Method for steering system control for multiple advanced driver assistance scenarios

Abstract

This invention relates to the field of automotive steering control technology, specifically a method for controlling a steering system in various advanced driver assistance scenarios. Compared with existing technologies, this invention meets the usage scenarios of assisted automatic parking, driver-in-the-loop, driver-hands-free, and emergency avoidance; it receives the target rack position requested by the vehicle's host computer, and the electronic power steering system calculates the required motor torque through its internal controller to achieve lateral control response; the safety function of limiting the maximum rack speed of the steering system can meet the functional safety target of preventing oversteering from being violated; when the driver assistance function is in operation, it can simultaneously meet the requirements of angle following, smooth switching, and comfortable hand feel control in human-machine co-driving scenarios.

Description

Technical Field

[0001] This invention relates to the field of automotive steering control technology, specifically a method for steering system control in various advanced driver assistance scenarios. Background Technology

[0002] In recent years, China's advanced driver assistance systems (ADAS) have developed rapidly. However, due to the expensive vehicle architecture and the lack of formally promulgated laws and regulations, the implementation of SAE L3 / L4 autonomous driving functions has been delayed. Currently, SAE L2 functions have become the mainstream in the market.

[0003] Common automatic parking, lane keeping assist, and city / highway cruise control functions, along with electronic power steering, all require instructions from the host computer to execute motor torque responses and control the vehicle's lateral movement. More and more vehicles are equipped with driver monitoring systems to ensure the driver remains focused on the vehicle, allowing them to take their hands off the wheel. With the increasing demand for human-machine co-driving, drivers need good tactile feedback to control the vehicle's steering when driver assistance functions are in operation. Steering avoidance assist, as part of active vehicle safety, requires the steering system to meet functional safety requirements while accommodating large dynamic lateral movements.

[0004] CN114348112A discloses a vehicle steering control method suitable for semi-autonomous driving scenarios, which uses a dual PID algorithm. The difference between the target rack position and the ESP rack position is calculated using an outer loop PID algorithm, and the difference between the current rack speed and the EPS rack speed is calculated using an inner loop PID algorithm 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 large angles or rapid interventions, to determine whether the driver has intervened in the steering wheel.

[0006] The adaptive control method for 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 human-machine co-driving state, and coordinates the calculation of the output of basic assist torque and angle closed-loop control torque as the total motor torque.

[0007] In summary, existing patents on angle closed-loop control and human-machine co-driving either rely on the torque output of existing EPS basic functions superimposed with the torque of dual PID angle control algorithms, or when the steering rack is moving, functions related to steering angle or angular velocity, such as active return-to-center function, stability function, and inertia compensation function, will output torque, causing the EPS angle following performance to be negatively affected by the basic functions; or they do not consider the smoothness of the hand feel when the driver intervenes, or the superimposed algorithm makes it difficult to tune the smoothness of the driver intervention.

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

[0009] The purpose of this invention is to overcome the shortcomings of the prior art and provide a steering system control method for various advanced driver assistance scenarios. It 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 scenarios. The rack position-hand torque control algorithm can simultaneously meet the requirements of corner following, smooth switching and comfortable hand feel control in human-machine co-driving scenarios.

[0010] To achieve the above objectives, this invention provides a steering system control method for various advanced driver assistance scenarios, comprising the following steps: Step 1, the 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 the vehicle controller in real time, and uses these as inputs to the 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 target... When the set value or torsion bar torque is less than the maximum calibrated 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 steps 4 and 10. When any of the system state, steering angle sensor state, or vehicle speed state of the electric power steering system controller is abnormal, or the vehicle speed is greater than the maximum calibrated value, or the torsion bar torque is greater than the maximum calibrated value, the module system state machine is in an abnormal state and maintains the human driving mode. In 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 = If the host computer requests the target steering wheel angle A2, the target rack position L1 = A2 × ic / 360, where iw is the ratio of the steering wheel angle to the steering wheel deflection angle on the same side, 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: Based on different vehicle speeds and rack position differences, perform a two-dimensional lookup table to obtain the target hand torque; Step 7: Calculate the target total hand torque = target hand torque + hand torque output by the active inertia module + hand torque output by the intermediate sensing module; Step 8: Calculate the motor torque of the hand torque controller based on the target total hand torque and the torsion bar torque; Step 9: Superimpose the motor torque of the hand torque controller and the torque of the rack speed limit module to obtain the total intelligent driving function torque; Step 10: Switch between the motor torque of the basic steering module in human driving mode and the intelligent driving function torque in intelligent driving mode through a gain regulator.

