A smooth trajectory planning and anti-skid coordinated control system for a four-axle global vehicle

Abstract

The present invention provides a smooth trajectory planning and anti-skid coordinated control system for a four-axis global vehicle, including a signal input preprocessing module, a reference trajectory planning module and a wheel torque control module; the signal input preprocessing module is used to collect and preprocess the control expectation instructions and vehicle state information to obtain an input signal; the reference trajectory planning module is used to plan an executable reference trajectory in real time according to the input signal and in combination with the physical constraints of the vehicle motion, and calculate the reference value of the tracking according to the executable reference trajectory, wherein the reference value at least includes a reference speed and a reference yaw rate; the wheel torque control module is used to track the reference trajectory, calculate the control torque of each wheel in real time in combination with the vehicle motion dynamics state, and send it to the corresponding wheel. The present invention can enable the global vehicle to travel stably and avoid the situation where the vehicle loses stability, rolls over, or is damaged by collision.

Description

Technical Field

[0001] The present invention relates to the field of automobile technology, and in particular to a smooth trajectory planning and anti-skid coordinated control system for a four-axle global vehicle. Background Art

[0002] Global vehicles are vehicles that can travel on any terrain, and four-axle global vehicles are global vehicles with four axles and eight wheels. With the continuous development of unmanned driving technology, unmanned driving technology has also been adopted on global vehicles.

[0003] Existing unmanned multi-axle global vehicles usually adopt a distributed four-axle drive form. The four wheels on the left are driven by one motor and the four wheels on the right are driven by another motor. In the absence of a planning and control system, the rotation of the left and right motors is directly controlled, which cannot meet the requirements of smooth driving of the vehicle, causing serious wear and tear of vehicle parts, thereby affecting the normal operation of the vehicle, reducing its service life, and even causing the vehicle to become unstable and overturned, or collide and be damaged. Summary of the invention

[0004] The object of the present invention is to provide a smooth trajectory planning and anti-skid coordinated control system for a four-axle global vehicle to meet the requirements for smooth driving of the four-axle global vehicle.

[0005] A smooth trajectory planning and anti-skid coordinated control system for a four-axle global vehicle, comprising a signal input preprocessing module, a reference trajectory planning module and a wheel torque control module;

[0006] The signal input preprocessing module is used to collect and preprocess the control expectation instruction and vehicle status information to obtain an input signal;

[0007] The reference trajectory planning module is used to plan an executable reference trajectory in real time according to the input signal and in combination with the physical constraints of the vehicle motion, and calculate the reference value of tracking according to the executable reference trajectory, wherein the reference value at least includes a reference rotation speed and a reference yaw angular velocity;

[0008] The wheel torque control module is used to track the reference trajectory, calculate the control torque of each wheel in real time in combination with the vehicle's motion dynamics state, and send it to the corresponding wheel;

[0009] Wherein, the wheel torque control module includes a longitudinal-yaw dynamics control unit and an anti-skid coordination control unit;

[0010] The longitudinal-lateral dynamics control unit is used to convert the reference rotation speed and the reference yaw angular velocity into a total torque of the wheels on the left and right sides of the vehicle through a closed-loop control strategy;

[0011] The anti-skid cooperative control unit is used to calculate the control torque of each wheel in real time according to the actual state of the wheel, combined with the drive anti-skid constraint and the total torque of the left and right wheels of the vehicle, and send it to the corresponding wheel.

[0012] According to the smooth trajectory planning and anti-skid coordinated control system of a four-axle global vehicle provided by the present invention, the signal input preprocessing module is responsible for collecting and preprocessing the control expectation instructions and vehicle status information, the reference trajectory planning module is responsible for planning an executable and smooth reference trajectory of the vehicle in real time based on the preprocessed signal in combination with the physical constraints of the vehicle motion, and calculating the tracking reference value based on the executable reference trajectory, and the wheel torque control module is responsible for calculating the control torque of the eight wheels in real time based on the tracking reference value in combination with the vehicle motion dynamics state, and sending it to the corresponding wheels to realize the control of the global vehicle, so that the global vehicle can travel stably and avoid the vehicle from becoming unstable, rolling over, or being damaged by collision. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A structural block diagram of the smooth trajectory planning and anti-skid coordinated control system for a four-axle global vehicle provided by the present invention;

