Torque Control Method, Device and System for Electric Vehicle Hill Parking and Starting

Abstract

The present invention relates to a torque control method, device and assisted driving system for an electric vehicle to start on a ramp during parking. First, obtain the current state information of the electric vehicle, where the state information includes the current driving parameters of the vehicle, the current ramp value where the vehicle is located, and the ramp direction; then, based on the comfortable acceleration and the critical vehicle speed, control the driving torque and braking torque of the vehicle in stages until the vehicle stops or starts on the ramp. The present invention, according to different scenarios, finely controls the moment distribution of the vehicle's parking and starting processes by dividing scenarios and stages. The deceleration control before parking is continuous, the deceleration before parking is small, the braking force can maintain parking after parking, the speed change at the starting moment is small, and the acceleration control is continuous, which can well solve the problems of vehicle rollback and jerks encountered by the assisted driving system during ramp parking and starting, and improve the assisted driving experience and technical level.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle assisted driving, and particularly relates to a torque control method, device and assisted driving system for an electric vehicle to park and start on a ramp. Background Art

[0002] In the prior art, in most cases, when the assisted driving system controls the vehicle to perform ramp parking or starting, the sense of jerk is relatively serious, and it is also easy to produce a vehicle rollback phenomenon when starting to park on an uphill. Therefore, when the assisted driving function develops towards a higher-level assisted driving function, it needs to adapt to a wider range of ramps.

[0003] The traditional control method is as follows: when following and stopping on a ramp, the vehicle is mainly controlled to a stop with a constant small acceleration / deceleration, and the braking force is maintained when the vehicle speed is 0. However, when the vehicle speed is 0 during the uphill process, the braking force of the vehicle may not be able to meet the requirements of vehicle ramp parking. Due to the influence of the self-gravity component of the vehicle on the ramp, after the speed is 0, the vehicle rolls back, or the deceleration before the vehicle speed decreases to 0 during the downhill process is large, resulting in a large sense of jerk when parking; during the starting process, the vehicle is mainly controlled to start according to a constant acceleration, the preliminary driving force is calculated and applied to the vehicle while the braking force is released. However, the initial driving force applied during ramp starting may not be sufficient to maintain the forward driving of the vehicle or may be too large, which is likely to cause vehicle rollback during uphill starting and a large sense of jerk due to excessive acceleration during downhill starting.

[0004] There is a smart vehicle parking control method in the prior art, which can be mainly used to ensure that the vehicle maintains a certain braking pressure under the decelerating driving condition, and when the deceleration switches to the parking condition, the vehicle is precisely parked based on the original braking pressure. The vehicle can query the drive torque relationship table according to the road parameters and the current vehicle speed and generate the drive torque by the method of linear interpolation, and then control the braking force according to the driving force value and the deceleration requirement. In this way, at the moment before the vehicle speed is 0, due to the existence of the braking force, the vehicle can be stably switched from the decelerating state to the parking state to a certain extent, improving the user experience and avoiding the occurrence of vehicle rollback, ensuring the safety of the user.

[0005] However, this technical solution is only applicable to the working condition where the prerequisite is that the vehicle decelerates and parks on an uphill. This solution is largely limited by the accuracy and rationality of the pre-set parameters and lacks dynamic adaptability. Although it can maintain the stable uphill parking of the vehicle to a certain extent, the driving torque needs to be maintained for a certain period of time after the vehicle stops, resulting in a certain degree of energy waste, and it cannot solve the problem of excessive deceleration causing jerk at all times. Further, it cannot solve the problems of vehicle rollback and jerk during ramp starting. Summary of the Invention

[0006] In view of the technical problems existing in the prior art, the present invention provides a torque control method, device and assisted driving system for an electric vehicle to start on a ramp, assisting in the driving force and braking force distribution strategies during the stop and start of the vehicle on the ramp, improving the control performance of the assisted driving system on the ramp, making the vehicle stable without slipping and comfortable during the stop and start on the ramp, ensuring the safety of users and providing a comfortable driving experience.

[0007] The technical solution of the present invention to solve the above technical problems is as follows:

[0008] In a first aspect, the present invention provides a torque control method for an electric vehicle to start on a ramp, including the following steps:

[0009] S1, obtaining the current state information of the electric vehicle, where the state information includes the current driving parameters of the vehicle, the current ramp value where the vehicle is located, and the ramp direction;

[0010] S2, controlling the driving torque and braking torque of the vehicle in stages based on the comfortable acceleration and the critical vehicle speed until the vehicle stops or starts on the ramp;

[0011] The comfortable acceleration A 舒适 is the maximum value that will not cause a jerky feeling during parking or starting, negative during the parking process, positive during the starting process, and |A 舒适 | < |A max |, the value of A 舒适 is set according to empirical values, and A max is the maximum deceleration allowed by the cruise control function;

[0012] The critical vehicle speed V 2 is defined as follows: Assuming that the braking system starts to intervene from an acceleration of 0 until the vehicle reaches A max in a time of T, there is an acceleration change threshold K, the acceleration from 0 to A max in a time of T, the acceleration at any time t is A = K * t, and the safety factor C of the braking system control, then and V 2 > V 1 , V 1 is the critical wheel speed, that is, the wheel speed that can only overcome the elastic deformation of the tire and the deformation of the suspension without causing the vehicle to move.

[0013] Further, the method further includes dividing the ramp stop and start into four different working conditions: uphill stop, uphill start, downhill stop, and downhill start according to the stop or start requirements and the current state information.

