Roll speed and web tension regulation using two degree of freedom control systems

Abstract

In this paper, we first consider the problem of load speed regulation in a two inertia system consisting of a motor shaft connected to the load shaft via a mechanical transmission. The problem is reminiscent of a material roll (load) connected to the motor shaft through a belt-pulley and gear transmission system. In typical industrial speed control systems, the motor shaft speed is controlled under the assumption that the load shaft speed is indirectly controlled at its desired value scaled by the transmission ratio. In the presence of the transmission dynamics introduced by compliance and backlash, regulation of motor shaft speed does not translate to regulation of roll speed. The problem is further exacerbated when there are disturbances on the roll. One must consider the transmission dynamics in developing a control system that can provide the desired performance for the roll speed. We propose a two degree of freedom control system that utilizes measurement of motor shaft and roll shaft angular velocities in developing a control action necessary to regulate the roll speed. The control system consists of both feedback and model-based feedforward actions. The model-based feedforward action is generated by utilizing the model and adaptively estimating the disturbances on the roll. Experimental results conducted on a web machine indicate improved roll speed regulation in the presence of disturbances, which will be presented and discussed. Utilizing the improved roll speed regulation scheme a tension control strategy is also proposed and experiments were conducted with web transport. Experimental results indicate improved tension regulation with such a strategy.