A distributed skid chassis multi-modal steering system and collaborative control method

Abstract

The distributed drive-by-wire chassis multi-mode steering system of the present application comprises an angle module integrated with a steering unit and an electronic control system, the electronic control system is in communication connection with each module in the angle module, and further comprises: a steering semi-decoupling unit, the steering semi-decoupling unit is connected with the steering unit, and comprises: a shell, a coupling execution motor, a power input worm, a coupling claw, a first steering tie rod, a second steering tie rod and a locking pin; the first steering tie rod partially extends into the shell; the second steering tie rod is slidably threaded through the shell; the coupling execution motor is installed in the shell, the power input worm is in transmission connection with the coupling execution motor; the locking pin is fixedly connected to the inner end of the second steering tie rod; the coupling claw is hinged to the shell or the first steering tie rod, and the coupling claw is in transmission connection with the power input worm through a worm gear tooth profile. The beneficial effect is that the underlying pain points of lack of high-speed stability when independent steering and lack of fault tolerance redundancy when single-point failure of the distributed drive-by-wire chassis are solved.

Description

Technical Field

[0001] This invention belongs to the field of automotive chassis structure and control technology, and particularly relates to a distributed drive-by-wire chassis multimodal steering system and a cooperative control method. Background Technology

[0002] With the rapid development of vehicle electrification and intelligence, vehicle chassis architecture is undergoing a profound transformation from traditional mechanical chassis to steer-by-wire chassis. Essentially, this is a topological shift from centralized mechanical rigid connections to distributed electronic flexible control. Early steer-by-wire systems eliminated the rigid mechanical connection between the steering wheel and the steering actuator, but the actuator still retained the centralized rack and pinion mechanism of the front axle. With the maturity of distributed drive technology, chassis architecture began to evolve towards modular designs. The core feature of this stage is the high integration of the drive motor, steer-by-wire caliper, and independent steering motor around the wheels. This complete physical decoupling breaks the physical constraints of traditional mechanical axles, providing each individual wheel with complete degrees of freedom of movement.

[0003] Early steer-by-wire systems eliminated the rigid mechanical connection between the steering wheel and the steering actuator, but the actuation end still retained the centralized rack and pinion mechanism of the front axle. With the maturity of distributed drive technology, chassis architecture began to evolve towards modular designs. The core feature of this stage was the high integration of the drive motor, brake-by-wire caliper, and independent steering motor around the wheels. This complete physical decoupling broke the physical constraints of traditional mechanical axles, providing each individual wheel with complete degrees of freedom of movement.

[0004] In existing distributed chassis technologies, the pursuit of ultimate handling performance (such as turning on the spot and driving at an angle) often requires the steering system and suspension unit to have higher independent execution capabilities. As the degree of system decoupling deepens, the contradiction between "flexibility" and "safety" becomes increasingly prominent. Fully independent steering is highly susceptible to wheel shimmy and left-right asynchrony at high speeds due to road disturbances or even minor control delays. More critically, a single point of electrical failure in a single corner module can trigger a serious risk of loss of control.

[0005] Chinese invention patent application CN119821506.B, entitled "Semi-decoupled Steering Tie Rod Structure and Execution Control Method for Full-Vector Chassis," discloses a special steering tie rod assembly that introduces a semi-decoupled system. During high-speed driving, the clutch engages, resolving the vehicle's loss of control caused by wheel shimmy and asynchrony between left and right wheels in fully decoupled steering. When the steering motor or driver of a certain corner module fails, the clutch engages, unifying the left and right wheels and maintaining tracking capability. Furthermore, this patent arranges the first and second racks in parallel, staggered configurations. The two racks do not interfere with each other during horizontal movement, allowing for a very large steering angle range. Simultaneously, the clutch is directly mounted between the two helical gears, minimizing the transmission path and reducing mechanical backlash, which improves the accuracy and response speed of the motor's closed-loop control. However, to maintain clutch engagement, the electromagnet must be continuously energized. This not only increases the vehicle's overall energy consumption, but the electromagnetic coils also generate heat during prolonged operation, affecting stability. If a serious electrical fault occurs and the vehicle experiences a sudden power outage, the left and right wheels will instantly decouple. Furthermore, the engagement force of the end face teeth depends on the magnetic attraction of the electromagnet or the preload of the spring. If the vehicle experiences a single motor failure while cornering at high speed or performing an emergency braking maneuver, the enormous lateral force may exceed the electromagnetic attraction, causing the teeth to slip or disengage, resulting in a fatal danger. Summary of the Invention

[0006] To address the shortcomings and challenges in the aforementioned background technology, this invention provides a distributed drive-by-wire chassis multimodal steering system and a cooperative control method, specifically implemented through the following technical solutions:

[0007] The distributed drive-by-wire chassis multimodal steering system includes an angle module integrating a wheel unit, suspension unit, drive unit, braking unit, and steering unit, and an electronic control system. The electronic control system is communicatively connected to each module in the angle module. The system is characterized by further including a steering semi-decoupling unit connected to the steering unit, comprising: a housing, a coupling actuator motor, a power input worm gear, a coupling pawl, a first steering tie rod, a second steering tie rod, and a locking pin. One end of the first steering tie rod is connected to the steering knuckle of the steering unit, and the other end is fixed to the housing and partially extends into the housing. One end of the second steering tie rod is connected to the steering knuckle of another steering unit, and the other end slidably passes through the housing, with the portion extending into the housing forming an inner end. The coupling actuator motor is mounted on the housing. Inside, the power input worm gear is rotatably supported within the housing and driven by the coupling actuator motor; the locking pin is fixed to the inner end of the second steering tie rod; the coupling claw is located within the housing and hinged to the housing or the first steering tie rod, the coupling claw having a worm gear tooth profile adapted to the power input worm gear and a hook-shaped locking end for engaging the locking pin, and is driven by the power input worm gear through the worm gear tooth profile; when the power input worm gear drives the coupling claw to rotate to the coupling position, the hook-shaped locking end engages the locking pin, and the second steering tie rod forms an axial limiting fit with the first steering tie rod or the housing through the locking pin, the coupling claw; when the power input worm gear drives the coupling claw to rotate to the decoupling position, the hook-shaped locking end disengages from the locking pin, causing the second steering tie rod to disengage from the first steering tie rod or the housing.

