CN106043419B - Electric-liquid composite power steering control device and its control method - Google Patents

Abstract

The invention discloses a control device of an electric-hydraulic composite power steering system and a control method thereof, wherein, the power assist part of the electric-hydraulic composite steering system is composed of an electric power boost actuator and a hydraulic power boost actuator, and the power boost coupling module implements two modules The coupling of power assist, the control method selects different steering modes according to the steering wheel angle signal, vehicle speed signal, yaw rate signal, etc., and selects different working modes of the power assist module when the vehicle is in different states, so as to solve the problem of hydraulic power assist in traditional large buses. System, electronically controlled hydraulic power assist system, adjustability of power assist characteristics, and poor steering feel at medium and high speeds.

Description

Electro-hydraulic hybrid power steering system control device and control method thereof

technical field

The invention relates to the technical field of automobile power steering system control, and specifically refers to an electric-hydraulic compound power steering system control device and a control method based on the system.

Background technique

At present, the power steering systems commonly used in existing automobiles include: hydraulic power steering systems, electronically controlled hydraulic power steering systems and electric power steering systems. Among them, the hydraulic power steering system and the electronically controlled hydraulic power steering system can provide greater power assistance under low-speed operating conditions and reduce the burden on the driver when steering; however, the steering feel is poor under high-speed operating conditions, and there are problems with handling stability. The electric power steering system is composed of a controller, a power assist motor, a steering wheel torque sensor of a reduction mechanism, and a vehicle speed sensor. The controller receives and processes the steering wheel torque signal and vehicle speed signal measured by the sensor, and controls the motor to Characteristic output assist torque. However, affected by the electrical characteristics of the vehicle itself, such as the battery voltage, the maximum output torque is relatively small, which does not meet the needs of vehicles such as large buses.

The robustness of the control system originates from practical engineering problems. The performance and quality of an ideal automatic control system should accurately achieve the expected design requirements, but the uncertainty of the controlled object is unavoidable, so the controlled object contains uncertainty Under the premise of , it becomes a very important subject to make the system close to the ideal design index. The traditional control theory based on the study of time-invariant and deterministic control objects cannot solve the problem of robust control of the system, while the Hinf control theory and its LMI algorithm in the robust control theory are classic tools for the robust system design of linear systems. Effectively suppress the impact of uncertain interference on the system. This system adopts Hinf control theory as the theoretical basis to solve the research of system control technology.

Contents of the invention

Aiming at the deficiencies of the above-mentioned prior art, the object of the present invention is to provide an electric-hydraulic hybrid power steering system control device and its control method to solve the problems of the hydraulic power steering system and the electronically controlled hydraulic power steering system in the prior art. Under working conditions, the steering feel is poor, the steering stability is poor, and the maximum power torque output by the electric power steering system is small.

In order to achieve the above object, a control device for an electro-hydraulic hybrid power steering system of the present invention includes: a mechanical torque control module, a Hinf control module, an electric power boost actuator, a hydraulic power boost actuator, a mode selector, a current control module, Torque coupling module, current detection module, ECU, which also includes: electric power assist mode judger, hydraulic power assist mode judger, composite power assist mode judger;

The input end of the mechanical torque control module is connected to a sensor module composed of a vehicle speed sensor, a steering wheel torque sensor, and a steering wheel angle sensor, and the output end is connected to a current control module;

The input end of the mode selector is connected to the ECU, and the output end is connected to the electric assist mode judger, the hydraulic assist mode judger, and the compound assist mode judger;

The output terminals of the electric power assist mode judger, the hydraulic power assist mode judger, and the composite power assist mode judger are connected to the current control module;

The current detection module feeds back the actual value of the control current of the electric booster actuator and the hydraulic booster actuator to the input terminal of the Hinf control module;

The input end of the Hinf control module is connected to the current control module, and the output end is connected to the electric power assist actuator and the hydraulic power assist actuator;

The input end of the torque coupling module is connected with the electric power assist actuator and the hydraulic power assist actuator, and the output end is connected with the steering gear.

