Clutch pressure tracking control method, device and system

Abstract

The present invention discloses a clutch pressure tracking control method, device and system. The method comprises: obtaining the optimal control pressure trajectory of the clutch as the expected input pressure signal; constructing a sliding surface function of the pressure tracking error according to the difference between the expected input pressure signal and the actual input pressure signal; and establishing an adaptive control law with uncertain interference control items and switching control items according to the sliding surface function. The present invention provides a clutch pressure tracking control method, device and system, which can reduce the influence of the engagement or disengagement smoothness caused by the clutch pressure tracking deviation on the driving experience and improve the clutch life cycle.

Description

Technical Field

[0001] Embodiments of the present invention relate to the technical field of clutch control, and in particular to a clutch pressure tracking control method, device and system. Background Art

[0002] Bulldozers are a common type of earth-moving machinery. They have comprehensive functions such as digging, shoveling, pushing or leveling soil and gravel. They are widely used in water conservancy construction, road construction, airport construction, mining, farmland improvement and other engineering constructions, among which hydraulic mechanical power transmission accounts for a high proportion. During the cyclic operation, they frequently turn and shift gears, which places high demands on the clutch engagement or disengagement control involved in the power transmission system.

[0003] The existing technology currently only realizes the clutch engagement or release control function through open-loop control or closed-loop control of simple numerical deviation. The engagement or release control still has certain shortcomings. Summary of the invention

[0004] The present invention provides a clutch pressure tracking control method, device and system, which reduce the influence of engagement or disengagement smoothness caused by clutch pressure tracking deviation on driving experience and improve the clutch life cycle.

[0005] In a first aspect, an embodiment of the present invention provides a clutch pressure tracking control method, comprising:

[0006] Obtaining an optimal control pressure trajectory of the clutch as a desired input pressure signal;

[0007] Constructing a sliding surface function of a pressure tracking error according to a difference between the expected input pressure signal and the actual input pressure signal;

[0008] An adaptive control law with an uncertain disturbance control term and a switching control term is established according to the sliding surface function.

[0009] Optionally, the uncertain interference terms include: solenoid valve electromagnetic force fluctuation uncertainty, electro-hydraulic valve to clutch pressure uncertainty, electro-hydraulic valve to clutch flow uncertainty, load spectrum uncertainty, conversion to clutch equivalent pressure uncertainty, clutch characteristic parameter uncertainty and external interference white noise with random characteristics.

[0010] Optionally, establishing an adaptive control law with an uncertain interference control term and a switching control term according to the sliding surface function includes:

[0011] Obtaining the intermediate virtual input control law according to the sliding surface function, wherein the intermediate virtual input control law includes a switching gain coefficient;

[0012] The adaptive control law is constructed according to the switching gain coefficient, wherein the adaptive control law saturation function sat(s) or S-type function sigmoid(s) replaces the sign function sgn(s).

[0013] Optionally, after establishing the mapping relationship between the intermediate virtual input control law and the actual input pressure, it also includes:

[0014] The system stability of the control method is determined and analyzed.

[0015] Optionally, the determination and analysis of the system stability of the control method includes:

[0016] Construct the Lyapunov function and take its derivative;

[0017] Substituting the intermediate virtual input control law into the derivative of the Lyapunov function;

[0018] The derivative is negative and the control method satisfies the asymptotic stability condition.

[0019] In a second aspect, an embodiment of the present invention provides a clutch pressure tracking control device, comprising:

[0020] An acquisition module, used for acquiring an optimal control pressure trajectory of the clutch as an expected input pressure signal;

[0021] A sliding surface function module, used for constructing a sliding surface function of a pressure tracking error according to a difference between the expected input pressure signal and the actual input pressure signal;

[0022] The adaptive control module is used to establish an adaptive control law with an uncertain interference control term and a switching control term according to the sliding surface function.

[0023] Optionally, the clutch pressure tracking control device further includes:

[0024] A first calculation module, configured to obtain the intermediate virtual input control law according to the sliding surface function, wherein the intermediate virtual input control law includes a switching gain coefficient;

[0025] The second calculation module is used to construct the adaptive control law according to the switching gain coefficient, wherein the adaptive control law saturation function sat(s) or S-type function sigmoid(s) replaces the sign function sgn(s).

[0026] Optionally, the clutch pressure tracking control device further includes:

[0027] The stability analysis module is used to determine and analyze the system stability of the control method.