[0014] Figure 2 This is a schematic diagram of the trajectory planning test verification effect;

[0015] Figure 3 It is a schematic diagram of the collaborative control test verification effect. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] See also Figure 1 An embodiment of the present invention provides a smooth trajectory planning and anti-skid coordinated control system for a four-axle global vehicle, including a signal input preprocessing module, a reference trajectory planning module and a wheel torque control module.

[0018] The four-axle global vehicle of the present invention includes eight independently driven electric wheels, and the system can control the torque of any one of the eight wheels, thereby adjusting the movement posture of the vehicle.

[0019] The signal input preprocessing module is used to collect and preprocess the control expectation instructions and vehicle status information to obtain an input signal.

[0020] The input signals include a desired curvature, a desired vehicle speed, an actual rotation speed of each wheel, and an actual yaw rate.

[0021] Considering the high-frequency noise in the working environment of global vehicles, in order to suppress the interference of noise, four consecutive cycles of signals are used for weighted filtering.

[0022] Specifically, the signal input preprocessing module satisfies the following conditional formula:

[0023] ;

[0024] ;

[0025] ;

[0026] ;

[0027] ;

[0028] ;

[0029] ;

[0030] ;

[0031] ;

[0032] ;

[0033] ;

[0034] in, For the k The expected curvature of the filtered output at time instant, For the k The actual measured value of the moment curvature, For the k -1 The expected curvature of the filtered output at time For the k -2 The expected curvature of the filtered output at time instant, For the k -3 The expected curvature of the filtered output at time instant, v r,k For the k The expected vehicle speed output by the filter at each moment, v c,k For the k The actual measured value of the vehicle speed at the moment, v r,k-1 For the k-1 The expected vehicle speed output by filtering at time 1, v r,k-2 For the k -2 The expected vehicle speed output by filtering at time , v r,k-3 For the k -3 The expected vehicle speed output by filtering at time , n 1f,k , n 2f,k , n 3f,k , n 4f,k , n 5f,k , n 6f,k , n 7f,k , n 8f,k Respectively k The actual rotation speeds of the first wheel, the second wheel, the third wheel, the fourth wheel, the fifth wheel, the sixth wheel, the seventh wheel, and the eighth wheel output by moment filtering, n 1c,k , n 2c,k , n 3c,k , n 4c,k , n 5c,k , n 6c,k , n 7c,k , n 8c,k Respectively k actual measured values ​​of the first wheel speed, the second wheel speed, the third wheel speed, the fourth wheel speed, the fifth wheel speed, the sixth wheel speed, the seventh wheel speed, and the eighth wheel speed at the moment, n 1f,k-1 , n 2f,k-1 , n 3f,k-1 , n 4f,k-1 , n 5f,k-1 , n 6f,k-1 , n 7f,k-1 , n 8f,k-1 Respectively k -1 The actual speeds of the first wheel, the second wheel, the third wheel, the fourth wheel, the fifth wheel, the sixth wheel, the seventh wheel, and the eighth wheel output by filtering at time n1f,k-2 , n 2f,k-2 , n 3f,k-2 , n 4f,k-2 , n 5f,k-2 , n 6f,k-2 , n 7f,k-2 , n 8f,k-2 Respectively k -2 The actual speeds of the first wheel, the second wheel, the third wheel, the fourth wheel, the fifth wheel, the sixth wheel, the seventh wheel, and the eighth wheel output by filtering at time instant; n 1f,k-3 , n 2f,k-3 , n 3f,k-3 , n 4f,k-3 , n 5f,k-3 , n 6f,k-3 , n 7f,k-3 , n 8f,k-3 Respectively k -3 The actual speeds of the first wheel, the second wheel, the third wheel, the fourth wheel, the fifth wheel, the sixth wheel, the seventh wheel, and the eighth wheel output by filtering at the moment, For the k The actual yaw rate output by the filter at the moment, For the k The actual measured value of the actual yaw rate at time, For the k The actual yaw rate output by the filter at time -1, For the k -2 The actual yaw rate output by filtering at time For the k -3 The actual yaw rate output by filtering at time , , , , , m v1 , m v2 , m v3 , m v4 , m n11 , m n12 ,m n13 , m n14 , m n21 , m n22 , m n23 , m n24 , m n31 , m n32 , m n33 , m n34 , m n41 , m n42 , m n43 , m n44 , m n51 , m n52 , m n53 , m n54 , m n61 , m n62 , m n63 , m n64 , m n71 , m n72 , m n73 , m n74 , m n81 , m n82 , m n83 , m n84 , , , , is the filter weight.

