Achieving Commutation Control of an MRI-powered Robot Actuator



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IEEE Transactions on Robotics


Actuators that are powered, imaged, and controlled by magnetic resonance (MR) scanners could inexpensively provide wireless control of MR-guided robots. Similar to traditional electric motors, the MR scanner acts as the stator and generates propulsive torques on an actuator rotor containing one or more ferrous particles. Generating maximum motor torque while avoiding instabilities and slippage requires closed-loop control of the electromagnetic field gradients, i.e., commutation. Accurately estimating the position and velocity of the rotor is essential for high-speed control, which is a challenge due to the low refresh rate and high latency associated with MR signal acquisition. This paper proposes and demonstrates a method for closed-loop commutation based on interleaving pulse sequences for rotor imaging and rotor propulsion. This approach is shown to increase motor torque and velocity, eliminate rotor slip, and enable regulation of rotor angle. Experiments with a closed-loop MR imaging actuator produced a maximum force of 9.4 N.



Rotors, Magnetic resonance imaging, Actuators, Radio frequency, Commutation, Torque


Copyright 2015 IEEE Transactions on Robotics. This is a post-print version of a published paper that is available at: Recommended citation: Felfoul, Ouajdi, Aaron Becker, Christos Bergeles, and Pierre E. Dupont. "Achieving commutation control of an MRI-powered robot actuator." IEEE Transactions on Robotics 31, no. 2 (2015): 387-399. DOI: 10.1109/TRO.2015.2407795 This item has been deposited in accordance with publisher copyright and licensing terms and with the author’s permission.