Utilising Incipient Slip for Grasping Automation in Robot Assisted Surgery

Abstract

Despite recent advances in modern surgical robotic systems, an ongoing challenge remains their limited ability to control grasp force. This can impair surgical performance as a result of either tissue slippage or trauma from excessive grasp force. In this work we investigate a force control strategy to address this challenge based on the detection of incipient slip. Our approach employs a grasper face whose shape is engineered to encourage preferential localised slips that can be sensed using embedded displacement sensors prior to gross slip occurring. This novel approach enables closed loop control of the grasping force to prevent gross slip whilst applying minimal force. In this paper we first demonstrate the efficacy of sensing incipient slip and then demonstrate how this can form a robust closed loop grasping system to maintain stable control of tissue. Results demonstrate that this approach can achieve equivalent grasping performance to a scheme employing a fixed maximal grasping force while reducing tissue loading, and thus risk of trauma. This provides the foundation for the development of automated surgical robots with adaptive grasp force control.

Incipient Slip Sensing for Improved Grasping in Robot Assisted Surgery

“…vibration, shear force, normal force distribution and optical tracking), for a detailed summary of these see the review by Chen et al [16]. We have previously produced an incipient slip sensor, for use with soft tissues, that utilises the variation of the normal force to induce predictable incipient slip events, which were monitored using a localised measurement system [20].…”

“…Our concept is based on monitoring the difference in local tissue displacement that occurs between the front and rear of the grasper, created by the propagation of slip along its length. To achieve this the grasper's surface is separated into multiple sections or 'islands' that can move independently of each other, similar to those we utilised previously [20]. As the tissue is retracted the tensile force applied to the front island causes it to move forward with the tissue, until the shear force acting between the tissue and island exceeds the frictional force, at which point the island's displacement will halt as the tissue slips.…”

Encouraging and Detecting Preferential Incipient Slip for Use in Slip Prevention in Robot-Assisted Surgery

“…The aim of our research is to produce an instrumented surgical grasper capable of inducing and then detecting preferential incipient slip before macro slip occurs that is applicable for a range of soft biological tissues and would be compatible with current surgical grasper designs. This sensor has already been demonstrated for the successful automation of surgical grasping using tissue simulants [ 18 ]. In this paper, we present the sensor concept and design before analysing its ability to reliably detect incipient slip over a wide range of test conditions, representative of those used in surgery.…”

“…In this paper, we present the sensor concept and design before analysing its ability to reliably detect incipient slip over a wide range of test conditions, representative of those used in surgery. Initial experiments were conducted using a range of tissue simulants to define the slip detection algorithm that was utilised in [ 18 ] and to evaluate it on a repeatable substrate. The complete system was then applied to the grasping of porcine liver tissue to demonstrate its efficacy for real-world application in surgical grasping for the early detection of slip when manipulating soft biological tissues.…”

“…This work builds on our prior work in the area [ 18 , 19 , 20 ]. Here, our contribution is to rigorously evaluate the ability of the system to detect slip under a wider range of clearly defined test conditions for force, retraction speed, and material stiffness.…”