Dual-Speed MR Safe Pneumatic Stepper Motors

Abstract

In breast cancer detection it is essential to perform precise interventions to determine the diagnosis. Robotic systems actuated by MR safe pneumatic stepper motors could improve accuracy to target the tumor. The achievable accuracy or speed is limited due to long pneumatic tubes connecting the motors to the electromagnetic valves in the control room. This paper presents the design of two dual-speed stepper motors in order to solve this limitation. The linear motor measures 50x32x14 mm (excluding racks) and has step sizes 1.7 mm and 0.3 mm. The maximum speed under load is 20 mm/s, measured force is 24 N and positioning accuracy is 0.1 mm. The rotational motor measures ⌀30x32 mm (excluding axles) and has step sizes 10°and 12.9°. Under load its maximum angular speed is 229 °/s or 38.2 RPM, maximum torque is 74 N mm and positioning accuracy is 1°. By operating the valves in a coordinated way high-speed and precise position control can be achieved. With these specifications the motors have high potential to actuate MR safe surgical robots.