JPH09265321A - Analog-to-digital converter for servo controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the servo control precision by correcting the output that undergone the A/D (analog/digital) conversion based on a map where the correction coefficients are previously set in each of areas that are divided according to the nonlinear characteristic. SOLUTION: A sensor 1 outputs an electric variable according to the physical value, and the analog signal outputted from the sensor 1 is converted into a digital signal by an A/D conversion means 50. An error correction means 51 corrects the converted digital signal and outputs it. If the sensor 1 has the nonlinear characteristic, the means 51 divides a measurement range into plural areas according to the nonlinear characteristic and decides the specific one of those divided areas to which the output of the means 50 is corresponding via a decision means 53 as well as a map 52 where the correction coefficients are previously set in every divided area. The correction coefficient of the area corresponding to the decision result of the means 51 is read by an arithmetic means 54. At the same time, the output that undergone the A/D conversion is corrected based on the correction coefficient and a corrected signal is outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of an A / D converter used in a digital servo controller.

[0002]

2. Description of the Related Art Conventionally, in a digital servo controller, an actuator or the like is driven to a target physical quantity according to a signal from a sensor which converts it into an electric quantity according to a physical quantity, and an analog signal output from the sensor is amplified. After being amplified by, it is converted into a digital signal by the A / D converter. Further, the error contained in this digital signal is corrected, and the target value of the physical quantity is calculated based on this corrected digital signal.

In the A / D converter of the servo controller for correcting the error as described above, as shown in FIG.
The digital signal after D conversion is corrected.

Explaining this, first, a physical quantity Lx at a predetermined measurement point X near the maximum value of the sensor measurement range and a physical quantity Ly at a predetermined measurement point Y near the minimum value of the sensor measurement range are preset. Then, the electric quantities Vx and Vy after A / D conversion according to the maximum value Lx and the minimum value Ly of these physical quantities are measured.

Then, these two points (Lx, Vx), (L
y, Vy) is the straight line connecting the sensor output characteristic lines f (L)
Ask as.

The output characteristic line f (L) of this sensor can be expressed by the following equation from its inclination a (dV / dL) and offset b.

F (L) = aL + b (1) Now, when the A / D converted output V is given, the actual physical quantity L is obtained from the above equation (1) as follows.

L = (V-b) / a (2) Therefore, in the A / D converter of the servo controller,
The correction process of the A / D converted output signal is performed by setting the straight line connecting the physical quantities at the two points and the output values at these two points as the output characteristic straight line.

[0009]

However, in the conventional A / D converter of the servo controller, the maximum value L
Since the straight line connecting x and the electric quantities Lx and Ly at the minimum value Ly is the output characteristic straight line, the error can be corrected only with the uniform inclination a and the offset b over the entire measurement range, and the output characteristic is non-linear. When the sensor is used, there is a problem in that an area where the error cannot be accurately corrected occurs, and the accuracy of servo control deteriorates in this area.

Therefore, the present invention has been made in view of the above problems. Even when a sensor having a non-linear output characteristic is used, the A / A of the servo controller capable of accurately correcting the error over the entire measurement range. It is an object to provide a D converter.

[0011]

As shown in FIG. 7, a first invention is a sensor 1 for outputting an electric quantity according to a physical quantity.
And an A / D conversion of a servo controller including an A / D conversion means 50 for converting an analog signal output from this sensor into a digital signal, and an error correction means 51 for correcting the output of the A / D conversion means 50. In the vessel, the sensor 1
Has a non-linear characteristic, and the error correction means 51 divides the measurement range into a plurality of regions according to the non-linear characteristic, and a map 52 in which a correction coefficient is preset for each region.
A means 53 for determining which of the plurality of areas the output of the A / D conversion means 50 corresponds to, a correction coefficient for the area according to the determination result is read from the map 52, and The calculation unit 54 corrects the output of the A / D conversion unit 50 according to the correction coefficient.

In a second aspect based on the first aspect, the map divides a physical quantity within a measurement range into a plurality of areas, and presets an electric quantity corresponding to a boundary point of each physical quantity area. Then, the calculation means obtains a physical quantity from the output of the A / D conversion means by interpolation calculation.

In a third aspect based on the first aspect, the calculating means includes an origin changing means for adding a predetermined shift amount to the calculation result of the physical quantity to change the origin of the physical quantity.

