CN113074962B

CN113074962B - Vehicle braking and steering system integrated test bench

Info

Publication number: CN113074962B
Application number: CN202110433712.2A
Authority: CN
Inventors: 朱冰; 靳万里; 赵健; 陈国胜; 康宇; 卜纯研; 李波; 姜景文
Original assignee: Jilin University
Current assignee: Sinotest Equipment Co ltd
Priority date: 2021-04-21
Filing date: 2021-04-21
Publication date: 2022-06-14
Anticipated expiration: 2041-04-21
Also published as: CN113074962A

Abstract

The invention discloses a vehicle braking and steering system integrated test bench, which comprises a brake-by-wire system, a steering-by-wire system, an electric cylinder, a driving robot, a data acquisition and control system, an upper computer and a power supply system, wherein the electric cylinder is connected with the brake-by-wire system through an input push rod, the driving robot is connected with a steering wheel in the steering-by-wire system, the data acquisition and control system is respectively in circuit connection with the brake-by-wire system, the electric cylinder, the steering-by-wire system and the driving robot, the data acquisition and control system respectively acquires sensor signals inside the brake-by-wire system, the electric cylinder, the steering-by-wire system and the driving robot through a signal acquisition circuit and sends control signals to ECU (electronic control unit) in the brake-by-wire system, the electric cylinder, the steering-by-wire system and the driving robot through a driving circuit, and has the advantages that: the dynamic and standardized test method can be matched with the requirements of relevant regulatory standards, and the dynamic and standardized test under the integrated braking and steering system is completed.

Description

Vehicle braking and steering system integrated test bench

Technical Field

The invention relates to an integrated test bed, in particular to an integrated test bed for a vehicle braking and steering system.

Background

At present, with the development of the automobile industry to electromotion, intellectualization and networking, the development trend of an automobile chassis system is as follows: the traditional chassis system taking machinery as the main chassis system is changed into an electric control chassis system. Specifically, in terms of a braking and steering system, the electronic booster replaces a vacuum booster to realize the functions of friction braking force, regenerative braking, active pressure building and the like, and the Electric Power Steering (EPS) replaces an original mechanical steering gear to realize the functions of power steering, active steering and the like. The increase of the electric control system of the vehicle chassis can bring the problems of coupling conflict between the electric control systems, cost increase, difficulty in ECU function cooperation, waste of computing resources and the like, and in order to solve the problems, the integration of the electric control system of the chassis is a necessary route.

However, at present, no special hardware-in-loop (HIL) rack is used for function development, matching and verification of a chassis electric control system (including an electromechanical liquid actuating mechanism in a loop), and real vehicle testing has the defects of high time cost, poor economy, low efficiency, poor repeatability and the like, so that once problems occur in the development process of the automobile chassis electric control system, the problems are difficult to solve in time. In addition, most of the electronic boosters, electronic stability control systems (ESCs) and electric power steering systems of the whole vehicle enterprises come from different suppliers, and when functional interaction causes problems, the performance of the whole vehicle is reduced, so that the whole vehicle enterprises are difficult to quickly and accurately find responsible parties, investigate related responsibilities and solve the problems.

In order to solve the above problems, it is necessary to establish an integrated testing experiment table for a braking and steering system, and perform a performance test on the integrated system in a V-flow development period of an automobile product, so as to quickly find and solve the problems, improve the product development efficiency, shorten the development period, reduce the research and development cost, and reduce the safety risk of a real-vehicle road test as much as possible.

Disclosure of Invention

The invention aims to solve the problems that in the V flow development period of an automobile product, the performance test of an integrated system is carried out so as to find and solve problems quickly, improve the product development efficiency, shorten the development period, reduce the research and development cost and reduce the safety risk of a real automobile road test as much as possible, and provides an integrated test bench for a vehicle braking and steering system.

The invention provides a vehicle brake and steering system integrated test bench which comprises a brake-by-wire system, a steering-by-wire system, an electric cylinder, a driving robot, a data acquisition and control system, an upper computer and a power supply system, wherein the electric cylinder is connected with the brake-by-wire system through an input push rod, the driving robot is connected with a steering wheel in the steering-by-wire system, the data acquisition and control system is respectively in circuit connection with the brake-by-wire system, the electric cylinder, the steering-by-wire system and the driving robot, the data acquisition and control system respectively acquires sensor signals inside the brake-by-wire system, the electric cylinder, the steering-by-wire system and the driving robot through a signal acquisition circuit and sends control signals to ECU (electronic control Unit) in the brake-by-wire system, the electric cylinder, the steering-by-wire system and the driving robot through a driving circuit, and the data acquisition and control system controls the brake-by-wire system, the steering system, The electric control system comprises an electric cylinder, a steer-by-wire system and a driving robot, wherein a power supply system is respectively connected with the steer-by-wire system, the electric cylinder, the steer-by-wire system and the driving robot and provides electric power for the steer-by-wire system, the electric cylinder, the steer-by-wire system and the driving robot, and an upper computer is connected with a data acquisition and control system through an Internet network cable to realize signal acquisition and control signal transmission.

The brake-by-wire system comprises an electronic booster, a brake master cylinder, a liquid storage pot, a hydraulic control unit and a brake cylinder, wherein the input end of the electronic booster is connected with an electric cylinder through an input push rod, the output end of the electronic booster is connected with a first piston in the brake master cylinder, the liquid storage pot is communicated with the brake master cylinder through two liquid conveying pipelines, the brake master cylinder is communicated with the hydraulic control unit through two pipelines, the hydraulic control unit is communicated with the brake cylinder through four pipelines, hydraulic oil flows out of two liquid outlets of the liquid storage pot and flows into the brake master cylinder through two liquid outlets after being pressurized by the brake master cylinder, the hydraulic oil flows into the brake cylinder through the regulation action of the hydraulic control unit, the hydraulic pressure in the brake cylinder is converted into wheel braking force, a pedal force sensor and a pedal stroke sensor are arranged on the input push rod connected between the electronic booster and the electric cylinder, a first hydraulic pressure sensor and a second hydraulic pressure sensor are respectively assembled on two pipelines communicated between the brake master cylinder and the hydraulic control unit; the four communicating pipelines between the hydraulic control unit and the brake wheel cylinder are respectively provided with a third hydraulic pressure sensor, a fourth hydraulic pressure sensor, a fifth hydraulic pressure sensor and a sixth hydraulic pressure sensor, the electronic booster, the hydraulic control unit, the pedal force sensor, the pedal stroke sensor, the first hydraulic pressure sensor, the second hydraulic pressure sensor, the third hydraulic pressure sensor, the fourth hydraulic pressure sensor, the fifth hydraulic pressure sensor and the sixth hydraulic pressure sensor are all connected with a data acquisition and control system, the pedal force sensor, the pedal stroke sensor, the first hydraulic pressure sensor, the second hydraulic pressure sensor, the third hydraulic pressure sensor, the fourth hydraulic pressure sensor, the fifth hydraulic pressure sensor and the sixth hydraulic pressure sensor can transmit acquired data to the data acquisition and control system in real time, and the data acquisition and control system controls the work of the electronic booster and the hydraulic control unit, the electronic booster is connected with the hydraulic control unit through a CAN bus to realize communication.

