CN113085578A - Four-wheel-drive automobile yaw control method and device based on fuzzy PID - Google Patents
Four-wheel-drive automobile yaw control method and device based on fuzzy PID Download PDFInfo
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Abstract
The invention provides a four-wheel drive automobile yaw control method and device based on fuzzy PID, and belongs to the technical field of automobiles. It has solved the problem that there is the vehicle poor stability in current moment of torsion distribution technique. The four-wheel-drive automobile yaw control method based on the fuzzy PID comprises the following steps: performing table lookup according to the current operating parameters of the vehicle to obtain an open-loop torque distribution coefficient; obtaining an expected yaw angular speed according to the rotation angle of the steering wheel and the longitudinal speed; calculating the difference between the expected yaw velocity and the actual yaw velocity to obtain a yaw velocity difference, obtaining the difference change rate of the yaw velocity difference at the front moment and the rear moment, and performing fuzzy PID control on the yaw velocity difference and the difference change rate to obtain a closed-loop torque distribution coefficient; and distributing the front axle torque and the rear axle torque according to the open-loop torque distribution coefficient and the closed-loop torque distribution coefficient. A four-wheel drive vehicle yaw control device based on fuzzy PID is also provided. The invention can improve the stability of the vehicle.
Description
Technical Field
The invention belongs to the technical field of automobiles, and relates to a four-wheel-drive automobile yaw control method and device based on fuzzy PID.
Background
The electric four-wheel drive automobile is usually provided with an independent front axle electric drive system and a rear axle electric drive system, the front and rear electric drive systems can distribute the torque required by a driver in a (0-1) proportion range, so that independent front drive, independent rear drive or four-wheel drive can be easily realized, and the torque distribution of the front and rear drive systems of the electric four-wheel drive automobile is greatly flexible.
The current four-wheel-drive torque distribution method mainly depends on basic state parameters such as steering wheel rotation angle, reference vehicle speed, requested torque, accelerator opening degree, road surface adhesion coefficient, road gradient, longitudinal acceleration, lateral acceleration and the like to carry out forward table look-up, for example, the driving system of the electric four-wheel-drive automobile and the torque distribution method thereof disclosed by Chinese patent documents calculate the optimal torque distribution coefficient according to the current vehicle speed and the torque look-up table required by a driver, so that the optimal target required torque is obtained to reasonably distribute the torque of the front and rear driving systems; the scheme calculates the torque distribution proportion of the front driving system and the rear driving system in real time, and compared with a distribution method adopting a fixed proportion in the prior art, the scheme can better adapt to different driving conditions, but the scheme does not consider the real-time attitude change of a vehicle, so that the control effect seriously depends on the accuracy of a standard quantity, the fault tolerance of control is lower, the rationality of vehicle torque distribution cannot be ensured, and the safety and the stability of the vehicle are poorer.
Disclosure of Invention
The invention aims to provide a four-wheel-drive automobile yaw control method and a four-wheel-drive automobile yaw control device based on fuzzy PID (proportion integration differentiation), aiming at solving the technical problems that: how to realize the reasonable distribution of the torque of the front axle and the rear axle, thereby improving the stability of the vehicle.
The purpose of the invention can be realized by the following technical scheme: a four-wheel drive vehicle yaw control method based on fuzzy PID comprises the following steps:
performing table lookup according to the current operating parameters of the vehicle to obtain an open-loop torque distribution coefficient;
obtaining an expected yaw angular speed according to the rotation angle of the steering wheel and the longitudinal speed;
calculating the difference between the expected yaw rate and the actual yaw rate to obtain a yaw rate difference, and obtaining a difference change rate according to the yaw rate difference obtained at the previous moment and the later moment;
carrying out fuzzy PID control on the difference value of the yaw angular velocity and the change rate of the difference value to obtain a closed-loop torque distribution coefficient;
and distributing the front axle torque and the rear axle torque according to the open-loop torque distribution coefficient and the closed-loop torque distribution coefficient to obtain the front axle requested torque and the rear axle requested torque.
