Keywords: Control , Hardware , Haptics , Haptic interface, control, telesurgery

During this final project, a simplified 1-DOF prototype of a teleoperated forceps with force feedback has been built, which is -- in contrast to other systems encountered in literature -- able to handle a wide range of tissues. A bilateral controller structure is used to synchronize information about forces and positions between the two remote systems. Experiments with the laboratory setup resulted in the development of a set of general rules and techniques to design high quality haptic controllers that can be used under a wide range of operating conditions. During this presentation these techniques will be shown and discussed.

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Robotic surgery is becoming a popular technique for certain procedures since benefits of endoscopic techniques have become general knowledge. However, one of the major shortcomings of the present generation of master-slave robotic systems is the lack of haptic feedback; the surgeon that remotely controls the robot is not able to feel what is happening inside the patient.

In order to get a better insight into master-slave systems, a final student project has been Iinitiated by the biorobotics group at the Eindhoven University of technology. The goal of the project was to design and implement a master-slave system, in which a human operator uses a master device to manipulate a remote slave-device. The distance between the master and the slave is limited to a few meters. Special attention has been paid to the design of a robust haptic master-slave controller.

The project consisted of three stages:
1.) A comprehensive literature study has been performed to obtain a better understanding of medical master-slave systems and all problems that are encountered during the design of such systems. The outcomes of this study have been published in a separate report. Only the most relevant proceeding will be recapitulated in this report.
2.) A laboratory setup has been designed and implemented, based on the requirements obtained from the literature study.
3.) Several controller architectures have been studied in simulations.Later on, these have been implemented and evaluated on the laboratory setup.

The first part of this report gives an introduction to medical robotics and discusses the design of the laboratory setup. In the first chapter, the minimally invasive surgery procedures are explained and an overview of commercially available systems is given. Also, a comprehensive explanation of human sensory is given, in order to understand what is needed to achieve ''high quality'' force feedback.
The knowledge of this preliminary study is used to construct a simple one degree-of-freedom laboratory setup, as discussed in chapter three. The setup consists of a master manipulator with force feedback and a slave manipulator actuated by an ordinary DC motor, too. Because of the low-bandwidth requirements, a relatively low sample frequency can be used; this means that the forceps can be controlled with relatively simple hardware and existing communication protocols.

The second part of the report deals with the design of the controller that connects the master and slave device. Generally known controller strategies from literature are used to get a better insight into the problem, after which some parts of the controller tuning are optimized and improved by defining a set of general rules of thumb. In addition, a H? plant has been used to automate the design. Unfortunately, this technique did not give better performance than the classic controllers.
One of the major problems encountered when tuning the controller for the slave-position are the enormous changes in the environmental properties. During a typical operation in the body, the slave comes in touch both with (relatively) still materials (when grasping a needle or touching a bone) and soft tissues, sometimes even with nothing during free movement in the air. This means that the slave controller should be robust against enormous changes in the remote environmental system. Also the master environment exhibits relevant changes in parameters; the major properties of the human hand vary linearly with increasing grip-force.