The electronic booster comprises an electric control unit, a permanent magnet synchronous motor, a primary gear speed reducing mechanism, a secondary gear speed reducing mechanism, a ball screw speed reducing mechanism, a boosting valve body, a displacement difference sensor, an input push rod, a spring, a feedback disc, an output push rod and a connecting plate, wherein the input push rod, the feedback disc and the output push rod are vacuum boosters, and the input push rod is connected with an electric cylinder through the connecting plate and used for inputting braking force; the connecting plate is in a stepped cylindrical shape, a threaded hole is processed at one end along the axis of the connecting plate, and the connecting plate is in transition fit with an output shaft of the electric cylinder through the threaded hole; a blind hole is processed along the other end of the axis of the connecting plate, the connecting plate is in transition fit with the input push rod through the blind hole, and the coupling of the braking force of the driver and the assistance of the motor is completed on the feedback disc; the output push rod is connected with a first piston in a brake master cylinder and used for outputting a brake coupling force, a displacement difference sensor is arranged between the input push rod and the power-assisted valve body and used for measuring a displacement difference value between the input push rod and the power-assisted valve body and used as the input of a permanent magnet synchronous motor, the permanent magnet synchronous motor is connected with an electric control unit and acts under the instruction of the electric control unit, a primary gear speed reducing mechanism, a secondary gear speed reducing mechanism and a ball screw speed reducing mechanism form a tertiary speed reducing mechanism, the permanent magnet synchronous motor is connected with the tertiary speed reducing mechanism and drives the tertiary speed reducing mechanism to work, a spring is arranged between the input push rod and the power-assisted valve body and used for releasing the return of the input push rod after braking, the displacement difference sensor and the electric control unit are connected with a data acquisition and control system, and the electric control unit is controlled to work by the data acquisition and control system.

The brake master cylinder comprises a cylinder body, a first piston, a first working cavity, a first return spring, a second piston, a second working cavity and a second return spring, wherein the inner cavity of the cylinder body is sequentially provided with the first piston and the second piston from right to left, the first return spring is arranged between the first piston and the second piston, the first working cavity is formed between the first piston and the second piston, the second return spring is arranged between the second piston and the inner bottom of the cylinder body, the second working cavity is formed between the second piston and the inner bottom of the cylinder body, and brake fluid is filled in the first working cavity and the second working cavity.

The steer-by-wire system comprises a steering wheel, a road sensing motor, a first reducing mechanism, a first steer electric control unit, a first steer power-assisted motor, a second steer electric control unit, a second steer power-assisted motor, a second reducing mechanism, a steering gear, a steering rack and a steer load simulation spring, wherein the steering wheel is connected with one end of the first reducing mechanism through a steer input shaft, a torque angle sensor is assembled on the steer input shaft, the other end of the first reducing mechanism is connected with the road sensing motor, one end of the second reducing mechanism is connected with the tail end of the steer input shaft, a first electromagnetic clutch is assembled on the steer input shaft between the first reducing mechanism and the second reducing mechanism, the second reducing mechanism is respectively connected with a steer output shaft and a second electromagnetic clutch, a torque coupler is further connected on the second electromagnetic clutch, and the tail end of the steer output shaft is connected with the steering gear, the steering gear is meshed with a steering rack, two ends of the steering rack are connected with a steering load simulation spring, a first steering electric control unit is connected with a first steering power-assisted motor through a circuit, a second steering electric control unit is connected with a second steering power-assisted motor through a circuit, the first steering power-assisted motor and the second steering power-assisted motor are both connected with a torque coupler, a torque angle sensor and a road sensing motor are both connected with the first steering electric control unit and the second steering electric control unit through circuits, the first steering electric control unit and the second steering electric control unit jointly receive signals collected by the torque angle sensor and current and rotor position feedback signals of the road sensing motor, the first steering electric control unit and the second steering electric control unit cooperatively control the work of a first electromagnetic clutch, a second electromagnetic clutch and the road sensing motor, and the first steering electric control unit receives current and rotor position feedback signals of the first steering power-assisted motor and controls the first steering power-assisted motor Movement of the machine; the second steering electric control unit receives the current of the second steering power-assisted motor and the rotor position feedback signal and controls the motion of the second steering power-assisted motor; the output torque of the first steering power-assisted motor and the output torque of the second steering power-assisted motor are output to the second speed reducing mechanism after the action of the torque coupler, the first steering electronic control unit and the second steering electronic control unit are both connected with the data acquisition and control system, the first steering electronic control unit and the second steering electronic control unit are controlled by the data acquisition and control system to work, and the first steering electronic control unit and the second steering electronic control unit are connected through a CAN bus to realize communication.

The driver assembled in the electric cylinder selects an S700 driver of Kollmorgen company, closed-loop control of displacement of the electric cylinder CAN be realized through CAN communication, and the speed and acceleration of the movement of the electric cylinder CAN be accurately controlled.

The data acquisition and control system comprises a controller, vehicle dynamics simulation software and a simulation test environment, wherein the controller is a SCALEXIO system of dSPACE company and is used for hardware-in-loop and rapid control prototype application, the controller provides an IO (input output) interface for realizing signal interaction between a simulation model and an ECU (electronic control unit) entity, a power supply module is provided for supplying power to the ECU, and an electrical error simulation port is assembled in the controller and can access a fault insertion unit to simulate errors in ECU wiring; the vehicle dynamics simulation software comprises Matlab/Simulink and CarSim, the CarSim provides a complete vehicle dynamics model, the Simulink can be used for building a dynamics model as required, a simulation test environment is configured in the CarSim as required and comprises road conditions, weather, signal lamps and buildings, dSPACE, Matlab/Simulink and CarSim software are installed in an upper computer, a test model is built in the upper computer, a software and hardware interface is configured in a configuration desk, then the model is compiled, downloaded and linked to generate a target file and an executable file format of the dSPACE, a controller in the data acquisition and control system receives an executable file transmitted by the upper computer, and simultaneously transmits acquired signals and internal parameter signals to the upper computer, and the upper computer detects and modifies an operation result of the model in a test platform and related parameters of the model through a ControlDesk.

The power supply system comprises a programmable power supply, a 380V alternating current and a storage battery, wherein the programmable power supply supplies power to the hydraulic braking unit, the first steering electric control unit and the second steering electric control unit; 380V alternating current is used for supplying power to the electric cylinder; the voltage of the storage battery is 12V, and the storage battery supplies power for the electric control unit and the driving robot.