The four-wheel drive yaw control method based on the fuzzy PID has the advantages that according to the current running parameters of the vehicle, besides the open-loop torque distribution coefficient is obtained by table lookup, the actual yaw rate of the vehicle is also detected, the expected yaw rate is obtained according to the rotation angle of the steering wheel and the longitudinal vehicle speed, the closed-loop torque split coefficient is obtained by performing a fuzzy PID control operation on the difference between the actual yaw rate and the desired yaw rate, and then the open-loop torque distribution coefficient and the closed-loop torque distribution coefficient are added to obtain the final torque distribution coefficient, the invention considers the actual yaw condition of the vehicle when distributing the torque of the front and rear axes, the torque distribution coefficient of the front and rear axles is dynamically adjusted according to the attitude of the vehicle, so that the torque distribution coefficient is more reasonable, and then under the condition of guaranteeing the maximum power of the vehicle, the stability and the safety of the vehicle are improved.
In the four-wheel-drive vehicle yaw control method based on the fuzzy PID, the method further comprises the following steps:
the maximum desired yaw rate is calculated from the road surface adhesion coefficient, and the desired yaw rate obtained as described above is limited to the maximum desired yaw rate. The maximum value of the expected yaw rate is limited according to the road adhesion coefficient, so that the torque distribution is more reasonable, and the running stability of the vehicle is improved.
In the four-wheel-drive vehicle yaw control method based on the fuzzy PID, the maximum desired yaw rate is obtained by the following formula one:
wherein,
the maximum lateral acceleration is obtained by the following formula two:
wherein rt is a correction factor, and is generally 0.7; mu is the road surface adhesion coefficient; g is the acceleration of gravity; vxThe real-time speed of the vehicle.
In the four-wheel-drive vehicle yaw control method based on the fuzzy PID, the method further comprises the following steps:
the rate of change of the desired yaw rate obtained as described above is adjusted according to the steering wheel speed.
In the four-wheel-drive vehicle yaw control method based on the fuzzy PID, the operation of adjusting the transformation rate of the obtained desired yaw rate according to the rotating speed of the steering wheel is as follows:
when the steering wheel speed is greater than the preset speed value, the rate of change of the control desired yaw rate is decreased as the steering wheel speed increases.
The conversion rate of the expected yaw rate is dynamically adjusted according to the rotating speed of the steering wheel, so that the conversion rate of the expected yaw rate is shortened when the rotating speed of the steering wheel is high, the timely adjustment of the torque distribution of the front shaft and the rear shaft is ensured, and the running stability and safety of the vehicle are improved.
In the four-wheel-drive vehicle yaw control method based on fuzzy PID, the current operation parameters of the vehicle comprise vehicle speed, road adhesion coefficient, longitudinal acceleration, lateral acceleration and road gradient transmitted on a CAN bus.
A four-wheel-drive vehicle yaw control device based on fuzzy PID comprises a signal acquisition module for acquiring current operating parameters of a vehicle, and further comprises:
the open-loop control module is used for looking up the current operating parameters of the vehicle to obtain an open-loop torque distribution coefficient;
the expected yaw rate acquisition module is used for acquiring an expected yaw rate according to the steering wheel rotation angle signal and the longitudinal vehicle speed signal acquired by the signal acquisition module;
a yaw rate detection module for detecting an actual yaw rate of the vehicle;
the fuzzy PID control module is used for obtaining a yaw velocity difference according to the expected yaw velocity and the actual yaw velocity, and further obtaining a difference change rate according to the yaw velocity difference at the front moment and the rear moment; the system is also used for carrying out fuzzy PID control on the difference value of the yaw angular velocity and the change rate of the difference value so as to obtain a closed-loop torque distribution coefficient;
and the torque distribution control module is used for distributing the front axle torque and the rear axle torque according to the open-loop torque distribution coefficient and the closed-loop torque distribution coefficient to obtain the front axle requested torque and the rear axle requested torque.
