JP2009175946A - Position controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position controller for further improving working accuracy. <P>SOLUTION: This position controller is configured to perform position control for calculating a speed command Vc by multiplying a position deviation between a position command Pc and a detection position Pm by a position loop gain Kp and speed control for calculating a speed deviation being a difference value between the speed command Vc and a detection speed Vm, then calculating a torque command Tc by adding the multiplied value of the speed deviation and a speed loop proportional gain Pv and the multiplied value of the speed deviation and a speed loop integral gain Iv to thereby control a servo motor 10, so that it is possible to control the position of a control object 12 to be driven through a ball screw 11 by the servo motor 10. This position controller is provided with means 16, 17 and 18 for calculating the jerk of the value change of the position command Pc and a gain arithmetic part 19 for varying at least one of the position loop gain Kp, the speed loop proportional gain Pv and the speed loop integral gain Iv according to the magnitude of the jerk. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides a position control for calculating a speed command by multiplying a position deviation between a position command and a detected position by a position loop gain, a speed deviation that is a difference value between the speed command and a detected speed, and then calculating the speed deviation. A speed control for calculating a torque command by adding a multiplication value of the speed loop proportional gain and a multiplication value of the speed deviation and the speed loop integral gain, and controlling the servo motor to control the ball screw by the servo motor. The present invention relates to a position control device that controls the position of a control target driven via the control device.

  FIG. 5 is a block diagram showing an example of a conventional position control device. The subtractor 2 calculates the deviation (Pc−Pm) between the position command Pc from the position command calculator 1 and the motor position detection value Pm from the motor position detector 13 attached to the motor 10, and the position deviation calculator 3. Multiplies the position deviation by a position loop gain Kp to output a speed command Vc. On the other hand, the differentiator 15 differentiates the motor position detection value Pm from the motor position detector 13 attached to the motor 10 and outputs the motor speed detection value Vm. The subtractor 4 calculates a deviation (Vc−Vm) between the speed command Vc and the detected motor speed Vm and outputs it to the speed deviation calculator 5. In the speed deviation calculator 5, the speed deviation proportional component calculator 6 outputs a speed deviation proportional component based on the speed deviation and the speed loop proportional gain Pv. At the same time, the speed deviation integral component calculator 7 outputs a speed deviation integral component based on the speed deviation and the speed loop integral gain Iv. The adder 8 calculates the sum of the speed deviation proportional component and the speed deviation integral component, and outputs a torque command value Tc. The inverter 9 controls the position of the controlled object 12 driven via the ball screw 11 by supplying a current according to the torque command value Tc to the servo motor 10.

  In a large machining center or the like, generally, the mechanical rigidity between the servo motor and the controlled object is low, and the controlled object is likely to vibrate, so the gain cannot be increased. As a result, there is a problem that a tracking error of the movement of the controlled object occurs and the machining accuracy is lowered.

  The following techniques are known as techniques for correcting tracking errors caused by low mechanical rigidity. First, the deflection compensation amount is calculated by multiplying the acceleration of the position command by the reciprocal of the rigidity of the ball screw drive system and the load side moment of inertia. Subsequently, the deflection compensation amount is differentiated to calculate the deflection speed compensation amount. Further, the bending speed compensation amount is differentiated to calculate the bending torque compensation amount. Then, there is known a method for compensating the deflection of the ball screw drive system by adding the calculated deflection compensation amount, deflection velocity compensation amount, and deflection torque compensation amount to the position command value, speed command value, and torque command value, respectively. (For example, refer to Patent Document 1 below).

  As other techniques, the following techniques are also known. First, a speed offset amount is calculated by adding the offset amount proportional to the speed of the position command and the offset amount proportional to the acceleration of the position command. Next, the torque offset amount is calculated by differentiating the speed offset amount. Then, by adding the obtained speed offset amount and torque offset amount to the speed command value and the torque command value, respectively, the tracking error due to low mechanical rigidity is corrected (for example, the following patent document) 2).

Japanese Patent No. 3351990 Japanese Patent No. 373949

  In the region where the speed of the position command or the acceleration of the position command is constant by the above-described conventional technology, it can be treated as an ideal model that is spring-coupled, resulting in low mechanical rigidity. The tracking error can be corrected. However, in the region where the acceleration of the position command changes, the servo motor actually starts after the transient state change of the lubricating oil etc. on the sliding surface or the supply of current according to the torque command value to the servo motor is started. Due to the time delay until the ball screw is rotated after the torque is generated, it cannot be treated as an ideal model coupled with a spring. For this reason, the actual follow-up error amount does not coincide with the delay amount calculated from the ideal model coupled with the spring, and there is a problem that the processing accuracy cannot be increased.