[0014] Further, S2 includes: based on the comfortable acceleration and the critical vehicle speed, for the uphill parking condition, controlling the driving torque and the braking torque of the vehicle in stages until the vehicle stops on the ramp, specifically including the following:

[0015] Obtain the current vehicle speed V and the acceleration value A at the current moment, and calculate the ramp parking braking force demand F under the current ramp according to the following-stop target position and the road surface adhesion coefficient 制 , the maximum deceleration A that can be generated by free coasting on the uphill ramp 滑 and the maximum deceleration A allowed by the cruise control function max ; if A > 0, enter S001-3, if A < 0 and A 滑 < A max , enter S001-1, if A < 0 and A 滑 > A max , enter S001-2,

[0016] S001-1, the braking force does not intervene, the driving force decays, with the target of reaching A max and the acceleration change rate being less than the threshold K, perform PID control on the decay of the driving force, and continuously judge the vehicle speed and acceleration in real time. If A > A max and V > V 2 , then loop and execute S001-1. If A = A max and V > V2, enter S002-1. If V 1 < V ≤ V 2 , enter S003-1. If V ≤ V 1 , enter S004-1;

[0017] S002-1, the braking force does not intervene, the driving force is maintained, and the vehicle decelerates at an acceleration of A max . If V > V 2 , then loop and execute S002-1. If V = V 2 , interrupt S002-1 and enter S003-1;

[0018] S003-1, the braking force does not intervene, the driving force increases, with the target of the vehicle speed dropping to V 1 before, the acceleration changes from A max to A 舒适 and the acceleration change rate being less than the threshold K, perform PID control on the intervention of the braking force. When the vehicle speed reaches V 1 , enter S004-1;

[0019] S004-1, the braking force increases to the maximum braking capacity according to (F 制+(Current driving force) to ensure that the vehicle can achieve hill parking without rolling back. After the braking force reaches, the driving force is cut off and the uphill parking ends;

[0020] S001-2, the braking force does not intervene, and the driving force decays to 0 until the acceleration value reaches A 滑 And the acceleration change rate is less than the threshold K as the control target. Perform PID control on the decay of the driving force, and judge the vehicle speed and acceleration in real time.

[0021] If V > V 2 And A > A 滑 , then loop and execute S001-2.

[0022] If V > V 2 And A ≤ A 滑 , then interrupt S001-2 and enter S002-2.

[0023] If V ≤ V 2 , then further judge the acceleration when V ≤ V 2 . If the acceleration A < A 舒适 , then interrupt S001-2 and enter S002-3; if the acceleration A > A 舒适 , then interrupt S001-2 and enter S002-4.

[0024] If V < V 1 , interrupt S001-2 and enter S003-3;

[0025] S002-2, the braking force increases and the driving force remains disconnected until the acceleration value reaches A max And the acceleration change rate is less than the threshold K 1 As the control target, perform PID control on the intervention of the braking force, and judge the vehicle speed and acceleration in real time. If V > V 2 , then loop and execute S002-2. If V = V 2 , then interrupt S002-2 and enter S003-2; K 1 < K;

[0026] S003-2, the braking force decays and the driving force follows the adjustment to change the acceleration from A 1 Before reaching V max To A 舒适 And the acceleration change rate does not exceed K as the control target. Perform PID control on the decay of the braking force. When the vehicle speed V = V 1 , interrupt S003-2 and enter S004-2;

[0027] S004-2, the braking force instantaneously increases to (F 制+(Current driving force). After the braking force is reached, the driving force is released to maintain the vehicle from rolling back during ramp parking, and the uphill parking ends;

[0028] S002-3, the braking force does not intervene, and the driving force increases to reach V at speed V 1 Previously, control the acceleration at A 舒适 And the acceleration change rate is less than K 1 As the control target, perform PID control on the increase of the driving force. When V ≤ V 1 Enter S003-3;

[0029] S002-4, the braking force increases and the driving force is cut off to reach V at speed V 1 Previously, control the acceleration at A 舒适 And the acceleration change rate is less than K 1 As the control target, perform PID control on the braking force. When V ≤ V 1 Enter S003-3;

[0030] S003-3, the braking force increases to (F 制 +Current driving force) to ensure that the vehicle can achieve ramp parking without rolling back. After the braking force is reached, the driving force is cut off, and the uphill parking ends.

[0031] Furthermore, S2 includes: Based on the comfortable acceleration and the critical vehicle speed, for the uphill start condition, control the driving torque and braking torque of the vehicle in stages until the vehicle starts on the ramp, specifically including the following:

[0032] Obtain the current vehicle speed V and the current acceleration value A in real time; after receiving the start demand, enter S101;

[0033] S101, the braking force decays and the driving force increases. During any period of this stage, |decreased braking force| < |increased driving force|, and the torque change difference increases linearly until the vehicle speed V > V 1 A starting trend is generated; the torque change difference = ||increased driving force| - |decreased braking force||, and |·| represents taking the absolute value;

[0034] S102, the braking force decays to 0 and the driving force follows the adjustment to reach A with the vehicle acceleration A 舒适 The acceleration change rate is less than K and the braking force must drop to 0 before the vehicle acceleration A reaches A 舒适 As the control target, perform PID adjustment on the braking force and driving force. The difference between the driving force and the braking force conforms to a linear change trend; when the acceleration A reaches A 舒适 And the braking force is 0, if the vehicle speed V < V 2 Enter S103, if the vehicle speed V > V2 The uphill start ends,

[0035] S103, the braking force is 0, the driving force increases, and reaches A at an acceleration of A max And with the small acceleration change rate of K as the control target, perform PID control on the driving force. After the acceleration A reaches Amax, the driving force is maintained. During this process, the vehicle speed V is judged. If V < V 2 Maintain S103 until V ≥ V 2 , the uphill start ends.

[0036] Furthermore, S2 includes: Based on the comfortable acceleration and the critical vehicle speed, for the downhill parking condition, control the driving torque and braking torque of the vehicle in stages until the vehicle stops on the ramp. Specifically, it includes the following:

[0037] Calculate the ramp parking braking force demand F for downhill 制 and the maximum deceleration A allowed by the cruise control function max , obtain the current acceleration A of the vehicle. If A > 0, enter the S201-1 stage; if A < 0, enter S201-2;

[0038] S201-1, the braking force increases, the driving force decays, with the vehicle acceleration reaching 0, the driving force being 0, and the acceleration change rate being less than the threshold K as the control target, perform PID control on the braking force and driving force, and the absolute value of the difference between the braking force and the driving force || increased braking force| - |decreased driving force|| conforms to the linear growth law and the driving force must drop to 0 before the acceleration A reaches 0. During this process, the acceleration and vehicle speed are judged in real time. If A > 0, maintain S201-1. If A = 0 and V > V 2 , enter S202-1. If A = 0 and V ≤ V 2 , enter S203-2;

[0039] S202-1, the braking force increases, the driving force does not intervene, with the acceleration reaching A max as the control target and the acceleration change rate being less than the threshold K as the control target, perform PID control on the increase of the braking force. After the acceleration reaches A max the braking force is maintained. During this process, the vehicle speed is judged in real time. If V > V 2 , maintain S202-1. If V ≤ V 2 , enter S203-1;

