JPH04123205A - Initial position detector for target to be controlled - Google Patents

Abstract

PURPOSE:To reduce origin restoring operation by counting up the rotational frequency of a rotary encoder by a counter and allowing the coordinate of a controlled target to coincide with control coordinates. CONSTITUTION:A rotary encoder body 5 is an increment type rotary encoder and outputs A and B phase outputs respectively having a 90 deg. phase difference and a C phase output having the prescribed number of pulses, e.g. eight pulses. After turning on a power supply, a motor 3 is rotated, a C phase pulse from the encoder 5 is detected, the position of an arm 1 to be the controlled target is recognized by the count value of the counter 6 and the physical coordinates of the arm 1 are allowed to coincide with the control coordinates. Since one or more C phase pulses are outputted in one revolution of the encoder 4, the origin restoring operation can be executed within one revolution of the motor 3. Thus, the origin restoring operation can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is used in robots, machine tools, etc. that control a controlled object using an electric motor, and detects the initial position of the controlled object when the power is turned on. The present invention relates to an initial position detection device.

In conventional technical industrial robots, machine tools, etc., it is necessary to match the control coordinates in the control device with the coordinates of the actual object to be controlled, such as a robot, before performing positioning control after power is turned on. For this reason, the control target itself is moved to the origin position and the necessary control is performed after these coordinates are matched. That is, the return to the origin is performed by moving an arm in an articulated robot or the like, or an XY table or the like in a machine tool to the origin position using an electric motor.

FIG. 6 is a mechanical diagram of an arm for one axis of a conventional horizontal articulated robot. In this figure, the controlled object is the arm 31. The arm 31 is driven by an electric motor 33 via a reduction gear 32, and its position is controlled.

34 is a rotary encoder.

Now, when the power is turned on, the arm 31 is assumed to be at the position A in FIG. 7, for example. After the power is turned on, the arm 3 moves in the direction of the position B, and stops moving after being detected by the origin sensor 35. The control device matches the control coordinates with the physical coordinates of the arm 31 by recognizing that point as the origin of the arm 31.

Problems to be Solved by the Invention However, when performing a return to the origin with such a configuration, since the origin sensor 35 is fixed at one point, it is necessary to move the object to be controlled to the origin position. This method not only requires moving the object to be controlled, but also requires a long time.

Therefore, as shown in Japanese Unexamined Patent Publication No. 1-31209, there is a method of connecting an absolute encoder and an incremental encoder and detecting the arm position by the combination, and a method of detecting the arm position using a multi-rotation type absolute encoder. Methods for detecting position are known. However, the former requires the use of two types of encoders, and also requires a large capacity memory to refer to the data table, resulting in a complicated configuration. The latter method also has the disadvantage that it is difficult to improve resolution because it uses an absolute encoder.

An object of the present invention is to use a single incremental encoder with a relatively simple configuration to detect the position of a controlled object after the power is turned on as it moves within one rotation of the motor, thereby reducing the need for return-to-origin operations.

Means for Solving the Problems In order to achieve the above object, the initial position detection device of the present invention comprises a rotary encoder connected to an electric motor and generating a predetermined number of pulses per rotation, and a C phase (Z) of the rotary encoder. (phase) A means for determining the order of pulses, a counter that changes according to the rotation angle of the encoder, a power supply that backs up the count value of the counter, and control based on the count value of the counter and the pulse order of the rotary encoder. This initial position detecting means includes means for determining the position of an object, and reduces the amount of movement of the controlled object in an origin return operation.

According to the present invention having the above configuration, the C-phase pulse from the encoder is detected by rotating the motor after power is turned on, and the position of the object to be controlled is recognized and controlled based on the count value of the counter obtained at that time. The coordinates are made to match the physical coordinates. C phase pulse is encoder 1
Since there is one or more during rotation, the return-to-origin operation can be completed within one rotation of the motor.

EXAMPLE A first example of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the basic configuration of one arm of a horizontally articulated robot robot. In this figure, electric motor 111 (
The motor) 3 is connected to the object to be controlled, in this case the arm 1, via the reducer 2.

An incremental rotary encoder 4 with a built-in counter is connected to the rotating shaft of the motor 3. This encoder 4
consists of a rotary encoder main body (RE) 5 and a counter 6 as shown in the figure. The rotary encoder main body 5 is an incremental type rotary encoder, and outputs A-phase and B-phase outputs having an electrical phase difference of 900 degrees, and a C-phase output of a predetermined number of pulses per rotation, for example, 8 pulses. The counter 6 is a counter that counts the amount of rotation of the motor 3, and its value increases or decreases depending on the rotation of the motor 3. For example, if the encoder rotates 900 degrees clockwise, the count increases by 1, and if it rotates 90 degrees in the opposite direction, the count increases by 1.
Count down. Further, a backup power source 7 is connected to the counter 6, so that counting can be performed even when the main power source of the control device is off. The counted value is given to the position detecting means 8. The position detecting means 8 detects the position of the robot arm based on this count value.

FIG. 2 is a diagram showing the relationship between the mechanical origin, the C phase, and the amount of rotation of the motor. A, B from mechanical origin to encoder origin
Let the number of phase encoder output pulses be the origin correction value ΔZ. The encoder origin here is the position of any C-phase pulse,
The order of the C-phase pulse is set to 0.

The amount of rotation representing how many times the motor 3 has rotated from the encoder origin is represented by m, and is determined from the count value (represented by n) output from the counter 6 to the position detection means 8. If the increment of the count value per rotation of the motor 3 is Δn, then the motor 3
The amount of rotation m is given by the following equation 0.

m=INT(n/Δn) --■INT is 0
This is an operation that extracts the integer value of the value within.