[0011] The two-dimensional lookup table is formed by the rack position difference and vehicle speed to create a calibrable curve, and the target hand torque is found from the curve.

[0012] After the intelligent driving mode is activated, if the torsion bar torque is greater than the maximum set value for a longer period of time than the maximum set value, it is determined that the driver has encountered a sudden 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; if the steering wheel torque is less than or equal to the maximum calibrated value, it is determined that the driver has no intention to take over, the intelligent driving mode is kept active, and the human-machine co-driving mode is entered.

[0013] Once the intelligent driving mode is activated, if any of the following conditions are abnormal: the system status of the electric power steering system controller, the steering angle sensor status, or the vehicle speed status, the intelligent driving mode will be exited and the human driving mode will be entered.

[0014] The motor torque 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.

[0015] Step 9 includes the following steps: Step 9a, the controller acquires the vehicle speed value, the intelligent driving mode, and the rack speed value of the steering gear; Step 9b, acquires the rack speed limit under the current calibration curve; Step 9c, compares the current rack speed with 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 safe rack speed is processed by a PI loop to obtain the safe motor torque after rack speed limitation M2=Kp×(V1-V2)+Ki×∫(V1-V2) dt, where Kp is the torque proportional parameter, Ki is the torque integral parameter, V1 is the target rack speed to be limited, and V2 is the actual steering gear rack speed.

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

[0017] Compared with existing technologies, this invention meets the usage scenarios of assisted automatic parking, driver-in-the-loop, driver-hands-free, and emergency avoidance; it accepts the target rack position requested by the vehicle's host computer, and the electronic power steering system calculates the required motor torque through the internal controller to achieve lateral control response; the safety function of limiting the maximum rack speed of the steering system can meet the functional safety target of avoiding oversteering being violated; when the driving assistance function is in effect, it can simultaneously meet the requirements of corner following, smooth switching, and comfortable hand feel control in human-machine co-driving scenarios. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the interaction between the EPS and the host computer in an advanced driver assistance scenario.

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

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

[0021] Figure 4 This is the logic diagram for calculating the nominal hand force of active inertia in this invention.

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

[0023] Figure 6 Calibration curves for the rack speed safety limits allowed by different intelligent driving functions of the present invention. Detailed Implementation

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

[0025] See Figure 1 In advanced driver assistance scenarios, the host computer monitors the environment using radar / cameras, plans the vehicle path, and calculates the target wheel angle. The EPS first converts the wheel angle into the target rack position, calculates the torque in intelligent driving mode using the rack position-hand torque algorithm, and outputs it to the motor via FOC. The EPS moves the rack, and the vehicle moves laterally to achieve the target trajectory.

[0026] This invention is a method for controlling a steering system in various advanced driver assistance scenarios, comprising the following steps:

[0027] Step 1: The 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 from the vehicle controller in real time, and uses them as input to the steering control module.

[0028] Step 2: The steering control module receives real-time system status, angle sensor status, current rack position, rotor speed, and torsion bar torque signals from the electric power steering system controller.

[0029] Step 3: When the system status of the electric power steering system controller, the steering angle sensor status, and the vehicle speed status 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 steps 4 and 10. When any of the system status of the electric power steering system controller, the steering angle sensor status, or the vehicle speed status 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.

[0030] 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.

[0031] 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 linear angle transmission ratio of the steering system. ic is a mechanical parameter, and the unit is mm / rev.

[0032] Step 5, calculate the rack position difference = target rack position - current steering gear rack position.

[0033] See Figure 2 In a scenario where the driver takes their hands off the wheel, 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.

[0034] When the driver intervenes in driving the vehicle, the angle difference increases as the driver intervenes in steering. The target hand torque also increases linearly by looking up the table. Through the hand force PID control loop, the actual hand force is close to the torsion bar torque. The actual hand force approaches the target hand force, creating the effect that the driver's hand torque changes with the angle difference.

