Unmanned engineering machinery steer-by-wire system and control method

Abstract

The invention discloses an unmanned engineering machinery steer-by-wire system and a control method in the technical field of vehicle chassis and steering systems. The unmanned engineering machinery steer-by-wire system comprises four wheels and steering modules, wherein the steering modules are in one-to-one correspondence with the four wheels, are completely independent and have the same structure; the corner deflection of the four wheels is cooperatively controlled through a distributed electronic control system; and each wheel is driven by a hub motor. Through four-wheel steering, the minimum turning radius can be 0 m, the trafficability in narrow roadways, sidewalks and obstacle dense areas is improved, meanwhile, four-wheel steering is independently controlled, special movement forms such as transverse translation and oblique advancing are supported, and the four-wheel steering robot is particularly suitable for high-precision operation requirements such as urban road edge stone attaching and sweeping; four-wheel independent main pin steering is combined with a hub motor and distributed redundancy control, so that the reliability, the function safety and the maintainability of the system are remarkably improved, and the system is particularly suitable for unmanned engineering machinery to work for a long time in narrow, complex and severe environments.

Description

TECHNICAL FIELD

[0001] The present application relates to an unmanned engineering machinery steer-by-wire system and a control method, belonging to the technical field of vehicle chassis and steering system. BACKGROUND

[0002] With the acceleration of the intelligentization process of urban environmental sanitation cleaning operations, unmanned environmental sanitation cleaning vehicles have gradually become the key technical carrier to solve the high labor cost and complex operation environment. In the field of traditional environmental sanitation cleaning vehicles, the steering system mostly adopts full hydraulic steering, which continuously provides pressure oil through a hydraulic pump, drives the steering cylinder through a full hydraulic steering gear to realize wheel steering. However, the full hydraulic steering system cannot meet the rapid response and high-precision execution under the working condition of high frequency and small amplitude steering correction required by trajectory tracking in the scenario of unmanned environmental sanitation cleaning operation. In view of the demand of steer-by-wire system for unmanned environmental sanitation cleaning vehicles, the current mainstream technical solutions in the industry mainly focus on two types of electric power-assisted front axle steering and electric recirculating ball front axle steering. Compared with traditional mechanical or hydraulic systems, the control accuracy and energy efficiency are improved, but there are still significant limitations in adapting to the ultra-narrow vehicle body, complex working conditions and high mobility requirements of unmanned environmental sanitation vehicles.

[0003] The electric power-assisted steering system mainly consists of a steering motor, a worm gear / gear reduction mechanism, a torque / angle sensor and an electronic control unit (ECU) as the core execution layer, which drives the wheels through a mechanical transmission chain (steering shaft→gear rack→tie rod→knuckle arm). When unmanned steering operation is performed, the automatic driving controller sends a target steering angle instruction to the ECU, the ECU generates a motor control signal in combination with sensor feedback, the motor output torque is amplified through the reduction mechanism, the gear rack moves horizontally, the tie rod is pulled to drive the front wheels to deflect synchronously, and the angle sensor verifies the position in real time to realize precise steering angle tracking.

[0004] The electric recirculating ball steering system mainly drives the worm input by a servo motor, links the recirculating ball steering gear (including worm, ball raceway, steering nut and sector tooth output mechanism), transmits power to the knuckle arm through the rocker arm and the straight pull rod, and is assisted by the motor encoder and the output shaft angle sensor to monitor the position. When unmanned steering operation is performed, the automatic driving system issues a target wheel steering angle instruction, the motion controller calculates the required angle of the worm, and then the servo motor accurately rotates the worm to drive the steering nut to move axially, drive the sector teeth to swing, and the output shaft pulls the steering straight pull rod through the rocker arm to realize the deflection of the front wheels. At the same time, a steering angle sensor is designed and installed at the steering kingpin to feedback the actual steering angle and realize closed-loop control.

[0005] Fully hydraulic steering relies on a continuous engine-driven hydraulic pump, maintaining high-pressure circulation even when the vehicle is moving straight, resulting in significant energy waste and contradicting the trend towards electrification and low power consumption in unmanned sanitation vehicles. Furthermore, the risk of hydraulic oil leakage could pollute the working environment, which is inconsistent with the core principles of sanitation vehicle cleaning operations. Additionally, the steering angle control of a fully hydraulic steering system depends on the opening adjustment of hydraulic valves, and its non-linear flow characteristics easily lead to steering lag and overshoot. In autonomous driving scenarios, trajectory tracking requires frequent, small-amplitude steering corrections, but the inertial delay and valve response lag of the hydraulic system cannot meet real-time control requirements.

