CN103057585B - Control device and control method for variable transmission ratio of active steering system - Google Patents

Abstract

The invention discloses a control device and a control method for variable transmission ratios of an active steering system, and belongs to the technical field of the invention. The control device includes: a conventional transmission ratio control module, a PID controller, a corner motor, a current detector, a first accumulator, a second accumulator, a first transmission ratio correction module, a second transmission ratio correction module, and a switch selector , Yaw rate state observer. The control method selects different additional angle compensation schemes for the angle motor according to the wheel speed signal, the steering wheel angle signal, and the steering wheel angle acceleration signal. The present invention considers the influence of the steering wheel speed signal, the steering wheel angle signal, and the steering wheel angle acceleration signal on the active steering system, When the vehicle is in different operational stability, different compensation schemes are selected for outputting the additional rotation angle of the rotation angle motor, which improves the control accuracy.

Description

Control device and control method for variable transmission ratio of active steering system

technical field

The invention discloses a control device and a control method for variable transmission ratio of an active steering system, belonging to the technical field of steering system control.

Background technique

As an extremely promising active steering system, it ensures the lightness of the steering while giving the driver a satisfactory steering feel. At present, most electric power steering systems at home and abroad use a fixed transmission ratio, and a huge modification has been made to the hydraulic power steering, which avoids the fact that the steering power provided by the traditional hydraulic power steering system cannot be changed with the increase of vehicle speed. Shortcomings. In this way, the vehicle has good steering portability at low speeds, and at high speeds, the driver obtains a significant "road feel", which reduces the vehicle stability and the driver's sense of safety when driving at high speeds. However, many complicated situations will appear in the driving process of the car, and the driving conditions of the car are also complex and changeable. A fixed transmission ratio is not conducive to changing the performance of the steering system: at low speeds, the steering wheel tends to sink; at high speeds, dangerous conditions such as oversteer tend to occur, and there are hidden dangers in the handling stability of the car.

In recent years, there has been an upsurge of research on electric power steering systems with variable transmission ratio functions at home and abroad, which has made great progress compared with fixed transmission ratios. However, the transmission ratio control only adjusts the transmission ratio of the car through the vehicle speed signal, and completely ignores the influence of the steering wheel speed and the steering wheel angular acceleration on the steering stability of the steering system. The speed of the vehicle and the angle of the steering wheel determine the transmission ratio, without considering how to correct the transmission ratio once the stability of the car is abnormal. When the handling stability of the car is different, the factors that need to be considered in the control of the transmission ratio of the car are very different. Therefore, different transmission ratio correction schemes must be proposed according to the different handling and stability conditions of the vehicle to reduce some potential safety hazards caused by these defects.

Due to the complex driving conditions of the vehicle, the measurement accuracy of its on-board sensors, production costs and other factors, many vehicle state variables cannot be accurately and reliably obtained through sensors; at the same time, the existing on-board sensors also have calibration errors and drifts. These problems limit the further development of variable transmission ratio control of automotive active steering systems. However, as an important indicator of vehicle handling stability, vehicle yaw rate plays a vital role in the evaluation of vehicle handling stability and the control of vehicle transmission ratio. Therefore, it is absolutely necessary to use a new control method to estimate the yaw rate of the vehicle, reduce the use of on-board sensors, and improve the reliability of the yaw rate signal.

Contents of the invention

The technical problem to be solved by the present invention is to provide a control device and a control method for variable transmission ratios of an active steering system in view of the shortcomings of the above-mentioned background technology.

The present invention adopts following technical scheme for realizing above-mentioned purpose of the invention:

Control device for variable transmission ratio of active steering system, including conventional transmission ratio control module, PID controller, angle motor, current detector, first accumulator, second accumulator, first transmission ratio correction module, second transmission ratio correction Module, switch selector, yaw rate state observer; where:

The first input terminal of the conventional transmission ratio control module is connected to the vehicle speed sensor, the second input terminal is connected to the steering wheel angle sensor, and the output terminal is connected to the first input terminal of the first accumulator;

The first input terminal of the yaw rate state observer is connected to the vehicle speed sensor, and the second input terminal is connected to the front wheel angle sensor;

