A by-wire hydraulic steering system and a redundancy control method thereof

Abstract

The present application relates to a kind of drive-by-wire hydraulic steering system and its redundancy control method, the hydraulic steering system includes: double controller terminal;Steering wheel subsystem, including steering wheel, road feeling torque motor, motor encoder, torque motor driver and steering encoder;Hydraulic steering wheel subsystem, including oil supply hydraulic element, electro-hydraulic proportional reversing valve, safety pressure stabilizing valve block, double steering cylinder and double stroke sensor.The each subsystem has the redundancy against single point failure, by mutual check of multiple sensor data, realize fault detection, design finite state machine and its state switching mechanism, realize the redundancy control of steering system under multiple abnormal conditions, guarantee the stable operation of steering system and the safety of engineering task.Compared with prior art, the present application is more suitable for articulated hydraulic steering equipment, uses redundancy design to guarantee the reliability and safety of steering system, while fully utilizing redundant equipment to improve steering precision, reduce cost.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of steering system of engineering machinery equipment, and relates to a by-wire hydraulic steering system and a redundancy control method thereof. BACKGROUND

[0002] The steering system of traditional hinged engineering construction equipment uses hydraulic power to rotate, for example, a wheel loader, a wheel excavator and the like use a full hydraulic reversing valve to control the extension and retraction movement of a double hydraulic cylinder, thereby driving the front and rear ends of the engineering machinery to rotate relative to the hinge point. It has the characteristics of relatively low cost. However, it also has obvious disadvantages, such as laborious steering, low steering accuracy, poor return accuracy, etc.

[0003] The biggest difference between by-wire steering (SBW) and other power steering systems is that there is no physical connection between the steering wheel and the actuator. It has obvious advantages in control flexibility, function richness, space layout, and reducing fuel consumption. The application of by-wire steering in engineering machinery is a developing trend. It can realize intelligent stable steering, variable transmission ratio and automatic driving of engineering equipment and other advanced functions.

[0004] When the wheel loader and other engineering machinery work in harsh environments, they may encounter scenarios such as sensor damage and controller failure. Therefore, it is necessary to design a redundancy system and control strategy to improve the fault tolerance of the steering system, which is the core requirement for upgrading the by-wire steering system. The redundancy design of the engineering construction steering system ensures normal operation when the components are damaged, quickly switches when a fault occurs, and maintains the continuity and safety of the engineering.

[0005] As CN202411005476.4 provides a steer-by-wire device with full redundancy function and control method, the main design concept is that the steer-by-wire device with full redundancy function obtains redundant four-way torque signals and two-way angle signals through the torque angle sensor on the steering wheel, and obtains redundant two-way angle signals through the angle sensor on the gear shaft to obtain accurate torque angle information. In addition, the road feeling motor and the steering motor are both double three-phase permanent magnet synchronous motors, and the road feeling motor controller and the steering motor controller are both double control unit architectures and redundant communication mechanisms. Through the above three aspects of detailed redundancy design, when the steer-by-wire single-point failure causes three phases to be unable to work, the system still has road feeling feedback and steering execution capability. Combined with the design of the rack force and reference hand force calculation strategy in the control logic, the system can still work normally when the key components of the steering system fail, thereby ensuring the stability and safety of vehicle driving. The redundancy scheme cannot cope with the problem of single terminal controller signal failure, and the redundancy degree is lacking. There is a complex mechanical transmission structure, high space occupancy rate, and high hardware cost of the redundancy scheme. There is no countermeasure for high-frequency high-amplitude vibration in complex construction environment, and the observation accuracy of multiple position sensors decreases. The redundancy control means lacks precision guarantee, and cannot meet the safety construction demand. SUMMARY

[0006] The purpose of the present application is to provide a steer-by-wire hydraulic steering system and a redundancy control method thereof, which effectively solves at least one of the problems of the existing hydraulic steering system of engineering construction equipment, such as low matching precision of steering wheel angle and steering wheel angle, laborious steering wheel operation, poor robustness, stability and safety of the steering system, and the like.