[0035] The reference trajectory planning module is used to plan an executable reference trajectory in real time according to the input signal and the physical constraints of the vehicle motion, and calculate the tracking reference values ​​according to the executable reference trajectory, the reference values ​​including the reference rotation speed, the reference curvature, the reference vehicle speed and the reference yaw rate.

[0036] Specifically, the reference trajectory planning module includes a desired curvature correction unit, a reference curvature solving unit, a reference vehicle speed solving unit and a reference yaw rate solving unit.

[0037] The desired curvature correction unit is used to correct the desired curvature to the instantaneous center of rotation of the vehicle to obtain a corrected desired curvature;

[0038] The reference curvature solving unit is used to plan a curvature trajectory according to the physical constraints of the vehicle, connect the current curvature of the vehicle with the corrected expected curvature into a smooth curve, and obtain a reference curvature;

[0039] The reference vehicle speed solving unit is used to plan a speed trajectory according to the physical constraints of the vehicle, connect the actual vehicle speed and the expected vehicle speed into a smooth curve, and obtain a reference vehicle speed and a reference rotation speed;

[0040] The reference yaw rate solving unit is used to calculate a reference yaw rate according to a reference curvature and a reference vehicle speed.

[0041] In this embodiment, the desired curvature correction unit satisfies the following formula:

[0042] ;

[0043] in, Indicates k Correct the desired curvature at all times, L represents the distance from the instantaneous center of rotation to the axle where the fourth wheel is located, B represents the distance between the fourth wheel and the eighth wheel, sgn is the sign function, when >0, =1; when <0: =-1; when =0, =0;

[0044] The reference curvature solving unit is specifically used for:

[0045] First calculate the theoretical value of the curvature increment , the expression is as follows:

[0046] ;

[0047] ;

[0048] in, The number of nodes representing the curvature trajectory, is the wheel control cycle, The sending frequency to correct the desired curvature;

[0049] Then calculate the current curvature of the vehicle , the expression is as follows:

[0050] ;

[0051] ;

[0052] v f,k For the k The actual speed of the vehicle at that moment, is the set value, which is an infinite decimal and can be taken as 0.001. The purpose is to prevent v f,k is 0; n lf,k For the k The filter output at the moment l The actual speed of the wheels, R l For the l The radius of the wheel;

[0053] Recalculate the reference curvature , the expression is as follows:

[0054] ;

[0055] in, is the curvature trajectory of the plan i The transition curvature of each point;

[0056] For curvature trajectory planning, the main responsibility is to plan the vehicle's executable and smooth reference curvature in real time, which can be divided into the following three cases:

[0057] when > hour, , is the maximum value of the curvature increment;

[0058] when < hour, , is the minimum value of the curvature increment;

[0059] when ≤ ≤ hour, ;

[0060] The reference vehicle speed solving unit is specifically used for:

[0061] First calculate the theoretical value of the speed increment , the expression is as follows:

[0062] ;

[0063] ;

[0064] in, N n The number of nodes representing the velocity trajectory, N nr Indicates the frequency of sending the desired vehicle speed;

[0065] Recalculate the reference speed v cc,k , the expression is as follows:

[0066] ;

[0067] in, v j The planned velocity trajectory j The transition speed of each point;

[0068] For the speed trajectory, it is mainly responsible for planning the vehicle's executable and smooth reference speed in real time, which is divided into the following three situations:

[0069] when Greater than v rmax hour, , v rmax is the maximum value of the velocity increment;

[0070] when Greater than v rmin hour, , v rmin is the minimum value of the speed increment;

[0071] when v rmin ≤ ≤ v rmax hour, ;

[0072] Finally, the reference speed is calculated using the following formula n cc,k :

[0073] ;

[0074] The reference yaw angular velocity solving unit is used to calculate the reference yaw angular velocity using the following formula :

[0075] .