[0006] Electric power steering systems typically only drive the front wheels for steering, resulting in a minimum turning radius limited by wheelbase and track width, making it difficult to perform highly maneuverable maneuvers such as "sweeping close to the edge" or "right-angle bends" in narrow streets and alleys. The amount of garbage loaded in sanitation vehicles changes dynamically during operation, and the steering motor must be selected according to the peak load, resulting in long-term inefficient operation of the motor under light load, with prominent energy consumption and heat generation issues. The system relies on a single motor and controller, and once it fails, it will directly lead to the loss of steering function. In addition, driverless sanitation vehicles need to meet functional safety requirements, requiring the addition of redundant motors or backup systems, further encroaching on the limited vehicle space.

[0007] The electric recirculating ball steering system integrates a motor-driven worm gear on the basis of the traditional recirculating ball mechanism, replacing the mechanical input shaft with electronic control. Although it has a certain load capacity, its design characteristics are fundamentally in conflict with the requirements of unmanned sanitation vehicles: the recirculating ball mechanism relies on a mechanical transmission chain of worm gear and sector teeth, and the transmission clearance and elastic deformation cause steering backlash, making it difficult to meet the millimeter-level accuracy requirements of unmanned driving trajectory tracking; the recirculating ball steering assembly is relatively large, which contradicts the layout of ultra-compact sanitation vehicles. The inherent high reduction ratio and friction loss of worm gear transmission cause steering response delay, which cannot match the high-frequency steering commands of unmanned driving systems under complex road conditions.

[0008] Therefore, there is an urgent need for a steering system that abandons the traditional front axle steering architecture and deeply integrates four-wheel independent drive with high-precision electromechanical actuators. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a steer-by-wire system and control method for unmanned engineering machinery.

[0010] To solve the above-mentioned technical problems, the present invention is implemented using the following technical solution.

[0011] In a first aspect, the present invention discloses a steer-by-wire system for unmanned engineering machinery, comprising: four wheels and a steering module that corresponds one-to-one with the four wheels, is completely independent and has the same structure; The steering angle deflection of the four wheels is controlled collaboratively by a distributed electronic control system. Each of the wheels is driven by a hub motor.

[0012] Furthermore, the steering module includes a steering actuator and a steering knuckle kingpin; The steering actuator includes an axial flux permanent magnet synchronous servo motor and a cycloidal pinwheel reducer that are directly coupled through a flange. The output shaft of the axial flux permanent magnet synchronous servo motor is coaxially connected to the input end of the cycloidal pinwheel reducer via a key. The steering knuckle kingpin adopts a sleeve-type structure. The inner ring connecting hole of the sleeve-type structure is connected to the output flange of the cycloidal pinwheel reducer by bolts. The outer ring connecting hole of the sleeve-type structure is connected to the steering knuckle by bolts. The steering actuator is installed in the sleeve of the steering knuckle kingpin through a cross roller bearing at the radial connection of the sleeve-type structure.

[0013] Furthermore, the connection structure between the steering knuckle kingpin and the cycloidal reducer also includes an upper bearing limit connector, a lower bearing limit connector, and a bearing end cap. The upper limit connector of the bearing is fixed to the housing of the cycloidal pinwheel reducer by bolts, the lower limit connector of the bearing is fixed to the upper limit connector of the bearing by bolts, thereby limiting the crossed roller bearing to the transmission position of the steering knuckle kingpin, and the bearing end cover is fixed to the steering knuckle kingpin by bolts.

[0014] Furthermore, a multi-turn absolute encoder is built into the tail end of the axial flux permanent magnet synchronous servo motor to measure the position of the motor rotor and obtain the current wheel steering information. The axial flux permanent magnet synchronous servo motor is also equipped with a rotary transformer for providing redundant position information. The absolute encoder and rotary transformer of each steering module convert the current actual steering angle signal. The current actual steering angle signals of the two are cross-validated in real time. If the deviation of the motor rotor position fed back by the two is greater than the preset threshold, it is determined that there is a fault in the current steering module; otherwise, there is no fault.