[0007] The purpose of the present application can be achieved by the following technical solutions.

[0008] In a first aspect, the present application provides a steer-by-wire hydraulic steering system, comprising:

[0009] A steering wheel subsystem comprising a steering wheel, a road feeling torque motor, a motor encoder, a torque motor driver and a steering encoder, wherein the steering wheel is used to obtain the steering intention of the driver, the road feeling torque motor is connected to the steering wheel through a steering wheel transmission structure, the motor encoder and the steering encoder are used to measure the steering angle of the steering wheel at the same time, and the torque motor driver is used to control the operation of the road feeling torque motor.

[0010] A hydraulic steering wheel subsystem comprising an oil supply hydraulic element, an electro-hydraulic proportional reversing valve, a safety pressure stabilizing valve block, a double steering cylinder and a double stroke sensor, wherein the double stroke sensor is used to obtain the stroke data of the left and right sides of the double steering cylinder.

[0011] The double-controller terminal comprises a main controller ECU and a backup controller ECU, wherein the main controller ECU serves as a working controller to process steering instructions and control the steer-by-wire hydraulic steering in real time, and the backup controller ECU serves as a check controller to supervise the implementation of instructions of the working controller.

[0012] Further, the main controller ECU and the backup controller ECU have a communication function, and when the main controller ECU is abnormal, the main / backup switching is performed, and the backup controller ECU 2 serves as the working controller to maintain the normal operation of the hydraulic steering system

[0013] In the second aspect, the application provides a control method of a steer-by-wire hydraulic steering system, comprising the following steps:

[0014] S1, performing an initialization steering system link, checking the system unit state, aligning the steering wheel and the steering wheel angle;

[0015] S2, entering a working mode cycle, detecting the state of the steering system, and realizing real-time steer-by-wire steering, wherein the redundant control strategy of the steer-by-wire steering working adopts a finite state machine, different operating states of the steering system are monitored, event and transition logic of state switching are formulated, and the reliability of the steering function of the engineering vehicle is ensured.

[0016] Further, in S1, in the initialization steering system link, the working controller calculates the steering wheel hinge point angle according to the steering angle observation value of the double-stroke sensor, and inputs the steering wheel hinge point angle as the expected steering wheel angle to the torque motor driver, so that the torque motor is driven by the steering wheel transmission structure to drive the steering wheel to the alignment angle of the steering wheel.

[0017] Further, the alignment result of the steering wheel is verified by the steering encoder observation value, and when the road feeling torque motor cannot drive the steering wheel to align in the initialization link, the steering wheel angle observation abnormal state is directly switched to, and the current steering wheel angle is taken as the alignment angle of the steering wheel, and the steering range and the steering ratio are limited.

[0018] Further, in S2, in the redundant control strategy finite state machine, the entire steer-by-wire hydraulic steering system has a normal state and an abnormal state, wherein the abnormal state is at least one of the following states, and therefore, after mutual combination, there can be seven cases:

[0019] The working controller abnormal state is activated by the main controller ECU failure event;

[0020] The steering wheel angle observation abnormal state is activated by the double-encoder observation difference exceeding the threshold value event;

[0021] The abnormal state of the steering wheel rotation angle observation is activated by the left and right steering wheel rotation angle observation difference exceeding the threshold event.

[0022] Further, the main controller ECU failure event activation logic is: when the standby controller ECU performs a detection program to check the IO, communication link and program logic execution of the main controller ECU, the standby controller ECU acquires the internal variables of the main controller ECU and switches to the working mode to take over the control, while isolating the main controller ECU;

[0023] The double-encoder observation difference exceeding the threshold event activation is: the working controller ECU acquires the steering angle values of the motor encoder and the steering encoder in a single working cycle, and determines whether to shield the motor encoder built-in the road feeling torque motor according to the difference between the two and the preset threshold, and instead uses the steering encoder acquisition value as the expected steering angle of the driver, and outputs the road feeling torque motor failure warning information;

[0024] The left and right steering wheel rotation angle observation difference exceeding the threshold event activation: compare the difference between the steering wheel rotation angles calculated from the observation values of the double-stroke sensors with the threshold value, when the threshold value is exceeded, it is determined that there is a failure, and the expected steering angle of the working ECU is used as a reference, the maximum angle deviation object is used as the failed stroke sensor, the acquisition value is ignored and the warning information is output.