[0076] The wheel torque control module is used to track the reference trajectory, calculate the control torque of each wheel in real time in combination with the vehicle's kinematic state, and send it to the corresponding wheel.

[0077] Wherein, the wheel torque control module includes a longitudinal-lateral dynamics control unit and an anti-skid coordination control unit.

[0078] The longitudinal-lateral dynamics control unit is used to convert the reference rotation speed and the reference yaw angular velocity into a total torque of the wheels on the left and right sides of the vehicle through a closed-loop control strategy;

[0079] The anti-skid cooperative control unit is used to calculate the control torque of each wheel in real time according to the actual state of the wheel, combined with the drive anti-skid constraint and the total torque of the left and right wheels of the vehicle, and send it to the corresponding wheel.

[0080] In this embodiment, the closed-loop control strategy in the longitudinal-lateral dynamics control unit adopts a mode of parallel feedforward control and feedback PID control;

[0081] Among them, feedforward control is used to overcome slope resistance, rolling resistance and air resistance, and calculate the feedforward torque T q , the calculation formula is:

[0082] ;

[0083] in, m is the vehicle mass, g is the acceleration due to gravity, is the slope, is the road rolling resistance coefficient, C D is the drag coefficient, A is the windward area, is the air density;

[0084] Feedback PID control uses a first PID controller and a second PID controller;

[0085] The first PID controller is used to eliminate the vehicle speed error and calculate the speed feedback torque T fv , the calculation formula is:

[0086] ;

[0087] ;

[0088] ;

[0089] in,K nP is the proportional coefficient of the first PID controller, e n is the vehicle speed error, K nI is the integral coefficient of the first PID controller, K nD is the differential coefficient of the first PID controller, for e n The first derivative of n f is the average value of the actual rotation speed of all wheels;

[0090] The second PID controller is used to eliminate the vehicle yaw rate error and calculate the yaw rate feedback torque , the calculation formula is:

[0091] ;

[0092] ;

[0093] in, is the proportional coefficient of the second PID controller, is the integral coefficient of the second PID controller, is the differential coefficient of the second PID controller, is the vehicle yaw rate error, for The first derivative of ;

[0094] The calculation formula for the total torque of the left and right wheels of the vehicle is:

[0095] ;

[0096] ;

[0097] in, T L is the total torque of the left wheel of the vehicle, T R is the total torque on the right wheel of the vehicle.

[0098] In this embodiment, the anti-skid cooperative control unit is specifically used to determine whether the wheel is slipping by checking whether the slip rate of each wheel exceeds the limit, and then distribute the driving torque to the wheel according to the wheel slip situation obtained by the judgment, wherein the first l Wheel slip rate The calculation formula is:

[0099] ;

[0100] when ≥ When l When the wheels slip; < When l The wheels do not slip.

[0101] If l The first wheel is judged to be slipping, which means that the ground is l The adhesion provided by the first wheel has exceeded the limit. l There is a high possibility that one wheel is suspended in the air or stuck in the mud. At this time, applying more driving torque will not only fail to help the vehicle get out of the skidding state, but it is more likely to cause the vehicle to spin and become unstable due to the extreme imbalance of torque on the left and right sides.