  An object of the present invention is to correct a tracking error caused by low mechanical rigidity even in a region where the acceleration of a position command changes, which cannot be handled as an ideal model coupled with a spring. It is to increase processing accuracy.

  The position control device of the present invention obtains a position deviation for calculating a speed command by multiplying a position deviation between the position command and the detected position by a position loop gain and a speed deviation that is a difference value between the speed command and the detected speed. The servo motor is controlled by performing a speed control for calculating a torque command by adding the multiplication value of the speed deviation and the speed loop proportional gain and the multiplication value of the speed deviation and the speed loop integral gain. In a position control device that controls the position of a control target driven by a motor via a ball screw, a means for calculating a jerk of a value change of a position command, a position loop gain, a speed according to the magnitude of the jerk And a gain calculation unit that varies at least one of a loop proportional gain and a speed loop integral gain.

  According to the present invention, even in a region where the acceleration of the position command cannot be handled as an ideal model coupled with a spring, the following error caused by the low mechanical rigidity is corrected, thereby correcting the processing error. The accuracy can be increased.

  FIG. 1 is a block diagram showing an example of the position control device of the present invention. It should be noted that the same elements as those in the conventional example shown in FIG. The differentiator 16 differentiates the position command Pc from the position command calculator 1, and calculates the value change speed of the position command. This is differentiated by the differentiator 17 and the acceleration of the change in value of the position command is output. The differentiator 18 differentiates this and outputs the jerk Jc of the change in value of the position command. The gain calculation unit 19 varies at least one of the position loop gain Kp, the speed loop proportional gain Pv, and the speed loop integral gain Iv according to the magnitude of the jerk Jc of the position command. The variably adjusted position loop gain Kp, speed loop proportional gain Pv, and speed loop integral gain Iv are sent to the position deviation calculator 3, the speed deviation proportional component calculator 6, and the speed deviation integral component calculator 7, respectively. Is output.

  Hereinafter, with reference to FIG. 2 showing an example in which the position loop gain Kp, the speed loop proportional gain Pv, or the speed loop integral gain Iv is changed by the gain calculation unit 19, the main components of the present invention will be described. explain. The jerk Jc of the position command is converted into an absolute value (| Jc |) by the absolute value generator 20. The absolute value of the jerk | Jc | includes a position loop gain calculation coefficient 21 (αK), a speed loop proportional gain calculation coefficient 22 (αP), and a speed loop integral gain calculation coefficient 23 (αI), respectively. Is multiplied by.

A multiplication value (αK · | Jc |) of the position loop gain calculation coefficient 21 (αK) and the absolute value | Jc | of jerk is output to the position loop gain calculator 24. The position loop gain calculator 24 uses the position loop gain initial value Kp0,
Kp = Kp0 (1 + αK · | Jc |)
The position loop gain Kp calculated in step 1 is output. Accordingly, as the jerk of the position command increases, the speed command Vc calculated by the position deviation calculator 3 in FIG. 1 also increases. As a result, the torque command value increases to correct the position error. Can do.

Further, the product (αP · | Jc |) of the velocity loop proportional gain calculation coefficient 22 (αP) and the absolute value | Jc | of the jerk is output to the velocity loop proportional gain calculator 25. The speed loop proportional gain calculator 25 uses the speed loop proportional gain initial value Pv0,
Pv = Pv0 (1 + αP · | Jc |)
The velocity loop proportional gain Pv calculated in step S is output. Accordingly, as the jerk of the position command increases, the speed deviation proportional component calculated by the speed deviation proportional component calculator 6 in FIG. 1 also increases. As a result, the torque command value increases, resulting in a position error. It can be corrected.

Further, the product (αI · | Jc |) of the velocity loop integral gain calculation coefficient 23 (αI) and the absolute value of jerk | Jc | is output to the velocity loop integral gain calculator 26. The speed loop integral gain calculator 26 uses the speed loop integral gain initial value Iv0,
Iv = Iv0 (1 + αI · | Jc |)
The velocity loop integral gain Iv calculated in step (1) is output. Accordingly, as the jerk of the position command increases, the speed deviation integral component calculated by the speed deviation integral component calculator 7 in FIG. 1 also increases. As a result, the torque command value increases and the position error is reduced. It can be corrected.

  If all three of the position loop gain Kp, the speed loop proportional gain Pv, and the speed loop integral gain Iv are increased, there is a possibility that the vibration of the servo motor or the controlled object is induced. For this reason, only an arbitrary gain may be selected and varied. For example, the speed loop proportional gain Pv may not be variably adjusted, but only the position loop gain Kp and the speed loop integral gain Iv may be variably adjusted according to jerk.