[0025] Further, in the S2 detection of the state of the steering system, the state of the hydraulic steering wheel system is observed with redundancy design, and the double-stroke sensors installed on the double steering oil cylinders are used to realize the redundant observation and accurate measurement of the steering angle of the front end of the construction equipment;

[0026] The double-stroke sensor ensures that when one of the stroke sensors fails, the steering angle can still be obtained from the measurement results of the other stroke sensor, realizing the redundant observation of the steering state.

[0027] Under normal working conditions, the double-stroke sensor simultaneously outputs the stroke data of the left and right sides of the double steering oil cylinder, and the derivation formula of the steering angle θ is:

[0028] θ=(θ l +θ r ) / 2,

[0029] Among them, the calculation formula of the steering angle θ l derived based on the left stroke data observed by the double-stroke sensor is:

[0030]

[0031] The calculation process of the steering angle θ r derived based on the right stroke data observed by the double-stroke sensor is:

[0032]

[0033] wherein, AL l represents the elongation of the left side of the double stroke sensor relative to the straight running; AL r represents the elongation of the right side of the double stroke sensor relative to the straight running; A, B, k, are constant coefficients, and the calculation formula is:

[0034]

[0035] wherein, h f represents the vertical distance from the front and rear hinge points to the front end cylinder connection point, h r represents the vertical distance from the front and rear hinge points to the rear end cylinder connection line, d f represents half the distance from the front end cylinder connection point, d r represents half the distance from the rear end cylinder connection point, h f , h r , d f , d r are measured when the vehicle is straight running. It should be noted that the articulated engineering machinery is divided into front and rear frames, and the hinge shaft is connected in the middle, which is the common knowledge in the art.

[0036] Under abnormal conditions, the observation data provided by the normally operating single stroke sensor is used as the steering angle value.

[0037] Further, in the S2 state detection of the steering system, the steering signal acquisition of the steering wheel subsystem is redundantly designed, the steering wheel rotation angle is measured by the motor encoder and the steering encoder at the same time, when the difference between the two observation values of the steering angle of the steering wheel exceeds the threshold value, it means that there is an encoder failure, and the steering angle calculated by the cylinder stroke sensor is used as a reference, and the encoder with the largest angle deviation is determined as the failure, wherein,

[0038] When the motor encoder fails, the road feeling torque motor cannot perform torque feedback, and is immediately isolated by the working controller, and the steering angle value of the steering encoder is directly obtained, and the difference between the steering wheel angle and the steering wheel angle is used to calculate the flow opening of the electro-hydraulic proportional directional valve, and the maximum steering angle and steering speed are limited;

[0039] When the steering encoder fails, it is also isolated by the system, and the steering wheel retains the road feeling feedback and normally transmits the steering information. In this way, mutual checking between sensors is realized, which not only can detect failed elements, but also can ensure accuracy.

[0040] Further, S2 detects the state of the steering system in each working cycle, and in the event of single or combined failure of the main controller ECU, the stroke sensor or the steering wheel angle measurement encoder, the finite state machine system can automatically switch to the corresponding state and execute the response action program to maintain stable operation of the steering system.

[0041] Wherein, the response action program for failure of the main controller ECU is to enable the backup controller ECU and execute the working control program to obtain the running state parameters of the main ECU; the response action program for failure of the single steering wheel encoder is to use another single steering wheel encoder to read the steering intention; the response action program for failure of the single stroke sensor is to use another single stroke sensor to observe the real-time steering angle. For the comprehensive failure condition, the state machine with the above combined response action is used. Here, the motor encoder and the steering encoder are collectively referred to as the steering wheel encoder.

