Improved Active Handrest Performance Through Use of Virtual Fixtures

The Active Handrest is a large workspace assistive robotic device that has been shown to significantly improve the user performance of various movement tasks. This device has the potential to assist highly accurate motions without the need for a robotically enabled or comanipulated tool while allowing the user to retain complete control over a grasped tool. This paper evaluates the Active Handrest´s effect on the kinematics of user movements together with various virtual fixture control strategies to further improve the human performance while using the Active Handrest. The most effective fixture strategy for tracing straight lines is first determined. Then, this fixture strategy is directly implemented on the Active Handrest´s motions. Finally, the performance of different fixture strategies is assessed through speed-accuracy tradeoff and movement kinematics. It is concluded that fixtures implemented on the Active Handrest are as effective as those implemented on a grasped tool, which enables users of the Active Handrest high accuracy with ordinary tools such as a scalpel or paint brush. The performance is further improved when fixtures are implemented on both the Active Handrest and the grasped tool.