The working principle of the invention is as follows:

the working principle of each part of the integrated test bench for the vehicle braking and steering system provided by the invention is as follows:

the working process of the brake-by-wire system is as follows: an electronic booster in the brake-by-wire system recognizes the braking intention of a driver or an upper controller, and as a power source, builds pressure in a brake master cylinder, and hydraulic oil of the brake master cylinder flows into a brake wheel cylinder after being regulated by a Hydraulic Control Unit (HCU) to finally generate wheel braking force. In addition, the brake-by-wire system is one of the main tested objects of the test experiment table, and is also an actuator for longitudinal control in the development of a chassis transverse and longitudinal coordinated control strategy. When a driver steps on a brake pedal or an electric cylinder pushes an input push rod, the input push rod generates displacement, after a displacement difference value acquired by a displacement difference sensor changes, an electric control unit judges the braking intention of the driver according to the displacement difference value, and then a motor control algorithm decides a motion instruction of the permanent magnet synchronous motor to control the permanent magnet synchronous motor to move. The power-assisted valve body is driven to move under the action of the primary gear reduction mechanism, the secondary gear reduction mechanism and the ball screw reduction mechanism, and finally the output torque of the permanent magnet synchronous motor is transmitted to the outer ring of the feedback disc; meanwhile, the input push rod directly acts on the inner ring of the feedback disc. The motor force is coupled with the manpower or the thrust of the electric cylinder on the feedback disc and finally acts on the output push rod to be transmitted to the first piston in the brake master cylinder, and the establishment of the brake hydraulic pressure is completed.

The working process of the steer-by-wire system is as follows: the steering electronic control unit identifies the steering intention of a driver/a driving robot or an upper controller, controls the steering power-assisted motor to realize power-assisted steering, controls the road feel motor to generate proper steering hand feel, and simultaneously controls the first electromagnetic clutch to be disconnected and the second electromagnetic clutch to be connected, so that the steering wheel finally reaches the expected wheel turning angle. Because the steering electronic control unit and the power-assisted motor of the steer-by-wire system adopt a redundant backup framework, only the first steering electronic control unit and the first steering power-assisted motor work under normal conditions, and when the first steering electronic control unit or the first steering power-assisted motor breaks down, the second steering electronic control unit and the second steering power-assisted motor start to work, so that the vehicle is ensured not to lose the steering capacity.

The specific process of the control signal sent by the controller in the data acquisition and control system is as follows: the control signals sent to the electric cylinder by the controller comprise a target displacement signal, a target displacement speed signal and a target displacement acceleration signal; the control signals sent to the driving robot by the controller comprise a target torque signal, a target torque change rate signal, a target corner signal and a target corner rate signal; the control signal sent to the electronic booster by the controller comprises an enabling signal; the control signals sent by the controller to a Hydraulic Control Unit (HCU) comprise an enabling signal, a KL15 signal, a wheel speed signal, a gear signal, a target master cylinder pressure signal and the like; the signals sent by the controller to the first steering electronic control unit and the second steering electronic control unit comprise enabling signals, KL15 signals, wheel speed signals, gear signals, target steering wheel rotation angles or torque signals and the like.

The invention provides a vehicle chassis brake and steering system integrated test bench, which comprises the following conventional test procedures:

1) designing a test scheme: according to the test target, designing a corresponding test scheme, exploring a test method, establishing an evaluation index and editing a test case.

2) Test preparation: based on Matlab/Simulink and Carsim software, a dynamic model required by testing is built, a software and hardware interface is configured in configuration desk software, then the model is compiled to generate an executable file, and then the executable file is downloaded to a controller.

3) Test experiments were carried out: and supplying power to the brake-by-wire system, the steering-by-wire system, the electric cylinder and the driving robot, and testing according to the test case after the system works normally.

4) And (3) analyzing a test result: and acquiring test data during testing, analyzing the data, and analyzing the result according to the previously established evaluation index.

5) And (3) test item improvement and optimization: and (4) according to the analysis of the test result, improving and optimizing the whole test item, and retesting under necessary conditions.

The invention has the beneficial effects that:

the integrated test stand for the vehicle braking and steering system provided by the invention realizes the hardware-in-loop of multiple physical systems of the brake-by-wire system and the steer-by-wire system, can quickly and comprehensively test the performance of the braking and steering system under the function interaction of the chassis, has more accurate off-line simulation result, and saves more time and cost compared with a real vehicle test. The electric cylinder and the driving robot are respectively used as loading devices of the braking system and the steering system, requirements of relevant regulatory standards can be matched, and dynamic and standardized tests under the braking and steering integrated system are completed. The test bed for the vehicle braking and steering system integration test provided by the invention has good portability, can simulate braking and steering performances under different vehicle types and different road surface conditions by simply modifying vehicle parameters and road environment parameters in CarSim, and can also quickly test the performances of braking systems and steering systems of other hardware in a ring. The performance of a single braking system or a steering system and the performance of a braking and steering integrated system can be tested, and the test platform can be used as a hardware-in-loop platform for verifying a chassis transverse and longitudinal coordinated control strategy. Not only can the conventional performance test of the system be realized, but also the fault injection test can be realized by means of an electrical error simulation port (EESPort) in SCALEXIO.

Drawings

Fig. 1 is a schematic structural diagram of the principle of the integrated test stand according to the present invention.

Fig. 2 is a schematic structural diagram of an electronic booster according to the present invention.

Fig. 3 is an isometric view of a connection plate according to the present invention.

Fig. 4 is a schematic structural diagram of a brake master cylinder according to the present invention.

FIG. 5 is a schematic diagram of a conventional testing process of the integrated testing stand according to the present invention.

FIG. 6 is a schematic diagram of the steering wheel angle input of the sine hysteresis test of the steering wheel of the integrated test bench according to the present invention.

FIG. 7 is a flow chart of the integrated test bench fault injection test according to the present invention.

Fig. 8 is a schematic diagram of a lateral and longitudinal coordination control strategy of the integrated test bed according to the present invention.

The labels in the above figures are as follows:

1. brake-by-wire system 2, steer-by-wire system 3, electric cylinder 4, and driving robot

5. Data acquisition and control system 6, host computer 7, power supply system 8, input push rod

9. Steering wheel 10, electronic booster 11, brake master cylinder 12, stock solution kettle

13. Hydraulic control unit 14, brake wheel cylinder 15, first piston

16. Pedal force sensor 17, pedal stroke sensor 18, first hydraulic pressure sensor

19. Second hydraulic pressure sensor 20, third hydraulic pressure sensor 21, fourth hydraulic pressure sensor

22. Fifth hydraulic pressure sensor 23, sixth hydraulic pressure sensor 24, electronic control unit

25. Permanent magnet synchronous motor 26, primary gear reduction mechanism 27 and secondary gear reduction mechanism

28. Ball screw speed reducing mechanism 29, power-assisted valve body 30 and displacement difference sensor

31. Spring 32, feedback disc 33, output push rod 34 and connecting plate

35. Cylinder 36, first working chamber 37, first return spring 38, second piston

39. A second working chamber 40, a second return spring 41, a road sensing motor 42, and a first speed reducing mechanism

43. A first steering electronic control unit 44, a first steering power-assisted motor 45, and a second steering electronic control unit

46. A second power steering motor 47, a second reduction gear 48, and a steering gear

49. Steering rack 50, steering load simulation spring 51, and steering input shaft

52. Torque angle sensor 53, first electromagnetic clutch 54, and steering output shaft

55. Second electromagnetic clutch 56, torque coupler 57, controller

58. Vehicle dynamics simulation software 59, simulation test environment 60, programmable power supply

61. 380V alternating current 62 and a storage battery.

