Oil pressure time-frequency domain combined control method of clutch hydraulic system

Abstract

The application discloses an oil pressure time-frequency domain combined control method of a clutch hydraulic system, and the oil pressure control under different working conditions is realized by using the time-frequency domain combined control method according to the oil pressure demand of the clutch hydraulic system and the characteristics of global fast sliding film time domain control and loop shaping frequency domain control. The application has the advantages of fast response time, high steady-state accuracy and small overshoot.

Description

Technical Field

[0001] This invention relates to the field of hydraulic pressure control in clutch hydraulic systems, and particularly to a time-frequency domain combined control method for hydraulic pressure in clutch hydraulic systems. Background Technology

[0002] When a vehicle shifts gears, the hydraulic pressure control of the clutch affects the performance of the transmission system. Deviations in hydraulic pressure during the shifting process can cause significant shocks, severely impacting ride comfort. It can also generate significant slippage work, causing the clutch to overheat. Increased temperature can easily lead to adhesion and damage of the friction plates, shortening the clutch's service life.

[0003] For the clutch hydraulic system of a vehicle, current control methods have poor anti-interference capabilities and cannot simultaneously meet the requirements of fast response time and low variability. Commonly used PID control methods suffer from large overshoot, slow response time, and large variability; time-domain control based on sliding film theory has fast response time and small steady-state error, but large overshoot; frequency-domain control based on "loop shaping" has strong anti-interference capabilities, small overshoot, and low variability, but slow response time. This is the area that this application needs to focus on improving. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a time-frequency domain combined control method for hydraulic pressure in a clutch hydraulic system, which has fast response time, small overshoot, high steady-state accuracy and low fluctuation.

[0005] To address the above technical problems, this invention provides a time-frequency domain combined control method for hydraulic pressure in a clutch hydraulic system. Based on the hydraulic pressure requirements of the clutch hydraulic system, and combining the characteristics of global rapid sliding film time-domain control and loop-forming frequency-domain control, the time-frequency domain combined control method achieves hydraulic pressure control under different operating conditions, including the following steps:

[0006] Step S1: Obtain the target oil pressure and external disturbance conditions of clutch engagement, assign certain weights to different disturbances, calculate the magnitude of external disturbances and set values, and determine the preliminary control method to be adopted;

[0007] External disturbances refer to changes in oil temperature and oil viscosity;

[0008] Step S2: Based on external disturbances, response time, overshoot, fluctuation degree and steady-state error parameters, comprehensively select time-domain control, frequency-domain control or combined control. The weight of combined control is optimized based on steady-state error requirements to achieve the target effect.

[0009] A mathematical model of the hydraulic system is established using system identification methods. A global fast sliding film time-domain control is established with the target pressure of the clutch as the input, and the corresponding global dynamic sliding film surface and global sliding film control law are designed.

[0010] To design a frequency domain control algorithm based on loop shaping, we first use the frequency domain model building technique based on the characteristic calibration method to design the desired system frequency domain control strategy according to the system characteristics, and then design H... ∞ A controller is a control algorithm that controls the controlled object to ensure that its response performance and robustness are within requirements.

[0011] The beneficial effects of this invention are: compared with traditional control methods, it has stronger robustness and advantages such as fast response time, high steady-state accuracy, and small overshoot. Attached Figure Description

[0012] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0013] Figure 1 This is a flowchart illustrating the combined control of the clutch hydraulic system according to a specific embodiment of the present invention. Detailed Implementation

[0014] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0015] Figure 1 A flowchart illustrating the combined control of the clutch hydraulic system according to an embodiment of the present invention is shown. Figure 1 As shown, this invention provides a time-frequency domain combined control method for hydraulic pressure in a clutch hydraulic system, with the following specific steps:

[0016] Step S1: After the vehicle starts, obtain the target oil pressure for clutch engagement and the external disturbance conditions;

[0017] External disturbances include changes in oil temperature and oil viscosity, and different disturbances are assigned certain weights.

[0018] Calculate the magnitude of external interference and the set value, and determine whether each interference exceeds the set value;

[0019] Yes, proceed to step S2;

[0020] No, proceed to step S3;

[0021] Total external disturbance Q = n1T y +n2η y +n3S y n1, n2, and n3 are the interference weights, respectively, n1 + n2 + n3 = 1, T y ,

[0022] η y S yThese represent the percentage changes in oil temperature, oil viscosity, and other disturbances, respectively.

[0023] When the external disturbance is small, the percentage change of each disturbance is close to zero, that is, Q = 0;

[0024] The setpoint Q0 is set according to 50% of the maximum disturbance within the controllable range of the system, i.e., Q0 = 0.5Q. max ;

[0025] Step S2: Obtain the actual clutch oil pressure using time-domain control; Proceed to step S4;

[0026] Step S3: Obtain the actual clutch oil pressure using frequency domain control; Proceed to step S4;

[0027] Step S4: Determine whether the response time of the actual clutch oil pressure curve is less than the set value.

