Active Vibration Control with State Feedback in Woodcutting

Abstract

Circular saws are widely used in wood processing for applications ranging from primary lumber manufacturing to furniture industry and home workshops. They directly contribute to production problems such as poor cutting accuracy, poor surface quality, short tool life, high noise levels, and excessive raw material wastage. Vibration of the saw blade during woodcutting has been identified as a key reason for poor wood recovery. In fact, about 12% of the raw material in woodcutting ends up as sawdust due to excessive sawing gap. Efficient wood sawing is being pursued with the objective of mitigating these problems; particularly, to reduce saw blade vibration and sawdust. In this paper, we present active control of saw blade vibration using linear quadratic Gaussian (LQG) control. We outline a test rig that has been developed for our experimental investigation. The system configuration is described and the control problem is formulated. The experimental procedure for identification of a system model is described. The implementation of the LQG control scheme is outlined, and typical results from the experimental control system are presented and discussed. The developed controller is shown to be very effective in the present application, as evident from the results that have been obtained. In particular, the amplitude of the saw blade vibration has been reduced by 66% on average using active control, compared to cases with no control. Also, the cutting gap (kerf) has been reduced by 25%, from 2.00 mm to 1.50 mm, through active control. In terms of 1995 prices, this would correspond to an increased revenue of $640,000 per year for a mill producing 100 MM fbm of lumber annually.