Effect of Delay and Bandwidth on Haptic Task Performance

Performing dextrous tasks with robotic telemanipulation is becoming increasingly important. Teleoperation allows safe access to remote and dangerous setting such as outer space and undersea environments (Fig. 1), and can enhance dexterity at small scales and in confined spaces in minimally invasive surgery. Performance of telepresence tasks is often limited by the latency involved in communication over long distances, the bandwidth of the tele-operation system, and the task environment.

Fig. 1. Remotely-operated undersea robots at the Deepwater Horizon oil spill in the Gulf of Mexico (Source: Associated Press)

This study investigated the effects of different time delays and bandwidth limitations on human task performance during a simple haptic assembly task, based on a typical peg-in-hole model, under static and moving-target conditions. The assembly task is analyzed in terms of two phases. Phase I is free motion phase, where the peg is moved from start-line towards the hole, using visual feed-back, and achieves first contact with rigid surface where the hole is located. Phase II is motion-and-force control phase, after the peg attains first contact and being manipulated into the hole using visual and force feedback; the end-point of Phase II is successful insertion of peg into the hole.

Fig. 2. Magnetic Levitation Haptics Device (Source: Butterfly Haptics LLC)

In this study, human subjects were instructed to perform a virtual assembly task by relying on visual feedback from the computer screen and force feedback from the haptic device (Fig. 2). This haptic interface was selected for this study because it features zero static friction, zero mechanical backlash, and the highest bandwidth and resolution compared to conventional linkage-based haptic devices.