[0040] S203-1, the braking force decays, the driving force does not intervene, with the deceleration being controlled at A 1 before the speed reaches V 舒适 and the deceleration change rate being less than the threshold K as the control target, control the decay of the braking force. During this process, the vehicle speed is judged in real time. If V > V1 , maintain S203-1 if V ≤ V 1 , enter S204;

[0041] S201-2, the braking force increases and the driving force decays. Regardless of whether there is a driving force on the vehicle currently, in this stage, the control target is that the vehicle deceleration reaches Amax, the driving force is 0, and the acceleration change rate is less than the threshold K. PID control is performed on the braking force and the driving force, and the absolute value of the difference between the braking force and the driving force conforms to the linear growth law and the acceleration reaches A max Before that, the driving force must be reduced to 0. During this process, the vehicle speed is judged. If V > V 2 , maintain S201-2, continue to increase the acceleration or maintain A max for deceleration. If V ≤ V 2 , enter S202-2; the absolute value of the difference between the braking force and the driving force = || increased braking force | - | decreased driving force ||;

[0042] S202-2, the braking force decays and the driving force does not intervene. The acceleration is controlled at A 1 before the vehicle speed reaches V 舒适 as the control target, and PID control is performed on the decay of the braking force. After reaching the acceleration A 舒适 , the braking force is maintained. During this process, the vehicle speed is judged in real time. If V > V 1 , maintain S201-2, continue to control the acceleration or maintain A 舒适 for deceleration; if V ≤ V 1 , enter S204;

[0043] S203-2, the braking force increases and the driving force does not intervene. The acceleration is controlled to A 1 before the speed becomes V 舒适 and the acceleration change rate is less than the threshold K as the control target. After the acceleration reaches A 舒适 , the braking force is maintained and enters S204 after the vehicle speed reaches V 1 ;

[0044] S204, the braking force is controlled at F 制 , maintain parking, and the downhill parking ends.

[0045] Furthermore, S2 includes: based on the comfortable acceleration and the critical vehicle speed, for the downhill start condition, the driving torque and the braking torque of the vehicle are controlled in stages until the vehicle starts on the ramp, specifically including the following:

[0046] The precondition of the vehicle before downhill start is that the vehicle is stationary, the driving force is greater than 0, and the braking force is greater than or equal to 0; after receiving the start demand, calculate the minimum parking braking force F required under the current ramp 制and the maximum acceleration A allowed by the cruise control function max , enter S301;

[0047] S301, release the braking force, cut off the driving force, quickly release the braking force to near F 制 , and then slowly decay, so that the vehicle relies only on the gravity component to overcome the braking force and rolling resistance to reach the critical speed V 2 , there are the following three situations during the release of the braking force:

[0048] a) During the release of the braking force, the wheel speed is less than V 1 , continue to release the braking force maintained in S301;

[0049] b) During the release of the braking force, the wheel speed reaches V 1 , the vehicle reaches the critical speed V 2 enter S302-1;

[0050] c) After the braking force is released, the wheel speed is less than V 1 , the gravity component of the vehicle on the current slope is not enough to overcome the wheel deformation and rolling resistance to make the vehicle reach the critical speed V 2 , enter S302-2;

[0051] S302-1, the braking force decays, the driving force is cut off or increased, and the acceleration is controlled to A 2 before the vehicle speed reaches V 舒适 and the acceleration change rate is less than K as the control target, perform PID control on the braking force and driving force, ||reduce the braking force| + |increase the driving force|| conforms to the linear growth law, and keep the current braking force or driving force after the acceleration reaches A 舒适 , and judge the vehicle speed during this process;

[0052] S302-2, slowly increase the driving force to make the wheel speed reach the critical wheel speed V 1 ;

[0053] S303, increase the driving force, and control the acceleration to A 2 before the vehicle speed reaches V 舒适 and the change rate does not exceed the threshold K as the control target, control the increase of the driving force, and keep the driving force after reaching A 舒适 ;

[0054] After S302-1 and S303 are executed and the vehicle speed reaches V 2 , the downhill start ends.

[0055] Further, the electric vehicle is configured with an air suspension. The method further includes, when switching between working conditions such as uphill parking, uphill starting, downhill starting, and downhill parking, adjusting the height and hardness of the air suspension to increase the vehicle rigidity and reduce the jitter during the switching of the vehicle motion state.

[0056] Further, the seat belt of the electric vehicle is configured with an electric retractor. The method further includes, when switching between working conditions such as uphill parking, uphill starting, downhill starting, and downhill parking, adjusting the seat belt pre-tension degree to mitigate the driver's subjective feeling of the vehicle motion state switching.

[0057] In a second aspect, the present invention further provides a torque control device for an electric vehicle to park and start on a slope, including:

[0058] A data acquisition module, configured to acquire the current state information of the electric vehicle, where the state information includes the current driving parameters of the vehicle, the current slope value of the vehicle, and the slope direction;

[0059] A torque control module, which controls the driving torque and braking torque of the vehicle in stages based on the comfortable acceleration and the critical vehicle speed until the vehicle stops or starts on the slope;

[0060] The comfortable acceleration A 舒适 is the maximum value that will not cause jerks during parking or starting. The parking process is negative, and the starting process is positive, and |A 舒适 | < |A max |, and the value of A 舒适 is set according to empirical values, and A max is the maximum deceleration allowed by the cruise control function;

[0061] The definition of the critical vehicle speed V 2 is as follows: Assuming that the braking system starts to intervene from an acceleration of 0 until the vehicle reaches A max in a time of T, there is an acceleration change threshold K, the acceleration from 0 to A max is in a time of T, the acceleration at any time t is A = K * t, and the safety factor C controlled by the braking system, then and V 2 > V 1 ,V 1 is the critical wheel speed, that is, the wheel speed that can only overcome the elastic deformation of the tire and the deformation of the suspension and does not cause the vehicle to move.

[0062] In a third aspect, the present invention further provides an assisted driving system. The assisted driving system realizes the torque control of the vehicle to stop or start on a slope through the torque control method for an electric vehicle to park and start on a slope according to the first aspect of the present invention.

[0063] The beneficial effects of the present invention are as follows: According to different scenarios of ramp parking and starting, the torque distribution during the parking and starting processes of the vehicle is controlled in a refined manner by dividing the scenarios and stages. The deceleration control before parking is continuous, the deceleration before parking is small, the braking force after parking can maintain parking, the speed change at the starting moment is small, and the acceleration control is continuous. It can well solve the problems of vehicle rollback and jerks encountered by the assisted driving system during ramp parking and starting, and improve the assisted driving experience and technical level. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a schematic flow chart of a torque control method for an electric vehicle's ramp parking and starting provided by an embodiment of the present invention;

[0065] Figure 2 It is a schematic flow chart of an uphill parking control strategy provided by an embodiment of the present invention;

[0066] Figure 3 It is a schematic flow chart of an uphill starting control strategy provided by an embodiment of the present invention;

[0067] Figure 4 It is a schematic flow chart of a downhill parking control strategy provided by an embodiment of the present invention;

[0068] Figure 5 It is a schematic flow chart of a downhill starting control strategy provided by an embodiment of the present invention;

[0069] Figure 6 It is a schematic structural diagram of a torque control device for an electric vehicle's ramp parking and starting provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0070] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0071] As Figure 1 shown, an embodiment of the present invention provides a torque control method for an electric vehicle's ramp parking and starting, including the following steps:

[0072] S1. Obtain the current state information of the electric vehicle, where the state information includes the current driving parameters of the vehicle, the current ramp value where the vehicle is located, and the ramp direction; the current state information of the electric vehicle can be obtained through various devices such as the chassis braking control system, the IMU of the assisted driving system, and the high-precision map, without involving additional devices and methods.

[0073] S2. Based on the comfortable acceleration and the critical vehicle speed, control the driving torque and the braking torque of the vehicle in stages until the vehicle stops or starts on the ramp;

[0074] The comfortable acceleration A舒适 is the maximum value that does not cause jerks during parking or starting. The parking process is negative, and the starting process is positive, and |A 舒适 |<|A max |, A 舒适 is set according to empirical values, and A max is the maximum deceleration allowed by the cruise control function;

[0075] The critical vehicle speed V 2 is defined as follows: Assume that the braking system starts to intervene from an acceleration of 0 until the vehicle reaches A max in a time of T, there is an acceleration change threshold K, and the acceleration from 0 to A max in the time of T, the acceleration at any time t is A = K * t, and the safety factor C controlled by the braking system, then and V 2 >V 1 ,V 1 is the critical wheel speed, that is, the wheel speed that can only overcome the elastic deformation of the tire and the deformation of the suspension and does not cause the vehicle to move.

[0076] Since the vehicle model is set as a non-rigid body considering the elastic deformation of the tire and the suspension during parking or starting, there is a critical wheel speed V 1 . This critical wheel speed can only overcome the elastic deformation of the tire and the deformation of the suspension and cannot cause the vehicle to move, that is, the vehicle does not move when the wheel rotates slightly. This value can be obtained through a certain amount of test data of actual vehicle starting and parking, and usually V 1 <1 Km / h.

[0077] When there is a need for parking or starting, different braking force and driving force control strategies are formulated according to four different working conditions: uphill parking, uphill starting, downhill parking, and downhill starting.

[0078] The uphill parking control strategy is as Figure 2 shown.

[0079] After receiving the parking demand, according to the vehicle parameters, obtain the current vehicle speed V and the current moment acceleration value A, and calculate the ramp parking braking force demand F 制 under the current ramp, the maximum deceleration A 滑 that can be generated by free sliding on the uphill ramp, and the maximum deceleration A max allowed by the cruise control function; further judgment

[0080] a) If A > 0, then enter S001-3;

[0081] b) If A < 0 and A 滑 <A max, then enter S001-1, and at this time the driving force must be greater than 0;

[0082] c) If A < 0 and A 滑 > A max , then enter S001-2.

[0083] S001-1, the braking force does not intervene, the driving force decays, and the control target is to reach A max with the acceleration change rate less than the threshold K, perform PID control on the decay of the driving force, and judge the vehicle speed and acceleration in real time,

[0084] a) If A > A max and V > V 2 , then loop and execute S001-1;

[0085] b) If A = A max and V > V2, which means the vehicle speed is still relatively high and has not reached the critical speed before stopping, then enter S002-1;

[0086] c) If V 1 < V ≤ V 2 , at this time the vehicle has reached the critical vehicle speed, and the acceleration needs to be maintained at A 舒适 , enter S003-1;

[0087] d) If V ≤ V 1 , at this time the vehicle has reached the critical vehicle speed, and the braking force needs to be increased rapidly, then enter S004-1.

[0088] S002-1, the braking force does not intervene, the driving force is maintained, and the vehicle decelerates with an acceleration of A max , and further judge the vehicle speed during this process:

[0089] If V > V 2 , then loop and execute S002-1;

[0090] If V = V 2 , then interrupt S002-1 and enter S003-1;

[0091] S003-1, the braking force does not intervene, the driving force increases, and the vehicle speed drops to V 1 before, and the acceleration changes from A max to A 舒适 with the acceleration change rate less than the threshold K as the control target, perform PID control on the intervention of the braking force, and when the vehicle speed reaches V 1 , enter S004-1;

[0092] S004-1, the braking force increases to the maximum braking capacity (F 制+(Current driving force) to ensure that the vehicle can achieve ramp parking without rolling back. After the braking force arrives, the driving force is cut off, and the uphill parking ends;

[0093] S001-2, the braking force does not intervene, and the driving force decays to 0 until the acceleration value reaches A 滑 And the acceleration change rate is less than the threshold K as the control target, and PID control is performed on the decay of the driving force. When this process is normally completed, the theoretical acceleration of the vehicle A = A 滑 , furthermore, during this process, the vehicle speed and acceleration are judged in real time:

[0094] a) If V > V 2 And A > A 滑 , then loop to execute S001-2;

[0095] b) If V > V 2 And A ≤ A 滑 , the driving force has decayed to 0 but the vehicle speed is still relatively high, and the deceleration needs to be further increased to A max , then interrupt S001-2 and enter S002-2;

[0096] c) If V ≤ V 2 , at this time the vehicle has entered the critical vehicle speed and can stop according to a gentle deceleration, then further judge the acceleration when V ≤ V 2 If the acceleration A < A 舒适 , then interrupt S001-2 and enter S002-3, the driving force increases, and the acceleration is controlled at A 舒适 ; If the acceleration A > A 舒适 , then interrupt S001-2 and enter S002-4, the driving force continues to decay, and the acceleration is controlled at A 舒适 ;

[0097] d) If V < V 1 , the vehicle has entered the critical vehicle speed of being stationary, and the braking force needs to intervene quickly for braking. Interrupt S001-2 and enter S003-3 to maintain parking.

