KR20130126341A - Method and apparatus for compensating sinusoidal optical encoder signal - Google Patents

Abstract

The present invention relates to an apparatus and a method for compensating sine waves of optical encoder signals. The invention comprises a signal compensating unit which compensates cosine and sine signals by calculating phase difference and gain between the sing and cosine signals from the encoder; and a control signal generating unit which generates signals for controlling the encoder using the calculated phase difference and gain. The invention is provided to accurately and quickly compensate the signals of the encoder even under a fast controlled environment. [Reference numerals] (100) Encoder;(102) Low pass filter;(106) Signal compensating unit;(AA) Control signal

Description

TECHNICAL FIELD The present invention relates to a sinusoidal optical encoder signal compensation method and apparatus,

The present invention relates to a sinusoidal optical encoder signal compensation method and apparatus, and more particularly, to a method and apparatus that can quickly and accurately compensate for sinusoidal optical encoder signal distortion.

In a servo system, a sinusoidal optical encoder is mainly used to detect rotation angle or position information.

The sinusoidal optical encoder changes the amplitude of the output signal according to the change of the speed and is influenced by noise or disturbance components coming into the sinusoidal optical encoder. When the influence of the amplitude and noise of the sinusoidal optical encoder is confirmed by the Lissajous curve, the Lissajous curve becomes smaller and affected by the noise and disturbance due to the speed change.

Therefore, when the amplitude of the sinusoidal optical encoder signal and the noise and disturbance can not be compensated, the distortion of the encoder signal appears.

 The arc-tangent method and the look-up table method are widely used in the conventional signal compensation method.

This method is simple to implement, has a constant error range, and is not affected by speed variations. However, the calculation time to compensate the signal is irregular and the accuracy of the position information is determined by the size of the memory.

Heydemann's proposed method compensates for non-ideal signals using sine and cosine least-squares methods. However, the method proposed by Heydemann has a complicated calculation process and can not be applied online.

Balemi proposed a method that can be applied online by using a gradient search method using the difference between the actual angle and the predicted angle. Using the gradient navigation method, the calculation process is simple and can be applied online. However, it is difficult to compensate with the ideal signal when high speed application such as spiral servo track writing (STW) of HDD (Hard Disk Driver) is applied and when the direction of encoder signal is changed.

Phase Shifted Sinusoid (PSS) interpolation was proposed by Benammar. PSS interpolation can accurately and linearly calculate the phase of an encoder without a processor or a look-up table. However, since the PSS interpolation method is implemented by an analog circuit, there is a disadvantage that switching noise can be accompanied.

In order to solve the problems of the prior art as described above, the present invention proposes a sinusoidal optical encoder signal compensation method and apparatus capable of signal compensation of a sinusoidal optical encoder even in high-speed and high-speed control.

In order to achieve the above object, according to a preferred embodiment of the present invention, there is provided an apparatus for compensating a signal of an encoder, comprising: a gain and a phase difference between a sine signal and a cosine signal output from the encoder, An adaptive signal corrector for correcting the signal; And a control signal generator for generating a control signal for controlling the encoder using the calculated gain and phase difference.

The adaptive signal correction unit may calculate the gain and phase difference on the assumption that the gain ratio of the sine signal and the cosine signal does not change.

The adaptive signal compensator may set an initial value of the gain and phase difference and determine a final value of the gain and phase difference through iterative calculation for each period.

The sine signal and the cosine signal estimated by the above assumption are defined as follows,

[Mathematical Expression]

와

는 이득,

와

는 오프셋,

는 위상 차이임

Wow

Is the gain,

Wow

Lt; / RTI >

Is the phase difference

Using the trigonometric function, the gain and phase difference can be defined as follows.

[Mathematical Expression]

는 signum 함수이고,

은 충분히 작은 양의 값이고,

는

범위에서 선택되는 변수임

Is the signum function,

Is a sufficiently small positive value,

The

Variable to be selected in scope

The adaptive signal correction unit may calculate a gain and a phase difference of the sine signal and the cosine signal through the iterative calculation of Equation (2) for each period.

The control signal generator may generate a control signal for compensating the encoder signal using a phase shifted sinusoid (PSS) interpolation method.

