1. Design and Control Challenges for a Surgical Radiographic Imaging System
Tim Elmore
Orthopaedic Biomechanics Laboratory
Department of Mechanical & Aerospace Engineering
University of Florida

2. The Motivation What surgeons can see… What surgeons want to see…

3. The Motivation
Current O-arm technology remains in sterile field, giving surgeon limited access to patient
The standard in industry …
Over 100 ft3 total volume!

4. The Motivation
Existing project development… Gator-Ray ! + =

5. Design Challenges for Surgical GatoRay
Kinematic
DOF
Obstacles
Reach
Accuracy
Kinetic
Payload mass
Velocity/Acceleration
Bearing life
5 degrees of freedom
OR table, surgeons, equipment
Under OR table to lateral view
+/- 1mm, +/-1 deg
30-60kg (65-130lbs)
0.25m/s, 2.5m/s^2
1,500,000 cycles (100/day, 40yr)

6. Mitsubishi PA10-6CE Specifications
Six Degree-of-Freedom Robot Arm
3-phase AC Brushless Servo Motors
Harmonic Drive Transmissions
Manufacturer Specified
Positional Repeatability of ±0.1mm AND
Joint Resolver Accuracy
= ±0.44 arc min (0.0073º)
10kg payload limit

7. Mitsubishi PA10-6CE Specifications
This payload would result in a 700% overload!

8. Alternative Manipulators
Panasonic VR-032 Robot
Axes: 6
Payload: 32 kg
H-Reach: 1866 mm
Repeatability: ±0.15 mm
Robot Mass: 580 kg
Mounting: floor, ceiling
Disadvantages:
Size
Mass
EE rotations are translation dependent
Cost ($20,000 used)
Table Height:
32 inches/810mm

9. Alternative Manipulators
Parallel Manipulators
Degrees of Freedom: 6
Payload: high (>30kg)
Repeatability: good (<1mm)
Robot Mass: low (<200 kg)
Disadvantage:
Limited rotation angles
Limited translations

10. Alternative Manipulators
Ballscrew/Rotary tables
Degrees of Freedom: 1 per table
Payload: high (>100kg)
Repeatability: good (<1mm)
Robot Mass: low (<200 kg)
Advantages:
Each axis is customizable
Mass supported by frame, not torque

11. The Proposed System (v0.1)
X-Ray Source
Undertable
Robot

12. The Proposed System (v1.0)
PA-10
X-Ray Sensor
X-Ray Source
Under table
Robot

13. The Proposed System (v1.0)
X-Ray Source Z Y X
Undertable
Robot

14. The Proposed System (v1.0)

15. Design Goals for Surgical GatoRay
Kinematic
5 DOF (3 translation, 2 rotation)
Reach around table into lateral view
Displacement: 3 translation, 2 rotation
Accuracy 0.2mm/axis, 1mm total
Kinetic
30-60kg payload
0.5m/sec velocity, 5m/sec2 acceleration
1,500,000 cycles at 30kg load

16. Kinematics By inspection, task space dependencies: Rx = f(xjs,Θzjs)
Ry = f(yjs,Θzjs)
Rz = f(zjs)
Θx = f(Θxjs)
Θz = f(Θxjs, xjs, yjs) Z Y X

17. Kinematics

18. Kinetics Motor choices Servo Stepper Pros: torque, speed
Cons: size, price, control
Stepper
Pros: size, price, control
Cons: torque, speed

19. Kinetics
Servo Control
Input
Output
Stepper Control
Input
Output

20. Stepper Motors

21. Stepper Motors 125kg horizontal payload 30kg vertical payload time