[0102] In order to restore the slipping wheel to a non-slip state as much as possible, the wheel executable driving torque is designed according to the following strategy:

[0103] When l The wheels are slipping and l ∈[1, 8], the condition is satisfied: T l,s = T l,k-1 - , T l,s For the l The available drive torque per wheel, T l,k-1 For the k -1 moment l The driving torque of each wheel, is the set torque reduction;

[0104] When l The wheels do not slip, and l ∈[1, 4], the condition is satisfied: T l,s = T L / 4;

[0105] When l The wheels do not slip, and l ∈[5, 8], the condition is satisfied: T l,s = T R / 4;

[0106] Furthermore, the calculation formula for the total torque of the wheels on the left and right sides of the vehicle is:

[0107] ;

[0108] ;

[0109] in, T L,s is the total driving torque that can be performed by the left wheels of the vehicle, T R,s is the total driving torque that can be performed by the right wheels of the vehicle, T 1,s , T 2,s , T 3,s , T 4,s , T 5,s , T 6,s , T 7,s , T 8,s The executable driving torques of the first wheel, the second wheel, the third wheel, the fourth wheel, the fifth wheel, the sixth wheel, the seventh wheel, and the eighth wheel respectively;

[0110] Then we get the following formula:

[0111] ;

[0112] ;

[0113] in, is the total driving torque difference of the left wheels of the vehicle, is the total driving torque difference of the right wheels of the vehicle;

[0114] when = When , the control torque of the 8 wheels is calculated according to the following formula:

[0115] T 1= T 1,s ; T 2= T 2,s ; T 3= T 3,s ; T 4= T 4,s ; T 5= T 5,s ; T 6= T 6,s ; T 7= T7,s ; T 8= T 8,s ;

[0116] in, T 1. T 2. T 3. T 4. T 5. T 6. T 7. T 8 are the control torques of the 1st wheel, the 2nd wheel, the 3rd wheel, the 4th wheel, the 5th wheel, the 6th wheel, the 7th wheel and the 8th wheel respectively;

[0117] when > When , the control torque of the 8 wheels is calculated according to the following formula:

[0118] T 1= T 1,s ; T 2= T 2,s ; T 3= T 3,s ; T 4= T 4,s ;

[0119] ;

[0120] ;

[0121] ;

[0122] ;

[0123] when < When , the control torque of the 8 wheels is calculated according to the following formula:

[0124] ;

[0125] ;

[0126] ;

[0127] ;

[0128] T 5= T 5,s ; T 6=T 6,s ; T 7= T 7,s ; T 8= T 8,s .

[0129] The system of the present invention is simulated and tested below. In the simulation test, the initial curvature is 0.1 / m, the expected curvature is 1 / m, the initial speed is 1m / s, the expected vehicle speed is -10m / s, the initial yaw rate is 0.1rad / s, the expected yaw rate is -0.6rad / s, the number of nodes of the curvature trajectory is 200, the minimum value of the curvature increment is -2 / m, the maximum value of the curvature increment is 2 / m, and the minimum value of the acceleration is -5m / s 2 , the maximum acceleration is 5m / s 2 , the minimum value of acceleration increment -1m / s 2 , the maximum value of acceleration increment is 1m / s 2 , the test results are as follows Figure 2 As shown, from Figure 2 It can be seen that the curvature curve increases linearly, and the speed, yaw rate, and wheel speed increase first and then decrease. The process is smooth and there is no sudden change. Under the constraints, the yaw rate reaches the expected value, while the speed is less than the expected value. The results show that the system of the present invention has the ability to generate smooth parameter trajectories. Furthermore, the collaborative control effect is as follows Figure 3 As shown, from Figure 3 It can be seen that except for slight fluctuations in the collaborative control tracking caused by interference such as sensor measurement noise, the overall vehicle driving in the entire domain is relatively stable, and there is no vehicle instability or rollover.

[0130] In summary, according to the smooth trajectory planning and anti-skid coordinated control system of the four-axle global vehicle provided by the present invention, the signal input preprocessing module is responsible for collecting and preprocessing the control expectation instructions and vehicle status information, the reference trajectory planning module is responsible for planning the vehicle's executable and smooth reference trajectory in real time based on the preprocessed signal in combination with the physical constraints of the vehicle's motion, and calculating the tracking reference value based on the executable reference trajectory, the wheel torque control module is responsible for calculating the control torque of the eight wheels in real time based on the tracking reference value in combination with the vehicle's motion dynamics state, and sending it to the corresponding wheels to achieve control of the global vehicle, so that the global vehicle can travel stably and avoid vehicle instability, rollover, collision and damage.

