Steer-by-wire fault tolerance device and method based on pavement perception

Abstract

The invention discloses a steer-by-wire fault-tolerant device and method based on road surface sensing, and the method comprises the steps: obtaining road surface information and vehicle information in real time through arranging a road surface sensing module, a vehicle state monitoring module, a fault-tolerant execution module and an active unit on an electric golf cart; the road surface friction coefficient between the current road surface and the vehicle is calculated in real time by combining the road surface information and the vehicle information, and whether the current vehicle is at the sideslip critical point caused by oversteering or not is judged by further calculating related parameters such as the road surface friction coefficient and the yaw velocity. And the fault-tolerant execution module is controlled in real time by calculating parameters to actively intervene the actual steering angle of the vehicle, and meanwhile, a driver is reminded in a steering wheel vibration mode, so that the risk of sideslip caused by excessive steering on a wet and slippery road surface can be effectively prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of safety control of electric golf carts, and in particular to a road surface perception-based steer-by-wire fault-tolerant device and method. Background Art

[0002] Electric golf carts often travel on slippery grass and gravel roads. When the driver drives an electric golf cart on a road with a low friction coefficient, the driver may oversteer due to insufficient estimation of road friction, causing the vehicle to skid.

[0003] Currently, the vast majority of electric golf carts use traditional steering systems, which control the vehicle's steering through a steering wheel, steering column, and steering rod. This makes it difficult to proactively intervene when an electric golf cart oversteers on slippery roads. Steer-by-wire systems are an emerging electronic steering system currently under development for civilian vehicles. These systems use electronic signals between the steering wheel and wheels, replacing the traditional mechanical connection. This allows for safe proactive intervention through the linkage of detection sensors.

[0004] The steer-by-wire systems currently under development on the market mainly include a steering wheel module (including a steering wheel, a steering wheel angle sensor, a torque sensor, and a return torque motor), a front-wheel steering module (including a steering actuator motor, a reduction mechanism, a front-wheel angle sensor, and a motor controller), and a main controller (ECU).

[0005] In light of this, the inventors, building on the technology currently under development for steer-by-wire systems, have developed a "Road Surface Sensing-Based Fault-Tolerant Steer-by-Wire Device and Method," which significantly improves vehicle safety on slippery roads. By utilizing this technology to perceive road conditions in real time, the system proactively alerts and intervenes to correct any driver oversteering. Summary of the Invention

[0006] The purpose of the present invention is to provide a steer-by-wire fault-tolerant device and method based on road surface perception. By arranging components for road surface perception and setting a fault-tolerant device in an electric golf cart, the risk of oversteering and resulting in sideslip on slippery roads can be effectively prevented. At the same time, it can also serve as an important technical reserve, providing strong support for the iterative upgrade of the steering system of electric golf carts.

[0007] The technical solution of the present invention is achieved as follows:

[0008] A steer-by-wire fault-tolerant device includes a road surface sensing module, a vehicle status monitoring module, a main control unit, and a fault-tolerant execution module. The road surface sensing module includes a six-axis IMU sensor and an infrared road surface sensor. The six-axis IMU sensor is installed at the geometric center of the chassis to collect the longitudinal acceleration of the vehicle body. , lateral acceleration of the vehicle body , actual yaw rate The infrared road surface sensor is installed at the front bumper and tilted downward 13~16° to collect the road surface reflectivity R. 、 and R are used to calculate the road friction coefficient The vehicle status monitoring module includes a wheel speed sensor and a steering angle sensor; the wheel speed sensors are respectively arranged on the inner side of the wheel hubs of the left and right front wheels of the vehicle, and are used to collect the angular velocity of the left front wheel. and the angular velocity of the right front wheel The steering angle sensor is located on the steering column coupling and is used to collect the steering wheel angle. The fault-tolerant execution module includes a steering wheel vibration motor and an electronic steering actuator. The steering wheel vibration motor is located in the steering wheel. The main control unit is electrically connected to the road perception module, the vehicle status monitoring module and the fault-tolerant execution module to calculate the rollover risk index. and sideslip risk value .