[0042] In a third aspect, the present application provides a computer readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the control method of the by-wire hydraulic steering system as described above. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 An engineering machinery by-wire hydraulic steering system according to the embodiment;

[0044] Figure 2 A hydraulic articulated steering model according to the embodiment;

[0045] Figure 3 A program element and state machine of the by-wire hydraulic steering system according to the embodiment;

[0046] Figure 4 A program running logic of the redundancy control strategy of the by-wire hydraulic steering system according to the embodiment;

[0047] MARKED DESCRIPTION IN THE FIGURE:

[0048] 1- steering wheel subsystem; 11- steering wheel; 12- steering wheel transmission structure; 13- road feel torque motor; 14- motor encoder; 15- torque motor driver; 16- steering encoder; 2- hydraulic steering wheel subsystem, 21- oil supply hydraulic element; 22- electro-hydraulic proportional directional valve; 23- safety pressure stabilizing valve block; 24- double steering oil cylinder; 25- double stroke sensor; 31- main controller ECU; 32- backup controller ECU; 41- normal state; 42- abnormal state; 43- working controller abnormal state; 44- steering wheel angle observation abnormal state; 45- steering wheel angle observation abnormal state. DETAILED DESCRIPTION

[0049] The application will be described in detail below in conjunction with the drawings and specific embodiments. The embodiments are implemented on the premise of the technical solutions of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the following embodiments.

[0050] In the description of the application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application. In addition, the terms "first", "second", "third" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0051] In the description of the application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0052] To solve the problems of the existing engineering construction equipment hydraulic steering system, such as low matching precision of steering wheel 11 turning angle and steering wheel turning angle, laborious operation of steering wheel 11, poor robustness, stability and safety of the steering system, in some embodiments, a steer-by-wire hydraulic steering system is provided, as shown in Figure 1 The steer-by-wire hydraulic steering system can realize physical decoupling of the steering wheel 11 and the hydraulic steering wheel.

[0053] Please refer to Figure 1 and Figure 2 In some specific embodiments, the steering wheel subsystem 1 includes a steering wheel 11, a road feel torque motor 13, a motor encoder 14, a torque motor driver 15, and a steering encoder 16, wherein the steering wheel 11 is used to obtain the steering intention of the driver, the road feel torque motor 13 is connected to the steering wheel 11 through a steering wheel transmission structure 12, the motor encoder 14 and the steering encoder 16 are used to simultaneously measure the steering angle of the steering wheel 11, and the torque motor driver 15 is used to control the operation of the road feel torque motor 13.

[0054] The hydraulic steering wheel system 2 comprises an oil supply hydraulic element 21, an electro-hydraulic proportional reversing valve 22, a safety pressure stabilizing valve block 23, a double steering oil cylinder 24, and a double stroke sensor 25, wherein the double stroke sensor 25 is used to acquire the stroke data of the left and right sides of the double steering oil cylinder 24.

[0055] The double controller terminal comprises a main controller ECU 31 and a backup controller ECU 32, wherein the main controller ECU 31 serves as a working controller to process steering instructions and control the by-wire hydraulic steering in real time, and the backup controller ECU 32 serves as a verification controller to supervise the implementation of instructions of the working controller.

[0056] The by-wire hydraulic steering system provided above has three redundant designs, including a main / backup controller ECU redundant design, a steering signal acquisition redundant design of the steering wheel subsystem 1, and a state observation redundant design of the hydraulic steering wheel system 2, so as to ensure the reliability and stability of the by-wire hydraulic steering function and realize safe operation in engineering construction.

[0057] The main / backup controller ECU redundant design is that, under normal working conditions, the main controller ECU 31 serves as a working controller to process steering instructions and control the steering system in real time, and the backup controller ECU 32 serves as a verification controller to supervise the implementation of instructions of the working controller. When the main controller ECU 31 is abnormal, the main / backup switching is performed, and the backup controller ECU 32 serves as a working controller to maintain normal operation of the hydraulic steering system.

