Trajectory Planning and Second-Order Sliding Mode Motion/Interaction Control for Robot Manipulators in Unknown Environments

The problem of determining an interaction control strategy, allowing a manipulator to reach a goal point even in the presence of unknown obstacles, is faced in this paper. To this end, on the basis of position/orientation and force measurements, first, a path planning strategy is proposed. The path planning is based on an a priori trajectory, which is determined without the prior knowledge of the obstacle presence in the workspace, and on a real-time approach to generate auxiliary temporary trajectories on the basis of the properties of the obstacle surface in a vicinity of the contact point, estimated through force measurements. To determine the input laws of the manipulator, a robust hybrid position/force control scheme is adopted. First- and second-order sliding mode controllers are considered to generate the robot input laws, and the obtained performances are experimentally compared with those of classical PD control. Experiments are made on a COMAU SMART3-S2 anthropomorphic industrial manipulator.