Abstract: An automatic head retract system for a disk drive. The system operates in response to electric power turn off to retract the heads to a landing zone on the disk surface. The heads are retracted by operating a positioner motor under the control of logic internal to the disk drive unit without intervention by a host computer. The positioner motor comprises a multiphase DC brushless motor which, after power loss, is supplied with current from a capacitor charged during normal drive usage, and by the back EMF of a spindle motor. A latch mechanically locks the heads in the landing zone.

Abstract: An automatic head retract system for a disk drive is disclosed which operates in response to electric power turn off to retract the heads to a landing zone on the disk surface. The heads are retracted by operating a positioner motor under the control of logic internal to the disk drive unit without intervention by a host computer. The positioner motor comprises a multiphase DC brushless motor which, after power loss, is supplied with current from a capacitor charged during normal drive usage and by the back EMF of a spindle motor. A latch mechanically locks the heads in the landing zone.

Abstract: A capacitive position encoder which provides a digital output indication of the relative position between two plates. One of the plates includes first and second conductive input areas which are separated by a gap having the shape corresponding to a square wave. The second plate includes a number of rectangular output pads whose length is equal to one-half of the wavelength of the square wave. The pads are separated from one another by an integral fraction of the wavelength. Periodic input signals which are the inverse of one another are applied to the input areas and are capacitively coupled to the output pads. When the degree of overlap between an output pad and the input areas is equal, a null signal will be generated. Each pad will provide a null signal corresponding to a different position of the plates.

Abstract: A capacitive position encoder which provides a digital output indication of the relative position between two plates. One of the plates includes first and second conductive input areas which are separated by a gap having the shape corresponding to a square wave. The second plate includes a number of rectangular output pads whose length is equal to one-half of the wavelength of the square wave. The pads are separated from one another by an integral fraction of the wavelength. Periodic input signals which are the inverse of one another are applied to the input areas and are capacitively coupled to the output pads. When the degree of overlap between an output pad and the input areas is equal, a null signal will be generated. Each pad will provide a null signal corresponding to a different position of the plates.

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 closed loop control system for a stepper motor provides the necessary feedback to accurately control the position of a motor during acceleration, constant velocity and deceleration. Generation of commutation signals is based upon a monitoring of motor position to determine the points where commutation would result in maximum accelerating torque during acceleration and constant velocity and minimum braking torque during deceleration. These points indicate the earliest points at which commutation may occur. Commutation may be delayed in order to reduce the accelerating torque during acceleration and constant velocity or increase the braking torque during deceleration.

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.

Abstract: A chromosome detector using a scanning microscope system is used to detect the presence of a chromosome spread in a slide specimen and to produce a signal usable by the scanning microscope system to automatically operate the microscope system whereby the detected chromosomes are centered in the field of view, are automatically focused and their location converted to coordinate data which is stored in a memory system whereby the system may be used to re-examine the detected chromosome by the use of the stored X-Y coordinates. The detector performs an amplitude and frequency analysis of a cell find signal produced by a slide scanner in the scanning microscope system and produces, in turn, an output signal representative of a detected chromosome spread and compatible with the scanning microscope control circuit.

Abstract: An electronic tachometer utilizes a transducer, typically an optical encoder disc, connected to a movable mechanical element. The transducer produces a pair of triangular waves of fixed relative phase, each having slopes proportional to the velocity of the mechanical element. The triangular waves are differentiated and the resultant signals are sampled by gating pulses derived from the triangular waves themselves. The samples are combined to produce an output signal having a magnitude proportional to element speed and a polarity indicative of direction.In a combined system in which the transducer is attached to the shaft of a brushless motor, another output of the same transducer is used for commutation control of the motor stator windings. This arrangement is particularly useful in a velocity servo system, in which the tachometer output is compared with a signal indicating desired motor velocity. The comparator output is used to modify the commutation control so as to produce the desired motor velocity.