Manipulator Design and Operation of a Six-Degree-of-Freedom Handheld Tremor-Canceling Microsurgical Instrument

Abstract

This paper presents the design and actuation of a six-degree-of-freedom (6-DOF) manipulator for a handheld instrument, known as “Micron,” which performs active tremor compensation during microsurgery. The design incorporates a Gough-Stewart platform based on piezoelectric linear motor, with a specified minimum workspace of a cylinder 4 mm long and 4 mm in diameter at the end-effector. Given the stall force of the motors and the loading typically encountered in vitreoretinal microsurgery, the dimensions of the manipulator are optimized to tolerate a transverse load of 0.2 N on a remote center of motion near the midpoint of the tool shaft. The optimization yields a base diameter of 23 mm and a height of 37 mm. The fully handheld instrument includes a custom-built optical tracking system for control feedback, and an ergonomic housing to serve as a handle. The manipulation performance was investigated in both clamped and handheld conditions. In positioning experiments with varying side loads, the manipulator tolerates side load up to 0.25 N while tracking a sinusoidal target trajectory with less than 20 μm error. Physiological hand tremor is reduced by about 90% in a pointing task, and error less than 25 μm is achieved in handheld circle-tracing.

Comparative Evaluation of Handheld Robot-Aided Intraocular Laser Surgery

“…Micron, presented in Fig. 1(b), incorporates a miniature micromanipulator that provides 6-DOF actuation of an end-effector within a cylindrical workspace 4 mm in diameter and 4 mm high [8]. It thus allows for a remote center of motion (RCM) at the point of entry through the sclera.…”

Piezoelectric Motors, an Overview

“…As systems in medical and micro robotic fields requiring more complex and multi-tasking actuations, the need for these motors would be in demand [77,[93][94][95][96]. Research on more reliable friction contact materials, non-lead piezoelectric materials, and making motors to operate at lower voltage with improved driving voltage-speed non-linearity can create advantages for finding new applications.…”

Haptics in Robot-Assisted Surgery: Challenges and Benefits

“…It must be noted however, that providing direct force feedback is not the only approach taken by researchers for reducing applied force in retinal membrane peeling. In [140] for example, an active handheld micromanipulator [141] is implemented under a hybrid position/force control schema that is shown to reduce the maximum force by more than 50% in experiments on both artificial and animal models. Table III, summarizes the research studies that have investigated the effects of haptic feedback in robot-assisted surgery.…”