Method for steering system control for multiple advanced driving assistance scenarios

Abstract

The invention relates to the technical field of automobile steering control, in particular to a steering system control method for various advanced driving assistance scenes. Compared with the prior art, the use scenes that automatic parking is assisted, a driver is in the ring, the driver slips out of the hand and emergency avoidance is achieved; a target rack position requested by a vehicle upper computer is received, the electronic power steering system calculates the required motor torque through an internal controller, and transverse control response is achieved; the safety function of limiting the maximum rack speed of the steering system can meet the requirement of preventing the function safety target of excessive steering from being violated; when the driving auxiliary function is used, the requirements for turning angle following, smooth switching and comfortable hand feeling control in a man-machine co-driving scene can be met at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile steering control, and in particular to a method for controlling a steering system for multiple advanced driving assistance scenarios. Background Art

[0002] In recent years, China's advanced automobile assistance driving systems have developed rapidly. However, due to the expensive vehicle architecture and laws and regulations that have not yet been officially promulgated, the implementation of SAE L3 / L4 autonomous driving functions has been delayed. Currently, SAE L2 functions have become the mainstream of the market.

[0003] Common automatic parking functions, lane keeping functions, city / highway pilot assistance functions, and electronic power steering systems all need to cooperate with the host computer's instructions to execute the motor torque response and perform lateral movement of the vehicle. More and more vehicles are equipped with driver monitoring systems to ensure that the driver is still paying attention to the vehicle. In this case, the driver is allowed to take his hands off the wheel; with the increasing demand for human-machine co-driving, when the driving assistance function is in effect, if the driver wants to control the vehicle, he needs to have a better feel to control the steering of the vehicle. As part of the vehicle's active safety, the steering avoidance assist function requires the steering system to meet the requirements of functional safety while cooperating with large dynamic lateral movements.

[0004] CN114348112A discloses a vehicle steering control method suitable for semi-automatic driving scenarios, which uses a dual PID algorithm to perform an outer-loop PID calculation on the difference between the target rack position and the ESP rack position, and an inner-loop PID calculation on the difference between the current rack speed and the EPS rack speed to obtain the EPS torque.

[0005] CN117698701A discloses a human-machine co-driving method for an automatic parking system, which uses the difference between the target steering wheel angle and the actual steering wheel angle or the large angle or fast rate of intervention to determine whether the driver has intervened in the steering wheel.

[0006] The adaptive control method of the human-machine co-driving steering system disclosed in CN116873034A is based on the existing angle closed-loop control strategy, superimposed with the judgment of the human-machine co-driving state, and coordinates the calculation of the output of the basic assist torque and the angle closed-loop control torque as the total motor torque.

[0007] In summary, the existing published patents for angle closed-loop control and human-machine co-driving are either based on the existing EPS basic function torque output superimposed on the torque of the dual PID angle control algorithm. When the steering rack is moving, functions related to the angle or angular velocity, such as active return function, stability function, inertia compensation function, etc., will output torque, causing the EPS angle following performance to be negatively affected by the basic functions; or the smoothness of the hand feel switching when the driver intervenes is not considered, or the smoothness of the driver's intervention is difficult to adjust due to the superimposed algorithm.

[0008] Therefore, it is necessary to design a steering system control method for a variety of advanced driving assistance scenarios, which is independent of the basic EPS function and can eliminate the influence of the torque output of the basic EPS function in intelligent driving scenarios or human-machine co-driving. The rack position-hand torque control algorithm can simultaneously meet the corner following, smooth switching and comfortable hand feel control in the human-machine co-driving scenario. Summary of the invention

[0009] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for steering system control for a variety of advanced driving assistance scenarios, which is independent of the basic EPS function and can eliminate the influence of the torque output of the basic EPS function in intelligent driving scenarios or human-machine co-driving; the rack position-hand torque control algorithm can simultaneously meet the corner following, smooth switching and comfortable hand-feel control in the human-machine co-driving scenario.

