Fuzzy logic control of a teleoperated log loader machine

In nonautomated unstructured environments, a machine such as a hydraulic log loader has no model of either itself or the world, and the operator has to control it at a joint-mode level. The operator can be more productive by controlling the machine in task coordinates, whereby the implement direction and speed are first decided by the deflection of a 3D joystick handle. Then, the appropriate control signals to the hydraulic actuators are determined by a computer control system. In this article the application of fuzzy logic to the development of a real-time hydraulic positioning control system for such machines is demonstrated. The control requirements of hydraulic actuation are met by development of (i) a PD-type fuzzy controller with simple set of membership functions and specialized rules and, (ii) a novel offset compensator for removing the steady-state regulating and tracking errors. Experimental results, performed on a Caterpillar 215B-based log loader, are presented