Preferably, the hydraulic booster actuator includes: a booster motor A, a booster oil pump, a rotary valve, and a hydraulic booster cylinder; the booster motor A drives the booster oil pump to rotate, pumps the booster oil from the oil storage tank into the rotary valve, and the booster oil passes through Rotary valves with different openings flow into both sides of the hydraulic booster cylinder to generate a hydraulic pressure difference; the electric booster actuator includes: booster motor B and a reduction mechanism, the output torque of the booster motor B is decelerated and increased by the reduction mechanism, and then output to the mechanical steering module.

A steering mode switching control method of an electro-hydraulic hybrid power steering system according to the present invention comprises the following steps:

(1) Input steering torque to the electro-hydraulic compound steering system through the steering wheel;

(2) The mechanical torque control module obtains the total assist current according to the vehicle speed signal measured by the vehicle speed sensor, the rotation angle signal measured by the steering wheel angle sensor, and the torque signal measured by the steering wheel torque sensor; the ECU converts the total assist current The size and current working condition parameters of the vehicle are input to the mode selector, and the current required steering mode of the vehicle is judged by the electric power assist mode judger, the hydraulic power assist mode judger, and the compound power assist mode judger, and the output current is sent to the current control module;

(3) The Hinf control module processes the output current of the current control module, and controls the electric power assist actuator and the hydraulic power assist actuator to output corresponding power;

(4) The current detection module feeds back the actual value of the control current of the electric power-assisted actuator and hydraulic power-assisted actuator to the input terminal of the Hinf control module to eliminate the tracking error between the system target signal and the actual signal;

(5) The torque coupling module processes the power output from the electric power assist actuator and the hydraulic power assist actuator, and outputs the total power assist value to the mechanical steering mechanism to realize power steering.

Preferably, the above step (3) specifically includes: w represents the disturbance input of the control system, w=[θ _s Q _s T _R ] ^T , W _w =[W _w1 , W _w2 , W _w3 ] represents the weight of the disturbance input w Function matrix, W _w1 , W _w2 , W _w3 represent the weighting functions of steering wheel input, road disturbance input, and power steering pump flow input respectively; G(s) represents the system transfer function, K(s) represents the compound steering system controller, by reference input And the power ratio characteristic is calculated to obtain the system control input u=[T _em ] so as to ensure the stable operation of the system, T _em represents the output of the control motor; d _s represents the sensor disturbance input;

e represents system evaluation index, z1, z2 and z3 represent system output error, controller output and system output respectively; W ₁ , W ₂ and W ₃ represent system tracking performance, controller output and robust performance weighting function respectively, through W ₁ , W ₂ and W ₃ three performance weighting functions to adjust the corresponding evaluation output of the system respectively; the system must meet the H _∞ norm of the transfer function from the interference input w to the evaluation output z is less than a given value, and the H _∞ norm can be solved for The system controller K is obtained; among them, G _w1 , G _w2 , and G _w3 represent the transfer functions of steering wheel input, road surface disturbance input, and power steering pump flow input respectively; G ₀ represents the system transfer function;

u=K·y

e=F _l (P(s),K(s))w

In the formula: u = [T _em ].

Beneficial effects of the present invention:

1. Comprehensively considering the influence of vehicle speed and steering wheel rotation speed on the electro-hydraulic compound steering system, when the vehicle is in different states, the steering mode of the electro-hydraulic compound steering system is quickly switched, which improves the torque control accuracy of the steering wheel and improves the Handling stability of vehicle driving.

2. Realize the multi-steering mode function in the power steering system of the car, which can switch the steering mode according to different working conditions, realize the perfect fusion of the car's steering convenience and steering road feeling, and also combine the economy and flexibility of the car's power steering Therefore, it has a broad market application prospect.

Description of drawings

Fig. 1 depicts a structural block diagram of the steering system control device of the present invention;

Figure 2 shows the schematic diagram of the torque control strategy of the Hinf control module.