After the vehicle is started, the signal acquisition module acquires the current operation parameters of the vehicle in real time, the open-loop control module obtains an open-loop torque distribution coefficient according to the current operation parameters of the vehicle acquired by the signal acquisition module by looking up a table, meanwhile, the yaw rate detection module detects the actual yaw rate of the vehicle in real time, the expected yaw rate acquisition module acquires an expected yaw rate according to the steering wheel rotation angle and the longitudinal vehicle speed, the fuzzy PID control module performs fuzzy PID control operation on the difference value between the actual yaw rate and the expected yaw rate to obtain a closed-loop torque distribution coefficient, and the torque distribution control module performs addition calculation on the open-loop torque distribution coefficient and the closed-loop torque distribution coefficient to obtain a final torque distribution coefficient. The torque distribution coefficients of the front axle and the rear axle are dynamically adjusted according to the posture of the vehicle, so that the torque distribution coefficients are more reasonable, and the stability and the safety of the vehicle are improved under the condition of ensuring the maximum power of the vehicle.
In the four-wheel-drive yaw control device based on the fuzzy PID, the four-wheel-drive yaw control device further comprises:
the conversion rate adjusting module is used for adjusting the time obtained by the expected yaw rate according to the rotating speed of the steering wheel obtained by the signal acquisition module and transmitting the time to the expected yaw rate obtaining module;
and the expected yaw rate acquisition module is used for controlling the interval time of the expected yaw rate transmitted to the fuzzy PID control module according to the adjustment result transmitted by the conversion rate adjustment module.
In the four-wheel-drive yaw control device based on the fuzzy PID, the four-wheel-drive yaw control device further comprises:
the expected yaw rate limiting module is used for calculating according to the road adhesion coefficient acquired by the signal acquisition module to acquire a maximum expected yaw rate and transmitting the maximum expected yaw rate to the expected yaw rate acquisition module;
the desired yaw-rate acquisition module is operable to limit the desired yaw-rate to within a maximum desired yaw-rate.
When the expected yaw rate obtaining module obtains the expected yaw rate, the expected yaw rate limiting module calculates the maximum expected yaw rate according to the road adhesion coefficient, so that the expected yaw rate is limited in the maximum expected yaw rate, the torque distribution is more reasonable, and the running stability of the vehicle is ensured.
In the four-wheel-drive yaw control device based on the fuzzy PID, the fuzzy PID control module comprises:
the difference value calculation module is used for calculating the difference value between the expected yaw rate transmitted by the expected yaw rate acquisition module and the actual yaw rate transmitted by the yaw rate detection module to obtain a yaw rate difference value;
the change rate calculation module is used for calculating the difference of the yaw velocity difference calculated by the difference calculation module at the front moment and the rear moment to obtain the difference change rate;
the fuzzy controller is used for fuzzifying the difference value of the yaw velocity calculated by the difference value calculation module and the difference change rate calculated by the change rate calculation module and finding out output quantity according to a fuzzy rule table to optimize in real time to obtain three parameters of Kp, Ki and Kd;
and the PID controller is used for carrying out PID operation according to the Kp, Ki and Kd parameters obtained by the fuzzy controller and the yaw velocity difference calculated by the difference calculation module to obtain a closed-loop torque distribution coefficient.
Compared with the prior art, the four-wheel-drive automobile yaw control method and the four-wheel-drive automobile yaw control device based on the fuzzy PID have the following advantages:
1. according to the invention, the open-loop torque distribution coefficient is obtained by looking up the table of the current running parameters of the vehicle, the forward control of the vehicle torque distribution is realized, the closed-loop control is carried out according to the difference value between the actual yaw velocity and the expected yaw velocity of the vehicle by using the fuzzy PID algorithm, and when the vehicle is unstable, the open-loop torque distribution coefficient can be quickly adjusted by combining the fuzzy PID control, so that more accurate torque distribution coefficient is obtained, the front and rear axle torque distribution of the vehicle is more reasonable, the function of quickly adjusting the body posture of the vehicle is achieved, and the stability and the safety of the vehicle are improved.