[0008] A further design of the distributed drive-by-wire chassis multimodal steering system is that the electronic control system includes:

[0009] The sensor group includes: a steering wheel angle sensor, a brake pedal displacement sensor, a resolver sensor, a wheel speed sensor, a six-axis inertial measurement unit, a chassis domain controller, a high-frequency phase current sensor, an absolute position encoder, a stator temperature sensor, a kingpin steering motor controller and Hall sensor, a coupled actuator motor current sensor, and a brake wheel cylinder pressure sensor.

[0010] An electronic control module is set up one-to-one with each corner module. The corner module electronic control module is communicatively connected to the drive unit, braking unit and steering unit in the corresponding corner module. It is used to collect information including wheel speed signal, steering motor position feedback signal, steering motor phase current signal, stator temperature signal and brake wheel cylinder pressure signal in the corresponding corner module, and output control signal including drive control signal, braking control signal and steering control signal of the corresponding corner module.

[0011] The signal analysis and intent reconstruction module calculates the vehicle's desired yaw rate and target deceleration based on signals from the steering wheel angle sensor and brake pedal displacement sensor; and outputs fault flags by analyzing data from the wheel speed sensor, six-axis inertial measurement unit, motor current, and resolver feedback to achieve fault diagnosis.

[0012] The core state machine decision logic module receives vehicle speed, fault flag and braking status information from the signal parsing module, and directly determines the opening and closing mode of the active coupler through the built-in finite state machine. In the event of an emergency, the state machine has a safety rewrite mechanism with the highest priority, which instantly issues a forced coupling command. If the normal braking performance is severely deteriorated, it will coordinate to control both wheels to turn into an inward position and immediately lock the coupler.

[0013] The collaborative execution and closed-loop module calculates the axial position deviation of the tie rod based on the feedback from the resolver sensor and controls the healthy side steering motor to perform small angle compensation.

[0014] The semi-decoupled actuator controller uses S-shaped trajectory planning to control the coupled actuator motor for decoupling and coupling operations; when a stall current spike is detected at the moment the coupling claw locks, the power supply to the coupled motor is cut off.

[0015] The fault-tolerant torque redistribution module redistributes the torque of the healthy motor after the underlying hardware fails and mechanical reconstruction is completed.

[0016] A further design of the distributed drive-by-wire chassis multimodal steering system is that the steering unit includes: a dual-winding steering motor, a reduction transmission mechanism, and a steering knuckle. The stator slot of the dual-winding steering motor has two sets of independent three-phase windings embedded in it, and the two sets of stator windings share the same permanent magnet rotor. The two sets of three-phase windings are powered and driven by independent inverters. The rotor output shaft of the dual-winding steering motor is connected to the steering knuckle through the reduction mechanism.

[0017] The present invention also provides a cooperative control method based on the distributed drive-by-wire chassis multimodal steering system, comprising the following steps:

[0018] Step 1) Establish an ideal linear two-degree-of-freedom vehicle dynamics model. Based on the obtained steering wheel angle and vehicle speed, calculate the current desired yaw rate and desired centroid sideslip angle to form an ideal yaw trajectory as the tracking target for upper-level control. Monitor the stator current of the two windings of the steering motor in real time using the state observer, and construct a current residual matrix as the current residual index. Set the fault triggering logic based on the current residual index to perform fault diagnosis.

[0019] Step 2) Based on the vehicle's current actual yaw rate and sideslip angle, plan the future trajectory of the vehicle and establish a standard quadratic cost function to track the ideal yaw trajectory;

[0020] Step 3) Establish a fuzzy inference mapping function to dynamically calculate the weight correction amount of the MPC cost function; and based on the constructed coupled triggering instruction triggering logic, execute the physical reconstruction and fault-tolerant takeover of the chassis according to the triggering logic;

[0021] Step 4) Establish hard constraints on the terminal position and velocity, and introduce the nonlinear friction characteristics of the worm gear into the prediction model to achieve zero impact at the moment of pawl engagement; construct the lower-level MPC actuator to establish the soft landing cost function, and perform soft landing control based on nonlinear friction feedforward and end velocity heavy penalty of MPC execution.

[0022] Step 5) Establish the dynamic model of the coupled vehicle, calculate the compensation torque required by the healthy side steering motor, and complete the fault-tolerant torque redistribution according to the dynamic model.

[0023] A further design of the cooperative control method is that step 1) specifically includes the following steps:

[0024] Step 1-1) Establish an ideal linear two-degree-of-freedom vehicle dynamics model according to equation (1);

[0025] (1)

[0026] In equation (1), Indicates the centroid sideslip angle. This represents the rate of change of the centroid's sideslip angle. Indicates yaw rate. Indicates yaw acceleration. Indicates the equivalent steering angle of the front axle. Indicates the overall vehicle weight. This represents the moment of inertia of the vehicle about its vertical axis. This represents the longitudinal distance from the vehicle's center of gravity to the center of the front axle. This indicates the longitudinal distance from the vehicle's center of gravity to the center of the rear axle. Indicates the longitudinal speed of the vehicle. Indicates the overall lateral stiffness of the front axle. This indicates the overall lateral stiffness of the rear axle;

[0027] Based on the obtained steering wheel angle and vehicle speed, calculate the vehicle's current desired yaw rate and desired sideslip angle. To form an ideal yaw trajectory as the tracking target for upper-level control;

[0028] Steps 1-2) Monitor the stator current of the two windings of the steering motor in real time using the state observer, and set the current residual matrix according to equation (2):

[0029] (2)

[0030] , for - Actual shaft current, , For the state observer Ideal or predicted current of the shaft. For current residual index, These represent the first and second sets of windings of the dual-winding steering motor, respectively.

