JPH07103707A - Position detector for actuator - Google Patents

Abstract

PURPOSE:To obtain a detector which makes accurate measurement possible by making a compensation from a non-linear position signal indicating the position of a magnet to be outputted from a magnetic sensor to a linear position signal proportional to the position of the magnet. CONSTITUTION:When a position detection signal from a magnetic sensor 5 is linear with the position of a magnet 3, a linear position detection signal inputted into a CPU of a data processing circuit 7 is not subjected to compensation for temperature and a non-linear area and the position of the magnet 3 proportional to the position signal is determined. When the position detection signal from the magnetic sensor 5 is nonlinear with the position of the magnet 3 and in such a wide range as to require a non-linear compensation, a program for positional compensation is read out of an RAM of the CPU to perform a computation based on a correction data included in the ROM according to the program. As a result, a compensation is performed from the position detection signal to a linear signal proportional to the position of the magnet 3. Thereafter, it is judged according to the position detection signal subjected to the compensation whether the detection of the position is possible or a moving part of an actuator is within a measuring range or not.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to detecting the position of a linear movement actuator, and more particularly to detecting the position or distance from a reference plane of linear movement of a piston of an actuator such as a cylinder operated by air pressure or the like. Regarding the device.

2. Description of the Related Art The applicant has proposed a device in which a position detecting device is applied to a pneumatic cylinder. FIG. 3 is an overall configuration diagram thereof. In FIG. 3, the pneumatic cylinder 1 is supplied with pneumatic pressure via a solenoid valve (not shown), and the cylinder piston 2 linearly moves in the X or Y direction in the figure. A magnet 3 is attached to the tip of the cylinder piston 2. The magnet 3 may be a magnet used for a proximity switch, for example. Also, the cylinder piston 2
A magnetic sensor 5 is attached to the cylinder body 4 which is fixed to the movable part of. The magnetic sensor 5 is housed in a case 6 to protect it from vibration and dust. The magnetic sensor 5 is configured as a bridge, and changes in the strength of the magnetic field are extracted as an electric signal by utilizing the property that the four magnetostrictive elements forming the bridge change their resistance in proportion to the strength of the magnetic field. There is. This magnetic sensor 5
The output from is sent to the data processing circuit 7 where the required data processing is performed. FIG. 4 is a diagram showing the relationship between the signal level output from the magnetic sensor 5 and the position of the cylinder piston 2. The position of the magnetic sensor 5 is C, and when the position of this C, that is, the magnet 3 is on the same straight line as the magnetic sensor 5, the magnetic field from the magnetic sensor 5 is not detected, and its output becomes zero. In FIG. 3, when the positions A, B, D, and E are defined from the position C in the X and Y directions, the signal level output from the magnetic sensor 5 when the magnet 3 reaches each position is a in FIG. , B, d, e respectively. As a result, as the cylinder piston 2 moves, a locus of a signal level point-symmetrical with respect to the position C shown by the solid line in FIG. 4 is output. Focusing on FIG. 4, it can be seen that when the magnet 3 is in the range BD centered on the position C, the magnetic sensor 5 outputs a position signal of a level proportional to the position of the magnet. Focusing on this fact, as shown in FIG. 5, only a region BD that linearly changes in the signal output from the magnetic sensor 5, that is, a specified region of a part of the stroke of the cylinder piston 2 is set as a measurement region. To use. Therefore, the signal level of the linear region BD output from the magnet 5 directly indicates the position of the magnet 3. The setting of the measurement range in the case of detecting whether the thickness of the inspection object 8 whose one surface is in close contact with the surface plate 9 is within the allowable range according to the moving distance of the cylinder piston 2 shown in FIG. 3 is as follows. To First, the magnet 3 of the cylinder piston 2 is aligned with the position of the magnetic sensor 5, that is, the position C, and the cylinder piston 2 is finely adjusted to confirm the position C where the position detection signal becomes zero. Next, the cylinder piston 2 is moved in the X direction to the upper limit position D of the tolerance measured based on the position C, and the position detection signal at this time is set as the upper limit position D. Similarly, the cylinder piston 2 is moved in the Y direction to the lower limit position B of the tolerance based on the position C, and the position detection signal at this time is set as the lower limit position B. Then, by moving the cylinder piston 2 in the X direction and detecting the position where it collides with the inspection object 8 as a position signal by the magnetic sensor 5, it is within the thickness tolerance of the inspection object 8, that is, within the measurement range BD. Whether it is in or not is automatically displayed.