[0058] In some specific embodiments, the program function of the working controller is to perform closed-loop control on the steering of the articulated hydraulic steering mechanism according to the expected steering angle output by the steering wheel subsystem 1 as input and the oil cylinder stroke collected by the double stroke sensor 25 as feedback information, so as to realize labor-saving and precise steering. The main steering control program is equipped with functions such as self-defined steering proportion of the by-wire hydraulic steering system, steering road feel feedback, and automatic return of the steering wheel 11.

[0059] In some specific embodiments, as shown in Figure 3 The steering signal acquisition redundant design of the steering wheel subsystem 1 is characterized in that the motor encoder 14 of the road feel torque motor 13 and the additional absolute value steering encoder 16 are used to simultaneously measure the rotation angle of the steering wheel 11. When the observation values of the steering wheel 11 by the two encoders differ by more than a threshold value, it is indicated that there is an encoder failure.

[0060] When the motor encoder 14 fails (no signal output), and the road feel torque motor 13 cannot perform torque feedback, it will be immediately isolated by the working controller ECU, and the system will be switched to the standby steering angle control program. The system directly obtains the steering angle value of the steering encoder 16, calculates the flow opening of the electro-hydraulic proportional reversing valve 22 from the difference between the steering wheel 11 steering angle and the steering wheel steering angle, and limits the maximum steering angle and steering speed in the steering program. Although the road feel is lost, the driver can still control the vehicle steering. When the steering encoder 16 fails, it is also soft-isolated by the system, and the steering wheel 11 retains the road feel feedback and normally transmits the steering information. The failure of the steering wheel 11 encoder is inferred by the alarm system to the user for timely maintenance.

[0061] In some specific embodiments, the hydraulic steering wheel system 2 state observation redundancy design realizes redundant observation and accurate measurement of the front end steering angle of the construction equipment by means of the double stroke sensors 25 installed on the double steering oil cylinders 24. This design can ensure that the steering angle can still be measured by the remaining stroke sensor when a single stroke sensor fails, and ultimately realize the redundant observation of the steering state.

[0062] As shown in Figure 2 , the double stroke sensor 25 is divided into a left stroke sensor and a right stroke sensor, corresponding to the left side and the right side of the double stroke sensor 25, respectively. By obtaining the left stroke sensor data, the steering angle θ l The derivation formula is as follows:

[0063]

[0064] Where ΔL l represents the elongation of the left stroke sensor relative to the elongation during straight-line driving. A, B, k, are four constant coefficients, and the calculation formula is as follows:

[0065]

[0066] Where h f represents the vertical distance from the front and rear hinge points to the front end oil cylinder connection point, h r represents the vertical distance from the front and rear hinge points to the rear end oil cylinder connection point, d f represents half the distance of the front end oil cylinder connection point, d r represents half the distance of the rear end oil cylinder connection point, h f , h r , d f , d r are measured during vehicle straight-line driving calibration.

[0067] Under normal conditions, the double stroke sensor 25 outputs data simultaneously to improve the measurement accuracy of the steering angle. After obtaining the stroke data of the left and right oil cylinders, the steering angle derivation formula is as follows:

[0068] θ = (θ l + θ r ) / 2

[0069] Wherein, the right stroke sensor 25 observes the steering angle result θ r The calculation process is as follows:

[0070]

[0071] ΔL r represents the elongation of the right stroke sensor relative to the elongation during straight driving, is the right constant coefficient.

[0072] Under abnormal conditions, the observation data provided by the normally operating single stroke sensor is used as the steering angle value.

[0073] Based on the above provided by the by-wire hydraulic steering system, in some embodiments, a control method of the by-wire hydraulic steering system is further provided, specifically:

[0074] After the hydraulic steering control system is started, it first performs an initialization steering system program to align the steering wheel 11 and the steering wheel angle, enters the working mode cycle, and then performs steering device state detection, realizing real-time by-wire steering. The redundant control strategy of by-wire steering work adopts a finite state machine, which monitors different operating states of the steering system, formulates state switching events and transfer logic, and guarantees the reliability of the steering function of the engineering vehicle.

