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CN117284366B - Drive-by-wire steering system considering driver force decay and road feel control method thereof - Google Patents

Drive-by-wire steering system considering driver force decay and road feel control method thereof Download PDF

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CN117284366B
CN117284366B CN202311237277.1A CN202311237277A CN117284366B CN 117284366 B CN117284366 B CN 117284366B CN 202311237277 A CN202311237277 A CN 202311237277A CN 117284366 B CN117284366 B CN 117284366B
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road feel
road
torque
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赵万忠
陈钰庭
周小川
张自宇
王春燕
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Qinhuai Innovation Research Institute Of Nanjing University Of Aeronautics And Astronautics
Nanjing University of Aeronautics and Astronautics
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Nanjing University of Aeronautics and Astronautics
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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
    • B62D5/0409—Electric motor acting on the steering column
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/16—Devices for psychotechnics; Testing reaction times ; Devices for evaluating the psychological state
    • A61B5/18—Devices for psychotechnics; Testing reaction times ; Devices for evaluating the psychological state for vehicle drivers or machine operators
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/316—Modalities, i.e. specific diagnostic methods
    • A61B5/389—Electromyography [EMG]
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    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D15/00—Steering not otherwise provided for
    • B62D15/02—Steering position indicators ; Steering position determination; Steering aids
    • B62D15/021—Determination of steering angle
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D15/00—Steering not otherwise provided for
    • B62D15/02—Steering position indicators ; Steering position determination; Steering aids
    • B62D15/021—Determination of steering angle
    • B62D15/0215—Determination of steering angle by measuring on the steering column
    • 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
    • B62D5/001—Mechanical components or aspects of steer-by-wire systems, not otherwise provided for in this maingroup
    • B62D5/005—Mechanical components or aspects of steer-by-wire systems, not otherwise provided for in this maingroup means for generating torque on steering wheel or input member, e.g. feedback
    • B62D5/006—Mechanical components or aspects of steer-by-wire systems, not otherwise provided for in this maingroup means for generating torque on steering wheel or input member, e.g. feedback power actuated
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D6/00—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits
    • 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
    • B62D6/007—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits adjustable by the driver, e.g. sport mode
    • 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
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
    • G06F17/10—Complex mathematical operations

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Abstract

本发明公开了一种考虑驾驶员力衰退的线控转向系统及其路感控制方法，包括：采集车辆的方向盘转矩信号、车速信号、转向执行电机转角转矩信号和驾驶员表面肌电信号，并对得到的驾驶员表面肌电信号进行处理，计算驾驶员肌肉激活度及驾驶员的转向不舒适度；计算考虑驾驶员力衰退的理想路感力矩；计算得理想路感力矩相应的电流，实时控制路感电机输出转矩跟踪理想路感力矩，以实现驾驶员实际转向不舒适度跟踪理想转向不舒适度。本发明的方法能够满足驾驶员对路感力的个性化需求，为驾驶员提供更好的驾驶体验和安全保障。

The present invention discloses a steer-by-wire system and a road feel control method thereof that takes into account the driver's force decay, including: collecting the vehicle's steering wheel torque signal, vehicle speed signal, steering execution motor angle torque signal and the driver's surface electromyography signal, and processing the obtained driver's surface electromyography signal, calculating the driver's muscle activation degree and the driver's steering discomfort; calculating the ideal road feel torque that takes into account the driver's force decay; calculating the current corresponding to the ideal road feel torque, and controlling the road feel motor output torque to track the ideal road feel torque in real time, so as to achieve the driver's actual steering discomfort tracking the ideal steering discomfort. The method of the present invention can meet the driver's personalized needs for road feel, and provide the driver with a better driving experience and safety guarantee.

Description

Drive-by-wire steering system considering driver force decay and road feel control method thereof
Technical Field
The invention belongs to the technical field of vehicle steering, and particularly relates to a steer-by-wire system considering driver force decay and a road feel control method thereof.
