether the amount of torque delivered to the front axle exceeds the front wheel limit (referred to as the front tire capacity), at which the front wheels begin to slip. In 908, the vehicle control module 104 delivers excess torque back to the rear axle. The excess torque refers to the difference between the total rear threshold torque and the front tire capacity.

[0060] In operation 910, the vehicle control module 104 determines whether the sum of the rear torque plus the excess torque exceeds the rear wheel limit (referred to as the rear tire capacity). If so, operation 912 is performed; otherwise, operation 918 is performed. In operation 912, the vehicle control module 104 distributes the remaining torque between the front and / or rear axles based on vehicle dynamics conditions.

[0061] In operation 914, the vehicle control module 104 determines whether the torque supplied to the front axle exceeds the front torque limit. If so, operation 916 is performed; otherwise, operation 918 is performed. In operation 916, the vehicle control module 104 sends any remaining excess torque to the rear axle and reduces the rate of change of the rear axle torque. Operation 900 can be performed after operation 916.

[0062] In operation 918, the wheel slip and yaw module 108 determines whether the rear wheel slip speed is greater than the front wheel slip speed. If not, operation 920 is performed; otherwise, operation 922 is performed. In operation 920, the wheel slip and yaw module 108 determines whether a yaw rate of the corresponding vehicle indicates an oversteer event. If so, operation 922 is performed; otherwise, operation 900 is performed. In operation 922, the wheel slip and yaw module 108 reduces the amount of torque delivered to the rear axle.

[0063] The following Fig. 10- Fig. Figure 14 are graphical examples of neutral steering, counter-steering, drift, throttle fall, and recuperation operating modes. The graphical examples are for a vehicle with one or more front axles and one or more rear axles. The following description below applies. Fig. 10 and Fig. 12- Fig. Section 14 is described in relation to a front axle and a rear axle. In the description of Fig. 10 and Fig. 12- Fig. 14 References to ‘the front axle’ refer to one or more front axles and references to ‘the rear axle’ refer to one or more rear axles.

[0064] Each of Fig. 10 and Fig. 12- Fig. Figure 14 contains a curve, with sections of the curve being assigned to the neutral steering, counter-steering, drift, throttle drop and recuperation operating modes. Fig. 10 and Fig. 12- Fig. The 14 are provided as examples and are assigned to the same sequence of events. One of the vehicle control modules disclosed herein may be implemented in a vehicle that controls the understeer angles of Fig. 10 and the corresponding understeer speeds of Fig. 11. The vehicle control module monitors the understeer angle, understeer speed, and steering angle of the vehicle and, based on these parameters and operating limits referenced below, adjusts the amount of torque delivered to the front and rear axles of the vehicle, as described by Fig. 13- Fig. Figure 14 shows a graphical representation of the steering angle. Fig. 12 provided.

[0065] Fig. Figure 10 shows a graphical representation of the understeer angle against time with respect to an exemplary operating limit of 1000. The operating limit of 1000 is associated with oversteer without vehicle skidding. The phase plane module 106 of Fig. 1 prevents the vehicle from skidding by operating within an operating limit, as described herein. In one embodiment, the phase-plane module 106 allows the vehicle to slide, e.g., while operating in a drift mode, but prevents the vehicle from operating in such a way that it skids. The graphical representation includes a curve 1002, which has sections A, B, C, and D, corresponding to a counter-steering mode, a drift mode, a throttle-fall mode, and a recuperation mode, respectively. These modes can be executed by the vehicle control module.

[0066] Fig. Figure 11 shows a graphical representation of the understeer angle versus the understeer speed with respect to an exemplary operating limit of 1100. Points in area 1102 are assigned to drift mode B. Points in area 1104 are assigned to throttle drop mode C. Points in area 1106 are assigned to recuperation mode D. The remaining points of Fig. 11 are assigned to counter-steering mode A.

[0067] Fig. Figure 12 shows a graph of the steering angle against time. The graph includes a curve 1200, which contains sections A, B, C, and D, corresponding to the counter-steering mode, the drift mode, the throttle drop mode, and the recuperation mode, respectively.

[0068] Fig. Figure 13 is an exemplary graphical representation of a front axle torque against time. The graphical representation includes a curve 1300, which contains sections A, B, C, and D, corresponding to the counter-steering mode, the drift mode, the throttle drop mode, and the recuperation mode, respectively.

[0069] Fig. Figure 14 is an exemplary graphical representation of rear axle torque versus time. The graphical representation includes a curve 1400, which contains sections A, B, C, and D, corresponding to the counter-steering mode, the drift mode, the throttle drop mode, and the recuperation mode, respectively.