[0010] In order to achieve the above-mentioned object, the present invention is a method for controlling a steering system for a variety of advanced driving assistance scenarios, comprising the following steps: Step 1, an electric power steering system controller acquires the driving assistance function status, target wheel angle or target steering wheel angle, vehicle speed status, and vehicle speed signal of a vehicle controller in real time, and uses them as inputs to a steering control module; Step 2, the steering control module receives the system status, angle sensor status, current rack position, rotor speed, and torsion bar torque signal of the electric power steering system controller in real time; Step 3, when the system status, angle sensor status, and vehicle speed status of the electric power steering system controller are all normal, and the vehicle speed is less than the maximum standard When the set value and the torsion bar torque are less than the maximum calibration value, the module system state machine is in a waiting state. After the vehicle controller sends a function enable signal, the controller enters the intelligent driving mode and continues with steps 4 and 10. When the system state, the angle sensor state, and the vehicle speed state of the electric power steering system controller are abnormal, or the vehicle speed is greater than the maximum calibration value, or the torsion bar torque is greater than the maximum calibration value, the module system state machine is in an abnormal state and maintains the human driving mode; Step 4, the electric power steering system converts the target wheel angle or the target steering wheel angle requested by the host computer into the target rack position: If the host computer requests the target wheel angle A1, the target rack position L1= iw×A1×ic / 360, if the upper computer requests the target steering wheel angle A2, the target rack position L1= A2×ic / 360, iw is the ratio of the steering wheel angle to the steering wheel deflection angle on the same side of the steering wheel, and ic is the linear angle transmission ratio of the steering system; Step 5, calculate the rack position difference = target rack position - current rack position of the steering gear; Step 6, perform a two-dimensional table lookup according to different vehicle speeds and rack position differences to obtain the target hand torque; Step 7, calculate the target total hand torque = target hand torque + active inertia module output hand torque + intermediate sense module output hand torque; Step 8, calculate the motor torque of the hand force controller according to the target total hand torque and torsion bar torque; Step 9, superimpose the motor torque of the hand force controller and the torque of the rack speed limit module to obtain the total intelligent driving function torque; Step 10, the motor torque of the basic steering module in human driving mode and the intelligent driving function torque in intelligent driving mode are switched through the gain regulator.

[0011] The two-dimensional table lookup forms a calibrable curve through the rack position difference and the vehicle speed, and searches for the target hand torque from the curve.

[0012] After the intelligent driving mode is activated, when the torsion bar torque is greater than the maximum set value and the maintenance time exceeds the maximum set time value, it is judged that the driver is encountering an emergency scenario or has a strong intention to take over the steering wheel, and the intelligent driving mode is exited and the human driving mode is entered; when the steering wheel torque is less than or equal to the maximum calibration value, it is judged that the driver has no intention to take over, the intelligent driving mode is kept activated, and the human-machine co-driving mode is in progress.

[0013] After the intelligent driving mode is activated, if any of the system status, steering angle sensor status, and vehicle speed status of the electric power steering system controller is abnormal, the intelligent driving mode will be exited and the manual driving mode will be entered.

[0014] The motor torque M1 of the hand force controller is calculated as follows: Kp×(T1-T2)+Ki×∫(T1-T2)dt+Kd×{(T1-T2)- (T1'-T2')}, where Kp is the torque proportional parameter, Ki is the torque integral parameter, T1 is the target total hand torque, T2 is the actual torsion bar torque, T1' is the target total hand torque of the previous cycle, and T2' is the actual torsion bar torque of the previous cycle.

[0015] The step 9 includes the following steps: step 9a, the controller obtains the vehicle speed value, the intelligent driving mode and the rack speed value of the steering gear; step 9b, obtains the rack speed limit under the current calibration curve; step 9c, compares the current rack speed and the rack speed limit, if the current rack speed is less than the rack speed limit, no processing is performed; if the current rack speed is greater than the rack speed limit, the difference between the current rack speed and the safety rack speed is processed by PI loop to obtain the safety motor torque M2=Kp×(V1-V2)+Ki×∫(V1-V2) dt after the rack speed is limited, Kp is the torque proportional parameter, Ki is the torque integral parameter, V1 is the limited target rack speed, and V2 is the actual steering gear rack speed.