[0015] Furthermore, the axial flux permanent magnet synchronous servo motor is equipped with a normally closed electromagnetic brake that automatically locks up when power is lost. A torque sensor for real-time monitoring of steering resistance torque is integrated at the front end of the cycloidal pinwheel reducer; When each steering module performs a steering action while driving, it also performs electronic differential control on the rotation of the tires. Specifically, it calculates the linear speed of the wheel rotation when each wheel is turning based on the steering center position.

[0016] Furthermore, the distributed electronic control system adopts a master-slave architecture, including a master controller (VCU), four slave controllers (ECUs), and a power supply. Each of the four slave controllers (ECUs) corresponds to a steering module, and each slave controller (ECU) is integrated with the axial flux permanent magnet synchronous servo motor of each steering module. The slave controller (ECU) communicates with the master controller (VCU) via high-speed CANFD, and is responsible for receiving the steering angle command of the corresponding wheel and driving the axial flux permanent magnet synchronous servo motor to realize the position servo closed-loop control of the wheel steering angle. The main controller (VCU) receives macroscopic path instructions from the autonomous driving controller and calculates the independent target turning angle and angular velocity instructions for the four wheels in real time based on the vehicle kinematics model; at the same time, it limits the angular velocity and acceleration based on the road adhesion coefficient estimation and the tire lateral slip model.

[0017] Furthermore, the slave controller ECU has dual-channel position acquisition, torque sensing acquisition, and overcurrent / overtemperature / short circuit protection. It performs position-speed-current cascade control and has S-shaped acceleration / deceleration trajectory planning, friction compensation, and dead zone compensation functions. The slave controller ECU and the master controller VCU maintain millisecond-level time synchronization. The dual-channel position acquisition adopts a heterogeneous sensor redundancy architecture, including synchronous orthogonal signal acquisition of a rotary transformer and an absolute encoder, and realizes real-time verification and fault tolerance of dual-source data through a phase compensation algorithm. The power system provides dual independent power supplies to the main controller VCU, each slave controller ECU, and sensors. Both channels can carry the full load. In the event of a single channel failure, undervoltage, or overvoltage, the system maintains power supply continuity and reports the fault.

[0018] Furthermore, the distributed electronic control system provides multiple steering modes through the main controller VCU and can be switched online. The multiple steering modes include: Ackermann front wheel steering mode, Ackermann four-wheel steering mode, crab steering mode, and stationary steering mode. When switching from Ackerman front-wheel steering mode and Ackerman four-wheel steering mode to crab steering mode and stationary steering mode, the current vehicle speed is first controlled to 0 before switching. When switching from crab steering mode and stationary steering mode to Ackerman front wheel steering mode and Ackerman four-wheel steering mode, first control the steering angle of all four wheels to 0° before switching.

[0019] Furthermore, the distributed electronic control system includes functional safety and degradation strategies, which specifically include: When a sensor failure is detected in a single steering module, each slave controller ECU executes a minor fault level one safety strategy. Specifically, the faulty steering module enters a holding angle or safe centering-brake state, and the kinematics of the other three wheels are reconstructed to complete a safe evacuation within the reachable range. When the master control communication is lost or a single power supply fails, each slave controller ECU executes a level 2 safety strategy for moderate faults, specifically: gradually decelerates, steers back to center and waits for manual takeover or remote recovery. When both the main and backup power supplies are detected to be out of power and the mechanical jamming cannot be resolved, each slave controller ECU executes a level three safety strategy for severe faults, specifically: emergency braking to stop.

