A Mechatronic and Model-Mediated Approach to Bilateral Teleoperation LoTESS: Towards a Force Feedback Telesurgical System (Een mechatronische en model-gebaseerde aanpak van bilaterale teleoperatie LoTESS: een telechirurgisch systeem met krachtterugkoppeling)

Abstract

People have always been fascinated by the ability to interact with an environment or with another person at a distance or behind a barrier. In minimally invasive surgery, the body wall is an example of such a barrier, since the surgeon loses his/her direct vision and manipulation ability. To reduce the additional complexity of minimally invasive surgery, teleoperation systems have entered the surgical theatre. These systems provide the surgeon with a feeling of immersion into the surgical workspace by restoring the natural hand-eye coordination. Nowadays, these systems are frequently used, despite a total lack of haptic feedback, often mentioned as their major drawback. Bilateral teleoperation, which restores the sense of touch, constitutes the core of this PhD thesis. It allows a person to manipulate an environment via a robotic slave device while force feedback is provided through a master device. The challenge of bilateral teleoperation is to find a good balance between the often conflicting requirements for performance and stability. The first part of this thesis presents a systematic analysis of the coupled stability properties of two state-of-the-art force sensing-based controllers. The analysis uses the classical two-port passivity and absolute stability methods along with in this thesis proposed bounded environment passivity method. The latter allows the specification of a model structure for the environment as well as the inclusion of bounds on the environment parameters. The analysis quantifies the effect of rigid-body dynamics, structural flexibilities, control parameters and signal filters, along with their interconnectivity. Based on this analysis, rules of thumb are defined for the master and slave hardware design as well as for the control design. The second part of the thesis describes the development of LoTESS, a teleoperation system for keyhole surgery that provides reliable force feedback. The force feedback requirement was the primary concern during the development. Design decisions are made according to the aforementioned rules of thumb for hardware and control design. LoTESS consists of three subsystems that are also valuable as separate units: a new 3-d.o.f. robotic device that can be used as a haptic joystick, a robotic device for keyhole surgery that uses a passive trocar support device to obtain a controlled motion of the instrument tip and an extracorporeal force measurement system. The combination of these subsystems with a force-sensing based controller and an adaptive rule for the damping at the master, results in a system that is both transparent in free space and stable in contact with the envisioned environments. The last part of this thesis looks into scenarios where the rules of thumb for hardware and control design cannot be applied, i.e. scenarios that are characterised by the presence of an inevitable and significant time or phase lag between the master and slave. Model-mediated teleoperation is presented as a powerful alternative for these challenging scenarios. The models are interpreted as time-varying signals and from this perspective, the stability of model-mediated teleoperation is discussed. Several case studies are described that consider models of various complexity, including an object location, a linear stiffness and a plane with variable location and orientation. These case studies are used to illustrate the concepts of the predictive power of a model, model switching, enhanced transparency and sensor fusion for model-estimation. Preview of LoTESS: http://www.youtube.com/watch?v=zWjs3Sr3tuInrpages: 340status: publishe