We propose here to deal with the optimization of velocity profiles of manipulator robots with a minimum time criterion subject to thermal constraints. This paper deals with the real impact of thermal limitations on optimal velocity profiles and the methods to calculate the corresponding optimal trajectories. We first calculate analytically the optimal solution in a simple case in order to verify the validity of the numerical algorithm and also to present a general methodology to calculate optimal trajectories in robotics using results from the theory of calculus of variations and not from the theory of optimal control. We derive then a numerical algorithm based on the discretization of the time law through an interpolation with non uniform cubic splines. This algorithm shows robust and efficient convergence properties and the trajectories thus generated were executed successfully on a Staubli Rtimes90

This paper deals with optimizing the task cycle time of industrial robots integrated in complex robot cells. Trajectory optimizers are usually based on models and can't properly deal with uncertainties due to interactions between the robot and its environment. We propose here a trajectory optimizer with hardware in the loop which can take into account constraints such as maximum authorized temperature and maximum authorized torque. Our approach is based on unconstrained optimization algorithms without derivatives and penalty methods. Experiments on real industrial applications showed good robustness properties of this algorithm even with a high number of parameters and with changes of the robot task

It is shown that in hybrid position/force control as well as in multi-robot cooperation and teleoperation, the desired behavior of the system can be defined in terms of a massless mechanism whose joints act as ideal position or force sources. Based on this remark, a simple and robust controller is proposed. Experiments validate the approach.

In a teleoperation system, assistance can be given to the operator by constraining the telerobot position to remain within a restricted subspace of its workspace. A new approach to motion constraint is presented in this paper. The control law is established simulating a virtual ideal mechanism acting as a jig, and connected to the master and slave arms via springs and dampers. Using this approach, it is possible to impose any (sufficiently smooth) motion constraint to the system, including non-linear constraints (complex surfaces) involving coupling between translations and rotations. Physical equivalence ensures that the controller is passive. Experimental results obtained with a 6-DOF teleoperation system are given. Other applications of the virtual mechanism concept include hybrid position-force control and haptic interfaces.