SERVO MOTOR CONTROL APPARATUS AND CONTROL METHOD

• US 20120268054A1
• Filed: 06/14/2012
• Published: 10/25/2012
• Est. Priority Date: 01/17/2007
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Kishimoto, Kenichi, Tazawa, Tooru
• Granted Patent: US 8,410,741 B2
• Time in Patent Office: Days
• US Class Current: 318/619
• CPC Class Codes: H02P 23/18 Controlling the angular speed together with angular position or phase
• CPC Class Codes: H02P 23/22 Controlling the speed digitally using a reference oscillator, a speed proportional pulse rate feedback and a digital comparator

Abstract

A servo motor control apparatus has a feedback loop. When an oscillation detection signal indicates no detection of oscillation, a parameter operating section gives an updating section an operational instruction to set a control parameter in accordance with a supplied set value. When the oscillation detection signal indicates detection of oscillation, the parameter operating section gives the updating section an operational instruction to set such a control parameter as to narrow a frequency band width of the feedback loop.

Claims

1. A servo motor control apparatus, having a feedback loop which obtains an amount of deviations from command information notified from outside and information on a rotational operation detected by a detection section, performs arithmetic operation processing on the deviation amount by use of a predetermined control parameter group including a control gain, and controls a rotational operation of a servo motor by a rotation control signal generated by the arithmetic operation processing, to perform feedback control such that the rotational operation of the servo motor tracks the command information, the apparatus comprising:

an oscillation detecting section, which detects oscillation of the feedback loop, to output an oscillation detection signal indicating a result of the detection;

an inertia estimating section, which estimates a moment of inertia of the servo motor and a load thereof, to output an inertia estimated value generated by the estimation;

an inertia setting section, which outputs as an inertia set value being a value of the moment of inertia, the inertia estimated value after the value becomes effective, or an inertia value set as the moment of inertia before the inertia estimated value becomes effective;

a stiffness value updating section, which is supplied with a stiffness value in accordance with stiffness of a load of the servo motor as the set value, and outputs the stiffness value while making an update thereon; and

a parameter setting section, which converts the stiffness value of the stiffness value updating section into a plurality of control parameter values, and supplies each of the converted control parameter values to the feedback loop, to set the values therein, wherein

when the oscillation detection signal indicates detection of oscillation after the inertia estimated value becomes effective, in accordance with an operational instruction of the parameter operating section, the stiffness value updating section switches the stiffness value thereof to a value corresponding to stiffness lower by a predetermined rank than the current value, to supply the switched value to the parameter setting section.

2. The servo motor control apparatus according to claim 1, wherein

when the oscillation detection signal indicates detection of oscillation within predetermined time from the inertia estimated value becoming effective, the stiffness value updating section switches the output value thereof to a value corresponding to stiffness lower by a predetermined first rank than the current output value, and

when the oscillation detection signal indicates detection of oscillation after the predetermined time from the inertia estimated value becoming effective, the stiffness value updating section switches the output value thereof to a value corresponding to stiffness lower by a predetermined second rank than the current output value, and

the predetermined first rank has a larger value than the predetermined second rank.

3. The servo motor control apparatus according to claim 1, further having;

a velocity gain calculating section, which multiplies a set value of the moment of inertia of the servo motor and the load thereof by a frequency band set value, to output an obtained value as a velocity gain; and

a stable stiffness value calculating section, which calculates as a stable stiffness value a value that satisfies a condition that an output value of the velocity gain calculating section after the inertia estimated value becomes effective is not more than an output value of the velocity gain calculating section before the inertia estimated value becomes effective, and corresponds to the highest stiffness as a stiffness value after the inertia estimated value becomes effective, wherein

when the oscillation detection signal indicates detection of oscillation within predetermined time from the inertia estimated value becoming effective, the stiffness value updating section switches the output value thereof to an output value of the stable stiffness value calculating section, and,

when the oscillation detection signal indicates detection of oscillation after the predetermined time from the inertia estimated value becoming effective, the stiffness value updating section switches the output value thereof to a value corresponding to stiffness lower by a predetermined rank than the current output value.