2. The invention also adjusts the value of the expected yaw rate and the conversion rate, further ensures the reasonability of torque distribution, and improves the stability and the safety of the vehicle.
Drawings
Fig. 1 is a control flow chart according to a first embodiment of the present invention.
Fig. 2 is a control flow chart of the second embodiment of the present invention.
Fig. 3 is a control flow chart of a third embodiment of the present invention.
Fig. 4 is a control flowchart of a fourth embodiment of the present invention.
Fig. 5 is a schematic structural diagram of a first embodiment of the present invention.
Fig. 6 is a schematic structural diagram of a second embodiment of the present invention.
Fig. 7 is a schematic structural diagram of a third embodiment of the present invention.
Fig. 8 is a schematic structural diagram of a fourth embodiment of the present invention.
In the figure, 1, a signal acquisition module; 2. an open loop control module; 3. an expected yaw rate acquisition module; 4. a yaw rate detection module; 5. a fuzzy PID control module; 51. a difference value calculation module; 52. a rate of change calculation module; 53. a fuzzy controller; 54. a PID controller; 6. a torque distribution control module; 7. a conversion rate adjustment module; 8. a yaw-rate limiting module is desired.
Detailed Description
The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.
The first embodiment is as follows:
as shown in FIG. 5, the four-wheel-drive vehicle yaw control device based on fuzzy PID comprises a signal acquisition module 1, an open-loop control module 2, an expected yaw rate acquisition module 3, a yaw rate detection module 4, a fuzzy PID control module 5 and a torque distribution control module 6, wherein the signal acquisition module 1 is connected with the open-loop control module 2, the expected yaw rate acquisition module 3 is connected with the signal acquisition module 1 and is used for calculating to acquire an expected yaw rate according to a steering wheel angle signal and a longitudinal vehicle speed signal acquired by the signal acquisition module 1, the yaw rate detection module 4 and the expected yaw rate acquisition module 3 are both connected with the fuzzy PID control module 5, the fuzzy PID control module 5 comprises a difference value calculation module 51, a change rate calculation module 52, a fuzzy controller 53 and a PID controller 54, the difference value calculation module 51 is respectively connected with the change rate calculation module 52, The fuzzy controller 53 is connected with the PID controller 54, the change rate calculation module 52 is connected with the fuzzy controller 53, the fuzzy controller 53 is connected with the PID controller 54, the yaw rate detection module 4 and the desired yaw rate acquisition module 3 are both connected with the difference value calculation module 51 in the fuzzy PID control module 5, and the torque distribution control module 6 is connected with the PID controller 54 in the fuzzy PID control module 5.
The four-wheel-drive automobile yaw control device based on the fuzzy PID is a four-wheel-drive automobile yaw control method based on the fuzzy PID, which is realized by arranging various functional components to respectively correspond. The operation principle of the four-wheel-drive yaw control device based on the fuzzy PID is explained by the four-wheel-drive yaw control method based on the fuzzy PID.
As shown in fig. 1, the four-wheel-drive yaw control method based on the fuzzy PID is a control method of a four-wheel-drive yaw control device based on the fuzzy PID, before the four-wheel-drive yaw control method based on the fuzzy PID is applied to vehicle torque distribution, current running parameters of a vehicle including a vehicle speed, a road adhesion coefficient, a longitudinal acceleration, a lateral acceleration, a road gradient, a steering wheel angle, a requested torque, an accelerator opening degree and the like are tested, and a two-dimensional table of torque distribution coefficients corresponding to each parameter is acquired and stored in the system in advance.