The first input terminal of the switch selector is connected to the roll angle sensor, and the second input terminal is connected to the output terminal of the yaw rate state observer;

The control terminal of the first transmission ratio correction module is connected to the output terminal of the switch selector, the first input terminal is connected to the steering wheel speed sensor, the second input terminal is connected to the steering wheel angular acceleration sensor, and the output terminal is connected to the second accumulator of the first accumulator. input terminal;

The control terminal of the second transmission ratio correction module is connected to the output terminal of the switch selector, the first input terminal is connected to the roll angle sensor, the second input terminal is connected to the output terminal of the yaw rate state observer, and the output terminal is connected to the first an accumulator second input terminal;

The input terminal of the current detector is connected to the output terminal of the angle motor, and the output terminal is connected to the third input terminal of the first accumulator;

The input terminal of the PID controller is connected to the output terminal of the first accumulator, and the output terminal is connected to the input terminal of the corner motor;

The first input end of the second accumulator is connected to the output end of the angle motor, the second input end is connected to the output end of the gear transmission mechanism, and the output end is connected to the input end of the rack and pinion steering gear.

The control device for variable transmission ratio of the active steering system also includes a vehicle speed signal filter and a front wheel angle signal filter;

Wherein: the input terminal of the vehicle speed signal filter is connected to the vehicle speed sensor, and the output terminal is connected to the first input terminal of the yaw rate state observer; the input terminal of the front wheel angle signal filter is connected to the front wheel angle sensor, and the output terminal is connected to The second input terminal of the yaw rate state observer.

A method for controlling a variable transmission ratio of an active steering system includes the following steps:

Step 1, constructing the variable transmission ratio control device of the active steering system;

Step 2, the driver applies a corner torque to the steering wheel of the active steering system;

Step 3, the conventional transmission ratio module obtains an ideal corner motor output current signal according to the vehicle speed signal measured by the vehicle speed sensor and the steering wheel angle signal measured by the steering wheel angle sensor;

Step 4, the yaw rate state observer obtains the yaw rate signal according to the output signal of the vehicle speed sensor and the output signal of the front wheel angle sensor;

Step 5, the switch selector judges the vehicle handling stability according to the output signal of the roll angle sensor and the yaw rate signal, and triggers the operation of the transmission ratio correction module to obtain the compensation current signal. The specific method is as follows:

If the operation stability of the vehicle is abnormal: the switch selector triggers the first transmission ratio correction module to obtain the first compensation current signal;

If the vehicle operation stability is normal: the switch selector triggers the second transmission ratio correction module to obtain the second compensation current signal;

Step 6, the first accumulator uses the ideal corner motor output current signal described in step 3 as the first variable, the compensation current signal described in step 5 as the second variable, and the actual output current of the corner motor measured by the current detector The signal is the third variable, and the input quantity of the PID controller is obtained;

Step 7, the PID controller processes the output of the first accumulator to obtain the input signal of the angle motor, and the angle motor outputs an additional angle signal;

Step 8, the second accumulator takes the additional rotation angle signal described in step 7 as the first variable, and takes the output of the gear transmission mechanism as the second variable to obtain the input signal of the rack and pinion steering gear, and the wheels are driven by the rack and pinion gear sports.

The present invention adopts the above-mentioned technical scheme, and has the following beneficial effects: the present invention not only considers the influence of the vehicle speed on the active steering system, but also considers the influence of the steering wheel speed signal, the steering wheel angle signal, and the steering wheel angle acceleration signal on the active steering system. When the operation stability is different, different compensation schemes are selected for the additional rotation angle output by the rotation angle motor, which improves the control accuracy. The operation of eliminating interference on the vehicle speed signal and the front wheel angle signal further improves the control accuracy.

Description of drawings

Fig. 1 is a schematic diagram of an active steering body variable transmission ratio control device.

Figure 2 is a simulation block diagram of the yaw rate state observer.

Figure 3 is a simulation block diagram of the switch selector.

Fig. 4 is a graph of the measured value of the yaw rate sensor and the estimated value of the state observer under the external disturbance.