Detailed Description

Please refer to fig. 1 to 8:

the invention provides a vehicle brake and steering system integrated test bench which comprises a brake-by-wire system 1, a steering-by-wire system 2, an electric cylinder 3, a driving robot 4, a data acquisition and control system 5, an upper computer 6 and a power supply system 7, wherein the electric cylinder 3 is connected with the brake-by-wire system 1 through an input push rod 8, the driving robot 4 is connected with a steering wheel 9 in the steering-by-wire system 2, the data acquisition and control system 5 is respectively in circuit connection with the brake-by-wire system 1, the electric cylinder 3, the steering-by-wire system 2 and the driving robot 4, the data acquisition and control system 5 respectively acquires sensor signals inside the brake-by-wire system 1, the electric cylinder 3, the steering-by-wire system 2 and the driving robot 4 through a signal acquisition circuit and sends control signals to ECUs in the brake-by-wire system 1, the electric cylinder 3, the steering-by-wire system 2 and the driving robot 4 through a driving circuit, the data acquisition and control system 5 controls the work of the brake-by-wire system 1, the electric cylinder 3, the steer-by-wire system 2 and the driving robot 4, the power supply system 7 is respectively connected with the brake-by-wire system 1, the electric cylinder 3, the steer-by-wire system 2 and the driving robot 4, the power supply system 7 respectively provides electric power for the brake-by-wire system 1, the electric cylinder 3, the steer-by-wire system 2 and the driving robot 4, the upper computer 6 is connected with the data acquisition and control system 5 through an Internet network cable, and signal acquisition and control signal sending are achieved.

The brake-by-wire system 1 comprises an electronic booster 10, a brake master cylinder 11, a liquid storage pot 12, a hydraulic control unit 13 and a brake wheel cylinder 14, wherein the input end of the electronic booster 10 is connected with the electric cylinder 3 through an input push rod 8, the output end of the electronic booster 10 is connected with a first piston 15 in the brake master cylinder 11, the liquid storage pot 12 is communicated with the brake master cylinder 11 through two liquid conveying pipelines, the brake master cylinder 11 is communicated with the hydraulic control unit 13 through two pipelines, the hydraulic control unit 13 is communicated with the brake wheel cylinder 14 through four pipelines, hydraulic oil flows out from two liquid outlets of the liquid storage pot 12 and flows in from two liquid inlets of the brake master cylinder 11, the hydraulic oil flows into the hydraulic control unit 13 through two liquid outlets after the brake master cylinder 11 is pressurized, the hydraulic oil flows into the brake wheel cylinder 14 after the regulation effect of the hydraulic control unit 13, and the hydraulic pressure in the brake wheel cylinder 14 is converted into wheel braking force, an input push rod 8 connected between the electronic booster 10 and the electric cylinder 3 is provided with a pedal force sensor 16 and a pedal stroke sensor 17, and two pipelines communicated between the brake master cylinder 11 and the hydraulic control unit 13 are respectively provided with a first hydraulic pressure sensor 18 and a second hydraulic pressure sensor 19; a third hydraulic pressure sensor 20, a fourth hydraulic pressure sensor 21, a fifth hydraulic pressure sensor 22 and a sixth hydraulic pressure sensor 23 are respectively assembled on four communicating pipelines between the hydraulic control unit 13 and the brake wheel cylinder 14, the electronic booster 10, the hydraulic control unit 13, the pedal force sensor 16, the pedal stroke sensor 17, the first hydraulic pressure sensor 18, the second hydraulic pressure sensor 19, the third hydraulic pressure sensor 20, the fourth hydraulic pressure sensor 21, the fifth hydraulic pressure sensor 22 and the sixth hydraulic pressure sensor 23 are all connected with the data acquisition and control system 5, the pedal force sensor 16, the pedal stroke sensor 17, the first hydraulic pressure sensor 18, the second hydraulic pressure sensor 19, the third hydraulic pressure sensor 20, the fourth hydraulic pressure sensor 21, the fifth hydraulic pressure sensor 22 and the sixth hydraulic pressure sensor 23 can transmit the acquired data to the data acquisition and control system 5 in real time, the data acquisition and control system 5 controls the work of the electronic booster 10 and the hydraulic control unit 13, and the electronic booster 10 is connected with the hydraulic control unit 13 through a CAN bus to realize communication.

The electronic booster 10 comprises an electric control unit 24, a permanent magnet synchronous motor 25, a primary gear reduction mechanism 26, a secondary gear reduction mechanism 27, a ball screw reduction mechanism 28, a boosting valve body 29, a displacement difference sensor 30, an input push rod 8, a spring 31, a feedback disc 32, an output push rod 33 and a connecting plate 34, wherein the input push rod 8, the feedback disc 32 and the output push rod 33 are vacuum boosters, and the input push rod 8 is connected with the electric cylinder 3 through the connecting plate 34 for inputting braking force; the connecting plate 34 is in a stepped cylindrical shape, a threaded hole is processed at one end along the axis of the connecting plate 34, and the connecting plate 34 is in transition fit with the output shaft of the electric cylinder 3 through the threaded hole; a blind hole is processed along the other end of the axis of the connecting plate 34, the connecting plate 34 is in transition fit with the input push rod 8 through the blind hole, and the feedback disc 32 completes the coupling of the braking force of a driver and the assistance of a motor; the output push rod 33 is connected with the first piston 15 in the master cylinder 11 for outputting the brake coupling force, the displacement difference sensor 30 is arranged between the input push rod 8 and the booster valve body 29 for measuring the displacement difference between the input push rod 8 and the booster valve body 29, the permanent magnet synchronous motor 25 is connected with the electric control unit 24 and acts under the instruction of the electric control unit 24, the primary gear reduction mechanism 26, the secondary gear reduction mechanism 27 and the ball screw reduction mechanism 28 form a three-stage reduction mechanism, the permanent magnet synchronous motor 25 is connected with the three-stage reduction mechanism and drives the three-stage reduction mechanism to work, a spring 31 is arranged between the input push rod 8 and the power-assisted valve body 29 and used for releasing the return of the input push rod 8 after braking, the displacement difference sensor 30 and the electric control unit 24 are connected with the data acquisition and control system 5, and the electric control unit 24 is controlled by the data acquisition and control system 5 to work.

The master cylinder 11 includes a cylinder body 35, a first piston 15, a first working chamber 36, a first return spring 37, a second piston 38, a second working chamber 39, and a second return spring 40, wherein the first piston 15 and the second piston 38 are sequentially assembled in an inner cavity of the cylinder body 35 from right to left, the first return spring 37 is disposed between the first piston 15 and the second piston 38, the first working chamber 36 is formed between the first piston 15 and the second piston 38, the second return spring 40 is disposed between the second piston 38 and an inner bottom of the cylinder body 35, the second working chamber 39 is formed between the second piston 38 and the inner bottom of the cylinder body 35, and the first working chamber 36 and the second working chamber 39 are filled with brake fluid.

