JPS61294510A - Absolute position detector - Google Patents

Abstract

PURPOSE:To detect an accurate absolute position by using a potentiovoltage storing buffer which stores the voltage level of a potentiometer obtained when an original point pulse is produced after replacing it into the latest data while a robot is working. CONSTITUTION:An absolute position detector is provided a drive means 80 for an object 2 to be driven, a pulse generator 9 for detection of absolute revolving angle connected to the means 80, a potentiometer 10 for detection of revolving angle, an original point pulse detection means 81, an A/D converter 15, a position storage means 82 and a data rewriting means 83. When the generator 9 produces an original point pulse, the voltage level of a potentiometer interlocking the object 2 is stored in the means 82 after A/D conversion. Thus the data train stored in a ROM is replaced with the data train of the means 82 by a rewriting means 82 when a rewriting indication is given to the data train of the ROM from a terminal equipment which gives an instruction to a robot controller.

Description

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

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

Among these industrial robots, there is an articulated robot as shown in FIG. 4, for example, which has a simple structure.

In the articulated industrial robot shown in the figure, an arm 2 is attached to a swivel base 1 which is rotatably attached to a base B so as to be rotatable in the direction indicated by the arrow in the figure. The swivel table 1 and arm 2 are generally driven by an electric or hydraulic motor.

A drive device for rotating the arm 2 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 gear fixed to the support shaft 3 meshes with a small bevel gear 7 as a driving gear attached to a drive unit main body 6 having a motor 5 and a speed reducer. 6 is attached to the arm 2 with a bolt 8.

The motor 5 has a position detector 9 with a built-in encoder that detects the rotation angle of the rotation axis as a coded signal.
is installed. Furthermore, the spur gear 11 is attached to the support shaft 3.
A potentiometer 10 for detecting the rotation angle of the arm 2 is moved by the spur gear 11.

Therefore, when the motor 5 is driven, the small bevel gear 7 rotates and revolves around the large bevel gear 4, causing the arm 2 to rotate. A signal corresponding to the rotation angle of the arm 2 is input to the computer by a position detector 9 and a potentiometer 10.

Next, a schematic configuration diagram of the absolute position detection device for arm 2 is shown in FIG. This absolute position detection device includes a motor 5 that is connected to a motor drive circuit 26 and drives the arm 2 via a reducer 6, and an A/D converter that operates in conjunction with the arm 2 and transmits a signal according to its rotation angle. 15 to the computer 22
Potentiometer 1 outputs to CPU 23 built in
0, an encoder 9 that is linked to the motor 5 and detects its rotation angle, and an origin pulse gate 16 and encoder 9 that are connected to the CPU 23 and that control whether or not the encoder 9 accepts the origin pulse and detect the generation of the origin pulse. A pulse counter 17 that counts pulses for detecting the rotation angle of
, a potentiometer voltage storage memory 24 that stores the A/D converted voltage value of the potentiometer 10, and an arm angle storage memory 29 that stores the rotation angle of the arm 2 converted into the number of pulses generated by the encoder 9. It is configured.

Next, a data storage program for the absolute position detecting device shown in FIG. 6 will be explained based on FIG. 7.

First, from the terminal that gives commands to the robot control device,
The number of the axis, which is a component of the robot, on which data is to be stored is designated (step 30).

Next, a signal instructing the rotational direction and rotational speed of the motor 5 is outputted from the CPLJ 23 to the motor drive circuit 26 via the signal line 27, and a voltage corresponding to the instruction is transmitted from the motor drive circuit 26 to the motor via the power line 28. 5 (step 31).

The motor 5 rotates in accordance with the command signal output in step 31, and the signal line 13 detects whether or not the origin pulse signal is generated by the encoder 9. This is determined by the CPU 23 via the origin pulse gate 16 and the signal line 20 (step 32).