[0020] Secondly, the present invention also discloses a control method for a steer-by-wire system of unmanned engineering machinery, comprising the following steps: S1. After the vehicle is powered on, the four steering modules simultaneously start a self-test program, which includes: each slave controller ECU first verifies the data consistency between the absolute encoder and the rotary transformer, confirming that the deviation of the motor rotor position fed back by the two is less than the preset threshold, and at the same time checks whether the resistance torque of the cycloidal reducer is within the normal threshold range when running under no-load; the dual power supply system is activated in parallel, and the voltage and current balance of the two power supplies are monitored in real time. If an abnormality is detected in one of the power supplies, the system immediately switches to the backup line to ensure that the system completes all hardware status confirmations within the preset time and feeds back a ready signal to the main controller VCU through the CAN FD bus; S2. Based on high-precision maps, GPS / IMU positioning, and LiDAR / camera data, plan a desired driving trajectory and send this trajectory signal to the main controller VCU. The main controller VCU can then select the optimal mode from the preset steering mode library based on the current vehicle status and the desired trajectory, and calculate the target turning angle of the four wheels in real time. S4. Through the CAN FD network, the target rotation angle commands of the four wheels calculated by the main controller are sent to the four slave controller ECUs respectively. After receiving the command, the slave controller ECU starts the high-precision position servo loop. First, it reads the feedback value of the encoder of the current wheel motor, calculates the actual rotation angle of the current wheel, and then calculates the deviation between the target rotation angle and the actual rotation angle. It generates a PWM signal to control the output torque and speed of the motor, directly drives the main pin shaft to rotate, and drives the wheel to deflect to the target angle. The system continuously monitors the current, angle error, and temperature of the permanent magnet synchronous servo motors of each axis. If it detects that the steering of a wheel is obstructed (i.e., the current exceeds the limit or the steering resistance torque exceeds the limit), it immediately reports to the main controller VCU so that the main controller VCU can replan the path or adjust the steering angle of other wheels for compensation. When a single steering module steering unit fails, its corresponding slave controller ECU will enter a safe state, and the main controller VCU will perform degraded steering control based on the remaining three normally operating steering modules. When the main controller VCU issues the parking path, the vehicle is parked in the designated position using Ackermann or crab-like methods; each slave controller ECU completes the angle return to center, and the axial flux permanent magnet synchronous servo motor enters the parking brake state.

[0021] The beneficial effects achieved by this invention are as follows: With four-wheel steering, the minimum turning radius can reach 0 meters, improving the unmanned sanitation sweeper's passability in narrow alleys, sidewalks, and areas with dense obstacles. Simultaneously, the independent control of each wheel steering wheel supports special motion patterns such as lateral translation and diagonal movement, increasing the sweeping path coverage. This is particularly suitable for high-precision operations such as cleaning along urban curbs. The steering module uses an axial flux servo motor directly connected to a cycloidal pinwheel reducer, resulting in a compact size, high output rigidity, and strong impact resistance, adapting to the high-frequency, low-speed, and high-resistance steering requirements of sanitation sweeping operations. The four steering modules are completely independent; if a single module fails, it can return to center or lock, and the remaining modules can reconstruct kinematics to achieve controllable withdrawal and degraded operation, providing fault-tolerant capability. The encoder, rotary transformer, and front-end torque sensor form a complete diagnostic chain, enabling jamming, collision detection, and torque limiting protection, reducing the risk of tire and mechanical component damage. During steering, differential coordination with the wheel hub motors ensures that the tire force aligns with the rolling direction, reducing tire lateral deviation and wear. Torque sensors detect changes in ground resistance in real time and adjust the steering angular velocity online, minimizing slippage on low-friction surfaces. In summary, employing four identical steering modules to achieve independent kingpin steering for all four wheels, combined with wheel hub motors and distributed redundant control, significantly improves system reliability, functional safety, and maintainability. This makes it particularly suitable for unmanned sanitation sweepers operating for extended periods in narrow, complex, and harsh environments. Attached Figure Description

[0022] Figure 1 This is a diagram of the steering module assembly; Figure 2 This is a schematic diagram of the steering module structure; Figure 3 This is a schematic diagram of the steering knuckle kingpin structure; Figure 4 This is a flowchart of the steering operation control process.

[0023] In the diagram: 1. Flux permanent magnet synchronous servo motor; 2. Cycloidal pinwheel reducer; 3. Bearing upper limit connector; 4. Bearing end cover; 5. Steering knuckle kingpin; 6. Bearing lower limit connector; 7. Cross roller bearing; 8. Output shaft. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0025] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] Example 1: This example describes a drive-by-wire steering system for unmanned engineering machinery, such as... Figures 1-3 As shown, it adopts four completely independent and structurally identical steering modules. The steering angle of the four wheels is controlled in a coordinated manner through a distributed electronic control system, which is particularly suitable for unmanned sanitation sweepers to carry out long-term sweeping operations in narrow, complex and harsh environments.

