# US 4,882,528 A · Digital servo system

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- Number: US 4,882,528 A
- Document ID: US4882528A
- Status: Granted
- Kind: A
- Application number: 07/233,644
- Filed: 1988-07-08
- Granted: 1989-11-21
- Earliest claimed: 1986-11-08
- Assignees: Fanuc Corporation
- Inventors: Masatoyo Sogabe; Kanemasa Okuda; Keiji Sakamoto; Shunsuke Matsubara
- Web page: https://patentgrep.com/patent/US4882528A

## CPC

- G05B 19/19: characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
- G05B 19/232: {with speed feedback only}
- G05B 2219/41029: Adjust gain as function of position error and position
- G05B 2219/41121: Eliminating oscillations, hunting motor, actuator
- G05B 2219/42093: Position and current, torque control loop
- G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G)

## Abstract

A digital servor system can swiftly stop a moving object, having a small friction resistance to the motion, at the position where the object should stop, without vibration thereof. A velocity command generating device (3) calculates a velocity command (V.sub.cmd) based on the deviation value of a position fedback from a position command detected by a position deviation detecting device (2). A velocity deviation detecting device (5) calculates a deviation (E) of a velocity fedback from the velocity command (V.sub.cmd). A torque command generating device (6) calculates a torque command (T.sub.cmd) giving a delay processing to the deviation (E), and outputs the torque command (T.sub.cmd) to a motor driving means (7).

## Claims

### Claim 1

A digital servo system comprising:
a position detecting means for detecting an actual position of an object;
a position deviation detecting means for detecting and for outputting a deviation of the actual position of the object from a predetermined position by a command;
a velocity command generating means for outputting a velocity command to move the object according to the output of the position deviation detecting means;
a velocity detecting means for detecting an actual velocity of the object;
a velocity deviation detecting means for detecting and for outputting a deviation of the actual velocity of the object from the velocity command;
a torque command generating means for outputting a torque command to drive a motor according to the output of the velocity deviation detecting means wherein the torque command increases according to a non-zero output of the velocity deviation detecting means up to a predetermined saturation value, and the torque command decreases swiftly down to zero at the time that the output of the velocity deviation detecting means becomes zero; and
a motor driving means for moving the object according to the torque command.

### Claim 2 (depends on 1)

A digital servo system according to claim 1 wherein n=1, 2 . . . , T.sub.cmd (t) is a torque command value at a time t which is output from said torque command generating means, E(t) is an output of said velocity deviation detecting means at the time t, K.sub.1 is a gain constant, r is a constant which satisfies 0<r<1; .tau. is a clock cycle time, and E.sub.n is the value of E(t) at the time t=n.tau.; said torque command T.sub.cmd (t) is renewed to T.sub.cmd n at the time t=n.tau., where
T.sub.cmd n =r }T.sub.cmd n-1 +K.sub.1 .sub.n },
and T.sub.cmd( 0)=T.sub.cmd 0 =0.