Abstract

The tracking performance of a single link pneumatically actuated robot arm has been investigated. The actuator pressure dynamics were considered, and an exact model knowledge integrator backstepping-based, IB, controller was designed with flow rates as the system’s control inputs. A more realistic valve flow model was then developed with valve control currents as the system inputs. Exact model knowledge based plant inversion techniques were used to compute the required control current given the desired flow rate and chamber pressure. In order to avoid reverse flow in the valves and singularities in the flow function, the controller gains were adjusted to ensure that the chamber pressures were maintained above and below the exhaust and supply pressures, respectively, throughout the experiments. Furthermore, flow choking, i.e. valve saturation, imposed further limitation on the system’s bandwidth. The tracking performance of the IB controller, when compared to linear PD control, was found to provide superior tracking performance. Finally, it is hypothesized that the tracking speed for IB control can be increased, by varying the value of the computed (i.e. desired) control based on the desired direction of motion.

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