JPS61294509A - Absolute position detector - Google Patents

Abstract

PURPOSE:To detect an accurate absolute position by using an original point pulse encoder which produces only the original point pulse from an arm driving motor for an industrial robot via a transmission. CONSTITUTION:An absolute position detector is provided with a drive means 61 for an object 2 to be driven, a pulse generator 9 for detection of relative revolving angle connected to the means 61, an original point pulse encoder 41, a pulse count means 17, the 1st and 2nd original point pulse detection means 61 and 63 and an absolute position arithmetic means 64. When the generator 9 produces an original point pulse, a signal is sent to the means 64 from the means 62. At the same time, the means 17 starts counting pulses. While a signal is sent to the means 64 from the means 63 when the encoder 41 produces an original point pulse. Thus the pulse counting operation is through. The difference is calculated between both count values for detection of the absolute position of the object 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in absolute position calculation means for detecting the position of an arm (for example, of an industrial L1 hot).

(Prior Art) Industrial robots have been used in various industries for the purpose of automating production lines and saving labor.

An industrial robot with a simple structure must be an articulated robot as shown in FIG. 5, for example. In the articulated industrial Kawaguchi bot shown in the figure,
Due to condition E, it is installed so that it can be rotated (swivel base 1)
An arm 2 is attached so as to be rotatable in the direction indicated by the arrow in the figure, and the swivel base 1 and arm 2 are generally driven by an electric or hydraulic motor.

The drive device for rotating the arm 20 described above is shown in FIG.

An arm 2 as an industrial robot component is rotatably attached to a support shaft 3 fixed to a rotating base 1 as an industrial robot component.

A large bevel gear 4 as a driven side m-wheel fixed to the support shaft 3 is meshed with a small bevel gear 7 as a drive side gear attached to a drive unit main body 6 having a motor 5 and a speed reducer. The unit 1~main body 6 is attached to the arm 2 by a bolt 8.

The motor 5 is equipped with a position detector 9 having a built-in encoder that detects the rotation angle of the rotation shaft as a coded signal.
is installed. Rough support shaft 3G is spur gear 1
1 is fixed, and a potentiometer 10 for detecting the rotation angle of the arm 2 is moved by this spur gear 11.

Therefore, when the motor 5 is driven, the small bevel gear 7 rotates and revolves around the large bevel tooth width 4, and the arm 2 rotates. A signal equal to the rotation angle of the arm 2 by 1.6 is inputted to the computer by the position detector 9 and the potentiometer 10. .

Next, a schematic configuration diagram of the absolute position calculation means of the arm 2 is shown in FIG. This absolute position calculating means operates in conjunction with the motor 5 connected to the motor drive circuit 26 and driving the arm 2 via the reducer 6, and the arm 2, and outputs a signal corresponding to its rotation angle. A potentiometer 10 that outputs an output to a CPU 23 built into a computer 22 via a Δ/D converter 15, an encoder 9 that detects the rotation angle in conjunction with the motor 5, and an encoder 9 that is connected to the CPU 23.
An origin pulse gate 16 that detects whether or not the origin pulse is accepted and the occurrence of the origin pulse, a pulse counter 17 that counts pulses for detecting the rotation angle of the encoder 9, and a potentiometer 10 when the origin pulse of the encoder 9 is generated. The voltage value and the ROM 24 in which the absolute position detection program of the arm 2 are stored are stored.

Here, the origin pulse is a pulse that the encoder 9 generates once per rotation, and the rotation angle detection pulse is a pulse that the encoder 9 generates once per unit rotation angle.

Next, the operation of the absolute position calculation means shown in FIG. 7 will be explained in detail based on the flowchart of the program stored in the ROM 24 of the computer 22 shown in FIG.

First, when the program starts, the CI) U 23 outputs the origin pulse interrupt enable signal to the origin pulse gate 16 via the signal line 19, and the origin pulse gate 16 receives the origin pulse generated by the encoder 9 from the signal line 13. (step 30).

Next, a signal instructing the rotational direction and rotational speed of the motor 5 is outputted from the CI-'U 23 to the motor drive circuit 26 via the signal line 27, and a voltage corresponding to the command is output from the Tanabata drive circuit 26 to the motor drive circuit 26. is applied to the motor 5 via line 28 (step 31).

Then, the motor 5 rotates 10 times in response to the command signal output in step 31, and the encoder 9 outputs the origin pulse (j, T
Signal line 13. origin pulse game
1 to 16 and to the CPU 23 via signal line 20.
C is determined (step 32).

If the encoder 9 does not generate the origin pulse signal, the process returns to step 30, and steps 30 to 31 are repeated until the encoder 9 generates the origin pulse signal. On the other hand, when the origin pulse is generated, the CPU 23 outputs a signal disabling the origin pulse interrupt to the origin pulse gate 16 via the signal line 19, and the origin pulse gate 16 is closed (
Step 33) At the same time, the signal line 2 is connected to the heptad drive circuit 26.
A stop command is issued via the motor 7, and the motor 5 is stopped (step 34).

Then, the voltage value of the potentiometer 10 corresponding to the position of the arm 2 when the motor 5 stops is determined by the signal line 12.
/D converter] 5, where the voltage value is converted into a digital value and input to the CPU 23 via the signal line 18 (step 35).

Based on the relative position data of the arm 2 input to the CPU 23 in this way, the basic output is obtained by inserting the voltage value of the potentiometer O when the origin pulse of the encoder 9 is generated, which is stored in advance in the ROM 24. The CPU 23 looks up the table and calculates the rotation angle θ of the arm 2 from the origin position (step 36).

As is clear from the above explanation, the absolute position θD of the arm 2 is determined by converting the voltage value of the potentiometer 10 at the time when the origin pulse is generated by the encoder 9 into a digital value by the Δ/D converter 15, and storing it in the ROM 24. The data closest to the digital value is selected from among the data in the basic output table, and the detection error of the potentiometer 10 is corrected for calculation.

(Problems to be Solved by the Invention) However, in such a conventional absolute position calculation means, since the absolute position of the arm 2 is detected by the potentiometer 10 and the Δ/D converter 15, the temperature of the potentiometer 10 is - The resistance value characteristics and the contact resistance values of the contacts will differ from the initial characteristics due to the influence of the atmosphere around the robot and aging, and the data obtained by the Δ/D converter 15 and the contact resistance values of the contacts will differ from the initial characteristics and are stored in the ROM 24. An error occurs between this and the data in the basic output table, making it difficult to accurately detect the absolute position of arm 2.

In addition, to increase the accuracy of absolute position detection, we need a high-precision potentiometer that is less affected by the surrounding atmosphere and aging.
Since a Δ/D converter corresponding to the accuracy of the potentiometer is required, the cost 1~ is high and A/D conversion takes time. (Roughly, the encoder 9 and potentiometer 10 are considered as one unit) 7-Driving u of arm 2
When replacing the potentiometer 10 or the reducer, etc., it is difficult to use a so-called Mogicor structure in which the potentiometer 10 is removably attached to the inside. The potentiometer 10. Since the encoder 9 and the like must be adjusted, there are problems in that it takes time for repairs.

The present invention has been made in view of these conventional problems.The present invention has been made in view of the problems of the conventional art. It is an object of the present invention to provide an absolute position calculation means that can detect the accurate absolute position of the arm by providing an encoder.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention includes a driving means for driving a driven body, and a device connected to the driving means to detect a relative rotation angle of the driven body. a pulse generator; an origin pulse encoder that outputs one pulse per revolution of the output shaft of a transmission connected to the pulse generator; a pulse count unit that measures the number of output pulses of the pulse generator; and the pulse generator. a first origin pulse detection means for detecting the origin pulse of the origin pulse encoder, a second origin pulse detection means for detecting the origin pulse of the origin pulse encoder, the pulse counting means, the first origin pulse detection means, and the second origin pulse The present invention is characterized by further comprising absolute position calculation means for calculating the absolute position of the driven body from the signal of the detection means.

(Operation) The operation of the present invention will be explained below based on FIG. 1. When the encoder, which is a pulse generator shown in the figure, generates a home pulse, a signal is sent from the first home pulse detection means to the absolute position calculation means, and the pulse counting means starts counting pulses for detecting the rotation angle of the encoder. be done.

Next, when the origin pulse encoder generates an origin pulse, a signal is sent from the second origin pulse detection means to the absolute position calculation means, and the counting of the rotation angle detection pulses of the encoder is completed.

In this way, the absolute position of the driven object is determined by calculating the count difference between the rotation angle detection pulses of the encoder when the encoder generates the origin pulse and when the origin pulse encoder generates the origin pulse. It is designed to be detected.

(Example) Embodiments of the present invention will be described based on the drawings.

FIG. 2 is a schematic diagram of the absolute position calculation means according to the present invention.

A reduction gear 6 is connected to the main shaft of the motor 5 driven by the motor drive circuit 26, and an arm 2 is connected to the reduction side shaft of the reduction gear 6.

Roughly speaking, an encoder 9 and a transmission 40 are connected to the main shaft of the motor 5, and an origin pulse encoder is connected to the output shaft of the transmission 40 for speed change.

The gear ratio of the transmission 40 is set close to 1 so that the origin pulse encoder 41 rotates at a slightly slower speed than the encoder 9.

The encoder 9 includes a first origin pulse gate 16 that manually inputs the origin pulse generated by the encoder 9, and a pulse counter 17 that counts the rotation angle and detection pulses generated by the encoder 9 on the signal lines 13 and 14. connected by. Further, a second origin pulse gate 43 that inputs the origin pulse generated by the origin pulse encoder 41 is connected to the origin pulse encoder 41 by a signal line 42 .

Said first origin pulse gate 16. The pulse counter 17 and the second origin pulse gate 43 are connected to a well-known C1) U23 in the computer 22 via respective signal lines.

Next, the operation of the absolute position calculating means shown in FIG. 2 will be explained in detail based on flowcharts 1 to 1 of the program written in the ROM 24 of the computer 22 shown in FIG.

When the program starts, signal line 1 is sent from the CPU 23.
9, a gate open signal is output to the first origin pulse gate 16, and the gate of the first origin pulse gate 16 is opened (step 50>).

Then, the signal line 2 is connected from the CPU 23 to the motor drive circuit 26.
A signal instructing the rotational direction and rotational speed of the motor 5 is outputted via the motor 7, and an output corresponding to the signal is given to the motor 5 from the motor drive circuit 26 via the power line 28 (
Step 51).

Next, the signal line 13 determines whether the encoder 9 has generated the origin pulse. This is determined by the CPU 23 via the first origin pulse gate 16 and the signal line 20, and if this determination is No, the motor 5 continues to rotate (step 52).

If the determination in step 52 is YES, the encoder 9 inputs the count value ■ of the rotation angle detection pulses inputted into the pulse counter 17 via the signal line 14 to the signal line 2.
Step 53), the gate open signal is sent from the CPU 23 to the signal line 19.
is output to the first origin pulse gate 16 through the gate, and the gate of the first origin pulse gate 16 is closed (step 54).
.

Next, a gate open signal is output from the CPU 23 to the second origin pulse gate 1-43 via the signal line 44, and the second origin pulse gate 43 is opened (step 55).

Then, in the same way as described in step 52, the signal line 42. A determination is made by the CPU 23 via the second w% point pulse gate 43 and the signal line 45, and if this determination is NO, the motor 5 continues to rotate at the same time (step 56).

If the determination in step 56 is YES, the CPU 23 reads the count value i of the rotation angle detection pulses that the encoder inputs to the pulse counter 17 via the signal line 14 via the signal line 21. In step 57), the gate open signal from the CPU 23 is temporarily stored.
It is output to the origin pulse gate 43 via the signal line 42,
The gate of the second origin pulse gate 43 is closed (step 58).

Then, the signal line 2 is connected from the CPU 23 to the motor drive circuit 26.
A stop signal is output via 7, and the motor 5 stops (
Step 59).

Next, the difference Δ between the pulse count value i of the encoder 9 temporarily stored in the CPU 23 in steps 53 and 57 and I
I=(i-I) is calculated, and the ROM24 is calculated from the pulse difference.
The absolute position of arm 2 is detected using the absolute position calculation formula stored in (step 60).

The principle of detecting the absolute position of arm 2 will be briefly explained with reference to FIG. This figure shows the encoder 9 and the origin pulse encoder 41 stacked together and viewed from above. In the figure, A indicates the holes provided on the outer circumference of the encoder 9 to generate rotation angle detection pulses, and B indicates the origin pulse generator. A hole C is a hole provided in the origin pulse encoder 41 for generating an origin pulse.

Encoder 9 and origin pulse encoder when arm 2 stops at an arbitrary position. Assume that the holes for generating both origin pulses of the sensor 41 are shifted by θ with respect to the measurement reference point as shown in the figure. 10. As mentioned above, the pulse count difference between the encoders 9 corresponding to one core at this angle θ is 8■. Next, assuming that the gear ratio of the transmission 40 is N (N is extremely close to 1), which phase is the origin pulse generation hole B of the encoder 9 and the origin pulse generation hole C of the origin pulse encoder 41? Each rotation of the encoder 9 results in a shift of 1-N rotations.

Therefore, if the number of rotation angle/degree detection pulses generated by the encoder 9 every rotation is P, the phase shift θ mentioned above is:
When converted to the rotation speed of the encoder 9, it becomes ΔI/P rotation. On the contrary, in order for the above-mentioned phase shift to become a ΔI/P rotation, the encoder 9 must be rotated by ΔI/((1-N)·P) from the starting point of the arm 2. However, this formula is always a decimal number, so if we round up the decimal point and make the number of rotations of the encoder 9 an integer, the integrated value of the rotation angle detection pulses generated by the encoder 9 from the starting point of the arm 2 is: It is expressed as ΔI/((1-N>・p)+0.5]・P.

Also, the initial phase difference between the holes B and C for generating pulses at both origin points at the starting origin at the time of assembling the arm 2 is determined by the encoder 9.
It is assumed that the number of pulses for detecting the rotation angle is ΔP,
If the theoretical starting origin of arm 2 at that time is different from the actual starting origin by ΔQ in terms of the number of pulses, the general formula for expressing the absolute position O of arm 2 in terms of the number of pulses is:
θ=INT[(Δ■-to 8P/((1N)・t')+0
．． 5] ・P+ΔQ [pulse].

e: Absolute position of arm 2 [pulses,] △■: Pulse count difference corresponding to both encoders phase difference angle θ [pulses] △P: Pulse count difference when assembled [pulses] N Gear ratio P of two encoders : Number of pulses generated for rotation angle detection per encoder rotation [pulses] △Q: Mechanical deviation of the arm origin [pulses] In this way, the absolute position O of arm 2 can be expressed by the number of pulses, so this By checking the number of pulses into angles using a combination coater, it is possible to detect the co-movement angle from the origin position of the )7-me 2, that is, the absolute position.

In order to improve the detection accuracy of the absolute position of the arm 2, it is necessary to bring the speed ratio N as close to 1 as possible.

For example, when the reduction ratio of the reducer 6 is 1/100 and the operating range of the arm 2 is 1 rotation, the speed ratio of the speed change Ia 40 is
It is sufficient to make it as close to 1 as possible within the range of adding ii1 to the condition of 100/101 <N < 1. However, since the gear ratio is close to 1, encoder 9. The transmission 40 and the origin pulse encoder 41 are connected to minimize mechanical play.

(Effects of the Invention) As explained above, the present invention includes a driving means for driving a driven body, a pulse generator connected to the driving means to detect a relative rotation angle of the driven body, and a pulse generator for driving a driven body. The transmission is connected to an origin pulse encoder that outputs one pulse per rotation of the output shaft, a pulse counting means that measures the number of output pulses of the pulse generator, and a pulse generator that detects the origin pulse of the pulse generator. a first origin pulse detection means for detecting the origin pulse of the origin pulse encoder, a second origin pulse detection means for detecting the origin pulse of the origin pulse encoder, and a means for detecting the origin pulse.

By providing the absolute position calculation means for calculating the absolute position of the driven body from the signals of the first origin pulse detection means and the second origin pulse detection means, it is possible to detect the absolute position of the arm without using a potentiometer. It is no longer necessary to use a Δ/D converter, and the absolute position of the arm can now be detected reliably and precisely. Furthermore, in the past, the accuracy of detecting the absolute position of the arm depended on the accuracy of the potentiometer, which placed restrictions on where the robot could be used. However, these restrictions have been significantly eased, and position detection has been made on the arm side. This provides an excellent effect in that a drive unit that integrates an arm, a speed reducer, and a motor can be easily modularized for performance without installing a device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an absolute position calculation means according to the present invention;
FIG. 2 is a schematic diagram of the absolute position calculation means according to the present invention, and FIG.
Figure 4 is an explanatory diagram of the absolute position detection principle according to the present invention, Figure 4 is a flowchart 1 of the computer program in the absolute position detection 'AM according to the present invention, Figure 5 is an explanatory diagram of the conventional robot, and Figure 5 is an explanatory diagram of the conventional robot. Figure 6 (is an explanatory diagram of the drive device in Figure 5, Figure 7
The figure is a diagram of a conventional absolute position calculating means, and FIG. 8 is a flowchart of a computer program in the conventional absolute position calculating means. 1... Swivel base, 2... Arm, 3... Support shaft, 4... Large bevel gear, 5... Motor,
6... Drive unit lζ main body, 7... Small bevel gear,
8...Bolt. 9... Position detector, 10... Potentiometer, 1
1... Spur gear, A... Hole for rotation angle detection, B... Hole for origin pulse generation, C... Hole for origin pulse generation, D... Measurement reference point. Patent applicant Nissan Motor Co., Ltd. Figure 2 Figure 8

Claims (1)

[Claims] A drive means for driving a driven body, a pulse generator connected to the drive means to detect the relative rotation angle of the driven body, and a pulse generator connected to the pulse generator for one rotation of the output shaft of the transmission. an origin pulse encoder that outputs pulses, a pulse counting means that measures the number of output pulses of the pulse generator, a first origin pulse detection means that detects the origin pulse of the pulse generator, and an origin pulse of the origin pulse encoder. and absolute position calculation means for calculating the absolute position of the driven body from the signals of the pulse counting means, the first origin pulse detection means, and the second origin pulse detection means. An absolute position detection device characterized by: