Center winding function introduction
As shown in Figure 1, the center winding control consists of three main parts: tension setpoint processing—tension control can vary with the winding diameter; diameter calculation function; and tension PID control. The basic characteristics of center winding are:
● The refresh time for tension control is 10-30ms.
● Tension-based ramp function
● Tension control taper function
● Tension limit alarm
● Multi-material tension PID parameter set
● Speed PID P-value adjustment
● Acceleration compensation function
● Roll diameter arrival indicator
● Multiple initial roll diameter selections and roll diameter measurement
● Roll diameter calculation limitations—The rate of change in roll diameter calculation is adjustable; limitations apply when the roll diameter calculation direction is incorrect.
1. Tension setting processing
As shown in Figure 2, the tension setting process, also known as the taper control function, aims to ensure consistent tension inside and outside the roll during winding, or consistent tightness inside and outside the roll, to prevent roll deformation during storage. The relationship between tension setting and roll diameter is not linear but hyperbolic.
2. Tension Unit
As can be seen from Figure 3, the actual setpoint of the PID is the setpoint after taking into account the taper function. At the same time, par-1941 is a very important parameter that has a great influence on the tension system.
3. Diameter calculation function
As shown in Figure 4, the diameter calculation is based on D = line speed / winder speed × core1. Multiple initial roll diameters can be selected. After the roll diameter is reset, the effective roll diameter value is the first initial roll diameter. The calculated roll diameter value remains unchanged when the machine is powered on; after power is off and then on again, it is the same as the roll diameter reset, as shown in Figure 4.
4. Overall Layout Diagram
As shown in Figure 5, the center winding also has a manual forward and reverse adjustment function. At the same time, the total setpoint of the frequency converter is the speed setpoint corresponding to the winding diameter plus the PID adjustment amount, as shown in Figure 5.
Several important technical parameters
1. Three parameters related to roll diameter calculation: line speed scale (1924)
This parameter is a coefficient that measures the maximum linear velocity relative to the given linear velocity pulse. Its meaning is that when the number of lines per revolution of the linear velocity encoder is fixed, and the machine is operating at its maximum linear velocity, the linear velocity value calculated based on the roll diameter is 100,000.
It can be obtained using the following formula:
1926—winder speed scale
1926—Similar to 1924, this parameter is adjusted so that the motor speed value in the roll diameter calculation unit is 100000 when the roll diameter is at its minimum, i.e., the motor speed is at its maximum, and the number of lines per revolution of the encoder reflecting the motor speed is determined.
This parameter can also be obtained using the following formula:
1925—speed match scale
This parameter determines the speed at which the motor should operate at its minimum winding diameter when the linear speed is at its maximum. This parameter is related to the mechanical transmission ratio, the PID adjustment, and the inverter's maximum speed setting.
The following factors need to be considered:
When the roll diameter is at its minimum, the speed at which the motor should run corresponding to the maximum linear speed is determined based on the mechanical parameters. This speed is generally 90% of the maximum motor speed set by the frequency converter (parameter 3-03), that is, the maximum adjustment amount left for the PID is 10% of the maximum motor speed. It should also be noted that parameter 1940 (PID output limit) should be set to a maximum of 16384 x 10%.
2. Several parameters related to PID control that require special attention: 1941 -- PID effect verses diameter
This parameter is used to determine the P value of the PID controller corresponding to the change in roll diameter. When the roll diameter is large, and the tension changes requiring speed adjustment, the PID adjustment will be smaller than when the roll diameter is small, meaning a smaller P value is needed. Conversely, when the roll diameter is small, a larger PID adjustment is required. Figure 6 visually illustrates this relationship (as shown in Figure 6).
"1930"line speed acceleration feed forward
This parameter is used to compensate for tension fluctuations caused by changes in linear velocity. When the linear velocity changes rapidly, if the PID control is insufficient to maintain stable tension, this function can be considered. The principle is to superimpose a speed adjustment variable related to the linear velocity change onto the PID output. Practice has shown that this function is very effective in compensating for these fluctuations.
The P-values of the PID controllers corresponding to the large and small rolls of "1948" and "1949".
These two parameters are the P values of the speed PID controller for empty and full rolls when the motor control mode is speed closed-loop. These values are obtained at the beginning of commissioning using the MCT10 oscilloscope function or the PID debugging interface of the synchronous control card, with the rolls empty and full. The accuracy of these values directly affects the tension stability during large and small roll operations. These two parameters can be used in conjunction with 1941.
The settings for other winding-related parameters are the same as those for the inverter in non-winding control (such as motor parameter settings, AMA, closed-loop speed settings, etc.), and will not be repeated here.
Through debugging and practical experience in some projects, it has been proven that the center winding control function of FC302 is relatively complete, has good performance, and high reliability, making it worthy of promotion and application.
