The control process of the double station printing coater mainly consists in the synchronization of the speed of the multi-axis transmission and the constant tension of take-in, take-off, traction, printing and coating, as well as the calculation of the roll diameter in the unwinding process, and the unwinding of duplex positions. A, B axis switching and other process requirements. The tension control of retracting and unwinding is very critical, the winding tension should be appropriate, the tension is too small, and the paper will loosen when the paper is rewinded; the tension is too great and the material will wrinkle easily when rewinding. In this example, the tension swing pendulum is used to feedback the angle of the pendulum, so that the PID regulates the unwinding speed to achieve a constant tension and a smooth speed; in addition, since the diameter of the reel becomes smaller as the coil is unreeled, if the reel is rotated If it is kept constant, the reel's reeling speed will be smaller and smaller, so that the problem of breaking the PE film easily occurs. In order to solve this problem, control of the unwinding drive must be performed on the roll diameter calculation to calculate the reference speed.
1 VFD-VE frequency conversion closed loop vector control mode
All frequency conversion drive shafts in the system adopt the closed-loop vector control mode of encoder feedback. The reason for using the closed-loop vector control mode is to ensure that the speed control accuracy of the drive shaft can be more accurate, faster, and more stable. The difference in line speed linearity caused by slip.
2 implementation process
All four axes, including unwinding, unwinding, coating, and rewinding, need to adjust the speed control mode with constant tension. The realization process is: First, the actual reference speed of each axis is calculated by electronic spindle method, and then the reference is Speed ​​± 5% of the line speed as the allowable adjustment range of PID adjustment, and then through the collection of the position of the pendulum position angle feedback as a PID feedback value to adjust the speed of each axis of smooth and constant tension; through the normal debugging of the PID parameters finally normal When working to the limit speed of 65m/min, it can guarantee the stability of the speed, and the swinging amplitude of tension pendulum does not exceed ±1%;
3 Retractable volume control
For retractable volume control, there are two main aspects: speed control and constant tension control. Since the running linear velocity of the paper material is contacted by the pressure roller (there is no slip phenomenon), it is only necessary to separately control the speed of the winding motor.
Since the actual size of the release roll changes with the running time, its accuracy is the key to the reference speed. At present, there are usually two methods for reference: thickness method and linear velocity method.
The principle of the thickness method is based on the understanding of the thickness of the material. For each revolution of the motor, the diameter of the reeling rod will increase by two thicknesses, and the diameter of the reeling rod will reduce the thickness of the two materials. This method is mainly used in the case of a uniform thickness of the retractable roll material. The advantage is that the calculated thickness value is accurate. The disadvantage is that the user needs to input the material thickness information in the relevant parameters of the frequency converter.
The principle of the linear velocity calculation method is mainly based on the following formula: D=(G*V)/(Ï€*n). Where D is the current coil diameter, G is the mechanical transmission ratio, V is the current line speed, and n is the motor speed. The current line speed can be captured in analog or pulsed form. The advantage of the linear velocity calculation method is that it can be used in situations where the material thickness is not uniform, and there is no need to set the thickness value of the material, which reduces the requirement for the operator; the disadvantage is that the calculated current diameter value will be affected by the linear velocity acquisition accuracy. As a result, if the linear velocity fluctuates greatly, the current volume diameter will also fluctuate greatly.
The curl diameter obtained by calculating the curling diameter is substantially equal to the actually measured curling diameter, so the adjustment range of ±5% of the PID adjustment can also be calculated. To increase the elasticity, the range of ±5% can be enlarged to ± 15%, the result is still ideal, and the normal fluctuation range of tension pendulum can be guaranteed within ±1%.
Note: In the process of acceleration and deceleration, it is forbidden to calculate the diameter of the coil. Because the target speed is increased in the process of acceleration and deceleration, and the speed following of PID adjustment is late, so try to avoid calculating the coil diameter during the speed change.
4 Calculation process
When the unwinding is operated at low speed (0 to 5Hz), the error of the given speed and the actual output speed caused by the factors such as the motor slip must be larger than the PID adjustment range by 15%. Therefore, the process requires the PID adjustment range to be in the drive. An inversely proportional calculation formula appears during the operation of the axis (0 to 5 Hz): F=K/V, where F is the PID allowable adjustment range, K is a constant value, and V is the actual output frequency of the drive shaft. After the actual PID allowable adjustment range F value: ± 150% ~ 15% (0 ~ 5HZ); ±% 15 (5 ~ 50HZ).
The adjustment of the PID fluctuation range under different speed output conditions fully satisfied the high-precision PID speed control in all cases, which not only achieved the small-scale and large-scale characteristics under high-speed conditions, but also satisfied the large-scale and small-amplitude characteristics under low-speed conditions.