Detailed ways

In order to facilitate the understanding of those skilled in the art, the present invention will be further described below in conjunction with the embodiments and accompanying drawings, and the contents mentioned in the embodiments are not intended to limit the present invention.

Referring to Fig. 1, a control device for an electro-hydraulic hybrid power steering system of the present invention is applied to an electro-hydraulic hybrid steering system, and the system includes: a driver model 1, a steering wheel model 2, a torque sensor 3, Steering gear 4, wheel 5;

The driver model 1 inputs the steering torque through the steering wheel model 2, transmits the torque to the wheels 5 through the steering column and the steering gear 4, drives the wheels 5 to rotate, and realizes system steering.

The above-mentioned control device includes: a mechanical torque control module 6, a Hinf control module 8, an electric power assist actuator 9, a hydraulic power assist actuator 10, a mode selector 14, a current control module 7, a torque coupling module 11, and a current detection module 12, The ECU 13 also includes: an electric power assist mode judger 15, a hydraulic power assist mode judger 16, and a composite power assist mode judger 17;

The input end of the mechanical torque control module 6 is connected to the sensor module composed of the vehicle speed sensor, the steering wheel torque sensor and the steering wheel angle sensor, and the output end is connected to the current control module 7, and the input is the vehicle speed signal 19 and the steering wheel torque sensor 3 The output torque signal 18 is the total power assist current signal 20; among them, the vehicle speed sensor: used to detect the vehicle speed, usually installed in the drive axle housing; the steering wheel torque sensor: used to detect the steering wheel torque, Usually installed on the steering tube shaft of the steering wheel; steering wheel angle sensor: used to detect the steering wheel angle, usually installed on the steering tube shaft of the steering wheel;

The input end of the mode selector 14 is connected to the ECU 13, the input is the ECU control current 21, and the output end is connected to the electric power assist mode judger 15, the hydraulic power assist mode judger 16, and the composite power assist mode judger 17;

The output terminals of the electric power assist mode determiner 15, the hydraulic power assist mode determiner 16, and the compound assist mode determiner 17 are connected to the current control module 7, and the current control module 7 receives the control signals 22 of each mode determiner and the total assist current signal 20 , output the control current 23 to the Hinf control module 8;

The input end of the Hinf control module 8 is connected to the current control module 7 to receive the control current; the output end is connected to the electric booster actuator 9 and the hydraulic booster actuator 10, and outputs a control signal 24 to both; the current detection module 12 connects the electric booster The signal 25 output by the actuator 9 and the hydraulic power-assisted actuator 10 is detected, and the control current 26 is fed back to the Hinf control module 8 to eliminate the signal tracking error,

The input end of the torque coupling module 11 is connected with the electric booster actuator 9 and the hydraulic booster actuator 10, the input is the output boost torque 27 of the two actuators, the output end is connected with the steering gear, and the output is the coupling boost torque 28; the electric booster actuator 9. The power assist output by the hydraulic power assist actuator 10 is output to the steering gear 4 through the torque coupling module 11 to realize power steering.

Wherein, the hydraulic booster actuator includes: a booster motor A, a booster oil pump, a rotary valve, and a booster hydraulic cylinder; the booster motor A drives the booster oil pump to rotate, pumps the booster oil from the oil storage tank into the rotary valve, and the booster oil passes through the rotary valve. Different valve openings flow into both sides of the hydraulic booster cylinder to generate a hydraulic pressure difference; the electric booster actuator includes: booster motor B and a reduction mechanism, the output torque of the booster motor B is decelerated and increased by the reduction mechanism, and then output to the mechanical steering module .

