Introduction in haptic control and passivity : literature study

Teleoperation aims to extend the human capabilities to manipulate objects remotely by providing the operator with similar conditions as those at the remote location. Using a well-considered type of force feedback, motion and force scaling, the precision can be increased. The ultimate goal is to reach total transparency, while remaining stable: The operator should feel as if he is manipulating the remote environment directly. This work takes a closer look at minimal invasive surgery (MIS) and haptic feedback overall. Besides an increased precision, MIS shows more advantages. For instance the fact that the medical specialists can work in a more ergonomic setup, tasks can be automated (suturing) and remote surgeons can assist local surgeons. Through the years haptic feedback developed rapidly. Major headlines in the world where directly caused by developments in the technique. For instance the race to the moon in the late 1960’s asked for remote space robots and a few years later during the big oil crisis of the 1970’s undersea robots were demanded to search for offshore oil, using unmanned submarines. During the same years, the software industry established their first businesses and asked for telerobotics in the manufacturing of the first computer chips. Since in teleoperation a human operator and an environment are involved it is hard to determine the stability of the total system using the regular robust stability criterions (hard to make a model of a human and a complex environment). The passivity approach makes it easier to determine the stability, since basically no dynamical model is needed of those subsystems and it is also applicable to nonlinear systems. After discussing passivity (and it’s extensions the scattering theory and the wave variable theory) this paper will treat different control structures using mainly the passivity theory and of every structure the practical benefit will be examined, regarding stability and transparency