CN102710187B - Reverse roll coating system multi-shaft crossed coupling constant-speed ratio control method - Google Patents

Abstract

The invention relates to a multi-axis cross-coupling constant speed ratio control method of a reverse roller coating system, which is characterized in that: the speed difference ratio control among metering rollers, back pressure rollers and coating rollers. The simulation results of the present invention show that the control method has robustness and fast tracking performance, the control system has strong anti-interference ability, good reliability, high control precision, and its dynamic control precision fully meets the requirements of three-roller coating transmission, and is AC synchronous The application of constant speed ratio control of motor drive system provides a theoretical basis.

Description

Multi-axis cross-coupling constant speed ratio control method for reverse roll coating system

technical field

The invention relates to a multi-motor constant speed ratio control method, in particular to a multi-axis cross-coupling constant speed ratio control method for a reverse roller coating system.

Background technique

Reverse roll coating technology is the most versatile coating method, which is widely used in the film, paper, fabric treatment and composite materials industries. It is characterized by versatility, accuracy and high productivity. From the coating thickness calculation formula ^[1] , it can be seen that the change of the coating thickness of the reverse roll is directly related to the change of the coating roll line speed V _C , the metering roll line speed V _M , and the back roll line speed V _B . The roller must maintain a strict fixed speed ratio transmission relationship to ensure uniform coating thickness and constant tension during the coating process, thereby ensuring coating quality. This requires controlling multiple motors, that is, multiple motors are used to independently drive each roller to run. Therefore, the study of multi-motor constant speed ratio control has important theoretical significance and practical application value.

In recent years, many scholars have conducted extensive research on multi-motor constant speed ratio control. At present, there are mainly two kinds of multi-motor coordinated synchronous control algorithms: non-coupling control algorithm and coupling control algorithm ^[2] . For the coordinated control of multiple motors, the non-coupling control algorithm is a control method for each axis, and its main idea is to control each motor independently. Xiao Benxian ^[3] proposed a master-slave motor constant speed ratio tracking control strategy based on the principle of phase-locked loop and reference pulse technology, designed a frequency and phase detector, and realized the transformation of the gear transmission chain to the electronic transmission chain, which greatly improved Tracking control performance and flexibility for multi-motor systems. Deng Zhiquan ^[4] aimed at the multivariable and strongly coupled control object of the three-phase asynchronous motor system, and used the feedback linearization method in the nonlinear geometric theory to realize the precise decoupling and global linearization of the dual-motor system, thereby utilizing the linear control Theoretical and precise fixed speed ratio control. Fan Jian ^[5] carried out theoretical and experimental research on the constant speed ratio control of AC motor transmission mechanical system, and proposed a constant speed ratio tracking control strategy and a variable structure feedforward compound control method, and used simulation and experiments to show that the control The method is robust and fast-tracking. In the traditional coupling control algorithm ^[6] , the feedback from the slave motor to the master motor is added, so that not only the slave motor can accurately track the master motor, but also the master motor can change its own operation when the slave motor’s operating conditions change to keep in line with Synchronization of slave motors. In 1980, Professor Koren of the University of Michigan proposed the idea of Cross-coupled Control (CCC) ^[7,8] , which provided a new way to improve the accuracy of multi-axis coordinated motion. Coupling control uses the motion synchronization error between multiple axes as a control index, and directly implements closed-loop control to achieve the purpose of improving the accuracy of multi-axis coordinated motion. Coupling control is an effective control method to improve the synchronous motion accuracy ^of multi-axis system and improve the anti-interference ability ^of the system ^{. ]} and so on have been successfully applied.

Contents of the invention

In view of the characteristics of the reverse three-roller coating constant speed ratio transmission, referring to the synchronous motor hysteresis current control strategy, the purpose of the present invention is to provide a permanent magnet synchronous motor drive system coupling constant speed ratio control control method.

