US 5,448,145 AGranted

Feedforward control method for a servomotor

AssigneeFanuc Corporation

InventorYasusuke Iwashita

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Abstract

A feedforward control method for a servomotor designed to improve with the command follow-up property of a servo system. In this method, the average value of move commands for N number of position/speed loop processing periods centering around the position/speed loop processing period concerned is obtained, the number N being equal to the number obtained by dividing the distribution period by the position/speed loop processing periods. A position feedforward amount FFp is obtained by multiplying this average value by a position feedforward coefficient, and a corrected speed command Vc(j) is obtained by adding this position feedforward amount FFp to a speed command obtained in a conventional position loop processing. Further, a speed feedforward processing is executed (S16), a torque command Tc(j) is obtained, and the motor is thereby driven. This feedforward control never causes any variation in the position deviation or any shock on the motor or machine.

Claims10

Dependent claims

A feedforward control method for a servomotor in a servo-circuit, in which a numerical control device periodically distributes a move command to said servo-circuit in a distribution period, said numerical control device storing a plurality of move commands to be distributed in each said distribution period, said distribution period being divided by a number N, N being an integer greater than 1, to produce a plurality of position and speed loop processing periods being equal in duration, said method comprising the steps of:

(a) reading one of said stored move commands to be distributed from said numerical control device in a next distribution period relative to a move command being distributed in a current distribution period;
(b) dividing said one move command into a plurality of position and speed loop move commands, each of said plurality of position and speed loop move commands to be executed in a corresponding one of said plurality of position and speed loop processing periods;
(c) obtaining an average value of said plurality of position and speed loop move commands over said number N, with said average value centering around one of said plurality of position and speed loop move commands being currently executed in a current one of said position and speed loop processing periods;
(d) determining a position feedforward amount by multiplying said average value by a position feedforward coefficient;
and
(e) determining a corrected speed command for a speed loop process by adding said position feedforward amount to a speed command obtained in a position loop process.

3 more elements

A feedforward control method for a servomotor in a servo-circuit, in which a numerical control device periodically distributes a move command to said servo-circuit in a distribution period, said numerical control device storing a plurality of move commands having been distributed and to be distributed in each said distribution period, said distribution period being divided by a number N, N being an integer greater than 1, to produce a plurality of position and speed loop processing periods being equal in duration, said method comprising the steps of:

(a) reading a first one of said stored move commands to be distributed from said numerical control device in a next distribution period relative to a move command being distributed in a current distribution period;
(b) reading a second one of said stored move commands having been distributed from said numerical control device in a previous distribution period relative to said move command being distributed in a current distribution period;
(c) obtaining an average value of a plurality of position and speed loop move commands over said number N, with said average value centering around one of said plurality of position and speed loop move commands being currently executed in a current one of said position and speed loop processing periods, based on said move command being currently executed, said first move command and said second move command;
(d) determining a position feedforward amount by multiplying said average value by a position feedforward coefficient;
and
(e) determining a corrected speed command for a speed loop process by adding said position feedforward amount to a speed command obtained in a position loop process.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/292,762Filed 19 Aug 1994 · continuation
Priority: JP 3-2559779 Sep 1991
Granted: 5 Sep 1995
Term ends: Not estimatedThe source records don’t support an estimate.

Classification4 codes

G05B 19/19
Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to…
G05B 2219/41429
Servomotor, servo controller till figures: mean value of previous feedforward values
G05B 2219/41441
Servomotor, servo controller till figures: position reference ffw for compensation speed reference and speed error
G05B
Control or regulating systems in general