CN113625547B - Main valve position control method of controller - Google Patents
Main valve position control method of controller Download PDFInfo
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- CN113625547B CN113625547B CN202110916482.5A CN202110916482A CN113625547B CN 113625547 B CN113625547 B CN 113625547B CN 202110916482 A CN202110916482 A CN 202110916482A CN 113625547 B CN113625547 B CN 113625547B
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- G05B11/36—Automatic controllers electric with provision for obtaining particular characteristics, e.g. proportional, integral, differential
- G05B11/42—Automatic controllers electric with provision for obtaining particular characteristics, e.g. proportional, integral, differential for obtaining a characteristic which is both proportional and time-dependent, e.g. P.I., P.I.D.
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Abstract
The invention discloses a main valve position control method of a controller, which relates to the field of controllers and comprises the steps of constructing a step response model vector of a proportional valve and constructing a step dynamic matrix according to the step response model vector; acquiring the position deviation between the actual position of the main valve at the current moment and a preset position through a first comparator; obtaining an output value of the MPC controller at the current moment by using the position deviation at the current moment and the step dynamic matrix through the MPC controller; acquiring the valve back pressure deviation of the proportional valve at the current moment by using a second comparator through the output value of the MPC controller at the current moment and the valve back pressure of the proportional valve at the current moment; acquiring an output value of a PID controller at the current moment by using the PID controller through the valve back pressure deviation of the proportional valve at the current moment; the position of the main valve is regulated by the proportional valve according to the output value of the PID controller at the current moment, so that the problems of large disturbance and system oscillation in the position control process are solved, and the accuracy and stability of the position control are greatly improved.
Description
Technical Field
The invention relates to the field of controllers, in particular to a main valve position control method of a controller.
Background
The multi-way valve is a short for multi-way reversing valve, has the advantages of compact structure, simple pipeline connection, capability of realizing independent control of loads of multiple execution mechanisms and the like as a main control element of engineering machinery, and is widely applied to hydraulic systems of engineering machinery. The multi-way valve directly relates to whether the whole engineering vehicle can run efficiently and safely. With the development of society and economy, the demands of industrial control systems for the accuracy and rapidity of valve position control are increasing. At present, most valve position control systems in China still adopt a traditional PID control algorithm, and the PID control algorithm has the characteristics of simple principle and easy realization, and has excellent control effect on the production process of a controlled object with a definite mathematical model. The working environment of the multi-way valve is different and is influenced by viscosity of medium flow flowing through the valve, internal friction force, unbalance force and the like of the valve, the valve position control process has strong nonlinearity, large inertia and time variability, an accurate mathematical model cannot be built, the parameter setting of the traditional PID algorithm is extremely difficult, an ideal control effect is often difficult to achieve, and safety problems and huge economic losses are brought to the industrial production process.
In addition, the research and application of the valve position control system at home and abroad at present mainly aims at a single-loop control system, the single-loop control system is simple in structure and easy to operate, but the anti-interference performance of the single-loop control system is poor, and the valve position control process is often caused to swing due to the interference of a plurality of external factors in the industrial production process of the regulating valve, so that a series of safety problems are caused. Therefore, it is difficult to ensure that the industrial process is performed smoothly and safely using single loop control in the valve position control system.
In summary, at present, the valve position control technology mainly has the following technical problems: because the valve position control process has strong nonlinearity, large inertia and time variability, an accurate mathematical model cannot be established, the control parameter setting of the conventional PID control algorithm is extremely difficult, and effective control is difficult to realize; secondly, the single-loop control system has poor anti-interference performance, is easy to cause oscillation of a position control process, is difficult to maintain safe operation of industrial production, and has the problems of limited anti-interference performance, simple control algorithm and common control effect.
Disclosure of Invention
In order to solve the problems that the control parameter setting of a conventional PID control algorithm in the prior art is extremely difficult and effective control is difficult to realize, the anti-interference performance of a single-loop control system is poor, the oscillation of a position control process is easy to cause, and the anti-interference performance of a valve position cascade control system which is proposed at present is limited, the invention provides a main valve position control method of a controller, wherein the controller comprises a first comparator, an MPC controller, a second comparator, a PID controller, a proportional valve and a main valve; the first comparator is electrically connected with the MPC controller, the MPC is electrically connected with the second comparator, the second comparator is electrically connected with the PID controller, the PID controller is electrically connected with the proportional valve, and the proportional valve is hydraulically connected with the main valve; the control method comprises the following steps:
s01: acquiring a step response sampling value output by the proportional valve at the current moment, constructing a step response model vector of the proportional valve through the step response sampling value, and constructing a step dynamic matrix according to the step response model vector;
s02: acquiring the actual position of the main valve at the current moment, and acquiring the position deviation between the actual position of the main valve at the current moment and the preset position through a first comparator;
s03: obtaining an output value of the MPC controller at the current moment by using the position deviation at the current moment and the step dynamic matrix through the MPC controller;
s04: acquiring the valve back pressure of the proportional valve at the current moment, and acquiring the valve back pressure deviation of the proportional valve at the current moment by using a second comparator through the output value of the MPC controller at the current moment and the valve back pressure of the proportional valve at the current moment;
s05: acquiring an output value of a PID controller at the current moment by using the PID controller through the valve back pressure deviation of the proportional valve at the current moment;
s06: and adjusting the position of the main valve by using a proportional valve according to the output value of the PID controller at the current moment.
Further, the proportional valve comprises a first proportional valve and a second proportional valve; the specific steps for constructing the step dynamic matrix in the step S01 are as follows:
s11: acquiring a step response sampling value output by the first proportional valve and the second proportional valve according to the step response sampling;
s12: respectively obtaining corresponding step response model vectors according to step response sampling values of the first proportional valve and the second proportional valve;
s13: and constructing a step dynamic matrix according to the step response model vectors of the first proportional valve and the second proportional valve.
Further, the specific method of step S04 includes the steps of:
s41: acquiring valve back pressure of the first proportional valve and the second proportional valve at the current moment;
s42: acquiring the valve back pressure deviation of the first proportional valve at the current moment by using a second comparator through the output value of the MPC controller at the current moment and the valve back pressure of the first proportional valve at the current moment; and obtaining the valve post pressure deviation of the second proportional valve at the current moment by using a second comparator through the output value of the MPC controller at the current moment and the valve post pressure of the second proportional valve at the current moment.
Further, the specific method for obtaining the output value of the PID controller at the current time in the step S05 is as follows:
acquiring a PID controller output value corresponding to the first proportional valve at the current moment by using a PID controller through the valve back pressure deviation of the first proportional valve at the current moment;
and acquiring the output value of the PID controller corresponding to the second proportional valve at the current moment by using the PID controller through the valve back pressure deviation of the second proportional valve at the current moment.
Further, the specific method for adjusting the position of the main valve in the step S06 is as follows:
and adjusting the back valve pressure of the first proportional valve and the second proportional valve through the output value of the PID controller corresponding to the first proportional valve and the second proportional valve at the current moment so as to adjust the position of the main valve.
Further, the specific method for obtaining the output value of the MPC controller at the current time in the step S03 is as follows:
s31: obtaining the predicted output value of the MPC controller at each moment after the current moment through a prediction model of the MPC controller;
s32: obtaining control increment of the output value of the MPC controller at the current moment by utilizing a rolling optimization method of the MPC controller according to the predicted output value of the MPC controller at each moment after the current moment and the step dynamic matrix;
s33: acquiring an output correction value of the MPC controller at the next moment by using a feedback correction method of the MPC controller through a control increment of the output value of the MPC controller at the current moment;
s34: and obtaining the output value of the MPC controller at the current moment according to the output correction value of the MPC controller at the next moment.
Further, the formula for obtaining the control increment of the output value of the MPC controller at the current time in step S32 is as follows:
wherein K is the current time, M is the control time domain, p is the optimized time domain of rolling optimization, A is the step dynamic matrix, Q is the preset error weight matrix, R is the preset control weight matrix, w is the output expected value of the MPC controller, and w p (k) To optimize the output expectancy of the MPC controller at the instant in time in the time domain,for the predicted output value of the current time obtained by optimizing the predicted output value of the MPC controller at each time in the time domain, deltau M (k) And (5) outputting a control increment of the value for the MPC controller at the current moment.
Further, the formula for obtaining the output correction value of the MPC controller at the next time in step S33 is as follows:
wherein S is a preset displacement matrix,for the predicted correction value of the MPC controller at the next moment obtained by the control increment of the output value of the MPC controller at the current moment,/and/or>The correction value is output for the MPC controller at the next time.
Further, in the step S05, the formula for obtaining the output value of the PID controller corresponding to the first proportional valve at the current time is:
wherein K is p E is a preset proportionality coefficient 1 (k) For the valve pressure deviation, e, of the first proportional valve at the present moment 1 (k-1) represents the valve post-valve pressure deviation of the first proportional valve at the previous time, i is a constant whose initial value is equal to 0, T is the period of step response sampling, T i E is a preset integral constant 1 (i) For the pressure deviation after the valve of the first proportional valve at the ith moment, T d To preset differential constant, u 1 (k-1) is the output value of the PID controller corresponding to the first proportional valve at the previous moment, u 1 (k) Outputting a value for the PID controller corresponding to the first proportional valve at the current moment;
the formula expression for obtaining the output value of the PID controller corresponding to the second proportional valve at the current moment is as follows:
in the formula e 2 (k) E, for the valve pressure deviation of the second proportional valve at the current moment 2 (k-1) represents the pressure deviation after the valve of the second proportional valve at the previous time, e 2 (i) For the pressure deviation after the valve of the second proportional valve at the ith moment, u 2 (k-1) is the output value of the PID controller corresponding to the second proportional valve at the previous moment, u 2 (k) And outputting a value for the PID controller corresponding to the second proportional valve at the current moment.
Further, the controller also comprises a displacement sensor, a first pressure sensor and a second pressure sensor;
the displacement sensor is electrically connected with the main valve and is used for acquiring the actual position of the main valve in real time;
the first pressure sensor is electrically connected with the first proportional valve and is used for acquiring the valve back pressure of the first proportional valve; the second pressure sensor is electrically connected with the second proportional valve and is used for acquiring the valve back pressure of the second proportional valve.
Compared with the prior art, the invention at least has the following beneficial effects:
(1) The invention adopts PID-MPC composite control, wherein the PID-MPC composite control comprises inner loop control and outer loop control, the inner loop control adopts PID control to restrain the influence effect of external interference on the system in the actual industrial control environment, the outer loop control adopts multivariable dynamic matrix control (MPC) to ensure that the system obtains optimal control and distribution effect, and the method can effectively improve the performance of the predictive control system;
(2) The invention is a cascade control method taking the position of a main valve as a control target, a position cascade control system related to the method actually forms two loops, one is a main valve position control loop, the other is a proportional valve control loop, the main valve position control loop is a main loop, and the main valve position is taken as a main loop control object; the proportional valve control loop is an auxiliary loop, and the proportional valve is used as an auxiliary loop control object; in the position control process, the proportional valve control loop serving as the auxiliary ring can rapidly overcome main disturbance which causes severe, frequent and large system change in the controlled process, so that the influence of secondary disturbance on the main ring control loop is very little, and then the main valve position control loop serving as the main ring further eliminates the disturbance which is not completely overcome by the auxiliary ring, so that the position change amplitude of the whole control process is small and stable, and the response speed, the control precision and the stability of the system are greatly improved;
(3) The position of the main valve is regulated by combining the PID controller and the MPC controller, so that the control system has strong predictive control and self-adaptive capacity, the problems of large disturbance and system oscillation in the position control process are solved, and the control precision and the robustness are greatly improved.
Drawings
FIG. 1 is a method step diagram of a method for controlling the position of a main valve of a controller;
FIG. 2 is a diagram of a controller configuration of a method for controlling a position of a main valve of the controller;
FIG. 3 is a rolling optimization diagram of a method of controlling a main valve position of a controller.
Detailed Description
The following are specific embodiments of the present invention and the technical solutions of the present invention will be further described with reference to the accompanying drawings, but the present invention is not limited to these embodiments.
Example 1
In order to improve the predictive control and self-adaptation capability of a main valve position control method, the invention provides a main valve position control method of a controller, wherein the controller comprises a first comparator, an MPC controller, a second comparator, a PID controller, a proportional valve and a main valve; the first comparator is electrically connected with the MPC controller, the MPC is electrically connected with the second comparator, the second comparator is electrically connected with the PID controller, the PID controller is electrically connected with the proportional valve, and the proportional valve is hydraulically connected with the main valve; the control method comprises the following steps:
s01: acquiring a step response sampling value output by the proportional valve at the current moment, constructing a step response model vector of the proportional valve through the step response sampling value, and constructing a step dynamic matrix according to the step response model vector;
the proportional valve comprises a first proportional valve and a second proportional valve; the specific steps for constructing the step dynamic matrix in the step S01 are as follows:
s11: acquiring a step response sampling value output by the first proportional valve and the second proportional valve according to the step response sampling;
s12: respectively obtaining corresponding step response model vectors according to step response sampling values of the first proportional valve and the second proportional valve;
s13: and constructing a step dynamic matrix according to the step response model vectors of the first proportional valve and the second proportional valve.
It should be noted that, in this embodiment, the PID controller includes a first PID controller and a second PID controller, where the first PID controller is electrically connected to the first proportional valve, and the second PID controller is electrically connected to the second proportional valve.
S02: acquiring the actual position of the main valve at the current moment, and acquiring the position deviation between the actual position of the main valve at the current moment and the preset position through a first comparator;
the preset position in this embodiment is denoted by ydn.
S03: obtaining an output value of the MPC controller at the current moment by using the position deviation at the current moment and the step dynamic matrix through the MPC controller;
the specific method for obtaining the output value of the MPC controller at the current moment in the step S03 is as follows:
s31: obtaining the predicted output value of the MPC controller at each moment after the current moment through a prediction model of the MPC controller;
in this embodiment, the specific details of obtaining, in step S31, the predicted output values of the MPC controller at each time after the current time through the prediction model are as follows:
at time k (i.e., the current time), assuming that the control effort remains unchanged, the predicted output values of the MPC controller outputs at N times after the current time may be expressed asi=1.. N; (e.g. at steady state startWherein y (k) is the actual output value of the MPC controller at the current moment;
when the k moment is controlled by a preset control increment delta u (k), the predicted output values of the MPC controllers at N moments after the k moment under the control action of the MPC controllers can be predicted as follows:
wherein a is a step response sampling value of the proportional valve output, a i For the step response sample value output by the proportional valve at the ith moment,the method comprises the steps of obtaining a preset predicted initial output value;
likewise, under the action of M consecutive preset control increments Δu (k),.+ -. Δu (k+m-1), the predicted output values of the MPC controller output at N times after the predicted k time may be represented by a prediction model as:
where M represents the number of control increments, (k+i|k) represents the prediction of the k+i time at the k time, j is a constant whose initial value is equal to 1,the predicted output value of the MPC controller at each time after the k time.
S32: obtaining control increment of the output value of the MPC controller at the current moment by utilizing a rolling optimization method of the MPC controller according to the predicted output value of the MPC controller at each moment after the current moment and the step dynamic matrix;
the formula expression for obtaining the control increment of the output value of the MPC controller at the current moment in the step S32 is as follows:
wherein K is the current time, M is the control time domain, p is the optimized time domain of rolling optimization, A is the step dynamic matrix, Q is the preset error weight matrix, R is the preset control weight matrix, w is the output expected value of the MPC controller, and w p (k) To optimize the output expectancy of the MPC controller at the instant in time in the time domain,for the predicted output value of the current time obtained by optimizing the predicted output value of the MPC controller at each time in the time domain, deltau M (k) And (5) outputting a control increment of the value for the MPC controller at the current moment.