In a fourth aspect based on the first aspect, the map divides the physical quantity within the measurement range into a plurality of areas according to changes in the inclination of the non-linear characteristic of the sensor. The electric quantity corresponding to the boundary point of the physical quantity region is set in advance, and the arithmetic means changes the arithmetic means for interpolating the physical quantity with a predetermined resolution from the output of the A / D conversion means, and the selection number of the boundary points. And a resolution changing means for changing the resolution.

[0015]

Therefore, according to the first aspect of the present invention, the analog signal from the sensor is converted into a digital signal by the A / D conversion means, and then the digital signal output is corrected by the error correction means before the control section of the servo controller. Sent to. Since the output characteristics of the sensor have non-linearity, the error correction means divides the measurement range into a plurality of areas according to the non-linear characteristics, and based on a map in which the correction coefficient is preset for each area, It is determined which of the plurality of areas the output of the A / D conversion means corresponds to, the correction coefficient of the area corresponding to the determination result is read from the map, and the output of the A / D conversion means is used as the correction coefficient. Since the correction is performed accordingly, it is possible to surely correct the error in the entire area of the measurement range of the sensor having nonlinearity and to ensure the accuracy of servo control.

According to a second aspect of the invention, the map divides the physical quantity within the measurement range into a plurality of areas, presets the electric quantities corresponding to the boundary points of these respective physical quantity areas, and the calculating means sets A Since the physical quantity corrected according to the non-linear characteristic of the sensor is obtained by performing the interpolating operation between the boundary points from the output of the / D conversion means, the non-linearity of the sensor is calculated by the polygonal line approximation in the whole area of the measurement range. Can be corrected.

In the third invention, the origin can be easily moved by adding a predetermined shift amount to the calculation result of the physical quantity.

According to the fourth aspect of the invention, the map is divided into a plurality of physical quantity regions according to changes in the inclination of the non-linear characteristic of the sensor, so that each physical quantity region is set to have a width corresponding to the characteristic of the sensor. . By performing interpolation calculation between the boundary points from the output of the A / D converter, a physical quantity corrected according to the non-linear characteristic of the sensor is calculated, and the physical quantity is corrected by the number of boundaries selected by the resolution switching means. However, by increasing the number of selection of boundary points, it is possible to perform high-precision correction, while by proposing the number of selection of boundary points, the calculation speed is improved and high-speed correction is performed. It can be carried out.

[0019]

1 to 3 show one embodiment of the present invention.

FIG. 1 shows a digital servo controller A.
The block diagram of the / D converter is shown, and 1 is a sensor that changes a physical quantity into an electric quantity. An analog signal from this sensor 1 is converted into a digital signal by an A / D converter 2 and then this digital signal output The corrected value of 1 is sent to the controller of the servo controller (not shown) as the output value of the sensor 1.

The A / D converter 2 includes an A / D converter 3 for converting an analog signal from the sensor 1 into a digital signal.
And a digital signal from the A / D conversion unit 3, and a memory 5 as a storage unit that stores the converted digital signal V and also stores a correction coefficient for each of a number of preset physical quantity regions, as described later. C to correct as described below
It is composed of a PU 4 and an interface (I / O) 6 for sending the calculation result of the CPU 4 or the data of the memory 5 to a control unit of a servo controller (not shown).

Here, an example of the control performed by the CPU 4 will be described in detail with reference to the flowchart of FIG. 2 and the error correction map of FIG.

First, the map shown in FIG. 3 for correcting the output signal V of the A / D converter 3 will be described.

In FIG. 3, the measurement range of the sensor 1 is divided into n areas, and the measurement range of the physical quantity is L ₁
˜L _{n + 1,} and n + 1 points of L _{1 to} L _{n + 1} indicate physical quantities at the boundary points of each area.

Boundary points L _{1 to} L of these physical quantities
The output values of the A / D conversion unit 3 corresponding to _{n + 1} are V _{1 to} V _{n + 1} . The minimum value of the physical quantity is L ₁ and the maximum value thereof is L _{n + 1} .

The polygonal line connecting the boundary points is used as the output characteristic line of the sensor 1. This output characteristic line has a different slope a and offset b in each area.

That is, the sensor 1 in an arbitrary area i
Of the output characteristic line f (L) is the slope a set in the region i.
_{From i} and the offset b _i , it is expressed by the following equation.

