A Method for Estimating Load Fluctuation and Feedback Control of a Hydraulic Steering Gear

Abstract

The present invention provides a method for estimating and feedback controlling the load fluctuation of a hydraulic steering gear. By setting the time constants of three typical load fluctuation situations and establishing a simplified approximate model, inputting the steering gear input command signal, comparing the difference between the model output signal and the steering gear output signal to obtain three load error signals, then performing a square integral operation, and selecting the smallest one as the load fluctuation situation closest to the actual situation; then designing a load identification compensation feedback signal according to the time constant of this situation, and at the same time designing a total load identification adjustment signal according to the load error signal of this situation, and combining it with the integral sliding mode signal formed by the valve-controlled cylinder piston displacement signal and the steering gear angle error signal and the finite-time switching softening signal to form the total hydraulic steering gear load identification control signal, thereby realizing the estimation of typical load fluctuations of the hydraulic steering gear, and at the same time using the load fluctuation estimation result to correct and compensate the sliding mode control, so as to further improve the dynamic performance of the steering gear.

Description

Technical Field

[0001] The present invention relates to the field of servo and motor design, and more particularly to a method for estimating and feedback controlling the load fluctuation of a hydraulic servo. Background Art

[0002] The load fluctuation of a hydraulic servo has an important impact on the overall operating performance and energy consumption of the servo. How to accurately perform more precise feedback control adjustment in response to load fluctuation changes is a very valuable issue, because on the one hand, it can improve the operating performance and quality of the servo, and on the other hand, it can also reduce unnecessary losses, mechanical wear, etc. For hydraulic servos used in aircraft or marine vessels, the load environment of the servo is completely different under different usage environments or different flight speed levels. If a feedback controller for low load is used to operate under high load conditions for a long time, it will inevitably reduce performance or affect the servo life; at the same time, if a feedback controller for high load is used to operate under low load conditions for a long time, corresponding chattering and other adverse problems will also occur. Currently, traditional hydraulic servos use the robustness of PID control to handle this problem, but this problem is not further divided. Based on the above background reasons, the present invention further divides the load conditions of the hydraulic servo, specifically divides it into three typical load conditions, which respectively represent high, medium, and low load conditions in actual operation, uses the prior knowledge obtained in actual work for modeling, and then performs online estimation and identification on it during the operation of the servo, so as to further use the identification results to feedback and adjust the parameters of the servo controller, thereby improving the control quality of the servo and enabling it to have the ability of automatic identification and adjustment of load fluctuation changes, so that the present invention has high practical application value.

[0003] It should be noted that the information disclosed in the above background art section is only used to enhance the understanding of the background of the present invention, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for estimating and feedback controlling the load fluctuation of a hydraulic servo, thereby overcoming the problems that the servo cannot automatically adapt to environmental changes and load fluctuations and cannot perform automatic adjustment due to defects in related technologies.

[0005] According to one aspect of the present invention, there is provided a method for estimating and feedback controlling the load fluctuation of a hydraulic servo, including the following six steps:

[0006] Step S10: Install two angle sensors and one position sensor on a hydraulic ship steering gear. Use the angle sensors to measure the input rotation angle command signal and the output rotation angle signal of the hydraulic steering gear respectively. Denote the input rotation angle command signal of the hydraulic steering gear as u1 and the output rotation angle signal of the steering gear as u2. Use the position sensor to measure the piston displacement signal of the valve-controlled cylinder, denoted as x a .

[0007] Step S20: Compare the input rotation angle command signal and the output rotation angle signal of the hydraulic steering gear to obtain the steering gear rotation angle error signal; then integrate the steering gear rotation angle error to obtain the integrated steering gear rotation angle error signal; then superimpose the piston displacement signal of the valve-controlled cylinder and the steering gear rotation angle error signal to form an integral sliding mode signal; and perform a finite-time switching transformation on the integral sliding mode signal to obtain a finite-time switching softening signal; then set the initial values of the total load identification adjustment signal and the load identification compensation feedback signal to zero, and then superimpose the finite-time switching softening signal and the integral sliding mode signal to form the total hydraulic steering gear load identification control signal.

[0008] Step S30: According to the input rotation angle command signal of the hydraulic steering gear and the empirical knowledge of three typical load conditions, set the characteristic time constants of the three typical load conditions, and establish first-order simplified approximate models for the three typical load conditions respectively. Then, after inputting the input rotation angle command signal of the hydraulic steering gear using the first-order simplified approximate model of the first typical load, obtain the first load output signal; then sequentially input the input rotation angle command signal of the hydraulic steering gear using the first-order simplified approximate models of the second and third typical loads respectively to obtain the second load output signal and the third load output signal.

