CN111422250B - Rear wheel steering control method, device and system and computer storage medium - Google Patents
Rear wheel steering control method, device and system and computer storage medium Download PDFInfo
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- CN111422250B CN111422250B CN202010299499.6A CN202010299499A CN111422250B CN 111422250 B CN111422250 B CN 111422250B CN 202010299499 A CN202010299499 A CN 202010299499A CN 111422250 B CN111422250 B CN 111422250B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D5/00—Power-assisted or power-driven steering
- B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
- B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
- B62D5/046—Controlling the motor
Abstract
The disclosure provides a rear wheel steering control method, device and system and a computer storage medium, and belongs to the field of automobile steering. The rear wheel steering control method includes: acquiring vehicle state information of a vehicle in response to a vehicle steering command; determining a motor rotation angle of a rear wheel steering motor according to the vehicle state information and the transmission ratio from the rear wheel steering motor to a rear wheel; and controlling the rear wheel steering motor to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor.
Description
Technical Field
The present disclosure relates to the field of vehicle steering, and in particular, to a method, an apparatus, a system, and a computer storage medium for controlling rear wheel steering.
Background
An EPS (Electric Power Steering) refers to a Power Steering system that relies on an Electric motor to provide an assist torque. Current vehicles are dominated by electric front wheel power steering (i.e., active front wheel steering). With the development of the automobile industry, people increasingly regard the driving experience as an important link for evaluating the performance of vehicles. Since active rear wheel steering is of great significance in improving vehicle handling stability, increasing steering flexibility, and the like, many automobile manufacturers begin to consider applying active rear wheel steering technology to vehicle development and mass production.
In the related art, an active rear wheel steering method includes: firstly, an ECU (Electronic Control Unit) determines an ideal steering wheel angle parameter according to a steering wheel angle signal; secondly, determining an ideal tire force signal according to the angle deviation value of the ideal steering wheel angle parameter and the actual steering wheel angle parameter, and converting the ideal tire force signal into an ideal steering motor torque signal; then, calculating a motor torque deviation value of the ideal steering motor torque signal and the actual steering motor output torque signal; and finally, obtaining a voltage input signal of the rear wheel steering motor according to the motor torque deviation value, and outputting the voltage input signal (a rear wheel steering command) of the rear wheel steering motor to the rear wheel steering motor so that the rear wheel steering motor drives the rear wheel to steer according to the rear wheel steering command.
The rear wheel steering method provided by the related technology has the advantages of more calculation steps, longer time consumption, slow response to the rear wheel steering requirement and reduced steering flexibility.
Disclosure of Invention
The embodiment of the disclosure provides a rear wheel steering control method, a rear wheel steering control device, a rear wheel steering control system and a computer storage medium, which can calculate and realize the control of the rear wheel steering relatively quickly and improve the flexibility of the steering. The technical scheme is as follows:
in a first aspect, a rear wheel steering control method is provided, which includes:
acquiring vehicle state information of a vehicle in response to a vehicle steering command;
determining a motor rotation angle of a rear wheel steering motor according to the vehicle state information and the transmission ratio from the rear wheel steering motor to a rear wheel;
and controlling the rear wheel steering motor to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor.
Optionally, the vehicle state information includes a steering wheel angle, a vehicle speed, a yaw rate, and a rear wheel angle,
determining a motor rotation angle of a rear wheel steering motor according to the vehicle state information and a transmission ratio from the rear wheel steering motor to a rear wheel includes:
determining an ideal yaw velocity according to the steering wheel angle and the vehicle speed;
determining an ideal rear wheel corner according to the deviation of the yaw rate and the ideal yaw rate and the transfer function from the rear wheel corner to the yaw rate;
and determining the motor rotation angle of the rear wheel steering motor according to the deviation of the rear wheel rotation angle and the ideal rear wheel rotation angle and the transmission ratio from the rear wheel steering motor to the rear wheel.
Optionally, said determining an ideal rear wheel angle from the deviation of the yaw-rate from the ideal yaw-rate and a transfer function of rear wheel angle to yaw-rate comprises:
the ideal rear wheel turning angle is calculated according to the following formula,
δ * ideal rear wheel angle, omega r Is the yaw-rate of the vehicle,
for an ideal yaw rate, G is the transfer function of the rear wheel steering angle to the yaw rate.
Optionally, the vehicle is provided with a front wheel steering function,
the rear wheel steering control method further includes:
when the rear wheel steering motor is out of order, controlling the rear wheel to keep the rear wheel steering angle at the current moment unchanged, or,
when the rear wheel steering motor fails and the failure is motor failure, the rear wheel is controlled to keep the rear wheel steering angle at the current moment unchanged, and when the rear wheel steering motor fails and the failure is motor overload, if the rear wheel steering angle at the current moment is not 0, the rear wheel steering motor is controlled to drive the rear wheel to steer and the rear wheel steering angle of the rear wheel after steering is 0, and the rear wheel steering angle is kept to be 0 unchanged.
