A new type of a parallel wire-driven robot is proposed in order to reach ultra-high speed. The driving principle of parallel wire systems is described. Since wires can only pull and not push on an object, at least n+1 wires are needed in order to move the object in a n-dimensional space. In this paper, taking account of the effect of such redundancy on actuation, the motion stability in wire length coordinates is analyzed by using a Lyapunov function. Using “Vector Closure”, it is proven that the hand position and orientation converge to the corresponding desired values and the internal force also converges to the desired one. Moreover, by making good use of non-linear elasticity of parallel wire driven robots, it is claimed that the internal force arising from redundant actuation can effectively reduce vibration when the high-speed robot stops at desired points. As a result, ultra-high speed with more than 40 g(g:gravitational acceleration) can be attained by using relatively small actuators.

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SUMMARYAdaptive control design schemes in the presence of input saturation have received much attention over the last two decades. However, few researchers have addressed the issue of designing the adaptive control system in the presence of unknown or variable input saturation. We propose an adaptive backstepping control method for single input uncertain nonlinear system with unknown or variable input saturation. This method uses the saturation error at previous time to estimate the saturation error at current time easily and rapidly, and the normalization based on the estimation error is introduced to ensure the stability of the whole adaptive system. We also suggest a new adaptive law to improve the performance of parameter identification in case that the uncertainty of saturation error estimation can be approximately decided. It is valid when parameters identified in the adaptive control system are taken as main design parameters of the other controllers, and especially when their accuracy has a significant influence on control performance of the whole system. Finally, simulation examples are presented to validate the effectiveness of the proposed approach.

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