Explanation of the symbols in the figure: 1 is the driver model, 2 is the steering wheel model, 3 is the rotation angle sensor, 4 is the double-row planetary gear train, 5 is the rack and pinion steering gear, 6 is the conventional transmission ratio control module, 7 is the current detector , 8 is the PID controller, 9 is the corner motor, 10 is the wheel, 11 is the first transmission ratio correction module, 12 is the switch selector, 13 is the second transmission ratio correction module, 14 is the yaw rate state observer, 16 17 is the steering wheel angle information, 18 is the new signal of the steering wheel angle, 19 is the output of the double-row planetary gear train, 20 is the input signal of the rack and pinion steering gear, 21 is the vehicle speed signal, 22 is the output current signal of the corner motor, 23 is the input value of the PID controller, 24 is the input signal of the angle motor, 25 is the additional angle signal, 26 is the actual output current signal of the angle motor, 27 is the front wheel angle signal, 28 is the steering wheel speed signal, and 29 is the steering wheel angle acceleration signal. 30 is the first compensation work signal, 31 is the second compensation work signal, 32 is the roll angle signal, 33 is the compensation current signal, 34 is the yaw rate signal, 35 is the vehicle speed sensor, 36 is the vehicle speed sensor interference simulator, 37 38 is the simulated interference signal of the front wheel angle, 39 is the simulated interference signal of the vehicle speed, 40 is the interference eliminator of the front wheel angle signal, 41 is the interference eliminator of the vehicle speed signal, and 42 is the vehicle two degrees of freedom Model, 43 is the front wheel angle signal without interference, 44 is the vehicle speed signal without interference, 45 is the lateral acceleration signal, 47 is the roll angle sensor interference simulator, 48 is the roll angle sensor, 49 is the roll angle signal interference eliminator, 50 is a roll angle simulation interference signal, and 51 is a roll angle signal without interference.

detailed description

Below in conjunction with accompanying drawing, the technical scheme of invention is described in detail:

The active steering system includes: steering wheel, angle sensor, dual planetary gear train, rack and pinion steering, wheel and vehicle speed sensors. The active steering system in the present invention adds a roll angle sensor, a front wheel angle sensor, a steering wheel angle acceleration sensor, a steering wheel speed sensor, and a steering wheel angle sensor.

Vehicle speed sensor: used to detect the vehicle speed of the car, usually installed in the drive axle housing.

Steering wheel angle sensor: used to detect the steering wheel angle, usually installed on the steering wheel steering tube shaft.

Steering wheel speed sensor: used to detect the steering wheel speed, usually installed on the steering wheel steering tube shaft.

Steering wheel angular acceleration sensor: used to detect the steering wheel angular acceleration, usually installed on the steering wheel steering tube shaft.

Roll angle sensor: used to detect the degree of roll of the car, usually installed on the car compartment.

Front wheel angle sensor: used to detect the angle of the front wheel, usually installed in the front wheel steering gear.

The existing active steering system variable transmission ratio control device includes a conventional transmission ratio module, a PID controller, a corner motor, a current detector, a first accumulator, and a second accumulator. The conventional transmission ratio module only obtains the ideal output current signal of the corner motor according to the vehicle speed signal measured by the vehicle speed sensor. The first accumulator accumulates the ideal output current signal of the angle motor and the actual output current signal of the angle motor to obtain the input value of the PID controller, ignoring the influence of the steering wheel speed signal and the steering wheel angle acceleration signal on the operational stability of the active steering system.