[0031] The fault triggering logic is set according to formula (3), and the fault diagnosis is performed in real time according to the logic.

[0032] (3)

[0033] In equation (3), express Actual shaft current, express Ideal current of shaft,

[0034] This is a fault flag bit. This is the preset current residual threshold.

[0035] A further design of the cooperative control method is that step 2) specifically involves: based on the vehicle's current actual yaw rate and sideslip angle, establishing a standard quadratic cost function according to equation (4) to plan the future trajectory of the vehicle:

[0036] (4)

[0037] In equation (4), Indicates the current moment. Indicates the prediction time domain, Indicates control time domain, For the current moment For the future The vehicle state prediction vector of the step, The reference state vector corresponding to the ideal yaw trajectory. To control the increment, This is the state tracking error weight matrix. To control the incremental weight matrix, As slack variables, The penalty coefficient for slack variables,

[0038] According to equation (5), the weight matrix that changes in real time with the fuzzy controller is obtained, and the ideal yaw trajectory is tracked.

[0039] (5)

[0040] In equation (5), , These are the basic state error weight matrix and the basic control increment weight matrix, respectively. , These are the weight correction values ​​output by the fuzzy controller, and they satisfy... Otherwise, the fuzzy correction amount may cause the MPC cost function to lose its convexity or numerical stability.

[0041] A further design of the cooperative control method is that step 3) specifically includes the following steps:

[0042] Step 3-1) Establish the fuzzy inference mapping function according to equation (6) and dynamically calculate the weight correction amount of the MPC cost function;

[0043] (6)

[0044] In equation (6), , These are the adjustments for MPC state weights and control weights, respectively. For coupling triggering index, For vehicle speed, For yaw rate error, The observed value is the road surface adhesion coefficient.

[0045] The road surface adhesion coefficient is estimated based on unscented Kalman filtering according to equation (7):

[0046] (7)

[0047] In equation (7), This is the final output estimate of the optimal road surface adhesion coefficient. For the prior adhesion coefficient, For Kalman gain, The actual measurement value at the current moment. For predicting measurement values;

[0048] Step 3-2) Output continuous coupling trigger commands according to equation (8). When the safety threshold is crossed or a motor hardware failure signal is received, trigger the mechanical rigid lock command to realize the physical reconstruction and fault-tolerant takeover of the chassis.

[0049] (8)

[0050] In equation (8), This indicates that the coupling command is triggered. This indicates that the decoupling state is maintained. This is the coupling safety threshold.

[0051] A further design of the cooperative control method is that step 4) specifically includes the following steps:

[0052] Step 4-1) Establish the hard constraints on the terminal position and velocity shown in equation (9) to ensure the alignment and absolute stillness of the locking pin and coupling claw when the coupler engages:

[0053] (9)

[0054] In equation (9), This is the equivalent engagement position of the locking end of the coupling claw. To lock the position, The equivalent speed of the locking end of the coupling claw is given. To lock the pin speed, This refers to the relative position error of the terminal. This refers to the relative speed error of the terminals;

[0055] Based on equation (10), the dynamic equilibrium equation of the coupled motor, which includes the Stribeck nonlinear friction effect of the worm gear, is established.

[0056] (10)

[0057] In equation (10), This is the equivalent moment of inertia of the coupling mechanism referred to the motor shaft. To couple the motor rotation angle, Angular velocity, Angular acceleration, To couple the motor torque constant, To couple the motor current, For external load torque, The equivalent frictional torque of the worm gear mechanism.

[0058] The Stribeck friction model is:

[0059]

[0060] For the maximum static friction torque, The frictional torque is Coulomb torque. Stribeck characteristic velocity, The shape factor, The viscous damping coefficient is...

[0061] Step 4-2) Construct the lower-level MPC executor and establish the soft landing cost function according to equation (11):

[0062] (11)

[0063] In equation (10), To couple the predicted rotation angle of the motor, This refers to the target motor rotation angle when the coupling claw and locking pin are aligned. To couple the motor current increment, For location tracking weights, As the current increment weight, As the terminal shock suppression weight,

[0064] Soft landing control is performed using MPC based on nonlinear frictional feedforward and terminal velocity heavy penalty.

[0065] A further design of the cooperative control method is that, in step 5), equation (11) establishes the dynamic model of the coupled vehicle.

[0066] (12)

[0067] In equation (12), Represents the lumped equivalent moment of inertia of the system. , This represents the lumped equivalent viscous damping of the system. , This represents the lumped nonlinear Coulomb friction torque of the system. , Indicates the total tire return torque of the front axle. , Represents the total electromagnetic driving torque .

[0068] Beneficial technical effects:

[0069] The distributed drive-by-wire chassis multimodal steering system and cooperative control method of the present invention solve the underlying pain points of distributed drive-by-wire chassis lacking high-speed stability during independent steering and lacking fault-tolerant redundancy when a single point fails. At the same time, it specifically overcomes the fatal defects of existing redundancy decoupling schemes.

[0070] This system and method can not only rigidly connect the left and right wheels under extreme conditions such as high-speed driving and inward-pointing emergency braking to improve the overall rigidity and safety of the system, but also completely overcome the high power consumption and heat dissipation hazards caused by the need for continuous power supply to maintain engagement of traditional electromagnetic clutches.

[0071] The semi-decoupled steering unit used in this invention, with its mechanical reverse self-locking characteristics and extremely high shear resistance, can achieve high-strength absolute locking in a completely power-off state, avoiding the risk of accidental disengagement under severe chassis impact. Furthermore, with extremely high spatial integration, it perfectly replaces the bulky lateral arrangement of the traditional double parallel rack solution, ultimately achieving a perfect balance of low-speed agility, high-speed stability, extreme safety redundancy, and zero power consumption within a very small envelope space. Attached Figure Description

[0072] Figure 1 This is a three-dimensional structural diagram of a distributed drive-by-wire chassis multimodal steering system.