In a second aspect, there is provided a rear wheel steering control device including:
the acquisition module is used for responding to a vehicle steering command and acquiring vehicle state information of a vehicle;
the determining module is used for determining the motor rotation angle of the rear wheel steering motor according to the vehicle state information and the transmission ratio from the rear wheel steering motor to the rear wheel;
and the control module is used for controlling the rear wheel steering motor to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor.
Optionally, the vehicle state information includes a steering wheel angle, a vehicle speed, a yaw rate, and a rear wheel angle,
the determining module is configured to determine whether the user is in a sleep mode,
determining an ideal yaw rate according to the steering wheel angle and the vehicle speed;
determining an ideal rear wheel corner according to the deviation of the yaw rate and the ideal yaw rate and the transfer function from the rear wheel corner to the yaw rate;
and determining the motor rotation angle of the rear wheel steering motor according to the deviation of the rear wheel rotation angle and the ideal rear wheel rotation angle and the transmission ratio from the rear wheel steering motor to the rear wheel.
Optionally, the determining module is configured to,
the ideal rear wheel turning angle is calculated according to the following formula,
δ * ideal rear wheel angle, omega r Is the yaw rate of the vehicle,
to reason forThe yaw rate G is a transfer function of the rear wheel rudder angle to the yaw rate.
In a third aspect, a rear wheel steering control device is provided, which includes a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor is configured to implement the aforementioned rear wheel steering control method when executing the computer program.
In a fourth aspect, a computer storage medium is provided, where at least one instruction is stored, and the instruction is loaded and executed by a processor to implement the aforementioned rear wheel steering control method.
In a fifth aspect, there is provided a rear wheel steering control system including:
a sensor group;
a rear wheel steering mechanism;
a rear wheel steering motor;
a rear wheel steering control device;
the sensor group is used for collecting vehicle state information of a vehicle;
the rear wheel steering control device is used for responding to a vehicle steering command and acquiring vehicle state information of the vehicle acquired by the sensor group; determining a motor rotation angle of a rear wheel steering motor according to the vehicle state information and the transmission ratio from the rear wheel steering motor to a rear wheel; and controlling the rear wheel steering motor to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor.
The technical scheme provided by the embodiment of the disclosure has the following beneficial effects:
by responding to a vehicle steering command and acquiring vehicle state information of a vehicle, for example, the vehicle state information can comprise steering wheel turning angles, the steering demand sent by a driver when the driver operates the steering wheel can be responded in real time; determining the motor rotation angle of a rear wheel steering motor according to the vehicle state information and the transmission ratio from the rear wheel steering motor to the rear wheel, and controlling the rear wheel steering motor to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor; the calculation process of the motor rotation angle is simple, the calculation can be performed quickly, the control of the rear wheel steering is realized, and the steering flexibility is improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a schematic diagram of a rear wheel steering control system provided by an embodiment of the present disclosure;
FIG. 2 is a flow chart of a rear wheel steering control method provided by an embodiment of the present disclosure;
FIG. 3 is a flow chart of a rear wheel steering control method provided by an embodiment of the present disclosure;
FIG. 4 is a schematic structural diagram of a rear wheel steering control device provided in an embodiment of the present disclosure;
fig. 5 is a block diagram of a rear wheel steering control device according to an embodiment of the present disclosure.
Detailed Description
To make the objects, technical solutions and advantages of the present disclosure more apparent, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.
The terms related to the present embodiment are explained as follows.
The automobile or vehicle includes a four-wheeled automobile. A four-wheeled vehicle includes two front wheels and two rear wheels.
The steering wheel turning angle refers to the angle of rotation of the automobile steering wheel from the first initial position around the steering shaft of the steering wheel. When the steering wheel is at the first initial position, the steering wheel angle is 0, and when the steering wheel angle is 0, the automobile does not turn.
And the yaw angle refers to the angle of rotation of the automobile from the second initial position around the Z axis vertical to the ground. The yaw angle of the vehicle is 0 at the second initial position, and the central axis of the vehicle can be parallel to the lane line.
The yaw rate refers to a rate of change of the yaw angle.
The centroid slip angle refers to an included angle between the longitudinal direction of an automobile body and the motion direction (namely the tangent line of an automobile rotation circle), and represents the posture of the automobile relative to the rotation circle in constant-speed circular motion.
The front wheel rotation angle refers to the angle of the front wheel on the automobile rotating around the Z axis vertical to the ground from the third initial position. And when the front wheel is at the third initial position, the rotation angle of the front wheel is 0, and the plane of the front wheel is parallel to the height direction of the vehicle.
And the rear wheel steering angle refers to the angle of rotation of the rear wheel on the automobile from the fourth initial position around the Z axis vertical to the ground. And the rear wheel steering angle is 0 when the rear wheel is at the fourth initial position, and the plane of the rear wheel is parallel to the height direction of the vehicle.
And rotating the angle of the motor, namely the angle of the motor output shaft rotating around the axial direction from the fifth initial position. The motor rotation angle of the motor output shaft at the fifth initial position is 0, and the fifth initial position can be set according to the motor industry specification.