5 power on pre-tensioning function:
After the initial film is turned on, by judging whether the closing and unwinding lever angle is in the tensioning position, otherwise the PID adjustment will be prohibited at this stage, and the winding operation and the unwinding operation will be stopped at a fixed speed. When judging that the winding and unwinding levers return to the specified angle, the speed is switched to the PID function.
6 Unwinding duplex switching, pre-starting the backup volume when the current volume reaches the end of discharging (calculate the fixed speed operation based on the set initial volume diameter), manually stop the current volume after the splice, and replace the backup volume. The speed is switched to the PID control speed mode to complete the double station unwinding and feeding control process.
1 VFD-VE frequency conversion closed loop vector control mode
All frequency conversion drive shafts in the system adopt the closed-loop vector control mode of encoder feedback. The reason for using the closed-loop vector control mode is to ensure that the speed control accuracy of the drive shaft can be more accurate, faster, and more stable. The difference in line speed linearity caused by slip.
2 implementation process
All four axes, including unwinding, unwinding, coating, and rewinding, need to adjust the speed control mode with constant tension. The realization process is: First, the actual reference speed of each axis is calculated by electronic spindle method, and then the reference is Speed ​​± 5% of the line speed as the allowable adjustment range of PID adjustment, and then through the collection of the position of the pendulum position angle feedback as a PID feedback value to adjust the speed of each axis of smooth and constant tension; through the normal debugging of the PID parameters finally normal When working to the limit speed of 65m/min, it can guarantee the stability of the speed, and the swinging amplitude of tension pendulum does not exceed ±1%;
3 Retractable volume control
For retractable volume control, there are two main aspects: speed control and constant tension control. Since the running linear velocity of the paper material is contacted by the pressure roller (there is no slip phenomenon), it is only necessary to separately control the speed of the winding motor.
Since the actual size of the release roll changes with the running time, its accuracy is the key to the reference speed. At present, there are usually two methods for reference: thickness method and linear velocity method.
The principle of the thickness method is based on the understanding of the thickness of the material. For each revolution of the motor, the diameter of the reeling rod will increase by two thicknesses, and the diameter of the reeling rod will reduce the thickness of the two materials. This method is mainly used in the case of a uniform thickness of the retractable roll material. The advantage is that the calculated thickness value is accurate. The disadvantage is that the user needs to input the material thickness information in the relevant parameters of the frequency converter.
The principle of the linear velocity calculation method is mainly based on the following formula: D=(G*V)/(Ï€*n). Where D is the current coil diameter, G is the mechanical transmission ratio, V is the current line speed, and n is the motor speed. The current line speed can be captured in analog or pulsed form. The advantage of the linear velocity calculation method is that it can be used in situations where the material thickness is not uniform, and there is no need to set the thickness value of the material, which reduces the requirement for the operator; the disadvantage is that the calculated current diameter value will be affected by the linear velocity acquisition accuracy. As a result, if the linear velocity fluctuates greatly, the current volume diameter will also fluctuate greatly.
The curl diameter obtained by calculating the curling diameter is substantially equal to the actually measured curling diameter, so the adjustment range of ±5% of the PID adjustment can also be calculated. To increase the elasticity, the range of ±5% can be enlarged to ± 15%, the result is still ideal, and the normal fluctuation range of tension pendulum can be guaranteed within ±1%.
Note: In the process of acceleration and deceleration, it is forbidden to calculate the diameter of the coil. Because the target speed is increased in the process of acceleration and deceleration, and the speed following of PID adjustment is late, so try to avoid calculating the coil diameter during the speed change.
4 Calculation process
When the unwinding is operated at low speed (0 to 5Hz), the error of the given speed and the actual output speed caused by the factors such as the motor slip must be larger than the PID adjustment range by 15%. Therefore, the process requires the PID adjustment range to be in the drive. An inversely proportional calculation formula appears during the operation of the axis (0 to 5 Hz): F=K/V, where F is the PID allowable adjustment range, K is a constant value, and V is the actual output frequency of the drive shaft. After the actual PID allowable adjustment range F value: ± 150% ~ 15% (0 ~ 5HZ); ±% 15 (5 ~ 50HZ).
The adjustment of the PID fluctuation range under different speed output conditions fully satisfied the high-precision PID speed control in all cases, which not only achieved the small-scale and large-scale characteristics under high-speed conditions, but also satisfied the large-scale and small-amplitude characteristics under low-speed conditions.
5 power on pre-tensioning function:
After the initial film is turned on, by judging whether the closing and unwinding lever angle is in the tensioning position, otherwise the PID adjustment will be prohibited at this stage, and the winding operation and the unwinding operation will be stopped at a fixed speed. When judging that the winding and unwinding levers return to the specified angle, the speed is switched to the PID function.
6 Unwinding duplex switching, pre-starting the backup volume when the current volume reaches the end of discharging (calculate the fixed speed operation based on the set initial volume diameter), manually stop the current volume after the splice, and replace the backup volume. The speed is switched to the PID control speed mode to complete the double station unwinding and feeding control process.
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