[0035] Step 6: Based on different vehicle speeds and rack position differences, perform a two-dimensional lookup table to obtain the target hand torque.

[0036] Two-dimensional lookup tables use rack position differences and vehicle speed to form a calibrable curve, and then find the target hand torque from this curve, such as... Figure 2 The curve is shown.

[0037] Step 7: Calculate the total target hand torque = target hand torque + hand torque output by the active inertia module + hand torque output by the intermediate sensing module.

[0038] The center-sensing module is designed to simulate steering force in the center zone at different vehicle speeds. See [link / reference]. Figure 3 The nominal torque is obtained by multiplying the torque that varies with the steering angle and the factor that varies with the vehicle speed. The steering angle ranges from 0 to 6°. The larger the steering angle, the greater the torque value; the higher the vehicle speed, the greater the torque factor.

[0039] The active inertia module is used to change the inertia of the steering system. See [link / reference]. Figure 4 The nominal hand force of inertia is obtained by multiplying the rotor inertia, the inertia torque that varies with the torsion bar torque, and the torque factor that varies with vehicle speed. The greater the hand force, the smaller the torque value; the higher the vehicle speed, the greater the torque factor.

[0040] Step 8: Calculate the motor torque of the hand force controller based on the target total hand torque and the torsion bar torque. The motor torque 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.

[0041] Step 9: Add 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.

[0042] This module is designed for safety reasons. The rack speed limit should be different in different intelligent driving modes.

[0043] See Figure 5 Step 9 includes the following steps: Step 9a, the controller acquires the vehicle speed value, the intelligent driving mode, and the rack speed value of the steering gear; Step 9b, acquires the rack speed limit under the current calibration curve; Step 9c, compares the current rack speed with 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 safe rack speed is processed by a PI loop to obtain the safe motor torque after rack speed limitation M2=Kp×(V1-V2)+Ki×∫(V1-V2) dt, where Kp is the torque proportional parameter, Ki is the torque integral parameter, V1 is the target rack speed to be limited, and V2 is the actual steering gear rack speed.

[0044] The safety limits for rack and pinion speeds are related to intelligent driving functions, such as... Figure 6 As shown in the calibration curves, the safety limit 'a' for intelligent driving functions based on hands-free scenarios is the lowest; for intelligent driving functions based on driver-in-the-loop scenarios, the driver's reaction time is faster after a failure, and the safety limit 'b' is slightly higher; due to the low vehicle speed, the safety limit 'd' for automatic parking functions is the highest.

[0045] For steering avoidance assist functions, the steering system must meet functional safety requirements while cooperating with large dynamic lateral movements. The permissible safety limit c is slightly higher than b. EPS must meet the following three conditions: In human-driven mode, the driver actively steers, the hand force gradient is greater than the calibrated value m, and the rack speed is greater than the calibrated value z, at which point the host computer requests the emergency avoidance steering function. At this time, the EPS safety limit temporarily switches to c, and the allowed time is t.

[0046] Step 10: The motor torque of the basic steering module in human driving mode and the torque of the intelligent driving function in intelligent driving mode are switched through the gain regulator.

[0047] After the intelligent driving mode is activated, the intelligent driving torque increases in a gradient of 0.01 Nm / ms to become the total intelligent driving function torque, while the human driving torque decreases in a gradient of 0.02 Nm / ms to become 0. After the intelligent driving mode is deactivated, the human driving torque increases in a gradient of 0.01 Nm / ms to become the motor torque, while the intelligent driving torque decreases in a gradient of 0.02 Nm / ms to become 0.

[0048] After the intelligent driving mode is activated, if the torsion bar torque is greater than the maximum set value for a longer period of time than the maximum set value, it is determined that the driver has encountered a sudden 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; if the steering wheel torque is less than or equal to the maximum calibrated value, it is determined that the driver has no intention to take over, the intelligent driving mode is kept active, and the human-machine co-driving mode is entered.

[0049] Once the intelligent driving mode is activated, if any of the following conditions are abnormal: the system status of the electric power steering system controller, the steering angle sensor status, or the vehicle speed status, the intelligent driving mode will be exited and the human driving mode will be entered.