The applicable scenarios of the rear-wheel steering control method provided by the embodiment include a vehicle having a rear-wheel steering function and no front-wheel steering function, and a vehicle having a four-wheel steering function (front-wheel steering and rear-wheel steering). Alternatively, the rear wheel steering control method provided by the present embodiment is applicable to a vehicle having a four-wheel steering function. The front wheel Steering function may be an Electric Power Steering function, and as for an EPS (Electric Power Steering) used for the front wheel Electric Power Steering function, the present embodiment is not limited, and any EPS in the related art may be used for the front wheel Electric Power Steering function. For example, the operation principle of the EPS may include: when the driver operates the steering wheel to rotate, a torque sensor attached to a steering shaft of the steering wheel continuously detects a torque signal on the steering shaft (or a steering angle sensor attached to a steering shaft of the steering wheel continuously detects a steering wheel angle signal on the steering shaft), and the torque signal (or the steering wheel angle signal) is input to an ECU (Electronic Control Unit) together with a vehicle speed signal. The ECU determines the magnitude and direction of the power-assisted torque, namely the current of the selected power-assisted motor and the steering according to the input signals, and adjusts the magnitude of the steering auxiliary power. The torque of the power-assisted motor is added to a steering mechanism of the automobile after being reduced and increased in torque through the electromagnetic clutch through the speed reducing mechanism, so that a steering acting force which is adaptive to the working condition of the automobile is obtained and applied to the front wheel.
Fig. 1 is a schematic diagram of a rear wheel steering control system provided in an embodiment of the present disclosure, and referring to fig. 1, the rear wheel steering control system includes: the vehicle rear wheel steering system comprises a sensor group 1, a rear wheel steering mechanism 2, a rear wheel steering motor 3 and a rear wheel steering control device 4.
The rear wheel steering motor 3 is connected with the rear wheel through the rear wheel steering mechanism 2, and the sensor group 1 and the rear wheel steering motor 3 are respectively and electrically connected with the rear wheel steering control device 4.
The sensor group 1 is used to collect vehicle state information of the vehicle, which may include a steering wheel angle, a vehicle speed, a yaw rate, and a rear wheel angle.
The rear wheel steering control device 4 is used for responding to a vehicle steering command and acquiring vehicle state information of the vehicle acquired by the sensor group 1; determining a motor rotation angle of the rear wheel steering motor 3 according to the vehicle state information and the transmission ratio from the rear wheel steering motor 3 to the rear wheels; and controlling the rear wheel steering motor 3 to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor 3.
The vehicle steering command is triggered when the whole automobile steers, and can be triggered when a driver operates a steering wheel or triggered when an auxiliary driving system needs to steer.
Illustratively, the sensor group 1 includes a steering wheel angle sensor, a vehicle speed sensor, a yaw rate sensor, and a rear wheel angle sensor. The steering wheel angle sensor can be installed on a steering shaft of a steering wheel and used for collecting steering wheel angles, the vehicle speed sensor can be installed in a drive axle housing or a transmission housing and used for collecting vehicle speeds (particularly longitudinal speeds of automobiles), the yaw rate sensor can be installed in the position of the mass center of a vehicle body and used for collecting yaw rates, and the rear wheel angle sensor is used for collecting rear wheel angles. Each sensor is electrically connected to the rear wheel steering control device 4.
The rear wheel steering control device 4 may be an ECU, for example.
The rear wheel steering motor 3 may be a dc brush motor or a dc brushless motor, for example.
Illustratively, an input end of the rear wheel steering mechanism 2 is connected to an output end of the rear wheel steering motor 3, and an output end of the rear wheel steering mechanism 2 is connected to the rear wheel. Alternatively, the output end of the rear wheel steering mechanism 2 may be connected to the rear wheel via a tie rod mechanism 5. The rear wheel steering angle sensor may be mounted on the tie rod mechanism 5. The rear wheel steering mechanism 2 may be of a Column type (e.g., column EPS, C-EPS), may be of a Pinion type (e.g., pinion EPS, P-EPS), or may be of a Rack type (e.g., rack EPS, R-EPS). The structure of the drawbar mechanism 5 is well known to those skilled in the art and will not be described in detail here.
Illustratively, the rear wheel steering control system further includes a speed reduction mechanism 6, such as a speed reducer. The output of the rear-wheel steering motor 3 may be connected to the input of the rear-wheel steering mechanism 2 via a reduction mechanism 6. The speed reduction mechanism 6 serves to reduce the rotation speed of the motor and increase the output torque of the motor.
Illustratively, the rear wheel steering control system further includes a normally-open clutch 7. The input end of the normally-open clutch 7 is connected with the input end of the rear wheel steering mechanism 2, and the output end of the normally-open clutch 7 is connected with the vehicle body and fixed with the vehicle body. The normally open clutch 7 is an electrically controlled clutch and is electrically connected to the rear wheel steering control device 4.
