CN102705561A - Hysteresis control method based on two-step method - Google Patents

Abstract

The invention provides a hysteresis control method based on a two-step method. The method is characterized by comprising the steps of: building a valve hysteresis model and an industrial process model in an SIMULINK of an MATLAB (Matrix Laboratory); building a main controller based on the PI (Power Inversion) algorithm and a compensating controller based on the two-step method in an OPTO22; and then connecting the MATLAB with the OPTO22 to perform communication, so as to form a feedforward-feedback control module taking the compensating controller as a feedforward controller. The method has the advantages that the defects of the prior art is overcome, the valve hysteresis in a loop is compensated by adopting the advanced control algorithm, the vibration in the industrial control loop, caused by the valve hysteresis, can be effectively eliminated without production halts, the anti-interference performance is high, the realizing mode is simple, and the control effect is good. The method can be applied to the practical industrial process.

Description

A kind of sluggish controlling method based on two-step method

Technical field

The present invention relates to a kind of sluggish controlling method, be used for the oscillation circuit that industrial process valve sluggishness causes is compensated control, belong to the Advanced process control technical field based on two-step method.

Background technique

The valve sluggishness is to cause the major reason of industrial system vibration, also be in the valve control the most generally, one of the most difficult problem that is overcome.The investigation of Honeywell company through lasting 2 years; 26000 pid control circuit systematic functions in the continuous industry process are analyzed; Draw as drawing a conclusion: have only 1/3 control loop system functional, and other control loop system performance all remains to be improved.Research points out, control system performance improvement 1% or energy utilization rate improve 1% in the industrial process, will bring several ten million even several hundred million dollars profit.

In the modern industry process,, also can therefore not stop production and safeguard, because the loss that stopping production causes is bigger even general enterprise detects the existence of control valve viscosity property.General business equipment maintenance period is half a year to 3 year, and the existence of control valve viscosity property in the meantime not only can increase the energy consumption of enterprise but also wearing and tearing that can acceleration equipment.Therefore design need not stop production and safeguard the controller that just can overcome the control valve viscosity property, and industrial process is saved energy and reduce the cost has very important meaning.Proposed at present the compensation method of the sluggish control of several kinds of valves, but some only rests on theoretical research, can not apply to complicated industry spot; Though some can be applied in the actual commercial production, has some drawbacks:

● Hagglund proposed a kind of sluggish controlling method in 2002, and soon the Knocker signal joins in the control signal and goes, and modulating valve is carried out the sluggishness compensation.There are some defectives in the method: the Knocker signal is the series of pulses signal, and the size of its three parameters can influence the quality of compensating action; Knocker compensation Control Parameter is many, and the difficulty of adjusting belongs to static compensation, in case promptly parameter is set, in servicely just can not change, and output fluctuation to weaken with the valve frequent movement be cost, this is not expect on the engineering.

● people such as Srinivasan proposed a kind of " two-step method " viscosity property compensator in 2007.The The whole analytical process of this method is on the basis of one-parameter model, to launch, and its compensator needs the sluggish parameter d of model accurately, and can only have no operation under the ideal situation of external interference, and this does not almost accomplish in the actual industrial production process.In addition, the valve location of this compensator can not be surveyed.The method is sheerly in theoretical research.

All there is narrow limitation separately in the sluggish controlling method of above-mentioned valve, and its compensation effect is also unsatisfactory.

Summary of the invention

The purpose of this invention is to provide a kind of need not to stop production just can eliminate vibration, strong interference immunity in the industrial loop, satisfy the valve sluggishness compensating control method that commercial Application HQ high quality and low energy consumption require.

In order to achieve the above object, technological scheme of the present invention provides a kind of sluggish controlling method based on two-step method, and this method is divided into following 3 steps:

Step 1: in the SIMULINK of MATLAB, set up sluggish model of valve and industrial process model;

Step 2: in OPTO22, set up based on the master controller of predictive PI algorithm with based on the compensating controller of two-step method,

Its control algorithm is following:

The input/output relation of predictive PI algorithm is: $u\left(t\right)=K(1+\frac{1}{p{T}_i})e\left(t\right)-\frac{1}{p{T}_i}[u\left(t\right)-u(t-L)]$

Wherein p is a differential operator, and e (t), u (t) are respectively the input and output of controller, and K is the inverse of process gain, T _iBe the leading time constant of control procedure, L is control procedure lag time;

