Integrated kingpin steering system and control method thereof

Abstract

The invention discloses an integrated kingpin steering system and a control method thereof. The control method comprises the steps that a kinetic model of the integrated kingpin steering system is established; performing reversibility analysis on the dynamical model of the integrated kingpin steering system; a neural network inverse method is adopted to decouple the integrated kingpin steering system into a linear system, and four linear subsystems are obtained; and a PID tracking controller is designed to control the four linear subsystems obtained through decoupling so as to control the vehicle to achieve steering, driving, braking and vibration reduction. The fixed master pin does not rotate along with the wheels any more, does not bear torque during steering and only bears vertical bending moment caused by different stress of the upper-section fixed master pin and the lower-section fixed master pin and lateral bending moment caused by lateral force of the wheels, design is simplified, and the bearing capacity of the fixed master pin is improved. According to the invention, the control precision of the rotation angle, the driving force, the braking force, the linear thrust and the like of each subsystem is improved, and the control performance of dynamic response smoothness and the like of the system is enhanced.

Description

Technical Field

[0001] The present invention belongs to the field of integrated and steering of intelligent steer-by-wire chassis for electric vehicles, and particularly relates to an integrated kingpin steering system and a control method thereof. Background Art

[0002] With the development of intelligent connected and autonomous driving vehicle technologies, the chassis control of modern vehicles is no longer limited to the separate control of traditional drive systems, suspension systems, braking systems, and steering systems. A more intelligent and shared high-mobility vehicle chassis has become a hot topic in the industry. In particular, a steering angle module integrating technologies such as integrated electric drive, steer-by-wire, brake-by-wire, and chassis suspension has become an ideal modular solution.

[0003] The drive-steering integrated angle module highly integrates components such as drive, brake, steering, and suspension. A single angle module can achieve functions such as drive, steering, braking, load-bearing, and vibration damping, which can reduce a large number of mechanical transmission components, optimize the overall vehicle layout space, enable each wheel to rotate independently, and thus make the vehicle turn and move more flexibly, greatly expanding the control boundary of the vehicle chassis, enabling the vehicle to exhibit excellent handling and adaptability under various complex road surfaces and working conditions, and effectively improving vehicle performance such as power performance, economy, ride comfort, braking performance, and handling stability.

[0004] However, although the existing vehicle angle module reduces the occupied space of a part of the steering mechanical structure in the vehicle's front cabin and improves the vehicle's collision safety, in order to accommodate a larger steering angle, the size of the angle module components themselves and the additional space required during the movement process also increase accordingly, causing the angle module to occupy more space in the vertical direction of the vehicle, thus affecting the overall layout and space utilization of the vehicle.

[0005] In the Chinese invention patent application with the application number CN202311448022.X and the title "An Angle Module and a Vehicle", the steering drive assembly, steering execution assembly of the steering system and the wheel steering shaft are highly integrated, and the intermediate steering transmission structure such as the transmission arm is also omitted, making the physical integration degree of the angle module components higher and the structure more compact, effectively reducing the space occupied by the angle module in the whole vehicle. However, the relationship between the kingpin and the output shaft of the steering motor is vertical, and this layout occupies lateral space. At the same time, the kingpin is directly connected to the wheel to drive the wheel to rotate, so the kingpin itself needs to bear bending torque. In terms of the bearing mechanism, this solution does not use a steering knuckle, but directly lets the kingpin bear the bending torque, and the problem of insufficient bearing capacity needs to be considered, and there are certain limitations in terms of bearing and space utilization.

[0006] The Chinese invention patent application number CN202410557892.9 entitled “Wheel angle module with integrated controllable kingpin and kingpin steering” discloses an integrated wheel assembly, steering system, suspension system and variable kingpin inclination angle system, with the functions of kingpin steering and active adjustment of kingpin inclination angle. However, due to the limited space near the suspension, a large steering motor cannot be arranged, which creates certain difficulties for its promotion and application. Summary of the invention

[0007] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide an integrated kingpin steering system and a control method thereof, so as to solve the problems in the prior art that the kingpin and the steering motor output shaft are vertically arranged to occupy the lateral space of the vehicle and the kingpin directly bears the bending torque and has poor bearing capacity, as well as the complex coupling relationship between the various subsystems in the existing system, which leads to the inaccurate control effects of the turning angle, driving force, braking force, and linear thrust, and the control performance such as the dynamic response smoothness of the system cannot be taken into account.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] An integrated kingpin steering system of the present invention comprises: a wheel module, a suspension module, a steering module, a brake module and an electronic control unit;

[0010] The wheel module comprises: a wheel hub, a wheel hub motor spindle and a wheel hub drive motor;

[0011] The wheel hub is arranged inside the tire and comprises a rim and a spoke. The rim contacts the tire. A hub motor spindle through hole is arranged at the center of the spoke, and a plurality of mounting holes for mounting the hub drive motor are arranged around the spoke.