Accordingly, the vehicle has a front wheel steering function, and the rear wheel steering control device 4 is also configured to control the rear wheels to keep the rear wheel steering angle at the present time constant when the rear wheel steering motor 3 fails, which includes a motor failure or a motor overload.
Alternatively, when the rear-wheel steering motor 3 fails, the rear-wheel steering control device 4 controls the normally-open clutch 7 to be closed, so that the rear-wheel steering mechanism 2 is fixedly connected with the vehicle body, and the rear wheels are fixed with the rear-wheel steering mechanism 2, that is, the rear-wheel steering angle at the present time is kept constant.
The rear wheel steering motor 3 breaks down, and the rear wheel steering easily brings the potential safety hazard, and at this moment, the rear wheel corner is fixed, and the rear wheel no longer continues to turn to, and the front wheel steering function leads whole steering, can avoid the incident.
The rear wheel steering control system also illustratively includes a normally closed clutch 8. The input end of the normally closed clutch 8 is connected with the output end of the speed reducing mechanism, and the output end of the normally closed clutch 8 is connected with the input end of the rear wheel steering mechanism 2. The normally closed clutch 8 is an electrically controlled clutch and is electrically connected with the rear wheel steering control device 4.
Correspondingly, the vehicle has a front wheel steering function, and the rear wheel steering control device 4 is further configured to control the rear wheels to keep the rear wheel steering angle at the current moment unchanged when the rear wheel steering motor 3 fails and the failure is motor failure; when the rear wheel steering motor 3 is in failure and the failure is motor overload, if the rear wheel steering angle at the current moment is not 0, the rear wheel steering motor 3 is controlled to drive the rear wheel to steer, the rear wheel steering angle of the rear wheel after steering is 0, and the rear wheel steering angle is kept to be 0.
Alternatively, when the rear-wheel steering motor 3 fails and the failure is a motor failure, the rear-wheel steering control device 4 controls the normally-open clutch 7 to be closed, so that the rear-wheel steering mechanism 2 is fixedly connected with the vehicle body, and the rear wheels are fixed with the rear-wheel steering mechanism 2, namely, the rear-wheel steering angle at the current moment is kept unchanged; when the rear wheel steering motor 3 is in failure and the failure is motor overload, if the rear wheel steering angle at the current moment is not 0, the rear wheel steering control device 4 controls the rear wheel steering motor 3 to drive the rear wheel steering to recover the rear wheel steering angle to be 0 on the basis of the current rear wheel steering angle, and then the rear wheel steering control device 4 controls the normally closed clutch 8 to be opened again, so that the power of the rear wheel and the rear wheel steering motor 3 is cut off.
The rear wheel steering motor 3 has motor failure, the rear wheel steering easily brings potential safety hazards, the rear wheel steering angle is directly fixed at the moment, the rear wheel does not steer any more, and safety accidents can be avoided. The rear wheel steering motor 3 is overloaded, the motor can normally work in a short time, the steering power of the rear wheel is cut off after the steering angle of the rear wheel is restored to 0, the automobile steering is mainly performed by the front wheel, the rear wheel does not steer any more, and the safety of the automobile is very high.
In the embodiment of the disclosure, by responding to a vehicle steering command and acquiring vehicle state information of a vehicle, for example, the vehicle state information may include a steering wheel angle, a steering demand issued when a driver operates a steering wheel can be responded to in real time; determining a motor rotation angle of a rear wheel steering motor according to the vehicle state information and the transmission ratio from the rear wheel steering motor to the rear wheel, and controlling the rear wheel steering motor to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor; the calculation process of the motor rotation angle is simple, the calculation can be performed quickly, the control of the rear wheel steering is realized, and the steering flexibility is improved.
When the electric power steering system is adopted to control the front wheel to steer, the rear wheel steering motor is controlled to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor; the control that rear wheel turned to has been realized when satisfying the electronic power assisted steering of front wheel, improves vehicle operating stability, increases and turns to the flexibility, promotes people's driving experience.
Fig. 2 is a flowchart of a rear wheel steering control method according to an embodiment of the present disclosure. Referring to fig. 2, the method flow is executed by the rear wheel steering control device and may include the following steps.
And step 101, responding to a vehicle steering command, and acquiring vehicle state information of a vehicle.
And 102, determining the motor rotation angle of the rear wheel steering motor according to the vehicle state information and the transmission ratio from the rear wheel steering motor to the rear wheel.
And 103, controlling the rear wheel steering motor to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor.
In the embodiment of the disclosure, by responding to a vehicle steering command and acquiring vehicle state information of a vehicle, for example, the vehicle state information may include a steering wheel angle, a steering demand issued when a driver operates a steering wheel can be responded to in real time; determining the motor rotation angle of a rear wheel steering motor according to the vehicle state information and the transmission ratio from the rear wheel steering motor to the rear wheel, and controlling the rear wheel steering motor to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor; the calculation process of the motor rotation angle is simple, the calculation can be performed quickly, the control of the rear wheel steering is realized, and the steering flexibility is improved.
