Reconstruction of unwinding tension control system

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Transformation of the unwinding tension control system of gravure press (Part 2)

v. tension control system debugging

in order to give consideration to the stability of the unwinding single coil control tension and the stability of the large-scale dynamic control of the biaxial switching tension, in the debugging process, first eliminate the influence of residual magnetism on the braking torque, obtain the braking torque range and PID parameters under the single coil closed-loop state, set the open-loop control parameters, and finally adopt the strategy of open-loop + closed-loop hybrid control, Optimize the system control parameters to meet the control requirements of the system, and take the following steps:

(1) according to the instructions of convenient use, when the input is 0, adjust the offset of the two circuits respectively to make the output 0, and then adjust the two circuits to eliminate the remanence output respectively to minimize the residual braking torque

(2) preliminary setting of PID parameters and obtaining the tension control range. Set a set of basic parameters: p=20, i=10, d=0, so that the machine operates at a low speed of about 10% of the maximum speed. When the system reaches stability, if it is a full roll at this time, it is the maximum torque during normal operation. If it is a small roll at this time, it is the minimum torque during normal operation. Record the maximum and minimum output values of out1 or out2 corresponding to CDTA, and the braking torque corresponding to the maximum roll diameter and the minimum roll diameter as the basis for setting parameters of open-loop control

(31 generally choose excellent alloy structural steel) increase the scale factor P in increments of 10 to 15. When the value of P increases to a certain extent, the system will enter an unstable stage. Take 90% of the p value at this time as the set value of P

(4) artificially impose interference, such as acceleration and deceleration, and observe the system. If the system recovers to stability for too long and does not enter continuous oscillation, increase the p value; If the system enters continuous oscillation, when the electronic universal testing machine shows defects, reduce the p value. Adjust the time for the system to restore stability under interference to an acceptable range, and the international influence of the plastic extruder industry continues to rise

(5) increase the differential factor D in increments of 5 ~ 7, artificially impose interference, such as acceleration and deceleration, and observe the system. If the system recovers to stability for too long, increase the D value; Conversely, reduce the D value. The adjustment time for the system to recover stability under interference is further shortened

(6) set the open-loop control parameters. First restore the PID parameters to 0, and then connect the open-loop control input. Before the two axle switch, the braking torque is required to be minimum. When the corresponding open-loop input is adjusted, the open-loop output can be set to the minimum, which can generally be set to 0; After the two axle switch, the maximum braking torque is required. Accordingly, adjust the open-loop output corresponding to the open-loop input at this time to the maximum

(7) set the system to the mixed control mode, and then artificially impose interference. Especially in the case of double volume switching, further optimize the PID parameter setting

generally speaking, the integration factor I is not very important for the stability of the system and should be as small as possible. In the tension control system of reeling in and out, its function is to ensure the slow change of coil diameter and eliminate the steady-state error. If the scale factor p is too small, the anti-interference ability of the system is poor. In case of interference, the system will recover for a long time, and if it is too large, it will lead to super harmonic and low-frequency oscillation. If the differential factor D is too small, the dynamic response of the system is poor, and if it is too large, it will cause low amplitude and high frequency oscillation

VI. conclusion

the unwinding tension control system of the gravure press we use has been put into use for nearly one year after transformation. The actual measurement analysis and production practice have proved that the unwinding tension control system has the characteristics of high mechanical strength, good stiffness, stable operation, convenient operation, high electronic control precision, convenient operation, fast response, small overshoot, strong anti-interference ability, high steady-state precision, etc, It can meet the requirements of cigarette label printing production. Under the same production process conditions of the same product, compared with the production situation before and after the transformation, the scrap rate decreased by 0.5%, and obvious economic benefits were obtained

source: Printing Technology

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