Environment Estimation in Teleoperation Systems

One of the main objectives of control algorithms for teleoperation systems is to have a master device mimicking the response of the remote environment, while the slave device is requested to behave as the human operator. In general, the remote environment is compliant, with a quite different behavior with respect to perfectly rigid surfaces (e.g. in surgery or human-centered applications). In these cases, the knowledge of the dynamical properties of the remote environment can be used in order to improve the transparency of the overall system. A number of analytical and computational models have been proposed in literature in order to describe the behavior of compliant materials but, for sake of simplicity, design and simulation of controllers for robotic telemanipulation are still tied to classical linear spring-damper models. On the other hand, previous experimental activities with soft materials and human tissues have demonstrated that they are characterized by dynamical effects (relaxation and creep phenomena), which cannot be taken into account by means of linear, low-order models. In this Chapter, we study the suitability of a class of nonlinear contact models to describe and emulate compliant visco-elastic environments. Their parameters, estimated on-line, can then be used to command a suitable behavior to the master device in order to render a better contact sensation to the user.