Abstract: An electric motor has three windings which are supplied by a three-phase source of electricity that has one polarity during a first half-cycle and another polarity during a second half-cycle. The motor is controlled by an apparatus that has three thyristor switches coupling the phases of the source to the motor windings. A switch controller triggers the thyristor switches to apply electricity that produces movement of the motor. One thyristor switch is operated to be in a first non-conductive state during a portion of every first half-cycle and in a second non-conductive state during a portion of every second half-cycle. The first non-conductive states are longer in duration than the second non-conductive states. A current sensor provides a first value that indicates the magnitude of the DC component of electric current flowing through one motor winding that is connected to the one switch.

Abstract: A bar code reader of the type which directs a light beam to scan an area (i.e. raster scan) is disclosed herein. The reader includes first and second oscillating mirrors for directing a light beam from a photodiode to a bar code, and for directing portions of the light beam reflected from the bar code back to a photodetector which generates an electrical signal representative of the information embodied in the bar code. The first oscillating mirror scans the light parallel to a first line (e.g. vertical line) at a first frequency onto the second oscillating mirror. The second oscillating mirror scans the light from the first mirror parallel to a second line (e.g. horizontal line perpendicular to the vertical line) at a second frequency greater than the first frequency onto the bar code. The first mirror may be a compound mirror having a concave, reflective surface which circumscribes a flat, reflective surface.

Abstract: A non-invasive system for accurately determining the stator resistance in an electric motor during motor operation. The system includes a mechanism for determining the phase angle of the stator current within the dq frame of reference and a mechanism for transforming feedback voltages into a new frame of reference defined by this phase angle. Counter EMFs are detected which are free of stator resistance and used to force the counter EMF components of the stator winding voltages to conform to desired values. The stator resistance is then derived using simple mathematical relationships between the resistance, stator current, feedback voltage and known counter EMF values.

Abstract: A programmable controller for executing general instructions and relay ladder instructions employs a general purpose microprocessor together with a high speed relay ladder processor. The relay ladder instruction in a user program are executed by the special processor exclusively. When a general instruction is encountered, the special processor releases the general purpose microprocessor from a wait state and provides it with data in response to a previous long read instruction. This data is interpreted by the microprocessor to indicate the next instruction to be executed and points to a series of machine instructions terminating in another long read instruction to a designated address. When a read of this designated address is detected by the special processor, thus indicating the conclusion of the execution of the general instruction, the special processor puts the microprocessor back in the wait state and continues to execute relay ladder instructions in the user program if any.

Abstract: A motor control system and the electrical bus for interconnecting the components of the control system are disclosed herein. The system includes a main motor control unit connected to four motor axis control modules. The control algorithms and commands for the system are stored and executed by the control unit which communicates control commands to the individual motor axis control modules. Each motor control module processes the control commands to control a motor connected to the module, and also communicates feedback signals produced at the associated axis to the control unit. The interconnection between the control unit and the modules is positioned at the face of the components to facilitate removal and insertion of the modules. The electrical bus includes both communications conductors and power conductors, and is included in the interconnection of the components.