[0028] The rotation of the wheels of the unmanned sanitation sweeper is driven by hub motors. There is no drive shaft between the wheels and the vehicle body, meaning that each wheel can rotate 360° without any mechanical constraints.

[0029] The steering function of each wheel is achieved by an independent steering module. This module mainly includes the steering actuator and the steering knuckle kingpin.

[0030] The steering actuator consists of a high-power-density axial flux permanent magnet synchronous servo motor 1 and a cycloidal pinwheel reducer 2 directly coupled via a flange. The output shaft 8 of the steering motor is coaxially connected to the input end of the reducer via a key.

[0031] The steering knuckle kingpin 5 adopts a sleeve-type structure. Its inner ring connecting hole is bolted to the output flange of the steering actuator reducer, and its outer ring connecting hole is bolted to the steering knuckle. The steering actuator is installed in the steering knuckle kingpin sleeve through a crossed roller bearing 7 at its radial connection point. The entire steering movement is achieved by the steering motor directly driving the steering knuckle kingpin to rotate forward and backward through the reducer.

[0032] The connection structure between the steering knuckle kingpin and the cycloidal reducer also includes an upper bearing limit connector 3, a lower bearing limit connector 6, and a bearing end cap 4. The upper bearing limit connector 3 is fixed to the reducer housing by bolts, and the lower bearing limit connector 6 is fixed to the upper bearing limit connector 3 by bolts, thereby limiting the crossed roller bearing 7 to the transmission position of the steering knuckle kingpin 5. The bearing end cap 4 is fixed to the steering knuckle kingpin 5 by bolts for further sealing and protection.

[0033] At the tail end of the steering motor, a multi-turn absolute encoder is built in to accurately measure the position of the motor rotor to obtain the current wheel steering information.

[0034] A high-resolution rotary transformer is also installed in the steering motor to provide redundant position information.

[0035] The absolute encoder and rotary transformer of each module are converted into the current actual rotation angle signal. The information of the two are cross-validated in real time. If the rotation information of the two is greater than 0.2°, the current module is considered to be faulty.

[0036] The steering motor is equipped with a normally closed electromagnetic brake that automatically locks when power is lost.

[0037] A torque sensor is integrated at the front end of the cycloidal pinwheel reducer to monitor steering resistance torque in real time and achieve obstacle collision detection.

[0038] The distributed electronic control system adopts a master-slave architecture, consisting of a master controller (VCU), four slave controllers (ECUs), and a power supply.

[0039] The main controller (VCU) receives macroscopic path instructions from the autonomous driving controller and calculates the independent target steering angle and angular velocity instructions for the four wheels in real time based on the vehicle kinematics model. At the same time, it limits the angular velocity and acceleration based on the road adhesion coefficient estimation and the tire lateral slip model to avoid slipping on low-adhesion surfaces.

[0040] The four slave controller ECUs are dedicated steering ECUs for each steering module. They communicate with the master controller via high-speed CAN FD, are responsible for receiving the steering angle command of the current wheel, and driving the steering servo motor to realize the position servo closed-loop control of the wheel steering angle.

[0041] Four controller ECUs are integrated with the steering motor of each steering module.

[0042] The ECU features dual-channel position acquisition, torque sensing acquisition, and overcurrent / overtemperature / short-circuit protection. It executes position-speed-current cascade control and includes S-shaped acceleration / deceleration trajectory planning, friction compensation, and dead-zone compensation functions. The ECU maintains millisecond-level synchronization with the VCU to ensure consistent four-wheel coordination.

[0043] The power system provides dual independent power supplies to the VCU, each steering ECU and sensor. Both channels can carry the full load. In the event of a single channel failure, undervoltage or overvoltage, the system maintains power supply continuity and reports the fault.

[0044] The system offers multiple steering modes that can be switched online, including but not limited to: Ackermann front-wheel steering mode, Ackermann four-wheel steering mode, crab steering mode, and stationary steering mode. The VCU automatically selects or switches modes based on the work scenario and path requirements.

[0045] When switching from Ackermann steering mode to other steering modes, the current vehicle speed must be 0.