When the electric power steering system is adopted to control the front wheel to steer, the rear wheel steering motor is controlled to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor; the control that rear wheel turned to has been realized when satisfying the electronic power assisted steering of front wheel, improves vehicle operating stability, increases and turns to the flexibility, promotes people's driving experience.
Fig. 3 is a flowchart of a rear wheel steering control method according to an embodiment of the present disclosure. Referring to fig. 3, the method flow is executed by the rear wheel steering control device and may include the following steps.
The vehicle state information may include a steering wheel angle, a vehicle speed, a yaw rate, and a rear wheel angle.
The rear-wheel steering control apparatus may acquire the vehicle state information of the vehicle at the present time through the aforementioned sensor group.
In step 202, the ideal yaw rate may be calculated according to the following formula (1)
In the formula (1), θ sw Is a steering wheel corner; v. of x Is the vehicle speed; l is the vehicle wheel base; i.e. i d Is a steering transmission ratio; m is the mass of the whole vehicle; a is the distance from the center of mass of the automobile to the front axle; b is the distance from the center of mass of the automobile to the rear axle; c ar Is the tire sidewall deflection stiffness of the rear wheel; c af The tire sidewall deflection rigidity of the front wheel tire.
Steering gear ratio i d Can be calculated by the formula (2).
And step 203, determining an ideal rear wheel steering angle according to the deviation of the yaw rate and the ideal yaw rate and the transfer function from the rear wheel steering angle to the yaw rate.
In this embodiment, the transfer function from the rear wheel rotation angle to the yaw rate may be derived through a two-degree-of-freedom model of the entire vehicle. The two-degree-of-freedom model of the whole vehicle can be represented by formula (3).
In the formula (3), ω is r The yaw angular velocity of the automobile; beta is the automobile mass center slip angle; delta r The rear wheel steering angle of the vehicle at the current moment; delta f The turning angle of the front wheel of the vehicle at the current moment; m is the mass of the whole vehicle; v. of x Is the vehicle speed; c af The tire sidewall deflection stiffness of the front wheel; c ar Is the tire sidewall deflection stiffness of the rear wheel; a is the distance from the center of mass of the automobile to the front axle; b is the distance from the mass center of the automobile to the rear axle; i is z The moment of inertia of the automobile around the Z axis; theta sw Is the steering wheel angle.
Equation (3) may be expressed in the form as shown in equation (4):
respectively angle delta of the rear wheel in the formula (4) r And yaw angular velocity ω r By performing the rahralski transformation as a variable, the transfer function G from the rear wheel angle to the yaw rate can be extracted as shown in equation (5).
In step 203, the ideal rear wheel steering angle δ * Can be calculated by the formula (6).
And step 204, determining the motor rotation angle of the rear wheel steering motor according to the deviation of the rear wheel steering angle and the ideal rear wheel steering angle and the transmission ratio from the rear wheel steering motor to the rear wheel.
In step 204, the motor rotation angle δ of the rear wheel steering motor e Can be calculated by the formula (7).
In the formula (7), δ r I is the rear wheel steering angle of the vehicle at the present moment, and i is the transmission ratio from the rear wheel steering motor to the rear wheel steering angle.
It is realized through steps 202 to 204 that the motor rotation angle of the rear wheel steering motor is determined according to the vehicle state information and the transmission ratio from the rear wheel steering motor to the rear wheel, and the rear wheel steering motor is connected with the rear wheel through the rear wheel steering mechanism.
And step 205, controlling the rear wheel steering motor to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor.
Alternatively, the motor rotation angle of the rear wheel steering motor corresponds one-to-one to the operating current of the rear wheel steering motor. According to the motor rotation angle of the rear wheel steering motor, the rear wheel steering control device can determine the working current of the corresponding rear wheel steering motor, and then adjust the working current of the rear wheel steering motor, so that the axial rotation angle of the output shaft of the rear wheel steering motor is the calculated motor rotation angle, the rear wheel is driven to steer, and the steering angle is the corresponding rear wheel rotation angle.
The application scenario of step 206 includes the vehicle having front steering capability. Faults include motor overload and motor failure.
The motor overload detection mode comprises the following steps: and detecting the working current and the working voltage of the motor, and determining that the motor is overloaded when the working current of the motor exceeds the rated working current and the working voltage of the motor exceeds the rated working voltage.
The detection mode of the motor failure comprises the following steps: and detecting the working current and the working voltage of the motor, and determining that the motor fails when the working current of the motor is lower than a current set value and the working voltage of the motor is lower than a voltage set value. The current set point and the voltage set point may both be 0.
When the rear wheel steering motor fails, step 207 is executed.
And step 207, carrying out fault response.
The embodiment of the invention provides two fault response modes.
In a first fault response mode, different faults support unified response: when the rear wheel steering motor fails (the motor fails or the motor is overloaded), the rear wheels are controlled to keep the rear wheel steering angle at the current moment unchanged.
