Active Handrest: A large workspace tool for precision manipulation

To address the limited dexterous workspace of the human hand, we have developed the Active Handrest. This device assists in precision manipulation tasks by extending a user’s dexterous workspace while providing ergonomic support for reduced fatigue. People use handrests to complete dexterous activities as routine as providing a signature. However, the dexterous workspace of the statically supported hand is somewhat limited. By providing consistent support over large workspaces the Active Handrest could be useful for performing precision tasks, such as surgery, upper limb rehabilitation, and machining. Our prototype Active Handrest is a planar, human–machine interface that provides support for the user’s wrist and arm while allowing the user to retain complete control over a grasped tool or manipulated device. The Active Handrest uses force input from the user’s hand, position input from a grasped tool, or a combination of these inputs. The device’s controller then converts the input(s) into handrest motions. In this paper we describe our novel device prototype and establish a baseline for its performance. Preliminary experiments were conducted to investigate the effects of control input, velocity limits, and user experience. Subsequent experiments compared the Active Handrest to various other support conditions. Use of the Active Handrest was found to significantly reduce task error and provided better speed-accuracy performance than the other tested support methods.