[0070] Fig. Figure 15 shows a control diagram 1500, which is an exemplary use of the graphical representation 600 of Fig.Figure 6 illustrates this. The graphical representation shows an understeer angle versus the understeer speed, including exemplary torque amounts to be supplied to the front and / or rear axles. Sensor inputs, e.g., from a steering angle sensor 1502, a yaw rate sensor 1504, and wheel speed sensors 1506, are shown. Actual understeer dynamics 1508 and manipulated understeer dynamics 1510 are determined based on outputs from sensors 1502, 1504, and 1506. Torque offset amounts for shifting torque amounts between the front and / or rear axles are determined based on the actual understeer dynamics 1508 and the manipulated understeer dynamics 1510. The control instructions 1512 are then generated to supply the torque offset amounts.

Claims

[1] Chassis control system (102) of a vehicle (100, 200), wherein the chassis control system (102) comprises: a first torque source (206) configured to supply torque to a first axle (210) of the vehicle (100, 200); a second torque source (208) configured to deliver torque to a second axle (212) of the vehicle (100, 200) independently of the first torque source (206); and a vehicle control module (104) configured to control the first torque source (206) and the second torque source (208); characterized by , that the vehicle control module (104) is configured to control the first torque source (206) and the second torque source (208) based on a wheel torque redistribution threshold, a wheel torque limit of the first axle (210) and / or the second axle (212), and a torque limit of one of the first torque source (206) and the second torque source (208) in order to switch between a torque redistribution mode and a torque limiting control mode, wherein the torque redistribution mode refers to the selective delivery of torque to the first axle (210) by the first torque source (206) and torque to the second axle (212) by the second torque source (208), and the torque limiting control mode refers to the limitation of torque to the first axle (210) and the second axle (212); the vehicle control module (104) is further configured as follows: (i) to increase a torque on the first axle (210) at a first rate and on the second axle (212) at a second rate until the torque on the second axle (212) reaches the wheel torque limit of the second axle (212), and then to increase a torque on the first axle (210) at a third rate and on the second axle (212) at a fourth rate, the third rate being lower than the first rate and the fourth rate being lower than the second rate; or (ii) during operation in torque limiting control mode, limit the torque supplied to the first axis (210) based on a torque limit of the first torque source (206) and refrain from increasing any torque at the second axis (212); or (iii) to determine a lateral acceleration of the vehicle (100, 200), a torque quantity requested by a driver of the vehicle (100, 200), a speed of the vehicle (100, 200) and a road surface condition; to determine an operating limit for the understeer angle versus the understeer speed based on the vehicle's lateral acceleration (100, 200), the amount of torque requested by the vehicle's driver (100, 200), the vehicle's speed (100, 200), and the road surface condition; and to adjust the torque to the first axle (210) and the second axle (212) in order to keep the operation of the vehicle (100, 200) within the operating limits; or (iv) to determine whether a torque requested by a driver is greater than the wheel torque redistribution threshold; to deliver, in response to the fact that the amount of torque requested by a driver is greater than the wheel torque redistribution threshold, an amount of torque equal to a torque limit for the first axle (210), from the second torque source (208) to the second axle (212); and to switch from operating in torque redistribution mode to torque limiting control mode in response to the fact that the amount of torque requested by a driver is not greater than the wheel torque redistribution threshold. [2] Chassis control system (102) according to claim 1, wherein the vehicle control module (104) is configured to switch from a normal torque-shaping mode to a torque-boosting mode based on a torque amount requested by a driver of the vehicle (100, 200) and the wheel torque redistribution threshold; and The vehicle control module (104) increases torque on the first axle (210) and the second axle (212) simultaneously during torque increase mode. [3] Chassis control system (102) according to claim 1, wherein the vehicle control module (104) is configured to switch from torque redistribution mode to torque limiting control mode when the torque at the second axle (212) reaches the wheel torque limit of the second axle (212), which involves increasing torque to the first axle (210) at a fifth rate and to the second axle (212) at a sixth rate; wherein the fifth rate is lower than the third rate and the sixth rate is lower than the fourth rate. [4] Chassis control system (102) according to claim 1, wherein the vehicle control module (104) is configured to proactively increase torque to the first axle (210) and to the second axle (212) based on a torque request from a driver of the vehicle (100, 200). [5] Chassis control system (102) according to claim 4, wherein the vehicle control module (104) is configured to transition from preventive torque increase to the first axis (212) at a first rate and to the second axis (212) at a second rate to operating in a torque increase mode, which includes increasing torque to the first axis (210) at a third rate and to the second axis (212) at a fourth rate; wherein the third rate is lower than the first rate and the fourth rate is different from the second rate. [6] Chassis control system (102) according to claim 5, wherein the vehicle control module (104) is configured to switch from a torque increase mode to a torque rate reduction mode, wherein the torque rate reduction mode comprises refraining from increasing the torque to the second axle (212) and maintaining a torque amount at the second axle (212) below a wheel torque limit of the second axle (212).

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