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Abstract-A Cable-Driven Locomotion Interface employs two independent cable-driven haptic foot platforms constrained in six degrees of freedom (6-DOF). Its control system and its geometry are designed for performing a wide range of trajectories that could generate cable interferences. This paper presents and analyzes computational methods for determining which cable can be released from an active actuation state while allowing control in a minimal tension state, thereby ensuring that both platforms stay in a controllable workspace. One challaging task is to develop light and fast computational algorithms for hard real time processes included in haptic display applications. Seeing that releasing a cable from an active actuation state might generate discontinuities in tension values in the other cables, this paper proposes collision prediction schemes named Interference Estimated Time of Arrival in order to reduce or completely eliminate such discontinuities.

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Optimal tension control in parallel mechanisms for balancing wrench at the end-effector introduces a complex model of the overall system. Moreover, actuator saturations such as motor current and angular velocity limits impose that a non-linear system be controlled. Such a system is usually controlled sub-optimally due to the complexity of its model. In haptic applications where transparency and stability are both critical parameters, optimal performance should be achieved. This paper introduces an enhanced FPID auto-tuning based on Extremum Seeking-Tuning (ES-Tuning) which uses a different cost function to find the local optimal solution for haptic rendering and a correction on noise measurement for a high order complex system. The solution of this optimization gives a direct measure of the reel dynamic transparency evaluated by the proposed cost function.