[0016] In the step 10, after the intelligent driving mode is activated, the intelligent driving torque increases with a gradient of 0.01 Nm / ms to the total intelligent driving function torque, and the human driving torque decreases with a gradient of 0.02 Nm / ms to 0; after the intelligent driving mode is exited, the human driving torque increases with a gradient of 0.01 Nm / ms to the motor torque, and the intelligent driving torque decreases with a gradient of 0.02 Nm / ms to 0.

[0017] Compared with the prior art, the present invention meets the usage scenarios of assisted automatic parking, driver-in-the-loop, driver hands-off, and emergency avoidance; accepts the target rack position requested by the vehicle host computer, and the electronic power steering system calculates the required motor torque through an internal controller to achieve lateral control response; the safety function of the maximum rack speed limit of the steering system can meet the functional safety goal of avoiding oversteering; when the driving assistance function is in effect, it can simultaneously meet the corner following, smooth switching, and comfortable hand-feel control in the human-machine co-driving scenario. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The diagram is a schematic diagram of the interaction between the EPS and the host computer in the advanced driving assistance scenario of the present invention.

[0019] Figure 2It is a general block diagram of the rack position-hand force control of the steering system for various advanced driver assistance scenarios of the present invention.

[0020] Figure 3 This is a calculation logic diagram of the intermediate sense nominal hand force of the present invention.

[0021] Figure 4 This is a calculation logic diagram of the active inertia nominal hand force of the present invention.

[0022] Figure 5 This is a calculation logic diagram of the rack speed limit of the EPS of the present invention.

[0023] Figure 6 The rack speed safety limit calibration curve is allowed by different intelligent driving functions of the present invention. DETAILED DESCRIPTION

[0024] The present invention will now be further described with reference to the accompanying drawings.

[0025] See also Figure 1 In the advanced driving assistance scenario, the host computer uses radar / camera to monitor the environment, plan the vehicle path, and calculate the target wheel angle; EPS first converts the wheel angle into the target rack position, and calculates the torque in the intelligent driving mode through the rack position-hand torque algorithm, which is output to the motor through FOC. EPS moves the rack and the vehicle moves laterally to reach the target trajectory.

[0026] The present invention is a method for controlling a steering system for various advanced driver assistance scenarios, comprising the following steps: Step 1: The electric power steering system controller obtains the driving assistance function status, target wheel angle or target steering wheel angle, vehicle speed status, and vehicle speed signal of the vehicle controller in real time, and uses them as input to the steering control module.

[0027] Step 2: The steering control module receives the system status, the steering angle sensor status, the current rack position, the rotor speed and the torsion bar torque signal of the electric power steering system controller in real time.

[0028] Step 3. When the system state, steering angle sensor state, and vehicle speed state of the electric power steering system controller are all normal, and the vehicle speed is less than the maximum calibration value, and the torsion bar torque is less than the maximum calibration value, the module system state machine is in a waiting state. After the vehicle controller sends a function enable signal, the controller enters the intelligent driving mode and continues with steps 4 and 10. When any of the system state, steering angle sensor state, and vehicle speed state of the electric power steering system controller is abnormal, or the vehicle speed is greater than the maximum calibration value, or the torsion bar torque is greater than the maximum calibration value, the module system state machine is in an abnormal state and maintains the human driving mode.

[0029] Step 4: The electric power steering system converts and calculates the target wheel angle or target steering wheel angle requested by the host computer into a target rack position.

