Kourosh Zareinia, Yaser Maddahi, Nariman Sepehri, Tim Olson, and Wes Mueller
Telemanipulation, power line maintenance, hydraulic manipulators, virtual fixture, performance analysis
We present an experimental evaluation of three schemes that enable a hydraulic manipulator to be controlled by two commercially available hand-controllers. The tested hydraulic telemanipulator is employed to partially substitute for, and work cooperatively with, linemen for live transmission line maintenance. The two hand-controllers are a seven-function joystick, which is provided by the manipulator manufacturer, and a PHANToM haptic device. The effectiveness of each scheme is validated by conducting several live power line maintenance tasks in a laboratory setting. First, the performance of the hydraulic telemanipulator is evaluated under joint-mode (JM) control scheme, whereby the hydraulic manipulator is guided through direct mapping of the angular displacements of joystick joints to the angular displacements of manipulator joints. The performance of the entire system is evaluated using three indices: task completion time, control effort, and amount of the manipulator end-effector movement to accomplish a task. The same tests are repeated when the operator runs the system under coordinated-mode (CM) control scheme, in which the position of the PHANToM haptic device end-effector is mapped onto the position of the hydraulic manipulator implement. In the CM scheme, the force capability of the haptic device is not utilized. The tasks under the JM scheme are shown to require more time to complete than under the CM scheme. Besides, the control effort and the distance travelled by manipulator end-effector, under the CM scheme, are smaller, as compared to the JM scheme. To further enhance the performance, an impedance-type forbidden-region virtual fixture is added to the CM scheme using the haptic capability of the PHANToM device. The virtual fixture generates a force helping the operator avoid unwanted movements in performing repetitive maintenance tasks. Examination of the performance of the proposed augmented coordinated-mode (ACM) control scheme demonstrates the best performance. Qualitative studies indicate the participants acknowledge that the proposed system is helpful for novice linemen to get familiarized with maintenance activities and for experts to perform tasks easier using robotics technology.
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