[0009] Step S40: Compare the first load output signal with the output rotation angle signal of the steering gear to obtain the first load error signal; and perform integral transportation after taking the absolute value squared to obtain the first load matching metric signal; similarly, compare the second load output signal with the output rotation angle signal of the steering gear to obtain the second load error signal; and perform integral transportation after taking the absolute value squared to obtain the second load matching metric signal; compare the third load output signal with the output rotation angle signal of the steering gear to obtain the third load error signal; and perform integral transportation after taking the absolute value squared to obtain the third load matching metric signal.

[0010] Step S50: Select the minimum value from the first load matching metric signal, the second load matching metric signal, and the third load matching metric signal as the result of typical load condition identification. Then, design a load identification compensation feedback signal based on the characteristic time constant of the selected typical load condition and the servo angle error signal. Next, design a load identification constant parameter adjustment law signal based on the load error signal of the selected typical load condition, and integrate it to obtain a designed load identification constant parameter signal.

[0011] Step S60: Design a load identification sliding mode parameter adjustment law signal based on the load error signal of the selected typical load condition, and integrate it to obtain a designed load identification sliding mode parameter signal. Design a load identification damping parameter adjustment law signal based on the load error signal of the selected typical load condition, and integrate it to obtain a designed load identification damping parameter signal. Finally, add the load identification constant parameter signal to the product of the load identification sliding mode parameter signal and the integral sliding mode signal, and the product of the load identification damping parameter signal and the valve-controlled cylinder piston displacement signal to obtain a total load identification adjustment signal, thereby obtaining the subsequent calculation results of the total load identification adjustment signal and the load identification compensation feedback signal in Step S20, completing all calculations of the hydraulic servo load identification control total signal, and sending it to the operational amplifier circuit input port of the valve-controlled cylinder to control the piston movement of the valve-controlled cylinder, and completing the online identification and real-time online correction feedback control of the hydraulic servo load fluctuation.

[0012] In an exemplary embodiment of the present invention, compare the hydraulic servo input rotation angle command signal with the servo output rotation angle signal to obtain a servo angle error signal. Then, integrate the servo angle error to obtain a servo angle error integral signal. Then, add the valve-controlled cylinder piston displacement signal and the servo angle error signal to form an integral sliding mode signal. And perform a finite-time switching transformation on the integral sliding mode signal to obtain a finite-time switching softening signal. Then, set the initial values of the total load identification adjustment signal and the load identification compensation feedback signal to zero, and add the finite-time switching softening signal and the integral sliding mode signal to form the hydraulic servo load identification control total signal, including:

[0013] e = u1 - u2;

[0014] s1 = ∫edt;

[0015] s = k1e + k2s1 + k3x a ;

[0016]

[0017] u = k4s + k5w0 + z u +u d ;

[0018] where e is the steering gear angle error signal, s1 is the integral signal of the steering gear angle error, and s is the integral sliding mode signal; w0 is the finite-time switching softening signal; z u is the total load identification and adjustment signal, u d is the load identification compensation feedback signal, and u is the total load identification control signal of the hydraulic steering gear; k1, k2, k3, k4, and k5 are constant control parameters, and ε0 is a constant softening parameter.

[0019] In an exemplary embodiment of the present invention, according to the input steering angle command signal of the hydraulic steering gear and the empirical knowledge of three typical load conditions, the characteristic time constants of the three typical load conditions are set, and first-order simplified approximate models of the three typical load conditions are established respectively. After inputting the input steering angle command signal of the hydraulic steering gear, three load output signals are obtained, including:

[0020]

[0021] where p is the differential operator of the transfer function of the first-order simplified approximate model; y1 is the first load output signal; y2 is the second load output signal; y3 is the third load output signal; T1 is the characteristic time constant of the first typical load condition; T2 is the characteristic time constant of the second typical load condition; and T3 is the characteristic time constant of the third typical load condition.

[0022] In an exemplary embodiment of the present invention, according to the comparison of the three load output signals with the steering gear output angle signal, three load error signals are obtained; and after taking the absolute value square and integrating, three load matching measure signals are obtained, including:

[0023] e1 = y1 - u2;

[0024] s1 = ∫|e1| 2 dt;

[0025] e2 = y2 - u2;

[0026] s2 = ∫|e1| 2 dt;

[0027] e3 = y3 - u2;

[0028] s3 = ∫|e1| 2 dt;

[0029] where e1 is the first load error signal, s1 is the first load matching measure signal; e2 is the second load error signal, s2 is the second load matching measure signal; e3 is the third load error signal, and s3 is the third load matching measure signal.

