# A Novel Rolling Driving Principle-Enabled Linear Actuator for Bidirectional Smooth Motion

## TL;DR

A new linear actuator design inspired by rack-and-pinion mechanisms achieves smooth bidirectional motion with high consistency and linearity.

## Contribution

A novel rolling driving principle (RDP) for stick-slip actuators is introduced, enabling pure rolling motion with a single PZT and consistent bidirectional performance.

## Key findings

- The RDP-based actuator achieves forward and reverse speeds of 0.410 and 0.417 mm/s at 10 Hz with high linearity.
- At 560 Hz, the actuator reaches 37.73 and 34.99 mm/s with velocity difference ratios of 1.96% and 7.54%.
- An MRI-compatible microsurgical instrument based on the RDP actuator was prototyped for intraoperative use.

## Abstract

This work presents a novel rolling driving principle (RDP) for stick-slip actuators to achieve high motion consistency, inspired by the rack-and-pinion mechanism. This RDP utilizes a symmetrical driving structure and tangential contact to realize the pure rolling motion between the stator and the slider, requiring just a single lead zirconate titanate (PZT). This configuration ensures a consistent bidirectional driving process with a constant contact force, which improves both motion consistency and linearity. Based on this RDP principle, a linear stick-slip actuator incorporating an isosceles trapezoidal flexible mechanism (ITFM) has been implemented. The corresponding driving principle, operating principle, and the RDP’s advantages have been analyzed and revealed. Design optimization was performed to investigate the optimal structural parameters of the ITFM. The superior performance of the proposed RDP-type actuator was experimentally verified across both high- and low-frequency ranges. The results indicate that the presented design exhibits forward and reverse output speed values of 0.410 and 0.417 mm/s at 10 Hz with linear correlation coefficients of 0.99969 and 0.99962, indicating an excellent motion consistency with a velocity difference ratio of 1.96%. When working at 560 Hz, the presented actuator reaches 37.73 and 34.99 mm/s for the forward and reverse output speed, yielding high linearity values of 0.99999 and 0.99999 due to the tiny speed fluctuation, and maintains a reasonable motion consistency with a velocity difference ratio of 7.54%. Finally, an RDP-type actuator-based magnetic resonance imaging (MRI)-compatible microsurgical instrument was proposed and prototyped, which enables opening–closing motions and cutting motions for intraoperative MRI surgical applications.