The active steering system and variable transmission ratio control device shown in Figure 1 are constructed using simulation software. The active steering system includes: a driver model 1 , a steering wheel model 2 , a rotation angle sensor 3 , a double planetary gear train 4 , a rack and pinion steering gear 5 , and wheels 10 . The active steering system variable transmission ratio control device includes: a conventional transmission ratio control module 6, a first accumulator, a PID controller 8, a corner motor 9, a current detector 7, a second accumulator, a yaw rate state observer 14, and a switch A selector 12 , a first transmission ratio correction module 11 , and a second transmission ratio correction module 13 . The first input terminal of the conventional transmission ratio control module 6 is connected to the vehicle speed sensor, the second input terminal is connected to the steering wheel angle sensor, and the output terminal is connected to the first input terminal of the first accumulator. The first input terminal of the yaw rate state observer 14 is connected to the vehicle speed sensor, and the second input terminal is connected to the front wheel angle sensor. The first input terminal of the switch selector 12 is connected to the roll angle sensor, and the second input terminal is connected to the output terminal of the yaw rate state observer 14 . The control terminal of the first transmission ratio correction module 11 is connected to the output terminal of the switch selector 12, the first input terminal is connected to the steering wheel speed sensor, the second input terminal is connected to the steering wheel angular acceleration sensor, and the output terminal is connected to the second input terminal of the first accumulator. The control terminal of the second transmission ratio correction module 13 is connected to the output terminal of the switch selector 12, the first input terminal is connected to the roll angle sensor, the second input terminal is connected to the output terminal of the yaw rate state observer 14, and the output terminal is connected to the first accumulator second input. The input end of the current detector 7 is connected to the output end of the angle motor 9, and the output end is connected to the third input end of the first accumulator. The input end of the PID controller 8 is connected to the output end of the first accumulator, and the output end is connected to the input end of the corner motor 9 . The first input end of the second accumulator is connected to the output end of the angle motor 9, the second input end is connected to the output end of the double-row planetary gear train 4, and the output end is connected to the input end of the rack and pinion steering gear 5. The wheel 10 is connected to the output end of the rack and pinion steering gear 5 .

The working principle of the active steering system variable transmission ratio control device of the present invention is as follows: the driver applies steering torque to the steering wheel, and the steering wheel transmits the angular displacement of the steering wheel to the rack and pinion through the steering column and the double-row planetary gear train through the gear transmission mechanism The steering gear, the rack and pinion steering gear drives the wheels through a certain angle. At the same time, the active steering system judges the driving conditions of the car, and the rotation of the corner motor drives the double-row planetary gear train to rotate at a certain angle. When the active steering system requires a relatively large transmission, the motor rotates in the opposite direction to the steering wheel; when the active steering system requires a small transmission, the motor rotates in the same direction as the steering wheel. An additional rotation angle is applied to the wheels through the double-row planetary gear train, and the function of variable transmission ratio of the active steering system is realized.

A method for controlling a variable transmission ratio of an active steering system includes the following steps:

Step 1, construct the active steering system variable transmission ratio control device as shown in Figure 1;

Step 2, the driver model 1 applies a corner torque 16 to the steering wheel model 2 of the active steering system;

Step 3, the conventional transmission ratio module 6 according to the vehicle speed signal 21 (υ) measured by the vehicle speed sensor, the steering wheel angle signal 18 (θ) measured by the steering wheel angle sensor 3 from the steering wheel angle information 17, through the preset transmission ratio characteristic The curved surface is k (υ, θ) to obtain the ideal corner motor output current signal 22;

Step 4, the yaw rate state observer 14 obtains the yaw rate signal 34 according to the vehicle speed signal 21 and the front wheel angle signal 27;

Step 5, the switch selector 12 judges the steering stability of the vehicle according to the roll angle signal 32 and the yaw rate signal No. 34, triggers the transmission ratio correction module to work to obtain the compensation current signal, and the specific method is as follows:

If the vehicle operation stability is abnormal: the switch selector outputs the first compensation work signal 30 to trigger the first transmission ratio correction module, and the first transmission ratio correction module is based on the steering wheel rotational speed signal 28 (ω), the steering wheel angular acceleration signal 29 (α) , The preset transmission ratio characteristic surface, namely k(ω,α), obtains the first compensation current signal;

If the vehicle operation stability is normal: the switch selector outputs the second compensation working signal 31 to trigger the second transmission ratio correction module, and the second transmission ratio correction module is based on the roll angle signal 32 (β) and the yaw rate 34 (δ), The second compensation current signal is obtained from the preset transmission ratio characteristic surface, namely k(β, δ);

Step 6, the first accumulator takes the ideal corner motor output current signal 22 described in step 3 as the first variable, the compensation current signal 33 described in step 5 as the second variable, and the corner motor measured by the current detector 7 The actual output current signal 26 is the third variable, and the input quantity 23 of the PID controller is obtained;

Step 7, the PID controller 8 processes the output of the first accumulator to obtain the input signal 24 of the angle motor, and the angle motor 9 outputs an additional angle signal 25;

Step 8, the second accumulator takes the additional rotation angle signal 25 described in step 7 as the first variable, and takes the output of the double planetary gear train 19 as the second variable to obtain the input signal 20 of the rack and pinion steering gear, and the wheel 10 is in the gear Driven by the rack rotator 5, it moves.