  Hereinafter, referring to FIG. 3 showing another example in which the position loop gain Kp, the speed loop proportional gain Pv, or the speed loop integral gain is changed by the gain calculation unit 19, the main components of the present invention are described. Will be described. The jerk Jc of the position command is converted into an absolute value (| Jc |) by the absolute value generator 20, and then the position loop gain calculator 27, the speed loop proportional gain calculator 28, and the speed loop integral gain calculator 29, respectively. Output to. The position loop gain calculator 27 uses a correlation between a predetermined absolute value of the position command jerk and the position loop gain, and a position loop gain corresponding to the absolute value | Jc | Output Kp. Accordingly, as the jerk of the position command increases, the speed command Vc calculated by the position deviation calculator 3 in FIG. 1 also increases. As a result, the torque command value increases to correct the position error. Can do. Further, the velocity loop proportional gain calculator 28 uses the relationship between the predetermined absolute value of the position command jerk and the velocity loop proportional gain, according to the absolute value | Jc | The speed loop proportional gain Pv is output. Accordingly, as the jerk of the position command increases, the speed deviation proportional component calculated by the speed deviation proportional component calculator 6 in FIG. 1 also increases. As a result, the torque command value increases and the position error is reduced. It can be corrected. Further, the velocity loop integral gain calculator 29 uses a predetermined relationship between the absolute value of the jerk of the position command and the velocity loop integral gain in accordance with the absolute value | Jc | of the position command at any time. The speed loop integral gain Iv is output. Accordingly, as the jerk of the position command increases, the speed deviation integral component calculated by the speed deviation integral component calculator 7 in FIG. 1 also increases. As a result, the torque command value increases and the position error is reduced. It can be corrected. Note that if the position loop gain Kp, the speed loop proportional gain Pv, and the speed loop integral gain Iv are all increased, there is a possibility of inducing vibrations of the servo motor or the controlled object. It is also possible.

  In FIG. 1, the subtractor 2 calculates the deviation between the position command Pc from the position command calculator 1 and the motor position detection value Pm from the motor position detector 13 attached to the motor 10, and the position deviation calculator 3 describes the semi-closed loop control in which the position deviation is multiplied by the position loop gain Kp and the speed command Vc is output. However, as shown in FIG. 4, the subtractor 2 calculates the deviation between the position command Pc from the position command calculator 1 and the control target position Pl from the linear scale 14 that directly outputs the position of the control target 12, and the position deviation The calculator 3 may be applied to full closed loop control in which the position deviation is multiplied by the position loop gain Kp and the speed command Vc is output.

  As described above, in the present invention, even in a region where the acceleration of the position command changes, which cannot be handled as an ideal model coupled with a spring, a tracking error caused by low mechanical rigidity is eliminated. By correcting the position control device, it is possible to provide a position control device capable of increasing the processing accuracy.

It is a block diagram which shows embodiment of this invention. It is a block diagram which shows embodiment of the gain calculating part of this invention. It is a block diagram which shows other embodiment of the gain calculating part of this invention. It is a block diagram which shows other embodiment of this invention. It is a block diagram which shows a prior art.

Explanation of symbols

  1 Position command calculator, 2, 4 subtractor, 3 Position deviation calculator, 5 Speed deviation calculator, 6 Speed deviation proportional component calculator, 7 Speed deviation integral component calculator, 8 Adder, 9 Inverter, 10 Servo motor , 11 Ball screw, 12 Control object, 13 Motor position detector, 14 Linear scale (Control object position detector), 15, 16, 17, 18 Differentiator, 19 Gain calculator, 20 Absolute value converter, 21 Position loop gain Calculation coefficient, 22 Speed loop proportional gain calculation coefficient, 23 Speed loop integral gain calculation coefficient, 24 Position loop gain calculator, 25 Speed loop proportional gain calculator, 26 Speed loop integral gain calculator, 27 Position loop gain calculator, 28 Speed loop proportional gain calculator, 29 Speed loop integral gain calculator.

Claims (2)

Position control that calculates the speed command by multiplying the position deviation between the position command and the detected position by the position loop gain, and after obtaining the speed deviation that is the difference value between the speed command and the detected speed, the speed deviation and the speed loop proportional gain And a speed control for calculating a torque command by adding a multiplication value of the speed deviation and a multiplication value of the speed deviation and the speed loop integral gain, and controlling the servo motor to drive the servo motor via a ball screw. In the position control device for controlling the position of the control object,
Means for calculating the jerk of the value change of the position command;
A gain calculator that varies at least one of a position loop gain, a speed loop proportional gain, and a speed loop integral gain according to the magnitude of the jerk;
A position control device comprising: The position control device according to claim 1,
The position control device characterized in that the gain calculation unit changes the position loop gain, the speed loop proportional gain, and the speed loop integral gain so as to increase as the jerk value increases.

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