CN105128929A - Intelligent drive-by-wire electro-hydraulic steering system - Google Patents

Abstract

The invention relates to an intelligent automobile wire-controlled electro-hydraulic power steering system and a control method thereof. The system consists of a steering wheel-road sensor motor assembly, an electric-hydraulic power assist device, and a steering control unit. Among them, the road sense motor is connected to the steering shaft through the worm gear and worm, which simulates the steering road feel and makes the steering wheel actively return to normal; the steering motor is connected to the rotary valve spool of the hydraulic steering gear through the worm gear and worm, and the torque of the motor can be transmitted through the torsion bar on the one hand. To overcome the steering resistance for the steering gear, on the other hand, it can control the relative rotation of the spool and the valve sleeve to control the opening of the rotary valve, and then control the size of the hydraulic booster. There are two working modes: electric and hydraulic work together, and electric power assist alone. In terms of control methods, the road sensor motor, steering motor, and steering pump are controlled based on information such as driver actions, road conditions, vehicle status, and system parameters to achieve power assist control, damping control, centering control, assisted driving, and automatic parking. car and other functions.

Description

An intelligent wire-controlled electro-hydraulic steering system

technical field

The invention relates to an automobile steering system, in particular to an intelligent automobile wire-controlled electro-hydraulic steering system and a control method thereof, belonging to the field of motor vehicle power steering.

Background technique

The automobile steering system has developed from a simple mechanical steering system and a hydraulic power steering system to an electro-hydraulic power steering system (Electro-hydraulic Power Steering, EHPS) and an electric power steering system (Electric Power Steering, EPS), which are currently widely used. The electrification of the steering system reduces the energy consumption of the system and improves the steering performance. On this basis, in order to further improve the handling stability, active safety and driver comfort of the vehicle, the development of automobile technology has become more and more intelligent. The intelligence of the steering system provides the basis for car safety, assisted driving and autonomous driving vehicles, and is an important part of the integrated control of the car chassis and smart cars.

For the power steering system, the latest research results include electric power steering system (EPS), electrohydraulic power steering system (EHPS) and steering by wire (SBW). BMW, Nissan, Volvo and other large international car companies have successively announced that they will develop self-driving technology. Audi can realize self-parking with one touch of an application on a smartphone. The driverless car developed by Google has already entered people's field of vision.

AFS, jointly developed by BMW and ZF, adds an input degree of freedom through a set of corner motors and double-row planetary gear trains to achieve additional steering, and the Servtronic hydraulic servo steering system is used to realize the power steering function. Audi's dynamic steering system superimposes the output power of the motor in parallel with the driver's steering power through the harmonic gear transmission mechanism, and provides speed-dependent power assistance through Sevotronic. The electrical system has the advantages of simple and precise control. At the same time, the hydraulic system itself has energy density. Large, short lag time, good steering follow-up characteristics, strong resistance to road impact, low operating noise, uniform and stable transmission movement, etc., the combination of the two can realize that the power assist changes according to the power assist characteristic curve, and has good steering characteristics.

As for the steer-by-wire system, the mechanical connection such as the steering column is removed, which avoids the damage of the steering column to the driver in a collision accident, and improves the safety performance of the car; based on the steering power control based on relevant parameters such as vehicle speed and road surface information, It can improve the driving characteristics and enhance the handling stability; the "road feeling" is generated by simulation, and the information that can best reflect the actual driving state of the car and the road surface conditions can be extracted from the signal, thereby providing the driver with a more realistic "road feeling"; eliminating By connecting the mechanical structure, the steering system can be arranged more conveniently, and the vibration of the wheels will not be transmitted to the driver. Based on the road surface recognition information, steering correction, assisted driving and intelligent parking can be realized, which can reduce driver fatigue and enhance active safety. It is now considered to combine the electric power steering system and the hydraulic power steering system based on the wire control technology to improve the steering performance.

Contents of the invention

In view of the above problems, the object of the present invention is to develop an intelligent steer-by-wire system capable of realizing high efficiency and energy saving, controllable power assist, active centering, assisted driving and automatic parking.

