Modern warp-knit electronic let-off systems are control […]
Modern warp-knit electronic let-off systems are controlled in two ways, using warp beam surface speed encoders or without warp beam surface speed encoders, and their control principles are different. When the warp beam surface speed encoder is not used, the pulse signal of the warp beam speed is directly taken from the pulse encoder on the warp beam motor to indirectly measure the displacement of the warp beam, which is a semi-closed loop mode. Using a warp beam surface speed encoder, the warp beam warp speed signal is obtained by a speed encoder that is pressed against the warp beam surface in a full closed loop manner. Since semi-closed-loop servo systems are easier to implement than full-closed-loop servo systems, and modern servo motors already have very accurate feedback accuracy, semi-closed loop control methods are now used.
The warp knitting machine is driven by a spindle motor, and each time the spindle rotates, the warp knitting machine weaves a course. Each warp beam is driven by the warp beam motor through the reducer for active feed, and a warp beam encoder is installed on the warp beam motor, and the pulse signal is sent as a warp beam angular displacement feedback signal. The process parameters required by the fabric (the outer circumference of the shaft, the inner circumference of the warp beam, the number of turns, the amount of the warp) are input to the control unit 2 through the control terminal 1 (keyboard, touch screen, etc.) before the operation. When the machine is running, the spindle pulse signal is sampled periodically, and the angular displacement of the warp beam motor is determined according to the accumulated number of spindle pulses, the input process parameters and other parameters.
The actual angular displacement of the warp beam motor is fed back to the control unit through the pulse encoder of the warp beam motor. The position difference is determined by comparison, and then the position difference is converted into the speed adjustment value by the control program, thereby determining the speed of the warp beam motor. The command value is output to the DC drive device, and the motor is driven to feed the warp beam according to the required amount of the process.