Contraves Goerz Corporation

Control Systems Research, Inc.

International Cybernetics Corp.

Contraves Gorez Corporation

Donald H Jones

Paul F McNally

Robert G Burig

Spencer W Allen

Philip R Chimes

The present invention provides a high response inexpensive microprocessor based control system. The system uses only one detector that detects only one motion characteristic of the object controlled by the system. In the preferred embodiment, the system controls the position and velocity of the movable member of the motor by creating commands that represent the desired position of the movable member 1024 times per second. The system also provides methods for improving the accuracy and precision of the system.

Sampled data servo control system with deadband compensation

Sampled data servo control system

The motor control system for an electric motor having no mechanical means integral therewith for commutating current provides the ability to control position, velocity and torque of such a motor to the degree achievable with DC motors having mechanical commutators. Such a result is achieved by maintaining a desired spatial relationship between the resultant magnetic field created by the stationary member and the movable member of the electric motor. The control system includes detecting apparatus for detecting parameters of the motor that dictate, in part, the desired spatial relationship within the motor and command apparatus for creating a motor command signal which, when generated in the motor, causes the desired spatial relationship to be established. The present invention also permits maintenance of an optimal spatial relation--a spatial relationship that causes the motor to produce desired torque with a minimum excitation.

Control system for electric motor

A power controller having a plurality of power output modules which can be added or removed as desired to change the power output rating. The electrical output of the individual power modules are removably attached to an output combining structure. The electrical connections to the output combining structure also provide mechanical support for the power output modules. The servo controller is constructed so that as additional power modules are added, each provides a predetermined proportion of the output power. That is, each module will add in a linear fashion to the total output capability of the amplifier. Load sharing among the modules is provided. An etched copper resistor having a positive resistance versus temperature characteristic is provided to aid load sharing among the output semiconductors. A feedback signal is derived from the power output modules to protect the servo controller. The protection of the power controller is one function of the feedback signal, in that, it limits the maximum current derivable from the controller under normal conditions. The primary function of the current feedback signal is to provide an error signal which when combined with the input command causes the current output to be properly metered to a load. The feedback signal can be obtained from only one of the output modules since load sharing is provided or can be obtained in several or all of the power output modules as desired. Temperature sensing of a representative module is provided for system protection.

Power controller with a modular power output

A speed detector, particularly useful on a permanent magnet DC motor, for providing a pulse indication from movement of the rotor teeth. During one revolution of the motor, a pulse is provided for each motor tooth. In a preferred embodiment, the pulse pickup probe is formed from a ferromagnetic stud which is anchored to the stator housing and extends through an opening formed in the center of the fixed permanent magnet to a position in close proximity to the rotor. The magnet through which the probe extends provides magnetic flux having a path through the stud and the rotor. The reluctance of the flux path through the rotor varies as a function of the alignment of a rotor tooth with respect to the ferromagnetic stud. The stud is formed to have a pickup end facing the rotor. The diameter of the pickup end is slightly greater than the rotor tooth width. A pickup coil is wound around a reduced diameter portion formed on the ferromagnetic stud, and generally lies within the opening through the permanent magnet. As a rotor tooth passes across the pickup end of the stud, a voltage pulse is induced in the pickup coil. The speed with which these voltage pulses are produced indicates motor speed. A small opening or openings extend from the head of the stud towards the reduced diameter portion for receiving leads which are connected to the pickup coil. A diode can be electrically connected to the pickup coil to produce a unidirectional pulse output.

Speed detector for use on a dc motor

A two-speed resolver system wherein the rotor of a fine brushless resolver which is directly connected to the shaft to be instrumented is connected to the rotor of a coarse resolver so that the rotor ofthe coarse brushless resolver rotates at a proportional but different rate than the fine resolver and the electrical output of the fine resolver which represents the position of the input shaft is fed to the electrical input on the coarse resolver and combined with the mechanical input to the coarse resolver to provide a signal out of the coarse resolver which indicates a predetermined fraction of angular rotation for each revolution of the rotor of the fine resolver. The disclosed two-speed resolver system utilizes brushless resolvers wherein the electrical connections to the rotors are through brushless rotary transformers. Two gears having a different number of teeth can be used to couple the rotor of the fine resolver to the rotor of the coarse resolver. The difference between the coarse resolver mechanical rotation and the fine resolver electrical output when subtracted by the coarse resolver determines the fractional rotation indicated by the coarse resolver for each revolution of the fine resolver rotor. The fine resolver is connected to provide sine and cosine representations of the mechanical angular input to its rotor. These sine and cosine angular indications can be fed to the stator windings or rotor windings on the coarse resolver and the coarse resolver can be connected to provide an output signal which represents the difference between the revolution of its rotor and the sine and cosine input from the fine resolver. This output can be made to indicate a predetermined number of degrees of rotation for each revolution of the input shaft.