[0098] S002-2, the braking force increases, and the driving force remains disconnected, until the acceleration value reaches A max And the acceleration change rate is less than the threshold K 1 As the control target, PID control is performed on the intervention of the braking force, and the vehicle speed and acceleration are judged in real time:

[0099] a) If V > V 2 , then loop to execute S002-2,

[0100] b) If V = V 2 , the vehicle has reached the critical vehicle speed for parking, and the acceleration needs to be controlled at A 舒适, then interrupt S002-2 and enter S003-2; K 1 <K;

[0101] S003-2, brake force attenuation, driving force following adjustment, to reach V at speed V 1 Before that, change the acceleration from A max to A 舒适 and the acceleration change rate does not exceed K as the control target, perform PID control on the attenuation of the brake force. In this stage, it is possible that the acceleration does not reach A when the brake force is 0 舒适 , after the brake force is reduced to 0, the driving force needs to intervene. During this process, judge the vehicle speed at any time. When the vehicle speed V = V 1 , interrupt S003-2 and enter S004-2;

[0102] S004-2, instantaneously increase the brake force to (F 制 + current driving force), after the brake force reaches, release the driving force, maintain the ramp parking without rolling back, and the uphill parking ends;

[0103] S002-3, the brake force does not intervene, the driving force increases, to reach V at speed V 1 Before that, control the acceleration at A 舒适 and the acceleration change rate is less than K 1 as the control target, perform PID control on the increase of the driving force. After the acceleration reaches A 舒适 , the driving force is maintained. After this process ends, judge the vehicle speed in real time. When V ≤ V 1 , enter S003-3;

[0104] S002-4, the brake force increases, the driving force is cut off, to reach V at speed V 1 Before that, control the acceleration at A 舒适 and the acceleration change rate is less than K 1 as the control target, perform PID control on the brake force. After the acceleration reaches A 舒适 , the brake force is maintained. After this process ends, judge the vehicle speed in real time. When V ≤ V 1 , enter S003-3;

[0105] S003-3, increase the brake force to (F 制 + current driving force) according to the maximum brake force, ensure that the vehicle realizes ramp parking without rolling back, and cut off the driving force after the brake force reaches, and the uphill parking ends.

[0106] Uphill start control strategy, as Figure 3 shown.

[0107] Obtain the current vehicle speed V and the current acceleration value A in real time; after receiving the start demand, enter S101;

[0108] S101, Brake force fades, driving force increases. During any moment in this stage, |decreased brake force| < |increased driving force|, and the difference in torque change increases linearly until the vehicle speed V > V 1 A starting trend is generated; the difference in torque change = ||increased driving force| - |decreased brake force||, where |·| represents taking the absolute value;

[0109] S102, The brake force fades to 0, and the driving force follows the adjustment (increases, remains constant, or decreases). At the initial state of this stage, there may be a brake force. The vehicle acceleration A reaches A 舒适 and the acceleration change rate is less than K, and the brake force must drop to 0 before the vehicle acceleration A reaches A 舒适 as the control target. PID adjustment is performed on the brake force and the driving force, and the difference between the driving force and the brake force conforms to a linear change trend; when the acceleration A reaches A 舒适 and the brake force is 0, if the vehicle speed V < V 2 , enter S103. If the vehicle speed V > V 2 , the uphill start ends.

[0110] S103, The brake force is 0, and the driving force increases. With the acceleration A reaching A max and the acceleration change rate being small and K as the control target, PID control is performed on the driving force. After the acceleration A reaches Amax, the driving force remains constant. During this process, the vehicle speed V is judged. If V < V 2 , maintain S103 until V ≥ V 2 , and the uphill start ends.

[0111] The downhill parking control strategy is as Figure 4 shown.

[0112] Calculate the ramp parking brake force demand F 制 for downhill and the maximum deceleration A max allowed by the cruise control function. Obtain the current vehicle acceleration A. If A > 0, enter the S201-1 stage. If A < 0, enter S201-2;

[0113] S201-1, The brake force increases, and the driving force decays. With the vehicle acceleration reaching 0, the driving force being 0, and the acceleration change rate being less than the threshold K as the control target, PID control is performed on the brake force and the driving force, and the absolute value of the difference between the brake force and the driving force ||increased brake force| - |decreased driving force|| conforms to a linear growth pattern and the driving force must drop to 0 before the acceleration A reaches 0. During this process, the acceleration and the vehicle speed are judged in real time. If A > 0, maintain S201-1. If A = 0 and V > V 2 , enter S202-1. If A = 0 and V ≤ V 2 , enter S203-2;

[0114] S202-1, the braking force increases and the driving force does not intervene, with the acceleration reaching A max Taking the control target as the acceleration change rate being less than the threshold K and the acceleration reaching A, perform PID control on the increase of the braking force, and the acceleration reaches A max After that, the braking force is maintained. During this process, the vehicle speed is judged in real time. If V > V 2 , maintain S202-1. If V ≤ V 2 , enter S203-1;

[0115] S203-1, the braking force decays and the driving force does not intervene, so as to control the deceleration at A 1 before the speed reaches V 舒适 and taking the control target as the deceleration change rate being less than the threshold K, control the decay of the braking force. During this process, the vehicle speed is judged in real time. If V > V 1 , maintain S203-1. If V ≤ V 1 , enter S204;

[0116] S201-2, the braking force increases and the driving force decays. Regardless of whether there is a driving force in the vehicle currently, in this stage, taking the vehicle deceleration reaching Amax, the driving force being 0, and the acceleration change rate being less than the threshold K as the control target, perform PID control on the braking force and the driving force, and the absolute value of the difference between the braking force and the driving force conforms to the linear growth law and the acceleration reaches A max Before that, the driving force must drop to 0. During this process, the vehicle speed is judged. If V > V 2 , maintain S201-2, continue to increase the acceleration or maintain A max for deceleration. If V ≤ V 2 , enter S202-2; The absolute value of the difference between the braking force and the driving force = || increased braking force | - | decreased driving force ||;

[0117] S202-2, the braking force decays and the driving force does not intervene, so as to control the acceleration at A 1 before the vehicle speed reaches V 舒适 as the control target, perform PID control on the decay of the braking force, and reach the acceleration A 舒适 After that, the braking force is maintained. During this process, the vehicle speed is judged in real time. If V > V 1 , maintain S201-2, continue to control the acceleration or maintain A 舒适 for deceleration; If V ≤ V 1 , enter S204;

[0118] S203-2, the braking force increases and the driving force does not intervene, so as to control the acceleration to A 1 before the speed becomes V 舒适And the control objective is that the acceleration change rate is less than the threshold K, and the acceleration reaches A 舒适 After that, the braking force is maintained and when the vehicle speed reaches V 1 Then it enters S204;

[0119] S204, the braking force is controlled at F 制 , maintaining parking, and the downhill parking ends.