In the second fault response mode, different faults correspond to different responses: when the rear wheel steering motor fails and the failure is motor failure, controlling the rear wheel to keep the rear wheel steering angle at the current moment unchanged; when the rear wheel steering motor breaks down and the fault is motor overload, if the rear wheel corner at the current moment is not 0, controlling the rear wheel steering motor to drive the rear wheel to steer, and keeping the rear wheel corner of the rear wheel after steering as 0, and keeping the rear wheel corner as 0; when the rear wheel steering motor fails and the failure is motor overload, if the rear wheel steering angle at the current moment is 0, the rear wheel steering angle is kept to be 0.
The embodiments of "keeping the rear wheel steering angle at the present time constant" and "keeping the rear wheel steering angle at 0 constant" may be implemented by the rear wheel steering device by controlling the normally-open clutch and the normally-closed clutch, and refer to the foregoing specifically, and will not be described in detail here. In "keeping the rear wheel steering angle at the present time constant" and "keeping the rear wheel steering angle 0 constant", the holding time may be until the failure is eliminated. The failure elimination may be that the rear-wheel steering control means determines that there is no failure in the operation of the rear-wheel steering motor, for example, that the operating current and the operating voltage of the motor are both within a normal current range and voltage range.
In the embodiment of the disclosure, by responding to a vehicle steering command and acquiring vehicle state information of a vehicle, for example, the vehicle state information may include a steering wheel angle, a steering demand issued when a driver operates a steering wheel can be responded to in real time; determining a motor rotation angle of a rear wheel steering motor according to the vehicle state information and the transmission ratio from the rear wheel steering motor to the rear wheel, and controlling the rear wheel steering motor to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor; the calculation process of the motor rotation angle is simple, the calculation can be performed quickly, the control of the rear wheel steering is realized, and the steering flexibility is improved.
When the electric power steering system is adopted to control the steering of the front wheels, the rear wheel steering motor is controlled to drive the rear wheels to steer according to the motor rotation angle of the rear wheel steering motor; the control that rear wheel turned to has been realized when satisfying the electronic power assisted steering of front wheel, improves vehicle operating stability, increases and turns to the flexibility, promotes people's driving experience.
In addition, the rear wheel steering control method can assist the front wheel electric power steering function, related external parameters comprise steering wheel turning angles, vehicle speed and the like, part of the external parameters (such as the steering wheel turning angles, the vehicle speed and the like) can be shared with the front wheel electric power steering function, only a small amount of external parameters (such as rear wheel turning angles and the like) need to be acquired independently, the number of the acquired parameters is small, the process of calculating the motor turning angles through the external parameters is simple, the whole rear wheel steering control method is easy to achieve, and the calculation efficiency is high.
Fig. 4 is a schematic structural diagram of a rear wheel steering control device provided in an embodiment of the present disclosure, and referring to fig. 4, the rear wheel steering control device includes an obtaining module 401, a determining module 402, and a control module 403.
The obtaining module 401 is configured to obtain vehicle state information of a vehicle in response to a vehicle steering instruction.
A determination module 402 determines a motor angle of the rear-wheel steering motor based on the vehicle state information and a transmission ratio of the rear-wheel steering motor to the rear wheels.
And a control module 403, configured to control the rear wheel steering motor to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor.
In a first alternative embodiment, the vehicle state information includes a steering wheel angle, a vehicle speed, a yaw rate, and a rear-wheel steering angle, and the determining module 402 is configured to determine an ideal yaw rate based on the steering wheel angle and the vehicle speed; determining an ideal rear wheel corner according to the deviation between the yaw rate and the ideal yaw rate and the transfer function from the rear wheel corner to the yaw rate; and determining the motor rotation angle of the rear wheel steering motor according to the deviation of the rotation angle of the rear wheel from the ideal rear wheel rotation angle and the transmission ratio from the rear wheel steering motor to the rear wheel.
In a second alternative embodiment, the determining module 402 is configured to calculate the ideal rear wheel steering angle according to equation (6).
In a third alternative embodiment, the vehicle has a front wheel steering function, and accordingly, the control module 403 is further configured to control the rear wheel to keep the rear wheel steering angle at the current time unchanged when the rear wheel steering motor fails, or to keep the rear wheel steering angle at the current time unchanged when the rear wheel steering motor fails and the failure is motor failure, and to control the rear wheel steering motor to drive the rear wheel to steer and keep the rear wheel steering angle at the steered position of 0 when the rear wheel steering motor fails and the failure is motor overload if the rear wheel steering motor fails and the failure is motor overload.
In the embodiment of the disclosure, by responding to a vehicle steering command and acquiring vehicle state information of a vehicle, for example, the vehicle state information may include a steering wheel angle, a steering demand issued when a driver operates a steering wheel can be responded to in real time; determining a motor rotation angle of a rear wheel steering motor according to the vehicle state information and the transmission ratio from the rear wheel steering motor to the rear wheel, and controlling the rear wheel steering motor to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor; the calculation process of the motor rotation angle is simple, the calculation can be performed quickly, the control of the rear wheel steering is realized, and the steering flexibility is improved.
Fig. 5 is a block diagram showing a configuration of a rear wheel steering control apparatus according to an exemplary embodiment of the present invention. The rear wheel steering control device 300 may be a computer.
