Preliminary study of virtual nonholonomic constraints for time-delayed teleoperation

Direct teleoperation with multisecond time-delayed telemetry between master and slave is challenging for humans to perform. When controlling a holonomic robot with many degrees of freedom, operators may incidentally provide commands in an intended direction without realizing their mistake until receiving feedback several seconds later. For some applications, imposing a virtual nonholonomic constraint (VNHC) on the motion of the end effector can help prevent operators from moving in an unintended direction by reducing the number of controllable degrees of freedom. This paper presents the development of a VNHC for a planar time-delayed telerobotic task, motivated by an on-orbit telerobotic satellite servicing operation. We also describe a nonholonomic virtual fixture (NHVF) that adheres to the VNHC to further reduce the potential for operators to input mistaken commands. We report the results of a pilot study in which teleoperation with a VNHC was found to have comparable task performance to holonomic planar teleoperation, while decreasing operator workload. The NHVF was found to decrease performance slightly, though user feedback indicated that a differently implemented virtual fixture and controller may improve performance.