CN116373992A - Road feel torque determination method and device for steer-by-wire system and storage medium - Google Patents
Road feel torque determination method and device for steer-by-wire system and storage medium Download PDFInfo
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- CN116373992A CN116373992A CN202310238195.2A CN202310238195A CN116373992A CN 116373992 A CN116373992 A CN 116373992A CN 202310238195 A CN202310238195 A CN 202310238195A CN 116373992 A CN116373992 A CN 116373992A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D6/00—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits
- B62D6/008—Control of feed-back to the steering input member, e.g. simulating road feel in steer-by-wire applications
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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
- B62D5/0463—Controlling the motor calculating assisting torque from the motor based on driver input
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
Abstract
The invention provides a road feel torque determining method and device for a steering-by-wire system and a storage medium, wherein the road feel torque determining method for the steering-by-wire system comprises the following steps: calculating the coulomb friction compensation moment T c The method comprises the steps of carrying out a first treatment on the surface of the Compensating moment T based on coulomb friction c Steering wheel torque T f Damping moment T damp Determining the operator input torque divides the overall system architecture into a steering wheel subsystem and an active steering subsystem, and road feel torque is represented by an automobile model that delivers current from the road feel motor to the steering wheel torque. A road torque expression related to the speed and road condition is designed for the steering wheel subsystem, the torque expression is corrected by utilizing a damping model and a coulomb friction model, and the tracking precision is improved by processing complex friction parameter estimation based on a back-stepping method.
Description
Technical Field
The invention relates to a road feel moment acquisition technology, and belongs to the technical field of intelligent driving steering control of automobiles.
Background
As a new trend of development of automobile steering systems, steer-by-wire technology is gradually applied to modern intelligent automobiles. The system eliminates the mechanical connection structure of the traditional steering column, is beneficial to enlarging the operation space of a driver and reduces the weight of an automobile. However, due to such a change, the driver cannot apply torque to the front wheels, and the feedback torque transmitted by the mechanical structure is also interrupted, and the driver does not feel feedback information from the road surface, resulting in a deteriorated driving experience, and the driving of the vehicle is more dangerous. In response to the above problems, a road sensing motor in the steering wheel subsystem is used to provide a feedback torque, a steering actuator motor in the active steering subsystem provides a steering angle consistent with the driver's operational intent, and the controllers of the two subsystems are integrated into the ECU.
The road feel in SBW needs to be freely designed to match the driver's operation feel and to observe the moment of road feedback to the system with the real-time current of the steering actuator motor. The road feedback torque is defined as a torque that varies with the state of the vehicle, such as steering wheel angle, vehicle speed, lateral acceleration, etc. It is believed that these conditions have the greatest effect on steering wheel torque. The desired feedback torque is considered to meet the following design requirements: the gradient of the lateral acceleration under the low-speed working condition is relatively small, in this case, the driver has weak perception of the lateral acceleration change caused by the angle of the front wheel, the driver easily perceives the change of the angle of the steering wheel, and correspondingly, the torque of the steering wheel under the high-speed working condition is mainly influenced by the lateral acceleration.
Disclosure of Invention
The invention aims to provide a method, a device and a storage medium for determining road feel torque of a novel drive-by-wire steering system with friction compensation, which can improve prediction accuracy.
In order to solve the technical problems, the invention adopts the following technical scheme:
the invention firstly provides a road feel torque determining method of a steer-by-wire system, which comprises the following steps:
calculating the coulomb friction compensation moment T c ：
Wherein a is c For coulomb friction moment coefficient (the parameter automobile is fixed when leaving the factory), b c For gradient change coefficients, to represent the speed of the process transformation (this parameter is obtained by matlab simulation experiments),
for the rotational speed of the steering wheel (measured with an angular velocity sensor);
compensating moment T based on coulomb friction c Steering wheel torque T f Damping moment T damp Determining a driver input torque:
T 1 ＝T f +T c +T damp
wherein T is 1 Torque is input for the driver.
