Servo controlling device and method
First Claim
1. A servo controlling method which has a control loop using a position/speed feedback and drives a feed axis of a machine tool, wherein after a movement reversal of the feed axis is detected, a control loop is modeled, and a virtual internal model using constants of values that are different from those of the constants used in the control loop;
- a virtual torque instruction calculated in the virtual internal model is added to a torque instruction for driving the feed axis;
when said virtual torque instruction reaches a predetermined value, said adding is terminated; and
when the adding is terminated, a value of an integrator within the virtual internal model at this point is added to a corresponding integrator of the position/speed feedback group.
1 Assignment
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Accused Products
Abstract
When a position/speed feedback changes while a control system for driving a feed axis uses an integration gain during a shaft stopping, the control system goes unstable to cause a torque instruction to vibrate or diverge. In addition, only a single, narrow-range feed speed can be accommodated to find an out-of-range speed to be insufficient or excessive in compensation effects. After detecting the movement reversal of a feed axis, a control loop is modeled, a virtual internal model computing unit (21) using a constant separate from a constant used in a control loop is configured, a virtual torque instruction (22) computed by this computing unit (21) is added to a torque instruction (16) for driving the feed axis, this adding is terminated when the virtual torque instruction (22) reaches a specified value, and a value (25) of an integrator in a virtual internal model at the adding termination is added to the integrator (14) corresponding to a position/speed feedback loop.
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Citations
5 Claims
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1. A servo controlling method which has a control loop using a position/speed feedback and drives a feed axis of a machine tool, wherein
after a movement reversal of the feed axis is detected, a control loop is modeled, and a virtual internal model using constants of values that are different from those of the constants used in the control loop; -
a virtual torque instruction calculated in the virtual internal model is added to a torque instruction for driving the feed axis;
when said virtual torque instruction reaches a predetermined value, said adding is terminated; and
when the adding is terminated, a value of an integrator within the virtual internal model at this point is added to a corresponding integrator of the position/speed feedback group. - View Dependent Claims (2)
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3. A servo controlling device for controlling a motor based on an inputted position instruction, comprising:
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a position detecting part for detecting the position of a rotor of said motor as a motor position;
a speed detecting part for detecting the speed of the motor;
a position controlling part which outputs a speed instruction so that the motor position corresponds to said position instruction;
a speed controlling part which outputs a torque instruction so that the motor speed corresponds to said speed instruction;
a current controlling part which inputs said torque instruction and drives the motor by controlling a current;
a disturbance estimating part which estimates a motor stop timing tz when detecting that the motor speed has become zero by monitoring the motor speed, and outputs an estimated disturbance Cs (t) calculated by Cs (t)=−
Fc1+(Cs (tz)+Fc1) exp ((t−
tz)/et1) −
DcVfb (t) in a case where t≦
tz, orCs (t)=Fc2+(Cs (tz)−
Fc2) exp ((tz−
t)/et2)+DcVfb (t) in a case where t>
tz, provided that the motor speed is defined as Vfb (t), the viscous friction is defined as Dc, the Coulomb friction when the motor speed is positive is defined as Fc1, the Coulomb friction when the motor speed is negative is defined as Fc2, a value of an estimated disturbance at the timing tz is defined as Cs (tz), a time constant of the estimated disturbance Cs (t) when the motor decelerates and stops is defined as et1, and a time constant of the estimated disturbance Cs (t) when the motor accelerates is defined as et2; and
means for adding the estimated disturbance Cs (t) to the torque instruction. - View Dependent Claims (4, 5)
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Specification