Abstract: A varistor disk assembly for mounting to a commutator base comprising a non-conductive retaining ring, a conductive member, and a varistor disk interposed between the commutator base and the distal end of the retaining ring. The retaining ring has an axial bore therethrough providing a friction fit with the motor shaft on which the commutator is mounted. A tolerance absorbing member can be interposed between the varistor disk and the retaining ring. The conductive member conducts current through its thickness from the commutator base to the varistor disk, but does not conduct current between adjacent commutator segments. To orient the varistor disk to the commutator, the proximal end of the retaining ring can have at least one planar side formed in its periphery for alignment with one of the commutator segments, while the distal end of the retaining ring also has formed in its periphery a planar side, and the varistor disk is provided with a complementary planar side in its inner diameter.

Abstract: A force transducer for a robotic arm comprises a plurality of axially-contractible cells. Each cell includes first and second end pieces which are interconnected by a pair of flexible connecting members. The connecting members are disposed on opposite sides of a longitudinal axis. The connecting members are deflected inwardly towards the longitudinal axis by a pair of electromagnets to cause a change in length of the transducer. The transducers can be used to impart movement robotic devices.

Abstract: A motor control apparatus is disclosed for controlling the rotational velocity of a drive shaft of an electric motor in accordance with a reference time period indicative of the desired rotational speed of the drive shaft. A sensor in the form of a tachometer provides a train of pulses. The period between tachometer pulses is measured and the difference between the reference and measured time periods is obtained. This difference is digitally processed by integrating, dividing and summing with a signal proportional to the difference to provide a motor command signal. The gains of the motor control apparatus are set to reduce phase delays and the deleterious effects thereof. Further, sensors in the form of Hall effect devices are disposed about the motor to each provide a train of timing signals. The timing signals are used to control the application of an energizing signal by corresponding switches to the motor coils; the level of the energization signal or current is set by the motor command signal.

Abstract: In a motor control system of the type having a plurality of transistors connected in series between a power supply and ground, a protection circuit is utilized to prevent the transistors from turning on simultaneously. The protection circuit introduces time delay into the turn on signals applied to the bases of the serially connected transistors, thereby preventing simultaneous operation and preventing excessive currents from damaging the transistors.

Abstract: In a brushless DC motor of the type having a control circuit and a plurality of position sensors, an error detector responsive to the position sensors is used to generate an error signal useful in shutting off the motor. The output signals of the position sensors provide a numerical code representative of the rotation of the rotor relative to the windings. When the numerical code deviates from a predetermined sequence, the error detector generates an error signal and the control circuit shuts off the motor.