[0028] No, the oil pressure curve obtained after feedback correction is then subjected to time-domain control, and the process proceeds to step S2;

[0029] Yes, proceed to step S5;

[0030] Step S5: Determine whether the overshoot is less than the set value;

[0031] No, the oil pressure curve obtained after feedback correction is used for frequency domain control, and then proceed to step S3;

[0032] Yes, proceed to step S6;

[0033] Step S6: Determine whether the fluctuation level is less than the set value;

[0034] No, adopt time-frequency domain combined control, proceed to step S7;

[0035] Yes, proceed to step S8;

[0036] Step S7: Time-frequency domain combined control, and weight identification based on data;

[0037] The hydraulic pressure characteristics are extracted and identified through a large amount of data. The hydraulic pressure characteristics include the degree of fluctuation, overshoot, response rate and response delay. The initial weights of the time domain and frequency domain control methods are w1 and w2, respectively. Since the frequency domain control suppresses overshoot and fluctuation, the frequency domain control weight w2 is continuously increased and the time domain control weight w1 is decreased in subsequent iterative optimization.

[0038] Step S8: Determine whether the steady-state error is less than the set accuracy;

[0039] If not, then the weights of the time-frequency domain combined control are further optimized, and the oil pressure curve after feedback correction is then subjected to time-frequency domain combined control again; then it is further determined whether the steady-state error is less than the set accuracy, and if so, the control ends.

[0040] If yes, then control ends.

[0041] If the above control method fails to meet the control requirements after N rounds or if the control time exceeds T seconds, the optimal oil pressure control within N rounds or T seconds will be output, and a signal will be sent to remind the driver.

[0042] The control parameters in the above control method include response time, overshoot, fluctuation, and steady-state error. Among these, response time and steady-state error are the primary parameters, while overshoot and fluctuation are secondary parameters. The difference between primary and secondary parameters lies in whether a signal is sent to remind the driver.

[0043] For the primary parameter, response time, the time-domain control performs feedback corrections on the response time through N rounds. If, after 10 iterations, the target response time is still not met, the value closest to the target response time within those 10 iterations is output and a signal is sent to remind the driver. For the secondary parameter, overshoot, the frequency-domain control performs feedback corrections on the overshoot through N rounds. If, after 20 iterations, the target overshoot is still not met, the value closest to the target overshoot within those 20 iterations is output, and the next step is performed.

[0044] The N iterations and the time T here are consistent criteria, that is, the judgment is based on whether the number of iterations exceeds a certain value or the time spent on the iterations exceeds a certain value.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for combined time-frequency domain control of hydraulic pressure in a clutch hydraulic system, characterized in that: Based on the oil pressure requirements of the clutch hydraulic system, and combining the characteristics of global fast sliding film time-domain control and loop-forming frequency-domain control, a time-frequency domain combined control method was used to achieve oil pressure control under different operating conditions, including the following steps: Step S1: Obtain the target oil pressure and external disturbance conditions of clutch engagement, assign certain weights to different disturbances, calculate the magnitude of external disturbances and set values, and determine the preliminary control method to be adopted; Step S2: Based on external disturbances, response time, overshoot, fluctuation degree and steady-state error parameters, comprehensively select time-domain control, frequency-domain control or combined control. The weight of combined control is optimized based on steady-state error requirements to achieve the target effect. Step S1 includes the following steps: After the vehicle starts, obtain the target oil pressure for clutch engagement and the status of external disturbances; The external disturbances include changes in oil temperature and changes in oil viscosity, and different disturbances are assigned certain weights. Calculate the magnitude of external interference and the set value, and determine whether each interference exceeds the set value; Yes, the actual clutch oil pressure is obtained by using time-domain control; No, frequency domain control is used to obtain the actual clutch oil pressure; Step S2 includes the following steps: Determine whether the response time of the actual clutch oil pressure curve is less than the set value. No, the actual clutch oil pressure is obtained by performing time-domain control on the oil pressure curve obtained after feedback correction. Yes, proceed to the next step; Determine whether the overshoot is less than the set value; No, the actual clutch oil pressure is obtained by frequency domain control through the oil pressure curve obtained after feedback correction. Yes, proceed to the next step; Determine whether the fluctuation level is less than the set value; No, time-frequency domain combined control is adopted, and weight identification is based on data; Yes, determine whether the steady-state error is less than the set accuracy; No, perform weighted re-optimization of time-frequency domain combined control, and then perform time-frequency domain combined control again on the oil pressure curve after feedback correction; then further determine whether the steady-state error is less than the set accuracy, and if so, the control ends.

2. The hydraulic pressure time-frequency domain combined control method for the clutch hydraulic system according to claim 1, characterized in that: The time-frequency domain combined control extracts and identifies oil pressure characteristics through a large amount of data. The initial weights of the time-domain and frequency-domain control methods are w1 and w2, respectively. In subsequent iterative optimization, the frequency-domain control weight w2 continuously increases, while the time-domain control weight w1 decreases.

3. The hydraulic pressure time-frequency domain combined control method for the clutch hydraulic system according to claim 2, characterized in that: The hydraulic pressure characteristics include fluctuation level, overshoot, response rate, and response delay.

Images