Incipient slippage detection in tactile feedback system

• Main Author: Ahmad Khairyanto Ratmin
• Other Authors: Seet Gim Lee, Gerald
• Format: Theses and Dissertations
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering::Mechanical engineering::Mechatronics; DRNTU::Engineering::Mechanical engineering::Robots; DRNTU::Engineering::Mechanical engineering::Surgical assistive technology
• Online Access: http://hdl.handle.net/10356/73392
• Institution: Nanyang Technological University

The physical isolation of surgeon from surgical instrument and patient inherent to the master-slave setup of the tele-Robotic Minimally Invasive Surgery (RMIS) results in a total loss of sense of touch compromising both diagnostic (e.g. palpation) and assistive (e.g. grasping and suturing) surgical tasks conducted. Grasping and manipulating tissue without access to coherent tactile sensations impedes natural grasping with one being unable to directly gauge excessive and inadequate grasping forces leading to higher rates of tissue perforations as well as slippages. To date, the tactile feedback system consisting collectively of i) tactile sensor to measure conditions on contact interface, ii) tactile display to relay tactile sensation to operator and iii) integrating control to relate sensor output to the tactile display, represents the foremost approach for restoring necessary tactile feedback. In contrast to systems already established for palpation and shape, there exists a dearth of systems for facilitating grasping mainly due to the complexity of innate human grasping response. The current work investigates the necessary formulation and configuration of such a tactile feedback system and its subsequent application to resolve impaired grasping in RMIS. A three-step approach was undertaken to resolve the problem of impaired grasping in RMIS through tactile feedback system. The first step involved the review of literature pertaining to psychophysical studies of precision human grasping to identify and understand the intrinsic biology and derive the physiological requirements. The next step involved the identification and selection of potential hardware and approach analogues to human physiology for both sensing and display elements of the tactile feedback system together with a framework for effective application of the entire system. The final step consisted of modeling and experiments conducted necessary for the effectiveness of the framework. The solution developed within the thesis is aimed to provide for sufficient grasping transparency within a teleoperation setting. It consists of a novel incipient slippage tactile feedback system designed to be implemented under a unique framework with an underlying hybrid shared control architecture to compensate for intrinsic delay in data transmission between local and remote sites. The framework proposed is designed to facilitate prompt partial to fully automated response on the remote site to mitigate communication lag in the event of imminent slip while relaying incipient slip sensation to the master allowing for operator awareness. The critical element for the proposed system is quick detection of incipient slippage. The results obtained from experiments conducted with the designed piezoresistive incipient slip sensor achieved a 77% detection rate with a best detection time of 0.2s prior to incipient slippage. Failed detections were observed in situations when normal force applied were close to the minimum and maximum operational limits of the sensor. To facilitate the framework, an extension to Ho’s Two Dimensional Beam Bundle was formulated to enable analysis of microvibration phenomenon at the moment of incipient slip model. By modeling each individual beam’s vibration with a spring and dashpot configuration, the characteristic frequency and threshold magnitude unique to incipient slippage could be identified. As accurate identification of stiffness and damping ratio values remains a source of potential error, further study and elaboration on the methodology for identifying these parameters would be required.