The rear wheel steering control device 300 includes a Central Processing Unit (CPU) 301, a system memory 304 including a Random Access Memory (RAM) 302 and a Read Only Memory (ROM) 303, and a system bus 305 connecting the system memory 304 and the central processing unit 301. The rear wheel steering control device 300 also includes a basic input/output system (I/O system) 306, which facilitates transfer of information between various components within the computer, and a mass storage device 307 for storing an operating system 313, application programs 314, and other program modules 315.
The basic input/output system 306 comprises a display 308 for displaying information and an input device 309, such as a mouse, keyboard, etc., for a user to input information. Wherein a display 308 and an input device 309 are connected to the central processing unit 301 through an input-output controller 310 connected to the system bus 305. The basic input/output system 306 may also include an input/output controller 310 for receiving and processing input from a number of other devices, such as a keyboard, mouse, or electronic stylus. Similarly, an input-output controller 310 may also provide output to a display screen, a printer, or other type of output device.
The mass storage device 307 is connected to the central processing unit 301 through a mass storage controller (not shown) connected to the system bus 305. The mass storage device 307 and its associated computer-readable media provide non-volatile storage for the rear wheel steering control apparatus 300. That is, mass storage device 307 may include a computer readable medium (not shown) such as a hard disk or CD-ROM drive.
Without loss of generality, computer readable media may comprise computer storage media and communication media. Computer storage 13 media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes RAM, ROM, EPROM, EEPROM, flash memory or other solid state memory technology, CD-ROM, DVD, or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices. Of course, those skilled in the art will appreciate that computer storage media is not limited to the foregoing. The system memory 304 and mass storage device 307 described above may be collectively referred to as memory.
According to various embodiments of the present invention, the rear wheel steering control device 300 may also be operated by a remote computer connected to a network through a network such as the internet. That is, the rear-wheel steering control device 300 may be connected to the network 312 through the network interface unit 311 connected to the system bus 305, or may be connected to another type of network or a remote computer system (not shown) using the network interface unit 311.
The memory further includes one or more programs, and the one or more programs are stored in the memory and configured to be executed by the CPU. The one or more programs include instructions for performing the rear wheel steering control method provided by the embodiments of the present invention.
It should be noted that: the rear wheel steering control device provided in the above embodiment is only illustrated by dividing the above functional modules when controlling the rear wheel steering, and in practical applications, the above function distribution may be completed by different functional modules according to needs, that is, the internal structure of the apparatus is divided into different functional modules to complete all or part of the above described functions. In addition, the rear wheel steering control device provided by the above embodiment and the rear wheel steering control method embodiment belong to the same concept, and the specific implementation process thereof is detailed in the method embodiment and is not described herein again.
It will be understood by those skilled in the art that all or part of the steps for implementing the above embodiments may be implemented by hardware, or may be implemented by a program instructing relevant hardware, where the program may be stored in a computer-readable storage medium, and the above-mentioned storage medium may be a read-only memory, a magnetic disk or an optical disk, etc.
The above description is intended only to illustrate the preferred embodiments of the present disclosure, and should not be taken as limiting the disclosure, as any modifications, equivalents, improvements and the like which are within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.
Claims (8)
1. A rear wheel steering control method characterized by comprising:
acquiring vehicle state information of a vehicle in response to a vehicle steering command, the vehicle state information including a steering wheel angle, a vehicle speed, a yaw rate, and a rear wheel steering angle;
determining an ideal yaw rate according to the steering wheel angle and the vehicle speed;
determining an ideal rear wheel corner according to the deviation of the yaw rate and the ideal yaw rate and the transfer function from the rear wheel corner to the yaw rate; the transfer function from the rear wheel turning angle to the yaw rate is obtained through derivation of a two-degree-of-freedom model of the whole vehicle, and the transfer function G from the rear wheel turning angle to the yaw rate is expressed by the following formula:
in the formula, ω r The yaw angular velocity of the automobile; beta is the automobile mass center slip angle; delta r The rear wheel steering angle of the vehicle at the current moment; delta f The turning angle of the front wheel of the vehicle at the current moment; m is the mass of the whole vehicle; v. of x Is the vehicle speed; c af The tire sidewall deflection stiffness of the front wheel tire; c ar Is the tire sidewall deflection stiffness of the rear wheel; a is the distance from the center of mass of the automobile to the front axle; b is the distance from the mass center of the automobile to the rear axle; i is z The moment of inertia of the automobile around the Z axis; theta sw Is a steering wheel corner;
determining a motor rotation angle of the rear wheel steering motor according to the deviation of the rear wheel rotation angle and the ideal rear wheel rotation angle and the transmission ratio from the rear wheel steering motor to a rear wheel;
and controlling the rear wheel steering motor to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor.
2. The rear-wheel steering control method according to claim 1, wherein the determining an ideal rear-wheel steering angle from the deviation of the yaw rate from the ideal yaw rate and a transfer function of a rear-wheel steering angle to the yaw rate includes:
the ideal rear wheel turning angle is calculated according to the following formula,
δ * ideal rear wheel angle, omega r Is the yaw rate of the vehicle,
for an ideal yaw rate, G is the transfer function of the rear wheel steering angle to the yaw rate.
