Framework for Human Haptic Perception With Delayed Force Feedback

Abstract

Time delays in haptic teleoperation affect the ability of human operators to assess mechanical properties (damping, mass, and stiffness) of the remote environment. To address this, we propose a unified framework for human haptic perception of the mechanical properties of environments with delayed force feedback. In a first experiment, we found that the delay in the force feedback led our subjects to underestimate all the three mechanical properties. Moreover, subjects perceived additional damping or stiffness properties that the environment did not possess. It was found that the extents of these changes in the perception depend on both time-delay magnitude and the frequency of the movement with which subjects interacted with the environment. This was due to the fact that subjects were not able to distinguish the delaycaused phase shift in the movement-force relation from changes in the three mechanical properties. Based on this, we proposed a framework that allowed for a prediction of the change associated with delayed force in perception of mass-spring-damper environments. The framework was corroborated by a second experiment, in which a combined mass-damper environment was tested. Our hypotheses that the delay would cause subjects to underestimate the mass but overestimate the damping and that the extents of the under-and overestimation would differ between individual subjects due to the difference in the interaction frequency were confirmed.

Perception Centered Transparency Evaluation of Wave-Variable Based Bilateral Teleoperation

“…In this section, our framework [8] is extended to describe the perception of dynamical properties in teleoperation. We first briefly describe the principle of this framework, then propose the perception-based transparency evaluation approach.…”

“…Humans use the patterns between the excitation movement of their manipulator and the force feedback they receive to estimate the mechanical properties of a dynamic system [8], [10]. More specifically, stiffness is usually estimated on the basis of how much force is perceived with a displacement (spring force), mass is related to the effort to change the movement direction (inertia force), and damping is identified from the force resisting the movement velocity (viscous force).…”

“…Changes in the observed relations (in other words, changes in the three force components) lead humans to perceive the mechanical properties in a different way. Thus, a changed perception of mechanical properties is not necessarily caused by an actual change in the properties of the dynamic system [8]. Delays in the transmission channel, motor dynamics, filtering and so forth, can all result in a change in perception of mass, spring and damper properties [8], [10], [11], [12].…”

“…In this study, we use recent advances in understanding of human perception of haptics [8], to systematically investigate the effect of the wave-variable transformation on human haptic perception, for cases where delays are present in the transmission channel. Using this approach the perception of all three mechanical properties of an arbitrary linear environment can be studied over the full range of potential manual excitation.…”

“…The foundation of our proposed method is laid by the frequency-domain framework discussed in [8]. This framework offers a systematic understanding of how the human perception of mechanical properties (mass, stiffness and damping) of an arbitrary linear environment changes by a teleoperation system, or haptic interface.…”