[0075] In some specific embodiments, in the initialization steering system link, the working controller ECU calculates the steering wheel hinge point angle according to the steering angle observation value of the double stroke sensor 25, and inputs it as the expected steering angle of the steering wheel 11 to the torque motor driver 15, so that it controls the road feeling torque motor 13 to drive the steering wheel 11 to return to the steering wheel alignment angle through the steering wheel transmission structure 12. The return result of the steering wheel 11 is verified by the observation value of the steering encoder 16. When the road feeling torque motor 13 cannot drive the steering wheel 11 to return in the initialization link, it is directly switched to the steering wheel angle observation abnormal state, and the current steering wheel 11 angle is used as the steering wheel alignment angle, and the steering range and steering ratio are limited.

[0076] The above redundant control strategy finite state machine has 8 states (including normal state 41 and abnormal state 42) in the entire hydraulic steering system, and the working controller ECU is used as the logic calculation unit for state switching:

[0077] Wherein, in the normal state 41, the built-in motor encoder 14 of the road feeling torque motor 13 is used as the acquisition sensor of the steering wheel angle, and the steering encoder 16 is responsible for checking the acquisition of the steering angle; the main controller ECU 31 is used as the working controller, and the standby controller ECU 32 is used as the monitoring working controller to check the execution of the controller instructions and to replace the main controller ECU 31; the left and right double stroke sensors 25 are used to observe the angles of the front and rear hinged points.

[0078] The abnormal state 42 includes three basic situations and their combination modes, and the three basic situations are the working controller abnormal state 43, the steering wheel angle observation abnormal state 44, and the steering wheel angle observation abnormal state 45, so there are seven abnormal states.

[0079] The working controller abnormal state is activated by the main controller ECU failure event, and the event activation logic is as follows: when the standby controller ECU 32 executes the detection program to check the IO, communication link and program logic execution of the main controller ECU 31, the standby controller ECU 32 acquires the internal variables of the main controller ECU 31 and switches to the working mode to take over the control, while isolating the main controller ECU 31.

[0080] The steering wheel angle observation abnormal state is activated by the double encoder observation difference exceeding the threshold value event. The event activation logic is as follows: the working controller ECU acquires the steering angle values of the double encoders in a single working cycle, and determines whether to shield the built-in encoder of the road feeling torque motor 13 according to the difference between the two values and the preset threshold value, and instead uses the steering encoder 16 to collect the values as the expected steering angle of the driver, and outputs the torque motor failure warning information.

[0081] The steering wheel angle observation abnormal state is activated by the left and right steering wheel angle observation difference exceeding the threshold value event. The event activation logic is as follows: the difference between the steering wheel angles calculated by the double stroke sensors 25 is compared with the threshold value, and when the threshold value is exceeded, it is determined that there is a failure, and according to the expected steering angle in the current working cycle, the failure stroke sensor is determined, the acquisition value is ignored and the warning information is output.

[0082] In some specific embodiments, during the control process, the master / standby controller adopts a redundant design, the working controller ECU is responsible for real-time control of the operation of the steer-by-wire system, and the standby controller ECU 32 monitors the execution effect of the master controller in real time. The two controllers have communication between them. When the master controller ECU 31 fails, the standby controller ECU 32 can immediately receive the intermediate variable data sent by the master controller ECU 31 and switch to the working mode to run the steering control program, ensuring the continuous operation of the steer-by-wire system. The double closed-loop control circuit adopted by the present application solves the problem of single controller failure and improves the safety and stability of the system.

[0083] In some specific embodiments, the state of the steering system is detected in a certain working cycle, and single or combined failure conditions of the master controller ECU 31, the stroke sensor or the steering wheel angle measurement encoder occur. The finite state machine system can automatically switch to the corresponding state and execute the response action program to maintain stable operation of the steering.