Steering wheel torque T f The method comprises the following steps:
T f ＝T m -k(v)T l -(1-k(v))T h
T l ＝(a 1 v+b 1 )(1-e -c1δ1 )
T h ＝(a 2 v+b 2 )(1-e -c2ay )
wherein T is m Is the electromagnetic torque of the road sensing motor, T l Is the feedback moment at low speed, T h Is the feedback torque at high speed (torque is obtained by a torque sensor), k (v) is a weight function of the switching process of high speed and low speed, v is the vehicle speed, a y For lateral acceleration, a 1 、b 1 、a 2 、b 2 、c 1 、c 2 A constant greater than 0 (the values are all between 0 and 30, the coefficients a and b relate to the state of the automobile, the parameter c relates to the running environment of the automobile, delta 1 Is the steering wheel angle.
Electromagnetic torque T of road-sensing motor m The method comprises the following steps:
wherein J is m For the moment of inertia (motor delivery parameter) of the road sensing motor, B m K is the damping coefficient (motor delivery parameter) of the road sensing motor s For torsional rigidity of steering column (motor delivery parameter), θ m G is the angle of the road sensing motor (which can be obtained by an angle sensor) m Is the reduction ratio (motor delivery parameter) of the road sensing motor reducer,
for the angular velocity of the road-sensing motor (obtained by an angular velocity sensor),/for the road-sensing motor>
The angular acceleration (the angular velocity) of the road-sensing motor is derived.
The weight function k (v) for the high and low speed switching process is expressed as:
the weight function is constrained by the following conditions:
wherein m is the vehicle mass, n is the vehicle acceleration coefficient (which is mainly divided according to the acceleration of the vehicle, n is 5-8 when the vehicle acceleration is larger than 0.2g, p is the vehicle motion coefficient (the intrinsic parameter of the vehicle), q is the correction parameter, v l A low-speed demarcation point (30 km/h) for the automobile; v h Is a high-speed demarcation point (80 km/h) for automobiles.
Damping moment T damp The method comprises the following steps:
wherein C is damp K is a function of vehicle speed damp Is a damping adjustment coefficient.
The invention also provides a road feel torque determining device of the steer-by-wire system, which is characterized by comprising a processor and a memory; the memory stores programs or instructions that are loaded and executed by the processor to implement the steps of the steer-by-wire system road feel torque determination method.
The present invention also provides a computer readable storage medium having stored thereon a program or instructions that when executed by a processor, perform the steps of the steer-by-wire road feel torque determination method.
Compared with the prior art, the invention has the following advantages:
(1) In the case of high-speed driving, a slight rotation of the steering wheel causes a large change in the lateral acceleration of the vehicle. In addition, the invention also considers the actual driving requirement, and requires the steering wheel to be capable of automatically resetting, so that damping torque related to the speed of the steering wheel and the speed of the vehicle is introduced. This is lacking in the current friction compensation torque determination schemes. In addition, in order to prevent the steering wheel from shaking caused by abrupt torque change, a tangential function is introduced at the forward and reverse process change to make correction.
(2) The road feeling moment after friction compensation provided by the invention is basically consistent with the design moment in terms of variation trend and numerical value. When the steering wheel keeps a certain rotation direction, the error fluctuation coefficient is smaller and the robustness is stronger under the condition of high adhesion coefficient or low adhesion coefficient. The friction compensation strategy of the road-sensing motor can eliminate friction interference of different road adhesion coefficients, so that the road-sensing motor output is output according to actual preset torque.
(3) The road sensing moment designed by the invention is matched with the traditional EPS system, can adapt to various complex road surface working conditions and different vehicle speed running working conditions, and improves the self-adaptation of the road sensing moment to complex environments. The algorithm accurately acquires the design torque based on the automatically identified friction characteristics, reduces the torque fluctuation of the steering wheel, and improves the steering stability of the vehicle.
Drawings
FIG. 1 is a schematic diagram of a steer-by-wire steering wheel subsystem;
fig. 2 coulomb friction compensation control.
Detailed Description
The present invention will be described in further detail with reference to the following examples and drawings, wherein the exemplary embodiments of the present invention and the descriptions thereof are for the purpose of illustration only and are not limiting the invention. The following describes the embodiments of the present invention further with reference to the examples of the accompanying drawings.
The invention discloses a road feel torque determining method of a steer-by-wire system, which comprises the following steps of:
step one, calculating Coulomb friction compensation moment T c ：
Wherein a is c B is the coulomb friction moment coefficient c Is a gradient change coefficient, used to represent the speed of the process transformation,
is the rotational speed of the steering wheel;
step two, compensating the moment T according to coulomb friction c Steering wheel torque T f Damping moment T damp Determining a driver input torque:
T 1 ＝T f +T c +T damp
wherein T is 1 Torque is input for the driver.
In the steering wheel subsystem, signals generated by the steering wheel angle sensor, the torque sensor and the active steering subsystem are sent to the road feel controller for processing. The output control signal enables the road feel motor to simulate road feel which accords with the preference of a driver, so that the driver can sense information from a road surface, and the final driver input torque is obtained through combining steering wheel torque, coulomb friction compensation torque and damping torque.
Steering wheel torque is designed as a function of vehicle speed and steering wheel angle, and feedback torque is adjusted by varying the gain of the various control parameters. Selecting a reduced order modeling method, establishing a dynamic model of a steering wheel subsystem, and solving a dynamic transfer model between a steering wheel and a torque sensor:
wherein J is 1 For moment of inertia, B 1 Delta as damping coefficient 1 Is the steering wheel angle; t (T) 1 To drive input torque, T s Is a torque sensor value.
A torque sensor dynamics model is built, which can be expressed as:
T s ＝K s (δ 1 -θ m )/G m
wherein K is s For torsional rigidity of steering column, θ m G is the angle of the road sensing motor m Is the reduction ratio of the road sensing motor speed reducer.
Establishing a dynamic model between the moment sensor and the road-sensing motor, wherein the dynamic model can be expressed as:
wherein J is m For the moment of inertia (motor delivery parameter) of the road sensing motor, B m K is the damping coefficient (motor delivery parameter) of the road sensing motor s For torsional rigidity of steering column (motor delivery parameter), θ m G is the angle of the road sensing motor (which can be obtained by an angle sensor) m Is the reduction ratio (motor delivery parameter) of the road sensing motor reducer,
for the angular velocity of the road-sensing motor (obtained by an angular velocity sensor),/for the road-sensing motor>
The angular acceleration (the angular velocity) of the road-sensing motor is derived.
A method for designing a road-sensing motor current based on measuring a steering actuator motor current to be equivalent to a road load is proposed, and an electric balance equation of the road-sensing motor can be expressed as:
wherein U is m 、I m 、R m 、L m 、k e 、k t The voltage, current, resistance, inductance, back electromotive force coefficient and electromagnetic torque coefficient of the road induction motor. The current can pass through the controllerThe resistance sampling method is used for obtaining the resistance sampling method, and the expression is as follows:
T m ＝k t I m
SBW uses the real-time current of the steering actuator motor to observe the torque that the road feeds back to the system, the desired feedback torque needs to meet the following design requirements: the gradient of the lateral acceleration under the low-speed working condition is relatively small, in this case, the driver has weak perception of the lateral acceleration change caused by the angle of the front wheel, the driver easily perceives the change of the angle of the steering wheel, and correspondingly, the torque of the steering wheel under the high-speed working condition is mainly influenced by the lateral acceleration. The desired feedback torque expression is:
T f ＝T m -k(v)T l -(1-k(v))T h
T l ＝(a 1 v+b 1 )(1-e -c1δ1 )
T h ＝(a 2 v+b 2 )(1-e -c2ay )
wherein T is m Is the electromagnetic torque of the road sensing motor, T l Is the feedback moment at low speed, T h Is the feedback torque at high speed (torque is obtained by a torque sensor), k (v) is a weight function of the switching process of high speed and low speed, v is the vehicle speed, a y For lateral acceleration, a 1 、b 1 、a 2 、b 2 、c 1 、c 2 A constant greater than 0 (the values are all between 0 and 30, the coefficients a and b relate to the state of the automobile, the parameter c relates to the running environment of the automobile, delta 1 Is the steering wheel angle.
In order to ensure the stable transition of the feedback moment at different speeds, a weight function is introduced, and the expression is as follows:
the weight function is constrained by the following conditions:
wherein m is the vehicle mass, n is the vehicle acceleration coefficient (which is mainly divided according to the acceleration of the vehicle, n is 5-8 when the vehicle acceleration is larger than 0.2g, p is the vehicle motion coefficient (the intrinsic parameter of the vehicle), q is the correction parameter, v l A low-speed demarcation point (30 km/h) for the automobile; v h Is a high-speed demarcation point (80 km/h) for automobiles.
In a high-speed driving scenario, a small steering wheel rotation causes a drastic change in the lateral acceleration of the vehicle. In addition, considering actual driving demand, the steering wheel is required to be capable of being automatically reset, and the overshoot is minimum. Therefore, the damping moment is increased on the basis of the road feel moment. The invention designs the damping control moment as a function of steering wheel speed and vehicle speed, and the expression is:
wherein T is damp For damping moment, C damp K is a function of vehicle speed damp Is a damping adjustment coefficient.
In order to prevent steering wheel shake caused by abrupt torque change under the condition of small torque change when the coulomb friction model is adopted to compensate the switching direction, a tangent function is added at the forward and reverse switching points, and the coulomb friction compensation moment after tangent correction is expressed as:
the final road feel moment can be expressed as:
T 1 ＝T f +T c +T damp
the foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (8)
1. A method for determining road feel torque of a steer-by-wire system, comprising:
calculating the coulomb friction compensation moment T c ：
Wherein a is c Is the coulomb friction torque coefficient; b c Is a gradient change coefficient, used to represent the speed of the process transformation,
is the rotational speed of the steering wheel;
compensating moment T based on coulomb friction c Steering wheel torque T f Damping moment T damp Determining a driver input torque:
T 1 ＝T f +T c +T damp
wherein T is 1 Torque is input for the driver.
2. The method for determining road feel torque for a steer-by-wire system according to claim 1, wherein the steering wheel torque T f The method comprises the following steps:
T f ＝T m -k(v)T l -(1-k(v))T h
T l ＝(a 1 v+b 1 )(1-e -c1δ1 )
T h ＝(a 2 v+b 2 )(1-e -c2ay )
wherein T is m Is the electromagnetic torque of the road sensing motor, T l Is the feedback moment at low speed, T h Is the feedback moment at high speed, k (v) is the weight function of the switching process at high speed and low speedNumber v is vehicle speed, a y For lateral acceleration, a 1 、b 1 、a 2 、b 2 、c 1 、c 2 A constant greater than 0, delta 1 Is the steering wheel angle.
3. The road feel torque determination method of a steer-by-wire system according to claim 2, characterized in that the electromagnetic torque T of the road feel motor m The method comprises the following steps:
wherein J is m For the moment of inertia of the road-sensing motor, B m K is the damping coefficient of the road sensing motor s For torsional rigidity of steering column, θ m G is the angle of the road sensing motor m Is the reduction ratio of the speed reducer of the road sensing motor,
for the angular speed of the road-sensing motor, +.>
Is the angular acceleration of the road sensing motor.
4. A steering-by-wire system road feel torque determination method according to claim 3, characterized in that the weight function k (v) of the high-speed and low-speed switching process is expressed as:
the weight function is constrained by the following conditions:
wherein m is the mass of the vehicleN is the acceleration coefficient of the automobile, q is the correction parameter, v l Is a low-speed demarcation point of the automobile; v h Is a high-speed demarcation point of the automobile.
5. The method for determining road feel torque for a steer-by-wire system according to claim 4, wherein the acceleration coefficient n is determined according to the magnitude of acceleration of the vehicle:
when the acceleration of the automobile is larger than 0.2g, n is 5-8;
when the acceleration of the automobile is less than 0.2g, n is 2-3.
6. The method for determining road feel torque for a steer-by-wire system according to claim 5, wherein the damping torque T damp The method comprises the following steps:
wherein C is damp K is a function of vehicle speed damp Is a damping adjustment coefficient.
7. The road feel torque determining device of the steer-by-wire system is characterized by comprising a processor and a memory; stored in the memory are programs or instructions that are loaded and executed by the processor to implement the steps of the steer-by-wire road feel torque determination method of any one of claims 1 to 6.
8. A computer readable storage medium having stored thereon a program or instructions which, when executed by a processor, implement the steps of the steer-by-wire road feel torque determination method of any one of claims 1 to 6.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310238195.2A CN116373992A (en) | 2023-03-14 | 2023-03-14 | Road feel torque determination method and device for steer-by-wire system and storage medium |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202310238195.2A CN116373992A (en) | 2023-03-14 | 2023-03-14 | Road feel torque determination method and device for steer-by-wire system and storage medium |
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| CN116373992A true CN116373992A (en) | 2023-07-04 |
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| CN202310238195.2A Pending CN116373992A (en) | 2023-03-14 | 2023-03-14 | Road feel torque determination method and device for steer-by-wire system and storage medium |
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- 2023-03-14 CN CN202310238195.2A patent/CN116373992A/en active Pending
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