The simulation block diagram of the yaw rate state observer is shown in Figure 2. The vehicle speed sensor 35 outputs the vehicle speed signal 21 and the vehicle speed sensor interference simulator 36 sends out the vehicle speed simulation interference signal 39 as the input of the vehicle speed signal interference eliminator 41 to obtain a vehicle speed signal 44 without interference. The front wheel angle signal 27 output by the front wheel angle sensor 34 and the front wheel angle sensor interference simulator 37 send the front wheel angle analog interference signal 38 as the input of the front wheel angle signal interference eliminator 40 to obtain the interference-free front wheel angle signal 43 . At the same time, the non-interference vehicle speed signal 44 and the non-interference front wheel angle signal 43 are used as input of the vehicle two-degree-of-freedom model 42 to obtain a lateral acceleration signal 45 . The yaw rate state observer 14 receives the undisturbed vehicle speed signal 44 and the lateral acceleration signal 45 , and obtains the yaw rate signal 34 of the vehicle through analysis and calculation.

The simulation block diagram of the switch selector is shown in Figure 3. The roll angle signal 32 output by the roll angle sensor 48 and the roll angle analog interference signal 50 output by the roll angle sensor interference simulator 47 are used as the input of the roll angle signal interference canceller 49 to obtain an interference-free roll angle signal 51 . The switch controller 12 accepts the non-disturbance tilt angle signal 51 and the yaw rate signal 34 output by the yaw rate state observer 14 , and verifies whether the vehicle handling stability condition is satisfied, and serves as the control signal of the switch controller 12 . When the vehicle handling stability is normal, the second transmission ratio correction model 13 is executed; when the vehicle handling stability is abnormal, the first transmission ratio correction model 11 is executed. The switch selector 12 inputs the angle motor current signal to the angle motor model 9, and the angle motor model 9 applies an additional angle to the double-row planetary gear train.

There is no clear standard in the industry for the objective evaluation index of vehicle handling stability, and it varies with individual research requirements. In order to ensure the safety of the vehicle, the switch selector described in the present invention takes: 0≤roll angle β≤2.5°, 0≤yaw rate δ≤0.3rad/s as the criteria for vehicle operation stability. When the roll angle β and yaw rate δ meet the above criteria, it is judged that the vehicle handling stability is normal, and the second transmission ratio correction model is executed; when the roll angle β and yaw rate δ meet the above criteria, it is determined that the vehicle handling stability Abnormal stability, execute the first transmission ratio correction model. The above criterion is only a judgment basis, and the specific conditions that should be satisfied by the roll angle β and the yaw rate δ are formulated according to the research and development requirements.

Fig. 4 is a graph of the measured value of the yaw rate sensor and the estimated value of the state observer under the external disturbance. It can be seen from the above figure that under external disturbances, the measured value of the yaw rate sensor will fluctuate to a certain extent due to external disturbances, while the estimated value of the yaw rate obtained by the state observer will not be affected by external disturbances, and the estimated value curve is relatively smooth. Therefore, the value of the yaw rate obtained by the state observer is more accurate than that measured by the sensor, and is not affected by external disturbances.

Utilize the variable transmission ratio control system and control method of the active steering system of the present invention: when the automobile is running at a low speed and the steering wheel has a small turning angle, in order to reduce the burden on the driver and achieve good steering portability, the steering system should have a larger transmission ratio ; And when driving at high speed and with a large steering wheel angle, in order to ensure driving safety and obtain a good steering feel, the steering system should have a smaller transmission ratio. Therefore, it is an ideal steering system to realize the variable transmission ratio function in the active steering system, realize the perfect fusion of the car's steering convenience and steering road feeling, and also organically integrate the safety and flexibility of the car. ,have a broad vision of application.

