FLEXURE-BASED MANIPULATOR FOR ACTIVE HANDHELD MICROSURGICAL INSTRUMENT
David Y. Choi and Cameron N. Riviere The Robotics Institute, Carnegie Mellon University, Pittsburgh, PA USA
Need for tremor compensation
Tremor characteristics
• Roughly sinusoidal, 8-12 Hz • 50 um p-p
Flexure-based manipulator
Male Luer connector Spherical flexure
Tasks difficult or impossible
• Removal or retinal membrane 20 μm thick • Intraocular cannulation of 100 um diameter vein
Cavity for piezoelectric stack
Revolute flexures
• Complexity: 1 part • Errors: free of backlash and friction less sensitive to manufacturing error no assembly
How Micron works
• Handheld instrument with active tremor compensation for vitreoretinal surgery
Visual feedback
• Cost: $60 – 1.5% of the former cost
Results
1.Motion Sensing Visuomotor control system
1 DOF Sinusoid Tracking rmse = 6.5 um
3 DOF Circle Tracking rmse = 12.1 um
Eye of patient
2.Estimation of erroneous motion
3. Manipulation of tip for active error compensation
Noisy, tremulous motion
Conventional manipulator infeasible
• Three-degree-of-freedom (DOF) • Parallel mechanism • Actuated by piezoelectric stacks
displacement (µm)
Handheld Result
60 30 0 -30 -60
uncompensated compensated
Total range: 52% reduction RMS amplitude: 47% reduction
• Complexity: >30 parts • Errors: machining, assembly larger than tremor • Cost: ~ $4000
Many parts of conventionally machined manipulator
0
1
2
3
time (s)
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SUPPORTED BY:
NIH (grant no. 1 R01 EB000526) NSF (grant no. EEC-9731748)