Showing papers by "Asokan Thondiyath published in 2017"

Design of a controllable variable buoyancy module and its performance analysis as a cascaded system for selective underwater deployment

Abstract: Variable buoyancy systems (VBSs) are commonly used in underwater vehicles to achieve efficient heave motion. Most of the time, these systems are used as a part of conventional underwater vehicles w...

MagNex — Expendable robotic surgical tooltip

Abstract: This paper presents the design of a single use disposable compliant surgical tooltip for a tele-operated surgical robot. The proposed design aims at mitigating bio-fouling of surgical tools. By implementing a monolithic design for surgical tooltip, the cleaning and sterilization processes needed after every surgery for traditional surgical robotic tools is considerably simplified. The proposed design has 3 degrees of freedom (DOF) with a modified serpentine joint for enhanced buckling strength and off-axis stiffness. A magnetic force based coupling is proposed as a means of transferring power through a hermetic barrier to maneuver the tooltip. The tooltip is thus coupled through a hermetically sealed tool shaft preventing biological material from entering the tool shaft. By having a pluggable tooltip, modularity is also achieved by interchangeable tooltip instead of replacing the whole tool during surgery. A prototype of the proposed design is developed and its functional performance is validated. Owing to the magnetic nexus which forms the magnetic coupling, the tool is named MagNex.

Differential analysis of muscle fatigue induced elbow and wrist tremor in controlled laparoscopic manoeuvring.

Abstract: Background Fatigue induced hand tremor (FIT) is a primary limiting concern for the prolonged surgical intervention in minimally invasive surgery (MIS) and robot-assisted-minimally invasive surgery (RAMIS). A thorough analysis is necessary to understand the FIT characteristics in laparoscopic tool movement. The primary aim of this study is to perform a differential analysis of the elbow and wrist tremor due to muscle fatigue in laparoscopic manoeuvring. Methods We have introduced a joint angle based tremor analysis method, which enables us to perform a differential study of FIT characteristics at the individual joint. Experimental data was acquired from a group of subjects during static and dynamic laparoscopic movement in an imitative RAMIS master manipulation scenario. A repetitive task was performed with a total span of 1 h for observing the effect of muscle fatigue. Along with the joint angle variation, surface electromyography (sEMG) signal was also studied in the analysis. Results The wrist tremor is more predominant than tremor generated at the elbow, especially in highly fatigued condition. The high-frequency tremor (>4 Hz) is contributed by the wrist joint. Moreover, the variation of the wrist and elbow tremor ratio was found to be dependent upon the experience of the surgeons. Conclusions In this work, we have investigated the attribution of elbow and wrist joints in FIT during laparoscopic tool manipulation. The outcomes may be useful for the design of robot-assisted surgical manipulator, and can be used for quality assessment of surgical training as well.

Improved Planning and Filtering Algorithm for Task-priority Redundancy Resolution in Mobile Manipulation.

Abstract: Discrete time implementation of task-priority redundancy resolution using closed loop inverse kinematics with fixed sampling time may lead to discretization chatter. The chattering effect is due to switching between different closed loop behaviours whenever the corresponding external event has occurred. This effect causes high frequency oscillation with finite frequency and amplitude in both joint space motion and operational space motion which is highly undesired. In this paper, we propose a planning and filtering algorithm to improve the robustness of task-priority redundancy resolution without having the effect of chattering, while combining multiple closed loop behaviours. We also show how the null space projection in taskpriority control affects the operational space motion while switching between the behaviours. To demonstrate the effectiveness of the proposed algorithm, three different case studies are presented for a planar mobile manipulator with holonomic constraint. The results confirm that the proposed algorithm eliminates the chatter and moves the end effector on a smooth trajectory.

Stability and Transparency in Bilateral Teleoperation of a Surgical Robot: A case study

Abstract: Teleoperation plays a major role in many robotic applications such as minimally invasive surgeries, deep underwater/ space operations, hazardous manipulations etc. This necessitates the development of better controllers and architectures that are efficient for practical implementation. The systematic analysis of the developments in the field of teleoperation and the current direction of research are presented herein. This paper elaborates on the practical issues in the development of a teleoperation system, the means by which researchers have attempted to solve these, the level of success, and the future directions. The teleoperation of a surgical robot with a master-slave configuration is considered as a case study to emphasise the issues in bilateral teleoperation. Modelling of the system, the teleoperation control architecture and the stability-transparency issues are presented along with the corresponding simulation results. Finally, an architecture is suggested, which serves as a suitable platform for researchers to carryout teleoperation system analysis.