[0073] Figure 2 This is a schematic diagram of the wheel unit.

[0074] Figure 3 This is a schematic diagram of the steering unit.

[0075] Figure 4 This is a schematic diagram of the steering semi-decoupling unit.

[0076] In the diagram, 1-wheel unit, 11-tire, 12-wheel hub, 2-brake drive unit, 21-brake caliper, 22-brake disc, 23-wheel hub motor, 3-suspension unit, 31-damping strut, 32-upper control arm, 33-lower control arm, 4-steering unit, 41-dual-winding steering motor housing, 42-dual-winding steering motor, 43-reduction transmission mechanism, 44-steering knuckle, 5-steering semi-decoupling unit, 51-first steering tie rod, 52-housing, 53-second steering tie rod, 54-power input worm gear, 55-coupling pawl. Detailed Implementation

[0077] The following will refer to the appendices in the embodiments of the present invention. Figures 1-4 The technical solutions in the embodiments of the present invention will be clearly and completely described.

[0078] The distributed drive-by-wire chassis multimodal steering system of the present invention mainly consists of an angle module, a semi-decoupled steering unit, and an electronic control system.

[0079] like Figure 1 The corner module is specifically composed of: wheel unit 1, suspension unit 3, braking drive unit 2, and steering unit 4.

[0080] The wheel unit mainly consists of a flexible tire 11 and a hub 12. The hub 12 is located inside the tire 11 and includes a rim and spokes. The rim contacts the tire 11. A hub motor main shaft through hole is provided at the center of the spokes, and multiple mounting holes for mounting the hub drive motor are provided around it.

[0081] In this embodiment, the suspension unit 3 is arranged entirely inside the wheel and the drive / brake module, between the vehicle chassis and the core support base of the corner module. In terms of spatial orientation, it spans the entire height of the corner module in the vertical direction, forming the physical boundary and guide frame for the up-and-down movement of the wheel.

[0082] The suspension unit mainly consists of elastic shock absorbers and upper and lower control arms 32 and 33. The elastic shock absorber is an upright or inclined damping strut assembly. The top of the damping strut 31 is rigidly or flexibly fixed to the chassis or subframe via rubber bushings. The bottom end of the damping strut is typically fixed to the lower control arm via bolts or hinge points, transmitting vertical forces from the wheels to the vehicle body. The inner ends of the upper and lower control arms are rotatably connected to the chassis or subframe via hinge points such as rubber bushings; the outer ends of the upper and lower control arms are pivotally connected to the blue steering knuckle body via ball joints or other hinge points.

[0083] like Figure 2 In this embodiment, the braking drive unit 2 is integrally arranged within the internal space of the wheel rim. In the longitudinal layout, it is closely adjacent to and coaxially arranged with the drive motor, and the two are highly integrated. The braking unit is placed in the wheel unit and includes: brake disc 22, brake caliper 21, and brake pads.

[0084] The brake disc is mounted on the wheel and connected to the main shaft of the hub motor 23. The brake disc rotates synchronously with the wheel. The brake calipers are mounted on the motor housing and are located on both sides of the brake disc, on the same side of the wheel module as the brake disc. The brake pads are installed inside the brake calipers.

[0085] The hub drive motor 23 is located inside the wheel rim / hub and is highly integrated with the wheel. It includes a motor housing, an inner stator, and an outer rotor. The inner stator is located inside the motor housing. One end of the hub motor main shaft passes through the motor housing. The interior of the outer rotor is connected to the hub motor main shaft, and the exterior of the outer rotor is connected to the hub. One end of the hub motor main shaft is connected to the hub drive motor, and the other end is connected to the brake disc. The hub motor main shaft serves as a cooling channel for the brake module and the hub drive motor, allowing the central cooling water circuit to pass through.

[0086] like Figure 3 The steering unit 4 is arranged vertically in the inner core area of ​​the corner module, and the system is highly integrated on the pin axis established by the line connecting the outer hinge points of the upper and lower control arms of the suspension unit. The steering unit mainly consists of a dual-winding steering motor 41, a steering unit housing 42, and a reduction transmission mechanism 43, which ultimately acts on the steering knuckle 44.

[0087] In this embodiment, the stator slots of the dual-winding motor are embedded with two sets of independent three-phase windings, which are typically offset by 30° in space. Both sets of stator windings share the same permanent magnet rotor. The two sets of three-phase windings are powered and driven by two completely independent inverters. The stator of the motor is wound with two independent three-phase windings, forming double electrical redundancy at the hardware level. The steering motor is rigidly fixed to a non-deflection base bracket connected to the suspension. Its rotor output shaft extends downwards along the kingpin direction and connects to the reduction gear mechanism. The reduction gear mechanism, located between the motor and the steering knuckle, includes a planetary reduction mechanism. Its input end is coaxially connected to the motor rotor shaft, and its power output end is directly and mechanically rigidly fastened to the blue steering knuckle body. The steering knuckle is located at the outer end of the suspension unit. Its upper and lower ends are held and supported by the upper and lower connecting rods of the suspension unit through hinge points, thus positioning it in space and establishing the kingpin axis for deflection.

[0088] The steering semi-decoupling unit 5 in this embodiment mainly consists of a coupling actuator motor (not shown in the figure), a power input worm gear 54, a coupling pawl 55, a first steering tie rod 51, a second steering tie rod 53, and a housing 52. The coupling actuator motor is completely enclosed and installed inside the semi-transparent coupler housing, positioned directly above the power input worm gear. The power output shaft extends vertically downwards and is rigidly connected coaxially to the power input worm gear below. The motor and worm gear assembly are arranged on the side of the steering tie rod that passes through the housing.