[0012] One end of the hub motor spindle is connected to the hub drive motor, and the other end is connected to the brake disc. The hub motor spindle serves as a cooling channel for the brake module and the hub drive motor, allowing the central cooling water channel to pass through;

[0013] The wheel hub drive motor is arranged in the wheel hub, and comprises a motor housing, an inner stator and an outer rotor. The inner stator is arranged inside the motor housing, one end of the wheel hub motor main shaft passes through the motor housing, the inner part of the outer rotor is connected to the wheel hub motor main shaft, and the outer part of the outer rotor is connected to the wheel hub;

[0014] The suspension module comprises: a swing arm and a shock absorber assembly;

[0015] The swing arm comprises an upper swing arm and a lower swing arm, wherein the intersection end of two cross arms of the upper swing arm is connected to the steering module, and the forked ends of two cross arms of the upper swing arm are connected to the vehicle body / frame; the intersection end of two cross arms of the lower swing arm is connected to the steering module, and the forked ends of two cross arms of the lower swing arm are connected to the vehicle body / frame;

[0016] A shock absorber assembly, comprising: a spring, a linear motor, and a suspension support arm. The stator of the linear motor is connected to the spring. The mover of the linear motor is movably disposed within the stator along the axis of the stator. The upper end of the mover is connected to the vehicle body / frame, and the lower end of the mover is connected to the suspension support arm. The spring is connected to the stator of the linear motor, and the arrangement axis of the spring coincides with that of the linear motor.

[0017] The steering module includes: an integrated steering assembly and a fixed kingpin.

[0018] The integrated steering assembly includes: a steering motor, a steering reduction device, and an integrated floating knuckle.

[0019] The steering motor is disposed within the integrated floating knuckle.

[0020] The steering reduction device includes: a sun gear, planet gears, a planet carrier, and an internal gear ring. The sun gear is fixed as the main pinion gear on the lower fixed kingpin of the fixed kingpin. The sun gear is respectively connected to the planet gears and the planet carrier. The planet gears are connected to the output shaft of the steering motor, and the planet gears rotate synchronously with the steering motor, causing the planet carrier to rotate around the sun gear.

[0021] The integrated floating knuckle integrates the knuckle and the steering motor housing, and the integrated floating knuckle integrates the design of the knuckle and the steering motor housing.

[0022] The steering motor outputs torque to the steering reduction device. After being decelerated and torque-increased by the steering reduction device, it is output downward through the integrated floating knuckle, causing the integrated floating knuckle to rotate around the fixed kingpin. The middle part of the integrated floating knuckle is connected to the vehicle wheel, thereby driving the vehicle wheel to steer.

[0023] The fixed kingpin includes: an upper fixed kingpin and a lower fixed kingpin.

[0024] The upper fixed kingpin is connected to the upper end of the integrated floating knuckle, and the lower fixed kingpin is connected to the lower end of the integrated floating knuckle through a ball joint. The integrated floating knuckle rotates around the axis of the lower fixed kingpin, thereby driving the vehicle to steer.

[0025] The brake module is disposed within the wheel module and includes: a brake disc, a brake caliper, and brake pads.

[0026] The brake disc is disposed on the wheel and is connected to the main shaft of the in-wheel motor. The brake disc rotates synchronously with the wheel.

[0027] The brake caliper is disposed on the motor housing and is located on both sides of the brake disc and on the same side of the wheel module as the brake disc.

[0028] The brake pads are installed inside the brake caliper.

[0029] The electronic control unit includes: four electronic control modules, each of which is simultaneously connected to a steering motor and a wheel angle sensor, a hub drive motor and a torque sensor, a braking module and a braking force sensor, and a linear motor and a linear thrust sensor;

[0030] The electronic control module receives the desired angle command signal, the desired driving force signal, the desired braking force signal, and the desired linear thrust signal sent by the vehicle controller, and the actual wheel angle sensor signal, the actual torque sensor signal, the actual braking force sensor signal, and the actual linear thrust sensor signal sent by the wheel angle sensor, the torque sensor, the braking force sensor, and the linear thrust sensor respectively, performs inverse transformation to eliminate the existing coupling relationship, thereby obtaining four linear subsystems, and separately controls each linear subsystem through the PID control algorithm, and separately outputs current to drive the steering motor to rotate, drive the hub drive motor to rotate, control the braking module to brake, and control the linear motor to output linear thrust, so as to control the vehicle to achieve steering, driving, braking, and vibration reduction.

[0031] Further, the hub drive motor is an outer rotor direct drive hub motor.

[0032] Further, an installation hole is provided in the middle section of one of the two cross arms of the lower swing arm, and the installation hole is connected to the suspension support arm.

[0033] Further, the spring is an air spring, including but not limited to single-chamber and double-chamber air springs.

[0034] Further, the steering reduction device is a planetary gear reducer, a gear reducer or a worm reducer.