Define system error E rror=SP-PV, wherein SP is system's input, PV is system's output; Stiction is a setting value less than the input SP of system, when Error is greater than or equal to Stiction, adopts master controller, otherwise adopts compensating controller; In conjunction with Fig. 4, the algorithm of compensating controller is following:

Definition Count is that counter, Period are that control cycle, Flag are flag bit, and OP is master controller output,

Set the initial value of Count, Period and Flag, Flag=0, Count is since 0 counting;

When Count=Period, Flag=0 and Error >=0, OP=OP+Stiction, Flag=1;

When Count=Period, Flag=0 and Error＜0, OP=OP-Stiction, Flag=1;

When Count＞Period and Flag=1, OP=OP+Error/T _i, Flag=0, Count=0;

Step 3: connect MATLAB and OPTO22 and carry out communication; Make the sluggish model of master controller and valve, industrial process model connect and compose close loop negative feedback control model successively; Compensating controller is connected in parallel on the master controller two ends and outputs to after the master controller as the feedforward controller of the sluggish model of valve, and the output PV of system is industrial process output.

A kind of sluggish controlling method provided by the invention based on two-step method, when there was interference in the external world, control loop can return stable state after two steps, keep good operational effect; The required Control Parameter of this method is few, and the Control Parameter explicit physical meaning, is convenient to parameter tuning.

Method provided by the invention has overcome the deficiency of existing technology; Come the valve in the compensation circuit sluggish through adopting advanced control algorithm; Need not to stop production and just can effectively eliminate the vibration that causes by the valve sluggishness in the industrial control loop, strong interference immunity, way of realization is simple; Control effectively, can be used for actual industrial process.

Description of drawings

Fig. 1 a kind of sluggish controlling method control loop block diagram provided by the invention based on two-step method;

Fig. 2 is that the valve output (MV) of the sluggish model of valve when not having sluggishness is exported (PV) comparison diagram with system;

Valve output (MV) when Fig. 3 is the sluggish model existence of valve sluggishness and controller output (OP) comparison diagram;

Fig. 4 is based on the algorithm flow chart of the compensating controller of two-step method in the present embodiment;

Fig. 5 is the systematic steady state output waveform when not disturbing in the present embodiment;

System's output waveform when Fig. 6 does not adopt compensating controller for adding in the present embodiment after the interference;

Systematic steady state output waveform when Fig. 7 disturbs the back to adopt compensating controller for adding in the present embodiment;

Embodiment

For making the present invention more obviously understandable, now with a preferred embodiment, and conjunction with figs. elaborates as follows.

OPTO22 is found in 1974, relates generally to hardware and software Products Development and manufacturing that industrial automation, remote monitoring and business data are gathered the field.Through employing standard and commercial internet, networking and computer technology, the I/O of OPTO22 and control system allow the client that all machineries, Electrical and Electronic assets are carried out data monitoring, control and collection.

The present invention has developed the real-time Monitoring and Controlling software based on OPTO22PAC Project Professional.PAC Project Professional comprises following a few part composition: PAC Control, PAC Display, OPTO OPC Server, PAC Manager etc.Algorithm use PAC Control script is programmed, and the user monitoring interface adopts PAC Display to carry out interface development.

Shown in Figure 1 is a kind of sluggish controlling method control loop block diagram based on two-step method provided by the invention, and this method is divided into following 3 steps:

Step 1: in the SIMULINK of MATLAB, set up sluggish model of valve and industrial process model;

Step 2: in OPTO22, set up based on the master controller of predictive PI algorithm with based on the compensating controller of two-step method,

Its control algorithm is following:

The input/output relation of predictive PI algorithm is: $u\left(t\right)=K(1+\frac{1}{p{T}_i})e\left(t\right)-\frac{1}{p{T}_i}[u\left(t\right)-u(t-L)]$

Wherein p is a differential operator, and e (t), u (t) are respectively the input and output of controller, and K is the inverse of process gain, T _iBe the leading time constant of control procedure, L is control procedure lag time;

Define system error E rror=SP-PV, wherein SP is system's input, PV is system's output; In conjunction with Fig. 2, Stiction is a setting value less than the input SP of system, when Error is greater than or equal to Stiction, adopts master controller, otherwise adopts compensating controller; In conjunction with Fig. 4, the algorithm of compensating controller is following:

Definition Count is that counter, Period are that control cycle, Flag are flag bit, and OP is master controller output, sets the initial value of Count, Period and Flag, Flag=0, and Count is since 0 counting;

When Count=Period, Flag=0 and Error >=0, OP=OP+Stiction, Flag=1;

When Count=Period, Flag=0 and Error＜0, OP=OP-Stiction, Flag=1;

When Count＞Period and Flag=1, OP=OP+Error/T _i, Flag=0, Count=0;

Step 3: connect MATLAB and OPTO22 and carry out communication; Make the sluggish model of master controller and valve, industrial process model connect and compose close loop negative feedback control model successively; Compensating controller is connected in parallel on the master controller two ends and outputs to after the master controller as the feedforward controller of the sluggish model of valve, and the output PV of system is industrial process output.

Two step functions below in fact compensating controller has been realized in the above control system:

The first step makes modulating valve overcome the valve sluggishness and moves to suitable aperture position;

Second step, mobile valve its position that should be under the steady state, and make valve remain on this settling position always.

Import for excitation pulse SP of system as system; SP is transferred to the sluggish model of valve through master controller and compensating controller; Output signal MV, signal MV sends feed-forward signal through compensating controller to the sluggish model of valve, and the sluggish model of valve is when accepting the master controller instruction and moving; Receive the regulation and control of feed-forward signal again in time, therefore action can be more accurate.The sluggish model output of valve signal is again through industrial process output, and industrial process output signal PV reverse feedback progressively reduces the error of control system to system input, and system tends towards stability.

Set up the simulation model of above-mentioned control system, when the sluggish model of valve did not have sluggishness, sluggish model output MV of valve and the output PV of system were as shown in Figure 2, and MV and PV reach unanimity; When the sluggish model of valve had sluggishness, sluggish model output MV of valve and master controller output OP were as shown in Figure 3, and the MV amplitude is significantly less than OP, proves that compensating controller has played good compensation effect;

Fig. 5 is the systematic steady state output waveform when not disturbing, and on the output PV of system, adds a step signal as interference, adds when not adopting compensating controller after the interference, and system's output waveform is as shown in Figure 6, and system's output output that departs from objectives is bigger; After adding compensating controller; The systematic steady state output waveform is as shown in Figure 7; System output is near fluctuation target output basically, and the systematic steady state output waveform is not similar when disturbing among Fig. 5, proves that a kind of sluggish controlling method based on two-step method of the present invention's proposition has excellent control effect.

Claims (1)

1. sluggish controlling method based on two-step method, it is characterized in that: this method is divided into following 3 steps:

Step 1: in the SIMULINK of MATLAB, set up sluggish model of valve and industrial process model;

Step 2: in OPTO22, set up based on the master controller of predictive PI algorithm with based on the compensating controller of two-step method, its control algorithm is following:

The input/output relation of predictive PI algorithm is: $u\left(t\right)=K(1+\frac{1}{p{T}_i})e\left(t\right)-\frac{1}{p{T}_i}[u\left(t\right)-u(t-L)]$

Wherein p is a differential operator, and e (t), u (t) are respectively the input and output of controller, and K is the inverse of process gain, T _iBe the leading time constant of control procedure, L is control procedure lag time;

Define system error E rror=SP-PV, wherein SP is system's input, PV is system's output; Stiction is a setting value less than the input SP of system, when Error is greater than or equal to Stiction, adopts master controller, otherwise adopts compensating controller; The algorithm of compensating controller is following:

Definition Count is that counter, Period are that control cycle, Flag are flag bit, and OP is master controller output, sets the initial value of Count, Period and Flag, Flag=0, and Count is since 0 counting;

When Count=Period, Flag=0 and Error >=0, OP=OP+Stiction, Flag=1;

When Count=Period, Flag=0 and Error＜0, OP=OP-Stiction, Flag=1;

When Count＞Period and Flag=1, OP=OP+Error/T _i, Flag=0, Count=0;

Step 3: connect MATLAB and OPTO22 and carry out communication; Make the sluggish model of master controller and valve, industrial process model connect and compose close loop negative feedback control model successively; Compensating controller is connected in parallel on the master controller two ends and outputs to after the master controller as the feedforward controller of the sluggish model of valve, and the output PV of system is industrial process output.

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