Spring-based tactile array for assistive robotic surgical applications

Tactile sensing is highly desirable for robotic surgery, more specifically minimally invasive surgery, during tissue/organ manipulation. For safe handling and safe grasping of tissues, the two most important aspects are the monitoring and controlling of force and the stiffness information that exists at the sensor-tissue interface. In this study, a spring-based tactile sensing system is used to measure both the interacting forces and stiffness in surgical assistive applications. A differential analysis is performed to obtain the stiffness of a compliant object whilst individual elements of the proposed sensing array experience different deflections when they come in contact with the object. A lumped model formulation for tactile array performance shows that larger differences in stiffness between the force sensing elements provide higher sensitivity in evaluating the object stiffness. For benchmarking of our sensing principle, a macro tactile-sensor array is designed and tested. Different stiffness combinations of the sensing elements show an inverse linear relationship between the stiffness of the object and the output signal magnitude of the stiffness sensing unit. The proposed tactile array based on spring-based stiffness sensing has high potential for safe grasping/handling of the tissues when integrated into the jaws of a surgical grasper during the minimally invasive robotic procedures.