Abstract: Methods and apparatus for controlling a polyphase motor in implantable medical device applications are provided. In one embodiment, the polyphase motor is a brushless DC motor. The back emf of a selected phase of the motor is sampled while a drive voltage or the selected phase is substantially zero. Various embodiments utilize sinusoidal or trapezoidal drive voltages. The sampled back emf provides an error signal indicative of the positional error of the rotor. In one embodiment, the sampled back emf is normalized with respect to a commanded angular velocity of the rotor to provide an error signal proportional only to the positional error of the motor rotor. The error signal is provided as feedback to control a frequency of the drive voltage. A speed control generates a speed control signal corresponding to a difference between a commanded angular velocity and an angular velocity inferred from the frequency of the drive voltage.

Abstract: Methods and apparatus for controlling a polyphase motor in implantable medical device applications are provided. In one embodiment, the polyphase motor is a brushless DC motor. The back emf of a selected phase of the motor is sampled while a drive voltage of the selected phase is substantially zero. Various embodiments utilize sinusoidal or trapezoidal drive voltages. The sampled back emf provides an error signal indicative of the positional error of the rotor. In one embodiment, the sampled back emf is normalized with respect to a commanded angular velocity of the rotor to provide an error signal proportional only to the positional error of the motor rotor. The error signal is provided as feedback to control a frequency of the drive voltage. A speed control generates a speed control signal corresponding to a difference between a commanded angular velocity and an angular velocity inferred from the frequency of the drive voltage.

Abstract: A power system for an implantable heart pump is provided. The system includes two batteries, a microprocessor controller, two motor drivers, a multiplexer, two stators and a TET coil. During normal operation, only one battery and one motor driver are in use at a time to drive both stators.

Abstract: A power system for an implantable heart pump is provided. The system includes two batteries, a microprocessor controller, two motor drivers, a multiplexer, two stators and a TET coil. During normal operation, only one battery and one motor driver are in use at a time to drive both stators.

Abstract: A moving magnet electromagnetic motor wherein the moving magnet is attached to, and moves integrally with, the back iron flux return path portion. The preferred embodiment utilizes a two-pole fixed stator with an energizing coil wrapped about each pole. However, the present invention is applicable to motors with any number of stator pole pieces and energizing coils. Current applied to the energizing coil or coils create a magnetic field which propels the moving magnet and moving back iron combination. The invention is ideal for use as a disc drive read/write head positioning actuator. The invention provides a positioner of reduced size. In addition, the moving magnet and back iron structure doubles as a counterweight to the head structure which simplifies and reduces the size of the disc drive. A further improvement upon the current invention involves embedding the permanent magnet into the back iron flux return path portion, such that the two pieces are substantially coplanar.

Abstract: A closed-loop voltage feedback system and method for control of the step response of a multiple-phase step motor, wherein the rotor oscillation amplitude is smaller than the period of the back emf voltage waveform, achieving minimization of the step response ringout time. Thus, when used in computer memory disc drives, the present invention provides faster data acquisition by reducing settling time and seek time. The claimed method includes steps for sampling the back emf voltage induced across an open phase winding, producing a continuous feedback signal proportional to the velocity of the step motor, and applying the continuous feedback signal to an energized phase winding to produce damping. The method may also be used in conjunction with open or closed loop position feedback for microstepping the motor to nondetent positions. The present invention eliminates the need for external sensors or an extensive amount of electronics.

Abstract: The output of the ring detector is used to change or control the timing of specially generated torque damping pulses which are fed to the stepper motor at the end of a SEEK step sequence. These torque damping pulses are step pulses, the timing, amplitude and/or duration of which applies either a positive or negative torque to the stepper motor relative to the target track based on the "energy" that has to be dissipated to settle the read/write head over the desired track. The energy is measured indirectly by monitoring the back emf voltage of an open winding or unenergized phase of the motor, and developing an indication of how fast the read/write head is going through the desired track center or target track point. By bringing an additional signal out of the ring detector, the direction in which the read/write head has crossed the track can also be defined.

Abstract: A motor is disclosed comprising a housing and a plurality of parallel stator laminations mounted on the interior wall of the housing surrounding the rotor. The stator comprises a plurality of coils wound around the stator poles. Each coil or group of coils connected in series with each other are further connected in series with a thermistor network. Preferably, the thermistor is supported on a printed circuit board mounted adjacent to the coils, with the thermistor being inserted in a space directly adjacent to or between adjacent stator coils in order for the thermistor to accurately respond to the actual operating temperature of the coils. With increases in temperature, the resistance of the negative temperature coefficient thermistor will decrease, lowering the resistance of the motor circuit and maintaining the L/R time constant of the system. The opposite effect will occur with decreasing tempreature.