[0030] In an exemplary embodiment of the present invention, a load identification compensation feedback signal is designed according to the characteristic time constant of the selected typical load condition and the servo actuator angle error signal; and a load identification constant parameter adjustment law signal is designed according to the load error signal of the selected typical load condition, and after integration, the designed load identification constant parameter signal includes:

[0031]

[0032] where i is equal to 1 or 2 or 3; the selection principle is to select i such that s i = min(s1, s2, s3), where the function of min() is to select the minimum value; T i is the characteristic time constant of the i-th typical load condition; T a is the constant time parameter of the transfer function of the load identification compensation link; u d is the load identification compensation feedback signal; k w1 is a constant parameter used to adjust the convergence speed of the load identification constant parameter signal, d w1 is the load identification constant parameter adjustment law signal; is the load identification constant parameter signal; w 10 is the initial value, selected as a constant.

[0033] In an exemplary embodiment of the present invention, a load identification sliding mode parameter adjustment law signal is designed according to the load error signal of the selected typical load condition, and after integration, the designed load identification sliding mode parameter signal is obtained; a load identification damping parameter adjustment law signal is designed according to the load error signal of the selected typical load condition, and after integration, the designed load identification damping parameter signal is obtained; finally, the load identification constant parameter signal is superimposed with the product of the load identification sliding mode parameter signal and the integral sliding mode signal and the product of the load identification damping parameter signal and the valve-controlled cylinder piston displacement signal to obtain the total load identification adjustment signal, including:

[0034]

[0035] where k w2 is a constant parameter used to adjust the convergence speed of the load identification sliding mode parameter signal, d w2 is the load identification sliding mode parameter adjustment law signal; is the load identification constant parameter signal; w 20 is the initial value, selected as a constant; k w3 is a constant parameter used to adjust the convergence speed of the load identification damping parameter signal, d w3 is the load identification damping parameter adjustment law signal; is the load identification damping parameter signal; w 30is the initial value, selected as a constant; z u is the total signal for load identification and adjustment.

[0036] Beneficial effects

[0037] The present invention provides a method for estimating and feedback controlling the load fluctuation of a hydraulic steering gear. The main innovative points are as follows: First, in the control scheme, by setting three typical load modes to approximate and estimate, the problem that traditional PID control cannot classify the load conditions of the steering gear typically and perform targeted and precise subdivision control is solved. Second, three typical load modes are characterized by a simple first-order system. Of course, it can also be extended to four, five, and other multiple modes. The characterization method is simple and convenient for using the prior knowledge and experience of engineering practice to extract the time constant; at the same time, it makes the more detailed multi-mode extension easier to implement. Third, the load state that is most suitable for the current time of the steering gear is simply selected by minimizing the square integral. Thus, although the real load condition is difficult to accurately measure and calculate, this measurement can simply and directly make the most reasonable estimate of the current load state. Fourth, after estimating and selecting the load state, a method using inverse design is proposed to obtain the load identification compensation feedback signal, which directly compensates the closed-loop control and improves the quality of the closed-loop control. Fifth, on the basis of sliding mode control, using the results of load identification and estimation, the total signal for load identification and adjustment is designed, thus realizing the organic integration of identification and control, the integration of closed-loop feedback and identification compensation feedback, and the integration of sliding mode control and adaptive control, and improving the quality of closed-loop steering gear control.

[0038] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present invention. Brief description of the drawings

[0039] The drawings herein are incorporated into the specification and form a part of this specification, showing embodiments consistent with the present invention, and are used together with the specification to explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0040] Figure 1 is the flow chart of a method for estimating and feedback controlling the load fluctuation of a hydraulic steering gear provided by the present invention.

[0041] Figure 2 is a schematic structural diagram of a hydraulic steering gear control system for the method provided by an embodiment of the present invention;

[0042] Figure 3 is the signal curve of the output rotation angle of the steering gear (unit: degree) for the method provided by an embodiment of the present invention;

[0043] Figure 4 is the valve-controlled cylinder piston displacement signal curve (unitless) of the method provided by the embodiment of the present invention;

[0044] Figure 5 is the rudder angle error signal curve (unit: degree) of the method provided by the embodiment of the present invention;

[0045] Figure 6 is the total signal curve of hydraulic rudder load identification control (unitless) of the method provided by the embodiment of the present invention;

[0046] Figure 7 is the integral signal curve of the angle error (unitless) of the method provided by the embodiment of the present invention;