[0030] If the host computer requests the target wheel angle A1, the target rack position L1 = iw×A1×ic / 360. If the host computer requests the target steering wheel angle A2, the target rack position L1 = A2×ic / 360. iw is the ratio of the steering wheel angle to the steering wheel deflection angle on the same side of the steering wheel. iw is provided by the OEM. ic is the line angle transmission ratio of the steering system. ic is a mechanical parameter with the unit of mm / rev.

[0031] Step 5, calculate the rack position difference = target rack position - current rack position of the steering gear.

[0032] See also Figure 2 In the driver's hands-off scenario, the current torsion bar torque is close to 0. Through the hand force PID control loop, the target hand force approaches the torsion bar torque of 0, and the angle difference approaches 0, so that the actual rack position approaches the target rack position.

[0033] When the driver intervenes in driving the vehicle, the steering angle difference increases as the driver intervenes in steering, and the target hand torque also increases linearly through the lookup table. Through the hand force PID control loop, the actual hand force is close to the torsion bar torque, and the actual hand force approaches the target hand force, creating a change in the driver's hand torque with the steering angle difference.

[0034] Step 6: Perform a two-dimensional table lookup based on different vehicle speeds and rack position differences to obtain the target hand torque.

[0035] The two-dimensional lookup table forms a calibrable curve through the rack position difference and vehicle speed, and finds the target hand torque from the curve, such as Figure 2 The curve shown.

[0036] Step 7, calculate the target total hand torque = target hand torque + active inertia module output hand torque + intermediate sense module output hand torque.

[0037] The center-feel module is designed to create a center-zone steering force at different vehicle speeds. Figure 3 The torque that changes with the turning angle and the factor that changes with the vehicle speed are multiplied to get the intermediate nominal hand force. The turning angle ranges from 0 to 6 degrees. The larger the turning angle, the greater the torque value; the higher the vehicle speed, the greater the torque factor.

[0038] The active inertia module is used to change the inertia of the steering system. Figure 4 , the rotor inertia and the inertia torque that changes with the torsion bar torque and the factor that changes with the vehicle speed are multiplied to get the inertia nominal hand force. The greater the hand force, the smaller the torque value; the higher the vehicle speed, the greater the torque factor.

[0039] Step 8, calculate the motor torque of the hand force controller according to the target total hand torque and the torsion bar torque. The motor torque M1 of the hand force controller is M1=Kp×(T1-T2)+Ki×∫(T1-T2)dt+Kd×{(T1-T2) - (T1'-T2')}, where Kp is the torque proportional parameter, Ki is the torque integral parameter, T1 is the target total hand torque, T2 is the actual torsion bar torque, T1' is the target total hand torque of the previous cycle, and T2' is the actual torsion bar torque of the previous cycle.

[0040] Step 9: Superimpose the motor torque of the hand force controller and the torque of the rack speed limit module to obtain the total intelligent driving function torque.

[0041] The module is designed for safety considerations. In different intelligent driving modes, the rack speed limit should be different.

[0042] See also Figure 5 , step 9 includes the following steps: step 9a, the controller obtains the vehicle speed value, the intelligent driving mode and the rack speed value of the steering gear; step 9b, obtains the rack speed limit under the current calibration curve; step 9c, compares the current rack speed and the rack speed limit, if the current rack speed is less than the rack speed limit, no processing is performed; if the current rack speed is greater than the rack speed limit, the difference between the current rack speed and the safety rack speed is processed by PI loop to obtain the safety motor torque M2=Kp×(V1-V2)+Ki×∫(V1-V2) dt after the rack speed is limited, Kp is the torque proportional parameter, Ki is the torque integral parameter, V1 is the limited target rack speed, and V2 is the actual steering gear rack speed.

[0043] The safety limit of rack speed is related to intelligent driving functions, such as Figure 6 As shown in the calibration curve, the safety limit a allowed by the intelligent driving function based on the hands-free scenario is the lowest; for the intelligent driving function based on the driver-in-the-loop scenario, the driver's reaction time will be faster after failure, and the safety limit b allowed is slightly higher; due to the low vehicle speed, the safety limit d allowed by the automatic parking function is the highest.

