An Opposed Piston Driving Pneumatic Stepper Motor for MR Intervention Robotics

Magnetic resonance (MR) safe robots offer many advantages to robot-assisted surgeries in the magnetic resonance imaging (MRI) environment. As one of the key components, the design of actuators that work in the MR environment is critical for MR safe robots. This article proposed a new piston motor powered by compressed air for MR safe robots, in which the working principle is investigated, and the dynamic model is analyzed. Linear motion is achieved by applying the lead screw transmission. Experiments demonstrate that the rotary motor has a maximum speed of 800 r/min and maximum output torque of 132 mN·m, and the linear motor has an output force of 50 N, both at a speed of 2 steps/s. The step response and error analysis are also conducted. MR tests show that there are no obvious image artifacts caused by the motor.