This paper proposes a control scheme to apply in a redundant slave robot in a teleoperated application. Singularities are avoided through a damped least-squares formulation of the inverse kinematics problem. A direct approach for selecting the damping factor is proposed. The redundant degree of freedom (DOF) is used to keep the manipulator in the most manipulable position and within the joint limits. In addition, all the redundancy resolution is performed whilst feeding back information to the operator who can help to improve the performance and robustness of the whole system.

Kinematic and dynamic performance of robotic manipulators is poor when they are near singularities and workspace edges. This problem becomes more complex in teleoperated systems where there are two robots whose kinematics can be different. In these cases, neither should approach singularities or workspace boundaries. This work proposes a means of preventing the robots approaching places of risk. The algorithm computes a force proportional to the distance to singularity and/or workspace boundary. This force stops the robot moving towards that direction. It should be stressed that this strategy works in a very intuitive way in bilateral controlled systems, since the operator feels as if there are virtual springs which serve to prevent him entering forbidden regions. Finally, the algorithm has been tested successfully in a telerobotic system that consists of a Stewart platform and a 6-DOF open-chain manipulator.

A force-force controller of a master-slave force-feedback teleoperation system is proposed. This scheme is especially suitable for non-backdriveable manipulators. Forces and torques exerted by the operator and the environment and measured by a six axis force sensor are used to compute in real time a desired trajectory which is tracked by a PD controller. This system has been applied to a master-slave system, in which the master robot is a Stewart platform. The use of virtual springs prevents the platform from running into singularities and from getting close to workspace boundaries. Experimental results the satisfactory performance of control algorithm with virtual springs.

Master-slave teleoperators have to cope with tasks so different such as unconstrained motion and hard contact tasks. If the controller is tuned on one of them, the other will not perform well and may, eventually, lead to an unstable system. In this paper, an adaptive modification of the desired robot behaviour in the orthogonal direction to the contact task is proposed. This strategy makes the system stable in hard contact tasks while easy to control in unconstrained motion. Experimental results obtained with a 2-degree-of-freedom manipulator prove the effectiveness of the method.

Two mobile robots for the inspection of radioactive areas in nuclear power plants are described. Robicen III is a compact pneumatic robot of 3 kg designed for the inspection of radioactive cylindrical tanks. With a novel locomotive mechanism based on pneumatic actuators and suction pads, it is able to climb vertical walls at speeds close to 110 mm/s. MonoCaRob is a rail-guided autonomous robot for inspection in the drywell of BWR power plants. Copper rails and brushes provide a rugged and robust means for power supply and communications. A video camera and a variety of sensors can be carried by the robot during drywell inspections.