F (L) = a _i L + b _i However, (L _i ≦ L ≦ L _{i + 1} ) (3) Here, when an arbitrary output V is given from the A / D converter 3, When the output value V satisfies the measurement range V _i ≦ V ≦ V _{i + 1} , the actual physical quantity L is obtained from the equation (3) as follows.

L = (V−b _i ) / a _i (V _i ≦ V ≦ V _{i + 1} ) (4) Thus, the output value V of the A / D conversion unit 3 is determined according to the corresponding area. It is possible to obtain the physical quantity L in which the error is corrected by the correction coefficients a _i and b _i .

Next, the control operation of the CPU 4 based on the above error correction map will be described with reference to the flowchart of FIG.

First, in step S1, the A / D converter 3
The output value V obtained by converting the analog signal of the sensor 1 is read by.

Next, in step S2, the read output value V, the shown in Figure 3, a number of regions V _i ~V i + ₁ set in advance, determine appropriate which region i To do.

Then, in step S3, the correction coefficient (slope a _i , offset b _i ) of the area i including the output value V is read from the memory 5.

Next, in step S4, the physical quantity L obtained by correcting the output value V from the correction coefficients a _i and b _i corresponding to the output value V and the area i thereof is calculated from the equation (4).

The physical quantity L thus obtained is calculated in step S5.
Then, it is sent to the control unit of the servo controller (not shown) via the interface 6.

Even if the output characteristic of the sensor 1 is non-linear, the output characteristic of the sensor 1 can be approximated by a polygonal line divided into a number of regions by executing the above steps S1 to S5 at a predetermined sampling interval or the like. Therefore, the error can be accurately corrected in the entire measurement range, and the control accuracy can be significantly improved as compared with the conventional example.

FIG. 4 is a map showing the second embodiment, in which the origin (0 point) of the physical quantity L can be moved to an arbitrary position, and other configurations are the same as those in the first embodiment. .

When the control target of the servo controller is, for example, an actuator that makes a linear reciprocating motion, and when it is desired to drive with an arbitrary stroke position as the origin, FIG.
As shown in, the origin of the physical quantity L can be easily moved only by adding a predetermined shift amount s to the offset b _i set in each area i. It should be noted that the shift amount s is stored in the memory 5 or the like in advance, and is appropriately read and added to the offset b _i so that the origin of the physical amount L can be moved at any time, and a large number of shift amounts s are set. A desired shift amount s is selected by a selection unit (not shown).
By selecting, the origin can be moved to an arbitrary position, and one A / D converter 2 can be adapted to a wide range of control targets.

FIG. 5 shows a third embodiment in which the resolution of the A / D converter 2 is variable, and the width of the region of the first embodiment is set according to the inclination of the non-linear characteristic of the sensor 1. The width of the sensor 1 is variable and the switching of the resolution is changed according to the number of selected boundary points. Is set widely.

Now, all the boundary points L _{1 to} L of the physical quantity L
_{When n + 1} is selected, the resolution is high, and the output V of the A / D converter 3 can be corrected to a physical quantity L that substantially matches the non-linear characteristic of the sensor 1, thus realizing highly accurate servo control. can do.

On the other hand, if the number of boundary points to be selected is reduced,
The resolution of the obtained physical quantity L also decreases. For example, if _every other boundary point of the physical quantity L is set as L ₁ , L ₃ , L ₅ , L _n-3 , L _n-1 , L _{n + 1} , the boundary point V for comparison with the output V is set. _Since the number of _{1 to} V _{n + 1} is also halved, the correction calculation can be performed at high speed, and it becomes possible to select the priority of resolution and the priority of control speed, so that one A / D converter 2 can be used. It can be applied to a wide range of controlled objects, and versatility can be further improved.

Further, the width of the region is set narrow in the region where the non-linear characteristic of the sensor 1 is remarkable, while the width is set wide in the region where the sensor is substantially linear, so that the increase of the boundary points can be suppressed. It is possible to correct the physical quantity based on the output V of the / D conversion unit 3 with high accuracy and high speed.

[0043]

As described above, according to the first aspect of the present invention, since the output characteristic of the sensor has a non-linear characteristic, the error correction means divides the measurement range into a plurality of regions according to the non-linear characteristic. At the same time, it is determined which of the plurality of areas the output of the A / D conversion means corresponds to, based on a map in which the correction coefficient is preset for each area, and the correction coefficient of the area according to the determination result. While reading from the map
Since the output of the / D conversion means is corrected according to the correction coefficient,
It is possible to surely correct the error in the entire area of the measurement range of the sensor having nonlinearity, to significantly improve the control accuracy as compared with the conventional example, and to improve the servo control accuracy.