[0028] In a third aspect, an embodiment of the present invention provides a clutch pressure tracking control system, comprising a clutch pressure tracking device, an electro-hydraulic actuator system model, a control module and an operation module as described in any of the embodiments of the present invention; wherein the electro-hydraulic actuator system model includes a pressure control model and a clutch actuator;

[0029] The operation module is used to output an operation feedback signal;

[0030] The control module is connected to the operation module and the clutch pressure tracking device respectively; the control module is used to obtain the expected input pressure signal according to the feedback signal;

[0031] The clutch pressure tracking device is connected to the pressure control model; the pressure control model is connected to the clutch actuator; the clutch actuator is connected to the operation module;

[0032] The clutch pressure tracking device is used to output a control signal according to the expected input pressure signal; the pressure control model is used to output the actual input pressure signal according to the control signal;

[0033] The clutch actuator is used to control the operation module to perform an action according to the actual input pressure signal.

[0034] The technical solution provided by the present invention takes into account the influence of pressure tracking control deviation caused by factors such as model uncertainty and external interference corresponding to the application scenario, and constructs a control method integrating uncertain interference terms by designing a sliding membrane controller and an adaptive law to achieve precise tracking of clutch control pressure, thereby avoiding design uniformity, effectively reducing the influence of engagement or disengagement smoothness caused by clutch pressure tracking deviation on driving experience, and improving the life cycle of the clutch. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic flow chart of a clutch pressure tracking control method is provided for an embodiment of the present invention.

[0036] Figure 2 A structural diagram of an adaptive sliding membrane controller provided in an embodiment of the present invention.

[0037] Figure 3 A flow chart of another clutch pressure tracking control method is provided for an embodiment of the present invention.

[0038] Figure 4 A structural schematic diagram of another clutch pressure tracking device is provided for an embodiment of the present invention.

[0039] Figure 5 A structural schematic diagram of another clutch pressure tracking system is provided for an embodiment of the present invention. DETAILED DESCRIPTION

[0040] 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.

[0041] Figure 1 A flow chart of a clutch pressure tracking control method is provided for an embodiment of the present invention. This embodiment is applicable to clutch pressure tracking control. The method can be executed by a clutch pressure tracking control device, which can be implemented in hardware and / or software. The method specifically includes the following steps:

[0042] S110, obtaining an optimal clutch control pressure trajectory as a desired input pressure signal;

[0043] Specifically, the expected input signal pc' is the optimal expected input pressure signal considering the three factors of engagement or disengagement time, sliding friction work and impact degree, wherein the process of obtaining the optimal control pressure trajectory includes: determining the engagement or disengagement time boundary, the impact degree expression is approximated by the variable vehicle speed as the variable torque function, the sliding friction work expression is the time integral of the stage from the beginning of contact of the clutch friction plate to the stage where the friction plate speed difference is zero and the transmitted torque; constructing the state space equation of the friction plate speed difference and torque change; constructing the quadratic performance index functional of the impact degree and sliding friction work; establishing the Hamiltonian function based on the state space equation and the quadratic performance index functional, and obtaining the optimal control law based on its extreme value conditions and Pontryagin maximization principle; the engagement or disengagement torque under the time state can be obtained under the time integration and weight combination of the optimal control law; and obtaining the optimal control pressure trajectory through the equivalent variable conversion of the clutch structural characteristic parameters.

[0044] S120, constructing a sliding surface function of a pressure tracking error according to a difference between an expected input pressure signal and an actual input pressure signal;

[0045] Specifically, when designing a sliding mode controller, the deviation variable is obtained according to the actual input pressure signal of the clutch asymptotically approaching the expected input pressure signal, the error equation e is constructed according to the deviation variable, and the differential equation e' of the difference is obtained by taking the derivative of the error equation e. Without loss of generality, a sliding surface function s including the error equation e and its differential equation e' is constructed;

[0046] S130. Establishing an adaptive control law having an uncertain disturbance control term and a switching control term according to the sliding surface function.

[0047] Specifically, the adaptive control law is switched through the sliding surface function s, and the switching is performed according to a certain algorithm. Therefore, the system will present two different closed-loop structures. When the system trajectory leaves the sliding plane, this structural switching control will always bring its state trajectory back to the sliding plane asymptotically, showing a stable convergence effect. Figure 2 A structural diagram of an adaptive sliding film controller provided by an embodiment of the present invention, see Figure 2 , adaptive control will dynamically adjust to reduce the error with the actual requirements, take the feedback control system composed of sliding mode controller as the inner loop, design the adaptive control outer loop, the controlled object is the electro-hydraulic actuator system model, where the electro-hydraulic actuator system model includes the electro-hydraulic valve pressure control model and the clutch actuator model. The outer loop is the adaptive adjustment loop of the sliding mode controller parameters, and its function is to continuously measure the input u of the controlled object, the actual input pressure signal pc, and the deviation variable between the expected input pressure signal pc' and the actual input pressure signal pc, and then update the structure, parameters or control action of the inner loop controller according to a specific design method to achieve the complementary advantages of the two controls.