And a gradient search unit for calculating a difference between an actual angle and a predicted angle of the encoder by using the calculated gain and phase difference, wherein the control signal generator generates the control signal using the angle difference calculated in the gradient search unit, Signal can be generated.

The adaptive signal compensator may adaptively correct the sine signal and the cosine signal through demodulation of the digital value by inputting digital values of a sine signal and a cosine signal output from the encoder.

According to another aspect of the present invention, there is provided a method of compensating an encoder signal, comprising the steps of: calculating a gain and a phase difference of a sine signal and a cosine signal output from the encoder to adaptively correct the sinusoidal signals; And generating a control signal for controlling the encoder using the calculated gain and phase difference.

According to the present invention, since the sinusoidal optical encoder is compensated by adaptively correcting the signal output from the sinusoidal optical encoder and applying the PSS interpolation method to the phase difference of the corrected signal, it is possible to perform fast and accurate compensation.

1 illustrates a servo system including a sinusoidal optical encoder in accordance with an embodiment of the present invention.
2 is a diagram showing a detailed configuration of a signal compensator according to a preferred embodiment of the present invention;
3 is a diagram for explaining a PSS interpolation method;
4 is a simulation layout diagram for confirming results according to the present embodiment.
Figure 5 shows the encoder output signal before compensation;
6 is a diagram showing an encoder output signal after signal compensation according to the present embodiment.
7 is a diagram showing an encoder output signal when only a gradient search algorithm is applied;
8 is a diagram showing Lissajous curves of each of the signal compensation and gradient search algorithms according to the present embodiment.
FIG. 9 is a diagram comparing magnitudes of estimated position profiles and estimated errors when only the signal compensation and the gradient search algorithm according to the present embodiment are applied. FIG.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate a thorough understanding of the present invention, the same reference numerals are used for the same means regardless of the number of the drawings.

1 is a diagram illustrating a servo system including a sinusoidal optical encoder according to an embodiment of the present invention.

1, the servo system according to the present embodiment may include an encoder 100, a low-pass filter 102, an analog-to-digital converter 104, and a signal compensation unit 106.

The encoder 100 detects the state (position, rotation angle, and the like) of the rotor (not shown) of the servo system. The encoder 100 according to the present embodiment includes a light- And a sinusoidal optical encoder for outputting sinusoidal signals of sine signals and cosine signals.

When the rotary disk of the sinusoidal optical encoder is placed between the light source for transmitting light and the light receiving element and rotated, a pulse output proportional to the rotation angle can be obtained.

At this time, the encoder 100 simultaneously outputs the sine signal and the consine signal.

Each of the output sine signal and the consine signal is converted into a digital value in the analog-digital converter 104 via the low-pass filter 102.

The signal compensator 106 according to this embodiment corrects the signal output from the encoder 100 using the sine signal and the consine signal input as digital values and calculates the gain and phase difference of the signal.

2, the signal compensator 106 according to the present embodiment calculates a gain and a phase difference of a sine signal and a cosine signal output from the encoder 100, and adaptively corrects the sine signal and the cosine signal, And a control signal generator 204 for generating a control signal for controlling the encoder 100 using the gain and phase difference calculated by the adaptive signal corrector 200 and the adaptive signal corrector 200 can do.

Preferably, the signal compensation unit 106 according to the present embodiment may include a gradient search unit 202.

The gradient search unit 202 calculates the difference between the actual angle and the predicted angle of the rotor by applying the calculated gain and phase difference to the gradient search algorithm.

The control signal generator 204 generates a signal for controlling the encoder 100 by applying the angular difference calculated as described above to the PSS interpolation method.

Here, the control signal is a signal that can compensate for the amplitude change, noise, and disturbance of the signal output from the encoder 100.

The output control signal is fed back to the encoder 100 so that the encoder 100 outputs the compensated signal.

Hereinafter, the adaptive signal correction method, the gradient search algorithm, and the digital interpolation method will be described in detail.

The sine and consine signals output from the sinusoidal optical encoder 100 can be expressed as follows.

