Task-specific Multiple-arm Minimally Invasive Surgical Device Design Using Cooperative Kinematic Isotropy Indices

The transition from multiple-port to single-port robotic systems in minimally invasive surgery (MIS) procedures has made flexible, dexterous manipulation an essential capability. The requirement that single-port MIS devices span an enclosed surgical workspace through only one access point while avoiding collateral damage to surrounding tissues necessitates the employment of mechanically sophisticated, kinematically redundant device architectures. These redundant architectures, while capable of achieving clinically-acceptable performance levels on complicated MIS procedures, are difficult to design and can easily result in economically prohibitive or technically impractical solutions. The problem of balancing clinical functionality and design economy in single-port MIS devices becomes even more challenging when the dexterous use multiple surgical tools is required for a given procedure. This research presents a design methodology aimed at reducing the number of degrees of freedom needed to achieve dexterous motion for a multiple-arm single-port MIS device. This design methodology exploits the availability of multiple manipulator arms by quantifying device dexterity in terms of cooperative manipulability, such that the dexterity of two or more non-redundant manipulator arms can be synergistically combined to achieve a high level of motion redundancy. This methodology, in theory, can be used to design multiple-arm MIS devices such that each arm is specialized for a particular type of motion, thus obviating the need for more versatile, redundant manipulator arms which innately require higher DOFs and, by extension, demand greater mechanical sophistication and device cost. The concept of cooperative kinematic isotropy, an extension of prior work on weighted global isotropy indices, is developed as a multiple-arm MIS device fitness metric. This metric quantifies kinematic isotropy as the aggregate isotropy of two or more manipulator arms, and allows the treatment surgical procedures as a task-specific, hybrid set of individual and cooperative manipulation tasks. The efficacy of cooperative kinematic isotropy is demonstrated on the design of a fourarmed single-port MIS device designed for blood vessel anastomosis procedures that typically require such a hybrid set of manipulation tasks. Results show that cooperative kinematic isotropy is an effective means reducing MIS device complexity while maintaining adequate levels of kinematic dexterity for specific surgical procedures. The author concludes that this new design fitness metric, while heuristic in nature, holds the potential to improve both the clinical value and the economy of cutting-edge, multiple-armed, single-port MIS systems. Figure 1. MIS DEVICE WITH FOUR MANIPULATOR ARMS