[0089] In this embodiment, the coupling claw has an overall C-shaped or ear-shaped irregular structure. The lower half has a convex worm gear tooth profile machined on its arc-shaped outer edge. The upper half extends laterally and upwards, forming a hook-shaped locking end with an opening. A through pivot hole is provided at the other end (lower middle part) of the claw. The coupling claw is rotatably hinged to the end of the first steering tie rod inside the housing via a pivot pin, allowing it to swing in a fan-shaped motion at a certain angle in the vertical plane with this hole as the center. The lower worm gear tooth profile section meshes with a vertically arranged power input worm. The upper hook-shaped locking end is spatially aligned with the locking pin at the end of the second steering tie rod extending into the coupler. The driven component of the worm gear transmission pair receives high-speed rotational power from the motor and worm and converts it into a low-speed, high-torque, limited-angle oscillation around its pivot.

[0090] The outer end of the first steering tie rod extends towards the left side of the vehicle and is rotatably hinged to the steering knuckle body on the same side via a ball joint or other hinge components. The inner end extends horizontally towards the vehicle centerline and extends into the central active coupler housing. The inner end of the first steering tie rod serves as the load-bearing base of the active coupling mechanism, on which the aforementioned coupling actuator motor, power input worm gear, and coupling pawl, and other core control components are fixed, serving as a mechanical link for transmitting lateral displacement outward from the independent steering module on the same side.

[0091] The outer end of the second steering tie rod extends towards the other side of the vehicle and is also connected to the steering knuckle body on the opposite side via a hinge. The inner end extends towards the center of the vehicle and also extends into the central active coupler housing, and is in a parallel overlapping or coaxial guiding relative position relationship with the inner end of the first steering tie rod. At the end position extending into the coupler, the second steering tie rod is fixed with a dedicated force-bearing interface: a locking pin, which is spatially aligned with the hook-shaped opening of the coupling claw on the first steering tie rod.

[0092] The electronic control system in this embodiment mainly consists of: a sensor group, an electronic control module corresponding to each corner module, a signal analysis and intent reconstruction module, a core state machine decision logic module, a fault-tolerant torque redistribution module, and a semi-decoupled execution controller. Specifically, the sensor group includes: a steering wheel angle sensor, a brake pedal displacement sensor, a resolver sensor, wheel speed sensors, a six-axis inertial measurement unit, a chassis domain controller, a high-frequency phase current sensor, an absolute position encoder, a stator temperature sensor, a kingpin steering motor controller and Hall effect sensor, a coupled execution motor current sensor, and a brake wheel cylinder pressure sensor. The electronic control module collects information from each sensor in the sensor group and outputs control signals. The signal analysis and intent reconstruction module calculates the vehicle's desired yaw rate and target deceleration from the signals emitted by the steering wheel angle sensor and brake pedal displacement sensor; and by analyzing the data from the wheel speed sensor, the six-axis inertial measurement unit, and the motor current and resolver feedback, it outputs fault flags to achieve fault diagnosis. The core state machine decision logic module receives vehicle speed, fault flags, and braking status information from the signal analysis module. It directly determines the opening and closing mode of the active coupler through its built-in finite state machine. In emergency situations, the state machine has a high-priority safety rewrite mechanism, instantly issuing a forced coupling command. If a severe deterioration in conventional braking performance is assessed, it will coordinate the control of both wheels to turn inwards and immediately lock the coupler. The collaborative execution and closed-loop module calculates the axial position deviation of the tie rod based on feedback from the resolver sensor and controls the healthy side steering motor to perform minor angle compensation. The semi-decoupled execution controller uses S-shaped trajectory planning to control the coupled execution motor for decoupling and coupling operations. When a stall current spike is detected at the moment the coupling claw locks, the power supply to the coupled motor is cut off. The fault-tolerant torque redistribution module redistributes the torque of the healthy motor after underlying hardware failure and mechanical reconfiguration.

[0093] Furthermore, the semi-decoupled actuator controller, via commands from the chassis domain controller, primarily includes decoupled and coupled states. When the steering semi-decoupled unit is in the decoupled state, the coupled actuator motor receives a command and drives its output shaft to rotate the power input worm gear in a preset positive direction. The worm gear's rotation, through tooth meshing, drives the gear sector coupling pawl to swing upwards around its pivot axis. The hook-shaped opening at the upper end of the pawl is fully raised, completely disengaging from and avoiding the locking pin at the end of the second steering tie rod on the opposite side. At this time, the first and second steering tie rods are axially freed from all mechanical constraints, allowing the two rods to slide freely relative to each other within the coupler housing. The steering angles of the left and right wheels of the vehicle are completely driven independently by the steering units within their respective angle modules, without interference, achieving pure full-vector independent steering control.

[0094] When the steering semi-decoupled unit is in the coupled state, the coupling actuator motor is rapidly energized, driving the power input worm gear to rotate at high speed in the opposite direction. The reverse rotation of the worm gear causes the coupling pawl to swing downwards. The hook-shaped opening at the upper end of the pawl precisely engages downwards, firmly gripping the locking pin at the end of the second steering tie rod, eliminating the relative play between them. Instantly, the previously disconnected first and second steering tie rods are rigidly connected into a single, continuous tie rod. In the redundant scenario of single-sided steering failure, the torque output by the healthy steering motor on the unaffected side not only drives the wheel on that side to deflect but also, through this rigidly locked tie rod, mechanically drags or pushes the steering knuckle on the failed side to achieve synchronous deflection, thus ensuring that the vehicle does not lose its steering capability at the physical level.