는 엔코더(100)에서 출력되는 consine 신호,

는 엔코더(100)에서 출력되는 sine 신호이며,

와

는 이득이다. 또한

와 는 오프셋을 나타내고

는 위상 차이를 나타낸다.

A consine signal output from the encoder 100,

Is a sine signal output from the encoder 100,

Wow

Is the gain. Also

Wow Represents an offset

Represents the phase difference.

와

, 그리고 오프셋

와

가 추정

될 수 있으며, 이러한 동작 상태에서

(sine 신호 및 cosine 신호의 DC 이득 비율)의 비율 및 오프셋은 변하지 않는 것으로 가정할 수 있다.Generally, when there is no loss, and when operating at very low speeds,

Wow

, And offset

Wow

Estimate

In this operating state,

(the DC gain ratio of the sine signal and the cosine signal) and the offset do not change.

The cosine signal and the sine signal estimated by this assumption can be expressed as follows.

이고,

이다. here,

ego,

to be.

와

를 구하는 것이 필요하다. In Equation (2), at various speeds of the rotor

Wow

.

Using the trigonometric function, equation (2) can be summarized as follows.

Therefore, the gain is as follows.

The phase difference is as follows.

는 signum 함수이고, 다음의 반복 계산식으로 표현될 수 있는

은 충분히 작은 양의 값이다. here,

Is a signum function, and can be expressed by the following iteration formula

Is a sufficiently small positive value.

는

범위에서 선택되는 변수이며, 수학식 6을 통해 미리 설정된 횟수 동안 반복 계산하는 경우 위상 차이를 계산할 수 있다. here,

The

And the phase difference can be calculated when the iterative calculation is performed for a predetermined number of times through Equation (6).

According to the present embodiment, the gain can be easily calculated on the assumption that the ratio of the gain of the sine signal and the cosine signal output from the encoder 100 does not change.

Also, it is possible to rapidly perform the gain and phase difference for signal compensation of the encoder 100 at the initial value input by the user through the iterative calculation using Equations (4) and (6).

According to a preferred embodiment of the present invention, the sine and cosine signals obtained after adaptive signal correction is applied to the gradient search algorithm.

Equation (1) can be rewritten as follows.

,

,

,

,

이다. here,

,

,

,

,

to be.

Using trigonometric equations can be expressed as:

이며,

이다. here,

Is,

to be.

는

로 정의되며, 이는 수학식 8의 오차를 최소화할 수 있고 목적함수의 그래디언트,

는

및 파라미터들의 추정을 위해 오프라인 데이터를 이용하여 계산된다. The objective function,

The

, Which can minimize the error of Equation (8) and can be used to determine the gradient of the objective function,

The

And the off-line data for estimation of the parameters.

를 통해 회전자의 실제 각도와 예측 각도의 차이를 계산한다.By applying a gradient of objective function

To calculate the difference between the actual angle of the rotor and the predicted angle.

는 충분히 작은 값이다. here

Is sufficiently small.

The signal compensator 106 according to the present embodiment calculates the difference between the actual angle and the predicted angle of the rotor using the adaptively corrected signal and interpolates the calculated difference using the PSS interpolation described below And generates a control signal (eigenvalue for controlling the rotation of the encoder).

According to the present embodiment, multiple PSSs such as the following equations are used.

는 고정된 각도

이고, N 은 자연수이다. Where i = 1, 3, 5, ..., 2 N -1,

A fixed angle

And N is a natural number.

As shown in FIG. 3, a pseudo linear segment (PLS) satisfying the following equation (10) is generated.

는 출력 신호다. here,

Is an output signal.

는 다음과 같다.If the PLS is linear,

Is as follows.

,

,

, 그리고

는 도 에 도시된 바와 같이, 이진 출력 (

,

,

,

,

)이다.here,

,

,

, And

As shown in the figure, the binary output (

,

,

,

,

)to be.

은 PLS의 선형적 구간에서 절대적 에러를 최소화하도록 해야 한다. 본 실시예에 따른 PSS 보간법은 간단하게 구현될 수 있고 스위칭 노이즈 문제를 해결할 수 있다.

Should minimize the absolute error in the linear section of the PLS. The PSS interpolation method according to the present embodiment can be implemented simply and can solve the switching noise problem.