A multi-axis cross-coupling constant speed ratio control method for a reverse roll coating system, characterized in that:

The speed difference ratio among metering roller, back pressure roller and coating roller can be calculated according to the following formula:

(1)

i-speed ratio; q-coating amount; q0-baseline coating amount; i0-baseline speed ratio;

According to the requirements of the product, when the diameter of each roller is the same, only need to adjust the speed of the back pressure roller and the metering roller relative to the coating roller to obtain the required coating amount, so for a fixed substrate, the speed ratio i should be kept constant , so as to ensure that the coating amount is uniform and constant;

Define the speed ratio accuracy H:

(2)

i _r - the actual speed ratio,

The design requirement for the accuracy H of the three rolls of the reverse coater is 0.5%, and w _M /w _C =0.8, w _C /w _B =1.25. w _M - the angular velocity of the metering roller, w _C - the angular velocity of the coating roller, w _B - the angular velocity of the back pressure roller;

The reference model is an ideal model with fixed structure and constant parameters, whose state equation can be described as

(3)

where Am is the coefficient matrix of the reference model.

The reference model takes the angular velocity w _i of each roll as input, and through the constant speed ratio control operation, the output w _m of the reference model is obtained

(4)

In the formula, w _m is the output of the reference model.

The output of the reference model is specified as the ideal speed output that three independent PMSM control systems should have. Due to external disturbances and random changes in internal parameters, etc., there will be an error rate between the converted actual speed output of the controlled object and the output of the reference model

(5)

The cross-coupling compensation mechanism will perform feed-forward compensation control according to the speed ratio error rate ei (i=1.2.3). The final controller will send corresponding control signals to the controlled object according to the input speed signal r ( t ), the feedback signal actually output by the controlled object and the feed-forward compensation signal, so that the speed ratio error rate ei decreases or even disappears, thus making The speeds of the three synchronous motors track the output speed of the reference model in real time, so that the constant speed ratio control of the reverse roller coating step is realized.

The simulation results of the present invention show that the control method has robustness and fast tracking performance, the control system has strong anti-interference ability, good reliability, high control precision, and its dynamic control precision fully meets the requirements of three-roller coating transmission, and is AC synchronous The application of constant speed ratio control of motor drive system provides a theoretical basis.

Description of drawings

Fig. 1 is a principle diagram of reverse three-roller coating of the present invention.

Fig. 2 is a reverse three-roll coating model of the present invention.

Fig. 3 is a block diagram of the system control structure of the present invention.

Fig. 4 is the curve of external load and input speed of the invention.

Fig. 5 is a reference diagram of the simulation results of the present invention.

In the figure: 1. Metering roller; 2. Back pressure roller; 3. Coating roller; 4. Wallboard; 5. Squeegee; 6. Coating liquid.

detailed description

In the reverse roll coating system, the speed ratio is an important factor, so the requirements for precise coordination and synchronization between the three motors are high. In this paper, the reverse three-roll coating technology is taken as the research object, and the reverse three-roll coating system has the characteristics of high synchronization accuracy. Through the analysis of its working principle and the design of the control system, a multi-motor coordinated control multi-domain physical model is established. and mathematical model; and in view of the time-varying load, the coupling of each roller speed, and the uncertain model parameters in the coating process, a coupling constant speed ratio control is designed with reference to the hysteresis current control strategy of the permanent magnet synchronous motor (PMSM) Algorithm, that is, through three independent compensation speed PID controllers, the real-time tracking control of the dynamic output characteristics of the three permanent magnet synchronous motors (PMSM) to the expected average value of the three roller speeds is realized, so as to realize the coating roller 3, metering roller 1 and Precise speed ratio control of the back pressure roller 2. For the reverse three-roller coating system, a three-roller control model was established in AMESim, and a joint simulation was carried out with ADAMS. Under the condition of time-varying three-roller load, the fast tracking, anti-interference ability and reliability of the control method were analyzed .

Modeling and Analysis of Three Roll Coating System

Principle analysis

As shown in Figure 1, the principle of reverse roll coating mainly meets the following two requirements ^[1] :

First: the direction of rotation of the metering roller 1 and the coating roller 3 is opposite, and an accurate metering gap is maintained between the two rollers, and the thickness of the film on the surface of the substrate is regulated by the roller gap and the surface speed of the metering roller 1 and the coating roller 3 .

Second: The substrate is supported by an elastic backing roll, and the film is transferred from the coating roll 3 to the substrate.

system modeling

The speed difference ratio between metering roller 1, back pressure roller 2 and coating roller 3 can be calculated according to the following formula:

(1)

i-speed ratio; q-coating weight; q ₀ -basic coating weight; i ₀ -basic speed ratio

According to the requirements of the product, when the diameters of the rollers are the same, only need to adjust the speed of the back pressure roller 2 and the metering roller 1 relative to the coating roller 3 to obtain the required coating amount. Therefore, for a fixed substrate, the speed ratio i should be kept constant, so as to ensure a uniform and constant coating amount.