In summary, the present invention not only considers the influence of vehicle speed on the active steering system, but also considers the influence of the steering wheel speed signal, steering wheel angle signal, and steering wheel angle acceleration signal on the active steering system. The angle motor outputs an additional angle compensation scheme, which improves the control accuracy. The operation of eliminating interference on the vehicle speed signal and the front wheel angle signal further improves the control accuracy.

Claims (3)

1. the control setup of active front steering system variable ratio, comprise conventional gear than control module, PID controller, angle electrical machinery, current probe, the first accumulator/accum, the second accumulator/accum, it is characterized in that the control setup of described active front steering system variable ratio also comprises: the first transmitting ratio correcting module, the second transmitting ratio correcting module, switching selector, yaw velocity state observer; Wherein:

Described conventional gear connects car speed sensor than control module first input end, and the second input termination steering wheel angle sensor, exports termination first accumulator/accum first input end;

Described yaw velocity state observer first input end connects car speed sensor, the second input termination front wheel angle sensor;

Described switching selector first input end connects angle of roll sensor, yaw velocity state observer mouth described in the second input termination;

Described first transmitting ratio correcting module controls switching selector mouth described in termination, and first input end connects bearing circle tachogen, and the second input termination steering wheel angle acceleration pick-up, exports the second input end of the first accumulator/accum described in termination;

Described second transmitting ratio correcting module controls switching selector mouth described in termination, and first input end connects angle of roll sensor, and yaw velocity state observer mouth described in the second input termination, exports the first accumulator/accum second input end described in termination;

Angle electrical machinery mouth described in described current probe input termination, exports the first accumulator/accum the 3rd input end described in termination;

First accumulator/accum mouth described in described PID controller input termination, exports angle electrical machinery input end described in termination;

Described second accumulator/accum first input end switches through angle motor output end, and the second input termination gear drive mouth, exports termination rack and pinion steering gear input end.

2. the control setup of active front steering system variable ratio according to claim 1, is characterized in that the control setup of described active front steering system variable ratio also comprises vehicle speed signal filter, front wheel angle traffic filter;

Wherein: described vehicle speed signal filter input end connects car speed sensor, yaw velocity state observer first input end described in termination is exported; The input termination front wheel angle sensor of described front wheel angle traffic filter, exports yaw velocity state observer second input end described in termination.

3. the control method of active front steering system variable ratio, is characterized in that comprising the steps:

Step 1, builds active front steering system variable ratio control setup as claimed in claim 1 or 2;

Step 2, chaufeur applies corner moment to the bearing circle of active front steering system;

Step 3, the steering wheel angle signal that the vehicle speed signal that conventional gear records according to car speed sensor than control module, steering wheel angle sensor record, obtains desirable angle electrical machinery output current signal;

Step 4, yaw velocity state observer obtains yaw rate signal according to car speed sensor output signal, front wheel angle sensor output signal;

Step 5, switching selector judges vehicle handling stability according to angle of roll sensor output signal, yaw rate signal, and trigger the work of transmitting ratio correcting module and be compensated current signal, concrete mode is as follows:

If when Automobile operation stability is abnormal: switching selector triggers the first transmitting ratio correcting module and obtains the first compensating current signal;

If when Automobile operation stability is normal: switching selector triggers the second transmitting ratio correcting module and obtains the second compensating current signal;

Step 6, first accumulator/accum is the first variable with the desirable angle electrical machinery output current signal described in step 3, be the second variable with the compensating current signal described in step 5, the angle electrical machinery actual output current signal measured with current probe, for ternary, obtains the input of PID controller;

Step 7, PID controller process first accumulator/accum output obtains angle electrical machinery incoming signal, and angle electrical machinery exports additional rotation angle signal;

Step 8, the second accumulator/accum is the first variable with the additional rotation angle signal described in step 7, is the second variable with gear drive output, obtains rack and pinion steering gear incoming signal, and wheel is motion under rack-and-gear rot drives.