[0046] When switching from crab steering mode and stationary steering mode to Ackerman steering mode, the wheels must first be automatically aligned to ensure that the turning angle of all four wheels is 0°. The system possesses comprehensive functional safety and degradation strategies: dual-position sensor channel consistency criteria, torque mutation / static friction anomaly monitoring, communication timeout watchdog, power supply channel fault detection, and temperature deceleration control. When a single-module sensor fault is detected, each ECU executes a minor fault level one safety strategy, where the faulty module can enter a holding angle or safe return-to-center-brake state, while the other three wheels reconfigure their kinematics. If other steering modes are selected, a safe evacuation within the reachable range can continue. When main control communication is lost or a single power supply fails, each ECU executes a moderate fault level two safety strategy, gradually decelerating, steering back to center, and waiting for manual takeover or remote recovery. When both main and backup power supplies are lost, or mechanical jamming cannot be released, each ECU executes a severe fault level three safety strategy, implementing emergency braking to stop the vehicle.

[0047] The typical parameter range of this invention is: maximum output steering torque of a single module 600–1200 N·m, rated steering speed 60–90° / s, and positioning accuracy within ±0.2°; When each steering module performs a steering action while driving, it also performs electronic differential control on the rotation of the tires. Specifically, it calculates the linear speed of each wheel's rotation when steering based on the steering center position to avoid tire slippage and wear during steering.

[0048] Example 2: This example introduces a control method for a steer-by-wire system of unmanned engineering machinery, such as... Figure 4 As shown, it includes the following steps: S1 Power-On and Initialization: After the vehicle is powered on, the four steering modules simultaneously initiate self-test procedures. Each steering ECU first verifies the data consistency between the absolute encoder and the rotary transformer, confirming that the deviation of the motor rotor position fed back by both is less than 0.2°. Simultaneously, it checks whether the resistance torque of the cycloidal reducer during no-load operation is within the normal threshold range. The dual power supply system is activated in parallel, monitoring the voltage and current balance of the two power supplies in real time. If an anomaly is detected in either power supply, it immediately and seamlessly switches to the backup line, ensuring that the system completes all hardware status confirmations within 200 milliseconds and sends a ready signal back to the main controller via the CAN FD bus.

[0049] S2 Decision Layer Command Input: Based on high-precision maps, GPS / IMU positioning, and LiDAR / camera data, the autonomous driving system plans a desired driving trajectory and sends this trajectory signal to the vehicle main controller (VCU).

[0050] S3 Kinematics Calculation and Command Assignment: The VCU selects the optimal mode from the preset steering mode library based on the current vehicle status and the desired trajectory, and calculates the target steering angle of the four wheels in real time.

[0051] Ackermann front wheel steering mode: Steering while driving, based on Ackermann steering angle relationships, only the front wheels produce differential steering angles.

[0052] Ackermann four-wheel steering mode: Steering while driving, which causes the four wheels to produce different steering angles according to the Ackermann steering angle relationship.

[0053] Stationary turning mode: Used for U-turns in narrow spaces, where the line connecting the left front and right rear wheel axles intersects with the line connecting the right front and left rear wheel axles at a single point.

[0054] Crab mode: Used to move parallel to and close to a target area. The command is that all four wheels have the same target angle, and the vehicle moves horizontally along this angle.

[0055] S4 Distributed Closed-Loop Execution: The main controller sends four target rotation angle commands to the local ECUs of the four corner modules via the CAN FD network. After receiving the commands, the local ECUs activate the high-precision position servo loop. First, they read the feedback value from the encoder of the current wheel motor, calculate the actual rotation angle of the wheel, then calculate the deviation between the target rotation angle and the actual rotation angle, generate a PWM signal to control the output torque and speed of the motor, directly drive the main pin shaft to rotate, and cause the wheel to deflect to the target angle.

[0056] S5 Real-time Status Monitoring and Fault Tolerance: The system continuously monitors the current, steering angle error, and temperature of each steering motor. If steering resistance is detected at a wheel (i.e., current exceeds the limit or steering torque exceeds the limit), the system immediately reports to the main controller. The main controller can then replan the path or adjust the steering angle of other wheels to compensate. When a single steering module unit fails, its corresponding local ECU enters a safe state, and the main controller performs degraded steering control based on the remaining three normally functioning steering modules.

[0057] S6 Operation Completed and Parked: The VCU issues the parking path, and the vehicle is parked in the designated position using either an Ackermann or crab-like maneuver; each ECU completes angle centering. The steering motor enters the parking brake state. Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0058] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0059] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0060] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A drive-by-wire steering system for unmanned engineering machinery, characterized in that, include: Four wheels and a steering module that corresponds one-to-one with the four wheels, is completely independent and has the same structure; The steering angle deflection of the four wheels is controlled collaboratively by a distributed electronic control system. Each of the wheels is driven by a hub motor.

