It is noted that a head-mounted display (HMD) system would be a useful teleoperator system display if it increased operator performance of the desired task but could degrade performance because of display update rate limitations and communication delays. 3-D tracking and pick-and-place tasks are simulated to characterize performance levels for a range of update rates and delays. How performance changes as the display is altered to maintain the update rate is also examined. The results of the update experiments indicate that performance levels degrade only slightly until the update rate is below 1 or 2 Hz. Attempts to maintain update rate by eliminating display features such as stereo and occlusion cues show that the presence of either cue alone is sufficient to maintain performance levels in the simple, short-term tasks considered. Delays also degrade performance in both manipulation tasks considered. These HMD performance problems are not lessened by the presentation of a predictive feedback display. Instead, the delay in the head movement tracking loop must be eliminated. >

Some of what one needs to know about using head-mounted displays to improve teleoperator performance

The authors evaluate the performance and try to identify the strategies of human operators (HOs) teleoperating a robot along 2-D-trajectories in simulations of place-like tasks in an obstacle encumbered environment. The experiments utilize computer graphic simulations of a remote robot whose end-effector displacements are dynamically controlled in the X-Y plane by the HO's hand displacements. The performance is described in the various displayed conditions in terms of movement duration, spatial and temporal errors, and energy. The data show that performance depends on the nature of the cues and instructions provided to the operators. Comparative analysis of the various conditions suggests that visual feedback position control is used when continuous static or dynamic information about the trajectory is provided, while feedforward control, corrected by sampled visual information, is adopted when a self-generated movement can be planned and executed. The data also show that for a given set of execution cues, equivalent performance is achieved in both visual frames of reference. >

Hand movement strategies in telecontrolled motion along 2-D trajectories

Proposes a new type of visual interface system for teleoperated systems. Remote operations, particularly those in space, require robotic devices that are capable of performing a variety of complex mechanical manipulations with a high degree of precision and reliability. These devices must also be able to act and react accordingly to unforeseen circumstances that arise as a result of the unpredictable nature of space. Since fully autonomous motion for robots in space environments is not yet realizable, these systems must be controlled by direct dialogue through an ergonometrically designed user interface. Effective display, that includes accurate depth perception, of the remote scene is essential and vitally important for these interfaces. Although stereoscopic vision systems have been in existence for several years, most produce non-linearly mapped (distorted) images. The system proposed in the paper produces linearly-mapped images, thus facilitating the execution of teleoperated tasks. >

A linearly-mapping stereoscopic visual interface for teleoperation

Visual Factors Affecting Human Operator Performance with a Helmet-Mounted Display

In this study, an educational tool was prepared for a direct current (DC) motor, proportional (P), integrated (I) and derivative (D) speed controller with a shorter term and more economic education of the control systems. Parallel with the improvements of industrial technology, the development of computer and control technology has magnified the importance of either the theoretical or practical education of the motor speed control. The education of motors speed control in laboratory is very important, but this education is usually difficult because of a lot of abstract equations, difficult motor dynamic models and PID parameters. To overcome the mentioned negativities, an education tool was prepared for the education of DC motor speed control with PID controller. The tool which was prepared on C# environment has a flexible structure and a graphical interface. It has enabled the analysis of working principles of the P, PI, PD and PID control and traceability of the system response by the help of graphics, under different conditions created by changing the values of PID parameters. Besides, the motor could control the motor speed and reference speed and the changed PID parameters can be observed in the distance space over the internet.

	 

	Key words: DC motor speed control, PID control, educational tool, PIC16F877, motor control over the internet.

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An educational tool for DC motor PID speed controller

With major emphasis on simulation, a university laboratory telerobotics facility permits problems to be approached by groups of graduate students. Helmet-mounded displays provide realism; the slaving of the display to the human operator's viewpoint gives a sense of 'telepresence' that may be useful for prolonged tasks. Using top-down 3-D model control of distant images allows distant images to be reduced to a few parameters to update the model used for display to the human operator in a preview model to circumvent, in part, the communication delay. Also, the model can be used as a format for supervisory control and permit short-term local autonomous operations. Image processing algorithms can be made simpler and faster without trying to construct sensible images from the bottom. Control studies of telerobots lead to preferential manual control modes and, in this university environment, to basic paradigms for human motion and thence, perhaps, to redesign of robotic control, trajectory path planning, and rehabilitation prosthetics. Speculation as to future industrial drives for this telerobotic field suggests efficient roles for government agencies such as NASA. >

D. Lee

Papers

Telerobotics: problems and research needs