When the vehicle is ignited and started, the current running parameters of the vehicle, including vehicle speed, road adhesion coefficient, longitudinal acceleration, lateral acceleration, road gradient, steering wheel rotating speed, steering wheel rotating angle, longitudinal vehicle speed and the like, are transmitted on the CAN bus. The open-loop control module 2 queries a torque distribution coefficient two-dimensional table according to current running parameters of the vehicles such as vehicle speed, road adhesion coefficient, longitudinal acceleration, lateral acceleration and road gradient to obtain torque distribution coefficients corresponding to all the parameters, and then processes the torque distribution coefficients of all the parameters to obtain open-loop torque distribution coefficients; meanwhile, the expected yaw rate is obtained by looking up a table through the expected yaw rate obtaining module 3 according to the rotation angle of the steering wheel on the CAN bus and the longitudinal vehicle speed, wherein the table look-up calculation is common knowledge in the field and is not repeated herein;
the actual yaw rate of the vehicle is detected by the yaw rate detection module 4, in this embodiment, a yaw rate sensor is used to detect the actual yaw rate of the vehicle and send the detected actual yaw rate to the difference calculation module 51 in the fuzzy PID control module 5, the difference calculation module 51 calculates the difference between the desired yaw rate and the actual yaw rate to obtain a yaw rate difference, and sends the yaw rate difference to the change rate calculation module 52, the PID controller 54 and the fuzzy controller 53 in the fuzzy PID control module 5, and the change rate calculation module 52 calculates the difference between the yaw rates sent from the difference calculation module 51 at the front and back moments to obtain a difference change rate and sends the difference change rate to the fuzzy controller 53; the fuzzy controller 53 fuzzifies the yaw rate difference calculated by the difference calculation module 51 and the difference change rate calculated by the change rate calculation module 52, finds out output quantities according to a fuzzy rule table to optimize in real time to obtain three parameters of Kp, Ki and Kd and transmits the parameters to the PID controller 54, and the PID controller 54 performs PID operation according to the three parameters of Kp, Ki and Kd obtained by the fuzzy controller 53 and the yaw rate difference calculated by the difference calculation module 51 to obtain a closed-loop torque distribution coefficient;
the obtained open-loop torque distribution coefficient and the closed-loop torque distribution coefficient are both sent to a torque distribution control module 6, the torque distribution control module 6 adds the open-loop torque distribution coefficient and the closed-loop torque distribution coefficient to obtain a final torque distribution coefficient, and then the front axle torque and the rear axle torque are redistributed according to the obtained torque distribution coefficient, the obtained torque distribution coefficient is firstly defined in a control device and is defined as the front axle torque distribution coefficient or the rear axle torque distribution coefficient, in the embodiment, the obtained torque distribution coefficient is defined as the front axle torque distribution coefficient and is represented by a symbol mu, and then the rear axle torque distribution coefficient is 1-mu. And calculating the front axle request torque and the rear axle request torque as the actual required torque of the driver and the front axle torque distribution coefficient or the rear axle torque distribution coefficient to obtain the required torque. The actual required torque of the driver can be calculated according to the current vehicle speed and the opening degree of the accelerator pedal by looking up a table, and the calculation of the actual required torque of the driver is common knowledge in the field and is not described in detail herein.
Example two:
the technical solution in this embodiment is basically the same as that in the first embodiment, except that, as shown in fig. 2, the four-wheel drive yaw control method based on fuzzy PID further includes: the maximum desired yaw rate is calculated from the road surface adhesion coefficient, and the desired yaw rate obtained as described above is limited to the maximum desired yaw rate.
Wherein the maximum desired yaw rate is obtained by the following formula one:
wherein,
the maximum lateral acceleration is obtained by the following formula two:
wherein rt is a correction factor, and is generally 0.7; mu is the road surface adhesion coefficient; g is the acceleration of gravity; vxThe real-time speed of the vehicle.
As shown in fig. 6, the four-wheel-drive vehicle yaw control apparatus based on fuzzy PID further includes a desired yaw rate limiting module 8 connected to the desired yaw rate obtaining module 3 and the signal acquisition module 1, wherein the desired yaw rate limiting module 8 performs calculation according to the road adhesion coefficient obtained by the signal acquisition module 1 to obtain a maximum desired yaw rate, and transmits the maximum desired yaw rate to the desired yaw rate obtaining module 3, and the desired yaw rate obtaining module 3 limits the desired yaw rate within the maximum desired yaw rate, and transmits the maximum desired yaw rate to a difference value calculating module 51 in the fuzzy PID control module 5.