[0035] Further, the steering reduction device is in transmission connection with the steering motor and is arranged coaxially.

[0036] Further, the upper fixed kingpin is connected to the integrated floating steering knuckle through a ball joint, and the ball joint enables the integrated floating steering knuckle to rotate around the axis of the upper fixed kingpin while adapting to the spatial change of the up and down movement of the suspension module.

[0037] Wherein, the output shaft of the steering motor is parallel to the axis of the lower fixed kingpin. By arranging the fixed kingpin parallel to the output shaft of the steering motor, the lateral space of the vehicle is effectively saved, making the design more compact.

[0038] The present invention also provides a control method for an integrated kingpin steering system. Based on the above system, the steps are as follows:

[0039] 1) Establish a dynamic model of the integrated kingpin steering system;

[0040] 2) Conduct a reversibility analysis on the dynamic model of the integrated kingpin steering system;

[0041] 3) Use the neural network inverse method to decouple the integrated kingpin steering system into a linear system, obtaining four linear subsystems;

[0042] 4) Design a PID tracking controller to control the four decoupled linear subsystems, so as to control the vehicle to achieve steering, driving, braking, and vibration damping.

[0043] Furthermore, the dynamic model of the integrated kingpin steering system established in step 1) is as follows:

[0044]

[0045] Where J sa is the equivalent moment of inertia of the steering module, B sa is the equivalent damping coefficient of the steering module, θ sa is the wheel angle, T m = k Ts I sa is the torque of the steering motor, k Ts is the steering torque coefficient, I sa is the current of the steering motor, T P is the equivalent torque of the steering resistance torque on the steering module, d r is the equivalent road surface random disturbance torque on the steering module; J ma is the equivalent moment of inertia of the hub drive motor, B ma is the equivalent damping coefficient of the hub drive motor, θ ma is the angle of the hub drive motor, T m = k Tm I ma is the torque of the hub drive motor, k Tm is the driving torque coefficient, I ma is the current of the hub drive motor, T L is the load on the hub drive motor; J ea is the equivalent moment of inertia of the braking module, B ea is the equivalent damping coefficient of the braking module, θ ea is the angle of the braking motor, T e = k Te I ea is the torque of the braking motor, k Te is the braking torque coefficient, I ea is the current of the braking motor, T f is the frictional torque of the braking module, r is the transmission ratio of the braking module, F cl is the braking clamping force; m s is the sprung mass, m uis the unsprung mass, x s is the displacement of the sprung mass, x u is the displacement of the unsprung mass, x r is the road surface excitation displacement, P 0 is the absolute pressure inside the air spring of the air spring, P a is the external atmospheric pressure, A e is the equivalent acting area of the vertical force of the air spring, c is the air spring damping coefficient, g is the acceleration due to gravity, F e = k e I ka is the linear motor thrust, k e is the linear motor torque coefficient, I ka is the linear motor current.

[0046] Further, the step 2) specifically includes: performing reversibility analysis using the Interactor algorithm to ensure that the system can perform inverse transformation;

[0047] Calculate the derivatives of each order of the system output variable with respect to time respectively, and continuously take the derivative of the output function until all components of the output show the inclusion of the input. At this time, the system has a vector relative order, indicating that the system is reversible, and the state variables Control the input variable u = [T s , T m , T e , F e T , the system output variable

[0048] Use the Bristol - Shinskey method to determine the mapping relationship of the system before and after control to obtain the correct pairing relationship between the system input and output.

[0049] Further, the step 3) specifically includes:

[0050] 31) Determine the basic structure of the neural network inverse method;

[0051] The basic structure of the neural network inverse method includes: an input layer, an intermediate layer, and an output layer. The neurons in the input layer are used to receive external input information and transmit it to the neurons in the intermediate layer; the intermediate layer is used to perform information transformation according to the requirements of information change ability. The intermediate layer is designed as a single hidden layer or a multi - hidden layer structure. After further processing, it completes the forward propagation process of one - time learning, and the output layer outputs the processing results to the outside world;

[0052] 32) Conduct the selection of the neural network and the acquisition of data;

[0053] Determine the number of input nodes, output nodes, number of hidden layers, and excitation signal of the neural network, and obtain the input sample set for training the neural network​ and the expected output sample set [T s , T m , T e , F e ;

[0054] (33) Perform off-line training and performance verification of the neural network;

[0055] According to the input sample set and the expected output sample set obtained in step (32), use the BP neural network learning algorithm to select training samples and excitation signals, and perform off-line training on the neural network until the training error is small enough. By verifying the performance of the neural network inverse system, ensure that it can accurately approximate the inverse system of the original system, thereby obtaining four linear subsystems.