[0095] This invention also provides a cooperative control method based on a distributed drive-by-wire chassis multimodal steering system, comprising the following steps:

[0096] Step 1) Establish an ideal linear two-degree-of-freedom vehicle dynamics model according to equation (1);

[0097] (1)

[0098] In equation (1), Indicates the centroid sideslip angle. This represents the rate of change of the centroid's sideslip angle. Indicates yaw rate. Indicates yaw acceleration. Indicates the equivalent steering angle of the front axle. Indicates the overall vehicle weight. This represents the moment of inertia of the vehicle about its vertical axis. This represents the longitudinal distance from the vehicle's center of gravity to the center of the front axle. This indicates the longitudinal distance from the vehicle's center of gravity to the center of the rear axle. Indicates the longitudinal speed of the vehicle. Indicates the overall lateral stiffness of the front axle. This indicates the overall lateral stiffness of the rear axle;

[0099] Based on the obtained steering wheel angle and vehicle speed, calculate the vehicle's current desired yaw rate. Desired centroid side slip angle To form an ideal yaw trajectory as the tracking target for upper-level control;

[0100] The obtained road adhesion coefficient observation value As input to the subsequent fuzzy controller, it is used to dynamically correct the state tracking error weight, control increment weight, and coupling trigger threshold in the MPC cost function. When the road adhesion coefficient decreases, the system increases the tracking weights of yaw rate and centroid sideslip angle, and decreases the coupling trigger threshold of the steering semi-decoupling unit, so that the vehicle preferentially enters the highly stable coupled steering mode under low adhesion conditions.

[0101] The current residual matrix is ​​set according to the equation (2) based on the real-time monitoring of the stator current of the two windings of the steering motor by the state observer. :

[0102] (2)

[0103] The fault triggering logic is set according to formula (3), and the fault diagnosis is performed in real time according to the logic.

[0104] (3)

[0105] In equation (3), express Actual shaft current, express Ideal current of shaft, This represents the preset fault diagnosis residual threshold. The preset current residual threshold is used;

[0106] Step 2) Based on the vehicle's current actual yaw rate and sideslip angle, establish a standard quadratic cost function according to equation (4) to plan the future trajectory of the vehicle:

[0107] (4)

[0108] In equation (4), Indicates the current moment. Indicates the prediction time domain, Indicates control time domain, For the current moment For the future The vehicle state prediction vector of the step, The reference state vector corresponding to the ideal yaw trajectory. To control the increment, This is the state tracking error weight matrix. To control the incremental weight matrix, As slack variables, The penalty coefficient for slack variables,

[0109] According to equation (5), the weight matrix that changes in real time with the fuzzy controller is obtained, and the ideal yaw trajectory is tracked.

[0110] (5)

[0111] In equation (5), , These are the basic state error weight matrix and the basic control increment weight matrix, respectively. and This represents the adaptive weight adjustment amount.

[0112] Step 3) Establish the fuzzy inference mapping function according to equation (6) and dynamically calculate the weight correction amount of the MPC cost function;

[0113] (6)

[0114] In equation (6), , These are the adjustments for MPC state weights and control weights, respectively. For coupling triggering index, For vehicle speed, For yaw rate error, This represents the observed value of the road surface adhesion coefficient.

[0115] Since road surface adhesion conditions directly affect the tire lateral force limit and vehicle yaw stability margin, independent steering mode is more likely to cause asynchronous steering angles between the left and right wheels and a decrease in vehicle stability on low-adhesion surfaces. Therefore, this embodiment uses the road surface adhesion coefficient as a key environmental state variable for multimodal steering control, which is used for subsequent MPC weight adjustment and coupling mode determination.

[0116] Estimation of road surface adhesion coefficient based on unscented Kalman filtering:

[0117] ,

[0118] This is the final output estimate of the optimal road surface adhesion coefficient. For the prior adhesion coefficient, For Kalman gain, The actual measurement value at the current moment. For predicting measurement values.

[0119] According to equation (7), a continuous coupling trigger command is output. When the safety threshold is crossed or a motor hardware failure signal is received, a mechanical rigid lock command is triggered to realize the physical reconstruction and fault-tolerant takeover of the chassis.

[0120] (7)

[0121] In equation (7), This indicates that the coupling command is triggered. This indicates that the decoupling state is maintained. This is the coupling safety threshold.

[0122] Step 4) Use the terminal position and velocity hard constraints shown in equation (8) to ensure that the locking pin and coupling claw are aligned and absolutely stationary when the coupler engages:

[0123] (8)

[0124] In equation (8), This is the equivalent engagement position of the locking end of the coupling claw. To lock the position, The equivalent speed of the locking end of the coupling claw is given. To lock the pin speed, This refers to the relative position error of the terminal. This represents the relative speed error of the terminal.

[0125] To achieve zero impact at the moment of chuck engagement, the nonlinear friction characteristics of the worm gear are introduced into the prediction model. Based on equation (9), the coupled motor dynamic balance equation of the dynamic prediction model including the Stribeck nonlinear friction effect of the worm gear is established.

[0126] (9)

[0127] In equation (9), This represents the equivalent moment of inertia of the coupling mechanism referred to the motor shaft. Indicates the angular acceleration of the motor. This represents the electromagnetic torque output by the motor. Indicates the external load torque. This represents the Stribeck model.

[0128] Based on equation (10), construct the lower-level MPC executor to establish the soft landing cost function:

[0129] (10)

[0130] In equation (10), To predict the time domain, To control the time domain, To couple the predicted rotation angle of the motor, This refers to the target motor rotation angle when the coupling claw and locking pin are aligned. To couple the motor current increment, For location tracking weights, As the current increment weight, This is the terminal shock suppression weight.

[0131] A soft landing control method based on nonlinear frictional feedforward and terminal velocity heavy penalty;

[0132] Step 5) After the steering semi-decoupling unit completes the mechanical coupling, the left and right front wheel steering mechanisms change from an independent execution state to an equivalent single-degree-of-freedom synchronous steering state. Therefore, a coupled lumped dynamic model is established to calculate the compensation torque required by the healthy side steering motor and complete the fault-tolerant torque redistribution. A coupled vehicle dynamic model is established according to equation (11).