[0131] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0132] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A smooth trajectory planning and anti-skid coordinated control system for a four-axle global vehicle, characterized in that: It includes a signal input preprocessing module, a reference trajectory planning module and a wheel torque control module; The signal input preprocessing module is used to collect and preprocess the control expectation instruction and vehicle status information to obtain an input signal; The reference trajectory planning module is used to plan an executable reference trajectory in real time according to the input signal and in combination with the physical constraints of the vehicle motion, and calculate the reference value of tracking according to the executable reference trajectory, wherein the reference value at least includes a reference rotation speed and a reference yaw angular velocity; The wheel torque control module is used to track the reference trajectory, calculate the control torque of each wheel in real time in combination with the vehicle's motion dynamics state, and send it to the corresponding wheel; Wherein, the wheel torque control module includes a longitudinal-yaw dynamics control unit and an anti-skid coordination control unit; The longitudinal-lateral dynamics control unit is used to convert the reference rotation speed and the reference yaw angular velocity into a total torque of the wheels on the left and right sides of the vehicle through a closed-loop control strategy; The anti-skid cooperative control unit is used to calculate the control torque of each wheel in real time according to the actual state of the wheel, combined with the drive anti-skid constraint and the total torque of the left and right wheels of the vehicle, and send it to the corresponding wheel.

2. The smooth trajectory planning and anti-skid coordinated control system for a four-axle global vehicle according to claim 1 is characterized in that: The input signals include a desired curvature, a desired vehicle speed, an actual rotation speed of each wheel, and an actual yaw rate; The signal input preprocessing module satisfies the following conditional formula: ； ； ； ； ； ； ； ； ； ； ； in, For the k The expected curvature of the filtered output at time instant, For the k The actual measured value of the moment curvature, For the k -1 The expected curvature of the filtered output at time For the k -2 The expected curvature of the filtered output at time instant, For the k -3 The expected curvature of the filtered output at time instant, v r,k For the k The expected vehicle speed output by the filter at each moment, v c,k For the k The actual measured value of the vehicle speed at the moment, v r,k-1 For the k -1 The expected vehicle speed output by filtering at time 1, v r,k-2 For the k -2 The expected vehicle speed output by filtering at time , v r,k-3 For the k -3 The expected vehicle speed output by filtering at time , n 1f,k , n 2f,k , n 3f,k , n 4f,k , n 5f,k , n 6f,k , n 7f,k , n 8f,k Respectively k The actual rotation speeds of the first wheel, the second wheel, the third wheel, the fourth wheel, the fifth wheel, the sixth wheel, the seventh wheel, and the eighth wheel output by moment filtering, n 1c,k , n 2c,k , n 3c,k , n 4c,k , n 5c,k , n 6c,k , n 7c,k , n 8c,k Respectively k actual measured values ​​of the first wheel speed, the second wheel speed, the third wheel speed, the fourth wheel speed, the fifth wheel speed, the sixth wheel speed, the seventh wheel speed, and the eighth wheel speed at the moment, n 1f,k-1 , n 2f,k-1 , n 3f,k-1 , n 4f,k-1 , n 5f,k-1 , n 6f,k-1 , n 7f,k-1 , n 8f,k-1 Respectively k -1 The actual speeds of the first wheel, the second wheel, the third wheel, the fourth wheel, the fifth wheel, the sixth wheel, the seventh wheel, and the eighth wheel output by filtering at time n 1f,k-2 , n 2f,k-2 , n 3f,k-2 , n 4f,k-2 , n 5f,k-2 , n 6f,k-2 , n 7f,k-2 , n 8f,k-2 Respectively k -2 The actual speeds of the first wheel, the second wheel, the third wheel, the fourth wheel, the fifth wheel, the sixth wheel, the seventh wheel, and the eighth wheel output by filtering at time instant; n 1f,k-3 , n 2f,k-3 , n 3f,k-3 , n 4f,k-3 , n 5f,k-3 , n 6f,k-3 , n 7f,k-3 , n 8f,k-3 Respectively k -3 The actual speeds of the first wheel, the second wheel, the third wheel, the fourth wheel, the fifth wheel, the sixth wheel, the seventh wheel, and the eighth wheel output by filtering at the moment, For the k The actual yaw rate output by the filter at the moment, For the k The actual measured value of the actual yaw rate at time, For the k The actual yaw rate output by the filter at time -1, For the k -2 The actual yaw rate output by filtering at time For the k -3 The actual yaw rate output by filtering at time , , , , , m v1 , m v2 , m v3 , m v4 , m n11 , m n12 , m n13 , m n14 , m n21 , m n22 , m n23 , m n24 , m n31 , m n32 , m n33 , m n34 , m n41 , m n42 , m n43 , m n44 , m n51 , m n52 , m n53 , m n54 , m n61 , m n62 , m n63 , m n64 , m n71 , m n72 , m n73 , m n74 , m n81 , m n82 , m n83 , m n84 , , , , is the filter weight.