[0044] For the steering avoidance assist function, the steering system needs to meet the functional safety requirements while cooperating with large dynamic lateral movements. The allowable safety limit c is slightly higher than b. EPS needs to meet the following three conditions: in human driving mode, the driver actively steers, the hand force gradient is greater than the calibration value m and the rack speed is greater than the calibration value z, and the host computer requests the emergency avoidance steering function. At this time, the safety limit of EPS is temporarily switched to c, and the allowed time is t.

[0045] Step 10, the motor torque of the basic steering module in the human driving mode and the intelligent driving function torque in the intelligent driving mode are switched through the gain regulator.

[0046] After the intelligent driving mode is activated, the intelligent driving torque increases with a gradient of 0.01Nm / ms to the total intelligent driving function torque, and the human driving torque decreases to 0 with a gradient of 0.02 Nm / ms; after the intelligent driving mode is exited, the human driving torque increases with a gradient of 0.01Nm / ms to the motor torque, and the intelligent driving torque decreases to 0 with a gradient of 0.02 Nm / ms.

[0047] After the intelligent driving mode is activated, when the torsion bar torque is greater than the maximum set value and the maintenance time exceeds the maximum set time value, it is judged that the driver is encountering an emergency scenario or has a strong intention to take over the steering wheel, and the intelligent driving mode is exited and the human driving mode is entered; when the steering wheel torque is less than or equal to the maximum calibration value, it is judged that the driver has no intention to take over, the intelligent driving mode is kept activated, and the human-machine co-driving mode is in progress.

[0048] After the intelligent driving mode is activated, if any of the system status, steering angle sensor status, and vehicle speed status of the electric power steering system controller is abnormal, the intelligent driving mode will be exited and the manual driving mode will be entered.

[0049] When the driving assistance function is in effect, the steering system satisfies human-machine co-driving, and the driver controls and drives the vehicle with a smooth and comfortable feel. When the driver takes his hands off the wheel, the driving assistance function continues to control the lateral movement of the vehicle; the function exits when the calibrated driver torque limit is exceeded.

[0050] The present invention meets the usage scenarios of assisted automatic parking, driver-in-the-loop, driver hands-off, and emergency avoidance; accepting the target rack position requested by the vehicle host computer, the electronic power steering system calculates the required motor torque through an internal controller to achieve lateral control response; the safety function of the maximum rack speed limit of the steering system can meet the functional safety goal of avoiding oversteering; when the driving assistance function is in effect, it can simultaneously meet the corner following, smooth switching, and comfortable hand-feel control in the human-machine co-driving scenario.

Claims

1. A method for controlling a steering system for multiple advanced driver assistance scenarios, characterized in that: The steps include: Step 1, the electric power steering system controller obtains the driving assistance function status, target wheel angle or target steering wheel angle, vehicle speed status, and vehicle speed signal of the vehicle controller in real time, and uses them as input to the steering control module; Step 2, the steering control module receives the system status, the angle sensor status, the current rack position, the rotor speed and the torsion bar torque signal of the electric power steering system controller in real time; Step 3, when the system state, the angle sensor state, and the vehicle speed state of the electric power steering system controller are all normal, and the vehicle speed is less than the maximum calibration value, and the torsion bar torque is less than the maximum calibration value, the module system state machine is in a waiting state. After the vehicle controller sends a function enable signal, the controller enters the intelligent driving mode and continues to perform steps 4 and 10. When any of the system state, the angle sensor state, and the vehicle speed state of the electric power steering system controller is abnormal, or the vehicle speed is greater than the maximum calibration value, or the torsion bar torque is greater than the maximum calibration value, the module system state machine is in an abnormal state and maintains the human driving mode; Step 4, the electric power steering system converts the target wheel angle or target steering wheel angle requested by the host computer into the target rack position: if the host computer requests the target wheel angle A1, the target rack position L1 = iw×A1×ic / 360; if the host computer requests the target steering wheel angle A2, the target rack position L1 = A2×ic / 360, iw is the ratio of the steering wheel angle to the steering wheel deflection angle on the same side of the steering wheel, and ic is the line angle transmission ratio of the steering system; Step 5, calculate the rack position difference = target rack position - current rack position of the steering gear; Step 6, according to different vehicle speeds and rack position differences, a two-dimensional table lookup is performed to obtain the target hand torque; Step 7, calculate the target total hand torque = target hand torque + active inertia module output hand torque + intermediate sense module output hand torque; Step 8, calculating the motor torque of the hand force controller according to the target total hand torque and the torsion bar torque; Step 9: Superimpose the motor torque of the hand force controller and the torque of the rack speed limit module to obtain the total intelligent driving function torque; Step 10, the motor torque of the basic steering module in the human driving mode and the intelligent driving function torque in the intelligent driving mode are switched through the gain regulator.