In this embodiment, the specific details of obtaining the control increment of the output value of the MPC controller at the current moment by using the rolling optimization method of the MPC controller in step S31 are as follows:
firstly, it should be noted that the main purpose of the rolling optimization method is to optimize the preset control increment in the prediction model by using the prediction output value output by the MPC controller obtained in the prediction model, and correct the prediction output value output by the MPC controller by using the feedback correction method by using the optimized preset control increment, so that the prediction output value is as close to the preset prediction output expected value as possible, thereby reducing disturbance and vibration in the position control process;
as shown in fig. 3, MPC is an algorithm to optimize a certain control strategy, where T represents the sampling period of the step response, T represents time,the predicted output value of the MPC controller output at the 2 nd time after the k time is represented, and w (k+2) represents the predicted output expected value corresponding to the predicted output value of the MPC controller output at the 2 nd time after the k time; deltau (k) represents a preset control increment at the moment k, and u (k) represents an actual output value of the MPC controller; at time k, M control increments Δu (k),.+ -. Δu (k+m-1) corresponding to N times from that time are to be determined, and the predicted output values +.>As close as possible to a preset predicted output expected value w (k+i), i=1. M, P is herein referred to as the control time domain and the optimization time domain, respectively, and is typically defined as M.ltoreq.P.ltoreq.N;
in the control process, there is a problem that the preset control increment deltau is too severely changed, and this problem can be solved by adding soft constraint to the optimization performance index to perform rolling optimization on the preset control increment, so the optimization performance index at time k can be taken as:
wherein r and q are preset weight coefficients, which respectively represent the inhibition of tracking error and control quantity change, w is a preset reference target, and minJ (k) is an optimized performance index at k moment;
the above problem is expressed as Deltau, regardless of constraints M (k)＝[△u(k)...△u(k+M-1)] T An optimization problem of minimizing a performance index (formula 3) under a predictive model (formula 2) for optimizing variables; to solve this optimization problem, a relationship between the predictive model (equation 2) and the optimization performance index can be derived first, and this relationship can be written in vector form as:
wherein:
wherein A is a sampling value a of step response i A composed p×m matrix, called a dynamic matrix;predicted output values for the MPC controller predicted for P future times at time k; />Predicting initial output values preset for P times in the future for the k times;
the performance index (formula 3) is obtained by arranging the performance index into a vector form:
wherein w is P (k)＝[w(k+1)…w(k+P)] T ；Q＝diag(q 1 …q p )；R＝diag(r 1 …r M )；
Wherein Q is a diagonal matrix formed by preset weight coefficients Q, which is called an error weight matrix; r is a diagonal matrix formed by preset weight coefficients R, called an error weight matrix, w P (k) To at time kPredicting and outputting expected values preset at P moments in the future;
at time k, w P (k)，Are all of known quantity, J (k) is made to take the minimum Deltau M (k) Can pass the extreme value requirementThe control increment of the output value of the MPC controller at the current moment (namely, the control increment obtained after the preset control increment in the prediction model is subjected to rolling optimization) is obtained as follows:
in this embodiment, after performing rolling optimization on the preset control increment in the prediction model, the method further includes obtaining an actual output value of the MPC controller by using the optimized control increment, which is described in detail as follows:
equation 6 gives the optimum value of Δu (k.) the MPC does not treat them as solutions to be implemented, but rather takes the immediate control increment Δu (k) therein to construct the actual output value of the MPC controller, which is expressed as: u (k) =u (k-1) +Δu (k); by cycling through the above method to determine Δu (k+1) at the next time; the actual output value of the MPC controller at time instant 6,k can be expressed as:
in the P-dimensional row vector d T Called control vector, the expression is:
d T ＝c T (A T QA+R) -1 A T Q[d 1 …d P ](formula 8);
m-dimensional row vector c T = (10 … 0) representing an operation of taking the first element; once the optimization strategy is determined (i.e., P, M, Q, R is established), d T Can be offline at one timeAnd (5) calculating.
S33: acquiring an output correction value of the MPC controller at the next moment by using a feedback correction method of the MPC controller through a control increment of the output value of the MPC controller at the current moment;
the formula for obtaining the output correction value of the MPC controller at the next moment in the step S33 is as follows:
wherein S is a preset displacement matrix,for the predicted correction value of the MPC controller at the next moment obtained by the control increment of the output value of the MPC controller at the current moment,/and/or>The correction value is output for the MPC controller at the next time.