2. The unmanned engineering machinery steer-by-wire system according to claim 1, characterized in that, The steering module includes a steering actuator and a steering knuckle kingpin (5); The steering actuator includes an axial flux permanent magnet synchronous servo motor (1) and a cycloidal pinwheel reducer (2) that are directly coupled through a flange. The output shaft (8) of the axial flux permanent magnet synchronous servo motor (1) is coaxially connected to the input end of the cycloidal pinwheel reducer (2) by a key; The steering knuckle kingpin adopts a sleeve structure. The inner ring connecting hole of the sleeve structure is connected to the output flange of the cycloidal pinwheel reducer (2) by bolts. The outer ring connecting hole of the sleeve structure is connected to the steering knuckle by bolts. The steering actuator is installed in the sleeve of the steering knuckle kingpin through a cross roller bearing (7) at the radial connection of the sleeve structure.

3. The unmanned engineering machinery steer-by-wire system according to claim 2, characterized in that, The connection structure between the steering knuckle kingpin and the cycloidal reducer also includes an upper bearing limit connector (3), a lower bearing limit connector (6), and a bearing end cap (4). The upper limit connector (3) of the bearing is fixed to the housing of the cycloidal pinwheel reducer (2) by bolts. The lower limit connector (6) of the bearing is fixed to the upper limit connector (3) of the bearing by bolts, thereby limiting the cross roller bearing (7) to the transmission position of the steering knuckle kingpin (5). The bearing end cover (4) is fixed to the steering knuckle kingpin (5) by bolts.

4. The unmanned engineering machinery steer-by-wire system according to claim 2, characterized in that, At the tail end of the axial flux permanent magnet synchronous servo motor (1), a multi-turn absolute encoder is built in to measure the position of the motor rotor to obtain the current wheel steering information; The axial flux permanent magnet synchronous servo motor (1) is also equipped with a rotary transformer for providing redundant position information; The absolute encoder and rotary transformer of each steering module convert the current actual steering angle signal. The current actual steering angle signals of the two are cross-validated in real time. If the deviation of the motor rotor position fed back by the two is greater than the preset threshold, it is determined that there is a fault in the current steering module; otherwise, there is no fault.

5. The unmanned engineering machinery steer-by-wire system according to claim 2, characterized in that, The axial flux permanent magnet synchronous servo motor (1) is equipped with a normally closed electromagnetic brake, which automatically locks up when power is lost. A torque sensor for real-time monitoring of steering resistance torque is integrated at the front end of the cycloidal pinwheel reducer (2); When each steering module performs a steering action while driving, it also performs electronic differential control on the rotation of the tires. Specifically, it calculates the linear speed of the wheel rotation when each wheel is turning based on the steering center position.

6. The unmanned engineering machinery steer-by-wire system according to claim 1, characterized in that, The distributed electronic control system adopts a master-slave architecture, including a master controller VCU, four slave controllers ECUs and a power supply; each of the four slave controllers ECUs corresponds to a steering module, and each slave controller ECU is integrated with the axial flux permanent magnet synchronous servo motor (1) of each steering module; the slave controller ECU communicates with the master controller VCU through high-speed CAN FD, is responsible for receiving the steering angle command of the corresponding wheel, and drives the axial flux permanent magnet synchronous servo motor (1) to realize the position servo closed-loop control of the wheel steering angle; The main controller (VCU) receives macroscopic path instructions from the autonomous driving controller and calculates the independent target turning angle and angular velocity instructions for the four wheels in real time based on the vehicle kinematics model; at the same time, it limits the angular velocity and acceleration based on the road adhesion coefficient estimation and the tire lateral slip model.