[0009] A steer-by-wire fault-tolerant method using the steer-by-wire fault-tolerant device according to claim 1, comprising the following steps:

[0010] S1. Obtain the longitudinal acceleration of the vehicle body through the six-axis IMU sensor , lateral acceleration of the vehicle body and the actual yaw rate ;

[0011] S2, obtaining the road surface reflectivity R through an infrared road surface sensor;

[0012] S3. Obtain the angular velocity of the left front wheel through the wheel speed sensor and the angular velocity of the right front wheel , and calculate the vehicle longitudinal velocity ;

[0013] S4. Obtain the steering wheel angle through the steering angle sensor ;

[0014] S5. Fusion calculation of road friction coefficient , ,in, is the reflectivity-friction coefficient mapping function, 、 is the weight coefficient, is the acceleration due to gravity;

[0015] S6. Calculate the sideslip risk value , ,in is the desired yaw rate, which is calculated by the two-degree-of-freedom model. The calculation formula is: , is the steering wheel angle, is the wheelbase, For insufficient steering gradient;

[0016] S7, when When the set threshold is exceeded, the following actions are performed:

[0017] S71, control the steering wheel vibration motor to work at a duty cycle of 70%~80%,

[0018] S72, calculate the safe steering angle , ,

[0019] S73, limit the actual steering angle , ,in, Current steering wheel angle The sign (positive or negative), To take the smaller of the two values, the absolute value of the current steering angle and 80% of the absolute value of the safe steering angle.

[0020] A further technical solution is that the vehicle longitudinal speed The calculation formula is ,in is the rolling radius of the left front wheel tire, is the rolling radius of the right front wheel tire.

[0021] A further technical solution is that 、 , The results are obtained by calibration on different wet and slippery roads. When R>0.7, =0.85, when 0.4≤R≤0.7, =0.45, when R<0.4, =0.25, where is the road friction coefficient under different R values The value of R ranges from 0 to 1.0. is the acceleration due to gravity, and the above conditions are substituted into the road friction coefficient The calculation formula can be obtained as follows: .

[0022] A further technical solution is that the understeering gradient K is calibrated by the following formula: ,in: To calibrate the test speed, To measure the actual yaw rate during calibration, maintain a speed of 19.8-20.2 km / h on a dry road, input a 30° steering wheel angle, and record the steady-state yaw rate. , the K value that meets the test vehicle is calibrated through the above measured data.

[0023] A further technical solution is that The threshold value is ,when When , it is determined that there is a risk of skidding.

[0024] The beneficial effects of the present invention are:

[0025] 1. Multi-source fusion road perception: Combines IMU dynamic data and infrared optical detection to calculate the current road friction coefficient in real time , so that the current road friction coefficient The value is more accurate, and the sideslip risk value, sideslip risk value threshold and actual steering angle are calculated more accurately, providing precise and safe active steering control.

[0026] 2. Two-Way Fault Tolerance: Steering wheel vibration alerts the driver, informing them that the vehicle has reached the critical point of skidding. This allows the driver to proactively reduce speed or steering angle to prevent a skid. Dynamic steering angle limiting also allows the driver to take over steering, reducing the likelihood of a skid. The steering wheel warning also lets the driver know that understeering is not due to a malfunction, preventing panic. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a front wheel steering module in the prior art;

[0028] Figure 2 Schematic diagram of the coordinated execution of the fault-tolerant device and the fault-tolerant method in the present invention.

[0029] In the figure, 1. Electronic steering actuator. DETAILED DESCRIPTION

[0030] In order to better understand the technical content of the present invention, specific embodiments are provided below, and the present invention is further described in conjunction with the accompanying drawings.

[0031] A steer-by-wire fault-tolerant device for an electric golf cart comprises a road surface sensing module, a vehicle state monitoring module, a main control unit and a fault-tolerant execution module.

[0032] The road surface perception module includes a six-axis IMU sensor and an infrared road surface sensor to obtain the road friction coefficient in real time. The six-axis IMU sensor can use the BMI088 sensor, which is installed at the geometric center of the chassis with a sampling rate of 100Hz. The infrared sensor is installed on the front bumper at a 15° forward tilt, 200~300mm from the ground.

[0033] The vehicle status monitoring module includes a wheel speed sensor and a steering angle sensor. The wheel speed sensors are respectively arranged on the inner side of the wheel hubs of the two front wheels, and the steering angle sensor is arranged on the steering column coupling.