In this embodiment, a control increment of an output value of an MPC controller at a current time (i.e., a control increment obtained after performing rolling optimization on a preset control increment in a prediction model) is obtained by using a rolling optimization method of the MPC controller, and after an actual output value of an MPC controller at a k time is obtained by using the optimized control increment, the process proceeds to step S33, and a specific detailed description of obtaining an output correction value of the MPC controller at a next time by using a feedback correction method of the MPC controller in step S33 is as follows:
when u (k) is actually added to the object at time k, this corresponds to adding a control increment of magnitude Δu (k) to the input of the object, which can be expressed as:
in the method, in the process of the invention,prediction initiation preset for k times for N times in the futureOutput value->For the predicted output value of the MPC controller predicted for k times for N times in the future, equation 9 is actually a vector form of equation 1. However, the predicted value given by equation 9 may deviate from the actual value due to unknown factors such as the actual existence of model mismatch, environmental interference, and the like. For this purpose, in MPC, the actual output y (k+1) of the object is first detected by the next sampling time and is then compared with the predicted output value calculated by equation 9In comparison, an output error is constructed, the error expression being:
wherein e (k+1) is an output error value;
the prediction of the predicted output value of the future MPC controller may be modified by weighting e (k+1):
in the method, in the process of the invention,a prediction correction value for the MPC controller at the next moment; h is an N-dimensional vector of weight coefficients, called a correction vector, and may be expressed as h= [ h ] 1 …h N ] T ；
At time k +1, the predicted future point in time will also move to k +2, …, k +1+ n due to the variation in the time base point, and therefore,the element of (2) can be changed into the output correction value of the MPC controller at the moment k+1 through shifting, and the shifting expression is as follows:
whileDue to the truncation of the model, it can be made of +.>Approximately, this setting of the output correction value can be expressed in vector form as:
where S is a displacement matrix, which can be expressed as:
the correction value is output for the MPC controller at the next time.
S34: and obtaining the output value of the MPC controller at the current moment according to the output correction value of the MPC controller at the next moment.
S04: acquiring the valve back pressure of the proportional valve at the current moment, and acquiring the valve back pressure deviation of the proportional valve at the current moment by using a second comparator through the output value of the MPC controller at the current moment and the valve back pressure of the proportional valve at the current moment;
the specific method of the step S04 includes the steps of:
s41: acquiring valve back pressure of the first proportional valve and the second proportional valve at the current moment;
s42: acquiring the valve back pressure deviation of the first proportional valve at the current moment by using a second comparator through the output value of the MPC controller at the current moment and the valve back pressure of the first proportional valve at the current moment; and obtaining the valve post pressure deviation of the second proportional valve at the current moment by using a second comparator through the output value of the MPC controller at the current moment and the valve post pressure of the second proportional valve at the current moment.
S05: acquiring an output value of a PID controller at the current moment by using the PID controller through the valve back pressure deviation of the proportional valve at the current moment;
the specific method for obtaining the output value of the PID controller at the current moment in the step S05 is as follows:
acquiring a PID controller output value corresponding to the first proportional valve at the current moment by using a PID controller through the valve back pressure deviation of the first proportional valve at the current moment;
and acquiring the output value of the PID controller corresponding to the second proportional valve at the current moment by using the PID controller through the valve back pressure deviation of the second proportional valve at the current moment.
Specifically, the specific method for obtaining the output value of the PID controller at the current time in step S05 is as follows:
acquiring the output value of the PID controller corresponding to the first proportional valve at the current moment by using the first PID controller through the valve back pressure deviation of the first proportional valve at the current moment;
and acquiring the output value of the PID controller corresponding to the second proportional valve at the current moment by using the second PID controller through the valve back pressure deviation of the second proportional valve at the current moment.
In the step S05, the formula expression for obtaining the output value of the PID controller corresponding to the first proportional valve at the current time is:
wherein K is p E is a preset proportionality coefficient 1 (k) For the valve pressure deviation, e, of the first proportional valve at the present moment 1 (k-1) represents the valve post-valve pressure deviation of the first proportional valve at the previous time, i is a constant whose initial value is equal to 0, T is the period of step response sampling, T i E is a preset integral constant 1 (i) For the pressure deviation after the valve of the first proportional valve at the ith moment, T d To preset differential constant, u 1 (k-1) is the output value of the PID controller corresponding to the first proportional valve at the previous moment, u 1 (k) Outputting a value for the PID controller corresponding to the first proportional valve at the current moment;
the formula expression for obtaining the output value of the PID controller corresponding to the second proportional valve at the current moment is as follows:
in the formula e 2 (k) E, for the valve pressure deviation of the second proportional valve at the current moment 2 (k-1) represents the pressure deviation after the valve of the second proportional valve at the previous time, e 2 (i) For the pressure deviation after the valve of the second proportional valve at the ith moment, u 2 (k-1) is the output value of the PID controller corresponding to the second proportional valve at the previous moment, u 2 (k) And outputting a value for the PID controller corresponding to the second proportional valve at the current moment.
S06: and adjusting the position of the main valve by using a proportional valve according to the output value of the PID controller at the current moment.
The specific method for adjusting the position of the main valve in the step S06 is as follows:
and adjusting the back valve pressure of the first proportional valve and the second proportional valve through the output value of the PID controller corresponding to the first proportional valve and the second proportional valve at the current moment so as to adjust the position of the main valve.
The controller also comprises a displacement sensor, a first pressure sensor and a second pressure sensor;
the displacement sensor is electrically connected with the main valve and is used for acquiring the actual position of the main valve in real time;
the first pressure sensor is electrically connected with the first proportional valve and is used for acquiring the valve back pressure of the first proportional valve; the second pressure sensor is electrically connected with the second proportional valve and is used for acquiring the valve back pressure of the second proportional valve.