[0048] After the sliding surface function s is selected, the adaptive control law is designed. The adaptive control law includes two parts: uncertain interference control term and switching control term. The uncertain interference control term is used to eliminate the known nonlinear part of the original dynamics, and the switching control term is used to offset the influence of the system uncertainty and construct a new sliding mode. Optionally, the clutch force balance model and motion model, clutch oil cylinder cavity flow-pressure dynamic model, etc. constructed according to the application scenario can be used to obtain the involved uncertain interference terms based on the use data test, including: solenoid valve electromagnetic force fluctuation uncertainty, electro-hydraulic valve clutch pressure uncertainty, electro-hydraulic valve clutch flow uncertainty, load spectrum uncertainty, conversion to clutch equivalent pressure uncertainty, clutch characteristic parameter uncertainty and external interference white noise with random characteristics. Among them, the electromagnetic force fluctuation uncertainty of the solenoid valve is a combination of electromagnetic force fluctuation uncertainty under different currents, which is affected by factors such as changes in ambient temperature and changes in the magnetic ring structure during armature movement. Based on the comprehensive factors of the bulldozer clutch engagement or disengagement process, after the action signal starts to be executed, the characteristics of the electro-hydraulic valve, external random interference and the uncertainty of the actuator are taken into account, and a control method with adaptive robust function is used to achieve accurate tracking of the expected pressure trajectory signal.

[0049] The technical solution provided by the present invention takes into account the influence of pressure tracking control deviation caused by factors such as model uncertainty and external interference corresponding to the application scenario, and constructs a control method integrating uncertain interference terms by designing a sliding membrane controller and an adaptive law to achieve precise tracking of clutch control pressure, thereby avoiding design uniformity, effectively reducing the influence of engagement or disengagement smoothness caused by clutch pressure tracking deviation on driving experience, and improving the life cycle of the clutch.

[0050] Optionally, an adaptive control law with an uncertain disturbance control term and a switching control term is established according to the sliding surface function, including:

[0051] An intermediate virtual input control law is obtained according to the sliding surface function, wherein the intermediate virtual input control law includes a switching gain coefficient;

[0052] An adaptive control law is constructed according to the switching gain coefficient, wherein the adaptive control law saturation function sat(s) or S-type function sigmoid(s) replaces the sign function sgn(s).

[0053] Specifically, the sliding surface function is differentiated, and an intermediate virtual input control law ui with a switching control item is obtained through mathematical changes to achieve the actual input pressure signal gradually approaching the expected input pressure signal, wherein the intermediate virtual input control law ui contains an adaptive gain coefficient. With respect to the adaptive gain coefficient, considering the requirements of the adaptive gain coefficient in different stages of the sliding mode, a parameter adaptive control law is designed to transform the conventional sliding mode intermediate virtual input control law into an adaptive control law. Considering the continuity and smoothness of the change of the adaptive law, the saturation function sat(s) or the S-type function sigmoid(s) of the adaptive control law replaces the sign function sgn(s).

[0054] Figure 3 A flow chart of another clutch pressure tracking control method is provided for an embodiment of the present invention, see Figure 3 , the method specifically comprises the following steps:

[0055] S210, obtaining an optimal clutch control pressure trajectory as a desired input pressure signal;

[0056] S220, constructing a sliding surface function of a pressure tracking error according to a difference between an expected input pressure signal and an actual input pressure signal;

[0057] S230: Establish an adaptive control law with an uncertain disturbance control term and a switching control term according to the sliding surface function.

[0058] S240. Conduct determination and analysis on the system stability of the control method.

[0059] Specifically, after the adaptive sliding mode controller is designed, it is necessary to conduct stability analysis. The system trajectory motion process of sliding mode control includes the approach motion stage and the sliding mode stage. Only by ensuring that the system is stable in both stages can the reliability of the system be guaranteed. The design of the sliding mode control law is directly related to whether the system can stably enter the sliding mode stage from the approach motion stage, and the stability of the sliding mode stage can be guaranteed in the design stage of the control system.

[0060] Optionally, a determination analysis of the system stability of the control method may include:

[0061] Construct the Lyapunov function and take its derivative;

[0062] Substitute the intermediate virtual input control law into the derivative of the Lyapunov function;

[0063] The derivative is negative and the control method satisfies the asymptotic stability condition.