[0133] (11)

[0134] In equation (11), Represents the lumped equivalent moment of inertia of the system. , This represents the lumped equivalent viscous damping of the system. , This represents the lumped nonlinear Coulomb friction torque of the system. , Indicates the total tire return torque of the front axle. , Represents the total electromagnetic driving torque .

[0135] This invention has many specific applications. The above description is only a preferred embodiment of this invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of this invention, and these improvements should also be considered within the scope of protection of this invention.

Claims

1. A distributed drive-by-wire chassis multimodal steering system, comprising an angle module integrating a wheel unit, a suspension unit, a drive unit, a braking unit, and a steering unit, and an electronic control system, wherein the electronic control system is communicatively connected to each module in the angle module, characterized in that... Also includes: A semi-decoupled steering unit, connected to the steering unit, includes: a housing, a coupling actuator motor, a power input worm gear, a coupling pawl, a first steering tie rod, a second steering tie rod, and a locking pin; One end of the first steering tie rod is connected to the steering knuckle of the steering unit, and the other end is fixed to the housing and partially extends into the housing; one end of the second steering tie rod is connected to the steering knuckle of another steering unit, and the other end slidably passes through the housing, with the portion extending into the housing forming an inner end; the coupling actuator motor is installed inside the housing, and the power input worm gear is rotatably supported inside the housing and driven by the coupling actuator motor; the locking pin is fixed to the inner end of the second steering tie rod; the coupling pawl is located inside the housing and hinged to the housing or the first steering tie rod, coupling... The coupling claw has a worm gear profile adapted to the power input worm and a hook-shaped locking end for engaging the locking pin. It is connected to the power input worm through the worm gear profile. When the power input worm drives the coupling claw to rotate to the coupling position, the hook-shaped locking end engages the locking pin, and the second steering tie rod forms an axial limiting fit with the first steering tie rod or the housing through the locking pin, the coupling claw, and the second steering tie rod. When the power input worm drives the coupling claw to rotate to the decoupling position, the hook-shaped locking end disengages from the locking pin, thereby disengaging the second steering tie rod from the first steering tie rod or the housing.

2. The distributed drive-by-wire chassis multimodal steering system according to claim 1, characterized in that... The electronic control system includes: The sensor group includes: a steering wheel angle sensor, a brake pedal displacement sensor, a resolver sensor, a wheel speed sensor, a six-axis inertial measurement unit, a chassis domain controller, a high-frequency phase current sensor, an absolute position encoder, a stator temperature sensor, a kingpin steering motor controller and Hall sensor, a coupled actuator motor current sensor, and a brake wheel cylinder pressure sensor. An electronic control module is set up one-to-one with each corner module. The corner module electronic control module is communicatively connected to the drive unit, braking unit and steering unit in the corresponding corner module. It is used to collect information including wheel speed signal, steering motor position feedback signal, steering motor phase current signal, stator temperature signal and brake wheel cylinder pressure signal in the corresponding corner module, and output control signal including drive control signal, braking control signal and steering control signal of the corresponding corner module. The signal analysis and intent reconstruction module calculates the vehicle's desired yaw rate and target deceleration based on signals from the steering wheel angle sensor and brake pedal displacement sensor; and outputs fault flags by analyzing data from the wheel speed sensor, six-axis inertial measurement unit, motor current, and resolver feedback to achieve fault diagnosis. The core state machine decision logic module receives vehicle speed, fault flag and braking status information from the signal parsing module, and directly determines the opening and closing mode of the active coupler through the built-in finite state machine. In the event of an emergency, the state machine has a safety rewrite mechanism with the highest priority, which instantly issues a forced coupling command. If the normal braking performance is severely deteriorated, it will coordinate to control both wheels to turn into an inward position and immediately lock the coupler. The collaborative execution and closed-loop module calculates the axial position deviation of the tie rod based on the feedback from the resolver sensor and controls the healthy side steering motor to perform small angle compensation. The semi-decoupled actuator controller uses S-shaped trajectory planning to control the coupled actuator motor for decoupling and coupling operations; when a stall current spike is detected at the moment the coupling claw locks, the power supply to the coupled motor is cut off. The fault-tolerant torque redistribution module redistributes the torque of the healthy motor after the underlying hardware fails and mechanical reconstruction is completed.

3. The distributed drive-by-wire chassis multimodal steering system according to claim 1, characterized in that... The steering unit includes a dual-winding steering motor, a reduction transmission mechanism, and a steering knuckle. The stator slot of the dual-winding steering motor has two sets of independent three-phase windings embedded in it, and the two sets of stator windings share the same permanent magnet rotor. The two sets of three-phase windings are powered and driven by independent inverters. The rotor output shaft of the dual-winding steering motor is connected to the steering knuckle through the reduction mechanism.

4. A cooperative control method based on the distributed drive-by-wire chassis multimodal steering system according to any one of claims 1-3, comprising the following steps: Step 1) Establish an ideal linear two-degree-of-freedom vehicle dynamics model. Based on the obtained steering wheel angle and vehicle speed, calculate the current desired yaw rate and desired centroid sideslip angle to form an ideal yaw trajectory as the tracking target for upper-level control. Monitor the stator current of the two windings of the steering motor in real time using the state observer, and construct a current residual matrix as the current residual index. Set the fault triggering logic based on the current residual index to perform fault diagnosis. Step 2) Based on the vehicle's current actual yaw rate and sideslip angle, plan the future trajectory of the vehicle and establish a standard quadratic cost function to track the ideal yaw trajectory; Step 3) Establish a fuzzy inference mapping function to dynamically calculate the weight correction amount of the MPC cost function; and based on the constructed coupled triggering instruction triggering logic, execute the physical reconstruction and fault-tolerant takeover of the chassis according to the triggering logic; Step 4) Establish hard constraints on the terminal position and velocity, and introduce the nonlinear friction characteristics of the worm gear into the prediction model to achieve zero impact at the moment of pawl engagement; construct the lower-level MPC actuator to establish the soft landing cost function, and perform soft landing control based on nonlinear friction feedforward and end velocity heavy penalty of MPC execution. Step 5) Establish the dynamic model of the coupled vehicle, calculate the compensation torque required by the healthy side steering motor, and complete the fault-tolerant torque redistribution according to the dynamic model.