It has been found that the position detecting device manufactured on the basis of the above knowledge has the following problems. That is, in FIG. 4, when the measurement range for detecting the position of the magnet 3 is increased, the position signal output from the magnetic sensor 5 as shown in FIG. 6 is not necessarily linear as described above and is proportional to the position of the magnet. It was found to include an error d from the expected virtual linear level. This error is a size that cannot be ignored because it increases the measurement error after digital processing in the measurement range of a certain length or longer, and some kind of compensation was required to perform highly reliable and accurate measurement. Further, in the above-described position detecting device, when the measurement range is increased, the output characteristics of the magnetic sensor also change when the measurement temperature changes, as shown in FIG.
The signal level output from the device decreases as the temperature increases.
Therefore, it is necessary to compensate the position signal output from the magnetic sensor 5 so as to be proportional to the position of the magnet according to the measured temperature. An object of the present invention is to widen the measurement range for detecting the position of a magnet and, when a magnetic sensor outputs a position signal that is non-linear with the position of the magnet, compensate for the position signal so as to be proportional to the position of the magnet. It is an object of the present invention to provide a position detecting device capable of performing good measurement of It is another object of the present invention to provide a position detecting device capable of performing accurate measurement by compensating for the influence of temperature when the position signal from the magnetic sensor changes due to the influence of measurement temperature. It is another object of the present invention to compensate for the influence of temperature when the magnetic sensor outputs a position signal that is non-linear with the position of the magnet and the position signal changes due to temperature, and to move the position signal to the position of the magnet. An object of the present invention is to provide a position detecting device capable of performing accurate measurement by performing proportional compensation.

SUMMARY OF THE INVENTION According to the present invention, an actuator, a magnet provided on a movable part of the actuator which moves linearly, and a fixed position of the actuator are provided, and a fluctuation of a magnetic field of the magnet is converted into an electric signal. A magnetic sensor that outputs differently and outputs a non-linear position signal corresponding to the position of the magnet when the magnet exists in a position of a specific range, and a specific region of the non-linear analog position signal output from the magnetic sensor is measured. A measuring range setting means for setting the range, an analog / digital converter for converting an analog position signal output from the magnetic sensor within the measuring range set by the measuring range setting means into a digital position signal, and the digital position Area compensation means for compensating the digital position signal so that the signal is proportional to the position of the magnet;
According to the digital position signal compensated by the area compensating means, there is provided a detecting means for detecting a position of the movable part of the actuator in the measurement range or whether or not the movable part of the actuator is in the measurement range.
Further, according to the present invention, an actuator, a magnet provided on a movable part of the actuator which moves linearly, and a magnet provided on a fixed position of the actuator are provided to convert the magnetic field of the magnet into an electric signal and output the electric signal. A magnetic sensor which outputs a position signal corresponding to the position when the position is in a position of a specific range, and a measurement range setting unit which sets a specific region of the analog position signal output from the magnetic sensor as a measurement range, An analog position signal output from a temperature sensor provided at a fixed position of the actuator in the vicinity of the magnetic sensor and the magnetic sensor within the measurement range set by the measurement range setting means is converted into a digital position signal. An analog / digital converter and the digital position signal into a digital position signal at a reference temperature Temperature compensating means for compensating based on the temperature output from the temperature sensor, and the position within the measuring range of the movable part of the actuator or the movable part of the actuator is measured according to the digital position signal compensated by the temperature compensating means. The present invention further comprises detection means for detecting whether or not it is within a range, and an actuator, a magnet provided on a movable part of the actuator that moves linearly, and a magnet provided on a fixed position of the actuator. A magnetic sensor that outputs the magnetic field fluctuation of the magnetic field to an electric signal and outputs a position signal that is non-linear with the position when the magnet is in a position in a specific range; and an analog position signal that is output from the magnetic sensor. A measuring range setting means for setting a specific region as a measuring range, and a fixed position of the actuator. A temperature sensor provided in the vicinity of the magnetic sensor, an analog / digital converter for converting an analog position signal output from the magnetic sensor within the measurement range set by the measurement range setting means into a digital position signal, A region / temperature compensating means for correcting the digital position signal into a digital position signal at a reference temperature according to the temperature signal output from the temperature sensor, and further compensating the digital position signal in proportion to the position of the magnet; According to the digital position signal compensated by the area / temperature compensating means, there is provided a detecting means for detecting the position of the movable part of the actuator in the measurement range or whether the movable part of the actuator is in the measurement range. .