[0034] It should be noted that in the steer-by-wire systems currently available on the market, the steering angle sensor is arranged on the steering wheel module, which is an existing structural design. The existing structural design can be directly used to implement the solution in this disclosure.

[0035] The fault-tolerant execution module includes a steering wheel vibration motor and an electronic steering actuator 1. The steering wheel vibration motor is arranged in the steering wheel. Specifically, a corresponding placement slot can be opened at the steering wheel handle for placing the steering wheel vibration motor.

[0036] See also Figure 1 It should be noted that the electronic steering actuator 1 includes a steering actuator motor, a reduction mechanism, a front wheel angle sensor and a motor controller. The steering actuator motor is used to receive controller instructions and drive the steering mechanism to rotate the wheels. The reduction mechanism is used to amplify the motor torque. The front wheel angle sensor is used to monitor and measure the steering angle in real time and feed it back to the controller for closed-loop control. The motor controller is used to adjust the speed and torque of the steering actuator motor. In the wire-controlled steering systems currently available on the market, the electronic steering actuator 1 is arranged on the front wheel steering module, which is an existing structural design. The existing structural design can be directly used to implement the solution disclosed in this disclosure.

[0037] Six-axis IMU sensor is used to collect the longitudinal acceleration of the vehicle body , lateral acceleration of the vehicle body , yaw angular velocity .

[0038] The infrared road surface sensor is used to collect the road surface reflectivity R.

[0039] By measuring the above parameters, the road friction coefficient can be calculated , road friction coefficient The calculation formula is as follows:

[0040]

[0041] in, is the reflectivity-friction coefficient mapping function, 、 is the weight coefficient.

[0042] Specifically, The value is 0.7, The value is 0.3. The reflectivity-friction coefficient mapping function is obtained by calibration on different wet and slippery road surfaces. The reflectivity-friction coefficient mapping table in this disclosure is:

[0043] When R>0.7, =0.85

[0044] When 0.4≤R≤0.7, =0.45

[0045] When R<0.4, =0.25

[0046] in, is the road friction coefficient under different R values The value of R ranges from 0 to 1.0. Substituting the above conditions into the road friction coefficient The calculation formula can be obtained as follows:

[0047]

[0048] The wheel speed sensor is used to collect the angular velocity of the two front wheels. The angular velocity of the left front wheel (rad / s) and the angular velocity of the right front wheel (rad / s), combined with the rolling radius of the left front wheel tire (m) and the tire rolling radius of the right front wheel (m), the vehicle longitudinal speed can be calculated:

[0049]

[0050] Steering angle sensor is used to collect steering wheel angle .

[0051] The main control unit is electrically connected to the road perception module, the vehicle status monitoring module and the fault-tolerant execution module. Specifically, the main control unit can use the STM32H743VI controller. The main control unit is used to calculate the sideslip risk value. ,

[0052] The calculation formula of the sideslip risk value is:

[0053]

[0054] in: is the actual yaw rate (unit: rad / s), is the desired yaw rate (unit: rad / s), is the actual yaw rate and the desired yaw rate The deviation value of , the expected yaw rate is calculated by the two-degree-of-freedom model:

[0055]

[0056] in: : steering wheel angle (unit: rad / s), : Wheelbase (unit: m), : Understeering gradient (unit: s 2 / rad), which is the inherent characteristic of the vehicle. The yaw rate gain curve is fitted through the ISO standard double lane change test.

[0057] The understeer gradient K is calibrated by the following formula:

[0058]

[0059] in: To calibrate the test speed, To measure the yaw rate, maintain a speed of 19.8-20.2 km / h on a dry road, input a 30° steering wheel angle, and record the steady-state yaw rate. , the K value that meets the test vehicle is calibrated through the above measured data.

[0060] when Exceeding the threshold When , it is considered that there is a risk of sideslip, Set to:

[0061]

[0062] Among them, the threshold is the critical value of yaw rate deviation (unit: rad / s), and its physical meaning is the numerator Denominator representing the tire lateral force safety margin boundary This value reflects the impact of vehicle speed on steering dynamics. The value of 0.1 is set to introduce a speed offset to resolve the zero-speed singularity problem. It overall reflects the rotation angular rate threshold when the vehicle is about to become unstable.

[0063] when When the driver's steering angle is too large, the current steering wheel angle| ∣> When the active unit controls the electronic steering actuator 1, the steering angle is limited to ,in is the safe steering angle threshold under the current road surface and vehicle speed, and its calculation formula is as follows:

[0064]

[0065] in For insufficient steering gradient.