[0064] Specifically, the method of constructing Lyapunov function is used to analyze the system stability, and then the derivative is derived. Then, the adaptive control law is substituted into the derivative of Lyapunov function. Through mathematical processing, it is proved that the derivative is negative semi-definite, that is, the system meets the asymptotic stability condition and the error can converge in a finite time. After the sliding mode controller is designed, in view of the poor approaching effect and chattering problems caused by the fixed controller parameters of conventional sliding mode control, an adaptive control algorithm is used to adaptively adjust the sliding mode switching gain and boundary layer thickness. On the one hand, the approaching speed of the sliding mode approaching motion process is improved, and on the other hand, when the sliding mode control process enters the sliding mode region, the sliding mode chattering is reduced to obtain the best between the tracking error and the chattering amplitude.

[0065] Figure 4 A schematic diagram of another clutch pressure tracking device is provided for an embodiment of the present invention. Figure 4 ,include:

[0066] An acquisition module 110 is used to acquire an optimal clutch control pressure trajectory as an expected input pressure signal;

[0067] A sliding surface function module 120, used to construct a sliding surface function of a pressure tracking error according to a difference between an expected input pressure signal and an actual input pressure signal;

[0068] The adaptive control module 130 is used to establish an adaptive control law with an uncertain disturbance control term and a switching control term according to the sliding surface function.

[0069] Specifically, the expected input signal pc' is the optimal expected input pressure signal considering the three factors of engagement or disengagement time, sliding friction work and impact degree. When designing the sliding mode controller, the sliding surface function module 120 obtains the deviation variable according to the actual input pressure signal of the clutch asymptotically approaching the expected input pressure signal, constructs the error equation e according to the deviation variable, and obtains the differential equation e' of the difference by taking the derivative of the error equation e. Without loss of generality, a sliding surface function s including the error equation e and its differential equation e' is constructed; the adaptive control law is switched through the sliding surface function s, and the switching is performed according to a certain algorithm. Therefore, the system will present two different closed-loop structures. When the system trajectory leaves the sliding plane, this structural switching control will always bring its state trajectory back to the sliding plane asymptotically, presenting a stable convergence effect.

[0070] After the sliding surface function s is selected, the adaptive control module 130 designs the adaptive control law u. The adaptive control law u includes two parts: the uncertain interference control term and the switching control term. The uncertain interference control term is used to eliminate the known nonlinear part of the native dynamics, and the switching control term is used to offset the influence of the system uncertainty term and construct a new sliding mode. Optionally, the clutch force balance model and motion model, clutch oil cylinder cavity flow-pressure dynamic model, etc. constructed according to the application scenario can be obtained based on the use data test. The involved uncertain interference terms include: electromagnetic force fluctuation uncertainty of the solenoid valve, electro-hydraulic valve clutch pressure uncertainty, electro-hydraulic valve clutch flow uncertainty, load spectrum uncertainty, conversion to clutch equivalent pressure uncertainty, clutch characteristic parameter uncertainty, and external interference white noise with random characteristics. Among them, the electromagnetic force fluctuation uncertainty of the solenoid valve is a comprehensive electromagnetic force fluctuation uncertainty under different currents, which is affected by factors such as changes in ambient temperature and changes in the magnetic ring structure during the movement of the armature. Based on the comprehensive factors of the bulldozer clutch engagement or disengagement process, after the action signal starts to be executed, the characteristics of the electro-hydraulic valve, external random interference and the uncertainty of the actuator are taken into account, and a control method with adaptive robust function is used to achieve accurate tracking of the expected pressure trajectory signal.

[0071] Optionally, the clutch pressure tracking control device also includes:

[0072] A first calculation module is used to obtain an intermediate virtual input control law according to the sliding surface function, wherein the intermediate virtual input control law includes a switching gain coefficient;

[0073] The second calculation module is used to construct an adaptive control law according to the switching gain coefficient, wherein the adaptive control law saturation function sat(s) or S-type function sigmoid(s) replaces the sign function sgn(s).

[0074] Optionally, the clutch pressure tracking control device also includes:

[0075] The stability analysis module is used to determine and analyze the system stability of the control method.

[0076] The clutch pressure tracking control device provided in an embodiment of the present invention and the clutch pressure tracking control method provided in any embodiment of the present invention belong to the same inventive concept and have corresponding beneficial effects. For technical details not detailed in this embodiment, please refer to the clutch pressure tracking control method provided in any embodiment of the present invention.