Background
In recent years, with the development of the automobile industry and the continuous improvement of the intelligent level, the requirements on the safety and the comfort of the automobile are increasingly increased, and the steering technology is developed towards the electric operation. The steer-by-wire system replaces the traditional mechanical connection by an electronic signal, and transmits a steering instruction of a driver to the steering system of the vehicle, so that the steering system has potential in improving the control performance and the driving comfort. Because of no mechanical connection, road feel of the steer-by-wire system is reduced to the driver by the road feel motor, so that the driver can feel similar control feel to the traditional mechanical power-assisted steering system when using the steer-by-wire system. The technology monitors the running information of the vehicle in real time by an electronic control unit, and simulates corresponding road feel force feedback by a road feel motor control system according to real-time road conditions. Compared with the traditional mechanical steering system, the steer-by-wire road feel simulation not only can provide the driver with the perception of the running state of the vehicle, but also can realize the personalized adjustment of the steering force. The driver can adjust the intensity and the characteristic of the steering force by adjusting the parameters of the electronic control unit so as to adapt to the requirements of different driving environments and driving styles and improve the driving safety and the comfort.
In order to solve the problems of road traffic safety and driving comfort caused by fatigue of a driver, the existing technical scheme monitors the physiological state and the attention level of the driver in real time through in-vehicle sensor and algorithm analysis, such as monitoring eye movement, facial expression, surface electromyographic signals and the like of the driver so as to early warn fatigue driving.
Myoelectric detection technology measures the electrical activity signal of muscles by placing a sensor on the driver. These sensors typically employ surface electrodes or wearable devices that are capable of recording changes in the muscle potential of the driver. By analyzing the signals, the decline degree of the muscle force of the driver can be judged, the fatigue state of the driver can be early warned in time, and traffic accidents caused by fatigue driving are avoided.
The conventional road feel simulation method has advanced to some extent in the aspect of individual design of road feel, and different drivers may have different perceptions and demands on road feel, and the conventional road feel simulation system can generally provide adjustable steering force feedback according to individual demands of the drivers. However, in the past road feel simulation method, less consideration is given to the physiological state of the driver, especially the fatigue state, and the method is difficult to provide help for relieving the fatigue state of the driver, so that better driving experience and safety guarantee are provided for the driver.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a steer-by-wire system considering the driver force degradation and a road feel control method thereof, so as to solve the problem of muscle force degradation caused by fatigue of the driver after long-term driving in the prior art, and the method can meet the personalized demand of the driver on the road feel, and provide better driving experience and safety guarantee for the driver.
In order to achieve the above purpose, the invention adopts the following technical scheme:
The invention relates to a steer-by-wire system considering driver force decay, which comprises a steering wheel, a steering column, a torque sensor, a wireless surface myoelectric sensor, a road feel motor reducer and a road feel controller, wherein the steering column is provided with a steering wheel;
The steering wheel is connected with one end of the steering column, the other end of the steering column is connected with the output end of the road sensing motor reducer, the input end of the road sensing motor reducer is connected with the road sensing motor, the torque sensor is arranged on the steering column, the wireless surface myoelectric sensor is fixed on target muscles which need to be detected by a driver, and the road sensing controller receives the torque sensor signals and the wireless surface myoelectric sensor signals and controls the road sensing motor to output road sensing moment.
Further, the torque sensor is selected from MEAS FCA7300 for measuring steering wheel torque signals.
Further, delsys Trigno WIRELESS EMG is selected as the wireless surface electromyographic sensor for detecting the surface electromyographic signal EMG.
Further, the road feel controller is used for processing the surface electromyographic signals, calculating ideal road feel moment and controlling the current of the road feel motor.
The invention relates to a road feel control method of a steer-by-wire system considering driver force decay, which is based on the steer-by-wire system and comprises the following steps:
(1) Collecting a steering wheel torque signal, a vehicle speed signal, a steering execution motor corner torque signal and a driver surface electromyographic signal of a vehicle, processing the obtained driver surface electromyographic signal, and calculating the muscle activation of the driver and the steering discomfort of the driver;
(2) Establishing an ideal road feel function model considering the driver force degradation, and calculating an ideal road feel moment considering the driver force degradation according to the vehicle speed signal, the steering execution motor corner torque signal and the force degradation acquired in the step (1);
(3) And (3) calculating corresponding current according to the ideal road feel moment calculated in the step (2), and controlling the output torque of the road feel motor to track the ideal road feel moment in real time so as to realize that the actual steering discomfort degree of a driver tracks the ideal steering discomfort degree.
