Design of trajectories with physical constraints for very lightweight single link flexible arms

This article deals with feedforward control of very lightweight, flexible robotic arms. In particular, we develop a new, objective method of designing a trajectory that can be used as a modified input, to cancel tip vibrations during robot manoeuvres. This method takes into account the constraints found in real actuators (DC-motors), such as the maximum torque the motor can supply, and also those due to the mechanical limits of the link, like the maximum deflection before reaching the elastic limit of the link. The parameters of the internal control of the actuators are also derived from the design process, achieving the fastest performance possible without saturating the motor. Lastly, we show some experimental results which clearly demonstrate the benefits of the new trajectories by comparing them to a ramp one.