JP2008220019A - Method for identifying coefficient of fluctuation in torque constant of motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an identification method for accurately identifying the coefficient of fluctuations in torque constant using a clear constitution, when the torque constant of a motor fluctuates due to environmental variations, such as variations in the temperature. <P>SOLUTION: The coefficient of fluctuations in torque constant is identified, by computing the ratio of an acceleration signal computed using a motor angle signal to the maximum value or the minimum value of estimated acceleration derived from a current command or a current of the motor. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for identifying a torque constant fluctuation rate of a motor.

Conventionally, in a servo control device using a motor, a control system is constructed by identifying various parameters of the control target so that the control target satisfies the control specifications. However, the torque constant of the motor fluctuates due to environmental changes such as temperature, and the fluctuation of the torque constant causes a significant deterioration in control performance. With respect to this problem, in Patent Document 1, various parameters to be controlled are identified by using a sequential least square method, but there are cases where the calculation load is high and not practical.
JP 2006-217729 A

  In motor control, torque constant fluctuations associated with environmental changes such as temperature may significantly degrade the control performance, and a technique for accurately identifying is essential.

    However, in the above prior art, there is a case where the calculation load is high in the implementation of the identification method and is not practical. The present invention has been made in view of the above-described conventional situation, and an object of the present invention is to provide an identification method for accurately identifying the variation rate of the torque constant with a clear configuration.

  The torque constant variation rate identifying method according to the first aspect of the present invention calculates the ratio between the acceleration signal calculated using the motor angle signal and the maximum value or minimum value of the estimated acceleration derived from the motor current command or current. The torque constant fluctuation rate is identified.

  In the torque constant variation rate identifying method according to the second aspect of the invention, when the transfer function from the angle signal for calculating the acceleration signal to the acceleration signal is non-proper, a low-pass filter of the order in which the transfer function is proper is inserted. Thus, the acceleration signal can be calculated from the angle signal, and the estimated acceleration derived from the current command or current signal is passed through the low-pass filter correspondingly, and the ratio of the maximum value or the minimum value of these signals is calculated. Thus, the torque constant fluctuation rate is identified.

  Specific examples of the present invention will be described below.

  It is assumed that the transfer function P (s) from the current i (s) to the motor angle signal y (s) is expressed by Equation 1.

Here, k _t is a torque constant, J is a moment of inertia, D is a viscous friction coefficient, ζ _k is a damping coefficient, ω _k is a resonance angular frequency, and K _k is a gain.
Since the transfer function P (s) ⁻¹ from the angle signal to the current is a non-proper transfer function having a relative order of second order, the low-pass filter Q (s) is expressed by Equation 2.

Here, ω _l is the cutoff angular frequency of Q (s).
From the above, the schematic diagram of the identification mechanism of the torque constant fluctuation rate α is shown in FIG. Here, α ^ is an estimated torque constant fluctuation rate, α _{a is an} estimated acceleration signal, and α _b is an acceleration signal.
When the torque constant is reduced by 3% (α = 0.97), the simulation waveforms of α _a and α _b during positioning are shown in FIG. Note that Q (s) and P (s) ⁻¹ were z-transformed by bilinear transformation in consideration of the mounting surface.
From FIG. 2, there is a difference in the crest value between α _a which is _a blue line and α _b which is _a red line, and the ratio of the crest values can be regarded as the fluctuation rate of the torque constant. Formula 3 shows the ratio of the crest values of α _a and α _b .

Here, α _amax and α _bmax are the maximum values of α _a and α _b .
From Equation 3, the method according to the present invention accurately identifies the fluctuation rate of the torque constant assumed in the simulation, and the effectiveness thereof is shown.

  While the present invention has been described with reference to the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments and can be appropriately modified and applied without departing from the spirit thereof.

  The motor torque constant variation rate identifying method according to the present invention can be used for various motor control devices.

It is a block diagram of the identification method of the torque constant variation rate of a motor. It is the waveform of α _a and α _{b in} FIG. 1 when the torque constant fluctuates.

Claims (2)

    Torque constant fluctuation characterized by identifying the torque constant fluctuation rate of the motor from the ratio of the acceleration signal calculated using the motor angle signal and the maximum value or minimum value of the estimated acceleration signal derived from the current command or current signal Rate identification method.   When the transfer function from the motor angle signal to the acceleration signal for calculating the acceleration signal is non-proper, the low-pass filter in which the transfer function is proper is added to the transfer function and the estimated acceleration signal A torque constant fluctuation rate identifying method characterized by identifying a torque constant fluctuation rate from a ratio of signals passed through a low-pass filter.