Two-speed resolver employing differential reduction techniques

An absolute positioning servo for positioning a shaft in response to a digital command input which utilizes a resolver, for providing an analog position indication of the shaft, an analog to digital converter, which provides a digital indication of the shaft position, a comparator for comparing the digital command input signal with the digital indication signal and providing a differential digital error signal which is converted to an analog signal and fed back to position the shaft so that the differential digital error is 0. An analog fine control positioning means is provided which positions and maintains the shaft near the center point of the position represented by the digital command input signal when the digital differential error is 0. A signal representing the difference between the exact analog position of the shaft and the digital approximate position of the shaft is provided at the output of the translator. This is utilized to position the shaft within an angle equivalent of the least significant digital bit. The digital positioning system is utilized to move the shaft to a position within .+-. 1/2 bit of the desired position, then the analog positioning system takes over and positions and maintains the shaft within a lesser fractional portion of a bit to the absolute desired position. A short path positioning means is provided for selecting the shortest path to move the shaft to a new position indicated by the digital command input signal. That is, whenever the shaft is to be rotated to a position more than 180.degree. away, it is rotated in the opposite direction over an angle which then is necessarily less than 180.degree.. A square root function generator is provided following the digital to analog converter for the digital error signal which permits minimum positioning time for the servo system.

Servo system employing a tracking digital angle encoder

A method and apparatus for synchronizing the digitized position output of a multispeed system having overlapping position indications. The output of the multispeed position indicating system is a digital output word which is a combination of the individual outputs of the various transducers. For a two speed system a digital fine position having a high degree of accuracy is provided, and a digital coarse position indication of a lesser precision is also provided wherein the least significant coarse position digit overlaps the most significant fine position digit. An adjustment is provided for adjusting the coarse digital output as a function of the most significant digit of the fine transducer output so that nonambiguous synchronized position information is provided at all times. The appropriate adjustment can be obtained by adding a fixed number of counts, such as 5, to the coarse digital position indication and then subtracting the most significant digit of the fine position indication so that when the coarse position indication is combined with the fine position indication the desired unambiguous output results. The combined position indication can be obtained by utilizing all of the fine digital position outputs and the coarse digital outputs other than the least significant digit, which overlaps the most significant digit of the fine digital output. The coarse and fine position indicators can be resolvers which are connected to the shaft to be instrumented. The outputs of these resolvers are then converted to digital signals by analog to digital converters. The fine digital signal and the modified coarse digital signal are then combined by appropriate logic.

Synchronized multispeed transducer position indicating system

A transducer for combining an analog signal input and a digital signal input and providing an analog signal output, equal to the sum or difference, wherein the digital input signal is divided into a first component, for which a very accurate analog equivalent is provided and a second component for which a good approximate analog equivalent is provided. The translator is usually used in conjunction with a resolver which provides analog inputs in suppressed carrier trigonometric form. The translator performs certain trigonometric manipulations on the inputs from the resolver and the analog equivalents of the digital angle in order to obtain a signal proportional to the difference between the sensor resolver position and the digital angle command position. The first component of the digital angle, for which very precise analog equivalents are provided, uses a minimum number of high precision resistors. The outputs of the resolver are obtained, with appropriate sign changes when necessary, so that a few reference signals from high precision resistors can be used to determine the analog equivalent of the digital angle in one quadrant and by combining with the resolver outputs of the appropriate sign the value of the angle can be obtained for any quadrant. By proper selection of the signs for the trigonometric inputs from the resolver some of the analog equivalents of the digital inputs can even be obtained within the selected first quadrant. For example, if the analog equivalents of digital angles of 0.degree., 18.degree., and 36.degree. are obtained, the analog value of any angle which is a multiple of 18.degree. can be obtained with the selection of the proper sign. The second digital angle is fed to a voltage dividing network which is used to provide an analog approximation for the small digital angle. A programmable read only memory is provided for controlling switching and combining of the analog inputs, which are normally in sine and cosine form, and the analog equivalents of the digital inputs. By proper selection of the translator components and of the first large predetermined digital angle and the small digital angle, which is approximated in analog form, a translator output of any desired accuracy can be obtained.

Solid state translator

A tracking digital angle encoder utilizing a translator, for providing the difference between an analog angle input and a digital angle input, a counter, which feeds the digital angle input to the translator, a detector, which controls the counter and is connected to the output of the translator to be activated by the output of the translator exceeding a predetermined trigger value, all of which are connected to cause the counter to count to a position where the output of the translator is less than the predetermined trigger level. When the output of the translator is less than the predetermined trigger value, the output of the counter provides a digital signal which closely approximates the analog angle input to the translator. A balanced demodulator which is connected to the output of the translator and receives a signal from a reference oscillator, which is equal to the carrier frequency, provides a pure sine function output representing the difference between the analog and digital inputs to the translator. An adjustment is provided between the counter and the threshold detector which permits the level at which the threshold detector activates the counter to be varied and thus the angle, to which each bit of the counter is equivalent, can be varied. This adjustment allows easy compensation for errors due to mechanical tolerances or mechanical wear in the system being controlled. The translator also provides an output which is equivalent to the cosine of the analog angle input. This cosine output is utilized for switching the counter to its midpoint when the power is first applied if the cosine value is negative, indicating the angular position of the analog signal is in the second or third quadrant.

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Pittsburgh, PA, United States of America

Donald H Jones