A steering mode switching control method for an electro-hydraulic hybrid power steering system, comprising the following steps:

(1) Input steering torque to the electro-hydraulic compound steering system through the steering wheel;

(2) The mechanical torque control module obtains the total assist current according to the vehicle speed signal measured by the vehicle speed sensor, the rotation angle signal measured by the steering wheel angle sensor, and the torque signal measured by the steering wheel torque sensor; the ECU converts the total assist current The size and current working condition parameters of the vehicle are input to the mode selector, and the current required steering mode of the vehicle is judged by the electric power assist mode judger, the hydraulic power assist mode judger, and the compound power assist mode judger, and the output current is sent to the current control module;

(3) The Hinf control module processes the output current of the current control module, and controls the electric power assist actuator and the hydraulic power assist actuator to output corresponding power;

As shown in Figure 2, w represents the disturbance input of the control system, w=[θ _s Q _s T _R ] ^T , W _w =[W _w1 ,W _w2 ,W _w3 ] represents the weighting function matrix of the disturbance input w, W _w1 , W _w2 , W _w3 represent the weighting functions of steering wheel input, road surface disturbance input, and power steering pump flow input respectively; G(s) represents the system transfer function, K(s) represents the compound steering system controller, and is determined by the reference input And the power ratio characteristic is calculated to obtain the system control input u=[T _em ] so as to ensure the stable operation of the system, T _em represents the output of the control motor; d _s represents the sensor disturbance input;

e represents system evaluation index, z1, z2 and z3 represent system output error, controller output and system output respectively; W ₁ , W ₂ and W ₃ represent system tracking performance, controller output and robust performance weighting function respectively, through W ₁ , W ₂ and W ₃ three performance weighting functions to adjust the corresponding evaluation output of the system respectively; the system must meet the H _∞ norm of the transfer function from the interference input w to the evaluation output z is less than a given value, and the H _∞ norm can be solved for The system controller K is obtained; among them, G _w1 , G _w2 , and G _w3 represent the transfer functions of steering wheel input, road surface disturbance input, and power steering pump flow input respectively; G ₀ represents the system transfer function;

u=K·y

e=F _l (P(s),K(s))w

In the formula: u = [T _em ].

(4) The current detection module feeds back the actual value of the control current of the electric power-assisted actuator and hydraulic power-assisted actuator to the input terminal of the Hinf control module to eliminate the tracking error between the system target signal and the actual signal;

(5) The torque coupling module processes the output power of the electric power assist actuator and the hydraulic power assist actuator, and outputs the total power assist value to the mechanical steering mechanism to realize power steering.

Utilizing the control device and control method of the present invention, the vehicle performs mode switching between the compound steering mode, the electric power assist mode and the hydraulic steering mode according to the vehicle speed and other state quantities during driving, that is, the compound power steering mode is executed at a low speed, through two Two booster modules work together to meet the booster demand; at high speeds, the electric booster mode is implemented, and only a single module works to provide the driver with an appropriate booster value, ensuring the bus's handling stability and good road feel. By switching the corresponding steering mode of the vehicle under different working conditions, the handling stability and driving safety of the vehicle at medium and high speeds are effectively improved. The energy loss in the environment, so it has a broad market prospect.

The present invention comprehensively considers the relationship between vehicle speed, steering wheel torque and other state variables and the cooperative work of the two booster modules, and adopts a "total-divided" method to control the current of the electric booster actuator and the hydraulic booster actuator, which improves the electric-power booster. The control accuracy of the steering mode switching of the hydraulic compound steering system.

There are many specific application approaches of the present invention, and the above description is only a preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, some improvements can also be made without departing from the principles of the present invention. Improvements should also be regarded as the protection scope of the present invention.