[0066] The value formula is as follows:

[0067]

[0068] in, Current steering wheel angle The sign (positive or negative) of the output command steering angle cannot exceed 80% of the safe steering angle while maintaining the same direction as the original steering angle, and it cannot exceed the current steering angle. To take the smaller of the two values, the absolute value of the current steering angle and 80% of the absolute value of the safe steering angle.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A steer-by-wire fault-tolerant device, characterized in that: It includes a road perception module, a vehicle status monitoring module, a main control unit and a fault-tolerant execution module. The road perception module includes a six-axis IMU sensor and an infrared road sensor; the six-axis IMU sensor is installed at the geometric center of the chassis to collect the longitudinal acceleration of the vehicle body. , lateral acceleration of the vehicle body , actual yaw rate The infrared road surface sensor is installed at the front bumper and tilted downward 13~16° to collect the road surface reflectivity R. 、 and R are used to calculate the road friction coefficient The vehicle status monitoring module includes a wheel speed sensor and a steering angle sensor; the wheel speed sensors are respectively arranged on the inner side of the wheel hubs of the left and right front wheels of the vehicle, and are used to collect the angular velocity of the left front wheel. and the angular velocity of the right front wheel The steering angle sensor is located on the steering column coupling and is used to collect the steering wheel angle. The fault-tolerant execution module includes a steering wheel vibration motor and an electronic steering actuator. The steering wheel vibration motor is located in the steering wheel. The main control unit is electrically connected to the road perception module, the vehicle status monitoring module and the fault-tolerant execution module to calculate the rollover risk index. and sideslip risk value .

2. A steer-by-wire fault-tolerant method using the steer-by-wire fault-tolerant device according to claim 1, characterized in that The following steps are involved: S1. Obtain the longitudinal acceleration of the vehicle body through the six-axis IMU sensor , lateral acceleration of the vehicle body and the actual yaw rate ; S2, obtaining the road surface reflectivity R through an infrared road surface sensor; S3. Obtain the angular velocity of the left front wheel through the wheel speed sensor and the angular velocity of the right front wheel , and calculate the vehicle longitudinal velocity ; S4. Obtain the steering wheel angle through the steering angle sensor ; S5. Fusion calculation of road friction coefficient , ,in, is the reflectivity-friction coefficient mapping function, 、 is the weight coefficient, is the acceleration due to gravity; S6. Calculate the sideslip risk value , ,in is the desired yaw rate, which is calculated by the two-degree-of-freedom model. The calculation formula is: , is the steering wheel angle, is the wheelbase, For insufficient steering gradient; S7, when When the set threshold is exceeded, the following actions are performed: S71, control the steering wheel vibration motor to work at a duty cycle of 70%~80%, S72, calculate the safe steering angle , , S73, limit the actual steering angle , ,in, Current steering wheel angle The sign (positive or negative), To take the smaller of the two values, the absolute value of the current steering angle and 80% of the absolute value of the safe steering angle.

3. The steer-by-wire fault-tolerance method according to claim 2, characterized in that: The vehicle longitudinal speed The calculation formula is ,in is the rolling radius of the left front wheel tire, is the rolling radius of the right front wheel tire.

4. The steer-by-wire fault-tolerance method according to claim 3, characterized in that: described 、 , The results are obtained by calibration on different wet and slippery roads. When R>0.7, =0.85, when 0.4≤R≤0.7, =0.45, when R<0.4, =0.25, where is the road friction coefficient under different R values The value of R ranges from 0 to 1.

0. is the acceleration due to gravity, and the above conditions are substituted into the road friction coefficient The calculation formula can be obtained as follows: .

5. The steer-by-wire fault-tolerance method according to claim 4, characterized in that: The understeer gradient K is calibrated by the following formula: ,in: To calibrate the test speed, To measure the actual yaw rate during calibration, maintain a speed of 19.8-20.2 km / h on a dry road, input a 30° steering wheel angle, and record the steady-state yaw rate. , the K value that meets the test vehicle is calibrated through the above measured data.

6. The steer-by-wire fault-tolerance method according to claim 5, characterized in that: described The threshold value is ,when When , it is determined that there is a risk of skidding.

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