Further, the specific steps of the step (1) are as follows:
(11) Selecting a muscle group which plays a role in the steering process of the vehicle of a driver as a target muscle group for surface electromyographic signal detection, wherein the muscle group plays a role in the steering process of the vehicle and comprises a pectoral major collarbone part, a deltoid toe, a triceps brachii long head and a great circle muscle;
(12) Carrying out 25 Hz-250 Hz band-pass filtering and full-wave rectification on the detected surface electromyographic signals, and filtering interference noise in the detection process;
the root mean square amplitude RMS of the surface electromyographic signals of the target muscles of the driver obtained after the filtering is calculated as follows:
the surface electromyographic signal value of the target muscle group of the driver under the maximum autonomous contractile force under the calibration action is processed, and the root mean square amplitude RMS MVC is calculated as follows:
Wherein EMG (T) is the surface electromyographic signal value of the muscle of the target part, and T is the sampling period;
3Hz low-pass filtering is carried out on the root mean square amplitude RMS to obtain smooth RMS data;
The muscle activation a was calculated as follows:
(13) According to the muscle activation A obtained by real-time calculation, the steering discomfort degree of the measured muscle in a one-time complete steering operation process is established as follows:
Wherein D muscle is the steering discomfort degree of the muscle, and t is the time of one complete steering operation process;
according to the contribution of target muscles to steering discomfort, the steering discomfort of each muscle is weighted and polymerized to obtain the overall steering discomfort of the upper limbs of the driver, and the steering discomfort is used for observing the decline degree of the strength of the upper limbs of the driver in the steering process:
wherein D is the steering discomfort of the driver, ω j is the weight coefficient of the j-th measured muscle, j=1, 2,..;
the steering discomfort degree of the driver under the equal weight is obtained, the steering discomfort degree of each muscle is regressed under the equal weight, the correlation coefficient a j of the muscle is calculated, the correlation coefficient of each muscle is normalized, and the weight coefficient of each muscle is calculated by the normalization:
Wherein a n is the correlation coefficient of the nth muscle.
Further, the specific steps of the step (2) are as follows:
(21) The dynamic analysis is carried out on the gear rack, the steering executing motor and the speed reducing mechanism, and the dynamic model of the steering executing mechanism is as follows:
Wherein θ f is the steering angle of the steering actuator, J f is the rotational inertia of the steering actuator, B f is the system damping coefficient, K f is the torsional rigidity of the steering actuator, f f is the system friction torque, G f is the reduction ratio of the speed reducing mechanism of the steering actuator, T fm is the output torque of the steering actuator, and T f is the steering resistance torque;
(22) The ideal steering power-assisted function model is established as follows:
K(u)=C2eau+b (9)
wherein T p is steering assistance torque, T w is ideal road feel torque, T w0 is steering wheel torque when the assistance torque is minimum, T pmax is maximum steering assistance torque, K (D d) and K (u) are gradient functions of assistance characteristic curves, D d is driver force degradation degree and is calculated by a road feel controller according to steering discomfort degree of a driver, u is vehicle speed, C 1 and C 2 are characteristic factors of the driver, and the adjustment of assistance characteristics according to the requirements of the driver is realized;
taking a power-assisted gradient function value when the driver force degradation degree is 0 as a reference value, and establishing a driver force degradation gradient function model as follows:
wherein C 3 is a driver characteristic factor;
(23) Establishing an ideal road feel function model considering the driver force declination degree according to the models in the step (21) and the step (22);
the relation among the ideal road sensing moment, the steering resistance moment and the steering auxiliary moment is as follows:
Tw＝Tf-TP (11)
calculating to obtain ideal road feel moment considering the driver force declination degree:
further, the specific steps of the step (3) are as follows:
(31) The ideal steering discomfort degree is determined by the steering discomfort degree of a driver in the process of driving for many times, the steering discomfort degree of a complete steering operation is finished for the first time, and the road feel controller records the last k times of the history of the steering discomfort degree and takes the average value as follows:
Where D i is the ideal steering discomfort, and D j is the steering discomfort of the j-th first complete steering operation;
Adjusting the driver characteristic factor in the step (22) to obtain the most suitable road feel moment strength;
Calculating an error e D (t) by subtracting the ideal steering discomfort level D i from the real-time steering discomfort level D of the driver in the step (1):
eD(t)＝Di-D (14)
The ideal road-sensing torque T w of the driver obtained in the step (2) is differenced from the road-sensing motor output torque T wa (i.e., steering wheel torque), and an error e T (T) is calculated:
eT(t)＝Tw-Twa (15)
The road feel controller adopts a PID control method to control the steering discomfort degree of a driver to track the ideal steering discomfort degree, controls the road feel motor to output torque to track target torque, takes errors e D (t) and e T (t) as the input of the road feel controller, and outputs the model as follows:
Wherein u i (t) is the output control quantity of the road-sensing controller, K pi is a proportionality coefficient, K ii is an integral constant, K di is a differential constant, the output control quantity u D (t) is a force declination degree D d, and the output control quantity u T (t) is the target current of the input road-sensing motor;
(32) The force degradation degree D d output by the road feel controller participates in calculation of ideal road feel moment, so that the steering force required by a driver is reduced along with the force degradation caused by fatigue, the steering burden of the driver is lightened, the target current of the road feel motor output by the road feel controller enables the torque output by the road feel motor to track the ideal road feel moment, and the tracking of the actual steering discomfort of the driver to the ideal steering discomfort is realized.
