Camera Frame Misalignment in a Teleoperated Eye-in-Hand Robot: Effects and a Simple Correction Method

Abstract

Misalignment between the camera frame and the operator frame is commonly seen in a teleoperated system and usually degrades the operation performance. The effects of such misalignment have not been fully investigated for eye-in-hand systems -systems that have the camera (eye) mounted to the end-effector (hand) to gain compactness in confined spaces such as in endoscopic surgery. This paper provides a systematic study on the effects of the camera frame misalignment in a teleoperated eye-in-hand robot and proposes a simple correction method in the view display. A simulation is designed to compare the effects of the misalignment under different conditions. Users are asked to move a rigid body from its initial position to the specified target position via teleoperation, with different levels of misalignment simulated. It is found that misalignment between the input motion and the output view is much more difficult to compensate by the operators when it is in the orthogonal direction (∼40s) compared with the opposite direction (∼20s). An experiment on a real concentric tube robot with an eye-in-hand configuration is also conducted. Users are asked to telemanipulate the robot to complete a pick-and-place task. Results show that with the correction enabled, there is a significant improvement in the operation performance in terms of completion time (mean 40.6%, median 38.6%), trajectory length (mean 34.3%, median 28.1%), difficulty (50.5%), unsteadiness (49.4%), and mental stress (60.9%).

A Design Space of Control Coordinate Systems in Telemanipulation

“…To control a robot manipulator's end-effector with a spatial input device, telemanipulation systems need to map user inputs to some control coordinate system in the remote environment. The control coordinate systems in prior works fall into a few patterns, including a coordinate frame attached to the base of the robot [4]- [7], the camera [4], [5], [8], or the end-effector [4], [5], [9]- [11]. While specific choices made by individual systems have been described in prior works, this paper provides a design space for designers to understand the range of possible control coordinate systems and reason about their suitability.…”

“…Given the limitations of low-dimensional devices, their control coordinate systems should be carefully selected as the control coordinate systems represent which subspace the robot can move in. While many existing systems attach the control coordinate system to the ground plane [5], [11], [25] or the camera image plane [5], [8], [24], several alternative choices may be appropriate. In this paper, by articulating a design space of control coordinate systems, we introduce a hybrid frame that is specifically designed for low-dimensional input devices.…”