The steer-by-wire system 2 comprises a steering wheel 9, a road sensing motor 41, a first speed reducing mechanism 42, a first steering electronic control unit 43, a first steering power-assisted motor 44, a second steering electronic control unit 45, a second steering power-assisted motor 46, a second speed reducing mechanism 47, a steering gear 48, a steering rack 49 and a steering load simulation spring 50, wherein the steering wheel 9 is connected with one end of the first speed reducing mechanism 42 through a steering input shaft 51, a torque angle sensor 52 is assembled on the steering input shaft 51, the other end of the first speed reducing mechanism 42 is connected with the road sensing motor 41, one end of the second speed reducing mechanism 47 is connected with the tail end of the steering input shaft 51, a first electromagnetic clutch 53 is assembled on the steering input shaft 51 between the first speed reducing mechanism 42 and the second speed reducing mechanism 47, the second speed reducing mechanism 47 is also connected with a steering output shaft 54 and a second electromagnetic clutch 55 respectively, the second electromagnetic clutch 55 is further connected with a torque coupler 56, the tail end of the steering output shaft 54 is connected with the steering gear 48, the steering gear 48 is engaged with the steering rack 49, two ends of the steering rack 49 are connected with the steering load simulation spring 50, the first steering electric control unit 43 is connected with the first steering power-assisted motor 44 through a circuit, the second steering electric control unit 45 is connected with the second steering power-assisted motor 46 through a circuit, the first steering power-assisted motor and the second steering power-assisted motor 46 are both connected with the torque coupler 56, the torque angle sensor 52 and the road sensor motor 41 are both connected with the first steering electric control unit 43 and the second steering electric control unit 45 through a circuit, the first steering electric control unit 43 and the second steering electric control unit 45 jointly receive signals collected by the torque angle sensor 52 and current and rotor position feedback signals of the road sensor motor 41, the first steering electronic control unit 43 and the second steering electronic control unit 45 cooperatively control the operation of the first electromagnetic clutch 53, the second electromagnetic clutch 55 and the road sensing motor 41, and the first steering electronic control unit 43 receives the current of the first steering power-assisted motor 44 and the rotor position feedback signal and controls the movement of the first steering power-assisted motor 44; the second steering electronic control unit 45 receives the current of the second steering power-assisted motor 46 and the rotor position feedback signal and controls the motion of the second steering power-assisted motor 46; the output torque of the first steering assisting motor 44 and the output torque of the second steering assisting motor 46 are output to the second speed reducing mechanism 47 under the action of the torque coupler 56, the first steering electronic control unit 43 and the second steering electronic control unit 45 are both connected with the data acquisition and control system 5, the first steering electronic control unit 43 and the second steering electronic control unit 45 are controlled by the data acquisition and control system 5 to work, and the first steering electronic control unit 43 and the second steering electronic control unit 45 are connected through a CAN bus to realize communication.

The S700 driver of Kollmorgen company is selected as the driver assembled in the electric cylinder 3, the closed-loop control of the displacement of the electric cylinder CAN be realized through CAN communication, and the speed and the acceleration of the movement of the electric cylinder 3 CAN be accurately controlled.

The data acquisition and control system 5 comprises a controller 57, vehicle dynamics simulation software 58 and a simulation test environment 59, wherein the controller 57 is a SCALEXIO system of dSPACE company and is used for hardware-in-loop and rapid control prototype application, the controller 57 provides an IO interface for realizing signal interaction between a simulation model and an ECU real object, a power supply module is provided for supplying power to the ECU, and an electrical error simulation port is assembled in the controller 57 and can access a fault insertion unit to simulate errors in ECU wiring; the vehicle dynamics simulation software 58 comprises Matlab/Simulink and CarSim, the CarSim provides a complete vehicle dynamics model, the Simulink can be used for building a dynamics model as required, a simulation test environment 59 is configured in the CarSim as required and comprises road conditions, weather, signal lamps and buildings, dSPACE, Matlab/Simulink and CarSim software are installed in the upper computer 6, a test model is built in the upper computer 6, a software and hardware interface is configured in a configuration desk, then the model is compiled, downloaded and linked to generate a target file and an executable file format of dSPACE, a controller 57 in the data acquisition and control system 5 receives the executable file transmitted by the upper computer 6, and simultaneously transmits the acquired signal and an internal parameter signal to the upper computer 6, and the upper computer 6 detects and modifies the operation result of the model in the test platform and related parameters of the model through a control desk.

The power supply system 7 comprises a programmable power supply 60, 380V alternating current 61 and a storage battery 62, wherein the programmable power supply 60 supplies power to the hydraulic control unit 13, the first steering electronic control unit 43 and the second steering electronic control unit 45; 380V alternating current 61 supplies power for the electric cylinder 3; the voltage of the battery 62 is 12V, and the battery 62 supplies power to the electronic control unit 24 and the robot 4.

The working principle of the invention is as follows:

the working process of the brake-by-wire system 1 is as follows: the electronic booster 10 in the brake-by-wire system 1 recognizes the braking intention of the driver or the upper controller, and builds up pressure in the brake master cylinder 11 as a power source, and the hydraulic oil of the brake master cylinder 11 flows into the brake wheel cylinders 14 after being regulated by the hydraulic control unit 11(HCU) to finally generate wheel braking force. In addition, the brake-by-wire system 1 is one of the main objects to be tested of the test bench, and is also an actuator for longitudinal control in the development of a chassis transverse and longitudinal coordinated control strategy. When a driver steps on a brake pedal or the electric cylinder 3 pushes the input push rod 8, the input push rod 8 generates displacement, and after a displacement difference value acquired by the displacement difference sensor 30 changes, the electric control unit 24 judges the braking intention of the driver according to the displacement difference value, and then a motor control algorithm decides a motion instruction of the permanent magnet synchronous motor 25 to control the permanent magnet synchronous motor 25 to move. The power-assisted valve body 29 is driven to move under the action of the primary gear reduction mechanism 26, the secondary gear reduction mechanism 27 and the ball screw reduction mechanism 28, and finally the output torque of the permanent magnet synchronous motor 25 is transmitted to the outer ring of the feedback disc 32; at the same time, the input push rod 8 acts directly on the inner ring of the feedback disk 32. The motor force is coupled with the manpower or the thrust of the electric cylinder 3 on the feedback disc 32 and finally acts on the output push rod 33 to be transmitted to the first piston 15 in the brake master cylinder 11, and the establishment of the brake hydraulic pressure is completed.

The working process of the steer-by-wire system 2 is as follows: the steering electronic control unit recognizes the steering intention of a driver/a driving robot or an upper controller, controls the steering power-assisted motor to realize power-assisted steering, controls the road feel motor 41 to generate proper steering hand feel, and simultaneously controls the first electromagnetic clutch 53 to be disconnected and the second electromagnetic clutch 55 to be connected, so that the steering wheel finally reaches the expected wheel turning angle. Because the electric steering unit and the power-assisted motor of the steer-by-wire system 2 adopt a redundant backup architecture, only the first electric steering unit 43 and the first power-assisted steering motor 44 work under normal conditions, and when the first electric steering unit 43 or the first power-assisted steering motor 44 fails, the second electric steering unit 45 and the second power-assisted steering motor 46 start to work, so that the vehicle is ensured not to lose the steering capacity.

