JPH0247449Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in angle measuring devices such as theodolites.

Conventionally, as a device for measuring angles without using a scale, for example, the US
ARMYEngineerTopographicLaboratories
Some are reported in ReportETL-TR-72-1.

This angle measuring device measures the time T1 required for a slit provided on the circumferential surface of a constant-velocity rotating body to rotate once relative to a fixed reference point, and the time required for the slit to rotate from that reference point to the angle measurement point. Time required for T2
The angle is found by calculating 360° x (T2/T1).

The angle measuring device as described above is characterized in that measurement is easy because it does not require a scale, and its configuration is also simple.

The same report also mentions so-called 180° opposing reading in order to compensate for errors caused by eccentricity between the center of rotation of a constant-velocity rotating body and the center of rotation of an angle measurement point.

In the method described in the same report, the constant rotation performance of the rotating body in one revolution greatly affects the angle measurement accuracy. Therefore, in order to maintain high angle measurement accuracy, considerable care must be taken to ensure that the constant speed rotation performance of the motor that drives the rotating body does not fall below a predetermined value.

If there is one period of rotational unevenness during one rotation of the rotating body, the adverse effect tends to be canceled if 180° opposing reading is used. On the other hand, as a result of our experiments using the method described in the same report, we found that there are two periods of rotational irregularity for one rotation of the rotating body in the feedback detection system for motor or rotational control. Therefore, in terms of angle measurement accuracy, a two-period error curve is generated, and this error remains without being canceled even if 180° facing reading is adopted.

The present invention has been developed by focusing on the above-mentioned conventional problems, and eliminates the two-cycle rotational irregularity that occurs during one rotation of a rotating body by using a simple configuration and without increasing the number of detection units. It is an object of the present invention to provide a device capable of making corrections.

In order to achieve this object, the present invention provides two detected parts at different positions on the circumference of a constant velocity rotating body in the above-mentioned type of angle measuring device, and uses these two detected parts to Find time T1 and T2,
The angle to be measured is calculated from these times.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings. FIG. 1 is a plan view showing an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view taken along the line - in FIG.

The rotating body 1 is composed of two discs 1a and 1b, and is rotated at a constant speed by a motor 3 via a rotating shaft 1c, and the rotating shaft 1c is a non-movable part of the angle measuring device. It is pivotally supported by a certain board 2. The rotation axis of the collimating arm 4 is set to substantially coincide with the rotation axis 1c. A collimating telescope (not shown) is fixed to the collimating arm 4, so that the angle of the collimating telescope and the angle of the collimating arm 4 match.

Further, on the substrate 2, there is a reference point R as a reference.
1 and R2 are provided, and these reference points R1 and R2 each have a pair of light emitting element and light receiving element. Further, on the outer circumference of the disc 1b constituting the rotating body 1, there is a slit facing in the radial direction of the rotating shaft 1c.
SR1 and SR2 are provided, and these slits SR1,
As the rotating body 1 rotates, SR2 passes through an optical path from the light emitting element to the light receiving element that constitutes the reference points R1 and R2. Then, when the rotating body 1 is rotating, the slit
When SR1 and SR2 pass through these optical paths, each light receiving element generates a pulse. Slits SR1 and SR2
Although they are installed at approximately 90° intervals, they may be installed at other angles.

On the other hand, angle measurement points M1 and M2 are provided at both ends of the collimating arm 4. At these angle measurement points M1 and M2, a set of a light emitting element and a light receiving element is provided, respectively, similarly to the reference points R1 and R2. These light-emitting elements and light-receiving elements face each other across the disc 1a, and each time the slits SM1 and SM2 provided in the disc 1a pass through the angle measurement points M1 and M2, A pulse is generated. Also, slit SM1 and SM2
They are placed approximately 90 degrees apart.

Furthermore, the slits SM1 and SR1 are located at the same position in the circumferential direction and the radial direction.
2 and SR2 are both in the same position. Therefore, although there are actually four slits, two of them are facing each other, and since there are only two optically equivalent slits, there are actually two slits in total. is the same as That is, these slits SM1, SM2 and SR1, SR2 are separately provided for the angle measurement points M1, M2 and for the reference points R1, R2. Two identical slits can be used for each. Also, Slits SM1 and
The angular interval with SM2 may be an angle other than 90°, and the exact value of the angular interval between slits SR1 and SR2 may not be known.

FIG. 3 shows an example of the circuit used in the above embodiment, and FIG. 4 is a time chart showing the signal waveforms of the main parts of FIG.

Here, to improve measurement accuracy, counter reading (for example, the time it takes for a certain slit to move from one reference point to the next angle measurement point, and the time it takes for a slit to move from the remaining reference points to the remaining angle measurement points) However, the following explanation will be given for only one method. That is, each disk 1
Two slits are used for each of a and 1b, but the explanation will be given assuming that only R1 is used as a reference point and only M1 is used as an angle measurement point. When performing opposite reading, it is sufficient to further measure the reference point R2 and the angle measurement point M2 based on the following explanation, perform a predetermined calculation, and then take the average of both.

In FIG. 3, the R1 output signal is the output signal of the light receiving element at the reference point R1, and the M1 output signal is the output signal of the light receiving element at the angle measurement point M1. Also,
The measurement start signal is a signal output from a microcomputer or the like to start angle measurement.

The D flip-flop 5 divides the R1 signal by one stage while receiving the measurement start signal.
The D flip-flop 6 similarly divides the M1 signal by one stage. Further, the RS flip-flop 7 is set at the rising edge of the non-inverted output signal of the D flip-flop 5, and reset at the rising edge of the non-inverted output signal of the D flip-flop 6. Furthermore, the RS flip-flop 8 is
It is set by the transistor at the rising edge of the inverted output signal of the D flip-flop 5, and the output signal of the D flip-flop 6 is
It is reset by the rising edge of the inverted output signal. The D flip-flop 9 inputs the non-inverted output signal of the D flip-flop 5 and calculates the time from when the slit SR1 passes the reference point R1 until the next time when the same slit SR1 passes, that is, the time for one rotation of the rotating body 1. It outputs pulses for a certain period of time.

Further, the counter 14 is counted while the RS flip-flop 7 is outputting, that is, the slit SR1
The clock pulses are counted from when the slit SM1 passes the reference point R1 until the slit SM1 passes the angle measurement point M1. counter 15
is, while the RS flip-flop 8 is outputting,
That is, clock pulses are counted from the time when the slit SR2 passes the reference point R1 until the time when the slit SM2 passes the angle measurement point M1. The counter 16 counts the number of pulses corresponding to the time that the rotating body 1 makes one rotation.

The microcomputer 17 has a counter 14,
15 outputs are added, the average is taken, and this time is set as T2, and the output of the counter 16 is set as T1, 360°×(T2/T1) is calculated. The result of this calculation is the angle measurement value. Note that the reference numeral 10 is a clock signal generation circuit, and the reference numerals 11 and 1 are
2 and 13 are AND circuits.

Figure 5 shows that when the angle is measured as described above,
This shows the principle of compensating for measurement errors at that time. For example, if the slit spacing is 90°,
This is an error curve obtained by measuring a 90° angle at each position of the theodolite. Here, the solid line curve is an error curve according to the conventional method (in FIG. 3, it is an error curve that occurs when measurement is performed without using the RS flip-flop 8, the AND circuit 12, and the counter 15; 11 and the counter 14). In addition, the broken line curves in the figure are the second slits SR2 and SM.
Error curve when measuring using 2 (in Figure 3, RS flip-flop 8, AND circuit 1
2 and the counter 15).

By the way, the embodiment shown in Figs.
The measurement is performed by adding the solid line error curve and the broken line error curve in the figure, and the phases of these two curves are shifted by 90 degrees. For this reason, the error at that time can ideally be reduced to zero.

Moreover, FIG. 6 shows a case where the phase of the R1 output signal is slightly delayed from the phase of the M1 output signal, and compared to the case of FIG. 4, the phase relationship between the R1 and M1 output signals is reversed. This is a time chart showing the case. At this time, if the respective outputs of the counters 14 and 15 are simply averaged and divided by 2, the measured angle value will be different from the actual value. Therefore, when the contents of the counter 15 are larger than the contents of the counter 14 by a predetermined value or more, the counters 14 and 1
After adding the contents of 5 and dividing by 2, you can add 180 degrees, and by doing this, you can obtain the true angle value. In order to deal with such a case, a routine incorporating the above method may be added to the program of the microcomputer 17.

Although it is important to set the timing to generate the measurement start signal shown in Figure 4, since the R1 output signal is generated at irregular intervals, this property can be used to measure the angle. The above-mentioned timing can be appropriately obtained by the prior art in the previous stage. This may be accomplished by using a separate circuit or by using the microcomputer 50 to obtain the timing.

As mentioned above, compared to conventional angle measuring devices, the present invention is mechanically capable of sufficiently eliminating two periods of rotational unevenness in one rotation of the rotating body by simply adding one slit to the rotating body. Since it can be corrected, it has the effect that highly accurate angle measurement can be performed.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing one embodiment of the present invention;
The figure is a vertical sectional view taken from the - line in Figure 1, Figure 3 shows an example of the circuit used in the above embodiment, Figure 4 is a time chart of the above embodiment, and Figure 5 is a diagram of the present invention. A diagram showing the principle, FIG. 6 is a diagram showing another time chart in the above embodiment. DESCRIPTION OF SYMBOLS 1... Rotating body, 1a, 1b... Disk, 2... Board, 3... Motor, 4... Collimation arm, 5, 6...
...D flip-flop, 7, 8...RS flip-flop, 10...clock signal generation circuit, 1
4, 15, 16...Counter, 17...Microcomputer, R1, R2...Reference point as a detection point, M1, M2...Angle measurement point as a detection point, SR1, SR2, SM1, SM2...Target Slits as detection points.

Claims (1)

[Scope of utility model registration request] The time T1 required for a detected part provided on the circumference of a constant-velocity rotating body to rotate once with respect to a fixed reference point, and the time required for the detected part to rotate between the reference point and the angle measurement point. Find time T2 and calculate 360°×(T2/
In an angle measuring device that calculates a measured angle by calculating T1), two detected parts are provided at different positions on the circumference of the constant velocity rotating body, and these two
An angle measuring device that obtains the above-mentioned times T1 and T2 using two detected parts and calculates a measured angle from these times.