[0056] Furthermore, the expression of the PID tracking controller in step (4) is as follows:

[0057]

[0058] wherein, K P is the proportionality coefficient, K i is the integral coefficient, K d is the differential coefficient; u error (t) is the error value between the input quantity and the output quantity. The input quantity refers to the expected steering angle command signal, the expected driving force signal, the expected braking force signal, and the expected linear thrust signal; Y(t) is the output quantity, referring to the actual wheel steering angle sensor signal, the actual torque sensor signal, the actual braking force sensor signal, and the actual linear thrust sensor signal.

[0059] Advantages of the present invention:

[0060] (1) By arranging the fixed kingpin parallel to the output shaft of the steering motor, the present invention saves the lateral space of the vehicle and reduces the unsprung mass of the vehicle.

[0061] (2) In the present invention, the fixed kingpin no longer rotates with the wheel and does not bear the torque during steering. It only bears the vertical bending moment caused by the different forces on the upper fixed kingpin and the lower fixed kingpin and the lateral bending moment caused by the lateral force of the wheel, which simplifies the design of the system of the present invention and improves the bearing capacity of the fixed kingpin.

[0062] (3) The integrated design of the steering knuckle and the motor housing enhances the overall bearing capacity, making the system of the present invention more stable and reliable when bearing high loads.

[0063] (4) In the present invention, the braking module is built into the wheel module and connected to the main shaft of the hub motor. The main shaft of the hub motor serves as the cooling channel for the braking module and the hub drive motor, allowing the central cooling water path to pass through. This effectively reduces the heat generated during the operation of the braking module and the hub drive motor, ensuring the normal operation of the system of the present invention and greatly extending its service life.

[0064] (5) The present invention uses the neural network inverse method to decouple the system of the present invention into four linear subsystems: steering, braking, driving, and suspension, realizing the decoupling control of the system of the present invention, eliminating the control coupling between subsystems, and thus improving the control accuracy of the steering angle, driving force, braking force, linear thrust, etc. of each subsystem, and enhancing the control performance such as the smoothness of the system's dynamic response. Brief Description of the Drawings

[0065] Figure 1 is a schematic diagram of the structural principle of the system of the present invention.

[0066] Figure 2 is a top view of the structure of the present invention.

[0067] Figure 3 is a front view of the structure of the present invention.

[0068] Figure 4 is a left view of the structure of the present invention.

[0069] Figure 5 is a right view of the structure of the present invention.

[0070] Figure 6 is a schematic diagram of the movement mechanism principle of the steering module of the present invention.

[0071] Figure 7 is a schematic diagram of the structure of the braking module of the present invention.

[0072] Figure 8 is a flowchart of the control method of the present invention.

[0073] Figure 9 is a schematic diagram of the neural network structure of the inverse system of the present invention.

[0074] Figure 10 is a schematic diagram of the principle of the PID tracking controller of the present invention. Detailed Embodiments

[0075] For the convenience of those skilled in the art to understand, the present invention will be further described below in conjunction with embodiments and drawings. The content mentioned in the embodiments does not limit the present invention.

[0076] Refer to Figures 1 to 7As shown in the figure, an integrated kingpin steering system of the present invention includes: a wheel module 1, a suspension module 2, a steering module 3, a braking module 4, and an electronic control unit;

[0077] The wheel module includes: a wheel hub 11, a wheel hub motor main shaft 12, and a wheel hub drive motor 13;

[0078] The wheel hub 11 is provided inside the tire and includes a rim 111 and a spoke 112. The rim 111 is in contact with the tire. A wheel hub motor main shaft through-hole is provided at the center of the spoke 112, and a plurality of mounting holes for mounting the wheel hub drive motor 13 are provided around it;

[0079] One end of the wheel hub motor main shaft 12 is connected to the wheel hub drive motor 13, and the other end is connected to the brake disc. The wheel hub motor main shaft 12 serves as a cooling channel for the braking module and the wheel hub drive motor 13, allowing the central cooling water path to pass through;

[0080] The wheel hub drive motor 13 is disposed inside the wheel hub 11 and includes a motor housing 131, an inner stator 132, and an outer rotor 133. The inner stator 132 is disposed inside the motor housing 131. One end of the wheel hub motor main shaft 12 passes through the motor housing 131. The inside of the outer rotor 133 is connected to the wheel hub motor main shaft 12, and the outside of the outer rotor 133 is connected to the wheel hub 11;

[0081] The suspension module 2 includes: a swing arm 21 and a shock absorber assembly 22;

[0082] The swing arm 21 includes: an upper swing arm 211 and a lower swing arm 212. The intersecting ends of the two cross arms of the upper swing arm 211 are connected to the steering module, and the bifurcated ends of the two cross arms of the upper swing arm 211 are connected to the body / frame; The intersecting ends of the two cross arms of the lower swing arm 212 are connected to the steering module, and the bifurcated ends of the two cross arms of the lower swing arm 212 are connected to the body / frame;