According to the present invention, since the non-linear position signal indicating the position of the magnet output from the magnetic sensor is compensated to the linear position signal proportional to the position of the magnet, the region compensating means is provided. By determining the compensated position signal, it is possible to accurately detect the position of the magnet or whether the magnet is within the measurement range. Further, according to the present invention, a temperature sensor is provided in the vicinity of the magnetic sensor, and the temperature compensating means for compensating the position signal output from the magnetic sensor to the position signal at the reference temperature based on the temperature signal output from the temperature sensor. Since it is provided, it is possible to accurately detect the position of the magnet or whether the magnet is within the measurement range. Further, according to the present invention, the position signal of the magnet output from the magnetic sensor is corrected to a digital position signal at a reference temperature according to the temperature signal output from the temperature sensor, and the digital position signal is proportional to the position of the magnet. Since the area / temperature compensation means for compensation is provided, it is possible to accurately detect the position of the magnet or whether the magnet is within the measurement range.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure shown in FIG. 3 can be applied to the position detecting device of the present invention. In the present invention, a temperature sensor 11 is provided near the magnetic sensor 5, and the output of the temperature sensor 11 is the data processing circuit 7. Given to. The temperature sensor 11 is composed of, for example, a temperature sensor IC and may be integrated with the magnetic sensor 5. FIG. 1 is a block diagram showing an embodiment of a data processing circuit 7 of the present invention. In FIG. 1, the position detection signal of the cylinder piston 2 output from the magnetic sensor 5 and the temperature signal output from the temperature sensor 11 are both sent to a waveform shaping circuit 71, where noise and the like are removed and shaped. , A / D (analog / digital) converter 72. The position detection signal and the temperature signal converted into digital signals by the A / D converter 72 are given to a CPU (central processing unit) 73. CPU7
3 may include a comparison / determination circuit 73a, and the comparison / determination circuit 73a may be operated by receiving a measurement instruction command from the outside. A measurement range reference signal is input from the measurement range setting circuit 74 to the comparison / discrimination circuit 73a. The measurement range setting circuit 74 specifies a required measurement range of the position detection signal output from the magnetic sensor 11, and an upper limit setting circuit 74a that sets an upper limit value of the measurement range and a lower limit setting that sets a lower limit value. Circuit 74b is provided. The signals indicating the upper limit value and the lower limit value set by the measurement range setting circuit 74 are given to the comparison / determination circuit 73a. The comparison / determination circuit 73a includes a waveform shaping circuit 71, A /
The level of the position detection signal input via the D converter 72 is compared with the upper limit value and the lower limit value, and the signal level of the position detection signal exceeds the upper limit value, is below the lower limit value, or is within the measurement range. It is determined whether or not there is, and the determination result is output to an external device and displayed on the display circuit 75. Further, the measurement range setting circuit 74 displays and outputs the designated measurement range, that is, the upper limit value and the lower limit value to the display circuit 75. The display circuit performs a required display according to the instruction, for example, whether or not the detected position signal is within the measurement range. The position of the position detection signal within the measurement range, that is, the position of the cylinder piston may be displayed. The CPU 73 includes an arithmetic circuit 73 in addition to the comparison / discrimination circuit 73a.
b, a ROM 73c, a RAM 73d, and a control circuit 73e. The ROM 73c stores data for linearly correcting the non-linear position detection signal so that the position detection signal from the magnetic sensor 5 represents the position of the magnet 3, in other words, the position detection signal is linear with the position of the magnet. A program for position compensation is stored. A calculation technique for linearly compensating for non-linear data such as the position detection signal is generally known, and is obtained by subdividing the waveform of the position detection signal and calculating correction data obtained from an experiment step by step. Furthermore, temperature compensation data is stored in the ROM 73c in order to compensate for variations in the position detection signal due to temperature. This temperature compensation data is obtained by subdividing the waveform of the position detection signal, and obtaining the ratio of each position detection signal displaced by the temperature change to the reference position (reference temperature) reference position detection signal for each section. It represents the ratio obtained from the experimental results for each temperature. Arithmetic circuit 73b
Compensates the position detection signal in accordance with the data and program stored in the ROM 73c, and performs calculation so that the position detection signal becomes linear with the position of the magnet 5. The control circuit 73e controls the entire CPU 73. CP
Various data can be set in the ROM 73c of the U73 and programs can be stored by the input device 76 such as a keyboard. Next, a usage mode of the position detecting device of the present invention using the data processing circuit 7 of FIG. 1 will be described.
The measurement range setting circuit 74 is a narrow range that does not require compensation,