If the origin pulse signal is not generated, return to step 31;
Step 31 continues to be executed until the encoder 9 generates the origin pulse signal. On the other hand, when the origin pulse is generated, the pulse count value In of the encoder 9 from the pulse counter 17 is stored in the arm angle storage memory 29 via the signal line 21° CPU 23 and the signal line 25 (step 33).
, the voltage value vntfi of the potentiometer 10 is converted into a digital signal by the A/D converter 15 and sent to the signal line 18 . CPtJ23
and a potentiometer voltage storage memory 24 via a signal line 25.
(step 34).

Then, it is determined whether an instruction to end the data collection has been issued from the terminal (step 35), and if there is no instruction to end, the process returns to step 31 and steps 31 to 35 are repeatedly executed. On the other hand, if there is a termination instruction, the pulse count value In and the potentiometer voltage value Vn, which were temporarily stored in steps 33 and 34, are stored in the rewritable ROM (step 36).

As shown in FIG. 8, the data collected in step 33 is the pulse count value In at the time when each origin pulse of the encoder 9 is generated, and the data collected in step 34 is the pulse count value In at each origin pulse of the encoder 9. This is the potentiometer voltage value Vn at the time of occurrence.

Then, in step 36, a data string as shown in FIG. 9 is stored in the rewritable ROM.

Next, the operation of the absolute position detection device shown in FIG.
The explanation will be based on the flowchart of the program of the computer 22 shown in the figure.

First, when the program starts, the origin pulse interrupt enable signal is output from the CPU 23 to the origin pulse gate 16 via the signal line 19, and the origin pulse gate 16 waits for the origin pulse generated by the encoder 9 to be input from the signal line 13. . (Step 40).

Next, when an instruction for origin processing is issued from the operation panel (step 41>), a signal instructing the rotation direction and rotation speed of the motor 5 is output from the CPU 23 via the signal line 27 to the motor drive circuit 26, and the command A voltage corresponding to the voltage is applied from the motor drive circuit 26 to the motor 5 via the power line 28 (step 42).

The motor 5 then rotates in accordance with the command signal output in step 42, and the signal line 13 detects whether or not the origin pulse signal is generated by the encoder 9. This is determined by the CPU 23 via the origin pulse gate 16 and the signal line 20 (step 43).

If the origin pulse is not generated, the process returns to step 42, and step 42 is continued until the encoder 9 generates the origin pulse signal.
When the origin pulse signal is generated, the CPU 23 outputs the origin pulse interrupt disable signal to the origin pulse gate 16 via the signal line 19, and the origin pulse gate 16 is closed (step 44). A stop command is issued via the signal line 27, and the motor 5 is stopped (step 45).

Then, the voltage value of the potentiometer 10 corresponding to the position of the arm 2 when the motor 5 stops is set to A by the signal line 12.
The voltage value is input to the /D converter 15, where the voltage value is converted into a digital value and input to the CPU 23 via the signal line 18 (step 46).

Based on the relative position data of the arm 2 input to the CPU 23 in this way, the data storage program explained in FIG. 7 looks up the data string stored in the ROM, and The rotation angle on is calculated by the CPU 23 (step 47).

Next, the servo control speed of the robot is returned to normal speed (step 48).

As is clear from the above explanation, the absolute position e 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 A/D converter 15, and storing it in the ROM. The data closest to the digital value is selected from among the data in the data string, 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 detection device, the temperature-resistance value characteristics of the potentiometer 10, the contact resistance value of the contacts, and the play of the drive mechanism of the potentiometer 10 are The characteristics of the arm 2 will differ from the initial ones due to the influence of the atmosphere and aging, and an error will occur between the data obtained by the A/D converter 15 and the data in the data string stored in the ROM. Accurate absolute position detection becomes difficult. The data string stored in the ROM is transferred to the ROM by another program as described above.
Since the data is stored in the memory, the robot must be temporarily stopped to collect this data, and it takes time to collect the data.

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 an A/D converter corresponding to the accuracy of the potentiometer is required, there are problems such as high cost and time required for A/D conversion.