Analysis of Factors Affecting Speed Ratio Fluctuation

There are many factors affecting the fluctuation of the motor speed, including uncontrollable factors: sudden changes in voltage and current, magnetic flux leakage, friction between the roller and the wall plate 4; controllable factors: elasticity of the rollers, vibration of the machine, sudden change in load, etc. This paper focuses on the ability of the system to maintain constant speed ratio transmission under the condition of time-varying load.

Define the speed ratio accuracy H:

(2)

i _r - actual speed ratio.

The design requirement for the accuracy H of the three roll speeds of the reverse coater is 0.5%. Take w _M /w _C =0.8, w _C /w _B =1.25. w _M - angular velocity of metering roller, w _C - angular velocity of coating roller, w _B - angular velocity of back pressure roller

Coupled constant speed ratio control principle

In order to overcome the influence of various nonlinear factors such as speed coupling, load disturbance, and friction between the roller and the wall plate during the operation of the three-roller coating, this paper regards it as three independent synchronous motors (PMSM) tracking system and converts the load Disturbance is treated as disturbance, by improving the robustness and adaptability of the PID controller to realize the precise tracking of the dynamic and steady-state output characteristics of the same ideal reference model by the three synchronous motor control three-roll system, so as to obtain the three-roll Precise speed ratio control.

PMSM

Permanent magnet AC synchronous motor (PMSM) has its own remarkable characteristics compared with other forms of motors: it does not require excitation current below the base speed, and there is no rotor resistance loss during stable operation, which can significantly improve the power factor; Brushes and slip rings are simple in structure, easy to use, and high in reliability; and compared to other motors with the same power factor, they are much smaller in size. These advantages make permanent magnet synchronous motors widely used in national defense, industry and agriculture, and daily life. in life.

The permanent magnet synchronous motor is a multivariable, nonlinear, highly coupled system. Its output torque is not proportional to the stator current, but a complex functional relationship. Therefore, in order to obtain good control performance, it must be decoupled from the magnetic field. These characteristics are just suitable for the vector control technology, and there is no slip frequency current in the induction motor during the vector control process of the permanent magnet synchronous motor, and it is less affected by the rotor parameters, so the permanent magnet synchronous motor is easier to realize the vector control ^[12] .

Control Strategy

For PMSM is a permanent magnet motor based on sine wave back EMF, this paper adopts the hysteresis current control strategy: compare the current given signal with the detected actual output current signal of the inverter, if the actual current is greater than the given current value , then it can be reduced by changing the switching state of the inverter, and vice versa ^[13] .

In the actual system, the angular velocity sensor and torque sensor detect the speed and output torque of the three motors. In the cross-coupling control algorithm, the elastic back roller driving motor is used as the command motor, and the others are driven motors. The desired set value of the angular velocity of the elastic backing roller is the desired value of the entire system for speed control. The speed control is realized by the conventional PID controller to realize the feedback control, maintain the stability of the system, and restrain the disturbance. System control block diagram shown in Figure 3 .

The reference model is an ideal model with fixed structure and constant parameters, whose state equation can be described as

(3)

where A m is the coefficient matrix of the reference model.

The reference model takes the angular velocity w _i of each roll as input, and through the constant speed ratio control operation, the output w _m of the reference model is obtained

(4)

In the formula, w _m is the output of the reference model.

The output of the reference model is specified as the ideal speed output that three independent PMSM control systems should have. Due to external disturbances and random changes in internal parameters, etc., there will be an error rate between the converted actual speed output of the controlled object and the output of the reference model

(5)

The cross-coupling compensation mechanism will perform feed-forward compensation control according to the speed ratio error rate ei (i=1.2.3). The final controller will send corresponding control signals to the controlled object according to the input speed signal r ( t ), the feedback signal actually output by the controlled object and the feed-forward compensation signal, so that the speed ratio error rate ei decreases or even disappears, thus making The speeds of the three synchronous motors track the output speed of the reference model in real time, so that the constant speed ratio control of the reverse roller coating step is realized.

Co-simulation and result analysis of AMESim and ADAMS

According to the above control ideas and motor parameters, a system simulation model is established in AMESim, and then combined with ADAMS for simulation.