That is, when the position detection signal from the magnetic sensor 5 is linear to the position of the magnet 3, the linear position detection signal input to the CPU 73 is obtained by the CPU 73 at the position of the magnet 5 which is proportional to the position signal. There is no compensation in the non-linear region. When the measurement range setting circuit 74 is in a wide range requiring non-linear compensation, that is, when the position detection signal from the magnetic sensor 5 is non-linear with the position of the magnet 3, the CPU 73 R
A program for position compensation is sent from the OM 73c to the control circuit 73.
The operation according to the program read out to the ROM 73
As a result of the correction data stored in c, the position detection signal is compensated into a linear signal proportional to the position of the magnet. Thereafter, according to the compensated position detection signal, position detection or determination as to whether or not the movable part of the actuator is within the measurement range (whether or not the position of the magnet is within the set measurement range) is performed. When the position detection signal from the magnetic sensor 5 fluctuates according to the temperature, the magnetic sensor 5 and the temperature sensor 11 pass through the A / D converter 72 to the CPU 7
The position detection signal and the temperature signal input to 3 perform the following temperature compensation. That is, in the CPU 73, temperature compensation data corresponding to the temperature of the input temperature signal and corresponding to the section of the position detection signal to be compensated is read from the ROM 73c, and the position detection signal of the section is multiplied to obtain the temperature for each section. Calculate the compensated reference temperature position signal. After that, according to the temperature-compensated reference position detection signal, position detection or determination as to whether or not the movable part of the actuator is within the measurement range (whether or not the magnet position is within the set measurement range) is performed. When the position detection signal from the magnetic sensor 5 changes according to the temperature and the position detection signal is non-linear with the position of the magnet, the following temperature / region compensation is performed. That is, the CPU 73
, The temperature compensation data corresponding to the temperature of the input temperature signal and corresponding to the section of the position detection signal to be compensated is read from the ROM 73c, multiplied by the position detection signal of the section, and temperature-compensated for each section. A reference temperature position signal is calculated. Next, a program for position compensation is read from the ROM 73c of the CPU 73 to the control circuit 73e, and the calculation according to the program is performed on the reference temperature position signal based on the correction data stored in the ROM 73c. The reference temperature position signal is compensated into a linear signal proportional to the magnet position. Thereafter, according to the temperature-compensated and region-compensated position detection signal, it is determined whether or not the position detection or the movable part of the actuator is within the measurement range (whether the magnet position is within the set measurement range). Be seen. The above-mentioned area compensation is automatically performed for a set measurement range that is equal to or larger than a certain range in which the position detection signal becomes non-linear. Further, the temperature compensation may be configured to be performed together with the region compensation, or may be configured to perform the temperature compensation alone or together with the region compensation by giving a temperature compensation instruction from the outside. Next, a preferred application example of the position detecting device for the actuator including the above-mentioned area / temperature compensating means will be described with reference to FIG. FIG. 2 shows a device (commonly called a hand) (commercially available) for gripping an object by using air pressure. In this device, when air is supplied from the port A, the chamber 20 is filled with air and the piston 21 moves to the right in FIG. 5, and when air is supplied to the port B, the piston 21 moves to the left. Piston 2
1, a rod 22 is connected, and the rod 22 is connected to two arms 24 by an operating shaft 23. The arm 24 rotates about a support shaft 25, and this movement is transmitted to an operating shaft 26 fitted in a notch of the arm 24.
This operating shaft 26 is connected to the master jaw 27,
Although the rotational movement is transmitted to the master jaw 27, the master jaw 27 performs only the vertical movement indicated by the arrow in FIG. 2 by a bearing guide (not shown). That is, the master jaw 27 opens in conjunction with the right movement of the piston 21, and the master jaw 27 closes in conjunction with the left movement. The object to be measured is held between the two master jaws 27. In the apparatus of FIG. 2, the magnet 3 is attached to the piston 31, and the magnetic sensor 5 for detecting the position of the magnet 3 and the temperature sensor 11 for detecting the temperature of the magnetic sensor 5 are provided in the cylinder body 28. It is arranged at the required position. The outputs from the magnetic sensor 11 and the temperature sensor 12 are given to the above-mentioned data processing circuit 7, and the above-mentioned operation is performed. In the apparatus of FIG. 2, the position of the magnet 5 that moves linearly with the piston 21 is directly detected.
The opening of the master jaw 27, that is, the size of the object to be measured held by the master jaw 27, is shown. Therefore, as in the device shown in FIG. Whether or not it can be detected. When the present invention is applied to this hand type device, it can be used as two, for example, a transfer hand for dimensional inspection of machined products and an automatic inspection device, and its application range is wide.