[0084] The response action program for master controller ECU failure is to enable the standby controller ECU 32 and execute the working control program to obtain the operating state parameters of the master ECU. The response action program for single steering wheel encoder failure is to use another single steering wheel encoder to read the steering intention. The response action program for single stroke sensor 25 failure is to use another single stroke sensor to observe the real-time angle. For the integrated failure condition, the state machine of the combined response action is used.

[0085] In addition, in some embodiments, a computer readable storage medium storing a computer program is also provided, and the computer program is executed by a processor to implement the steps of the control method of the steer-by-wire hydraulic steering system as described above. The storage medium can be an electronic medium, a magnetic medium, an optical medium, an electromagnetic medium, an infrared medium or a semiconductor system or a propagation medium. The storage medium can also include a semiconductor or solid state memory, a magnetic tape, a removable computer disk, a random access memory (RAM), a read-only memory (ROM), a hard disk and an optical disk. The optical disk can include a compact disk-read only memory (CD-ROM), a compact disk-read / write (CD-RW) and a DVD.

[0086] The above description of the embodiments is to facilitate those skilled in the art to understand and use the invention. Those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described herein to other embodiments without having to go through creative labor. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art within the scope of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A control method of a by-wire hydraulic steering system, characterized by, The line control hydraulic steering system comprises: A steering wheel subsystem comprising a steering wheel, a road feel torque motor, a motor encoder, a torque motor driver and a steering encoder, wherein the steering wheel is used to obtain the steering intention of a driver, the road feel torque motor is connected to the steering wheel through a steering wheel transmission structure, the motor encoder and the steering encoder are used to simultaneously measure the steering angle of the steering wheel, and the torque motor driver is used to control the operation of the road feel torque motor; A hydraulic steering wheel subsystem comprising an oil supply hydraulic element, an electro-hydraulic proportional reversing valve, a safety pressure stabilizing valve block, a double steering oil cylinder and a double stroke sensor, wherein the double stroke sensor is used to obtain the stroke data of the left and right sides of the double steering oil cylinder; A double controller terminal comprising a main controller ECU and a backup controller ECU, wherein the main controller ECU serves as a working controller to process steering instructions and control the line control hydraulic steering in real time, and the backup controller ECU serves as a verification controller to supervise the implementation of the instructions of the working controller; The control method comprises the following steps: S1, performing initialization of the steering system links, checking the state of the system units, and aligning the steering wheel and the steering wheel angle; S2, entering a working mode cycle, detecting the state of the steering system, and realizing real-time line control steering, wherein the redundant control strategy of the line control steering working adopts a finite state machine, different operating states of the steering system are monitored, the event and transition logic of state switching are formulated, and the reliability of the steering function of the engineering vehicle is ensured; In S2, in the redundant control strategy finite state machine, the entire line control hydraulic steering system has a normal state and an abnormal state, wherein the abnormal state is at least one of the following states: The working controller abnormal state is activated by the main controller ECU failure event; The steering wheel angle observation abnormal state is activated by the double encoder observation difference exceeding the threshold event; The steering wheel angle observation abnormal state is activated by the left and right steering wheel angle observation difference exceeding the threshold event; The main controller ECU failure event activation logic is that when the backup controller ECU executes a detection program to check the IO, communication link and program logic execution of the main controller ECU, the backup controller ECU acquires the internal variables of the main controller ECU and switches to the working mode to take over the control, while isolating the main controller ECU; The double encoder observation difference exceeding the threshold event activation logic is that the working controller ECU acquires the steering angle values of the motor encoder and the steering encoder in a single working cycle, determines whether to shield the motor encoder built in the road feel torque motor according to the difference between the two and a preset threshold, uses the steering encoder acquisition value as the expected steering angle of the driver, and outputs the road feel torque motor failure warning information; The left and right steering wheel angle observation difference exceeding the threshold event activation logic is that the difference between the steering wheel angles calculated from the observation values of the double stroke sensors is compared with the threshold, when the difference exceeds the threshold, it is determined that there is a failure, the expected steering angle of the working controller is taken as a reference, the angle deviation maximum object is taken as the failed stroke sensor, the acquisition value of the stroke sensor is ignored, and warning information is output.