[0083] The shock absorber assembly 22 includes: a spring, a linear motor, and a suspension support arm 221. The stator of the linear motor is connected to the spring. The mover of the linear motor is movably disposed inside the stator along the axis of the stator. The upper end of the mover is connected to the body / frame, and the lower end of the mover is connected to the suspension support arm 221; The spring is connected to the stator of the linear motor, and the spring and the linear motor are arranged on the same axis;

[0084] The steering module 3 includes: an integrated steering assembly 31 and a fixed kingpin 32;

[0085] The integrated steering assembly 31 includes: a steering motor 311, a steering reduction device, and an integrated floating steering knuckle 312;

[0086] The steering motor 311 is disposed inside the integrated floating steering knuckle 312;

[0087] The steering reduction gear includes: a sun gear, planet gears, a planet carrier, and an internal gear ring; the sun gear is fixed as a main pin gear on the lower fixed main pin in the fixed main pin 32, and the sun gear is connected to the planet gears and the planet carrier respectively. The planet gears are connected to the output shaft of the steering motor, and the planet gears rotate synchronously with the steering motor, causing the planet carrier to rotate around the sun gear;

[0088] The integrated floating knuckle 312 integrates the knuckle and the steering motor housing; the integrated floating knuckle integrates the knuckle and the steering motor housing in a unified design;

[0089] The steering motor 311 outputs torque to the steering reduction gear. After decelerating and increasing the torque through the steering reduction gear, it is output downward through the integrated floating knuckle 312, causing the integrated floating knuckle 312 to rotate around the fixed main pin 32. The middle part of the integrated floating knuckle 312 is connected to the vehicle wheel, thereby driving the vehicle wheel to steer;

[0090] The fixed main pin 32 includes: an upper fixed main pin 321 and a lower fixed main pin 322;

[0091] The upper fixed main pin 321 is connected to the upper end of the integrated floating knuckle 312, and the lower fixed main pin 322 is connected to the lower end of the integrated floating knuckle 312 through a ball joint; the integrated floating knuckle rotates around the axis of the lower fixed main pin, thereby driving the vehicle to steer;

[0092] The braking module 4 is placed in the wheel module 3, and it includes: a brake disc 41, a brake caliper 42, and brake pads 43;

[0093] The brake disc 41 is arranged on the wheel, and the brake disc 41 is connected to the main shaft 12 of the in-wheel motor, and the brake disc 41 rotates synchronously with the wheel;

[0094] The brake caliper 42 is arranged on the motor housing 131, the brake caliper 42 is located on both sides of the brake disc 41, and is arranged on the same side of the wheel module as the brake disc 41;

[0095] The brake pads 43 are installed inside the brake caliper 42;

[0096] The electronic control unit includes: four electronic control modules, and each electronic control module is simultaneously connected to the steering motor and the wheel angle sensor, the in-wheel drive motor and the torque sensor, the braking module and the braking force sensor, and the linear motor and the linear thrust sensor;

[0097] The electronic control module receives the expected steering angle command signal, the expected driving force signal, the expected braking force signal and the expected linear thrust signal sent by the vehicle controller, and the actual wheel angle sensor signal, the actual torque sensor signal, the actual braking force sensor signal and the actual linear thrust sensor signal respectively sent by the wheel angle sensor, the torque sensor, the braking force sensor and the linear thrust sensor, and performs inverse transformation to eliminate the existing coupling relationship, thereby obtaining four linear subsystems. Each linear subsystem is individually controlled through the PID control algorithm, and current is output to drive the steering motor to rotate, drive the wheel hub drive motor to rotate, control the braking module to brake, and control the linear motor to output linear thrust, so as to control the vehicle to achieve steering, driving, braking and vibration reduction.

[0098] Wherein, the hub drive motor is an outer rotor direct drive hub motor.

[0099] Among them, a mounting hole is provided in the middle section of one of the two cross arms of the lower swing arm, and the mounting hole is connected to the suspension support arm.

[0100] Wherein, the spring is an air spring, including but not limited to single-chamber and double-chamber air springs.

[0101] Wherein, the steering reduction device is a planetary gear reducer, a gear reducer or a worm reducer.

[0102] The steering reduction device is transmission-connected to the steering motor and arranged coaxially, and the output shaft of the steering motor is parallel to the output shaft of the steering reduction device.

[0103] The upper fixed kingpin is connected to the integrated floating steering knuckle via a ball pin, and the ball pin allows the integrated floating steering knuckle to rotate around the axis of the upper fixed kingpin while adapting to the spatial changes of the up and down jumping of the suspension module 2.

[0104] The output shaft of the steering motor is parallel to the axis of the lower fixed kingpin. By arranging the fixed kingpin parallel to the output shaft of the steering motor, the lateral space of the vehicle is effectively saved, making the design more compact.