Claims (4)

1. a kind of electric-liquid composite power steering control device, including：Machine torque control module, Hinf control modules, electricity Dynamic power-assisted actuation mechanism, hydraulic booster executing agency, mode selector, current control module, moment coupling module, current detecting Module, ECU, which is characterized in that further include：Electric boosted mode decision device, hydraulic booster mode decision device, compound assistant mode Determining device；

The machine torque control module input terminal and vehicle speed sensor, steering-wheel torque sensor, steering wheel angle sensor The sensor assembly of composition is connected, and output terminal is connected with current control module；

The mode selector input is connected with ECU, output terminal and electric boosted mode decision device, hydraulic booster mode decision Device, compound assistant mode determining device are connected；

The electric boosted mode decision device, hydraulic booster mode decision device, compound assistant mode determining device output terminal and electric current Control module is connected；

The current detection module feeds back to electric boosted executing agency, hydraulic booster actuating mechanism controls electric current actual value Hinf control module input terminals；

The Hinf control modules input terminal is connected with current control module, and output terminal is helped with electric boosted executing agency, hydraulic pressure Power executing agency is connected；

The moment coupling module input is connected with electric boosted executing agency, hydraulic booster executing agency, and output terminal is with turning It is connected to device.

2. electric-liquid composite power steering control device according to claim 1, which is characterized in that the hydraulic pressure helps Power executing agency includes：Assist motor A, power-assisted oil pump, rotary valve, booster cylinder, assist motor A driving power-assisted oil pump rotations, Power-assisted fluid is pumped into rotary valve by oil storage tank, power-assisted fluid flows into servohydraulic cylinder both sides by rotary valve aperture difference, generates liquid Press pressure difference；The electric boosted executing agency includes：Assist motor B, deceleration mechanism, assist motor B output torques are via deceleration Mechanism slows down after increasing square, exports to mechanical steering module.

3. a kind of electric-liquid composite power steering steering pattern method for handover control, which is characterized in that include the following steps：

(1) steering moment is inputted to electric-liquid composite turning system by steering wheel；

(2) what machine torque control module is measured according to vehicle speed sensor speed signal, steering wheel angle sensor measured turns The dtc signal that angle signal, steering-wheel torque sensor measure obtains total power-assisted size of current；ECU is by total power-assisted size of current With vehicle current working parameter input pattern selector, by electric boosted mode decision device, hydraulic booster mode decision device, answer Closing assistant mode determining device, current desired steering pattern judges to vehicle, outputs current to current control module；

(3) Hinf control modules processing current control module output current controls electric boosted executing agency, hydraulic booster to perform Mechanism the output phase answers power-assisted；

(4) current detection module feeds back to electric boosted executing agency, hydraulic booster actuating mechanism controls electric current actual value Hinf control module input terminals, to eliminate the tracking error of aims of systems signal and actual signal；

(5) moment coupling module handles, and will be total electric boosted executing agency, hydraulic booster executing agency output power-assisted Power-assisted value is exported to mechanical steering gear, realizes power-assisted steering.

4. electric-liquid composite power steering steering pattern method for handover control according to claim 3, feature exist In above-mentioned steps (3) specifically include：W represents the exogenous disturbances of control system, w=[θ_s Q_s T_R]^T, W_w=[W_w1,W_w2,W_w3] table Show the weight function matrix of exogenous disturbances w, W_w1,W_w2,W_w3Steering wheel input, road agitation input, power assistance pump for steering are represented respectively The weighting function of flow input；G (s) represents ssystem transfer function, and K (s) represents composite turning system controller, by reference input AmountAnd system control input quantity u=[T are calculated in power-assisted proportionality_em] so as to ensure system stable operation, T_emIt represents Control motor output；d_sRepresent sensor disturbance input；

E represents system evaluation index, and z1, z2 and z3 represent system output errors, controller output and system output respectively；W₁, W₂ And W₃System tracking performance, controller output, robust performance weighting function are represented respectively, pass through W₁, W₂And W₃Three performance weightings Function adjusts system and evaluates output accordingly respectively；System must meet exogenous disturbances w to the H of evaluation output z transmission functions_∞Norm Less than set-point, H is solved_∞Norm, you can obtain system controller K；Wherein, G_w1、G_w2、G_w3Steering wheel input, road are represented respectively Face exogenous disturbances, the transmission function of power steering pump discharge input；G₀Represent ssystem transfer function；

U=Ky

E=F_l(P(s),K(s))w

In formula：U=[T_em]。