4 shows a simulation arrangement for verifying the signal compensation type according to the present embodiment.

As shown in FIG. 4, the signal output of the encoder 100 is implemented by the sine (cosine) function of MATLAB Simulink.

Non-ideal signal components such as gain, phase, and offset are added to the simulation placement, as shown in Table 1.

Simulation conditions Parameter Value Sampling rate of ADC 2 [MHz] Resolution of ADC 16 [bit] Noise -0.002 to 0.002 [V] Offset Cos + 0.2 [V] Phase ° Sin (x-3.6) Gain Sin × 1.1 [V]

The encoder signal (before compensation) passed through the low-pass filter is shown in Fig.

In this simulation, digital logic for adaptive signal correction and digital PSS interpolation is implemented in C language using s-function.

In this simulation, the conditions of digital PSS interpolation to minimize absolute error are N = 16 and k _N = 57.573 °. The remaining conditions are shown in Table 1 above.

As shown in Fig. 6, the encoder signal subjected to the adaptive signal correction in this simulation is close to an ideal signal.

However, if only the conventional gradient search method is used to compensate for the amplitude change effect, the Lissajous signal can not be completely restored as shown in FIG.

The usefulness of the method proposed in FIG. 8 can be confirmed.

The Lissajous curve in the case of applying the adaptive signal correction method according to the present embodiment shows a perfect circle shape unlike the case of using only the gradient search method.

Next, digital PSS interpolation was performed after adaptive signal correction.

The difference between the location profile and the estimated location is shown in FIG.

It can be seen that the oscillation time and the settling time are sufficiently reduced, and the estimated error angle is 0.8 °, which is the same value as at 36 count.

It will be apparent to those skilled in the relevant art that various modifications, additions and substitutions are possible, without departing from the spirit and scope of the invention as defined by the appended claims. The appended claims are to be considered as falling within the scope of the following claims.

Claims (10)

An apparatus for compensating for an encoder signal,
An adaptive signal corrector for correcting the sine signal and the cosine signal by calculating a gain and a phase difference between the sine signal and the cosine signal output from the encoder; And
And a control signal generator configured to generate a control signal for controlling the encoder by using the calculated gain and phase difference.
The method of claim 1,
And the adaptive signal correcting unit calculates the gain and phase difference assuming that the DC gain ratio and the offset ratio of the sine signal and the cosine signal do not change. 3. The method of claim 2,
Wherein the adaptive signal compensator comprises:
Wherein an initial value of the gain and phase difference is set and a final value of the gain and phase difference is determined through iterative calculation for each period. 3. The method of claim 2,
The sine signal and cosine signal estimated by the assumption are defined as follows.
[Mathematical Expression]

Wow

Is the gain,

Wow

Lt; / RTI >

Is the phase difference
And the gain and phase difference are defined as follows using a trigonometric function.
[Mathematical Expression]

Is the signum function,

Is a sufficiently small positive value,

The

Variable to be selected in scope
5. The method of claim 4,
Wherein the adaptive signal corrector calculates a gain and a phase difference of the sine signal and the cosine signal through the iterative calculation of Equation (2).
The method of claim 1,
Wherein the control signal generator comprises:
An encoder signal compensation device for generating a control signal for compensating the encoder signal by using a phase shifted sinusoid (PSS) interpolation method. The method of claim 1,
And a gradient search unit for calculating a difference between an actual angle and a predicted angle of the encoder using the calculated gain and phase difference,
Wherein the control signal generator generates the control signal using the angle difference calculated by the gradient search unit. The method of claim 1,
And the adaptive signal compensator is configured to input digital values of the sine signal and the cosine signal output from the encoder to adaptively correct the sine signal and the cosine signal through demodulation of the digital values.
A method of compensating for an encoder signal,
Adaptively correcting the plurality of sinusoidal signals by calculating a gain and a phase difference between a sine signal and a cosine signal output from the encoder; And
And generating a control signal for controlling the encoder using the calculated gain and phase difference. 10. The method of claim 9,
In the adaptive signal correction step, the gain and phase difference are calculated on the assumption that the gain ratios of the sine signal and the cosine signal do not change.

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