3. The rear wheel steering control method according to claim 1, wherein the vehicle is provided with a front wheel steering function,
the rear wheel steering control method further includes:
when the rear wheel steering motor is in failure, controlling the rear wheel to keep the rear wheel steering angle at the current moment unchanged, or,
when the rear wheel steering motor fails and the failure is motor failure, the rear wheel is controlled to keep the rear wheel steering angle at the current moment unchanged, and when the rear wheel steering motor fails and the failure is motor overload, if the rear wheel steering angle at the current moment is not 0, the rear wheel steering motor is controlled to drive the rear wheel to steer and the rear wheel steering angle of the rear wheel after steering is 0, and the rear wheel steering angle is kept to be 0 unchanged.
4. A rear wheel steering control device characterized by comprising:
the vehicle state information comprises a steering wheel angle, a vehicle speed, a yaw rate and a rear wheel steering angle;
the determining module is used for determining an ideal yaw rate according to the steering wheel turning angle and the vehicle speed;
determining an ideal rear wheel corner according to the deviation of the yaw rate and the ideal yaw rate and the transfer function from the rear wheel corner to the yaw rate; the transfer function from the rear wheel turning angle to the yaw rate is obtained through derivation of a two-degree-of-freedom model of the whole vehicle, and the transfer function G from the rear wheel turning angle to the yaw rate is expressed by the following formula:
in the formula, ω r The yaw angular velocity of the automobile; beta is the automobile mass center slip angle; delta. For the preparation of a coating r The rear wheel steering angle of the vehicle at the current moment; delta f The turning angle of the front wheel of the vehicle at the current moment; m is the mass of the whole vehicle; v. of x Is the vehicle speed; c af The tire sidewall deflection stiffness of the front wheel tire; c ar Is the tire sidewall deflection stiffness of the rear wheel; a is the distance from the center of mass of the automobile to the front axle; b is the distance from the center of mass of the automobile to the rear axle; I.C. A z The moment of inertia of the automobile around the Z axis; theta sw Is a steering wheel corner;
determining a motor rotation angle of the rear wheel steering motor according to the deviation of the rear wheel rotation angle and the ideal rear wheel rotation angle and the transmission ratio from the rear wheel steering motor to a rear wheel;
and the control module is used for controlling the rear wheel steering motor to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor.
5. The rear wheel steering control device according to claim 4, wherein the determining module is configured to,
the ideal rear wheel turning angle is calculated according to the following formula,
δ * ideal rear wheel angle, omega r Is the yaw rate of the vehicle,
for an ideal yaw rate, G is the transfer function of the rear wheel steering angle to the yaw rate.
6. A rear wheel steering control apparatus comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that the processor is configured to implement the rear wheel steering control method according to any one of claims 1-3 when executing the computer program.
7. A computer storage medium having stored therein at least one instruction that is loaded and executed by a processor to implement the rear wheel steering control method of any of claims 1-3.
8. A rear-wheel steering control system, characterized by comprising:
a sensor group;
a rear wheel steering mechanism;
a rear wheel steering motor;
a rear wheel steering control device;
the sensor group is used for collecting vehicle state information of the vehicle;
the rear wheel steering control device is used for responding to a vehicle steering instruction and acquiring vehicle state information of the vehicle, which is acquired by the sensor group, wherein the vehicle state information comprises a steering wheel angle, a vehicle speed, a yaw rate and a rear wheel steering angle;
determining an ideal yaw rate according to the steering wheel angle and the vehicle speed;
determining an ideal rear wheel corner according to the deviation of the yaw rate and the ideal yaw rate and the transfer function from the rear wheel corner to the yaw rate; the transfer function from the rear wheel turning angle to the yaw rate is obtained through derivation of a two-degree-of-freedom model of the whole vehicle, and the transfer function G from the rear wheel turning angle to the yaw rate is expressed by the following formula:
in the formula, ω r The yaw angular velocity of the automobile; beta is the automobile mass center slip angle; delta r The rear wheel steering angle of the vehicle at the current moment; delta f The turning angle of the front wheel of the vehicle at the current moment; m is the mass of the whole vehicle; v. of x Is the vehicle speed; c af The tire sidewall deflection stiffness of the front wheel; c ar Is the tire sidewall deflection stiffness of the rear wheel; a is the distance from the center of mass of the automobile to the front axle; b is the distance from the center of mass of the automobile to the rear axle; i is z The moment of inertia of the automobile around the Z axis; theta.theta. sw Is a steering wheel corner;
determining a motor rotation angle of the rear wheel steering motor according to the deviation of the rear wheel rotation angle and the ideal rear wheel rotation angle and the transmission ratio from the rear wheel steering motor to a rear wheel;
and controlling the rear wheel steering motor to drive the rear wheel to steer according to the motor rotation angle of the rear wheel steering motor.
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