In this paper, a virtual reality-based construction tele-robot control system is investigated. The system consists of a servo-controlled construction robot, two joysticks for controlling the construction robot, and virtual workspace environment displayed by HMD. The position and shape of the task objects in virtual workspace environment are updated in real-time on basis of image information obtained by a stereo camera fixed in the remote field. The method of passive automatic viewpoint (PAV) has been proved to be superior in operability, safety, and reduction of stress than the conventional three-screen visual display method. However, PAV will not change when the construction robot doesn't move. In this case, it is difficult to finish the work task for the operator. To overcome the shortcomings, active viewpoint movement by a HMD named 3Dvisor device is introduced into this system, and two different viewpoint trajectories with straight-line and curved trajectories are used to move viewpoint. At last, the evaluation experiment results based on risk measurement using PAV and active viewpoint movement methods are both included. These experiments indicate that active changing of viewpoint by 3Dvisor device is effective to enhance safety in operation.
