Recent advances in tele-robotic technologies will be able to replace human beings in most hazardous tasks such as space, undersea, and military operations as well as nuclear and toxic waste cleanup. Over the past decades, problems and several noticeable results have been reported mainly in a Single-Operator-Single-Robot (SOSR) teleoperation system to cope with its inherent time delay in transmission over a distance. Recently, the so-called multi-robot cooperation has rapidly emerged in many possible applications such as the plant maintenance, construction, and surgery, because it would have a significant advantage over a single robot in such cases. Thus, time-delayed control of multi-robot system is highly expected to play an important role in remote operations in dangerous or difficult-to-access environments. However, the effect of time delay would pose a more difficult problem to the Multi-Operator-Multi-Robot (MOMR) teleoperation systems and seriously affect their performance. Very recently, some efforts have been devoted to the MOMR teleoperation system. But, most of the researches as proposed to date have not yet reached a conclusion for satisfactorily dealing with the time-delay problem. Moreover, to our knowledge, no one has ever tried to teleoperate MOMR systems, where the operators are distant from each without any direct communication channel. Various methods to cope with the time delay in MOMR teleoperation systems are extensively handled in this study. Among them, the following approaches are currently under development:
Virtual dimension enlargement
The slave arm under another operator's control virtually enlarged in the local display. The uncertainty of another slave's motion through time delay is covered up by the enlarged dimension.
Estimated predictor overlay
Averaging the velocities of the delayed slave arm over the recent trajectory, we estimate the current position through time delay and have the estimated wireframe overlaid on the delayed arm.
Variable scaled rate control
The slave end-effector velocity tracks the master position and a positive scaling factor gets the master instructions scaled down/up according to the distance between two cooperating slave arms.
Virtual impedance modification
A virtual impedance is added to the master hand when two arms are approaching into collision.
Remote tele-collaboration through time delay with the Microsoft SideWinder Force Feedback Pro.
Operator in local control station with force-reflecting master hand and predictive display.
Audio-visual-haptic guided on-line graphics simulator. It signals warning against possible collision and gets the slave fine-tuned without time delay to cope with human operators' delayed visual perception.
Slave robots in a remote work site.
Local master control station with graphics simulator as well as delayed image feedback.
This study was supported in part by the Proposal-Based New Industry Creative Type Technology R & D Promotion Program from the New Energy and Industrial Technology Development Organization (NEDO) of Japan.
