A. Hardware Architecture The PiezoMotor actuators (Uppsala, Sweden) chosen are non-harmonic piezoelectric motors, which have two advan-tages over a harmonic drive: the noise caused by the driving wave is much easier to suppress, and the motion produced by the motors is generally at a more desirable speed and torque.
Optical encoders (US Digital, Vancouver, Washington) have been thoroughly tested in a 3T MRI scanner with satisfactory performance