In order to achieve the above purpose, the present invention discloses a control-by-wire electro-hydraulic power steering system, which integrates control-by-wire technology, electric power assist and hydraulic power steering into one system, and mainly includes the following structures:

(1) Steering wheel assembly, including steering wheel, steering wheel torque, angle sensor and road sensor motor, etc. The road sense motor is connected to the steering shaft through a worm gear mechanism, simulating the steering road sense and making the steering wheel actively return to normal;

(2) Steering motor and hydraulic booster assembly. The steering motor is connected to the rotary valve spool of the hydraulic power steering system through a worm gear reduction mechanism. On the one hand, the torque of the motor can be transmitted to the steering gear through the torsion bar to overcome the steering resistance. On the one hand, the relative rotation between the rotary valve spool and the valve sleeve can be controlled to control the opening of the rotary valve, and then control the size of the hydraulic boost;

(3) The oil pump is driven by the engine through the belt, and the belt input shaft is designed with an electromagnetic clutch to control the working state of the hydraulic system. At high speeds, the steering resistance is small, and the power is only provided by the motor to achieve energy-saving design.

Specifically, the driver's force on the steering wheel is transmitted to the steering wheel torque and rotation angle sensor through the steering column, and the information is converted into digital signals for the steering control unit (ECU) to make decisions. The road sense motor analyzes the road surface and vehicle status transmitted from the steering ECU through the worm gear reduction mechanism to simulate the "road sense", and returns the steering wheel to the right after the steering action is completed.

Steering actuators include motors, reduction mechanisms, rotary valves, rack and pinion hydraulic power steering gears, etc. The steering force is jointly provided by the electric power assist device and the hydraulic power assist device, and the two can be properly matched to meet the steering requirements. The steering ECU judges the required steering force based on the collected engine ignition signal, vehicle speed sensor, preview road surface information, yaw rate and other vehicle states, steering wheel torque and angle, voltage and current of the steering motor, and the position of the steering rack. The size, and then determine the power distribution of the electric power assist and hydraulic power assist system. Among them, the electric power assist device can not only provide partial power assist, but also overcome the steering resistance through the mutual cooperation of the electric motor and the hydraulic power steering system, so as to realize variable power steering.

When driving at low speed, the steering resistance is relatively large, and the electric motor and hydraulic power steering work together to overcome the steering resistance; when driving at high speed, the required steering force is small, so the hydraulic power assist can be turned off to save energy, and only the electric power assist is retained. And the motor has the function of active steering, which can compensate the influence of side wind or road surface unevenness on the steering wheel. On the basis of image recognition of white lines on the road surface to provide preview information, it can realize automatic correction of straight driving direction and lane adjustment. Auxiliary functions are maintained; the current and voltage through the motor can also estimate the steering load.

The steering motor is a brushless DC motor. Measures are taken to limit the impact of current in the speed control system. The speed and current double closed-loop control speed control system is adopted. The double closed-loop speed control system has good anti-interference and starting performance, and can meet the requirements of the system. need.

The steering oil pump is driven by the engine through the belt, and the belt input shaft is designed with an electromagnetic clutch to control the working state of the hydraulic system. At high speeds, the steering resistance is small, and the power assist is only provided by the steering motor, realizing energy-saving design. In addition, an electric steering oil pump can also be considered to realize the oil supply and control of the hydraulic system, especially for electric vehicles.

The intelligent control of the system is reflected in the fact that the motor can adjust the power assist of the motor itself and the magnitude of the hydraulic power assist according to the driving state of the vehicle, and the active steering can be realized through the motor when the driver has no steering related intentions, which can realize automatic driving on good road surfaces. Driving and automatic parking functions.

Description of drawings

The above structure of the present invention can be further illustrated by the accompanying drawings.

Fig. 1 is the steering wheel, sensor and road sensor motor assembly of the intelligent wire-controlled electro-hydraulic steering system;

Fig. 2 is the steering actuator assembly of the intelligent wire-controlled electro-hydraulic steering system;

Fig. 3 is a structural diagram of the electro-hydraulic booster device of the intelligent control-by-wire electro-hydraulic steering system;

Fig. 4 is a structural diagram of the oil pump clutch of the intelligent control-by-wire electro-hydraulic steering system;

Fig. 5 is a schematic diagram (middle position) of the intelligent control-by-wire electro-hydraulic steering system;

Fig. 6 is a control principle block diagram of the intelligent control-by-wire electro-hydraulic steering system.

In the above Figure 1, 1 is the steering wheel; 2 is the steering column; 3 is the steering wheel torque and angle sensor; 4 is the worm gear; 5 is the road sensor motor.

In Fig. 3, 6 is a steering motor; 7 is a casing; 8 is a worm gear; 9 is a valve core; 10 is a torsion bar; 11 is a valve sleeve; 12 is a steering gear; 13 is a clearance adjustment mechanism; 14 is a steering rack; 15 is the rotary valve housing.

Among Fig. 4, 16 is an input shaft; 17 is an electromagnet; 18 is a magnetizer; 19 is a yoke; 20 is a pulley.

Detailed ways

As shown in Figure 1, the steering wheel assembly includes a steering wheel 1, a steering wheel torque and angle sensor 3, a road sensor motor 5, and the like. The steering wheel is connected to the steering column 2, and the steering column is connected to the steering shaft through a cross coupling. After the steering shaft is interrupted, the steering wheel torque and angle sensor 3 is installed, and the output of the steering shaft is connected to the road through the worm gear 4 reduction mechanism. Induction motor 5, the whole device is connected to the cockpit through the housing etc., and when the vehicle hits, the crash of the steering wheel is considered to ensure the safety of the driver.

As shown in Figures 2 and 3, the steering actuator is integrated with electric power assist and hydraulic power assist. The steering motor 6 is connected to the input end of the hydraulic power assist system (HPS) through a worm gear 8 worm reduction mechanism. The steering force applied by the steering motor 6 can be passed through the torque The rod 10 is transmitted to the rack and pinion steering gear, which can make the rotary valve spool 9 and the valve sleeve 11 rotate relative to each other, control the opening of the rotary valve, and then determine the magnitude of the power assist in the case of hydraulic power assist.

As shown in Figure 4, the oil pump clutch is an electromagnetic clutch. When the hydraulic power is not needed, the electromagnetic clutch is powered off and the input shaft 16 is idling. The latter rotate synchronously due to friction, and drive the belt to rotate, and then drive the steering oil pump.

Figure 5 shows the schematic diagram of the wire-controlled hydraulic steering system, which is basically composed of steering wheel assembly, electric power assist device, hydraulic power assist device assembly, steering control unit (ECU) and so on. Figure 6 is the control block diagram of the system. The signals collected by the ECU include the ignition signal of the engine, the vehicle yaw rate, the preview road surface information, the vehicle speed and other vehicle states, the driver's actions such as the steering wheel torque and angle, the road sensor motor and the steering motor. The system parameters such as the voltage and current of the steering rack and the position information of the steering rack, through the corresponding control algorithm, control the road sense motor, steering motor and oil pump clutch, and then power assist control, damping control, return control, and further control the steering system Carry out assisted driving and automatic driving.

Claims (5)

1. an intelligentized automobile line traffic control electricity liquid servo steering system and control method thereof.It is characterized in that: primarily of bearing circle-road feel motor assembly, electro-hydraulic work-saving device, turning control cell composition.

2. bearing circle-road feel the motor assembly of line traffic control electricity liquid servo steering system according to claim 1, its architectural feature is: road feel motor is connected with steering shaft by worm and gear, simulation steering feel also makes bearing circle initiatively just return, moment of torsion and rotary angle transmitter, between bearing circle and worm gear, experience hand-power and the steering wheel angle of chaufeur.

3. the electro-hydraulic work-saving device of line traffic control electricity liquid servo steering system according to claim 1, it is characterized in that: steer motor is connected with the rotary valve spool of HPS by worm and gear, can pass to steering gear by torsion bar overcomes cornering resistance to the moment of motor on the one hand, the aperture relatively rotating to control rotary valve of spool and valve pocket can be controlled on the other hand, and then the size of hydraulic control power-assisted.

4. the turning control cell of line traffic control electricity liquid servo steering system according to claim 1, it is characterized in that: according to information such as driver actions, condition of road surface, vehicle-state and system parameters, satisfy the need electrification machine, steer motor and power steerig pump controls, to reach Power assisted control, damping control, rotary transform tensor, auxiliaryly to drive and the function such as automatic parking.

5. line traffic control electricity liquid servo steering system according to claim 1, is characterized in that: mode of operation has electronic and hydraulic pressure co-operation, electric boostedly work independently two kinds.