Comparison of active and passive dancers for periodic tension disturbance attenuation in web processing lines

Scope and method of study. This thesis compares the performance of passive and active dancers in a web process line in the presence of periodic tension disturbances. A sinusoidal disturbance, injected into the web line using an eccentric roller, is attenuated using the passive and active dancers. The piston-cylinder for the passive dancer is modeled as a gas spring with air as the compressible fluid and a model is suggested. The active dancer setup is fitted with a hydraulic actuator and the experiments are conducted for attenuation using a PID and an IMC controller.; Findings and conclusions. It is seen that the passive dancer mechanism is effective in attenuating web-tension at lower frequencies of disturbance. Its response to tension variations and its attenuation capabilities are limited due to the properties of its passive elements and its damped natural frequency. The properties of a passive dancer can be slightly varied using a gas spring and varying the pressure of the gas. This limitation is overcome by the active dancer with an actuator. The electro-hydraulic actuator, used in the active dancer has a high bandwidth compared to the electromechanical actuator. The IMC controller is found to be satisfactory in attenuating the sinusoidal disturbance up to a disturbance frequency of 28 rad/sec and easier to design than the PID controller.