[0120] The downhill start control strategy is as Figure 5 shown.

[0121] The pre - vehicle conditions before downhill start are that the vehicle is stationary, the driving force is greater than 0, and the braking force is greater than or equal to 0.

[0122] After receiving the start demand, first calculate the minimum parking braking force F required under the current slope 制 and the maximum acceleration A allowed by the cruise control function max , and enter S301.

[0123] S301: Release the braking force, cut off the driving force, quickly release the braking force to near F 制 and then slowly decay it, so that the vehicle only relies on the gravity component to overcome the braking force and rolling resistance to reach the critical vehicle speed. There are the following three situations during the release of the braking force:

[0124] a) During the release of the braking force, the wheel speed is less than V 1 , and continue to release the braking force maintaining the S301 braking force;

[0125] b) During the release of the braking force, the wheel speed reaches V 1 , and the vehicle reaches the critical vehicle speed and enters S302 - 1;

[0126] c) After the braking force is released, the wheel speed is less than V 1 , and the gravity component of the vehicle on the current slope is not enough to overcome the wheel deformation and rolling resistance to make the vehicle reach the critical vehicle speed, and enter S302 - 2.

[0127] S302 - 1: Decay the braking force, cut off or increase the driving force, and use the vehicle speed to reach V 2 before reaching an acceleration of A 舒适 and the acceleration change rate is less than K as the control objective to perform PID control on the braking force and driving force, │|reduce the braking force|+|increase the driving force|│ conforms to the linear growth law, and when the acceleration reaches A 舒适 maintain the current braking force or driving force, and judge the vehicle speed during this process.

[0128] S302 - 2: Slowly increase the driving force to make the wheel speed reach the critical wheel speed V 1 .

[0129] S303: Increase the driving force until the vehicle speed reaches V 2 and control the acceleration to A before reaching it 舒适 and control the increase of the driving force with the control target that the change rate does not exceed the threshold K to reach A 舒适 After reaching it, keep the driving force

[0130] After S302-1 and S303 are executed and the vehicle speed reaches V 2 the downhill start ends

[0131] As a preferred embodiment, if the electric vehicle is equipped with an air suspension, the method further includes, when switching between the working conditions of uphill parking, uphill start or downhill start, downhill parking, adjusting the height and hardness of the air suspension to increase the vehicle rigidity and reduce the jitter during the switching of the vehicle motion state

[0132] As a preferred embodiment, if the seat belt of the electric vehicle is equipped with an electric retractor, the method further includes, when switching between the working conditions of uphill parking, uphill start or downhill start, downhill parking, adjusting the seat belt pre-tension degree to slow down the driver's subjective feeling of the vehicle motion state switching

[0133] As Figure 6 shown, the embodiment of the present invention further provides a torque control device for an electric vehicle to start on a slope, including:

[0134] A data acquisition module, configured to acquire the current state information of the electric vehicle, where the state information includes the current driving parameters of the vehicle, the current slope value of the vehicle, and the slope direction

[0135] A torque control module, based on the comfortable acceleration and the critical vehicle speed, controls the driving torque and the braking torque of the vehicle in stages until the vehicle stops or starts on the slope

[0136] On the basis of the above embodiments, the present invention further provides an assisted driving system, and the assisted driving system realizes the torque control for the vehicle to stop or start on a slope through the above method

[0137] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments and all changes and modifications falling within the scope of the present invention

[0138] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. In this way, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations

Claims

1. A torque control method for an electric vehicle to start on a ramp during parking, characterized in that, it includes: Obtain the current state information of the electric vehicle, where the state information includes the current driving parameters of the vehicle, the current ramp value where the vehicle is located, and the ramp direction; Based on the comfortable acceleration and the critical vehicle speed, control the driving torque and braking torque of the vehicle in stages until the vehicle stops or starts on the ramp; The comfortable acceleration A 舒适 is the maximum value that does not cause jerks during parking or starting. It is negative during the parking process and positive during the starting process, and |A 舒适 | < |A max |, and the value of A 舒适 is set according to empirical values. A max is the maximum deceleration allowed by the cruise control function; The critical vehicle speed V 2 is defined as follows: Assume that the braking system starts to intervene from an acceleration of 0 until the vehicle reaches A max in a time of T, with an acceleration change threshold K, the acceleration from 0 to A max in a time of T, the acceleration at any time t is A = K * t, and the safety factor C controlled by the braking system, then and V 2 > V 1 , V 1 is the critical wheel speed, that is, the wheel speed that can only overcome the elastic deformation of the tire and the deformation of the suspension and does not cause the vehicle to move.

2. The method according to claim 1, characterized in that, it further includes classifying the ramp parking start into four different working conditions: uphill parking, uphill start, downhill parking, and downhill start according to the parking or start requirements and the current state information.