The specific process of the control signal sent by the controller 57 in the data acquisition and control system 5 is as follows: the control signals sent to the electric cylinder 3 by the controller 57 include a target displacement signal, a target displacement speed signal and a target displacement acceleration signal; the control signals sent by the controller 57 to the robot 4 include a target torque signal, a target torque change rate signal, a target rotation angle signal, and a target rotation angle rate signal; the control signals sent by controller 57 to electronic booster 10 include an enable signal; the control signals sent by the controller 57 to the hydraulic control unit 13(HCU) include an enable signal, a KL15 signal, a wheel speed signal, a gear signal, a target master cylinder pressure signal, etc.; the signals sent by the controller 57 to the first steering electronic control unit 43 and the second steering electronic control unit 45 include an enable signal, a KL15 signal, a wheel speed signal, a gear signal, a target steering wheel angle or torque signal, and the like.

2) Preparation of a test: based on Matlab/Simulink and Carsim software, a dynamic model required by testing is built, a software and hardware interface is configured in configuration desk software, then the model is compiled to generate an executable file, and then the executable file is downloaded to a controller.

3) Test experiments were carried out: and supplying power to the brake-by-wire system 1, the steering-by-wire system 2, the electric cylinder 3 and the driving robot 4, and testing according to the test case after ensuring the normal work of the system.

Following the test flow described in fig. 5, a test for the stability characteristics of the integrated brake and steering system is described in detail herein. The test method for stability control characteristic test mainly comprises a double-shift line test, a sine hysteresis test, an obstacle avoidance test and the like. The sine hysteresis test specified by the FMVSS No.126 standard is selected for description herein:

the method comprises the following steps: checking relevant regulation standards of reading and operating stability characteristic test, particularly FMVSS No.126 standard, designing a complete set of test scheme, establishing evaluation indexes, and editing test cases. The evaluation index here indicates the following two: in the sine hysteresis test, the yaw velocity corresponding to 1 second after the steering input of the steering wheel is finished should not exceed 35% of the peak value of the yaw velocity in the delay period of the same test cycle; the yaw rate corresponding to 1.75 seconds after the steering input to the steering wheel is ended in the sinusoidal hysteresis test should not exceed 20% of the peak value of the yaw rate during the delay period of the same test cycle. The corresponding two equations are as follows:

in the formula (I), the compound is shown in the specification,

is the vehicle yaw rate at a particular time in the sinusoidal hysteresis test,

for vehicle peak yaw rate in sinusoidal hysteresis test: t is t₀The time at which the steering wheel angle starts to be input in the sinusoidal hysteresis test.

The variables of the test case are mainly vehicle speed, steering wheel angle input and road adhesion coefficient, where vehicle speed and road adhesion coefficient are fixed, only steering wheel angle input is changed, and some tests are listed in table 1, for example. The final test case is generated by arranging and combining the vehicle speed, the steering wheel angle input, the road surface adhesion system, and the like. The "A" value here refers to the steering wheel angle at which the vehicle is caused to produce a steady lateral acceleration of 0.3 g.

TABLE 1 partial test case for sinusoidal hysteresis test of steering wheel

Step two: corresponding dynamic models and simulation test environments 59 are built based on Matlab/Simulink and CarSim, and after an interface is configured in configuration desk software, the models are compiled and downloaded to the controller 57.

Step three: after the brake-by-wire system 1, the steering-by-wire system 2 and the driving robot 4 are powered, and the normal work of the system is ensured, the upper computer 6 sends signals such as real-time vehicle speed, wheel speed, gear, KL15 and the like output by Carsim and signals such as steering wheel angle, steering angle change rate and the like received from the steering-by-wire system 2 to the steering-by-wire system 1 through the controller 57; the upper computer 6 sends signals such as real-time vehicle speed, wheel speed, gear, KL15 and the like output by the CarSim to the linear control steering system 2 through the controller 57; the upper computer 6 sends control signals such as an expected steering wheel angle and an expected steering angle change rate to the driving robot 4 through the controller 57.

The test preparation phase is mainly to determine the amplitude "a" by a slow steering wheel angle increase test. The test was performed twice, once with a clockwise rotation of the steering wheel and once with a counter-clockwise rotation of the steering wheel, each repetition 3 times. The vehicle speed in the model was set to (80 ± 2) km/h, the steering wheel angle was slowly increased by the steering robot 4 at a speed of 13.5 °/s until the lateral acceleration of the vehicle reached 0.5g, and from this test the amplitude "a" was determined, which was the steering wheel angle at which the vehicle produced a steady 0.3g lateral acceleration. "A" is the average of 6 trials and is rounded to 0.1.

Referring to fig. 6, when the test is performed, the vehicle speed in the model is set to (80 ± 2) km/h, the steering robot 4 is controlled to input the steering wheel angle in a sine of 0.7Hz, a delay of 500ms is made at the second peak, the steering wheel initial angle is 1.5A, and then the steering wheel initial angle is gradually increased by 0.5A until the steering wheel angle reaches 6.5A or 270 °, if 6.5A >300 °, the steering wheel maximum amplitude is 300 °.

Step four: and acquiring a yaw rate signal of a hydraulic control unit 13(HCU) in the brake-by-wire system 1 in real time in a test, analyzing and processing data, and analyzing a result according to the evaluation index provided in the first step.

Step five: and analyzing according to the result of the step four, evaluating whether the test item can meet the test requirement of the stability operating characteristic, improving and optimizing the whole test item, and redesigning the test scheme for testing if necessary.

In addition, according to the test flow illustrated in fig. 5, a test flow for performing a Hill Descent Control (HDC) function based on the integrated test bench for the braking and steering system is described as follows:

the method comprises the following steps: the steep descent function can realize that the vehicle automatically brakes and smoothly passes through a downhill section under the condition that a driver does not step on a brake pedal during downhill driving. The starting of the steep descent function requires three conditions to be met: the speed of the vehicle is 2km/h-35km/h, the steep slope is continuous and above 8 degrees, and the steep slope section is continuous and has a certain length. According to the function description of the steep descent, whether the steep descent function is available or not and the vehicle speed control performance after the steep descent is started are used as two evaluation indexes. The variables of the test case for the steep descent function include vehicle speed and road gradient, and if the road gradient is ensured to be unchanged, part of the test cases under the typical vehicle speed are shown in table 2.

TABLE 2 test case for steep descent function part

Step two: the method comprises the steps of building a road model in CarSim, setting the gradient of the road model to be 10 degrees, setting a vehicle to pass through the road surface at a certain speed, building a corresponding model in Simulink, configuring an interface in configuration desk software, compiling the model and downloading the model to a controller 57, wherein the front section of the road model is a flat straight road, and the rear section of the road model is a continuous downhill road section with a certain length.

Step three: and supplying power to the system, running the whole test program after ensuring the normal work of the system, and opening the steep descent control function switch to observe the motion state of the vehicle when the vehicle to be detected just drives into the downhill section.

Step four: and (3) acquiring signals of four wheel cylinder pressure sensors in the brake-by-wire system 1, a vehicle speed signal in a CAN bus and a steep descent working state signal in real time in a test, and analyzing and evaluating the acquired signals according to the evaluation index provided in the step one.

Step five: and analyzing according to the result of the step four, evaluating whether the test item can meet the test requirement of the ramp auxiliary function, improving and optimizing the whole test item, and redesigning the test scheme to test if necessary.