[0047] Figure 8 is the first load matching metric signal curve (unitless) of the method provided by the embodiment of the present invention;

[0048] Figure 9 is the second load matching metric signal curve (unitless) of the method provided by the embodiment of the present invention;

[0049] Figure 10 is the third load matching metric signal curve (unitless) of the method provided by the embodiment of the present invention;

[0050] Figure 11 is the load identification compensation feedback signal curve (unitless) of the method provided by the embodiment of the present invention;

[0051] Figure 12 is the total signal curve of load identification adjustment (unitless) of the method provided by the embodiment of the present invention. Detailed implementation manners

[0052] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this invention will be more complete and comprehensive, and will fully convey the concept of the example embodiments to those skilled in the art. The features, structures, or characteristics described may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of the present invention. However, those skilled in the art will realize that the technical solutions of the present invention can be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. may be used. In other cases, well-known technical solutions are not shown or described in detail to avoid obscuring the various aspects of the present invention.

[0053] The present invention provides a method for estimating and feedback controlling the load fluctuation of a hydraulic steering gear. By setting the time constants of three typical load fluctuation cases and establishing a simplified approximate model, inputting the steering gear input command signal, comparing the difference between the model output signal and the steering gear output signal, obtaining three load error signals, then performing square integral operation, and selecting the smallest one as the load fluctuation case closest to the actual situation; then designing a load identification compensation feedback signal according to the time constant of this case, and at the same time designing a total load identification adjustment signal according to the load error signal of this case, and forming a total hydraulic steering gear load identification control signal with the integral sliding mode signal formed by the valve-controlled cylinder piston displacement signal and the steering gear angle error signal and the finite-time switching softening signal, thus realizing the estimation of the typical load fluctuation of the hydraulic steering gear, and at the same time using the load fluctuation estimation result to correct and compensate the sliding mode control, so as to further improve the dynamic performance of the steering gear.

[0054] Next, in conjunction with the accompanying drawings, a method for estimating and feedback controlling the load fluctuation of a hydraulic steering gear of the present invention will be further explained and described. Refer to Figure 1 As shown, the method for estimating and feedback controlling the load fluctuation of a hydraulic steering gear includes the following steps:

[0055] Step S10, install two angle sensors and a position sensor on a hydraulic marine steering gear. Use the angle sensors to measure the input steering angle command signal and the output steering gear angle signal respectively, and use the position sensor to measure the valve-controlled cylinder piston displacement signal.

[0056] Specifically, install an angle sensor on the hydraulic marine steering gear to measure the steering gear input steering angle command signal, denoted as u1; install an angle sensor to measure the steering gear output steering angle signal, denoted as u2; use a position sensor to measure the valve-controlled cylinder piston displacement signal, denoted as x a . The block diagram of the entire hydraulic steering gear load fluctuation estimation and feedback control scheme is as Figure 2 shown.

[0057] Step S20, compare the input steering angle command signal of the hydraulic steering gear with the steering gear output steering angle signal to obtain a steering gear angle error signal; then integrate the steering gear angle error signal to obtain a steering gear angle error integral signal; then superimpose the valve-controlled cylinder piston displacement signal and the steering gear angle error signal to form an integral sliding mode signal; and perform a finite-time switching transformation on the integral sliding mode signal to obtain a finite-time switching softening signal; then set the initial values of the total load identification adjustment signal and the load identification compensation feedback signal to zero, and then superimpose the finite-time switching softening signal and the integral sliding mode signal to form a total hydraulic steering gear load identification control signal.

[0058] Specifically, it can be decomposed into the following five small steps. The first step is to compare the input steering angle command signal of the hydraulic steering gear with the steering gear output steering angle signal to obtain the steering gear angle error signal as follows:

[0059] e = u1 - u2;

[0060] where e is the steering gear angle error signal.

[0061] In the second step, integrate the steering gear angle error signal to obtain the integrated steering gear angle error signal as follows:

[0062] s1 = ∫edt;

[0063] where s1 is the integrated steering gear angle error signal.

[0064] In the third step, use the integrated steering gear angle error signal to superimpose the valve-controlled cylinder piston displacement signal and the steering gear angle error signal to form the integral sliding mode signal as follows:

[0065] s = k1e + k2s1 + k3x a ;

[0066] where s is the integral sliding mode signal; k1, k2, and k3 are constant control parameters.

[0067] In the fourth step, perform a finite-time switching transformation on the integral sliding mode signal to obtain the finite-time switching softening signal as follows:

[0068]

[0069] where w0 is the finite-time switching softening signal; ε0 is a constant softening parameter.