2. A control method of a by-wire hydraulic steering system according to claim 1, characterized by, The main controller ECU and the standby controller ECU have a communication function, when the main controller ECU is normal, it serves as the working controller, and the standby controller ECU serves as the check controller; when the main controller ECU is abnormal, the main / standby switching is performed, the standby controller ECU serves as the working controller, and the normal operation of the hydraulic steering system is maintained.

3. A control method of a by-wire hydraulic steering system according to claim 1, characterized by, In S1, the initialization of the steering system, the working controller collects and checks the state of each unit, calculates the front and rear hinge point angles according to the steering angle observation value of the double stroke sensor, and inputs the expected steering wheel angle to the torque motor driver, so that the road feeling torque motor drives the steering wheel to return to the alignment angle of the steering wheel through the steering wheel transmission structure.

4. A control method of a wire hydraulic steering system according to claim 3, characterized by, The steering encoder observation value is used to verify the steering wheel return result, when the road feeling torque motor cannot drive the steering wheel to return in the initialization link, the steering wheel angle observation abnormal state is directly switched to, and the current steering wheel angle is taken as the alignment angle of the steering wheel, and the steering range and steering ratio are limited.

5. The control method of a by-wire hydraulic steering system according to claim 1, characterized by, In S2, the state of the steering system is detected, the state observation of the hydraulic steering wheel system is redundantly designed, and the double stroke sensor installed on the double steering cylinder is used to realize the redundant observation and accurate measurement of the front end steering angle of the construction equipment; The double stroke sensor ensures that the steering angle can be obtained by the measurement result of the other stroke sensor when one of the stroke sensors fails, and the redundant observation of the steering state is realized; Under normal working conditions, the double stroke sensor simultaneously outputs the stroke data of the left and right sides of the double steering cylinder, and the derivation formula of the steering angle θ is: θ = (θ l + θ r ) / 2, wherein the steering angle θ derived based on the left travel data observed by the double stroke sensor l The calculation formula is: steering angle θ derived based on right lane travel data observed by a double travel sensor r The calculation process is as follows: wherein ΔL l represents the elongation of the left side of the double stroke sensor with respect to the straight running; ΔL r represents the elongation of the right side of the double stroke sensor with respect to the straight running; A, B, k, are constant coefficients, and the calculation formula is: where h f represents the vertical distance from the front and rear hinge points to the front cylinder connection point, h r represents the vertical distance from the front and rear hinge points to the rear cylinder connection point, d f represents half the distance from the front cylinder connection point, d r represents half the distance from the rear cylinder connection point, h f , h r , d f , d r measured at vehicle straight running calibration; Under abnormal conditions, the observation data provided by the normally operating single stroke sensor is used as the steering angle value.

6. A control method of a by-wire hydraulic steering system according to claim 1, characterized by, In S2, the steering signal acquisition of the steering wheel system is redundantly designed, the steering angle is measured by the motor encoder and the steering encoder at the same time, when the difference between the two observation values of the steering angle of the steering wheel exceeds the threshold value, it is indicated that there is an encoder failure, and the steering angle calculated by the cylinder stroke sensor is used as a reference, and the encoder with the largest angle deviation is determined as the failure, wherein, When the motor encoder fails, the road feeling torque motor cannot perform torque feedback, and is immediately isolated by the working controller, and the steering angle value of the steering encoder is directly obtained, and the difference between the steering wheel angle and the steering wheel angle observation is used to calculate the flow opening of the electro-hydraulic proportional reversing valve, and the maximum steering angle and the steering speed are limited; When the steering encoder fails, it is also isolated by the system, the steering wheel retains the road feeling feedback and normally transmits the steering information.

7. A computer readable storage medium storing a computer program, characterized in that, The computer program is executed by the processor to realize the steps of the control method of the steer-by-wire hydraulic steering system according to claim 1.

Images