Fundamental Limits of Performance for Force Reflecting Teleoperation

Abstract

The quality of telepresence provided by a force-reflecting teleoperator is determined, for the most part, by the fidelity of the contact-force information fed back to the operator. These fed-back forces, however, also directly influence system stability, and in this paper we investigate the relationship between fidelity and stability with a view toward understanding how stability considerations impose fundamental limits on system performance. The key idea of our work is to draw an explicit distinction between the information conveyed by the force signal and the energy inherent in that signal. Using known physiological properties of the operator, we argue that there exists a natural partitioning between information and energy wherein information is conveyed at frequencies above roughly 30 Hz, while the energetic interaction between the slave and the environment takes place at frequencies below this. We embody this distinction in a two-channel framework that we claim provides insight into the design of force-reflecting systems. Using a 1-DOF model, we study the effect of various system characteristics, notably mass, stiffness, and damping properties, on performance and stability. This model is used to derive expressions for the maximum force-reflection ratio that guarantees stability against pure-stiffness environments and to investigate the role of various compensation elements, including local force control around the slave. Finally, a framework is developed for force-reflecting teleoperation that maximizes the force information conveyed to the operator, subject to the constraints imposed by stability considerations.

Event-Based Haptics and Acceleration Matching: Portraying and Assessing the Realism of Contact

“…The human body takes at least 100 ms to react to tactile stimuli, and higherlevel cognition takes even longer. Consequently, Daniel and McAree separate haptic feedback into distinct power and information bands, below and above 30 Hz respectively [2]. Kontarinis and Howe used vibrotactile displays to improve perception of remote accelerations during teleoperation [4], and Okamura et al improved material discrimination by displaying virtual vibrations in the form of exponentially decaying sinusoids that were empirically tuned to observed signals [6].…”

Robust Haptic Teleoperation of a Mobile Manipulation Platform

“…The direct use of the measured contact force causes a delay in the loop and the stability of the system is greatly dependent upon the mass ratio of the master and slave systems [3].…”

“…Most of these schemes provide direct contact force feedback to the user for a greater level of telepresence. However, this feedback degrades the stability of the overall system especially if the mass properties of the master and slave differ significantly [3]. This paper proposes a new teleoperation scheme that utilizes local force control while exchanging position information between the master and slave station.…”

Point-cloud-based model-mediated teleoperation

“…wave-variable transformation [5][6][7], have been developed to address this issue. However, system stability (passivity) and transparency are conflicting objectives in passivity-based teleoperation system design [4,5,8]. In [9,10], the so-called predictive display approach is developed to compensate for Overview of a typical teleoperation system (adopted from [1]).…”