Abstract: A drive circuit for a brushless motor utilizing both phase shift and current shaping to provide for efficient operation of a brushless motor in a servo control system. The circuit includes circuitry for altering the phase of the drive signal as a function of motor velocity to compensate for increased current phase lag due to inductance of the motor at high commutation frequencies corresponding to high motor velocities. In addition to altering the phase shift of the drive signal, the circuitry also alters the commutation signal waveform to compensate for a non-sinusoidal field distribution to produce a nearly sinusoidal torque from each of the brushless motor windings. The compensation of both phase shift and commutation signal waveform is accomplished using digital circuitry. The phase commutation is a non-linear function of motor velocity. The waveform compensation is selected to compensate for a trapezoidal magnetic field distribution in the motor air gap.

Abstract: A motor compensation network for use with a two-degree of freedom velocity servo controller includes first and second compensation means. The first compensation means receives a signal representing a difference between a velocity command signal and a velocity feedback signal and provides a modified output signal. The second compensation means receives the velocity feedback signal and provides a modified output signal. Bandwidth adjustment means are coupled to the first and second compensation means. Damping factor adjustment means are coupled to the second compensation means. The transfer function of the first compensation means has characteristics of an integrator. The transfer function of the second compensation means has a first and a second component. The first component has characteristics of a differentiator, while the second component has characteristics of a proportionality or a gain constant.

Abstract: An optical shaft angle encoder which provides sensor output voltages having waveform characteristics modified for use with "multiplication type" tachometer converter circuits to provide improved servo control system performance by reducing step changes in the tachometer output voltage due to phase error and reducing tachometer output voltage ripple. The geometry of the encoder mask combination provides a non-sinusoidal sensor output voltage comprised of linear and parabolic segments having a trapezoidal derivative.

Abstract: A DC motor utilizing flux focussing pole pieces and non-ferrous spacers to wedge the pole pieces and magnets into contact with the motor housing. Cooling is provided with heat pipes mounted in the spacers or pole pieces and/or the motor armature.

Abstract: A modular encoder with a dimensionally stable housing which can be easily aligned for mounting on a motor housing. The encoder utilizes a monolithic, in-line, sensor array and a single light source to achieve improved long-term performance and includes improved alignment means permitting a user to readily align the encoder with a motor. Pre-alignment of the mask and sensor assembly simplifies the alignment performed by the user.

Abstract: A closed control system for controlling the operation of a multiple horsepower brushless direct current motor wherein a current feedback signal representative of the effective motor drive current is constructed from the instantaneous currents flowing in the stator windings. Protective circuitry is provided to shutdown the output power stages in the event of component failures to prevent catastrophic failure of other components in the system.

Abstract: A modular encoder with a dimensionally stable housing which can be easily aligned for mounting on a motor housing. The encoder utilizes a monolithic, in-line, sensor array and a single light source to achieve improved long-term performance and includes improved alignment means permitting a user to readily align the encoder with a motor. Pre-alignment of the mask and sensor assembly simplifies the alignment performed by the user.

Abstract: A brushless tachometer utilizing four stator windings and series connected field effect transistor commutation switches to provide an input to a summing amplifier. Connection of the field effect transistor switches to the summing junction of the amplifier and use of series resistance and back-to-back clamping diodes on the winding side of the field effect transistors permits commutation switching with a minimum of transient voltage changes due to interruption of the stator winding current.

Abstract: A Hall effect shaft angle position encoder is constructed using a plurality of magnetic elements independent of any magnetic rotor of the electrical device which may be a brushless motor or brushless tachometer. The plurality of magnetic elements has serially alternating polarities of magnetic north and south with at least one Hall effect sensor mounted in spaced and confronting relation with the magnetic elements for sensing the alternating polarities and producing output signals representative of the magnetic polarities where the signals include a ramp voltage passing through zero value. The magnetic elements are secured to the rotor outside the normal rotor elements of the device.

Abstract: A pulse width modulated motor control system in which the power supplies for forward and reverse operation for the motor are provided to supply electric energy at different levels. The control signals for the motor are provided in such a manner that the average energy of unbalanced pulse periods is the same, but the potential level differs by a substantial amount. Energy storage may be provided for in conjunction with the lesser of the two power supplies to assist in a rapid reversal, stop or shaft positioning of the motor.