Example two
As shown in FIG. 1, a method for controlling the position of a main valve of a controller, wherein the controller comprises a first comparator, an MPC controller, a second comparator, a PID controller, a proportional valve and a main valve; the first comparator is electrically connected with the MPC controller, the MPC is electrically connected with the second comparator, the second comparator is electrically connected with the PID controller, the PID controller is electrically connected with the proportional valve, and the proportional valve is hydraulically connected with the main valve; the control method comprises the following steps:
s01: acquiring a step response sampling value output by the proportional valve at the current moment, constructing a step response model vector of the proportional valve through the step response sampling value, and constructing a step dynamic matrix according to the step response model vector;
the proportional valve comprises a first proportional valve and a second proportional valve; the specific steps for constructing the step dynamic matrix in the step S01 are as follows:
s11: acquiring a step response sampling value output by the first proportional valve and the second proportional valve according to the step response sampling;
s12: respectively obtaining corresponding step response model vectors according to step response sampling values of the first proportional valve and the second proportional valve;
s13: and constructing a step dynamic matrix according to the step response model vectors of the first proportional valve and the second proportional valve.
S02: acquiring the actual position of the main valve at the current moment, and acquiring the position deviation between the actual position of the main valve at the current moment and the preset position through a first comparator;
s03: obtaining an output value of the MPC controller at the current moment by using the position deviation at the current moment and the step dynamic matrix through the MPC controller;
the specific method for obtaining the output value of the MPC controller at the current moment in the step S03 is as follows:
s31: obtaining the predicted output value of the MPC controller at each moment after the current moment through a prediction model of the MPC controller;
it should be noted that, the prediction model used in the present invention serves the optimization operation process in the algorithm operation process, and its main function is to predict the future theoretical state and the future theoretical output of the target object based on the past information and the assumed future information of the target object, under different control methods, the algorithm can predict the theoretical state and the theoretical output at the future moment of the system, and substitutes them into the constraint condition and the corresponding performance index of the system to perform operation, so as to determine the merits of different control strategies.
S32: obtaining control increment of the output value of the MPC controller at the current moment by utilizing a rolling optimization method of the MPC controller according to the predicted output value of the MPC controller at each moment after the current moment and the step dynamic matrix;
the formula expression for obtaining the control increment of the output value of the MPC controller at the current moment in the step S32 is as follows:
wherein K is the current time, M is the control time domain, p is the optimized time domain of rolling optimization, A is the step dynamic matrix, Q is the preset error weight matrix, R is the preset control weight matrix, w is the output expected value of the MPC controller, and w p (k) To optimize the output expectancy of the MPC controller at the instant in time in the time domain,for the predicted output value of the current time obtained by optimizing the predicted output value of the MPC controller at each time in the time domain, deltau M (k) And (5) outputting a control increment of the value for the MPC controller at the current moment.
S33: acquiring an output correction value of the MPC controller at the next moment by using a feedback correction method of the MPC controller through a control increment of the output value of the MPC controller at the current moment;
in the application of industrial process control, the predictive control algorithm is a method for establishing rolling optimization in a limited domain to realize control operation in an industrial environment. The optimal performance index of each sampling moment only covers a limited time domain from the moment, and can be converted into an open-loop optimal control problem with a future limited control quantity as an optimal control quantity. After these control amounts are calculated, the predictive control applies only the control amount at that time to the target object, and when the next sampling period is reached, the time domain of optimization at that time is scrolled forward with the advance of time, and on the basis of this, it is possible to obtain that the optimization operation in the predictive control algorithm is not completed in a direct on-line state in one operation, but is repeatedly operated with the lapse of time.
The formula for obtaining the output correction value of the MPC controller at the next moment in the step S33 is as follows:
wherein S is a preset displacement matrix,for the predicted correction value of the MPC controller at the next moment obtained by the control increment of the output value of the MPC controller at the current moment,/and/or>The correction value is output for the MPC controller at the next time.
S34: and obtaining the output value of the MPC controller at the current moment according to the output correction value of the MPC controller at the next moment.
It should be noted that, in each sampling time, the real-time state of the control object is detected first, and then this feedback information is directly applied to the prediction and optimization at the next time, so that the prediction and optimization operation process of the output at the next time is established above the actual running state of the system, which is called feedback correction.
The invention adopts PID-MPC composite control, wherein the PID-MPC composite control comprises inner loop control and outer loop control, the inner loop control adopts PID control to restrain the influence effect of external interference on the system in the actual industrial control environment, the outer loop control adopts multivariable dynamic matrix control (MPC) to ensure that the system obtains optimal control and distribution effect, and the method can effectively improve the performance of the predictive control system.
S04: acquiring the valve back pressure of the proportional valve at the current moment, and acquiring the valve back pressure deviation of the proportional valve at the current moment by using a second comparator through the output value of the MPC controller at the current moment and the valve back pressure of the proportional valve at the current moment;
the specific method of the step S04 includes the steps of:
s41: acquiring valve back pressure of the first proportional valve and the second proportional valve at the current moment;
s42: acquiring the valve back pressure deviation of the first proportional valve at the current moment by using a second comparator through the output value of the MPC controller at the current moment and the valve back pressure of the first proportional valve at the current moment; and obtaining the valve post pressure deviation of the second proportional valve at the current moment by using a second comparator through the output value of the MPC controller at the current moment and the valve post pressure of the second proportional valve at the current moment.
S05: acquiring an output value of a PID controller at the current moment by using the PID controller through the valve back pressure deviation of the proportional valve at the current moment;
the specific method for obtaining the output value of the PID controller at the current moment in the step S05 is as follows:
acquiring a PID controller output value corresponding to the first proportional valve at the current moment by using a PID controller through the valve back pressure deviation of the first proportional valve at the current moment;
and acquiring the output value of the PID controller corresponding to the second proportional valve at the current moment by using the PID controller through the valve back pressure deviation of the second proportional valve at the current moment.