Referring to fig. 7, the vehicle chassis braking and steering system integrated test bench provided by the invention can also perform fault injection test, and the fault injection test flow is as follows:

1) an electrical error simulation port (EESPort) profile is generated. The EESPort profile contains a path for a list of simulator signals that provides information about available signals and potentials and may also specify mapping information for potentials and signals.

2) The type of error is specified in the configuration file. The types of errors that may be specified here include: open circuits (broken wires, loose contacts) and short circuits (short to ground, short to power supply, short to signal measurement channel, etc.).

3) And downloading the set configuration file to hardware and activating.

4) And triggering simulation in ControlDesk software to perform fault injection test.

Referring to fig. 8, the vehicle chassis braking and steering system integrated test bench provided by the invention can also verify the chassis transverse and longitudinal coordination control strategy, and the process is as follows:

the method comprises the following steps: a chassis transverse and longitudinal coordination control strategy as shown in FIG. 8 is built, and mainly comprises an input module, key state parameter estimation, vehicle motion control, actuator control and controlled vehicles. First, the expected acceleration, yaw rate and centroid slip angle are estimated according to the road adhesion coefficient, gradient, steering wheel angle, accelerator/brake pedal opening, and vehicle state of the input module. And then, based on feedforward and PI feedback control of a vehicle dynamics inverse model, the expected generalized force of the whole vehicle is obtained by solving state parameters of the vehicle. And then, based on the control distribution layer design of kinematics, the expected generalized force of the whole vehicle is optimally divided into corresponding longitudinal force and lateral force of the vehicle under the condition of meeting the given control target and performance criterion. And converting the longitudinal force and the lateral force of the vehicle into expected driving torque/brake master cylinder pressure and front wheel rotation angle at an actuator control layer, sending signals to corresponding actuators, and inputting the actual driving torque/master cylinder pressure and front wheel rotation angle of the actuators into a controlled vehicle of CarSim to realize the transverse and longitudinal coordinated control of the chassis.

The control strategy shown in fig. 8 is to improve the yaw stability of the vehicle, so the vehicle lateral displacement deviation, the centroid side deviation angle and the yaw velocity are selected as evaluation indexes, and the control effects of the control strategy of the CarSim self and the control strategy of the invention shown in fig. 8 in the transverse and longitudinal directions are compared.

Step two: selecting an open-loop sine hysteresis test working condition and a closed-loop double-shift-line test working condition as two verified working conditions, building a simulation model corresponding to the graph 8 based on Simulnk and CarSim, and building a road model corresponding to the simulation working condition in the CarSim. The method comprises the steps of transmitting the whole vehicle state information in a chassis brake and steering system integrated test bench to a simulation model through CAN messages, respectively sending a control target (expected brake master cylinder pressure and front wheel rotation angle) finally decided by the simulation model to a hydraulic control unit 13 of a brake-by-wire system 1 and a steering electric control unit of a steering-by-wire system 2 through the CAN messages, and simultaneously acquiring the actual brake master cylinder pressure and front wheel rotation angle signals of an actuator in real time to send an input interface of CarSim. Because the test bed does not comprise a driving system, the simulation model comprises the modeling of the driving system, and the driving torque finally decided by the simulation model is directly sent to an input interface of the CarSim. After configuring the interface in the configuration desk software according to the above description of the transfer signal, the model is compiled and downloaded to the controller 57.

Step three: and supplying power to the system, running the whole test program and observing the motion state of the vehicle after ensuring the normal work of the system.

Step four: in the test, two main cylinder pressure sensor signals in the brake-by-wire system 1, a steering wheel turning angle signal in the CAN bus, a yaw rate signal, a vehicle speed signal and the like are collected in real time, and then the collected signals are analyzed and evaluated according to the evaluation index provided in the first step.

Step five: and analyzing according to the result of the fourth step, evaluating the performance of the chassis transverse and longitudinal coordination control strategy shown in the figure 8, improving and optimizing the defects of the algorithm, and redesigning a test scheme for testing if necessary.