[0050] When the driver assistance function is in operation, the steering system enables human-machine co-driving, allowing the driver to control and drive the vehicle with a smooth and comfortable feel. When the driver takes their hands off the wheel, the driver assistance function continues to control the lateral movement of the vehicle until the calibrated driver torque limit is exceeded, at which point the function disengages.

[0051] This invention meets the usage scenarios of assisted automatic parking, driver-in-the-loop, driver-hands-free, and emergency avoidance; it accepts the target rack position requested by the vehicle's host computer, and the electronic power steering system calculates the required motor torque through the internal controller to achieve lateral control response; the safety function of limiting the maximum rack speed of the steering system can meet the functional safety target of avoiding oversteering being violated; when the driving assistance function is in operation, it can simultaneously meet the requirements of corner following, smooth switching, and comfortable hand feel control in human-machine co-driving scenarios.

Claims

1. A method for controlling a steering system in various advanced driver assistance scenarios, characterized in that: Includes the following steps: Step 1: The 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 from the vehicle controller in real time, and uses them as input to the steering control module. Step 2: The steering control module receives real-time system status, angle sensor status, current rack position, rotor speed, and torsion bar torque signals from the electric power steering system controller. Step 3: When the system status of the electric power steering system controller, the steering angle sensor status, and the vehicle speed status 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 steps 4 and 10. When any of the system status of the electric power steering system controller, the steering angle sensor status, or the vehicle speed status 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 linear angle transmission ratio of the steering system. Step 5, calculate the rack position difference = target rack position - current steering gear rack position; Step 6: Based on different vehicle speeds and rack position differences, perform a two-dimensional lookup table to obtain the target hand torque; Step 7, calculate the total target hand torque = target hand torque + hand torque output by the active inertia module + hand torque output by the intermediate sensing module; Step 8: Calculate the motor torque of the hand force controller based on the target total hand torque and torsion bar torque; Step 9: Add 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 torque of the intelligent driving function in intelligent driving mode are switched through the gain regulator.

2. The method for steering system control in various advanced driver assistance scenarios according to claim 1, characterized in that: The two-dimensional lookup table is formed by the rack position difference and vehicle speed to create a calibrable curve, and the target hand torque is found from the curve.

3. The method for steering system control in various advanced driver assistance scenarios according to claim 1, characterized in that: After the intelligent driving mode is activated, if the torsion bar torque is greater than the maximum set value for a longer period of time than the maximum set value, it is determined that the driver has encountered a sudden 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 calibrated value, it is determined that the driver has no intention to take over, so the intelligent driving mode is kept active and the system is in human-machine co-driving mode.

4. The method for steering system control in various advanced driver assistance scenarios according to claim 1, characterized in that: Once the intelligent driving mode is activated, if any of the following conditions are abnormal: the system status of the electric power steering system controller, the steering angle sensor status, or the vehicle speed status, the intelligent driving mode will be exited and the human driving mode will be entered.

5. The method for steering system control in various advanced driver assistance scenarios according to claim 1, characterized in that: The motor torque 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.

6. The method for steering system control in various advanced driver assistance scenarios according to claim 1, characterized in that: 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, the controller obtains the rack speed limit under the current calibration curve; Step 9c, the controller 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 safe rack speed is processed by a PI loop to obtain the safe motor torque after the rack speed is limited: M2 = Kp × (V1 - V2) + Ki × ∫ (V1 - V2) dt, where Kp is the torque proportional parameter, Ki is the torque integral parameter, V1 is the target rack speed to be limited, and V2 is the actual steering rack speed.

7. A method for steering system control in various advanced driver assistance scenarios according to claim 1, characterized in that: In step 10, after the intelligent driving mode is activated, the intelligent driving torque increases at a gradient of 0.01 Nm / ms to become the total intelligent driving function torque, while the human driving torque decreases at a gradient of 0.02 Nm / ms to become 0; after the intelligent driving mode is deactivated, the human driving torque increases at a gradient of 0.01 Nm / ms to become the motor torque, while the intelligent driving torque decreases at a gradient of 0.02 Nm / ms to become 0.

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