Contraves Goerz Corporation

Control Systems Research, Inc.

Robert G Burig

Paul F McNally

Donald H Jones

Apparatus for generating synchronized multi-axis intermittent motion utilizing electronic encoding, memory and a position control system having feed-forward control. A plurality of slave shafts are rapidly and accurately positioned in response to the positioning of a rotatable master shaft, without mechanical interconnections therebetween. An analog transducer is attached to the master shaft providing an analog position output which is fed to a master encoder which feeds a digital output to a plurality of independent digital memory devices. Each digital memory device provides, in response, an output digital signal indicative of the desired position of an associated slave shaft. The output of each memory device, through an appropriate digital-to-analog converter, is fed to a position controller which positions the associated slave shaft as desired. The servo controller includes a feedforward input to speed positioning and reduce system lag. The feedforward velocity signal is obtained by calculating the difference between the present position of the associated slave shaft and the desired future position of the slave shaft to obtain the desired change in the slave shaft position. This difference is multiplied by the absolute value of the master axis velocity to obtain the necessary velocity feedforward signal. The velocity feedforward signal, which is a function of the change in slave shaft position and the velocity of the master shaft represents the velocity at which the slave shaft must be rotated to achieve the desired position while the master shaft moves through one digital increment.

Multi-axis motion generator utilizing feedforward control

Apparatus for generating synchronized multi-axis intermittent motion utilizing electronic encoding, memory and a servo controlled positioning system. A plurality of mechanically independent slave shafts are positioned in response to the position of a rotatable master shaft. An analog transducer is attached to the master shaft providing an analog output signal which is fed through an analog-to-digital converter. A digital representation of the master shaft position is provided by the analog-to-digital converter. The digital indication of master shaft position is fed to a plurality of independent digital memory devices each of which provides, in response, a digital position signal indicative of the desired position of an associated slave shaft. The output of each independent digital memory device is fed to a digital-to-analog converter which provides an analog output representative of the desired slave shaft position. A servo controller positions the associated slave shaft in response to the analog signal. A translator can be utilized for combining the digital output of each memory with an analog position signal from a position transducer connected to the associated slave shaft and providing an analog difference or error signal which can be utilized for proper positioning of the slave shaft. A tachometer can be utilized in the slave shaft servo for providing speed feedback information. Other means for speed feedback can be employed either by deriving a speed signal from other parameters, related to speed, or by utilizing the characteristics of the prime mover itself for speed feedback.

Multi-axis electronic motion generator

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 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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Allison Park, PA, United States of America

Robert G Burig