System Simulation Model

First create 3 angular velocity variables w1~w3 in ADAMS, and set the newly created 3 variables as the input values of the 3 synchronous motors, and then use the newly created 3 variables in ADAMS as the input values of ADAMS; also create 3 Two torque variables M1~M3, assign the torque values of the three rollers to the three force variables, and use these three variables as ADAMS output values in the plant output item, and finally import the first two steps into ADAMS to make The variable names of the input and output quantities, click OK, and two software interface files (suffix inf) will be generated in the working folder. This interface file contains all the information of the ADAMS mechanical model. Then import the generated interface file into the AMESim model and connect the components in the model. The completed AMESim model diagram is shown in Figure 3: it is mainly composed of the reference model, PMSM, three-roller model, cross-coupling compensation mechanism and PID controller.

Import the ADAMS model into AMESim for joint simulation analysis. The shear force of the coating roller and the metering roller subjected to the coating solution 6 is 287.5N and 332N respectively, and the extrusion force of the back pressure roller by the substrate is 77N. The simulation time is set to 2s, and the step size is 0.001s.

Table 1 lists the parameters controlling the main components in the model.

Table 1 Parameter table of main components

Simulation result analysis

The input speed curve and the external load of the three rollers are shown in Fig. 4.

The simulation result curve is shown in Fig. 5. It can be seen from Fig. 5 that in the case of time-varying load, given the speed signal, the speed of the three rollers changes from acceleration, stability to deceleration, and there is no obvious jump in the transition process, and the acceleration and deceleration processes are carried out smoothly; during the start-up of the motor, The dynamic response of the rotor mainly depends on the moment of inertia, w _M /w _C , w _C /w _B jumps; when the motor starts, the error rate e ₁ of the differential speed ratio between the output of each motor and the ideal input is at most 0.01, and the maximum at e ₂ It is 0.011, and e ₃ is 0.003 at most, and they are all less than 0.5% after 0.5s, and gradually decrease, approaching 0; the speed ratio of the three rolls remains constant after 0.06s, without oscillation. When the speed increases and the load changes suddenly, the system can quickly stabilize, so as to obtain high-quality coating products, which verifies the rationality and reference of the scheme design of the synchronous motor coupling constant speed ratio control system based on hysteresis current control The effectiveness and robustness of the model feed-forward control algorithm.

Claims (1)

1. a reverse roll coating system multi-shaft crossed coupling constant-speed ratio control method, is characterized in that:

Speed difference ratio between metering roll (1), counter-pressure cylinder (2) and applicator roll (3), can be calculated by formula below:

(1)

I-speed ratio；Q-coating weight；Q0-benchmark coating weight；I0-benchmark speed ratio；

According to goods requirement, in the case of each roller diameter is identical, only need to regulate that counter-pressure cylinder (2) is relative with metering roll (1) to be coated with The i.e. available required coating weight of the speed of roller (3), therefore for fixing base material, speed ratio i should keep constant, thus ensures coating weight Homogeneous constant；

Definition constant-speed ratio precision H:

(2)

i_r-actual speed ratio,

Three the roller speed precision H design requirements reversing spreader are 0.5%, take w_M/w_C=0.8,w_C/w_B=1.25；

w_M-metering roll (1) angular velocity, w_C-applicator roll (3) angular velocity, w_BCounter-pressure cylinder (2) angular velocity；

Reference model is an ideal model with fixed structure and constant parameter, and its state equation is described as

(3)

In formulaAmCoefficient matrix for reference model；

Reference model is with each roller angular velocityw _i For input, control computing through constant-speed ratio, it is thus achieved that the output of reference modelw _m

(4)

In formula,w _m Output for reference model；

The output of reference model is defined as the ideal velocity output that three independent PMSM control systems should have；

Due to external interference and the change at random of inner parameter, the actual speed output after the conversion of controlled device and reference model Output between there will be error rate

(5)

Cross coupling compensation mechanism will be according to speed ratio error ratee i(i=1.2.3), Front feedback control is carried out；

Final controller will be according to input rate signalr(t), the feedback signal of the actual output of controll plant and feedforward compensation letter Number, controll plant is sent corresponding control signal, makes speed ratio error ratee iReduce so that disappearing, hence in so that three same The output speed of step motor speed equal real-time tracking reference model, thus the constant-speed ratio realizing reversing roller coat step controls.