5. The cooperative control method according to claim 4, characterized in that... Step 1) specifically includes the following steps: Step 1-1) Establish an ideal linear two-degree-of-freedom vehicle dynamics model according to equation (1); (1) In equation (1), Indicates the centroid sideslip angle. This represents the rate of change of the centroid's sideslip angle. Indicates yaw rate. Indicates yaw acceleration. Indicates the equivalent steering angle of the front axle. Indicates the overall vehicle weight. This represents the moment of inertia of the vehicle about its vertical axis. This represents the longitudinal distance from the vehicle's center of gravity to the center of the front axle. This indicates the longitudinal distance from the vehicle's center of gravity to the center of the rear axle. Indicates the longitudinal speed of the vehicle. Indicates the overall lateral stiffness of the front axle. This indicates the overall lateral stiffness of the rear axle; Based on the obtained steering wheel angle and vehicle speed, calculate the vehicle's current desired yaw rate and desired sideslip angle. To form an ideal yaw trajectory as the tracking target for upper-level control; Steps 1-2) Monitor the stator current of the two windings of the steering motor in real time using the state observer, and set the current residual matrix according to equation (2): （2） , for - Actual shaft current, , For the state observer Ideal or predicted current of the shaft. For current residual index, These represent the first and second sets of windings of the dual-winding steering motor, respectively. The fault triggering logic is set according to formula (3), and the fault diagnosis is performed in real time according to the logic. （3） In equation (3), express Actual shaft current, express Ideal current of shaft, This is a fault flag bit. This is the preset current residual threshold.

6. The cooperative control method according to claim 5, characterized in that... Step 2) specifically involves: based on the vehicle's current actual yaw rate and sideslip angle, establishing a standard quadratic cost function to plan the future trajectory of the vehicle according to equation (4): （4） In equation (4), Indicates the current moment. Indicates the prediction time domain, Indicates control time domain, For the current moment For the future The vehicle state prediction vector of the step, This is the reference state vector corresponding to the ideal yaw trajectory. To control the increment, This is the state tracking error weight matrix. To control the incremental weight matrix, As slack variables, The penalty coefficient for slack variables, According to equation (5), the weight matrix that changes in real time with the fuzzy controller is obtained, and the ideal yaw trajectory is tracked. （5） In equation (5), , These are the basic state error weight matrix and the basic control increment weight matrix, respectively. , These are the weight correction values ​​output by the fuzzy controller, and they satisfy... Otherwise, the fuzzy correction amount may cause the MPC cost function to lose its convexity or numerical stability.

7. The collaborative control method according to claim 6, characterized in that... Step 3) specifically includes the following steps: Step 3-1) Establish the fuzzy inference mapping function according to equation (6) and dynamically calculate the weight correction amount of the MPC cost function; （6） In equation (6), , These are the adjustments for MPC state weights and control weights, respectively. For coupling triggering index, For vehicle speed, For yaw rate error, This refers to the observed value of the road surface adhesion coefficient; The road surface adhesion coefficient is estimated based on unscented Kalman filtering according to equation (7): (7) In equation (7), This is the final output estimate of the optimal road surface adhesion coefficient. For the prior adhesion coefficient, For Kalman gain, The actual measurement value at the current moment. For predicting measurement values; Step 3-2) Output continuous coupling trigger commands according to equation (8). When the safety threshold is crossed or a motor hardware failure signal is received, trigger the mechanical rigid lock command to realize the physical reconstruction and fault-tolerant takeover of the chassis. （8） In equation (8), This indicates that the coupling command is triggered. This indicates that the decoupling state is maintained. This is the coupling safety threshold.

8. The cooperative control method according to claim 7, characterized in that... Step 4) specifically includes the following steps: Step 4-1) Establish the hard constraints on the terminal position and velocity shown in equation (9) to ensure the alignment and absolute stillness of the locking pin and coupling claw when the coupler engages: （9） In equation (9), This is the equivalent engagement position of the locking end of the coupling claw. To lock the position, The equivalent speed of the locking end of the coupling claw is given. To lock the pin speed, This refers to the relative position error of the terminal. This refers to the relative speed error of the terminals; Based on equation (10), the dynamic equilibrium equation of the coupled motor, which includes the Stribeck nonlinear friction effect of the worm gear, is established. （10） In equation (10), This is the equivalent moment of inertia of the coupling mechanism referred to the motor shaft. To couple the motor rotation angle, Angular velocity, Angular acceleration, To couple the motor torque constant, To couple the motor current, For external load torque, The equivalent frictional torque of the worm gear mechanism. The Stribeck friction model is: In the formula, For the maximum static friction torque, The frictional torque is Coulomb torque. Stribeck characteristic velocity, The shape factor, The viscous damping coefficient is... Step 4-2) Construct the lower-level MPC executor and establish the soft landing cost function according to equation (11): （11） In equation (10), To couple the predicted rotation angle of the motor, This refers to the target motor rotation angle when the coupling claw and locking pin are aligned. To couple the motor current increment, For location tracking weights, As the current increment weight, As the terminal shock suppression weight, Soft landing control is performed using MPC based on nonlinear frictional feedforward and terminal velocity heavy penalty.

9. The cooperative control method according to claim 8, characterized in that... Step 5) Establish the dynamic model of the coupled vehicle using formula (11). （12） In equation (12), Represents the lumped equivalent moment of inertia of the system. , This represents the lumped equivalent viscous damping of the system. , This represents the lumped nonlinear Coulomb friction torque of the system. , Indicates the total tire return torque of the front axle. , Represents the total electromagnetic driving torque .

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