The invention has the beneficial effects that:
The invention increases the detection of the surface electromyographic signals of the driver on the basis of the traditional steer-by-wire system, provides highly personalized road feel moment adjustment for the drivers with different muscle states and driving styles according to the steering uncomfortableness of the driver by combining the electromyographic signals and the road feel moment adjustment mechanism, brings the drivers with driving experience according with the preference and the requirements of the drivers, can adaptively adjust the road feel moment according to the fading condition of the muscles of the drivers, lightens the muscle burden of the drivers in the long-time driving process, is beneficial to reducing the fatigue level of the drivers, improves the driving comfort and the driving safety, and can provide warning or take measures to maintain the safety and prevent accidents caused by fatigue driving if abnormal muscle reactions or excessive fatigue of the drivers are detected.
Drawings
Fig. 1 is a schematic diagram of a steer-by-wire system of the present invention.
Fig. 2 is a schematic diagram of the control method of the present invention.
Detailed Description
The invention will be further described with reference to examples and drawings, to which reference is made, but which are not intended to limit the scope of the invention.
Referring to fig. 1, a steer-by-wire system considering driver force degradation of the present invention includes a steering wheel 1, a steering column 2, a torque sensor 3, a wireless surface myoelectric sensor 4, a road-sensing motor 5, a road-sensing motor reducer 6, and a road-sensing controller 7;
The steering wheel 1 is connected with one end of the steering column 2, the other end of the steering column 2 is connected with the output end of the road sensing motor reducer 6, the input end of the road sensing motor reducer 6 is connected with the road sensing motor 5, the torque sensor 3 is arranged on the steering column 2, the wireless surface myoelectric sensor 4 is fixed on target muscles which need to be detected by a driver, and the road sensing controller 7 receives the torque sensor signals and the wireless surface myoelectric sensor signals and controls the road sensing motor 5 to output road sensing torque.
In the example, the torque sensor 3 is a MEAS FCA7300 for measuring steering wheel torque signals.
In an example, delsys Trigno WIRELESS EMG is selected as the wireless surface electromyographic sensor 4, and is used for detecting the surface electromyographic signal EMG.
The road sensing controller 7 is used for processing surface electromyographic signals, calculating ideal road sensing moment and controlling current of the road sensing motor.