[0070] In the fifth step, set the initial values of the total load identification adjustment signal and the load identification compensation feedback signal to zero, and then superimpose the finite-time switching softening signal and the integral sliding mode signal to form the total hydraulic steering gear load identification control signal as follows:

[0071] u = k4s + k5w0 + z u +u d ;

[0072] where z u is the total load identification adjustment signal, u d is the load identification compensation feedback signal, and u is the total hydraulic steering gear load identification control signal; k4 and k5 are constant control parameters.

[0073] Step S30: According to the input steering angle command signal of the hydraulic steering gear and the empirical knowledge of three typical load conditions, set the characteristic time constants of the three typical load conditions, respectively establish the first-order simplified approximate models of the three typical load conditions, and then use the first-order simplified approximate model of the first typical load to input the input steering angle command signal of the hydraulic steering gear to obtain the first load output signal; then, in turn, use the first-order simplified approximate models of the second and third typical loads to input the input steering angle command signal of the hydraulic steering gear respectively to obtain the second load output signal and the third load output signal as follows:<> <>

[0074] <> <> <>

[0075] where p is the differential operator of the transfer function of the first-order simplified approximate model; y1 is the first load output signal; y2 is the second load output signal; y3 is the third load output signal; T1 is the characteristic time constant of the first typical load condition; T2 is the characteristic time constant of the second typical load condition; T3 is the characteristic time constant of the third typical load condition.<> <>

[0076] Step S40: Compare the first load output signal with the steering gear output angle signal to obtain the first load error signal; and perform integral transportation after taking the absolute value squared to obtain the first load matching metric signal; similarly, compare the second load output signal with the steering gear output angle signal to obtain the second load error signal; and perform integral transportation after taking the absolute value squared to obtain the second load matching metric signal; compare the third load output signal with the steering gear output angle signal to obtain the third load error signal; and perform integral transportation after taking the absolute value squared to obtain the third load matching metric signal.<> <>

[0077] Specifically, it can be decomposed into the following three small steps. The first step: Compare the first load output signal with the steering gear output angle signal to obtain the first load error signal; and perform integral transportation after taking the absolute value squared to obtain the first load matching metric signal as follows:<> <>

[0078] e1 = y1 - u2;<> <>

[0079] s1 = ∫|e1|<> 2 dt;<> <>

[0080] where e1 is the first load error signal and s1 is the first load matching metric signal.<> <>

[0081] The second step: Compare the second load output signal with the steering gear output angle signal to obtain the second load error signal; and perform integral transportation after taking the absolute value squared to obtain the second load matching metric signal as follows:<> <>

[0082] e2 = y2 - u2;

[0083] s2 = ∫|e1| 2 dt;

[0084] Where e2 is the second load error signal and s2 is the second load matching metric signal.

[0085] In the third step, compare the third load output signal with the servo output rotation angle signal to obtain the third load error signal; and perform integral transportation after taking the absolute value square to obtain the third load matching metric signal as follows:

[0086] e3 = y3 - u2;

[0087] s3 = ∫|e1| 2 dt;

[0088] Where e3 is the third load error signal and s3 is the third load matching metric signal.

[0089] Step S50; According to the first load matching metric signal, the second load matching metric signal, and the third load matching metric signal, select the minimum value as the result of the typical load condition identification; then design the load identification compensation feedback signal according to the characteristic time constant of the selected typical load condition and the servo rotation angle error signal; and then design the load identification constant parameter adjustment law signal according to the load error signal of the selected typical load condition, and perform integration to obtain the designed load identification constant parameter signal.

[0090] Specifically, it can be decomposed into the following three small steps. In the first step, according to the first load matching metric signal, the second load matching metric signal, and the third load matching metric signal, select the minimum value as the result of the typical load condition identification; during the selection process, i is equal to 1 or 2 or 3; the selection principle is to select i such that s i = min(s1, s2, s3), where the function of the min() function is to select the minimum value.

[0091] In the second step, design the load identification compensation feedback signal according to the characteristic time constant of the selected typical load condition and the servo rotation angle error signal as follows:

[0092]

[0093] Where T i is the characteristic time constant of the i-th typical load condition; T a is the constant time parameter of the load identification compensation link transfer function.

[0094] Step 3: According to the load error signal of the selected typical load condition, design the load identification constant parameter adjustment law signal, and after integration, obtain the designed load identification constant parameter signal as follows:

[0095]

[0096] where u d is the load identification compensation feedback signal; k w1 is a constant parameter used to adjust the convergence speed of the load identification constant parameter signal, and d w1 is the load identification constant parameter adjustment law signal; is the load identification constant parameter signal; w 10 is the initial value, selected as a constant.

