Sofie, a robotic system for minimally invasive surgery

Developments in surgery are aimed at increasing patient value by improving the efficacy of procedures and decreasing patient trauma. In line with these developments, surgeons nowadays employ robotic systems for minimally invasive surgery (MIS). At the Eindhoven University of Technology, the Netherlands, Sofie is developed, a new robotic system for minimally invasive surgery. The system provides haptic feedback, precision, a compact design and high dexterity, enabling a further increase in patient value. Sofie is a so-called robotic master-slave system, shown in the figure. The master is operated by the surgeon, thus controlling the slave robot, which in turn manipulates the instruments. Two pen-shaped handles form the interface to the surgeon. In combination with visual feedback, the interface creates an intuitive working environment by virtually placing the hands of the surgeon on the instrument part inside the patient. The surgeon’s hand movements are measured using high-resolution encoders, enabling accurate control of the slave robot movements. A motor for each degree of freedom in a handle of the interface provides haptic feedback of the instrument force to the surgeon. Where possible, a direct drive minimizes friction [1,2]. Developments in robotic MIS often focus on compliant mechanisms for the slave robot, complicating dynamic force measurements required for haptic feedback. In contrast, the basis of the Sofie slave consists of a pre-surgical setup that is rigidly connected to the operating table. A platform is positioned above the patient. From the platform, the robotic arms manipulate the individual endoscopic instruments with respect to the patient. This layout leads to a short and stiff force-path between the instruments, as well as between the instruments and the operating table. The short and stiff force-path is advantageous for the dynamic system behavior. Accurate force measurements used for haptic feedback, facilitate high accuracy handling up to 10 Hz. Furthermore, the layout results in a compact, lightweight and robust design.The compactness of the design improves access to the patient during surgery and reduces the system mass considerably. Moreover, the system is easy to handle and pre-surgery setup of the system can be done quickly. Finally, an ’elbowwrist’configuration at the tip of an instrument provides high dexterity in the surgical area, reducing deflection of the external manipulating arm [3].To date, a proof-of-concept of the slave and a preliminary master are available.Furthermore, a hardware cabinet with software is available, enabling control of the slave robot using the master. Haptic feedback to the surgeon is developed further after successful preliminary tests with the team surgeons. Completion of the proof-of-concept is scheduled for mid-2011. [1] R. Hendrix, P.C.J.N. Rosielle and H. Nijmeijer (2009), Design of a haptic master interface for robotically assisted vitreo-retinal eye surgery, Int. Conf. Adv. Robot., pg. 1-6.[2] J.H. Grasman (2008), Mechanical design and construction of a 5 DOF haptic master device for an eye-surgery robot, Technical report, DCT 2008.111, Eindhoven University of