Example three:
the technical solution in this embodiment is basically the same as that in the first embodiment, except that, as shown in fig. 3, the four-wheel drive yaw control method based on fuzzy PID further includes: and adjusting the conversion rate of the obtained expected yaw rate according to the rotating speed of the steering wheel, and specifically operating as follows: when the steering wheel speed is greater than the preset speed value, the rate of change of the control desired yaw rate is decreased as the steering wheel speed increases.
As shown in fig. 7, the four-wheel-drive vehicle yaw control device based on the fuzzy PID further includes a transformation rate adjusting module 7 connected to the desired yaw rate obtaining module 3 and the signal acquisition module 1, wherein the transformation rate adjusting module 7 adjusts the time for obtaining the desired yaw rate according to the steering wheel rotation speed obtained by the signal acquisition module 1 and transmits the adjusted time to the desired yaw rate obtaining module 3; the interval time of the desired yaw rate being transmitted to the fuzzy PID control module 5 is controlled by the desired yaw rate acquisition module 3 according to the adjustment result transmitted by the conversion rate adjustment module 7.
Example four:
the technical solution in this embodiment is basically the same as the technical solution in the second embodiment, except that, as shown in fig. 4, the four-wheel drive vehicle yaw control method based on fuzzy PID further includes: and adjusting the conversion rate of the obtained expected yaw rate according to the rotating speed of the steering wheel, and specifically operating as follows: when the steering wheel speed is greater than the preset speed value, the rate of change of the control desired yaw rate is decreased as the steering wheel speed increases.
As shown in fig. 8, the four-wheel-drive vehicle yaw control device based on the fuzzy PID further includes a transformation rate adjusting module 7 connected to the desired yaw rate obtaining module 3 and the signal acquisition module 1, wherein the transformation rate adjusting module 7 adjusts the time for obtaining the desired yaw rate according to the steering wheel rotation speed obtained by the signal acquisition module 1 and transmits the adjusted time to the desired yaw rate obtaining module 3; the interval time of the desired yaw rate being transmitted to the fuzzy PID control module 5 is controlled by the desired yaw rate acquisition module 3 according to the adjustment result transmitted by the conversion rate adjustment module 7.
The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.
Claims (10)
1. A four-wheel drive vehicle yaw control method based on fuzzy PID is characterized by comprising the following steps:
performing table lookup according to the current operating parameters of the vehicle to obtain an open-loop torque distribution coefficient;
obtaining an expected yaw angular speed according to the rotation angle of the steering wheel and the longitudinal speed;
calculating the difference between the expected yaw rate and the actual yaw rate to obtain a yaw rate difference, and obtaining a difference change rate according to the yaw rate difference obtained at the previous moment and the later moment;
carrying out fuzzy PID control on the difference value of the yaw angular velocity and the change rate of the difference value to obtain a closed-loop torque distribution coefficient;
and distributing the front axle torque and the rear axle torque according to the open-loop torque distribution coefficient and the closed-loop torque distribution coefficient to obtain the front axle requested torque and the rear axle requested torque.
2. The fuzzy PID based four-wheel drive vehicle yaw control method according to claim 1, further comprising:
the maximum desired yaw rate is calculated from the road surface adhesion coefficient, and the desired yaw rate obtained as described above is limited to the maximum desired yaw rate.
3. The fuzzy PID based four-wheel drive vehicle yaw control method of claim 2, wherein the maximum desired yaw rate is obtained by one of the following equations:
wherein,
the maximum lateral acceleration is obtained by the following formula two:
wherein rt is a correction factor; mu is the road surface adhesion coefficient; g is the acceleration of gravity; vxThe real-time speed of the vehicle.