[0097] Step S60: According to the load error signal of the selected typical load condition, design the load identification sliding mode parameter adjustment law signal, and after integration, obtain the designed load identification sliding mode parameter signal; according to the load error signal of the selected typical load condition, design the load identification damping parameter adjustment law signal, and after integration, obtain the designed load identification damping parameter signal; finally, use the load identification constant parameter signal to superimpose the product of the load identification sliding mode parameter signal and the integral sliding mode signal and the product of the load identification damping parameter signal and the valve-controlled cylinder piston displacement signal to obtain the total load identification adjustment signal.

[0098] Specifically, it can be decomposed into the following three small steps. The first step: According to the load error signal of the selected typical load condition, design the load identification sliding mode parameter adjustment law signal, and after integration, obtain the designed load identification sliding mode parameter signal as follows:

[0099]

[0100] where k w2 is a constant parameter used to adjust the convergence speed of the load identification sliding mode parameter signal, and d w2 is the load identification sliding mode parameter adjustment law signal; is the load identification constant parameter signal; w 20 is the initial value, selected as a constant.

[0101] The second step: According to the load error signal of the selected typical load condition, design the load identification damping parameter adjustment law signal, and after integration, obtain the designed load identification damping parameter signal as follows:

[0102]

[0103] where k w3 is a constant parameter used to adjust the convergence speed of the load identification damping parameter signal, and dw3 is the signal for regulating the damping parameter identification law of the load; is the signal of the damping parameter for load identification; w 30 is the initial value, which is selected as a constant value.

[0104] In the third step, the total load identification adjustment signal is obtained by superimposing the constant parameter signal of load identification, the product of the sliding mode parameter signal of load identification and the integral sliding mode signal, and the product of the damping parameter signal of load identification and the piston displacement signal of the valve-controlled cylinder, as follows:

[0105]

[0106] where z u is the total load identification adjustment signal, so as to obtain the subsequent calculation results of the total load identification adjustment signal and the load identification compensation feedback signal in step S20, complete all calculations of the total load identification control signal of the hydraulic steering gear, and transmit it to the input port of the operational amplifier circuit of the valve-controlled cylinder to control the piston movement of the valve-controlled cylinder, thereby completing the online identification of the load fluctuation of the hydraulic steering gear and the real-time online correction feedback control.

[0107] Case implementation and analysis of computer calculation results

[0108] In step S10, the servo input command signal is set to 15 degrees respectively, and the servo output rotation angle signal is measured by an angle sensor as Figure 3 shown; the piston displacement signal of the valve-controlled cylinder is measured by a position sensor as Figure 4 shown.

[0109] In step S20, ε0 = 0.12, k1 = 1.2, k2 = 0.6, k3 = 1.5, k4 = 3600, k5 = 2500 are selected, and the servo rotation angle error signal is obtained as Figure 5 shown, and the total load identification control signal of the hydraulic servo is obtained as Figure 6 shown; the integral signal of the rotation angle error is as Figure 7 shown.

[0110] In step S30, T1 = 0.15, T1 = 1.5, T1 = 5.5 are selected.

[0111] In step S40, the first load matching metric signal is obtained as Figure 8 shown, and the second load matching metric signal is as Figure 9 shown; the third load matching metric signal is obtained as Figure 10 shown.

[0112] In step S50, T a = 0.1, k w1 = 0.02, w 10 = 0; the load identification compensation feedback signal is obtained asFigure 11 as shown

[0113] In step S60, k is selected w2 = 0.005, w 20 = 0; k w3 = 0.07, w 30 = 0, and the total load identification and adjustment signal is obtained as Figure 12 shown

[0114] First, it can be seen from Figure 3 that the final overall scheme is stable and finally stabilizes at 15 degrees; and it can be seen from Figure 5 that the error is convergent and the control accuracy is high; indicating that the overall scheme is basically feasible; although there are some oscillations before, this is exactly caused by the identification and estimation of load fluctuations and is normal; and it can be seen from Figure 8 and Figure 9 as well as Figure 10 that the identification resolution is very high at this time, Figure 8 the coincidence degree of the first type of load characterized is the highest, so its error integral is the smallest; and it is significantly smaller than the other two overloads; also indicating that the method provided by the present invention is very feasible for the hydraulic steering gear system. Therefore, the experimental results fully demonstrate the effectiveness of the method provided by the present invention and have high engineering application value.