The present invention has been made in view of these conventional problems, and it is an object of the present invention to perform A/D conversion of the voltage value of the potentiometer that occurs when the origin pulse of the encoder is generated during the operation of the robot, that is, during the execution of a so-called normal servo control program. An object of the present invention is to provide an absolute position detecting device that can always detect the accurate absolute position of the arm by providing a potentiometer voltage storage memory buffer that constantly updates and stores the measured value to the latest data. shall be.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention includes a driving means for driving a driven body, and a system connected to the driving means to detect the relative rotation angle of the driven body. a pulse generator to
A potentiometer connected to the driven body to detect the rotation angle of the driven body; origin pulse detection means for detecting the origin pulse of the pulse generator; and A that converts the detected voltage of the potentiometer into a digital value. /
D conversion means; position storage means for storing data from the A/D conversion means when a signal is output from the origin pulse detection means; and position storage means for storing the data from the position storage means when rewriting of the data is instructed. The present invention is characterized in that it further includes a data rewriting means for reading the data and rewriting the data.

(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 an origin pulse, the A/D conversion value of the potentiometer voltage value that detects the relative position of the driven object in conjunction with the driven object is stored in the position storage means. When a terminal that gives a command to the control device instructs the data string stored in the ROM to be rewritten, the data replacement means updates the data string to the data string stored in the position storage means.

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

FIG. 2 is a schematic configuration diagram of an absolute position detection device according to the present invention.

A reducer 6 and an encoder 9 are connected to the main shaft of the motor 5 driven by the motor drive circuit 26.
An arm 2 and a potentiometer 10 interlocked with the arm 2 are connected to the shaft on the deceleration side.

An origin pulse gate 16 that inputs the origin pulse generated by the encoder 9 and a pulse counter 17 that counts the rotation angle detection pulse generated by the encoder 9 are connected to the encoder 9 by signal lines 13 and 14.

Further, an A/D converter 15 is connected to the potentiometer 10 via a signal line 12.

Said A/D converter 15. The origin pulse gate 16 and the pulse counter 17 are connected to a CPU 23 provided in a computer 22 by signal lines 18, 19, 20, and 21. Furthermore, the CPU 23 includes a potentiometer voltage storage memory 24 that stores the potentiometer voltage at the time when the origin pulse of the encoder 9 is generated, an arm angle storage memory 29 that stores the angle of the arm 2 as the number of pulses of the encoder 9, and an origin point of the encoder 9. A potentiometer voltage storage memory buffer 50 that stores an A/D converted value of a potentiometer voltage every time a pulse is generated is connected via a signal line 25.

Next, the operation of the absolute position detection device shown in FIG. 2 will be explained in detail based on the flowchart of the program written in the computer 22 shown in FIG.

First, when the program starts, the origin pulse interrupt enable signal is output from the CPU 23 to the origin pulse gate 16 via the signal line 19, and the origin pulse gate 16 waits for the origin pulse generated by the encoder 9 to be input from the signal line 13. . (Step 60).

Next, when an instruction for origin processing is issued from the operation panel (step 61), a signal instructing the rotation direction and rotation speed of the motor 5 is output from the CPU 23 to the motor drive circuit 26 via the signal line 27, and the command A voltage corresponding to the voltage is applied from the motor drive circuit 26 to the motor 5 via the power line 28 (step 62).

The motor 5 then rotates in accordance with the command signal output in step 42, and the signal line 13 detects whether or not the origin pulse signal is generated by the encoder 9. This is determined by the CPU 23 via the origin pulse gate 16 and the signal line 20 (step 63).

If the origin pulse is not generated, the process returns to step 62, and step 62 continues until the encoder 9 generates the origin pulse signal.
When the origin pulse signal is generated, a stop command is issued from the CPU 23 to the motor drive circuit 26 via the signal line 27, and the motor 5 is stopped (step 64).

Then, the voltage value of the potentiometer 10 corresponding to the position of the arm 2 when the motor 5 stops is input to the A/D converter 15 via the signal line 12, where the voltage value is converted into a digital value and a signal is generated. It is input to the CPU 23 via line 18 (step 65). .

Based on the relative position data of the arm 2 input to the CPtJ23 in this way, the data string stored in the ROM is looked up by the data storage program explained in FIG. The rotation angle θn is calculated by the CPU 23 (step 66).