4. The fuzzy PID based four-wheel drive yaw control method according to claim 1, 2 or 3, further comprising:
the rate of change of the desired yaw rate obtained as described above is adjusted according to the steering wheel speed.
5. The fuzzy PID based yaw control method for four-wheel drive vehicle according to claim 4, wherein the operation of adjusting the rate of change of the desired yaw rate obtained as a function of the steering wheel speed is:
when the steering wheel speed is greater than the preset speed value, the rate of change of the control desired yaw rate is decreased as the steering wheel speed increases.
6. The fuzzy PID based four wheel drive yaw control method of claim 1, wherein the current vehicle operating parameters include vehicle speed, road adhesion coefficient, longitudinal acceleration, lateral acceleration and road grade transmitted over a CAN bus.
7. Four-wheel drive yaw control device based on fuzzy PID, comprising a signal acquisition module (1) for acquiring current running parameters of a vehicle, characterized by further comprising:
the open-loop control module (2) is used for looking up the current operating parameters of the vehicle to obtain an open-loop torque distribution coefficient;
the expected yaw rate acquisition module (3) is used for acquiring an expected yaw rate according to the steering wheel rotation angle signal and the longitudinal vehicle speed signal acquired by the signal acquisition module (1);
a yaw-rate detection module (4) for detecting an actual yaw rate of the vehicle;
the fuzzy PID control module (5) is used for obtaining a yaw velocity difference according to the expected yaw velocity and the actual yaw velocity, and further obtaining a difference change rate according to the yaw velocity difference at the front moment and the rear moment; the system is also used for carrying out fuzzy PID control on the difference value of the yaw angular velocity and the change rate of the difference value so as to obtain a closed-loop torque distribution coefficient;
and the torque distribution control module (6) is used for distributing the front axle torque and the rear axle torque according to the open-loop torque distribution coefficient and the closed-loop torque distribution coefficient to obtain the front axle requested torque and the rear axle requested torque.
8. The fuzzy PID based four wheel drive yaw control apparatus of claim 7, further comprising:
the conversion rate adjusting module (7) is used for adjusting the time for obtaining the expected yaw rate according to the rotating speed of the steering wheel obtained by the signal acquisition module (1) and transmitting the time to the expected yaw rate obtaining module (3);
the expected yaw rate acquisition module (3) is used for controlling the interval time of the expected yaw rate transmitted to the fuzzy PID control module (5) according to the adjustment result transmitted by the conversion rate adjustment module (7).
9. The fuzzy PID based four wheel drive yaw control apparatus of claim 7 or 8, further comprising:
the expected yaw rate limiting module (8) is used for calculating according to the road adhesion coefficient acquired by the signal acquisition module (1) to acquire the maximum expected yaw rate and transmitting the maximum expected yaw rate to the expected yaw rate acquisition module (3);
the desired yaw-rate acquisition module (3) is configured to limit the desired yaw-rate to within a maximum desired yaw-rate.
10. The fuzzy PID based four wheel drive yaw control device according to claim 7 or 8, characterized in that the fuzzy PID control module (5) comprises:
a difference value calculating module (51) for calculating the difference value between the expected yaw rate delivered by the expected yaw rate obtaining module (3) and the actual yaw rate delivered by the yaw rate detecting module (4) to obtain a yaw rate difference value;
a change rate calculation module (52) for calculating the difference of the yaw rate calculated by the difference calculation module (51) at the front and rear moments to obtain a difference change rate;
the fuzzy controller (53) is used for fuzzifying the difference value of the yaw velocity calculated by the difference value calculating module (51) and the difference change rate calculated by the change rate calculating module (52) and finding out output quantity according to a fuzzy rule table to optimize in real time to obtain three parameters of Kp, Ki and Kd;
and the PID controller (54) is used for carrying out PID operation according to the three parameters Kp, Ki and Kd obtained by the fuzzy controller (53) and the yaw rate difference value calculated by the difference value calculating module (51) to obtain a closed-loop torque distribution coefficient.
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