3. The method according to claim 2, characterized in that, The control of the driving torque and braking torque of the vehicle in stages based on the comfortable acceleration and the critical vehicle speed until the vehicle stops or starts on the ramp includes: based on the comfortable acceleration and the critical vehicle speed, for the uphill parking working condition, control the driving torque and braking torque of the vehicle in stages until the vehicle stops on the ramp, which specifically includes the following content: Obtain the current vehicle speed V and the acceleration value A at the current moment, and calculate the ramp parking braking force requirement F under the current ramp according to the following-stop target position and the road surface adhesion coefficient 制 , the maximum deceleration A that can be generated by free sliding on the uphill ramp 滑 and the maximum deceleration A allowed by the cruise control function max ; if A > 0, enter S001-3, if A < 0 and A 滑 < A max , enter S001-1, if A < 0 and A 滑 > A max , enter S001-2 S001-1, the braking force does not intervene, the driving force decays, and the acceleration value reaches A max With the control objective that the acceleration change rate is less than the threshold K, perform PID control on the decay of the driving force, and judge the vehicle speed and acceleration in real time. If A > A max and V > V 2 , then loop and execute S001-1. If A = A max and V > V2, then enter S002-1. If V 1 < V ≤ V 2 , then enter S003-1. If V ≤ V 1 , then enter S004-1; S002-1, the braking force does not intervene, the driving force is maintained, and the vehicle decelerates at an acceleration of A max If V > V 2 , then loop to execute S002-1. If V = V 2 , then interrupt S002-1 and enter S003-1; S003-1, the braking force does not intervene, the driving force increases, and the vehicle speed drops to V 1 front, the acceleration changes from A max to A 舒适 and the control target is that the acceleration change rate is less than the threshold value K, and PID control is performed on the intervention of the braking force. When the vehicle speed reaches V 1 it enters S004-1; S004-1, the braking force increases to F according to the maximum braking capacity 制 + the current driving force to ensure that the vehicle can achieve hill parking without rolling back. After the braking force reaches, the driving force is cut off and the uphill parking ends; S001-2, the braking force does not intervene, the driving force decays to 0, and the acceleration value reaches A 滑 With the control objective that the acceleration change rate is less than the threshold K, PID control is performed on the decay of the driving force, and the vehicle speed and acceleration are judged in real time If V > V 2 and A > A 滑 , then loop and execute S001-2 If V > V 2 and A ≤ A 滑 , then interrupt S001-2 and enter S002-2 If V ≤ V 2 , then further determine the acceleration when V ≤ V 2 . If the acceleration A < A 舒适 , then interrupt S001-2 and enter S002-3; if the acceleration A > A 舒适 , then interrupt S001-2 and enter S002-4. If V < V 1 , interrupt S001-2 and enter S003-3; S002-2, the braking force increases, the driving force remains disconnected, and the acceleration value reaches A max And the PID control is performed on the intervention of the braking force with the control objective that the acceleration change rate is less than the threshold K, and the vehicle speed and acceleration are judged in real time. If V > V 2 , then S002-2 is looped. If V = V 2 , then S002-2 is interrupted and S003-2 is entered; S003-2, braking force attenuation, driving force following adjustment, to reach V at speed V 1 Before, change the acceleration from A max to A 舒适 And with the control objective that the acceleration change rate does not exceed K, perform PID control on the attenuation of the braking force. When the vehicle speed V = V 1 Interrupt S003-2 and enter S004-2; S004-2, the braking force instantaneously increases to F 制 + the current driving force. After the braking force is reached, the driving force is released to maintain hill parking without rolling back, and the uphill parking ends; S002-3, the braking force does not intervene, the driving force increases, and it reaches V at speed V 1 First, control the acceleration at A 舒适 And with the control objective that the acceleration change rate is less than K, perform PID control on the increase of the driving force. When V ≤ V 1 , enter S003-3; S002 - 4, braking force increases, driving force is cut off, reaching V at speed V 1 Previously, control the acceleration at A 舒适 And the acceleration change rate is less than K 1 Taking this as the control target, perform PID control on the braking force. When V ≤ V 1 , enter S003 - 3; K 1 < K; S003-3, the braking force increases to F according to the maximum braking force 制 + the current driving force to ensure that the vehicle can achieve uphill parking without rolling back. After the braking force reaches, the driving force is cut off and the uphill parking ends.

4. The method according to claim 2, characterized in that, The control of the driving torque and braking torque of the vehicle in stages based on the comfortable acceleration and the critical vehicle speed until the vehicle stops or starts on the ramp includes: based on the comfortable acceleration and the critical vehicle speed, for the uphill start working condition, control the driving torque and braking torque of the vehicle in stages until the vehicle starts on the ramp, which specifically includes the following content: Real-time obtain the current vehicle speed V and the acceleration value A at the current moment; after receiving the start requirement, enter S101; S101, Brake force fades, driving force increases. During any period of this stage, |decreased brake force| < |increased driving force|, and the torque change difference increases linearly until the vehicle speed V > V 1 A starting trend is generated; torque change difference = ||increased driving force| - |decreased brake force||, where |·| represents taking the absolute value; S102, the braking force decays to 0 and the driving force follows the adjustment so that the vehicle acceleration A reaches A 舒适 , the acceleration change rate is less than K and before the vehicle acceleration A reaches A 舒适 , taking the braking force dropping to 0 as the control target before the vehicle acceleration A reaches A, performing PID adjustment on the braking force and the driving force, and the difference between the driving force and the braking force conforms to a linear change trend; when the acceleration A reaches A 舒适 and the braking force is 0, if the vehicle speed V < V 2 , enter S103, if the vehicle speed V > V 2 the uphill start ends S103, the braking force is 0, the driving force increases, and it reaches A at an acceleration of A max And the control objective is that the acceleration change rate is less than K, and PID control is performed on the driving force. After the acceleration A reaches Amax, the driving force is maintained. During this process, the vehicle speed V is judged. If V < V 2 Maintain S103 until V ≥ V 2 , the uphill start ends.