Claims

1. A method for estimating and feedback controlling load fluctuations of a hydraulic steering gear, characterized in that, It includes the following steps: Step S10, install two angle sensors and a position sensor on a hydraulic ship steering gear. Use the angle sensors to measure the input rotation angle command signal and the output rotation angle signal of the hydraulic steering gear respectively. The input rotation angle command signal of the hydraulic steering gear is denoted as u1, and the output rotation angle signal of the steering gear is denoted as u2. Use the position sensor to measure the piston displacement signal of the valve-controlled cylinder, denoted as x a ; Step S20: Compare the input steering angle command signal of the hydraulic steering gear with the steering gear output steering angle signal to obtain the steering gear angle error signal; then integrate the steering gear angle error to obtain the steering gear angle error integration signal; then superimpose the valve-controlled cylinder piston displacement signal and the steering gear angle error signal to form an integral sliding mode signal; and perform a finite-time switching transformation on the integral sliding mode signal to obtain a finite-time switching softening signal; then set the initial values of the load identification adjustment total signal and the load identification compensation feedback signal to zero, and then superimpose the finite-time switching softening signal and the integral sliding mode signal to form the hydraulic steering gear load identification control total signal; Step S30: According to the input steering angle command signal of the hydraulic steering gear and the empirical knowledge of three typical load conditions, set the characteristic time constants of the three typical load conditions, and respectively establish first-order simplified approximate models of the three typical load conditions. Then, after inputting the input steering angle command signal of the hydraulic steering gear using the first-order simplified approximate model of the first typical load, obtain the first load output signal; then successively input the input steering angle command signal of the hydraulic steering gear using the first-order simplified approximate models of the second and third typical loads to obtain the second load output signal and the third load output signal; Compare the first load output signal with the steering gear output steering angle signal to obtain the first load error signal; and perform integral transportation after taking the absolute value square to obtain the first load matching metric signal; similarly, compare the second load output signal with the steering gear output steering angle signal to obtain the second load error signal; And perform integral transportation after taking the absolute value square to obtain the second load matching metric signal; compare the third load output signal with the steering gear output steering angle signal to obtain the third load error signal; and perform integral transportation after taking the absolute value square to obtain the third load matching metric signal; Step S50: According to the first load matching metric signal, the second load matching metric signal, and the third load matching metric signal, select the minimum value as the result of the typical load condition identification; then design the load identification compensation feedback signal according to the characteristic time constant of the selected typical load condition and the steering gear angle error signal; and then design the load identification constant parameter adjustment law signal according to the load error signal of the selected typical load condition, and perform integration to obtain the designed load identification constant parameter signal; Step S60: Design the load identification sliding mode parameter adjustment law signal according to the load error signal of the selected typical load condition, and perform integration to obtain the designed load identification sliding mode parameter signal; Based on the load error signal of the selected typical load condition, design the load identification damping parameter adjustment law signal, and after integration, obtain the designed load identification damping parameter signal; finally, use the load identification constant parameter signal to superimpose the product of the load identification sliding mode parameter signal and the integral sliding mode signal, as well as the product of the load identification damping parameter signal and the valve-controlled cylinder piston displacement signal, to obtain the total load identification adjustment signal, so as to obtain the subsequent calculation results of the total load identification adjustment signal and the load identification compensation feedback signal in step S20, complete all calculations of the hydraulic servo load identification control total signal, and transmit it to the operational amplifier circuit input port of the valve-controlled cylinder to control the piston movement of the valve-controlled cylinder, thereby completing the online identification and real-time online correction feedback control of the hydraulic servo load fluctuation.

2. The hydraulic steering gear load fluctuation estimation and feedback control method according to claim 1, characterized in that Compare the input rotation angle command signal of the hydraulic servo with the servo output rotation angle signal to obtain the servo rotation angle error signal; then integrate the servo rotation angle error to obtain the servo rotation angle error integration signal; then superimpose the valve-controlled cylinder piston displacement signal and the servo rotation angle error signal to form an integral sliding mode signal; and perform a finite-time switching transformation on the integral sliding mode signal to obtain a finite-time switching softening signal; then set the initial values of the total load identification adjustment signal and the load identification compensation feedback signal to zero, and then superimpose the finite-time switching softening signal and the integral sliding mode signal to form the hydraulic servo load identification control total signal, including: e = u1 - u2; s1 = ∫edt; s = k1e + k2s1 + k3x a ; u = k4s + k5w0 + z u + u d ; where e is the servo angle error signal, s1 is the integral signal of the servo angle error, and s is the integral sliding mode signal; w0 is the finite-time switching softening signal; z u is the total load identification and adjustment signal, u d is the load identification compensation feedback signal, and u is the total load identification control signal of the hydraulic servo; k1, k2, k3, k4, k5 are constant control parameters, and ε0 is a constant softening parameter.

