Integral sliding mode based switched structure control scheme for robot manipulators

This paper deals with the design of a switching control scheme for robot manipulators. The key elements of the proposed scheme are the inverse dynamics based centralized controller and a set of decentralized controllers. They enable to realize two possible control structures: one of centralized type, the other of decentralized type. All the controllers are based on Integral Sliding Mode (ISM), so that matched disturbances and uncertain terms, due to unmodeled dynamics or couplings effects, are suitably compensated. The idea of using ISM, apart from its feature of providing robustness in front of a wide class of uncertainties, is motivated by its capability of acting as a 'perturbation estimator', which is a clear advantage in the considered case. In fact, it allows one to define a switching rule in order to choose one of the two control structures featured in the scheme, depending on the requested performances. As a consequence, the resulting control scheme is more efficient from computational viewpoint, while maintaining the advantages in terms of stability and robustness of the conventional standalone control schemes. In addition, the scheme can accommodate a variety of velocity and acceleration requirements, in contrast with the capability of the genuine decentralized or centralized control structures. The verification and the validation of our proposal have been carried out in simulation, relying on a model of an industrial robot manipulator COMAU SMART3-S2, with injected noise to better emulate a realistic setup.