Characterization and Control of a Pneumatic Motor for MR-Conditional Robotic Applications

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Abstract
Magnetic resonance (MR)-guided interventional robots have recently been developed for a variety of surgeries, such as biopsy, ablation, and brachytherapy. The actuators and encoders that power and track such robots must be MR conditional. In this paper, we propose an MR-conditional pneumatic motor with an integrated and custom-built fiber-optical encoder that provides powerful and accurate actuation. The motor is coupled with a modular plastic gearbox that provides a variety of gear ratio options so that the motor can be adapted to application requirements. With a 100:1 gear reduction at 0.55 MPa, the motor achieves 460 mN:m stall torque and 370 r/min no-load speed, which leads to the peak output power of 6 W. The motor has the bandwidth of approximately 1.1 and 3.5 Hz when connected to 8 and 0.2 m air hoses, respectively. The motor was tested in a 3T magnetic resonance imaging (MRI) scanner. No image artifact was observed and maximum signal-to-noise ratio (SNR) variation was less than 5%. Different from most of the existing MR-conditional pneumatic actuators, the proposed motor shape is more like the traditional electric motors, which offers more flexibility in the MR-conditional robot design.
Funding Information
  • National Institute of Health (1R21NS091735-01)

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