The disclosed system utilizes digital electronic programming to establish the rotational or translational speed of a motor driven member. The desired speed can be selected by manipulating a set of digital switches. A stable oscillator is employed to generate a high frequency signal which is processed by frequency dividers to produce a modulaton frequency signal. The modulation frequency is supplied to an optical encoder having a rotary shaft adapted to be connected to a rotary member, the speed of which is to be controlled. The encoder is constructed and arranged to produce a phase variable output signal at the modulation frequency, the phase of such output signal being variable as a function of the shaft angle. The high frequency signal is also processed by digital circuits under the control of the digital selector switches to produce a variable reference frequency signal having a frequency corresponding to the modulation frequency plus or minus a number which is established by the setting of the selector switches. The speed control system includes means for comparing the frequency of the phase variable signal with the frequency of the reference signal. This comparison circuit controls a motor operating circuit which increases or decreases the speed of the drive motor for the rotary member, until the phase variable signal has the same frequency and phase as the reference signal. The digital generation of the reference frequency signal insures that its frequency is established and maintained with an extremely high degree of accuracy.
An object of the present invention is realizing a highly accurate synchronous control device which does not cause time lag by detecting the rotational frequency and phase simultaneously perpetually by same signal in the synchronous control of plural electric motors. The synchronous control device synchronizes accurately rotational frequency and rotation phase of an electric motor or a machine axis driven by the electric motor. A master section outputs phase signals or frequency signals based on rotational frequency reference. On the other hand, a slave section detects master rotational frequency setting signals and master phase setting signals simultaneously and perpetually by using the phase signals or frequency signals from the master section, and detects rotational frequency feedback signals and phase feedback signals simultaneously and perpetually based on output of a rotary encoder attached to an electric motor or connected to an machine axis driven by the electric motor, then detects phase deviation perpetually out of the master phase setting signals and the phase feedback signals. The electric motor of the slave section or the machine axis driven thereby is synchronously controlled based on the phase deviation, said master rotational frequency setting signals and said rotational frequency feedback signals. Also, the master section may provide a control device for controlling the electric motor, and a means for sending frequency signals outputted from a rotary encoder attached to the electric motor or a rotary encoder connected to an machine axis driven by the electric motor to the slave section.
A detector circuit for detecting a phase or frequency error of an input signal. One mode of at least two detection modes is selected according to a phase or a frequency of the input signal with each mode having a reference value of a phase or a frequency of the input signal and reference values of the detection modes being different from each other. A pulse signal having a phase corresponding to a difference between an actual phase or frequency of the input signal and the reference value of the phase or the frequency is generated, and a predetermined carrier signal is pulse width modulated with a predetermined modulation factor in response to the pulse signal, the modulation factor being different for each detection mode.
A motor speed control apparatus includes a motor, a frequency generator for generating a detective frequency signal, the frequency of which is proportional to the motor speed, and a control signal generator. A rotational speed-error pulse train is produced by the control signal generator and is used for improving the load characteristics of the motor. The rotational speed of the motor is maintained constant at a predetermined speed, which is proportional to the reference frequency, for any load torque, the motor speed is not influenced by ambient temperature changes or long term characteristic variations of the electronic components utilized. Furthermore, the transient response of the motor is fast and the motor starts rotating smoothly and stably.
A frequency/speed controller is provided for controlling the frequency or speed of a device by comparing the frequency of the device to a known reference frequency and matching the device frequency with the reference frequency. The controller uses an up/down counter whose count at any given time is the digital quantized form of ##EQU1## where f.sub.1 and f.sub.2 are the frequencies to be matched.
A cyclically operating electrically or hydraulically powered unit, is provided with a control assembly comprising a partially digital control loop formed by a sensor responsive to the powered unit for the production of pulses at a multiple of the frequency thereof, a reversible counter having a count-up input receiving a control signal and a count-down input receiving a signal derived from the sensor and a digital-to-analog converter connected to the reversible counter to detect it state and supply a control signal to the powered unit.
