Servomotor controller for controlling periodic reciprocation

• US 8,067,918 B2
• Filed: 04/19/2010
• Issued: 11/29/2011
• Est. Priority Date: 05/21/2009
• Status: Active Grant

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Sonoda, Naoto, Okita, Tadashi, Toyozawa, Yukio
• Primary Examiner(s): Duda; Rina
• Application Number:
  US12/762,781
• Publication Number:
  US 20100295496A1
• Time in Patent Office: 589 Days
• Field of Search: 318/625, 318/798, 318/799, 318/632, 318/638
• US Class Current: 318/625
• CPC Class Codes: G05B 19/404 characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia G05B19/19, G05B19/41 take precedence
• CPC Class Codes: G05B 19/425 Teaching successive positions by numerical control, i.e. commands being entered to control the positioning servo of the tool head or end effector
• CPC Class Codes: G05B 2219/42152 Learn, self, auto tuning, calibrating, environment adaptation, repetition
• CPC Class Codes: G05B 2219/45161 Grinding machine

Abstract

A servomotor controller capable of properly generating reference positions, by which learning control of angle based method may be applied to the periodically reciprocating motion of an object. The learning controller obtains a first positional deviation of a driven object at every predetermined sampling period of time, and the first positional deviation is converted, by a first converting part, to a second positional deviation associated with each reference position in one periodic reciprocating motion of the driven object. After a first correction amount of an immediately previous reciprocating motion of the driven object, stored in a memory, is added to the second positional deviation, the second positional deviation is stored in the memory as a renewed first correction amount. The first correction amount is converted to a second correction amount associated with the sampling period, by a second converting part.

Claims

1. A servomotor controller for controlling a servomotor for performing periodic reciprocating motion of a driven object, the servomotor controller comprising:

a position detector for detecting the position of the driven object;

a positional deviation obtaining part for obtaining a first positional deviation of the position of the driven object detected by the position detector at every predetermined sampling period of time, relative to position command given by a head controller;

a reference position generating part for generating a plurality of reference positions, for one reciprocating period of time of the periodic reciprocating motion of the driven object, the plurality of reference positions being increased in one direction corresponding to the position command or the detected position of the driven object;

a first converting part for converting the first positional deviation obtained by the positional deviation obtaining part to a second positional deviation, the second positional deviation being associated with each of the reference positions generated by the reference position generating part;

an arithmetic adding part for adding the second positional deviation to a first correction amount in an immediately previous period stored in the storing part and for determining a renewed first correction amount;

a storing part for storing the renewed first correction amount associated with each reference position, for one reciprocating period of time of the reciprocating motion of the driven object;

a second converting part for converting the renewed first correction amount stored in the storing part to a second correction amount, the second correction amount being associated with the every predetermined sampling period of time; and

a controlling part for controlling the servomotor based on the first positional deviation and the second correction amount,

wherein

the reference position generating part generates the plurality of reference positions by dividing an integration value which is obtained by integrating absolute speed values for one reciprocating period of time, the absolute speed values being calculated from the sampling period of time and the position command or the position of the driven object at every sampling period of time.

2. The servomotor controller as set forth in claim 1, further comprising a polarity inverting part for inverting the polarities of the first positional deviation and the second correction amount based on the polarity of the speed calculated by the sampling period of time and the position command or the position of the driven object at every sampling period of time.

3. The servomotor controller as set forth in claim 2, wherein the reference position generating part and the polarity inverting part use the position of a driving object which synchronizes with the periodic reciprocating motion of the driven object, instead of using the position command or the position of the driven object.

4. The servomotor controller as set forth in claim 1, further comprising:

a first filter for limiting a frequency bandwidth of the renewed first correction amount obtained by adding the immediately previous first correction amount stored in the storing part to the second positional deviation converted by the first converting part; and

a second filter for compensating a phase and a gain of the first correction amount before the first correction amount stored in the storing part is sent to the second converting part associated with the sampling period of time.

5. The servomotor controller as set forth in claim 2, further comprising:

a first filter for limiting a frequency bandwidth of the renewed first correction amount obtained by adding the immediately previous first correction amount stored in the storing part to the second positional deviation converted by the first converting part; and

a second filter for compensating a phase and a gain of the first correction amount before the first correction amount stored in the storing part is sent to the second converting part associated with the sampling period of time.

6. The servomotor controller as set forth in claim 3, further comprising:

a first filter for limiting a frequency bandwidth of the renewed first correction amount obtained by adding the immediately previous first correction amount stored in the storing part to the second positional deviation converted by the first converting part; and

a second filter for compensating a phase and a gain of the first correction amount before the first correction amount stored in the storing part is sent to the second converting part associated with the sampling period of time.