Fuzzy logic control of a hydraulic system

This paper presents the implementation of a fuzzy logic controller on an automated machine for mechanical processing of salmon. The prototype machine, as developed in The Industrial Automation Laboratory, is an innovative and automated version of a fish cutting machine. It is able to considerably reduce wastage of fish meat during processing, by automatically adjusting the position of the blade of the cutter with respect to the fish that is being processed. The machine consists of an intermittent-motion conveyor system to move the fish forward, a pneumatically activated guillotine-type blade that operates in the vertical direction, an X-Y horizontal table which carries the cutting blade assembly and is driven by two hydraulic actuators, and a digital CCD camera that takes the image of a fish for geometric sensing before it is cut. A Proportional-plus-derivative (PD) type fuzzy logic controller is developed and implemented successfully for driving the cutter assembly. The performance of the fuzzy logic controller is investigated, with respect to the control specifications for the machine. The real time controller operates in sampling periods of 1 ms; consequently, the membership functions are designed so that only four rules are fired at each sampling period, thereby enabling real time processing. Processing stability of the controller may be adjusted by 9 central rules. Criteria for choosing the membership functions of inputs and output are discussed.