4. The servo motor control apparatus according to claim 3, wherein

when the oscillation detection signal indicates detection of oscillation within predetermined time from the inertia estimated value becoming effective and the stable stiffness value is a value corresponding to stiffness lower than the current value, the stiffness value updating section switches the output value thereof to an output value of the stable stiffness value calculating section, and,

when the oscillation detection signal indicates detection of oscillation after the predetermined time from the inertia estimated value becoming effective, or when the oscillation detection signal indicates detection of oscillation within the predetermined time from the inertia estimated value becoming effective and the stable stiffness value is a value corresponding to stiffness not less than the current stiffness, the stiffness value updating section switches an output value thereof to a value corresponding to stiffness lower by a predetermined rank than the current output value.

5. A servo motor control apparatus, having a feedback loop which obtains an amount of deviations from command information notified from outside and information on a rotational operation detected by a detection section, performs arithmetic operation processing on the deviation amount by use of a predetermined control parameter group including a control gain, and controls a rotational operation of a servo motor by a rotation control signal generated by the arithmetic operation processing, to perform feedback control such that the rotational operation of the servo motor tracks the command information, the apparatus comprising:

an oscillation detecting section, which detects oscillation of the feedback loop, to output an oscillation detection signal indicating a result of the detection;

an inertia estimating section, which estimates a moment of inertia of the servo motor and a load thereof, to output an inertia estimated value generated by the estimation; and

an inertia setting section, which outputs either the inertia estimated value or an inertia value set as the moment of inertia as an inertia set value, wherein

when the oscillation detection signal indicates detection of oscillation, the inertia setting section switches the output value thereof to a value reduced at a predetermined ratio with respect to the current output value.

6. The servo motor control apparatus according to claim 5, further having:

a stiffness value updating section, which is supplied with a stiffness value in accordance with stiffness of a load of the servo motor as the set value, and outputs the stiffness value while making an update thereon;

a parameter setting section, which converts the stiffness value of the stiffness value updating section into a plurality of control parameter values, and supplies each of the converted control parameter values to the feedback loop, to set the values therein; and

a stiffness value determining section, which outputs an inertia reduction command signal to the inertia setting section upon receipt of the oscillation detection signal and the stiffness value outputted by the stiffness value updating section, wherein

when the oscillation detection signal indicates detection of oscillation, upon determination of an output value of the stiffness value updating section as being a value equal to a predetermined stiffness value or a value corresponding to stiffness lower than the predetermined stiffness value, the stiffness value determining section gives the inertia setting section a command to switch the output value thereof to a value reduced at a predetermined ratio with respect to the current output value.

7. A servo motor control method, for a servo motor having a feedback loop which obtains an amount of deviations from command information notified from outside and information on a rotational operation detected by a detection section, performs arithmetic operation processing on the deviation amount by use of a predetermined control parameter group including a control gain, and controls a rotational operation of the servo motor by a rotation control signal generated by the arithmetic operation processing, to perform feedback control such that the rotational operation of the servo motor tracks the command information, the method comprising the steps of;

detecting oscillation of the feedback loop;

estimating a moment of inertia of the servo motor and a load thereof, to output an inertia estimated value generated by the estimation;

outputting as an inertia set value being a value of the moment of inertia, the inertia estimated value after the value becomes effective, or an inertia value set as the moment of inertia before the inertia estimated value becomes effective;

being supplied with a stiffness value in accordance with stiffness of a load of the servo motor as the set value, and outputting the stiffness value while making an update thereon; and

converting the stiffness value into a plurality of control parameter values, and supplying each of the converted control parameter values to the feedback loop, to set the values therein, and

when the oscillation is detected after the inertia estimated value becomes effective, the stiffness value is switched to a value corresponding to stiffness lower by a predetermined rank than the current value.

8. A servo motor control method, for a servo motor having a feedback loop which obtains an amount of deviations from command information notified from outside and information on a rotational operation detected by a detection section, performs arithmetic operation processing on the deviation amount by use of a predetermined control parameter group including a control gain, and controls a rotational operation of the servo motor by a rotation control signal generated by the arithmetic operation processing, to perform feedback control such that the rotational operation of the servo motor tracks the command information, the method comprising the steps of;

detecting oscillation of the feedback loop;

estimating a moment of inertia of the servo motor and a load thereof, to output an inertia estimated value generated by the estimation; and

outputting either the inertia estimated value or an inertia value set as the moment of inertia as an inertia set value, wherein

when the oscillation is detected, the output value is switched to a value reduced at a predetermined ratio with respect to the current output value.