Next, step 67) returns the servo control speed of the robot to the normal speed, and step 67 is executed until the origin pulse is generated from the encoder 9 again (step 68).

Then, when the origin pulse is generated, the voltage value of the potentiometer 10 at the time when the origin pulse is generated is A/D converted, and the value is temporarily stored as POTGEN in the CPU 23 via the signal line 18 (step 69).

Next, step 69 uses the voltage value yn of the potentiometer 10 at the time of generation of the origin pulse stored in the ROM.
It is determined whether the absolute value of the difference between the POTGEN values read in, that is, the relative error, is smaller than ((Vn - Vn-1>/2)/3) (step 70).

The POT fulfillment that can be written on the drawing here is (Vn -Vn-
1> is the average of (Vn - Vn-1) /2
means.

If the relative error is POTE)EL/3 or more, that is, outside the allowable range, the data read in step 69 is unreliable, and a position sensor error is displayed (step 74), indicating that the relative error is within the allowable range. If within the range, the data read in step 69 (POTGEN)
is updated and stored in the potentiometer voltage storage memory buffer 50 from the CPU 23 via the signal line 25 (step 71).
.

Then, it is determined whether an instruction to refresh the origin pulse data has been issued from the operation panel (step 72), and if there is no instruction, the process returns to step 67 and steps 67 to 72 are executed. If there is a refresh instruction, the latest data updated in step 71 is stored from the potentiometer voltage storage memory buffer 50 to the potentiometer voltage storage memory 24 via the signal line 25 by the CPtJ 23 (step 73). The absolute position of arm 2 is detected based on .

(Effects of the Invention) As explained above, the present invention includes a drive means for driving a driven body, a pulse generator connected to the drive means to detect a relative rotation angle of the driven body, and a pulse generator for detecting a relative rotation angle of the driven body. a potentiometer connected to the body to detect the rotation angle of the driven body, an origin pulse detection means to detect the origin pulse of the pulse generator, and an A/D conversion to convert the detected voltage of the potentiometer into a digital value. means, position storage means for storing data from the A/D conversion means when a signal is output from the origin pulse detection means, and reading the data from the position storage means when rewriting of the data is instructed. By providing a data rewriting means for rewriting the data, the A/D conversion value of the potentiometer voltage at the time when the origin pulse of the encoder is generated is automatically updated to the latest value during the execution of a normal servo control program. Since it can be updated and stored as data, this data can be freely rewritten at any time by the operator's data refresh instruction, and the absolute position of the arm can now be detected reliably and precisely. Generally speaking, in the past, the accuracy of detecting the absolute position of the arm depended on the accuracy of the potentiometer, which resulted in restrictions on where the robot could be used, but this has the excellent effect of significantly easing those restrictions. play.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an absolute position detection device according to the present invention,
FIG. 2 is a configuration diagram of the absolute position detection device according to the present invention, and FIG.
The figure is a flowchart of a computer program in the absolute position detecting device according to the present invention, FIG. 4 is an explanatory diagram of a conventional robot, FIG. 5 is an explanatory diagram of the drive device of FIG. 4, and FIG. 6 is a conventional robot. 7 to 9 are flowcharts of a general origin data collection program and their explanatory diagrams. FIG. 10 is a flowchart of a computer program in a conventional absolute position detection device. be. 1... Swivel base, 2... Arm °, 3... Support shaft, 4... Large bevel gear, 5... Motor,
6... Drive unit main body, 7... Small bevel gear,
8... Bolt, 9... Position detector, 10... Potentiometer, 11... Spur gear, Patent applicant Nissan Motor Co., Ltd. Figure 2 Figure 3 fM 6 Figure

Claims (1)

[Claims] 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 connected to the driven body to detect a rotation angle of the driven body. a potentiometer that detects the origin pulse of the pulse generator, an origin pulse detection means that detects the origin pulse of the pulse generator, an A/D conversion means that converts the detected voltage of the potentiometer into a digital value, and a A position storage means for storing data from the A/D conversion means, and a data rewriting means for reading the data from the position storage means and rewriting the data when the rewriting of the data is instructed. An absolute position detection device characterized by: