Sensor/Actuator Asymmetries in Telemanipulators: Implications of Partial Force Feedback

For many telemanipulators, it is often impractical to provide the same number of degrees of freedom for position control at the slave and force feedback to the master. Sensor/actuator asymmetries in telemanipulators are created when the user is able to position the telemanipulator in more degrees of freedom then the telemanipulator can provide force feedback. Most commonly, teleoperator asymmetries arise from the lack of an actuator on the master manip ulator or the lack of a sensor on the slave manipulator. While examples of systems containing asymmetries are numerous, telemanipulator asymmetries’ effect on operator performance and controller design have not been thoroughly examined. We present the necessary dynamic models of sensor/actuator asymmetries in telemanipulators. Using motivating examples and common passivity conditions, we show how these asymmetries cause “passive” control structures to be non-passive. More generally, asymmetries demonstrate challenges in creating practical, force-reflecting telemanipulators.