Referring to fig. 2, the road feel control method of the steer-by-wire system considering the driver force degradation of the present invention is based on the steer-by-wire system, and comprises the following steps:
(1) Collecting a steering wheel torque signal, a vehicle speed signal, a steering execution motor corner torque signal and a driver surface electromyographic signal of a vehicle, processing the obtained driver surface electromyographic signal, and calculating the muscle activation of the driver and the steering discomfort of the driver; the method comprises the following specific steps:
(11) Selecting a muscle group which plays a role in the steering process of the vehicle of a driver as a target muscle group for surface electromyographic signal detection, wherein the muscle group plays a role in the steering process of the vehicle and comprises a pectoral major collarbone part, a deltoid toe, a triceps brachii long head and a great circle muscle;
(12) Carrying out 25 Hz-250 Hz band-pass filtering and full-wave rectification on the detected surface electromyographic signals, and filtering interference noise in the detection process;
the root mean square amplitude RMS of the surface electromyographic signals of the target muscles of the driver obtained after the filtering is calculated as follows:
the surface electromyographic signal value of the target muscle group of the driver under the maximum autonomous contractile force under the calibration action is processed, and the root mean square amplitude RMS MVC is calculated as follows:
Wherein EMG (T) is the surface electromyographic signal value of the muscle of the target part, and T is the sampling period;
3Hz low-pass filtering is carried out on the root mean square amplitude RMS to obtain smooth RMS data;
The muscle activation a was calculated as follows:
(13) According to the muscle activation A obtained by real-time calculation, the steering discomfort degree of the measured muscle in a one-time complete steering operation process is established as follows:
Wherein D muscle is the steering discomfort degree of the muscle, and t is the time of one complete steering operation process;
according to the contribution of target muscles to steering discomfort, the steering discomfort of each muscle is weighted and polymerized to obtain the overall steering discomfort of the upper limbs of the driver, and the steering discomfort is used for observing the decline degree of the strength of the upper limbs of the driver in the steering process:
wherein D is the steering discomfort of the driver, ω j is the weight coefficient of the j-th measured muscle, j=1, 2,..;
the steering discomfort degree of the driver under the equal weight is obtained, the steering discomfort degree of each muscle is regressed under the equal weight, the correlation coefficient a j of the muscle is calculated, the correlation coefficient of each muscle is normalized, and the weight coefficient of each muscle is calculated by the normalization:
Wherein a n is the correlation coefficient of the nth muscle.
(2) An ideal road feel function model considering the driver force degradation degree is established, and the ideal road feel moment considering the driver force degradation degree is calculated according to the vehicle speed signal, the steering execution motor corner torque signal and the force degradation degree acquired in the step (1), wherein the specific steps are as follows:
(21) The dynamic analysis is carried out on the gear rack, the steering executing motor and the speed reducing mechanism, and the dynamic model of the steering executing mechanism is as follows:
Wherein θ f is the steering angle of the steering actuator, J f is the rotational inertia of the steering actuator, B f is the system damping coefficient, K f is the torsional rigidity of the steering actuator, f f is the system friction torque, G f is the reduction ratio of the speed reducing mechanism of the steering actuator, T fm is the output torque of the steering actuator, and T f is the steering resistance torque;
(22) The ideal steering power-assisted function model is established as follows:
K(u)=C2eau+b (9)
wherein T p is steering assistance torque, T w is ideal road feel torque, T w0 is steering wheel torque when the assistance torque is minimum, T pmax is maximum steering assistance torque, K (D d) and K (u) are gradient functions of assistance characteristic curves, D d is driver force degradation degree and is calculated by a road feel controller according to steering discomfort degree of a driver, u is vehicle speed, C 1 and C 2 are characteristic factors of the driver, and the adjustment of assistance characteristics according to the requirements of the driver is realized;
taking a power-assisted gradient function value when the driver force degradation degree is 0 as a reference value, and establishing a driver force degradation gradient function model as follows:
wherein C 3 is a driver characteristic factor;
(23) Establishing an ideal road feel function model considering the driver force declination degree according to the models in the step (21) and the step (22);
the relation among the ideal road sensing moment, the steering resistance moment and the steering auxiliary moment is as follows:
Tw＝Tf-TP (11)
calculating to obtain ideal road feel moment considering the driver force declination degree:
(3) According to the ideal road sensing moment calculated in the step (2), calculating corresponding current, and controlling the output torque of the road sensing motor to track the ideal road sensing moment in real time so as to realize that the actual steering discomfort degree of a driver tracks the ideal steering discomfort degree, wherein the specific steps are as follows:
(31) The ideal steering discomfort degree is determined by the steering discomfort degree of a driver in the process of driving for many times, the steering discomfort degree of a complete steering operation is finished for the first time, and the road feel controller records the last k times of the history of the steering discomfort degree and takes the average value as follows:
Where D i is the ideal steering discomfort, and D j is the steering discomfort of the j-th first complete steering operation;
Adjusting the driver characteristic factor in the step (22) to obtain the most suitable road feel moment strength;
Calculating an error e D (t) by subtracting the ideal steering discomfort level D i from the real-time steering discomfort level D of the driver in the step (1):
eD(t)＝Di-D (14)
The ideal road-sensing torque T w of the driver obtained in the step (2) is differenced from the road-sensing motor output torque T wa (i.e., steering wheel torque), and an error e T (T) is calculated:
eT(t)＝Tw-Twa (15)
The road feel controller adopts a PID control method to control the steering discomfort degree of a driver to track the ideal steering discomfort degree, controls the road feel motor to output torque to track target torque, takes errors e D (t) and e T (t) as the input of the road feel controller, and outputs the model as follows:
Wherein u i (t) is the output control quantity of the road-sensing controller, K pi is a proportionality coefficient, K ii is an integral constant, K di is a differential constant, the output control quantity u D (t) is a force declination degree D d, and the output control quantity u T (t) is the target current of the input road-sensing motor;
(32) The force degradation degree D d output by the road feel controller participates in calculation of ideal road feel moment, so that the steering force required by a driver is reduced along with the force degradation caused by fatigue, the steering burden of the driver is lightened, the target current of the road feel motor output by the road feel controller enables the torque output by the road feel motor to track the ideal road feel moment, and the tracking of the actual steering discomfort of the driver to the ideal steering discomfort is realized.