5. The method according to claim 2, characterized in that, The control of the driving torque and braking torque of the vehicle in stages based on the comfortable acceleration and the critical vehicle speed until the vehicle stops or starts on the ramp includes: based on the comfortable acceleration and the critical vehicle speed, for the downhill parking working condition, control the driving torque and braking torque of the vehicle in stages until the vehicle stops on the ramp, which specifically includes the following content: Calculate the ramp parking braking force requirement F for going downhill 制 and the maximum deceleration A allowed by the cruise control function max , obtain the current vehicle acceleration A. If A > 0, enter the S201-1 stage; if A < 0, enter S201-2; S201-1. The braking force increases and the driving force decays. With the vehicle acceleration reaching 0, the driving force being 0, and the acceleration change rate being less than the threshold K as the control target, PID control is performed on the braking force and the driving force. Moreover, the absolute value of the difference between the braking force and the driving force, ||increased braking force| - |decreased driving force||, conforms to the linear growth law, and the driving force must drop to 0 before the acceleration A reaches 0. During this process, the acceleration and vehicle speed are judged in real time. If A > 0, S201-1 is maintained. If A = 0 and V > V 2 , enter S202-1. If A = 0 and V ≤ V 2 , enter S203-2; S202-1, the braking force increases, the driving force does not intervene, and the acceleration reaches A max With the control target of the acceleration change rate being less than the threshold K and the acceleration reaching A, PID control is performed on the increase of the braking force max After that, the braking force is maintained. During this process, the vehicle speed is judged in real time. If V > V 2 , S202-1 is maintained. If V ≤ V 2 , enter S203-1; S203-1, Brake force attenuation, driving force not involved, to control the deceleration at A before the speed reaches V 1 and the control target is that the deceleration change rate is less than the threshold K, control the attenuation of the brake force. During this process, judge the vehicle speed in real time. If V > V 舒适 , maintain S203-1. If V ≤ V 1 , enter S204; 1 ​ S201-2, the braking force increases and the driving force decays. Regardless of whether there is a driving force on the vehicle currently, in this stage, the control objective is that the vehicle deceleration reaches Amax, the driving force is 0, and the acceleration change rate is less than the threshold K. PID control is performed on the braking force and the driving force, and the absolute value of the difference between the braking force and the driving force conforms to the linear growth law and the acceleration reaches A max Before that, the driving force must be reduced to 0. During this process, the vehicle speed is judged. If V > V 2 , maintain S201-2, continue to increase the acceleration or maintain A max for deceleration. If V ≤ V 2 , enter S202-2; the absolute value of the difference between the braking force and the driving force = ||the increased braking force| - |the decreased driving force||; S202-2, Brake force attenuation, driving force not involved, with the vehicle speed reaching V 1 Before that, control the acceleration at A 舒适 As the control target, perform PID control on the attenuation of the brake force to achieve the acceleration A 舒适 After that, maintain the brake force. During this process, continuously judge the vehicle speed. If V > V 1 , maintain S201-2, continue to control the acceleration or maintain A 舒适 to decelerate; if V ≤ V 1 , enter S204; S203-2. The braking force increases and the driving force does not intervene, with the speed becoming V. 1 Previously, the acceleration was controlled to A. 舒适 And the control target is that the acceleration change rate is less than the threshold K, and the acceleration reaches A. 舒适 After that, the braking force is maintained and when the vehicle speed reaches V. 1 Then it enters S204. S204, Brake force is controlled at F 制 , Maintain parking, downhill parking ends.

6. The method according to claim 2, characterized in that, The control of the driving torque and braking torque of the vehicle in stages based on the comfortable acceleration and the critical vehicle speed until the vehicle stops or starts on the ramp includes: based on the comfortable acceleration and the critical vehicle speed, for the downhill start working condition, control the driving torque and braking torque of the vehicle in stages until the vehicle starts on the ramp, which specifically includes the following content: Before starting on a downhill slope, the previous conditions of the vehicle are that the vehicle is stationary, the driving force is greater than 0, and the braking force is greater than or equal to 0; after receiving the start requirement, calculate the minimum parking braking force F required under the current slope 制 and the maximum acceleration A allowed by the cruise control function max , enter S301; S301, Release the braking force, cut off the driving force, quickly release the braking force to F 制 After approaching, slowly decay it so that the vehicle only relies on the gravity component to overcome the braking force and rolling resistance to reach the critical speed V 2 , During the process of releasing the braking force, there are the following three situations: a) During the braking force release process, the wheel speed is less than V 1 , maintain the braking force release of S301; b) During the braking force release process, the wheel speed reaches V 1 , and the vehicle reaches the critical vehicle speed V 2 to enter S302-1; c) After the braking force is released and the wheel speed is less than V 1 , the gravitational component of the vehicle on the current slope is not sufficient to overcome the wheel deformation and rolling resistance to make the vehicle reach the critical speed V 2 , enter S302-2; S302-1, Brake force attenuation, drive force cut-off or increase, until the vehicle speed reaches V 2 Before that, control the acceleration to A 舒适 And with the control objective that the acceleration change rate is less than K, perform PID control on the brake force and drive force, ||Reduce the brake force| + |Increase the drive force|| conforms to the linear growth law, and the acceleration reaches A 舒适 After that, maintain the current brake force or drive force, and judge the vehicle speed during this process; S302-2, the driving force increases slowly to make the wheel speed reach the critical wheel speed V 1 ; S303, the driving force increases until the vehicle speed reaches V 2 Previously, the acceleration is controlled to A 舒适 And with the control objective that the change rate does not exceed the threshold K, the increase of the driving force is controlled to reach A 舒适 After that, the driving force remains unchanged; After S302-1 and S303 are executed and the vehicle speed reaches V 2 the downhill start ends.

7. The method according to claim 1, characterized in that, The electric vehicle is equipped with an air suspension, and this method further includes adjusting the height and hardness of the air suspension when switching between the working conditions of uphill parking, uphill start, or downhill start, downhill parking to increase the vehicle rigidity and reduce the jitter during the switching of the vehicle motion state.

8. The method according to claim 1, characterized in that, The seat belt of the electric vehicle is equipped with an electric retractor, and the method further includes adjusting the pre-tightening degree of the seat belt when switching between the working conditions of uphill parking, uphill starting, downhill starting, and downhill parking, so as to mitigate the driver's subjective feeling of the vehicle's motion state switching.

9. A torque control device for an electric vehicle to park and start on a slope Characterized in that it includes: a data acquisition module for acquiring the current state information of the electric vehicle, where the state information includes the current driving parameters of the vehicle, the current slope value of the vehicle, and the slope direction; a torque control module for controlling the driving torque and braking torque of the vehicle in stages based on the comfortable acceleration and the critical vehicle speed until the vehicle stops or starts on the slope; The comfortable acceleration A 舒适 is the maximum value that does not cause jerks during parking or starting. It is negative during the parking process and positive during the starting process, and |A 舒适 | < |A max |, and the value of A 舒适 is set according to empirical values. A max is the maximum deceleration allowed by the cruise control function; The critical vehicle speed V 2 is defined as follows: Assume that the braking system starts to intervene from an acceleration of 0 until the vehicle reaches A max in a time T, with an acceleration change threshold K, the acceleration from 0 to A max in time T, the acceleration at any time t is A = K * t, and the safety factor C controlled by the braking system, then and V 2 > V 1 , V 1 is the critical wheel speed, that is, the wheel speed that can only overcome the elastic deformation of the tire and the deformation of the suspension without causing the vehicle to move.

10. An assisted driving system Characterized in that the assisted driving system realizes the torque control of the vehicle to stop or start on the slope through the torque control method for an electric vehicle to park and start on a slope according to any one of claims 1-8.

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