Abstract: An apparatus for controlling a let-off motion in a loom having a let-off motion motor includes a tension detector for detecting a warp tension to produce a tension correction signal, a control unit responsive to the tension correction signal for producing a speed signal, a driving amplifier for controlling the let-off motion motor in response to the speed signal, a warp coil diameter detector for issuing a warp coil diameter correction signal inversely proportional to the diameter of a warp coil on a beam to the driving amplifier, and a normal-reverse rotation control unit responsive to the warp coil diameter correction signal for selectively applying prescribed normal- and reverse-rotation signals dependent on a rotation command to the driving amplifier. With this arrangement, the motor is rotated at a desired constant speed for feeding out or rewinding the warp yarn for a desired length irrespectively of the warp coil diameter.

Abstract: A method of controlling a motor-driven let-off motion in a loom including a system for controlling a let-off motion motor includes the steps of sampling a variation of warp tension during each revolution of a main shaft of the loom, effecting at least proportional and integral control modes on the average of sampled values, adding a proportional and integral output to a basic speed signal at a prescribed ratio, and applying a sum signal to the system for controlling the let-off motion motor.

Abstract: The amplitude of a signal (original waveform) produced by weft sensors is relativized, and the signal waveform is analyzed in various aspects based on multiple parameters to discriminate a weft yarn and a jet of fluid accurately. More specifically, a discriminating function is calculated beforehand from a signal indicative of the weft yarn and jet of fluid under normal weft insertion conditions, and a signal produced in actual detection operation is compared with the discriminating function to determine whether the weft yarn is present or not. The discriminating function can be obtained by extracting feature parameters from a signal generated by the weft sensors, and relativizing the feature parameters with respect to the original signal waveform to find a reference quantity. The feature parameters include the original waveform per se, a differentiated value thereof, an integrated value thereof, frequencies in certain frequency ranges, and sampling averages of the above parameters.