Possibility of using a continuum master device to control a continuum surgical robot

1. Possibility of using a continuum master device to control a continuum surgical robot Ho Man Ng Imperial College Biomedical Engineering (BEng)

2. About Me • 3rd Year Imperial College student, biomedical engineering • Summer internship in CUHK • Interested in clinical medical research in the future Winner of the best poster in 2nd Year Group Project – developing a horse riding simulator for physiotherapy

3. What is the problem? • ESD robotic surgery using endoscope (developed by CUHK) • Surgeons’ feedback about viewpoint (at PWH) • Hard to measure distance in endoscope • Two arms covering each other • Not easy to predict and cut the submucosal tissue • ESD surgery is technically challenging for beginners, high learning curve and many complications for beginners, so haptic feedback useful for learning [1] 1. Anthony Yuen Bun Teoh et al. "Difficulties and Outcomes in Starting Endoscopic Submucosal Dissection - Springer." (n.d.): n. pag. Difficulties and Outcomes in Starting Endoscopic Submucosal Dissection - Springer. 01 May 2010. Web. 15 Aug. 2014.

4. What is a continuum robot? • Worked for narrow environments • Hyper-redundant design A section of a continuum robot, pulled by strings (in blue) The orange part is the primary backbone

5. Background information • Many existing commercial haptic devices Novint Falcon [2] HapticMaster[3] 2. "NovintFalcon." Novint Falcon. Novint, 14 Aug. 2014. Web. 14 Aug. 2014. 3. DerLinde, Van, R.Q et al.FCS Control Systems, The Netherlands (n.d.): n. pag.TheHapticMaster, a New High-performance Haptic Interface. UniversiteitTwente, 15 Aug. 2014. Web. 15 Aug. 2014.

6. Prior Work • Work has been done to do haptic feedback in simulation of Minimal Invasive Surgery [4] • Force feedback is usually the main method in haptic feedback • Done for training surgeons for Minimal Invasive Surgery • Prerecorded data of specific tissues in different organs would be transferred to the master • Difficulties include real time rendering and the difficulties to simulate realistic tool-tissue interactions 4. CagatayBasdogan et al. "Haptics in Minimally Invasive Surgical Simulation and Training." IEEE Computer Graphics and Applications. N.p., Mar.-Apr. 2004. Web. 15 Aug. 2014.

7. Prior Work • Research has also been done to provide haptic feedback to users with robotic surgical systems [5] • Experiments have been done using Da Vinci System • Focused on providing force feedback • Surgeons typically uses sense of touch to puncture tissue, pull suture through and tie knots • It was found that force feedback reduces the number of errors by a factor of three (although data is not conclusive) 5. Okamura, Allison M. " Methods for haptic feedback in teleoperated robot-assisted surgery ." National Center for Biotechnology Information. U.S. National Library of Medicine, 29 June 2005. Web. 15 Aug. 2014.

8. Design of master for haptic movement • Continuum robot is hard to map to existing haptic devices and not ergonomic • Design of a continuum master device solves mapping problems and is easier for surgeons to predict the right movement

9. Design of master for haptic movement

10. Theory – Impedance Control • Classical feedback loop methods are not suitable for controlling the haptic device • Instead, using relation between force and position as a control parameter [6][7] 6. Hogan, Neville. "Impedance Control: An Approach to Manipulation: Part I—Theory." Journal of Dynamic Systems, Measurement, and Control 107.1 (1985): 1. Web. 7. Hogan, Neville. "Impedance Control: An Approach to Manipulation: Part II—Implementation." Journal of Dynamic Systems, Measurement, and Control 107.1 (1985): 8. Web.

11. Classic algorithm for rendering with an impedance-type device[8] • Read the position of the user from the haptic display • See if there is any collision with the objects in the real environment • Calculate forces if there is any collision • Send corresponding torque commands to the motor 8. Allison M. Okamura. "Lecture 4: Kinesthetic Haptic Devices: Rendering." ME 327: Design and Control of Haptic Systems Spring 2014. Stanford University, 2014. Web. 15 Aug. 2014.

12. Static rigid body interaction • With impedance control, nothing is perfectly rigid: F=kx If xuser=xwall, F=k(xwall- xwall) Stiffness k>0

13. Damping for obstacles • Adding a dissipative term, where b is the damping coefficient • The term would only work when going into the wall • Also creates vibrations at impact point

14. Modeling for friction? (a) Viscous damping; (b) coulomb model; (c) Coulomb and viscous; (d) “stiction”; (e) Karnopp’s model; (f) the Stribeck effect 9. Richard, C., Cutkosky, M. R., & MacLean, K. (1999). Friction identification for haptic display. Proc. of Haptic Interfaces for Virtual Environments and Teleoperator Systems (HAPTICS). 19 Aug 2014

15. Another method: admittance control [3] • Inverse of impedance control • i.e.: viewed from the haptic device, it is force in, displacement out • Backlash and tip inertia eliminated • Impedance control: Performance lacking in higher forces, high mass and high stiffness[10] • Admittance control: high stiffness and minimal friction • Intrinsically register forces encountered 10. Adams, R.j., and B. Hannaford. "Control Law Design for Haptic Interfaces to Virtual Reality." IEEE Transactions on Control Systems Technology 10.1 (2002): 3-13. Web.

16. Admittance control algorithm

17. Experiments that can be done • Building a impedance controlled continuum master device and test if it is useful for controlling the continuum robot • Test and build the relationship of different tissue and its stiffness and damping value • Possibility of using admittance control to do a haptic feedback system on the continuum master device

18. Difficulties faced (for experiment 1) • Controller issues: • Faulhaber motion controller (RS232) is designed to deliver precise position and can return voltage and current • Can create elasticity but there isn’t a way to control the stiffness due to the internal feedback loop in the motion controller • Not found away to get around it yet • Faulhaber do not have a force/voltage input, which makes controlling the force directly difficult

19. Difficulties faced (for experiment 1) • Passivity issues: • If the energy feedback from the robot is larger than the original force, the system would be unstable • Oscillation may occur as well if the feedback force factor wasn’t chosen well • Hard to choose the right force due to the difficulty to change the force control with the controller used

20. Possible solutions • Use Arduino with a motor controller to directly control the voltage to the motor, which is analogue to the force • Separate the position sensor from the motor • Use a simple motor • Use admittance control and map the PVA vector through force input • Preferably force sensor close to hand

21. The way forward • Haptic feedback is a difficult topic with some of its theory already well researched • However, continuum robots is a relatively new concept • A demand in haptic feedback in surgery – force sensing technique through continuum robot is viable[11] • Useful to integrate into existing ESD surgical robot in the future 11. Xu, K., & Simaan, N. (2008). An investigation of the intrinsic force sensing capabilities of continuum robots. Robotics, IEEE Transactions on, 24(3), 576-587.

22. The way forward • Other methods to increase the user experience of surgeons can be done • Augmented reality with the opportunity to detect tumour locations is one of the directions • Using our own camera, there is an opportunity to work on such a system in the future • Replacing the need to have a haptic feedback by the visual cues

23. On another note • Other work: Capsule Solidworks

24. On another note • Visiting MISSC and help setting up and performing experiments

25. Acknowledgements • Prof. Carmen Poon • Hu Yang, Kachun and Esther in the lab • Prof. Yam in MAE Dept • Prof. Chiu, Dr. Chung and many other doctors in MISSC centre

26. Thank You!