JP3246572B2 - Load constant measurement method for motor drive system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a load constant of a motor drive system.

[0002]

2. Description of the Related Art As a method of measuring a load constant of a motor, the following method has been used. (1) A sine wave is applied to the motor as an angular velocity command, and the motor is repeatedly operated while changing the frequency of the sine wave, and an inertial load is calculated from the frequency response. (2) Using the step response of the angular velocity, the time constant of the velocity loop is obtained from the response time of the rise, and the inertial load is calculated from the time constant. (3) The torque generated by the motor is integrated, and the inertial load is determined from the ratio between the value and the rotational speed difference.
88780).

[0003]

However, the above (1)
In the method of the above, since the NC machine tool or the like has a backlash due to a speed reducer such as a ball screw between the electric motor and the load, giving the sine wave as the angular velocity command is to destroy the speed reducer of the machine. There's a problem. In the method (2), the delay of the current output in the servo amplifier and the effect of static friction may cause a dead time, and the torque according to the speed command may not be output due to the effect of the dynamic friction during response. There were problems such as a longer time. Therefore, an accurate time constant cannot be obtained, and thus an accurate inertial load cannot be obtained. In the method (3), the torque generated by the motor is integrated, and
The inertial load is calculated from the ratio between the value and the rotational angular velocity difference.If a constant load other than the inertial load is applied to the drive system, the integrated value of the load torque other than the inertial load must be included in the torque integrated value. Since the integrated value of the torque required for purely driving the inertial load is not used, a large error is included in the calculated value of the inertial load. Further, in the above method (3), acceleration / deceleration is performed at a constant acceleration / deceleration rate and rotation speed change width, and the difference between the integral amount of the signal proportional to the motor-generated torque during acceleration and deceleration and the change width of the rotation angular speed are calculated. The method of estimating load inertia by calculation is raised.However, since the effects of static friction and dynamic friction are different between acceleration and deceleration, an accurate inertia load is similarly calculated for a drive system with large static friction and dynamic friction. I couldn't do that. Further, a problem common to the above methods (1) to (3) is that since only the inertial load of the drive system is focused on, the viscous friction coefficient and dynamic friction torque required for control system design cannot be measured, and Since a special operation sequence is required for the load constant measurement, it is difficult to perform the load constant measurement during operation. An object of the present invention is to provide a motor drive system that is not affected by mechanical backlash, static friction, dynamic friction, etc., does not depend on the control method of the motor, and can measure a load constant during normal operation. It is to provide a load constant measuring method.

[0004]

In order to solve the above-mentioned problems, according to the present invention, the upper controller (4) periodically outputs the output torque from the servo controller (5) while a load is applied to the electric motor (1). T, the angular acceleration a obtained by a known method such as an angular velocity ω and a difference from the position feedback is fetched and stored in a temporary storage buffer (41). In the temporary storage buffer (41), T, D, R , J is unique
The data for three samples , which can be obtained in a typical manner, are input to the load constant calculator (42), and T−DR−ω = J · a where T is the output torque of the motor, D is the dynamic friction torque, and R
Is characterized in that a viscous friction coefficient J uses an inertial load to determine a load constant composed of an inertial load, a dynamic friction torque, and a viscous friction coefficient.

[0005]

Generally, the drive system of a motor is represented by a block diagram as shown in FIG. 2, and considers viscous friction, dynamic friction, and inertia load proportional to the angular velocity as the load of the motor. The balance between the motor output torque and the load force is expressed by the following equation (1).

[0006]

(Equation 1)

Here, T is the output torque of the motor, D is the dynamic friction torque, R is the viscous friction coefficient, J is the inertial load, and ω is the angular velocity. However, the inertia of the motor itself is included in J. Here, assuming that the angular acceleration is a, dω / dt =
Since it is a, Expression 1 is expressed by Expression 2 below.

[0008]

(Equation 2)

Here, three points on the time series, that is, t ₀ and t
_{If the} output torque at ₁ and t ₂ is T ₀ , T ₁ , T ₂ , the angular velocity is ω ₀ , ω, ₁ ω ₂ , and the angular acceleration is a ₀ , a ₁ , a ₂ , the following equation holds.

[0010]

[Equation 3]

[0011]

(Equation 4)

[0012]

(Equation 5)

When this is expressed in a matrix, the following equation 6 is obtained.

[0014]

(Equation 6)

From equation (6)

[0016]

(Equation 7)

From the output torques T ₀ , T ₁ , T ₂ , angular velocities ω ₀ , ω, ₁ ω ₂ , and angular accelerations a ₀ , a ₁ , a ₂ at three points in the time series, load constants J, R, D can be determined.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an embodiment. 1 is an electric motor,
2 is a load, 3 is a pulse generator, 4 is a host controller that outputs a position command, and 5 is a servo controller that outputs a drive current to the electric motor 1 from a position command from the host controller 4 and a feedback pulse from the pulse generator 3. is there. The host controller 4 includes the motor 1
During the operation, the output torque T and the position feedback are periodically taken in from the servo controller 5. Then, the angular velocity ω and the angular acceleration a are obtained from the position feedback by a known method such as a difference, and are stored in the temporary storage buffer 41 together with the output torque T. Next, the host controller 4 inputs the data of three samples in the temporary storage buffer 41 to the load constant calculator 42, and calculates the load constant using Expression 7. The inertia load J, the static friction and the dynamic friction torque D, and the viscous friction coefficient R are obtained by changing the time and repeating the load constant calculation from the data at three points in the time series, so that the accuracy of the constant measurement is improved, and Dynamic load fluctuations can also be measured. The measured load constant is used for servo controller tuning and the like. In the present invention, the calculation of the load constant and the like is performed by the host controller. However, the present invention is not limited to the configuration of the above embodiment, and the servo controller may perform the calculation.

[0019]

As described above, according to the present invention,
Since the load constant is determined from the angular velocity, angular acceleration and output torque during operation of the motor drive system, it is not affected by mechanical backlash, static friction, dynamic friction, etc., does not depend on the control method of the motor, and is usually There is an effect that the load constant can be measured during operation.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a balance between an output torque and a load torque of the electric motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Motor 2 Load 3 Pulse generator 4 Host controller 41 Temporary storage buffer 42 Load constant calculator 5 Servo controller

Claims (1)

(57) [Claims] An upper controller (4) periodically obtains an output torque T from a servo controller (5) with a load applied to a motor (1) by a known method such as an angular velocity ω and a difference from position feedback. The angular acceleration a is taken and stored in a temporary storage buffer (41), and T, D, R, and J of the following equations are uniquely defined in the temporary storage buffer (41).
The data for the three samples to be obtained are input to the load constant calculator (42), and T−D−R · ω = J · a, where T is the output torque of the motor, D is the dynamic friction torque, and R is the dynamic friction torque.
Is a method of measuring a load constant of a motor drive system, wherein a viscous friction coefficient J is a load constant composed of an inertial load, a dynamic friction torque, and a viscous friction coefficient using an inertial load.