According to a second aspect of the invention, the map divides the physical quantity within the measurement range into a plurality of areas, presets the electric quantities corresponding to the boundary points of these respective physical quantity areas, and the calculating means sets A Since the physical quantity is obtained from the output of the D / D conversion means by interpolation calculation, the non-linearity of the sensor can be corrected for the entire area of the measurement range by the polygonal line approximation, and the control accuracy is greatly improved compared to the conventional example. As a result, the accuracy of servo control can be improved.

In the third invention, the origin can be easily moved by adding a predetermined shift amount to the calculation result of the physical quantity, and the versatility of the A / D converter can be improved.

According to the fourth aspect of the invention, the map is divided into a plurality of physical quantity regions according to changes in the inclination of the non-linear characteristic of the sensor, so that each physical quantity region is set to have a width corresponding to the characteristic of the sensor. By performing interpolation calculation between the boundary points from the output of the A / D converter, a physical quantity corrected according to the non-linear characteristic of the sensor is calculated, and the physical quantity is corrected by the number of boundaries selected by the resolution switching means. According to the above, the accuracy becomes higher, and by increasing the number of boundary points selected, it is possible to perform high-precision correction, while by reducing the number of boundary points selected, the calculation speed is improved and high-speed correction is performed. It is possible to select the priority of resolution and the priority of control speed, one A / D converter can be adapted to a wide range of control targets, and versatility can be further improved. .

[Brief description of drawings]

FIG. 1 is a block diagram of an A / D converter showing an embodiment of the present invention.

FIG. 2 is a flowchart showing an example of processing performed by a CPU.

FIG. 3 is a map showing an example of an error correction calculation and showing a relationship between a physical quantity L and an A / D converter output value V according to each region i.

FIG. 4 is a map of an error correction calculation showing the second embodiment,
The relationship between the physical quantity L and the A / D converter output value V when the origin of the physical quantity L is moved is shown.

FIG. 5 is a map of an error correction calculation showing the third embodiment,
The relationship between the physical quantity L and the A / D converter output value V when the resolution is improved is shown.

FIG. 6 is a map showing a conventional error correction calculation and showing a relationship between a physical quantity and an A / D converter output.

FIG. 7 is a claim correspondence diagram corresponding to any one of the first to fourth inventions.

[Explanation of symbols]

 1 Sensor 2 A / D Converter 3 A / D Converter 4 CPU 5 Memory 6 I / O 50 A / D Conversion Means 51 Error Correction Means 52 Maps 53 Judgment Means 54 Arithmetic Means

Claims (4)

[Claims] 1. A sensor for outputting an electric quantity according to a physical quantity, an A / D conversion means for converting an analog signal output by the sensor into a digital signal, and an error correction for correcting an output of the A / D conversion means. In the A / D converter of the servo controller including means, the sensor has a non-linear characteristic, and the error correction means divides the measurement range into a plurality of areas according to the non-linear characteristic and A map in which a correction coefficient is preset for each, a means for determining which of the plurality of areas the output of the A / D conversion means corresponds to, and a correction coefficient for the area according to the determination result An A / D converter for a servo controller, comprising: an arithmetic unit that reads from a map and corrects the output of the A / D converter according to a correction coefficient. 2. The map divides the physical quantity within the measurement range into a plurality of areas, while presetting the electric quantity corresponding to the boundary point of each physical quantity area, and the computing means sets the A
The A / D converter of the servo controller according to claim 1, wherein the physical quantity is obtained from the output of the / D conversion means by interpolation calculation. 3. The converter of the servo controller according to claim 1, wherein the arithmetic means includes an origin changing means for adding a predetermined shift amount to the calculation result of the physical quantity to change the origin of the physical quantity. . 4. The map divides the physical quantity within the measurement range into a plurality of areas according to the change in the slope of the non-linear characteristic of the sensor, and presets the electric quantity corresponding to the boundary point of each physical quantity area. However, the arithmetic means includes arithmetic means for interpolating a physical quantity with a predetermined resolution from the output of the A / D conversion means, and resolution changing means for changing the resolution by changing the selection number of the boundary points. The A / D converter of the servo controller according to claim 1, further comprising: