Abstract: A brushless sensorless DC motor assembly computes rotor position by examining the current measurements of the stator windings. The brushless DC motor assembly includes a rotor and a set of stator windings that are adapted to drive the rotor. In addition, a power amplifier is adapted to apply a voltage to each stator winding in sequence according to a received sequence of switching signals. Also included is a terminal that is adapted to receive a commanded rotor stopping position from a user input device or a controlling computer. A current sensing assembly permits the determination of the current through each stator coil to produce a sequence of stator coil current values over time. A data processor is adapted to calculate the sequence of switching signals based on the received commanded rotor position and the computed rotor position. The calculation of the computed rotor position is based on the most recent set of stator coil current values and the most recent set of the computed switching signals.

Abstract: A control device for converting a manual input into an electrical signal is provided. The control device includes a control button, a first magnet having a first predetermined polarity, a second magnet having a second predetermined polarity, and a hall-effect sensor located adjacent to the control button. The control button is mounted for pivotal displacement about a neutral position in accordance with the manual input. The first magnet and the second magnet are mounted to the control button. The polarity of the second magnet is opposite the polarity of the first magnet. The hall-effect sensor has an electrical input and an electrical output. The electrical signal produced by the control device may, for example, be used to control the velocity of a motor, which rotates an ultrasound transducer.

Abstract: A motor control circuit for a switched reluctance motor which includes a rotor and a plurality of stator coils, and a driver circuit for energizing the coils in sequence, includes a current sensing resistor for detecting a signal proportional to the current in the coils and a slope detector for detecting the rate of change of the current signal with respect to time over predetermined time intervals during which the voltage in the coils is dominated by a term representing back EMF. A variable oscillator is responsive to an integrated output of the slope detector for generating a timing signal for the driver circuit. When the voltage across the coils is dominated by the back EMF term, the current should be substantially constant, but when the rotor is out of phase with the driver circuit, the current signal during this time has a substantially linear slope which is either positive or negative depending upon whether the rotor is leading or lagging the driver circuit.