In the step S05, the formula expression for obtaining the output value of the PID controller corresponding to the first proportional valve at the current time is:
wherein K is p E is a preset proportionality coefficient 1 (k) For the valve pressure deviation, e, of the first proportional valve at the present moment 1 (k-1) represents the valve post-valve pressure deviation of the first proportional valve at the previous time, i is a constant whose initial value is equal to 0, T is the period of step response sampling, T i E is a preset integral constant 1 (i) For the pressure deviation after the valve of the first proportional valve at the ith moment, T d To preset differential constant, u 1 (k-1) is the output value of the PID controller corresponding to the first proportional valve at the previous moment, u 1 (k) Outputting a value for the PID controller corresponding to the first proportional valve at the current moment;
the formula expression for obtaining the output value of the PID controller corresponding to the second proportional valve at the current moment is as follows:
in the formula e 2 (k) E, for the valve pressure deviation of the second proportional valve at the current moment 2 (k-1) represents the pressure deviation after the valve of the second proportional valve at the previous time, e 2 (i) For the pressure deviation after the valve of the second proportional valve at the ith moment, u 2 (k-1) is the output value of the PID controller corresponding to the second proportional valve at the previous moment, u 2 (k) And outputting a value for the PID controller corresponding to the second proportional valve at the current moment.
S06: and adjusting the position of the main valve by using a proportional valve according to the output value of the PID controller at the current moment.
The invention is a cascade control method taking the position of a main valve as a control target, a position cascade control system related to the method actually forms two loops, one is a main valve position control loop, the other is a proportional valve control loop, the main valve position control loop is a main loop, and the main valve position is taken as a main loop control object; the proportional valve control loop is an auxiliary loop, and the proportional valve is used as an auxiliary loop control object; in the position control process, the proportional valve control loop serving as the auxiliary ring can rapidly overcome main disturbance which causes severe, frequent and large system change in the controlled process, so that the influence of secondary disturbance on the main ring control loop is very little, and then the main valve position control loop serving as the main ring further eliminates the disturbance which is not completely overcome by the auxiliary ring, so that the position change amplitude of the whole control process is small and stable, and the response speed, the control precision and the stability of the system are greatly improved.
The specific method for adjusting the position of the main valve in the step S06 is as follows:
and adjusting the back valve pressure of the first proportional valve and the second proportional valve through the output value of the PID controller corresponding to the first proportional valve and the second proportional valve at the current moment so as to adjust the position of the main valve.
The controller also comprises a displacement sensor, a first pressure sensor and a second pressure sensor;
the displacement sensor is electrically connected with the main valve and is used for acquiring the actual position of the main valve in real time;
the first pressure sensor is electrically connected with the first proportional valve and is used for acquiring the valve back pressure of the first proportional valve; the second pressure sensor is electrically connected with the second proportional valve and is used for acquiring the valve back pressure of the second proportional valve.
The position of the main valve is regulated by combining the PID controller and the MPC controller, so that the control system has strong predictive control and self-adaptive capacity, the problems of large disturbance and system oscillation in the position control process are solved, and the control precision and the robustness are greatly improved.
It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.
Furthermore, descriptions such as those referred to herein as "first," "second," "a," and the like are provided for descriptive purposes only and are not to be construed as indicating or implying a relative importance or an implicit indication of the number of features being indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
In the present invention, unless specifically stated and limited otherwise, the terms "connected," "affixed," and the like are to be construed broadly, and for example, "affixed" may be a fixed connection, a removable connection, or an integral body; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In addition, the technical solutions of the embodiments of the present invention may be combined with each other, but it is necessary to be based on the fact that those skilled in the art can implement the technical solutions, and when the technical solutions are contradictory or cannot be implemented, the combination of the technical solutions should be considered as not existing, and not falling within the scope of protection claimed by the present invention.
