1. Precise Automated Kinematic Calibration of RCM Robots Checkpoint Presentation Group6

2. About our Project Precise Automated Kinematic Calibration of RCM Robots Main Goal: Quantify the error of Optical Tracker, Robot Remote Center of Motion Important Steps: Calibrating the accuracy of Polaris Optical Tracking System Quantify the error of RCM Update Kinematic Model

3. Status Done: – Report on the accuracy and precision of Polaris tracker (minimum) – In Process: Submitting Paper to Engineering Urology Society Conference 2012 To-Do: – Observe Revolving Needle Driver Robot (Expected) – Identify errors in RCM motion (Expected) – Update Kinematic Model (Maximum)

4. Background of Polaris From NDI Manual 3D RMS Volumetric Accuracy3D RMS Repeatability acceptance 0.350 mm0.200 mm

5. Background of Polaris From other papers Accuracy assessment and interpretation for optical tracking systems, Andrew D Wile, 2004 -Good: RMS analysis, 3D pyramid shape, 1500 position readings -Limit: Sample number Weak Apparatus (small table mill) No information about coordinate system registration Comparative Tracking Error Analysis of Five Different Optical Tracking Systems, Rasool Khadem, 2000 -Good: Compare many trackers, use passive/active markers - Limit : Only looked at precision Did not align apparatus with tracker (plate with holes) Only 100 samples

6. Polaris Error Quantification: Objectives How many samples must we take? Where in the tracker volume should we read? What accuracy and precision can we get?

7. Polaris Error Quantification: Coordinate Systems Directions which the observed Marker will travel

8. Step 1: Machine Vibration Conclusion: Do not take readings while spindle is turning

9. Testing Methods 1D, 2D tests

10. 1D Precision Test: How many samples? Carried out along Polaris Z Conclusion: 500 samples is OK

11. 2D Accuracy Test: Point Cloud Registration Tracker ^---^ Here

12. 2D Accuracy Test: What Subset for Registration? 9 pts 16 pts All

13. 2D Test: Point Cloud Registration Closest Point: 32 micron precision, 152 micron accuracy Furthest Point: 69 micron precision, 231 micron accuracy

14. 2D Test: Point Cloud Registration Results XYZ AccuracyMean0.00250.01250.1036 (mm)Min0.00010.00080.0116 Max0.00780.02980.2315 PrecisionMean0.0484EuclideanDistance (mm)Min0.0314 Max0.0705

15. Methods 3D test set up

16. 3D Volume Test: Pyramid Slices

17. Scaled Precision Radii and Accuracy Vectors show non-uniform error

18. 3D Volume Test: Individual Points Closest Point: 19 micron precision, 367 micron accuracy Furthest Point: 23.7 micron precision, 276 micron accuracy

19. 3D Volume Test: Middle Points Middle Point: 25 micron precision, 31.5 micron accuracy Conclusion: Accuracy not so great at extremes of point cloud

20. 3D Volume Test: Numbers Results XYZ AccuracyMean0.01520.03490.1904 (mm)Min0.00060.00010.0017 Max0.03750.07370.3868 PrecisionMean0.0423EuclideanDistance (mm)Min0.0024 Max0.0737

21. Conclusions CNC more reliable, relatively accurate than other calibration apparatus Can get more precise readings than previously thought – take more samples Precision generally worse in Polaris Z – Should measure in XY planes Accuracy is distorted over tracker volume – Point cloud minimizes error at center – Localize observation for better accuracy

22. Next Steps Continue pursuing Polaris accuracy & precision Observe motion of the Revolving Needle Driver (RND) End-Effector – Gets isocenter(s) of RCM point, EEF motion Use these to update kinematic model

23. Questions? – 2D – 3D XYZ AccuracyMean0.00250.01250.1036 (mm)Min0.00010.00080.0116 Max0.00780.02980.2315 PrecisionMean0.0484EuclideanDistance (mm)Min0.0314 Max0.0705 XYZ AccuracyMean0.01520.03490.1904 (mm)Min0.00060.00010.0017 Max0.03750.07370.3868 PrecisionMean0.0423EuclideanDistance (mm)Min0.0024 Max0.0737 Thank You!