7. The unmanned engineering machinery steer-by-wire system according to claim 6, characterized in that, The slave controller ECU has dual-channel position acquisition, torque sensing acquisition, and overcurrent / overtemperature / short circuit protection. It performs position-speed-current cascade control and has S-shaped acceleration / deceleration trajectory planning, friction compensation, and dead zone compensation functions. The slave controller ECU and the master controller VCU maintain millisecond-level time synchronization. The dual-channel position acquisition adopts a heterogeneous sensor redundancy architecture, including synchronous orthogonal signal acquisition of a rotary transformer and an absolute encoder, and realizes real-time verification and fault tolerance of dual-source data through a phase compensation algorithm. The power system provides dual independent power supplies to the main controller VCU, each slave controller ECU, and sensors. Both channels can carry the full load. In the event of a single channel failure, undervoltage, or overvoltage, the system maintains power supply continuity and reports the fault.

8. The unmanned engineering machinery steer-by-wire system according to claim 6, characterized in that, The distributed electronic control system provides multiple steering modes through the main controller VCU and can be switched online. The multiple steering modes include: Ackermann front wheel steering mode, Ackermann four-wheel steering mode, crab steering mode, and stationary steering mode. When switching from Ackerman front-wheel steering mode and Ackerman four-wheel steering mode to crab steering mode and stationary steering mode, the current vehicle speed is first controlled to 0 before switching. When switching from crab steering mode and stationary steering mode to Ackerman front wheel steering mode and Ackerman four-wheel steering mode, first control the steering angle of all four wheels to 0° before switching.

9. The unmanned engineering machinery steer-by-wire system according to claim 7, characterized in that, The distributed electronic control system includes functional safety and degradation strategies, which specifically include: When a sensor failure is detected in a single steering module, each slave controller ECU executes a minor fault level one safety strategy. Specifically, the faulty steering module enters a holding angle or safe centering-brake state, and the kinematics of the other three wheels are reconstructed to complete a safe evacuation within the reachable range. When the master control communication is lost or a single power supply fails, each slave controller ECU executes a level 2 safety strategy for moderate faults, specifically: gradually decelerates, steers back to center and waits for manual takeover or remote recovery. When both the main and backup power supplies are detected to be out of power and the mechanical jamming cannot be resolved, each slave controller ECU executes a level three safety strategy for severe faults, specifically: emergency braking to stop.

10. A control method for a steer-by-wire system for unmanned engineering machinery according to any one of claims 1-9, characterized in that, Includes the following steps: S1. After the vehicle is powered on, the four steering modules simultaneously start a self-test program, which includes: each slave controller ECU first verifies the data consistency between the absolute encoder and the rotary transformer, confirming that the deviation of the motor rotor position fed back by the two is less than the preset threshold, and at the same time checks whether the resistance torque of the cycloidal reducer is within the normal threshold range when running under no-load; the dual power supply system is activated in parallel, and the voltage and current balance of the two power supplies are monitored in real time. If an abnormality is detected in one of the power supplies, the system immediately switches to the backup line to ensure that the system completes all hardware status confirmations within the preset time and feeds back a ready signal to the main controller VCU through the CAN FD bus; S2. Based on high-precision maps, GPS / IMU positioning, and LiDAR / camera data, plan a desired driving trajectory and send this trajectory signal to the main controller VCU. The main controller VCU can then select the optimal mode from the preset steering mode library based on the current vehicle status and the desired trajectory, and calculate the target turning angle of the four wheels in real time. S4. Through the CAN FD network, the target rotation angle commands of the four wheels calculated by the main controller are sent to the four slave controller ECUs respectively. After receiving the command, the slave controller ECU starts the high-precision position servo loop. First, it reads the feedback value of the encoder of the current wheel motor, calculates the actual rotation angle of the current wheel, and then calculates the deviation between the target rotation angle and the actual rotation angle. It generates a PWM signal to control the output torque and speed of the motor, directly drives the main pin shaft to rotate, and drives the wheel to deflect to the target angle. The system continuously monitors the current, angle error, and temperature of the permanent magnet synchronous servo motors of each axis. If it detects that the steering of a wheel is obstructed (i.e., the current exceeds the limit or the steering resistance torque exceeds the limit), it immediately reports to the main controller VCU so that the main controller VCU can replan the path or adjust the steering angle of other wheels for compensation. When a single steering module steering unit fails, its corresponding slave controller ECU will enter a safe state, and the main controller VCU will perform degraded steering control based on the remaining three normally operating steering modules. When the main controller VCU issues the parking path, the vehicle is parked in the designated position using Ackermann or crab-like methods; each slave controller ECU completes the angle return to center, and the axial flux permanent magnet synchronous servo motor enters the parking brake state.

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