3. The smooth trajectory planning and anti-skid coordinated control system for a four-axle global vehicle according to claim 2 is characterized in that: The reference trajectory planning module includes a desired curvature correction unit, a reference curvature solving unit, a reference vehicle speed solving unit and a reference yaw rate solving unit; The desired curvature correction unit is used to correct the desired curvature to the instantaneous center of rotation of the vehicle to obtain a corrected desired curvature; The reference curvature solving unit is used to plan a curvature trajectory according to the physical constraints of the vehicle, connect the current curvature of the vehicle with the corrected expected curvature into a smooth curve, and obtain a reference curvature; The reference vehicle speed solving unit is used to plan a speed trajectory according to the physical constraints of the vehicle, connect the actual vehicle speed and the expected vehicle speed into a smooth curve, and obtain a reference vehicle speed and a reference rotation speed; The reference yaw rate solving unit is used to calculate a reference yaw rate according to a reference curvature and a reference vehicle speed.

4. The smooth trajectory planning and anti-skid coordinated control system for a four-axle global vehicle according to claim 3 is characterized in that: The desired curvature correction unit satisfies the following formula: ； in, Indicates k Correct the desired curvature at all times, L represents the distance from the instantaneous center of rotation to the axle where the fourth wheel is located, B represents the distance between the fourth wheel and the eighth wheel, sgn is the sign function, when >0, =1; when <0: =-1; when =0, =0; The reference curvature solving unit is specifically used for: First calculate the theoretical value of the curvature increment , the expression is as follows: ； ； in, The number of nodes representing the curvature trajectory, is the wheel control cycle, The sending frequency to correct the desired curvature; Then calculate the current curvature of the vehicle , the expression is as follows: ； ； v f,k For the k The actual speed of the vehicle at that moment, is the set value, n lf,k For the k The filter output at the moment l The actual speed of the wheels, R l For the l The radius of the wheel; Recalculate the reference curvature , the expression is as follows: ； in, is the curvature trajectory of the plan i The transition curvature of each point; when > hour, , is the maximum value of the curvature increment; when < hour, , is the minimum value of the curvature increment; when ≤ ≤ hour, ; The reference vehicle speed solving unit is specifically used for: First calculate the theoretical value of the speed increment , the expression is as follows: ； ； in, N n The number of nodes representing the velocity trajectory, N nr Indicates the frequency of sending the desired vehicle speed; Recalculate the reference speed v cc,k , the expression is as follows: ； in, v j The planned velocity trajectory j The transition speed of each point; when Greater than v rmax hour, , v rmax is the maximum value of the velocity increment; when Greater than v rmin hour, , v rmin is the minimum value of the speed increment; when v rmin ≤ ≤ v rmax hour, ; Finally, the reference speed is calculated using the following formula n cc,k : ； The reference yaw angular velocity solving unit is used to calculate the reference yaw angular velocity using the following formula : 。 5. The smooth trajectory planning and anti-skid coordinated control system for a four-axle global vehicle according to claim 4 is characterized in that: The closed-loop control strategy in the longitudinal-lateral dynamics control unit adopts a mode of parallel feedforward control and feedback PID control; Among them, feedforward control is used to overcome slope resistance, rolling resistance and air resistance, and calculate the feedforward torque T q , the calculation formula is: ； in, m is the vehicle mass, g is the acceleration due to gravity, is the slope, is the road rolling resistance coefficient, C D is the drag coefficient, A is the windward area, is the air density; Feedback PID control uses a first PID controller and a second PID controller; The first PID controller is used to eliminate the vehicle speed error and calculate the speed feedback torque T fv , the calculation formula is: ； ； ； in, K nP is the proportional coefficient of the first PID controller, e n is the vehicle speed error, K nI is the integral coefficient of the first PID controller, K nD is the differential coefficient of the first PID controller, for e n The first derivative of n f is the average value of the actual rotation speed of all wheels; The second PID controller is used to eliminate the vehicle yaw rate error and calculate the yaw rate feedback torque , the calculation formula is: ； ； in, is the proportional coefficient of the second PID controller, is the integral coefficient of the second PID controller, is the differential coefficient of the second PID controller, is the vehicle yaw rate error, for The first derivative of ; The calculation formula for the total torque of the left and right wheels of the vehicle is: ； ； in, T L is the total torque of the left wheel of the vehicle, T R is the total torque on the right wheel of the vehicle.

