Servo motor control apparatus

• US 5,134,354 A
• Filed: 12/03/1990
• Issued: 07/28/1992
• Est. Priority Date: 04/10/1989
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Yaskawa Denki Seisakusho
• Original Assignee: Kabushiki Kaisha Yaskawa Denki Seisakusho
• Inventors: Yamamoto, Yoichi, Tohya, Takayuki, Hiraga, Yoshiji
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Bergmann, Saul M.
• Application Number:
  US07/623,410
• Time in Patent Office: 603 Days
• Field of Search: 318/609, 318/610, 318/611, 318/561, 318/616, 318/615, 364/161, 364/162
• US Class Current: 318/609
• CPC Class Codes: G05B 19/231 the positional error is used to control continuously the servomotor according to its magnitude
• CPC Class Codes: G05B 19/237 with a combination of feedback covered by G05B19/232 - G05B19/235
• CPC Class Codes: G05B 2219/37313 Derive speed from position
• CPC Class Codes: G05B 2219/41084 Compensation speed axis with changing, reversing direction, quadrant circle
• CPC Class Codes: G05B 2219/41421 Eliminate, diminish delay in feedback speed
• CPC Class Codes: G05B 2219/42034 Pi regulator
• CPC Class Codes: G05B 2219/42035 I regulator
• CPC Class Codes: G05B 2219/42062 Position and speed and current
• CPC Class Codes: G05B 2219/42096 Add, substract i part of speed feedback as function of sign speed error

Abstract

When a workpiece is cut or otherwise machined by a machine using a servo motor control apparatus having a position feedback loop, a velocity feedback loop, and a current feedback loop, it is the common practice to preset the instructed current value to a voltage corresponding to friction torque when rotation of the motor is started or reversed. This is to compensate for the response delay of the motor introduced by the friction torque. The present invention relates to improvements in this technique. After the instructed motor velocity changes from a positive value, to a negative value or vice versa, or after the detected motor velocity changes from a positive value to a nonpositive value or from a negative value to a nonnegative value, the value of the integration element of a velocity control portion is reversed according to a function. The obtained output value is added to the instructed current value or to the integration term to compensate for the response delay, thus reducing machining error.

Claims

1. A servo motor control apparatus having a motor velocity feedback loop, with a motor torque feedback loop or motor current feedback loop formed inside the velocity feedback loop, a velocity control portion comprised of a microcomputer, and a controller included in the velocity control portion and having at least a proportional element and an integration element, said servo motor control apparatus comprising means connected to reverse the output value of the integration element of the velocity control portion with a function that smooths stepwise changes of an input to said velocity control portion and to add the output value of the integration element either to an instructed current value or to the integration element after an instructed motor velocity changes from a positive value to a negative value or vice versa, or after the detected velocity of the motor changes from a positive value to a nonpositive value, or from a negative value to a nonnegative value.

2. A servo motor control apparatus having a motor velocity feedback loop with a motor torque feedback loop or motor current feedback loop formed inside the velocity feedback loop, a velocity control portion consisting of a microcomputer, and a controller included in the velocity control portion and having at least a proportional element and an integration element, said servo motor control apparatus comprising means connected to change the output value of the integration element of the velocity portion with a function that smooths stepwise changes of an input to said velocity control portion so as to assume a value corresponding to positive or negative friction, depending upon whether the motor rotates, respectively, forwardly or rearwardly, and to add the output value of the integration element either to an instructed current value or to the output value of the integration element after an instructed motor velocity changes from a positive value to a negative value or vice versa, or after the detected velocity of the motor changes from a positive value to a nonpositive value, or from a negative value to a nonnegative value.

3. The servo motor control apparatus of claim 2, wherein after the instructed motor velocity changes from a positive value to a negative value or vice versa, or after the detected velocity of the motor changes from a positive value to a nonpositive value, or from a negative value to a nonnegative value, a value which overcomes positive or negative friction is made to change according to a function, and wherein the output value is added either to the instructed current value or to the integration term.

4. A servo motor control apparatus having a motor velocity feedback loop with a motor torque feedback loop or motor current feedback loop formed inside the velocity feedback loop, a velocity control portion consisting of a microcomputer, and a controller included in the velocity control portion and having at least a proportional element and an integration element, said servo motor control apparatus comprising means connected to change the output value of the integration element of the velocity control portion with a function that smooths stepwise changes of an input to said velocity control portion so as to assume a value corresponding to positive or negative friction, depending upon whether the motor rotates, respectively, forwardly or rearwardly, and to add the output value of the integration element either to an instructed current value or to the output value of the integration element after an instructed motor velocity changes from zero to a nonzero value.

5. The servo motor control apparatus of claim 4, wherein after the instructed motor velocity changes from zero to a nonzero value, a value overcoming positive or negative friction is made to change according to function, and wherein the output value is added either to the instructed current value or to the integration term.