3. The hydraulic steering gear load fluctuation estimation and feedback control method according to claim 2, wherein Based on the input rotation angle command signal of the hydraulic servo and the empirical knowledge of three typical load conditions, set the characteristic time constants of the three typical load conditions, and respectively establish first-order simplified approximate models of the three typical load conditions. Then, after inputting the input rotation angle command signal of the hydraulic servo into the first-order simplified approximate model of the first typical load, obtain the first load output signal; then, in turn, input the input rotation angle command signal of the hydraulic servo into the first-order simplified approximate models of the second and third typical loads respectively to obtain the second load output signal and the third load output signal as follows: Where p is the differential operator of the transfer function of the first-order simplified approximate model; y1 is the first load output signal; y2 is the second load output signal; y3 is the third load output signal; T1 is the characteristic time constant of the first typical load condition; T2 is the characteristic time constant of the second typical load condition; T3 is the characteristic time constant of the third typical load condition.

4. A method for estimating and feedback controlling the load fluctuation of a hydraulic steering gear according to claim 3, characterized in that, Compare the first load output signal with the servo output rotation angle signal to obtain the first load error signal; and perform integral transportation after taking the absolute value square to obtain the first load matching measure signal; similarly, compare the second load output signal with the servo output rotation angle signal to obtain the second load error signal; Integrate after taking the absolute value squared for transportation to obtain the second load matching metric signal; compare the third load output signal with the servo output rotation angle signal to obtain the third load error signal; integrate after taking the absolute value squared for transportation to obtain the third load matching metric signal, and select the minimum value from the first load matching metric signal, the second load matching metric signal, and the third load matching metric signal as the result of typical load condition identification; then design a load identification compensation feedback signal based on the characteristic time constant of the selected typical load condition and the servo rotation angle error signal; further design a load identification constant parameter adjustment rule signal based on the load error signal of the selected typical load condition, and integrate it to obtain the designed load identification constant parameter signal as follows: e1 = y1 - u2; s1 = ∫|e1| 2 dt; e2 = y2 - u2; s2 = ∫|e1| 2 dt; e3 = y3 - u2; s3 = ∫|e1| 2 dt; Where e1 is the first load error signal, s1 is the first load matching metric signal; e2 is the second load error signal, s2 is the second load matching metric signal; e3 is the third load error signal, s3 is the third load matching metric signal; i is equal to 1 or 2 or 3; The selection principle is to select i such that s i = min(s1, s2, s3), where the function of min() is to select the minimum value; T i is the characteristic time constant for the i-th typical load condition; T a is the constant time parameter of the transfer function of the load identification compensation link; u d is the load identification compensation feedback signal; k w1 is a constant parameter used to adjust the convergence speed of the load identification constant parameter signal, d w1 is the load identification constant parameter adjustment law signal; is the load identification constant parameter signal; w 10 is the initial value, selected as a constant.

5. A method for estimating and feedback controlling the load fluctuation of a hydraulic steering gear according to claim 4, characterized in that, Design a load identification sliding mode parameter adjustment rule signal based on the load error signal of the selected typical load condition, and integrate it to obtain the designed load identification sliding mode parameter signal; Design a load identification damping parameter adjustment rule signal based on the load error signal of the selected typical load condition, and integrate it to obtain the designed load identification damping parameter signal; finally, add the load identification constant parameter signal to the product of the load identification sliding mode parameter signal and the integral sliding mode signal, and the product of the load identification damping parameter signal and the valve-controlled cylinder piston displacement signal to obtain the total load identification adjustment signal, thereby obtaining the subsequent calculation results of the total load identification adjustment signal and the load identification compensation feedback signal in step S20, completing all calculations of the hydraulic servo load identification control total signal, and sending it to the input port of the operational amplifier circuit of the valve-controlled cylinder to control the piston movement of the valve-controlled cylinder, and completing the online identification and real-time online correction feedback control of the hydraulic servo load fluctuation as follows: where k w2 is a constant parameter used to adjust the convergence speed of the load identification sliding mode parameter signal, and d w2 is the load identification sliding mode parameter adjustment law signal; is the load identification constant parameter signal; w 20 is the initial value, selected as a constant; k w3 is a constant parameter used to adjust the convergence speed of the load identification damping parameter signal, and d w3 is the load identification damping parameter adjustment law signal; is the load identification damping parameter signal; w 30 is the initial value, selected as a constant value; z u is the total signal for load identification adjustment.

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