Abstract: A motor control system for a high accuracy incremental motion system such as a paper feed system in a high speed printer. The system utilizes a stepping motor which is driven in one of two modes, depending upon its position. During most of the movement from one position to another, the motor is driven as a DC brushless motor. This is accomplished by commutating the phases of the motor so that they are energized around the peaks of their torque curves. The motor is driven in a closed loop fashion, with velocity commands being generated by a velocity profile generator incorporating a microprocessor. Both position and velocity feedback are utilized. Since the motor is driven as a DC brushless motor, traditional control theory methods (e.g., Root locus, Bode, etc.) can be employed.As the motor nears the final desired position, the system switches so that the motor is energized as a step motor.

Abstract: A digitizer for receiving sine and cosine encoder signals and providing a digital output representative of the phase angle of the encoder. A counter is used to generate a variable reference angle, and memories are used to generate digital signals representing the sine and cosine of the output of the counter. These signals are multiplied by the analog cosine and sine inputs, respectively, in order to determine the direction of the difference between the encoder phase angle and the counter angle. The counter is incremented or decremented so as to make the digital angle output provided by the counter equal to the phase angle of the encoder. A velocity indication may be provided by the addition of a low pass filter to the circuit.

Abstract: A capacitive encoder utilizing a stationary plate having transmitter elements and receiver elements located on the surface thereof and a moving plate having two conductive areas separated by a sine wave shaped gap. The receiver elements on the stationary plate overlie the gap and provide outputs which vary as a function of the position of the gap with respect to the output elements. Signals from the output elements are differentially amplified and demodulated in order to provide precise sine and cosine outputs, the accuracy of which are unaffected by variations in the input signal.

Abstract: A magnetic print module for use as a printhead of a magnetic printing system. The print module comprises a base having a matrix of integral protrusions extending upward from the base and a plurality of coils wrapped around the base between the rows and columns of the matrix. By selectively energizing four coils at a time, a current path may be formed around one of the protrusions, which induces a magnetic field in the protrusion and permits it to print a dot in a recording medium. In order to form a printhead with minimal spacing between print positions, a matrix having a plurality of print rows may be formed and the matrix skewed with respect to the path of the recording medium.