JPH0617801B2 - Absolute position detector - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absolute position detector for detecting the absolute position of each axis of a robot or NC machine tool.

2. Description of the Related Art In recent years, robots and NC machine tools require an absolute position detector that does not require a home-return operation to limit the work area and avoid hitting the work when returning from a power outage or emergency stop. .

An example of the above-described conventional absolute position detector will be described below with reference to the drawings.

FIG. 3 shows the structure of a conventional absolute position detector.

In FIG. 3, 1 and 3 are resolvers, 2 is a speed reducer connecting the resolver 1 and the resolver 3 with a reduction ratio of 1 / r, and 4 and 5 are obtained as outputs by passing an alternating current through the excitation windings of the resolvers 1 and 3. An R / D converter that digitally outputs the rotation angles of the resolvers 1 and 3 from the delay of the voltage phase, 6 is an R / D converter 4,
5 is a microcomputer for calculating an absolute position from position data of each of resolvers 1 and 3 obtained from FIG.

FIG. 4 shows the structure of the R / D converter.

In FIG. 4, 7 is an oscillating circuit that oscillates a 4 MHz clock, 8 is a 10-bit counter that counts a 4 MHz clock, 9a and 9b are sine wave tables consisting of a memory in which the data shown in FIG. 5 is written, and 10a. 10,
b is a D / A converter, 11a and 11b are amplifiers, 12
Is a resolver, 13 is a comparator that compares the output value of the resolver 12 at 0V, and 14 is a latch that holds the data of the counter 8 at the output of the comparator.

The operation of the absolute position detector configured as described above will be described below.

The operation of the R / D converter is as follows.
It counts the MHz clock and outputs a value from 0 to 1023. This output is shown in FIG. 6 (a). The output of the counter 8 is converted by the sine wave tables 9a and 9b, and converted by the D / A converters 10a and 10b into two sine waves whose phases are shifted by 90 degrees as shown in FIGS. 6 (b) and (c). It This 2
The two signals are amplified by the amplifiers 11a and 11b, and the resolver 1
2 to the two excitation windings. The output of the resolver 12 is θ from the waveform shown in FIG. 6 (b) as shown in FIG. 6 (d).
The waveform has a delayed phase, and θ changes from 0 to 360 degrees depending on the rotation angle of the rotor of the resolver. In order to obtain the value of θ as a digital value, the output of the resolver 12 is compared with 0V by the comparator 13, converted into a digital wave as shown in FIG. 6 (e), and the data of the counter 8 is risen at the rising edge of this signal. Is held by the latch 14.

The rotational positions of the resolvers 1 and 2 thus formed by the R / D converters 4 and 5 are read by the microcomputer 6 and the absolute position is obtained. As shown in FIG. 7, the processing of the microcomputer 6 first reads the data of the R / D converters 4 and 5 in step 1 and outputs the data of the one having a larger rotation speed (for example, the one connected to the motor) to P1, The position of the resolver after deceleration is set to P2. P in step 2
2 is multiplied by the speed reduction ratio r and divided by the resolution N of the R / D converter (here, N = 2 ¹⁰ = 1024), and the integer part thereof is m. In step 3, the resolution N is added to m obtained in step 2.
The absolute position Pa is obtained by multiplying by and adding P1.

Problems to be Solved by the Invention However, in the above configuration, It was necessary to adjust the positions of the resolver 1 and the resolver 3 accurately, which required a lot of adjustment.

2. Depending on the position of the resolver, if the data changes due to the influence of noise or voltage fluctuation, the absolute position will shift significantly.

In order to solve the problem of 3.2, the reduction ratio was fixed to the optimum value and the number of resolvers was increased to deal with it, but this made the structure more complicated and impossible to incorporate in the robot arm. Is. There were problems such as.

In view of the above problems, the present invention provides an absolute position detector that does not complicate the structure so that it can be incorporated in an arm of a robot or the like and does not require time and effort for adjustment.

Means for Solving the Problems In order to solve the above problems, an absolute position detector of the present invention includes a first resolver and a second resolver provided on a rotary shaft of the first resolver via a speed reducer. Resolver and the first
First and second resolver-to-digital converters (hereinafter R / R) that obtain the absolute position within one rotation from the resolver and the second resolver.
D converter) and a value obtained by multiplying the output value of the second R / D converter by the reduction ratio of the decelerator to obtain the first R / D.
Virtual offset calculation means for calculating the remainder obtained by subtracting the output value of the D converter and dividing by the dispersion power N per rotation of the first and second R / D converters, and the calculation result of the virtual offset calculation means Error determining means for determining whether an error may occur when the absolute position is obtained using the virtual offset value as described above, and the output of the error determining means may cause an error when the absolute position is obtained. When it indicates that there is an absolute position, the absolute position is calculated from the position shift means for moving the first resolver by 1/2 turn and the output values of the first and second R / D converters or the position shift means. And absolute position calculation means.

Operation According to the present invention, the virtual offset value is obtained by the virtual offset calculating means by the above-mentioned configuration, and the first and second
Of the resolver becomes unnecessary, and the absolute position obtained from the virtual offset value and the outputs of the first and second R / D converters by the error determination means may be displaced due to the error. It is possible to detect the time and shift the position to a position not affected by the error by the position shift means to detect the absolute position value without the position shift.

Embodiments An absolute position detector according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an absolute position detector in an embodiment of the present invention. In FIG. 1, reference numerals 21 and 23 are resolvers, 22 is a speed reducer having a reduction ratio of 1 / r, and 24 and 25 are R / D.
The converter 26 is a microcomputer. The above is the same as the configuration of the conventional example.

The operation of the absolute position detector configured as described above will be described below with reference to FIGS. 1 and 2.

The operations of the resolvers 21 and 23 and the R / D converters 24 and 25 are the same as those of the conventional example, but the processing of the microcomputer 26 is, as shown in FIG. Is read and designated as P1 and P2. In step 2, P1 is subtracted from P2 multiplied by the speed reduction ratio r, and the remainder divided by the decomposition N of the R / D converters 24 and 25 is set as the virtual offset value O ₁₂ . In step 3, the case where the virtual offset value O ₁₂ is in the range of N / 4 and 3 × N / 4 is distinguished from the case other than that. Next, in step 3, N / 4 ≦ O ₁₂ 3
If it is N / 4, step 4 is executed. If not, step 5 is executed. Step because when the 4 P1, P2, even using O ₁₂ in the calculation of this state absolute position error does not occur offset value O ₂ = O _1, the shift amount O ₁ = 0, P1 shifts the values P ₁₂ = P1 And go to step 6. At the time of step 5, P1 is shifted by N / 2 and the absolute position is obtained at a place where no error occurs. That is, P ₁₂ is the remainder obtained by adding P1 and N / 2, and the remainder is divided by N. Offset O ₂ is the remainder obtained by subtracting P ₁₂ by subtracting P ₁₂ from P2 multiplied by the reduction ratio r, and O ₁ is the shift amount N. _1/2, and go to step 6. In Step 6 Step 4 or Step results of 5 pull the P ₁₂ multiplied by the reduction ratio r to P2 still pull the O ₂ N _1/2 and r / 2 was added N
Divide by and make the integer part m The absolute position Pa is obtained by multiplying m by N, adding P _12, and adding O ₁ .

As described above, according to the present embodiment, the virtual offset calculating means for obtaining the virtual offset value in step 2, step 3
By providing the error determining means for determining the presence or absence of an error in step 1 and the position shifting means for shifting the position by N / 2 in step 5, it is possible to obtain an absolute position without positional deviation without changing the configuration of the conventional example.

In the present embodiment, the N / 2 shift is performed by the calculation of the microcomputer 26. However, when the resolver 21 is connected to the motor, the 1/2 rotation motor may be rotated.

As described above, according to the present invention, by providing the virtual offset calculation means, the error determination means and the position shift means, it is necessary to adjust the position of the resolver and to measure the displacement of the resolver in advance with a minimum configuration. It is possible to perform absolute position detection without any error.

[Brief description of drawings]

FIG. 1 is a block diagram of an absolute position detector in an embodiment of the present invention, FIG. 2 is a flowchart of processing contents of the microcomputer of FIG. 1, FIG. 3 is a block diagram of a conventional example, and FIG. FIG. 5 is a configuration diagram of the D converter, FIG. 5 is an explanatory diagram of a sine wave table, FIG. 6 is a waveform diagram of each part of the R / D converter, and FIG. 7 is a flowchart showing processing contents of a microcomputer of a conventional example. . 21, 23 ... Resolver, 22 ... Reducer, 24, 25
...... R / D converter, 26 …… Microcomputer.

Claims (1)

[Claims] 1. A first resolver, and a second resolver provided on a rotating shaft of the first resolver via a speed reducer,
First and second resolver / digital converters (hereinafter referred to as R / D converters) for obtaining an absolute position within one rotation from the first resolver and the second resolver, and the second R / D converter. Of the first R / D converter is subtracted from the product of the output value of ## EQU1 ## and the reduction ratio of the decelerator, and the output value of the first R / D converter is subtracted.
Error when an absolute position is obtained using virtual offset calculation means for calculating the remainder divided by the resolution N per rotation of the R / D converter and the virtual offset value as the calculation result of the virtual offset calculation means. The error resolver that determines whether or not the error may occur and the output of the error determiner indicates that the error may occur when the absolute position is obtained. Absolute position detection, comprising position shift means for rotational movement, and absolute position calculation means for calculating an absolute position from output values of the first and second R / D converters or the position shift means. vessel.