The present invention has been described in terms of the preferred embodiments thereof, and it should be understood by those skilled in the art that various modifications can be made without departing from the principles of the invention, and such modifications should also be considered as being within the scope of the invention.

Claims (4)

1. A road sensing control method of a drive-by-wire steering system considering driver force degradation is based on the drive-by-wire steering system considering driver force degradation, and the system comprises a steering wheel, a steering column, a torque sensor, a wireless surface myoelectric sensor, a road sensing motor reducer and a road sensing controller;
the steering wheel is connected with one end of the steering column, the other end of the steering column is connected with the output end of the road sensing motor reducer, and the input end of the road sensing motor reducer is connected with the road sensing motor;
The method is characterized by comprising the following steps:
(1) Collecting a steering wheel torque signal, a vehicle speed signal, a steering execution motor corner torque signal and a driver surface electromyographic signal of a vehicle, processing the obtained driver surface electromyographic signal, and calculating the muscle activation of the driver and the steering discomfort of the driver;
(2) Establishing an ideal road feel function model considering the driver force degradation, and calculating an ideal road feel moment considering the driver force degradation according to the vehicle speed signal, the steering execution motor corner torque signal and the force degradation acquired in the step (1);
(3) And (3) calculating corresponding current according to the ideal road feel moment calculated in the step (2), and controlling the output torque of the road feel motor to track the ideal road feel moment in real time so as to realize that the actual steering discomfort degree of a driver tracks the ideal steering discomfort degree.
2. The road feel control method of a steer-by-wire system taking into account driver force degradation according to claim 1, wherein the step (1) comprises the specific steps of:
(11) Selecting a muscle group which plays a role in the steering process of the vehicle of a driver as a target muscle group for surface electromyographic signal detection, wherein the muscle group plays a role in the steering process of the vehicle and comprises a pectoral major collarbone part, a deltoid toe, a triceps brachii long head and a great circle muscle;
(12) Carrying out 25 Hz-250 Hz band-pass filtering and full-wave rectification on the detected surface electromyographic signals, and filtering interference noise in the detection process;
the root mean square amplitude RMS of the surface electromyographic signals of the target muscles of the driver obtained after the filtering is calculated as follows:
the surface electromyographic signal value of the target muscle group of the driver under the maximum autonomous contractile force under the calibration action is processed, and the root mean square amplitude RMS MVC is calculated as follows:
Wherein EMG (T) is the surface electromyographic signal value of the muscle of the target part, and T is the sampling period;
3Hz low-pass filtering is carried out on the root mean square amplitude RMS to obtain smooth RMS data;
The muscle activation a was calculated as follows:
(13) According to the muscle activation A obtained by real-time calculation, the steering discomfort degree of the measured muscle in a one-time complete steering operation process is established as follows:
Wherein D muscle is the steering discomfort degree of the muscle, and t is the time of one complete steering operation process;
according to the contribution of target muscles to steering discomfort, the steering discomfort of each muscle is weighted and polymerized to obtain the overall steering discomfort of the upper limbs of the driver, and the steering discomfort is used for observing the decline degree of the strength of the upper limbs of the driver in the steering process:
Wherein D is steering discomfort of a driver, omega j is a weight coefficient of the j-th measured muscle, and j=1, 2, L, n and n are the total number of the measured muscles;
the steering discomfort degree of the driver under the equal weight is obtained, the steering discomfort degree of each muscle is regressed under the equal weight, the correlation coefficient a j of the muscle is calculated, the correlation coefficient of each muscle is normalized, and the weight coefficient of each muscle is calculated by the normalization:
Wherein a n is the correlation coefficient of the nth muscle.
3. The road feel control method of the steer-by-wire system taking into consideration driver's force degradation according to claim 2, wherein the step (2) comprises the specific steps of:
(21) The dynamic analysis is carried out on the gear rack, the steering executing motor and the speed reducing mechanism, and the dynamic model of the steering executing mechanism is as follows:
Wherein θ f is the steering angle of the steering actuator, J f is the rotational inertia of the steering actuator, B f is the system damping coefficient, K f is the torsional rigidity of the steering actuator, f f is the system friction torque, G f is the reduction ratio of the speed reducing mechanism of the steering actuator, T fm is the output torque of the steering actuator, and T f is the steering resistance torque;
(22) The ideal steering power-assisted function model is established as follows:
K(u)=C2eau+b(9)
wherein T p is steering assistance torque, T w is ideal road feel torque, T w0 is steering wheel torque when the assistance torque is minimum, T pmax is maximum steering assistance torque, K (D d) and K (u) are gradient functions of assistance characteristic curves, D d is driver force degradation degree and is calculated by a road feel controller according to steering discomfort degree of a driver, u is vehicle speed, C 1 and C 2 are characteristic factors of the driver, and the adjustment of assistance characteristics according to the requirements of the driver is realized;
taking a power-assisted gradient function value when the driver force degradation degree is 0 as a reference value, and establishing a driver force degradation gradient function model as follows:
wherein C 3 is a driver characteristic factor;
(23) Establishing an ideal road feel function model considering the driver force declination degree according to the models in the step (21) and the step (22);
the relation among the ideal road sensing moment, the steering resistance moment and the steering auxiliary moment is as follows:
Tw＝Tf-TP(11)
calculating to obtain ideal road feel moment considering the driver force declination degree:
4. the road feel control method of a steer-by-wire system taking into account driver's force degradation according to claim 3, wherein said step (3) comprises the specific steps of:
(31) The ideal steering discomfort degree is determined by the steering discomfort degree of a driver in the process of driving for many times, the steering discomfort degree of a complete steering operation is finished for the first time, and the road feel controller records the last k times of the history of the steering discomfort degree and takes the average value as follows:
Where D i is the ideal steering discomfort, and D j is the steering discomfort of the j-th first complete steering operation;
Adjusting the driver characteristic factor in the step (22) to obtain the most suitable road feel moment strength;
Calculating an error e D (t) by subtracting the ideal steering discomfort level D i from the real-time steering discomfort level D of the driver in the step (1):
eD(t)＝Di-D(14)
And (2) calculating an error e T (T) by making a difference between the ideal road-sensing torque T w of the driver obtained in the step (2) and the road-sensing motor output torque T wa:
eT(t)＝Tw-Twa(15)
The road feel controller adopts a PID control method to control the steering discomfort degree of a driver to track the ideal steering discomfort degree, controls the road feel motor to output torque to track target torque, takes errors e D (t) and e T (t) as the input of the road feel controller, and outputs the model as follows:
Wherein u i (t) is the output control quantity of the road-sensing controller, K pi is a proportionality coefficient, K ii is an integral constant, K di is a differential constant, the output control quantity u D (t) is a force declination degree D d, and the output control quantity u T (t) is the target current of the input road-sensing motor;
(32) The force degradation degree D d output by the road feel controller participates in calculation of ideal road feel moment, so that steering force required by a driver is reduced along with the force degradation caused by fatigue, and the target current of the road feel motor output by the road feel controller enables the torque output by the road feel motor to track the ideal road feel moment, so that the tracking of the actual steering discomfort of the driver to the ideal steering discomfort is realized.
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CN110281938A (en) * 2019-05-30 2019-09-27 南京航空航天大学 A kind of automobile line traffic control intelligent steering system and its control method merging fatigue detecting
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