6. The smooth trajectory planning and anti-skid coordinated control system for a four-axle global vehicle according to claim 5, characterized in that: The anti-skid cooperative control unit is specifically used to determine whether the wheel is slipping by checking whether the slip rate of each wheel exceeds the limit, and then distribute the driving torque to the wheel according to the wheel slip situation determined, wherein the first l Wheel slip rate The calculation formula is: ； when ≥ When l When the wheels slip; < When l The wheels do not slip; When l The wheels are slipping and l ∈[1, 8], the condition is satisfied: T l,s = T l,k-1 - , T l,s For the l The available drive torque per wheel, T l,k-1 For the k -1 moment l The driving torque of each wheel, is the set torque reduction; When l The wheels do not slip, and l ∈[1, 4], the condition is satisfied: T l,s = T L / 4; When l The wheels do not slip, and l ∈[5, 8], the condition is satisfied: T l,s = T R / 4; Furthermore, the calculation formula for the total torque of the wheels on the left and right sides of the vehicle is: ； ； in, T L,s is the total driving torque that can be performed by the left wheels of the vehicle, T R,s is the total driving torque that can be performed by the right wheels of the vehicle, T 1,s , T 2,s , T 3,s , T 4,s , T 5,s , T 6,s , T 7,s , T 8,s The executable driving torques of the first wheel, the second wheel, the third wheel, the fourth wheel, the fifth wheel, the sixth wheel, the seventh wheel, and the eighth wheel respectively; Then we get the following formula: ； ； in, is the total driving torque difference of the left wheels of the vehicle, is the total driving torque difference of the right wheels of the vehicle; when = When , the control torque of the 8 wheels is calculated according to the following formula: T 1= T 1,s ； T 2= T 2,s ； T 3= T 3,s ； T 4= T 4,s ； T 5= T 5,s ； T 6= T 6,s ； T 7= T 7,s ； T 8= T 8,s ； in, T 1. T 2. T 3. T 4. T 5. T 6. T 7. T 8 are the control torques of the 1st wheel, the 2nd wheel, the 3rd wheel, the 4th wheel, the 5th wheel, the 6th wheel, the 7th wheel and the 8th wheel respectively; when > When , the control torque of the 8 wheels is calculated according to the following formula: T 1= T 1,s ； T 2= T 2,s ； T 3= T 3,s ； T 4= T 4,s ； ； ； ； ； when < When , the control torque of the 8 wheels is calculated according to the following formula: ； ； ； ； T 5= T 5,s ； T 6= T 6,s ； T 7= T 7,s ； T 8= T 8,s 。

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