[0105] Reference Figures 8 to 10 As shown, the present invention also provides a control method for an integrated kingpin steering system. Based on the above system, the steps are as follows:

[0106] 1) Establish the dynamic model of the integrated kingpin steering system;

[0107] The dynamic model of the integrated kingpin steering system is established as follows:

[0108]

[0109] In the formula, Jsa is the equivalent moment of inertia of the steering module, B sa is the equivalent damping coefficient of the steering module, θ sa is the wheel angle, T m = k Ts I sa is the torque of the steering motor, k Ts is the steering torque coefficient, I sa is the current of the steering motor, T P is the equivalent moment of the steering resistance torque on the steering module, d r is the road surface random interference torque equivalent to the steering module; J ma is the equivalent moment of inertia of the hub drive motor, B ma is the equivalent damping coefficient of the hub drive motor, θ ma is the angle of the hub drive motor, T m = k Tm I ma is the torque of the hub drive motor, k Tm is the driving torque coefficient, I ma is the current of the hub drive motor, T L is the load on the hub drive motor; J ea is the equivalent moment of inertia of the braking module, B ea is the equivalent damping coefficient of the braking module, θ ea is the angle of the braking motor, T e = k Te I ea is the torque of the braking motor, k Te is the braking torque coefficient, I ea is the current of the braking motor, T f is the frictional torque of the braking module, r is the transmission ratio of the braking module, F cl is the braking clamping force; m s is the unsprung mass, m u is the sprung mass, x s is the displacement of the sprung mass, x u is the displacement of the unsprung mass, x r is the road surface excitation displacement, P 0 is the absolute pressure inside the air spring, P a is the external atmospheric pressure, A e is the equivalent acting area of the air spring vertical force, c is the air spring damping coefficient, g is the acceleration due to gravity, F e = k e I ka is the thrust of the linear motor, k e is the torque coefficient of the linear motor, I ka is the current of the linear motor.

[0110] 2) Perform reversibility analysis on the integrated kingpin steering system dynamics model; specifically including: performing reversibility analysis using the Interactor algorithm to ensure that the system can perform inverse transformation;

[0111] Calculate the derivatives of each order of the system output variables with respect to time, and continuously take the derivative of the output function until all components of the output show the presence of the input. At this time, the system has a vector relative order, indicating that the system is reversible, and the state variables The control input variable u = [T s , T m , T e , F e T , the system output variables

[0112] Use the Bristol - Shinskey method to determine the mapping relationship of the system before and after control to obtain the correct pairing relationship between the system input and output.

[0113] 3) Use the neural network inverse method to decouple the integrated kingpin steering system into a linear system, obtaining four linear subsystems; specifically including:

[0114] 31) Determine the basic structure of the neural network inverse method;

[0115] The basic structure of the neural network inverse method includes: an input layer, an intermediate layer, and an output layer. The neurons in the input layer are used to receive external input information and transmit it to the neurons in the intermediate layer; the intermediate layer is used to perform information transformation according to the requirements of information change ability. The intermediate layer is designed as a single hidden layer or a multi - hidden layer structure. After further processing, the forward propagation process of one - time learning is completed, and the processing result is output to the outside by the output layer;

[0116] 32) Conduct the selection of the neural network and the acquisition of data;

[0117] Determine the number of input nodes, output nodes, number of hidden layers, and excitation signal of the neural network, and obtain the input sample set for training the neural network and the expected output sample set [T s , T m , T e , F e ;

[0118] 33) Conduct offline training and performance verification of the neural network;

[0119] ​According to the input sample set and the expected output sample set obtained in step 32), using the BP neural network learning algorithm, select training samples and excitation signals, and perform offline training on the neural network until the training error is small enough. By verifying the performance of the neural network inverse system, ensure that it can accurately approximate the inverse system of the original system, thereby obtaining four linear subsystems.

[0120] 4) Design a PID tracking controller to control the four decoupled linear subsystems to control the vehicle to achieve steering, driving, braking, and vibration reduction;

[0121] The expression of the PID tracking controller is as follows:

[0122]

[0123] In the formula, K P is the proportionality coefficient, K i is the integral coefficient, K d is the differential coefficient; u error (t) is the error value between the input quantity and the output quantity. The input quantity refers to the desired steering angle command signal, the desired driving force signal, the desired braking force signal, and the desired linear thrust signal; Y(t) is the output quantity, referring to the actual wheel steering angle sensor signal, the actual torque sensor signal, the actual braking force sensor signal, and the actual linear thrust sensor signal.