As described above, the present invention includes the area compensating means for compensating the non-linear position detection signal indicating the position of the magnet output from the magnetic sensor into the linear position signal proportional to the position of the magnet. Therefore, even if the measurement range is widened and the position detection signal is not proportional to the position of the magnet, it is possible to compensate for the linear position detection signal by the area compensating means.
Therefore, the measurement accuracy can be remarkably improved as compared with the conventional device. Further, according to the present invention, a temperature sensor is provided in the vicinity of the magnetic sensor, and the temperature compensating means for compensating the position signal output from the magnetic sensor to the position signal at the reference temperature based on the temperature signal output from the temperature sensor. Since it is provided, it is possible to detect with high accuracy regardless of changes in temperature. Further, according to the present invention, the position signal of the magnet output from the magnetic sensor is corrected to a digital position signal at a reference temperature according to the temperature signal output from the temperature sensor, and the digital position signal is proportional to the position of the magnet. Since the area / temperature compensating means for compensating is provided, the measuring range is widened and the position detection signal is not proportional to the position of the magnet, and whether or not the position of the magnet or the magnet is within the measuring range regardless of the temperature change. Can be detected accurately. Further, the present invention, by using the hand as in the embodiment, it is possible to simultaneously perform the conventional inspection process in a machining line or the like at the same time as it is conveyed by the hand, simplifying the process and shortening the line, It can greatly contribute to cost reduction.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a data processing device of a position detecting device of the present invention.