Claims

1. A vehicle braking and steering system integrated test bench comprises a wire-controlled braking system, a wire-controlled steering system, an electric cylinder, a driving robot, a data acquisition and control system, an upper computer and a power supply system, wherein the electric cylinder is connected with the wire-controlled braking system through an input push rod, the driving robot is connected with a steering wheel in the wire-controlled steering system, the data acquisition and control system is respectively in circuit connection with the wire-controlled braking system, the electric cylinder, the wire-controlled steering system and the driving robot, the data acquisition and control system respectively acquires sensor signals inside the wire-controlled braking system, the electric cylinder, the wire-controlled steering system and the driving robot through a signal acquisition circuit and sends control signals to ECU (electronic control Unit) in the wire-controlled braking system, the electric cylinder, the wire-controlled steering system and the driving robot through a driving circuit, and the data acquisition and control system controls the wire-controlled braking system, the upper computer and the power supply system, Electronic jar, steer-by-wire system and the work of driving the robot, power supply system is connected with drive-by-wire braking system, electronic jar, steer-by-wire system and driving the robot respectively and for drive-by-wire braking system, electronic jar, steer-by-wire system and driving the robot provide electric power, the host computer passes through Internet net twine and data acquisition and control system connection, realizes the collection of signal and control signal's transmission, its characterized in that: the brake-by-wire system comprises an electronic booster, a brake master cylinder, a liquid storage pot, a hydraulic control unit and a brake cylinder, wherein the input end of the electronic booster is connected with the electric cylinder through an input push rod, the output end of the electronic booster is connected with a first piston in the brake master cylinder, the liquid storage pot is communicated with the brake master cylinder through two liquid conveying pipelines, the brake master cylinder is communicated with the hydraulic control unit through two pipelines, the hydraulic control unit is communicated with the brake cylinder through four pipelines, hydraulic oil flows out of two liquid outlets of the liquid storage pot and flows into the brake master cylinder from two liquid inlets of the brake master cylinder, the hydraulic oil flows into the hydraulic control unit through the two liquid outlets after the pressure of the brake master cylinder is built up, the hydraulic oil flows into the brake cylinder after the regulation effect of the hydraulic control unit, the hydraulic pressure in the brake cylinder is converted into wheel braking force, a pedal force sensor and a pedal stroke sensor are arranged on the input push rod connected between the electronic booster and the electric cylinder, a first hydraulic pressure sensor and a second hydraulic pressure sensor are respectively assembled on two pipelines communicated between the brake master cylinder and the hydraulic control unit; the four communicating pipelines between the hydraulic control unit and the brake wheel cylinder are respectively provided with a third hydraulic pressure sensor, a fourth hydraulic pressure sensor, a fifth hydraulic pressure sensor and a sixth hydraulic pressure sensor, the electronic booster, the hydraulic control unit, the pedal force sensor, the pedal stroke sensor, the first hydraulic pressure sensor, the second hydraulic pressure sensor, the third hydraulic pressure sensor, the fourth hydraulic pressure sensor, the fifth hydraulic pressure sensor and the sixth hydraulic pressure sensor are all connected with a data acquisition and control system, the pedal force sensor, the pedal stroke sensor, the first hydraulic pressure sensor, the second hydraulic pressure sensor, the third hydraulic pressure sensor, the fourth hydraulic pressure sensor, the fifth hydraulic pressure sensor and the sixth hydraulic pressure sensor can transmit acquired data to the data acquisition and control system in real time, and the data acquisition and control system controls the work of the electronic booster and the hydraulic control unit, the electronic booster is connected with the hydraulic control unit through a CAN bus to realize communication; the electronic booster comprises an electric control unit, a permanent magnet synchronous motor, a primary gear speed reducing mechanism, a secondary gear speed reducing mechanism, a ball screw speed reducing mechanism, a boosting valve body, a displacement difference sensor, an input push rod, a spring, a feedback disc, an output push rod and a connecting plate, wherein the input push rod, the feedback disc and the output push rod are vacuum boosters, and the input push rod is connected with an electric cylinder through the connecting plate and used for inputting braking force; the connecting plate is in a stepped cylindrical shape, a threaded hole is processed at one end along the axis of the connecting plate, and the connecting plate is in transition fit with an output shaft of the electric cylinder through the threaded hole; a blind hole is processed along the other end of the axis of the connecting plate, the connecting plate is in transition fit with the input push rod through the blind hole, and the coupling of the braking force of the driver and the assistance of the motor is completed on the feedback disc; the output push rod is connected with a first piston in a brake master cylinder and used for outputting a brake coupling force, a displacement difference sensor is arranged between the input push rod and the power-assisted valve body and used for measuring a displacement difference value between the input push rod and the power-assisted valve body and used as the input of a permanent magnet synchronous motor, the permanent magnet synchronous motor is connected with an electric control unit and acts under the instruction of the electric control unit, a primary gear speed reducing mechanism, a secondary gear speed reducing mechanism and a ball screw speed reducing mechanism form a three-stage speed reducing mechanism, the permanent magnet synchronous motor is connected with the three-stage speed reducing mechanism and drives the three-stage speed reducing mechanism to work, a spring is arranged between the input push rod and the power-assisted valve body and used for releasing the return of the input push rod after braking, the displacement difference sensor and the electric control unit are connected with a data acquisition and control system, and the electric control unit is controlled to work by the data acquisition and control system; the steer-by-wire system comprises a steering wheel, a road sensing motor, a first reducing mechanism, a first steer electric control unit, a first steer power-assisted motor, a second steer electric control unit, a second steer power-assisted motor, a second reducing mechanism, a steering gear, a steering rack and a steer load simulation spring, wherein the steering wheel is connected with one end of the first reducing mechanism through a steer input shaft, a torque angle sensor is assembled on the steer input shaft, the other end of the first reducing mechanism is connected with the road sensing motor, one end of the second reducing mechanism is connected with the tail end of the steer input shaft, a first electromagnetic clutch is assembled on the steer input shaft between the first reducing mechanism and the second reducing mechanism, the second reducing mechanism is respectively connected with a steer output shaft and a second electromagnetic clutch, a torque coupler is further connected on the second electromagnetic clutch, and the tail end of the steer output shaft is connected with the steering gear, the steering gear is meshed with a steering rack, two ends of the steering rack are connected with a steering load simulation spring, a first steering electric control unit is connected with a first steering power-assisted motor through a circuit, a second steering electric control unit is connected with a second steering power-assisted motor through a circuit, the first steering power-assisted motor and the second steering power-assisted motor are both connected with a torque coupler, a torque angle sensor and a road sensing motor are both connected with the first steering electric control unit and the second steering electric control unit through circuits, the first steering electric control unit and the second steering electric control unit jointly receive signals collected by the torque angle sensor and current and rotor position feedback signals of the road sensing motor, the first steering electric control unit and the second steering electric control unit cooperatively control the work of a first electromagnetic clutch, a second electromagnetic clutch and the road sensing motor, and the first steering electric control unit receives current and rotor position feedback signals of the first steering power-assisted motor and controls the first steering power-assisted motor Movement of the machine; the second steering electric control unit receives the current of the second steering power-assisted motor and the rotor position feedback signal and controls the motion of the second steering power-assisted motor; the output torque of the first steering power-assisted motor and the output torque of the second steering power-assisted motor are output to the second speed reducing mechanism after the action of the torque coupler, the first steering electronic control unit and the second steering electronic control unit are both connected with the data acquisition and control system, the first steering electronic control unit and the second steering electronic control unit are controlled by the data acquisition and control system to work, and the first steering electronic control unit and the second steering electronic control unit are connected through a CAN bus to realize communication.

2. The vehicle braking and steering system integrated test bench of claim 1, wherein: the brake master cylinder include cylinder body, first piston, first working chamber, first return spring, the second piston, second working chamber and second return spring, wherein the inner chamber of cylinder body is equipped with first piston and second piston from the right side to left side in proper order, be provided with first return spring between first piston and the second piston, form into first working chamber between first piston and the second piston, be provided with second return spring between second piston and the cylinder body inner bottom, form into second working chamber between second piston and the cylinder body inner bottom, be full of brake fluid in first working chamber and the second working chamber.

3. The vehicle braking and steering system integrated test bench of claim 1, wherein: the driver assembled in the electric cylinder selects an S700 driver of Kollmorgen company, closed-loop control of displacement of the electric cylinder CAN be realized through CAN communication, and the speed and acceleration of the movement of the electric cylinder CAN be accurately controlled.

4. The vehicle braking and steering system integrated test bench of claim 1, wherein: the data acquisition and control system comprises a controller, vehicle dynamics simulation software and a simulation test environment, wherein the controller is a SCALEXIO system of dSPACE and is used for hardware-in-loop and rapid control prototype application, the controller provides an IO (input/output) interface for realizing signal interaction between a simulation model and an ECU (electronic control unit) entity, a power supply module is provided for supplying power to the ECU, and an electrical error simulation port is assembled in the controller and can access a fault insertion unit to simulate errors in ECU wiring; the vehicle dynamics simulation software comprises Matlab/Simulink and CarSim, the CarSim provides a complete vehicle dynamics model, the Simulink can be used for building a dynamics model as required, a simulation test environment is configured in the CarSim as required and comprises road conditions, weather, signal lamps and buildings, dSPACE, Matlab/Simulink and CarSim software are installed in an upper computer, a test model is built in the upper computer, a software and hardware interface is configured in a configuration desk, then the model is compiled, downloaded and linked to generate a target file and an executable file format of the dSPACE, a controller in the data acquisition and control system receives an executable file transmitted by the upper computer, and simultaneously transmits acquired signals and internal parameter signals to the upper computer, and the upper computer detects and modifies an operation result of the model in a test platform and related parameters of the model through a ControlDesk.

5. The vehicle braking and steering system integrated test bench of claim 1, wherein: the power supply system comprises a programmable power supply, a 380V alternating current and a storage battery, wherein the programmable power supply supplies power to the hydraulic braking unit, the first steering electric control unit and the second steering electric control unit; 380V alternating current is used for supplying power to the electric cylinder; the voltage of the storage battery is 12V, and the storage battery supplies power for the electric control unit and the driving robot.