[0124] There are many specific application ways of the present invention. The above description is only the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements can still be made, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. An integrated kingpin steering system, characterized in that: include: Wheel modules, suspension modules, steering modules, brake modules and electronic control units; The wheel module comprises: a wheel hub, a wheel hub motor spindle and a wheel hub drive motor; The wheel hub is arranged inside the tire and comprises a rim and a spoke. The rim contacts the tire. A hub motor spindle through hole is arranged at the center of the spoke, and a plurality of mounting holes for mounting the hub drive motor are arranged around the spoke. One end of the hub motor spindle is connected to the hub drive motor, and the other end is connected to the brake disc. The hub motor spindle serves as a cooling channel for the brake module and the hub drive motor, allowing the central cooling water channel to pass through; The wheel hub drive motor is arranged in the wheel hub, and comprises a motor housing, an inner stator and an outer rotor. The inner stator is arranged inside the motor housing, one end of the wheel hub motor main shaft passes through the motor housing, the inner part of the outer rotor is connected to the wheel hub motor main shaft, and the outer part of the outer rotor is connected to the wheel hub; The suspension module comprises: a swing arm and a shock absorber assembly; The swing arm comprises an upper swing arm and a lower swing arm, wherein the intersection end of two cross arms of the upper swing arm is connected to the steering module, and the forked ends of two cross arms of the upper swing arm are connected to the vehicle body / frame; the intersection end of two cross arms of the lower swing arm is connected to the steering module, and the forked ends of two cross arms of the lower swing arm are connected to the vehicle body / frame; The shock absorber assembly includes: a spring, a linear motor and a suspension support arm, the stator of the linear motor is connected to the spring, the mover of the linear motor is movably arranged in the stator along the axis direction of the stator, the upper end of the mover is connected to the vehicle body / frame, and the lower end of the mover is connected to the suspension support arm; the spring is connected to the stator of the linear motor, and the arrangement axis of the spring and the linear motor coincide; The steering module comprises: an integrated steering assembly and a fixed kingpin; An integrated steering assembly, including: a steering motor, a steering reduction device and an integrated floating steering knuckle; The steering motor is arranged in the integrated floating steering knuckle; The steering reduction device comprises: a sun gear, a planetary gear, a planetary carrier and an inner gear ring; the sun gear is fixed on the lower section of the fixed kingpin in the fixed kingpin as a kingpin shaft gear, the sun gear is connected to the planetary gear and the planetary carrier respectively, the planetary gear is connected to the output shaft of the steering motor, the planetary gear rotates synchronously with the steering motor, so that the planetary carrier rotates around the sun gear; The integrated floating steering knuckle integrates the steering knuckle and the steering motor housing. The integrated floating steering knuckle integrates the steering knuckle and the steering motor housing into an integrated design; The steering motor outputs torque to the steering deceleration device, which decelerates and increases torque through the steering deceleration device and then outputs it to the lower end through the integrated floating steering knuckle, so that the integrated floating steering knuckle rotates around the fixed kingpin. The middle part of the integrated floating steering knuckle is connected to the wheels of the vehicle, thereby driving the wheels of the vehicle to steer; Fixed kingpin, including: upper fixed kingpin and lower fixed kingpin; The upper fixed kingpin is connected to the upper end of the integrated floating steering knuckle, and the lower fixed kingpin is connected to the lower end of the integrated floating steering knuckle through a ball stud; the integrated floating steering knuckle rotates around the axis of the lower fixed kingpin, thereby driving the vehicle to turn; The brake module is placed in the wheel module, and includes: a brake disc, a brake caliper and a brake pad; The brake disc is arranged on the wheel, the brake disc is connected to the main shaft of the wheel hub motor, and the brake disc rotates synchronously with the wheel; The brake caliper is arranged on the motor housing, the brake caliper is located on both sides of the brake disc, and is arranged on the same side of the wheel module as the brake disc; The brake pad is installed inside the brake caliper; The electronic control unit comprises: four electronic control modules, each of which is simultaneously connected to a steering motor and a wheel angle sensor, a wheel hub drive motor and a torque sensor, a brake module and a brake force sensor, and a linear motor and a linear thrust sensor; The electronic control module receives the expected steering angle command signal, the expected driving force signal, the expected braking force signal and the expected linear thrust signal sent by the vehicle controller, and the actual wheel angle sensor signal, the actual torque sensor signal, the actual braking force sensor signal and the actual linear thrust sensor signal respectively sent by the wheel angle sensor, the torque sensor, the braking force sensor and the linear thrust sensor, and performs inverse transformation to eliminate the existing coupling relationship, thereby obtaining four linear subsystems. Each linear subsystem is individually controlled through the PID control algorithm, and current is output to drive the steering motor to rotate, drive the wheel hub drive motor to rotate, control the braking module to brake, and control the linear motor to output linear thrust, so as to control the vehicle to achieve steering, driving, braking and vibration reduction.

2. The integrated kingpin steering system according to claim 1, characterized in that: A mounting hole is provided in the middle section of one of the two cross arms of the lower swing arm, and the mounting hole is connected to the suspension support arm.

3. The integrated kingpin steering system according to claim 1, characterized in that: The steering speed reduction device is transmission-connected with the steering motor and is coaxially arranged.

4. The integrated kingpin steering system according to claim 1, characterized in that: The output shaft of the steering motor is parallel to the axis of the lower fixed kingpin, and the fixed kingpin is arranged parallel to the output shaft of the steering motor.

5. The integrated kingpin steering system according to claim 1, characterized in that: The upper fixed kingpin is connected to the integrated floating steering knuckle through a ball pin, and the ball pin enables the integrated floating steering knuckle to rotate around the axis of the upper fixed kingpin while adapting to the spatial changes of the up and down jumping of the suspension module.

6. A control method for an integrated kingpin steering system, based on the system according to any one of claims 1 to 5, characterized in that: Here are the steps: 1) Establish the dynamic model of the integrated kingpin steering system; 2) Conduct reversibility analysis on the integrated kingpin steering system dynamics model; 3) The integrated kingpin steering system is decoupled into a linear system using the neural network inverse method, and four linear subsystems are obtained; 4) Design a PID tracking controller to control the four linear subsystems obtained by decoupling to control the vehicle to achieve steering, driving, braking and vibration reduction.

7. The control method of the integrated kingpin steering system according to claim 6, characterized in that: The dynamic model of the integrated kingpin steering system established in step 1) is as follows: In the formula, J sa is the equivalent moment of inertia of the steering module, B sa is the equivalent damping coefficient of the steering module, θ sa is the wheel angle, T m =k Ts I sa is the steering motor torque, k Ts is the steering torque coefficient, I sa is the steering motor current, T P is the equivalent torque of the steering resistance torque on the steering module, d r is the road random disturbance torque equivalent to the steering module; J ma is the equivalent moment of inertia of the wheel hub drive motor, B ma is the equivalent damping coefficient of the wheel hub drive motor, θ ma is the wheel hub drive motor rotation angle, T m =k Tm I ma is the wheel hub drive motor torque, k Tm is the driving torque coefficient, I ma is the wheel hub drive motor current, T L is the load on the wheel hub drive motor; J ea is the equivalent moment of inertia of the brake module, B ea is the equivalent damping coefficient of the brake module, θ ea is the braking motor rotation angle, T e =k Te I ea is the braking motor torque, k Te is the braking torque coefficient, I ea is the braking motor current, T f is the friction torque of the brake module, r is the transmission ratio of the brake module, F cl is the brake clamping force; m s is the sprung mass, m u is the unsprung mass, x s is the displacement of the sprung mass, x u is the displacement of the unsprung mass, x r is the road excitation displacement, P0 is the absolute pressure in the airbag, P a is the external atmospheric pressure, A e is the equivalent action area of ​​the vertical force of the air spring, c is the damping coefficient of the air spring, g is the acceleration of gravity, F e =k e I ka is the linear motor thrust, k e is the linear motor torque coefficient, I ka is the linear motor current.

8. The control method of the integrated kingpin steering system according to claim 6, characterized in that: The step 2) specifically includes: using the Interactor algorithm to perform reversibility analysis to ensure that the system performs an inverse transformation; Calculate the derivatives of the system output variables with respect to time, and continue to derive the output function until each component of the output shows that it contains the input. At this time, the system has a vector relative order, indicating that the system is reversible and the state variable Control input variable u=[T s ,T m ,T e ,F e ] T , system output variables The Bristol-Shinskey method is used to determine the mapping relationship between the systems before and after control in order to obtain the correct pairing relationship between the system input and output.

9. The control method of the integrated kingpin steering system according to claim 6, characterized in that: The step 3) specifically includes: 31) Determine the basic structure of the neural network inverse method; The basic structure of the neural network inverse method includes: an input layer, an intermediate layer and an output layer. The neurons in the input layer are used to receive input information from the outside world and transmit it to the neurons in the intermediate layer; the intermediate layer is used to transform information according to the requirements of information change capability. The intermediate layer is designed as a single hidden layer or a multi-hidden layer structure. After further processing, the forward propagation process of a learning is completed, and the processing result is output to the outside world by the output layer; 32) Select the neural network and obtain data; Determine the number of input nodes, output nodes, hidden layers and excitation signals of the neural network, and obtain the input sample set for training the neural network and the expected output sample set [T s ,T m ,T e ,F e ]; 33) Conduct offline training and performance verification of neural networks; According to the input sample set and the expected output sample set obtained in step 32), the BP neural network learning algorithm is used to select training samples and excitation signals, and the neural network is trained offline until the training error is small enough. The performance of the neural network inverse system is verified to ensure that it can accurately approximate the inverse system of the original system, thereby obtaining four linear subsystems.

10. The control method of the integrated kingpin steering system according to claim 6, characterized in that: The expression of the PID tracking controller in step 4) is as follows: In the formula, K P is the proportionality coefficient, K i is the integration coefficient, K d is the differential coefficient; u error (t) is the error value between the input and output quantities, the input quantity refers to the expected steering angle command signal, the expected driving force signal, the expected braking force signal and the expected linear thrust signal; Y(t) is the output quantity, which refers to the actual wheel angle sensor signal, the actual torque sensor signal, the actual braking force sensor signal and the actual linear thrust sensor signal.

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