Requirements for a Light-Weight Robot for Both Open and Laparoscopic Surgery

I n minimally invasive surgery (MIS), the surgeon works with long instruments through small incisions. These small incisions are the main advantage of MIS, leading to several benefits for the patient when compared with open surgery. These benefits include reduced pain and trauma, reduced loss of blood, reduced risk of wound infections, shorter hospital stays, shorter rehabilitation time, and cosmetic advantages. In contrast to open surgery, direct access to the operation field is no longer possible for the surgeon. According to [1], the loss of direct access leads to several drawbacks for the surgeon: 1) Tissue cannot be palpated any more. 2) Because of the relatively high friction in the trocar, the contact forces between instrument and tissue can hardly be sensed. [The trocar is a surgical device, which makes it possible to create incisions in a visceral cavity (i.e. thorax, abdominal cavity) and keeps it open with the aid of a tube.] This is especially the case when the trocar is placed in the narrow intercostal space (i.e., space between the ribs). 3) As the instruments have to be moved around an invariant fulcrum point, intuitive direct hand–eye coordination is lost, and because of the kinematic restrictions, only 4 degrees of freedom (DoF) remain inside the body of the patient. Therefore, the surgeon cannot reach any point in the work space at an arbitrary orientation. This is a main drawback of MIS, which makes complex tasks like knot tying very time consuming and require intensive training [2]. To overcome the aforementioned drawbacks, telesurgery systems are a promising approach (Figure 1). Within these systems, telemanipulators are key components, as they transfer the surgeon’s commands into the patient’s body. In combination with appropriate display and telepresence technologies, they allow for a high-grade immersion of the surgeon into the remote site, thus regaining virtually direct access to the operation area comparable to open surgery. The following properties of minimally invasive robotic surgery (MIRS) can be realized with appropriate technologies: 1) Manipulation forces can be measured by miniaturized sensors integrated in the instruments (e.g., see [3]). It is to be expected that the surgeon’s situational awareness is increased if the contact situation is displayed to the surgeon by suitable man–machine interfaces (MMIs). 2) By means of control algorithms and actuated surgical instruments, the correct