FIG. 2 is a plan sectional view showing a preferred application example of the present invention.

FIG. 3 is an overall configuration diagram showing an example of a position detection device to which the present invention can be applied.

FIG. 4 is a diagram showing a relationship between a moving distance of a magnet and a level of a position detection signal by a magnetic sensor.

FIG. 5 is a diagram showing a linear region of a position detection signal.

FIG. 6 is a diagram showing that the position detection signal includes a non-linear region.

FIG. 7 is a diagram showing a relationship between a temperature change and a level of a position detection signal by a magnetic sensor.

[Explanation of symbols]

 1 Pneumatic Cylinder 2 Cylinder Piston 3 Magnet 5 Magnetic Sensor 7 Data Processing Device 11 Temperature Sensor 73 CPU 73a Comparison / Discrimination Circuit 73b Arithmetic Circuit 73c ROM 73d RAM 73e Control Circuit 74 Measuring Range Setting Circuit 75 Display Circuit

Claims (3)

[Claims] 1. An actuator, a magnet provided on a movable part of the actuator which moves linearly, and a magnet provided on a fixed position of the actuator, which converts a magnetic field variation of the magnet into an electric signal and outputs the electric signal. A magnetic sensor that outputs a non-linear position signal corresponding to a position within a position of a specific range, and a measurement range setting means that sets a specific region of the non-linear analog position signal output from the magnetic sensor as a measurement range. An analog / digital converter for converting an analog position signal output from the magnetic sensor within the measurement range set by the measurement range setting means into a digital position signal; and the digital position signal is proportional to the position of the magnet. Area compensation means for compensating the digital position signal, and a digital position signal compensated by the area compensation means. Position detecting device for a linear movement actuator, comprising a detecting means for detecting a position of the movable part of the actuator in the measurement range or whether the movable part of the actuator is in the measurement range according to the above item. 2. An actuator, a magnet provided in a movable part of the actuator which moves linearly, and a magnet provided in a fixed position of the actuator, which converts the magnetic field variation of the magnet into an electric signal and outputs the electric signal. A magnetic sensor that outputs a position signal corresponding to a position within a specific range position, a measurement range setting unit that sets a specific region of the analog position signal output from the magnetic sensor as a measurement range, and the actuator. A temperature sensor provided at a fixed position in the vicinity of the magnetic sensor,
An analog / digital converter for converting an analog position signal output from the magnetic sensor within the measurement range set by the measurement range setting means into a digital position signal;
Temperature compensating means for compensating the digital position signal into a digital position signal at a reference temperature based on the temperature output from the temperature sensor; and the movable part of the actuator according to the digital position signal compensated by the temperature compensating means. A position detecting device for a linear movement actuator, comprising detection means for detecting a position within a measurement range or a movable part of the actuator within the measurement range. 3. An actuator, a magnet provided on a movable part of the actuator which moves linearly, and a magnet provided on a fixed position of the actuator, which converts a magnetic field variation of the magnet into an electric signal and outputs the electric signal. A magnetic sensor that outputs a position signal that is non-linear with the position when the position is within a specific range, a measurement range setting unit that sets a specific region of the analog position signal output from the magnetic sensor as a measurement range, and the actuator. A temperature sensor provided at a fixed position in the vicinity of the magnetic sensor,
An analog / digital converter for converting an analog position signal output from the magnetic sensor within the measurement range set by the measurement range setting means into a digital position signal;
Area / temperature compensating means for correcting the digital position signal into a digital position signal at a reference temperature according to a temperature signal output from the temperature sensor, and further compensating the digital position signal so as to be proportional to the position of the magnet, and the area. A straight line comprising detection means for detecting the position of the movable part of the actuator in the measuring range or whether the movable part of the actuator is in the measuring range according to the digital position signal compensated by the temperature compensating means Position detector for moving actuator.