The control design for bilateral teleoperation systems represents a challenge in finding the proper balance in the inherent tradeoff between transparency and stability. To address this problem, we propose a methodology in which we develop a parametric model of the teleoperation system. Subsequently, we exploit robust control techniques based on linear matrix inequalities to design controllers that aim to achieve a predefined performance, and are robust to bounded but arbitrarily fast-time-varying parametric uncertainties. We present analysis, simulation, and experimental results of the designed controller, thus showing that the assumptions made during modeling are appropriate and the effectiveness of the method to tradeoff perfect transparency and stability.

Robust high performance bilateral teleoperation under bounded time-varying dynamics

Decentralized robust control for teleoperated needle insertion with uncertainty and communication delay

The inherent transparency-stability trade-off in bilateral teleoperation poses a challenge to design controllers that find a proper balance between both requirements. Furthermore, when the environment of the teleoperation system varies within a wide range, a single controller might not be sufficient to achieve both stability and transparency. Therefore, we propose the synthesis of a switching robust controller that increases the environment stiffness range for which both stability and transparency is achieved. During the design we take into account the fact that environment estimators will have limited accuracy due to noise and uncertainty. Additionally, we use a parametric model of the human operator based on measurements of an operator's hand. We show the applicability of the approach by experiments on a 1-DOF teleoperated system interacting with a virtual spring.

High performance teleoperation using switching robust control

We investigated grouping by similarity of surface roughness in the context of task difficulty. We hypothesized that grouping yields a larger benefit at higher levels of task complexity, because efficient processing is more helpful when more cognitive resources are needed to execute a task. Participants searched for a patch of a different roughness as compared to the distractors in two strips of similar or dissimilar roughness values. We reasoned that if the distractors could be grouped based on similar roughness values, exploration time would be shorter and fewer errors would occur. To manipulate task complexity, we varied task difficulty (high target saliency equalling low task difficulty), and we varied the fingers used to explore the display (two fingers of one hand being more cognitive demanding than two fingers of opposite hands). We found much better performance in the easy condition as compared to the difficult condition (in both error rates and mean search slopes). Moreover, we found a larger effect for the similarity manipulation in the difficult condition as compared to the easy condition. Within the difficult condition, we found a larger effect for the one-hand condition as compared to the two-hand condition. These results show that haptic search is accelerated by the use of grouping by similarity of surface roughness, especially when the task is relatively complex. We conclude that the effect of perceptual grouping is more prominent when more cognitive resources are needed to perform a task.

Perceptual grouping by similarity of surface roughness in haptics: the influence of task difficulty.

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A. César

Papers

High Performance and Stable Teleoperation under Bounded Operator and Environment Dynamics

Switching Robust Control for Transparent and Stable Teleoperation