Medical Robotics

1
Medical Robotics

• Haptic feedback for biorobotics

Coen Willems
Supervisors Maarten Steinbuch Ivonne
Lammerts Coaches Loy Rovers Martijn Franken
2
Contents

• Introduction
• Master/Slave System
• Calibration
• Controller Design
• Experimental Results
• Discussion
• Recommendations

3
Introduction

• M.I.S. vs. regular surgery
• Less trauma to tissue
• More inconvenience for the surgeon

4
Introduction

• Current robotics systems
• Advantages
• 2 cameras provide 3D view
• Motion control
• Disadvantages
• Expensive
• No haptic feedback

5
Introduction

• Objectives
• Linkage of a master system to a slave system
• Slave actuated by one SMA wire and a spring
• Realizing haptic feedback on the experimental (1
  d.o.f.) setup

6
Master/Slave System

• System requirements
• Position Measurement (Master/Slave)
• Movement actuation (Slave)
• Force Measurement (Slave)
• Force Delivery (Master)

7
Master/Slave System

• Master System

1. Handles 2. Shaft 3. Movement Sensor 4. DC-Motor
8
Master/Slave System

• Slave System

1. Forceps 2. Motion mechanism 3. Drive
rod 4. Spring 5. Stiff wire 6. LVDT 7. Nitinol
wire 8. Load cell
9
Calibration

• Calibration

-Encoder Disk 2000 counts / 2p
rad Accuracy0.0031 rad
-LVDT/Position Forceps
Position0.07LVDT12.3
10
Calibration

• Calibration
• Load Cell/Torque Forceps

F(N)-73.7LoadCell(V)1.7
Low pass filter H(s)1/(0.1s1)
11
Calibration

• Calibration
• Current Amplifier/DC-motor

0.033 Nm/A
0.7A/V
12
Controller Design

• KFF

-
Xm
Xs
e
Slave Plant
Master Plant
Master Controller
Slave Controller
Environment
Fenv
Human Operator
Xm position master Xs position
slave e position error Fenv force environment
13
Controller Design

• Position Controller Slave
• SMA
• Simple On/Off Switch
• On 0.8 A
• Off 0 A

14
Controller Design

• Simulink

15
Results

• Experimental Results

0.001 Hz 0.1 Hz
16
Results
17
Discussion

• Advantages
• KFF scheme with on/off controller works
• No instability
• Good position tracking flt0.1 Hz
• Exerted torque is fed back to operator

18
Discussion

• Disadvantages
• System is slow
• no ability to dose the exerted force on
  incompressible material because of on/off switch
• Fed back force stays the same if position error
  increases

19
recommendations

• Alterations to slave design to increase speed
• Determination of SMA properties to be able to
  make a proportional actuation in stead of on/off
  switch
• Implementation of KFF model so the operator can
  tell that the forceps can not close any further