Claims (7)
1. The main valve position control method of the controller is characterized in that the controller comprises a first comparator, an MPC controller, a second comparator, a PID controller, a proportional valve and a main valve; the first comparator is electrically connected with the MPC controller, the MPC is electrically connected with the second comparator, the second comparator is electrically connected with the PID controller, the PID controller is electrically connected with the proportional valve, and the proportional valve is hydraulically connected with the main valve; the control method comprises the following steps:
s01: acquiring a step response sampling value output by the proportional valve at the current moment, constructing a step response model vector of the proportional valve through the step response sampling value, and constructing a step dynamic matrix according to the step response model vector;
s02: acquiring the actual position of the main valve at the current moment, and acquiring the position deviation between the actual position of the main valve at the current moment and the preset position through a first comparator;
s03: obtaining an output value of the MPC controller at the current moment by using the position deviation at the current moment and the step dynamic matrix through the MPC controller;
the specific method for obtaining the output value of the MPC controller at the current moment in the step S03 is as follows:
s31: obtaining the predicted output value of the MPC controller at each moment after the current moment through a prediction model of the MPC controller;
s32: obtaining control increment of the output value of the MPC controller at the current moment by utilizing a rolling optimization method of the MPC controller according to the predicted output value of the MPC controller at each moment after the current moment and the step dynamic matrix;
the formula expression for obtaining the control increment of the output value of the MPC controller at the current moment in the step S32 is as follows:
wherein K is the current time, M is the control time domain, p is the optimized time domain of rolling optimization, A is the step dynamic matrix, Q is the preset error weight matrix, R is the preset control weight matrix, w is the output expected value of the MPC controller, and w p (k) To optimize the output expectancy of the MPC controller at the instant in time in the time domain,for the predicted output value Deltau at the current time obtained by optimizing the predicted output value of the MPC controller at each time in the time domain M (k) The control increment of the output value of the MPC controller at the current moment is obtained;
s33: acquiring an output correction value of the MPC controller at the next moment by using a feedback correction method of the MPC controller through a control increment of the output value of the MPC controller at the current moment;
the formula for obtaining the output correction value of the MPC controller at the next moment in the step S33 is as follows:
wherein S is a preset displacement matrix,for the predicted correction value of the MPC controller at the next moment obtained by the control increment of the output value of the MPC controller at the current moment,/and/or>Outputting a correction value for the MPC controller at the next moment;
s34: obtaining the output value of the MPC controller at the current moment according to the output correction value of the MPC controller at the next moment;
s04: acquiring the valve back pressure of the proportional valve at the current moment, and acquiring the valve back pressure deviation of the proportional valve at the current moment by using a second comparator through the output value of the MPC controller at the current moment and the valve back pressure of the proportional valve at the current moment;
s05: acquiring an output value of a PID controller at the current moment by using the PID controller through the valve back pressure deviation of the proportional valve at the current moment;
s06: and adjusting the position of the main valve by using a proportional valve according to the output value of the PID controller at the current moment.
2. The method of claim 1, wherein the proportional valve comprises a first proportional valve and a second proportional valve; the specific steps for constructing the step dynamic matrix in the step S01 are as follows:
s11: acquiring a step response sampling value output by the first proportional valve and the second proportional valve according to the step response sampling;
s12: respectively obtaining corresponding step response model vectors according to step response sampling values of the first proportional valve and the second proportional valve;
s13: and constructing a step dynamic matrix according to the step response model vectors of the first proportional valve and the second proportional valve.
3. The method for controlling the position of a main valve of a controller according to claim 2, wherein the specific method of step S04 includes the steps of:
s41: acquiring valve back pressure of the first proportional valve and the second proportional valve at the current moment;
s42: acquiring the valve back pressure deviation of the first proportional valve at the current moment by using a second comparator through the output value of the MPC controller at the current moment and the valve back pressure of the first proportional valve at the current moment; and obtaining the valve post pressure deviation of the second proportional valve at the current moment by using a second comparator through the output value of the MPC controller at the current moment and the valve post pressure of the second proportional valve at the current moment.
4. A method for controlling the position of a main valve of a controller according to claim 3, wherein the specific method for obtaining the output value of the PID controller at the current time in step S05 is as follows:
acquiring a PID controller output value corresponding to the first proportional valve at the current moment by using a PID controller through the valve back pressure deviation of the first proportional valve at the current moment;
and acquiring the output value of the PID controller corresponding to the second proportional valve at the current moment by using the PID controller through the valve back pressure deviation of the second proportional valve at the current moment.
5. The method for controlling the position of the main valve of a controller according to claim 4, wherein the specific method for adjusting the position of the main valve in step S06 is as follows:
and adjusting the back valve pressure of the first proportional valve and the second proportional valve through the output value of the PID controller corresponding to the first proportional valve and the second proportional valve at the current moment so as to adjust the position of the main valve.
6. The method for controlling the position of a main valve of a controller according to claim 5, wherein the formula for obtaining the output value of the PID controller corresponding to the first proportional valve at the current time in step S05 is:
wherein K is p E is a preset proportionality coefficient 1 (k) For the valve pressure deviation, e, of the first proportional valve at the present moment 1 (k-1) represents the valve post-valve pressure deviation of the first proportional valve at the previous time, i is a constant whose initial value is equal to 0, T is the period of step response sampling, T i E is a preset integral constant 1 (i) For the pressure deviation after the valve of the first proportional valve at the ith moment, T d To preset differential constant, u 1 (k-1) is the output value of the PID controller corresponding to the first proportional valve at the previous moment, u 1 (k) Outputting a value for the PID controller corresponding to the first proportional valve at the current moment;
the formula expression for obtaining the output value of the PID controller corresponding to the second proportional valve at the current moment is as follows:
in the formula e 2 (k) E, for the valve pressure deviation of the second proportional valve at the current moment 2 (k-1) represents the pressure deviation after the valve of the second proportional valve at the previous time, e 2 (i) For the pressure deviation after the valve of the second proportional valve at the ith moment, u 2 (k-1) is the output value of the PID controller corresponding to the second proportional valve at the previous moment, u 2 (k) And outputting a value for the PID controller corresponding to the second proportional valve at the current moment.
7. The method of claim 2, wherein the controller further comprises a displacement sensor, a first pressure sensor, and a second pressure sensor;
the displacement sensor is electrically connected with the main valve and is used for acquiring the actual position of the main valve in real time;
the first pressure sensor is electrically connected with the first proportional valve and is used for acquiring the valve back pressure of the first proportional valve; the second pressure sensor is electrically connected with the second proportional valve and is used for acquiring the valve back pressure of the second proportional valve.
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