[0077] Figure 5 A schematic diagram of another clutch pressure tracking system is provided for an embodiment of the present invention. Figure 5 , comprising: a clutch pressure tracking device of any embodiment of the present invention, an electro-hydraulic actuator system model, a control module and an operation module;

[0078] The electro-hydraulic actuator system model includes the pressure control model and the clutch actuator;

[0079] The operation module is used to output the feedback signal of the operation;

[0080] The control module is connected to the operation module and the clutch pressure tracking device respectively; the control module is used to obtain the expected input pressure signal according to the feedback signal;

[0081] The clutch pressure tracking device is connected to the pressure control model; the pressure control model is connected to the clutch actuator; the clutch actuator is connected to the operation module;

[0082] The clutch pressure tracking device is used to output a control signal according to the expected input pressure signal; the pressure control model is used to output an actual input pressure signal according to the control signal;

[0083] The clutch actuator is used to control the operation of the operation module according to the actual input pressure signal. The operation module includes the engine, power take off device (PTO), torque converter, gearbox, front and rear drive shafts, drive axle, wheel reducer, etc. The feedback signals output by the operation module include engagement or disengagement time, sliding friction work, impact degree and transmission load.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A clutch pressure tracking control method, characterized in that: include: Obtaining an optimal control pressure trajectory of the clutch as a desired input pressure signal; Constructing a sliding surface function of a pressure tracking error according to a difference between the expected input pressure signal and the actual input pressure signal; An adaptive control law with an uncertain disturbance control term and a switching control term is established according to the sliding surface function.

2. The clutch pressure tracking control method according to claim 1, characterized in that: The uncertain interference terms include: solenoid valve electromagnetic force fluctuation uncertainty, electro-hydraulic valve to clutch pressure uncertainty, electro-hydraulic valve to clutch flow uncertainty, load spectrum uncertainty, conversion to clutch equivalent pressure uncertainty, clutch characteristic parameter uncertainty and external interference white noise with random characteristics.

3. The clutch pressure tracking control method according to claim 1, characterized in that: An adaptive control law having an uncertain disturbance control term and a switching control term is established according to the sliding surface function, including: Obtaining an intermediate virtual input control law according to the sliding surface function, wherein the intermediate virtual input control law includes a switching gain coefficient; The adaptive control law is constructed according to the switching gain coefficient, wherein the adaptive control law saturation function sat(s) or S-type function sigmoid(s) replaces the sign function sgn(s).

4. The clutch pressure tracking control method according to claim 1, characterized in that: After establishing the mapping relationship between the intermediate virtual input control law and the actual input pressure, it also includes: The system stability of the control method is determined and analyzed.

5. The clutch pressure tracking control method according to claim 4, characterized in that: The determination and analysis of the system stability of the control method includes: Construct the Lyapunov function and take its derivative; Substituting the intermediate virtual input control law into the derivative of the Lyapunov function; The derivative is negative and the control method satisfies the asymptotic stability condition.

6. A clutch pressure tracking control device, characterized in that: include: An acquisition module, used for acquiring an optimal control pressure trajectory of the clutch as an expected input pressure signal; A sliding surface function module, used for constructing a sliding surface function of a pressure tracking error according to a difference between the expected input pressure signal and the actual input pressure signal; The adaptive control module is used to establish an adaptive control law with an uncertain interference control term and a switching control term according to the sliding surface function.

7. The clutch pressure tracking control device according to claim 6, characterized in that: Also includes: A first calculation module, configured to obtain an intermediate virtual input control law according to the sliding surface function, wherein the intermediate virtual input control law includes a switching gain coefficient; The second calculation module is used to construct the adaptive control law according to the switching gain coefficient, wherein the adaptive control law saturation function sat(s) or S-type function sigmoid(s) replaces the sign function sgn(s).

8. The clutch pressure tracking control device according to claim 6, characterized in that: Also includes: The stability analysis module is used to determine and analyze the system stability of the control method.

9. A clutch pressure tracking control system, characterized in that: It comprises the clutch pressure tracking device according to any one of claims 6 to 8, an electro-hydraulic actuator system model, a control module and an operation module; wherein the electro-hydraulic actuator system model comprises a pressure control model and a clutch actuator; The operation module is used to output an operation feedback signal; The control module is connected to the operation module and the clutch pressure tracking device respectively; the control module is used to obtain the expected input pressure signal according to the feedback signal; The clutch pressure tracking device is connected to the pressure control model; the pressure control model is connected to the clutch actuator; the clutch actuator is connected to the operation module; The clutch pressure tracking device is used to output a control signal according to the expected input pressure signal; the pressure control model is used to output the actual input pressure signal according to the control signal; The clutch actuator is used to control the operation module to perform an action according to the actual input pressure signal.

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