2. A method for controlling a steering system for multiple advanced driver assistance scenarios according to claim 1, characterized in that: The two-dimensional table lookup forms a calibrable curve through the rack position difference and the vehicle speed, and searches for the target hand torque from the curve.

3. The method for controlling a steering system for multiple advanced driver assistance scenarios according to claim 1, characterized in that: After the intelligent driving mode is activated, when the torsion bar torque is greater than the maximum set value for a period of time that exceeds the maximum set time value, it is judged that the driver has encountered an emergency scenario or has a strong intention to take over the steering wheel, and the intelligent driving mode is exited and the human driving mode is entered; When the steering wheel torque is less than or equal to the maximum calibration value, it is judged that the driver has no intention to take over, and the intelligent driving mode remains activated, in human-machine co-driving mode.

4. The method for controlling a steering system for multiple advanced driver assistance scenarios according to claim 1, characterized in that: After the intelligent driving mode is activated, if any of the system status, steering angle sensor status, and vehicle speed status of the electric power steering system controller is abnormal, the intelligent driving mode will be exited and the manual driving mode will be entered.

5. The method for controlling a steering system for multiple advanced driver assistance scenarios according to claim 1, characterized in that: The motor torque M1 of the hand force controller is calculated as follows: Kp×(T1-T2)+Ki×∫(T1-T2)dt+Kd×{(T1-T2)- (T1'-T2')}, where Kp is the torque proportional parameter, Ki is the torque integral parameter, T1 is the target total hand torque, T2 is the actual torsion bar torque, T1' is the target total hand torque of the previous cycle, and T2' is the actual torsion bar torque of the previous cycle.

6. The method for controlling a steering system for multiple advanced driver assistance scenarios according to claim 1, characterized in that: The step 9 comprises the following steps: step 9a, the controller obtains the vehicle speed value, the intelligent driving mode and the rack speed value of the steering gear; step 9b, obtains the rack speed limit under the current calibration curve; step 9c, compares the current rack speed with the rack speed limit, and if the current rack speed is less than the rack speed limit, no processing is performed; If the current rack speed is greater than the rack speed limit, the difference between the current rack speed and the safety rack speed is processed by the PI loop to obtain the safety motor torque M2=Kp×(V1-V2)+Ki×∫(V1-V2) dt after the rack speed is limited, where Kp is the torque proportional parameter, Ki is the torque integral parameter, V1 is the limited target rack speed, and V2 is the actual steering gear rack speed.

7. The method for controlling a steering system for multiple advanced driver assistance scenarios according to claim 1, characterized in that: In the step 10, after the intelligent driving mode is activated, the intelligent driving torque increases with a gradient of 0.01 Nm / ms to the total intelligent driving function torque, and the human driving torque decreases with a gradient of 0.02 Nm / ms to 0; after the intelligent driving mode is exited, the human driving torque increases with a gradient of 0.01 Nm / ms to the motor torque, and the intelligent driving torque decreases with a gradient of 0.02 Nm / ms to 0.

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