Sampling of 3DOF Robot Manipulator Joint-Limits for Haptic Feedback

Teleoperation of robotic proxies can extend human control to spaces, tasks and constraints that would otherwise be intractable or unattainable. The robustness to harsh environments, scalability, precision and repeatability of robots make them ideal for dangerous or difficult missions, and their use oftentimes reduces monetary and human cost. Maneuverable robot devices can provide more flexibility and articulation, but come at the cost of kinematic complexity. The kinematics and workspace of the remote device is oftentimes dissimilar to the input device, leading to potential confusion and frustration of the human operator. One solution is to constrain the input device motion to a scaled version of remote device joint ranges. This paper presents a method for doing so with 3 degree of freedom (DOF) manipulators and input devices with kinematic dissimilarities. The approach utilizes a simple tree structure, whereby a local Cartesian workspace limit is sampled and indexed by joint. This generates a locally sampled joint limit surface, represented as a point cloud. This local point cloud is then used to provide 3DOF haptic feedback to the operator as an indication that a joint limit has been reached, and provides kinesthetic force feedback to efficiently remove the operator from that joint limit. This work can improve usability of human-robot interfaces for teleoperation by allowing users to naturally intuit remote device joint limits and avoid confusion.