ARTIGO TÉCNICO Pedro Queirós, Cristóvão Sousa, Rui Cortesão Institute of Systems and Robotics, University of Coimbra, Portugal pqueiros@isr.uc.pt, crisjss@gmail.com, cortesao@isr.uc.pt This work was partially supported by the Portuguese Science and Technology Foundation FCT project number PTDC/EEA-ACR/72253/2006 and by the FCT National Program for Scientific Re-Equipment, REEQ/1113/EEI/2005
ROBOTIC SETUP FOR MEDICAL APPLICATIONS ABSTRACT The paper presents a robotic setup for medical applications developed at the Institute of Systems and Robotics – University of Coimbra. Computed torque control, feedback linearization and operational space techniques are used to develop a telemanipulation system with haptic force feedback. The operational space control has a position-position teleoperation architecture with a haptic device in the loop. Based on position commands, the Cartesian dimensions are controlled by a decoupled plant powered by multiple Active Observers (AOBs), which provide model reference adaptive control. In addition, an active impedance control scheme for comanipulation tasks is described following the same decoupled control structure. The system devices as well as the involved communication protocols are discussed. Finally, the developed software architecture that integrates the different system components is presented. Keywords:Telemanipulation, haptics, telepresence, comanipulation robot, active observer, impedance.
I. INTRODUCTION The impact of robotic systems in surgery promises to be comparable to the manufacturing robots in industrial production. Surgical robots and robotic systems may be seen as “smart” surgical tools that enable surgeons to treat individual patients with improved efficacy, greater safety, and less morbidity then would be possible otherwise [1]. The goal of medical robotics is not to replace the physician by a robot, but to provide a new set of versatile tools to treat patients in a faster and better way. Surgical robots can be grouped into two main groups: 1) surgeon extenders, which are operated directly by the surgeon, augmenting and enhancing the ability to manipulate surgical instruments. Examples include the Intuitive Surgical DaVinci system [2], the Zeus system, the ROBODOC system for joint replacement surgery [3], [4] and the Accuracy Cyberknife for radio-surgery [5]. 2) auxiliary surgical tools [6]. In this group, robots generally work side-by-side with the surgeon and perform such functions as endoscope holding or retraction and automatic laparoscopic camera guidance [7]. These systems typically provide one or more direct control interfaces such as joysticks, head trackers or voice control. However, there have been some efforts to make these systems more autonomous to require less surgeon control. The paper describes a robotic setup for medical applications addressing telemanipulation and comanipulation paradigms. It is organized as follows. Sections II and III describe the experimental setup and the software architecture, respectively. Sections IV and V discuss telemanipulation and comanipulation, focusing in computed torque control techniques. Finally the conclusions are summarized in Section VI.
and is connected by a CAN bus to a PC (Intel® CoreTM 2 Duo at 2.13GHz) running RTAI Linux. For simulation purposes, the WAM® can be replaced by its simulator providing a noiseless and well defined environment for testing and development. A screenshot of the simulator is depicted in Fig. 1(c). The simulation takes into account the real robot dynamic and kinematic parameters, including: link size, mass and inertia parameters. Based in the
a)
b)
II. EXPERIMENTAL SETUP Figure 1 shows the main components of the master and slave stations. The master station has a Phantom Desktop haptic device, with 6-DOF position/ orientation outputs and 3-DOF force inputs (see Fig. 1(a)). The slave station depicted in Fig. 1(b) has the WAM® medical robot, which is a lightweight anthropomorphic arm with 7 Degrees of Freedom (DOF). Since almost all joints are cable driven (only the last one has gears) the robot has almost zero backlash and is highly backdrivable. All of these characteristics make the WAM® an excellent platform for force control and human interaction applications. To measure the contact forces and moments, a JR3 force sensor is attached to the robot end-effector. The robot is joint-torque controlled
[4 ]
robótica
c) Figure 1 . Master and slave stations. a) Phantom Desktop haptic device. b) Robot manipulator WAM® 7-DOF with a JR3 force sensor at the end-effector. c) WAM® simulator screenshot.