When the encoder has (i+1) C phases per rotation, each C phase is expressed as c* using a subscript from 0 to i.
It is expressed as (k: k=o~1). The position of C1 pulse is C
If it is within one rotation with o as the reference, it is expressed by the following equation (2) using k.

IN/ (i+1)] xk ・・・・・・■
N is the number of output pulses per rotation of the motor 3. However, it does not have to be the direct output of the encoder, and may be the number of processed pulses taken into the position detection means 8.

Using these, the C phase pulse detected from the mechanical origin for the first time after turning on the power is C.

If it is a pulse, the amount of movement from the mechanical origin to that point is determined by the following equation.

[Amount of movement from the mechanical origin] - [Amount of movement within one rotation of the motor] + [(Amount of motor rotation)
...■ Figure 3 shows a flowchart from power-on to current position detection. In this figure, first, after turning on the power, step 16.
At step 17, the arm at an arbitrary position is rotated until the C-phase output of the rotary encoder is obtained. C
If the phase output is obtained, the process proceeds to step 18, where the count value n of the counter 6 at that time is read, and the rank k of the C phase obtained earlier is known at step 19, and then, at step 20, using the 0 formula, Calculate the amount of rotation of the motor 3. Then proceed to step 24.22 and move from type 0 to arm 3.
Find the amount of movement from the mechanical origin. Here 20.21.
22 may be one step, or step 18
and 19 and the order of steps 20 and 21 may be reversed. This allows the position of the arm 1, which is the object to be controlled, to be detected. Even when the main power is turned off, the counter is maintained by the backup power supply 7, so by matching the physical coordinates of the arm thus obtained with the control coordinates, the same purpose as the conventional return-to-origin operation can be achieved. I can do it. Note that the value of k may be determined using either hardware or software.

Next, a second embodiment of the present invention will be described.

In the first embodiment, the C phases during one rotation were distinguished from O to i, but the count value of the counter when a certain C phase is detected is the same as the count value of the counter when the next C phase is detected. The case where they are different, that is, the case where the number of C phases per revolution is less than or equal to the counter increment per revolution will be explained using FIG. As in FIG. 2, the difference between the mechanical origin and the encoder origin is defined as the origin correction value ΔZ. Let the encoder output pulse per revolution be N,
Let the number of C phases be (j+l). Let the counter increment per revolution be Δn. Letting n be the count value when the C phase is detected for the first time after power is turned on, its position is expressed by the following equation 0.

[Movement amount from mechanical origin] = [Movement amount per count value 1 x count value] 10 [Origin correction value] = (N/Δn) This can be realized by omitting steps 19 and 20 of .

Next, a third embodiment of the present invention will be described.

In the second embodiment, the counter value when a certain C phase is detected is different from the counter value when the adjacent C phase is detected, but when they become the same, that is, 1 A case will be described in which the number of C phases per rotation is greater than the counter increment per rotation. In this case, when the C phase is detected, the counter value is the same as that of the adjacent C phase, so a means for distinguishing this C phase is required. A specific example will be explained using FIG. 5. Similarly to FIG. 2, the difference from the mechanical origin to the encoder origin is defined as the origin correction value ΔZ.

Let N be the output pulse of the encoder per revolution, and let the number of C phases be (i+1). Let the increment of the counter for one revolution be Δn. Here, as an example, 1=7 and Δn=2. 4 per counter count (hereinafter referred to as count value)
Since there are four C phases, the four C phases are processed using 2-bit data. If the value of the 2-bit data is k, then the position of the C phase obtained for the first time after the power is turned on is the next 0.
Expressed by the formula.

[Movement amount from mechanical origin = [Movement amount within count value] + [Movement amount per count xy1] + [Origin correction value] = IN/ (j+1)] xk + (N/Δn)Xn+ΔZ ・. . . ■ The flowchart in this case omits step 20 in FIG. 3 so that the song can be actually sung.

In addition, whether 2-bit data was used to calculate k or C
As long as the phases can be distinguished, the purpose can be achieved, so the value does not matter. In this case, the determination may be made by hardware or by software, and the method is not critical. In these embodiments, a horizontal multi-joint arm has been described, but the control object may be an orthogonal type control object or another rotation type control object. Also, the type of motor does not matter. Of course, a combination of these embodiments is also possible. The point is that the position of the object to be controlled, such as an arm, can be detected from the count value of the counter when the C phase is detected and the order of the C phase after the power is turned on.

Effects of the Invention As described above, according to the present invention, the amount of rotation of the motor is counted by a counter using a rotary encoder, and by holding the counted value, the control coordinates and the coordinates of a controlled object such as a robot arm can be determined. I'm trying to match. Therefore, the same purpose as returning to the origin can be achieved by only slightly rotating the motor after the power is turned on, and the control coordinates and arm coordinates can be made to match without moving the arm to the origin position such as Rohonoto.

Furthermore, it can be realized by relatively simple arithmetic processing, and the position of the controlled object can be recognized without using a complicated table. Furthermore, there is an advantage that it is not necessary to use an origin sensor and its adjustment is also unnecessary. Furthermore, the position can be detected in the time it takes for the motor to rotate one revolution or less.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of one arm of a horizontal articulated robot according to the first embodiment of the present invention, and Fig. 2 shows the position of the robot arm, the count value of the counter, the amount of rotation of the motor, and the C phase. FIG. 3 is a flowchart showing the procedure for arm position detection, FIG. 4 is a diagram showing the relationship between the C phase and the count value of the counter in the second embodiment of the present invention, and FIG. A diagram showing the relationship between the C phase and the count value of the counter in the third embodiment of the present invention, FIG. 6 is a diagram showing the configuration of one arm of a conventional horizontal articulated robot, and FIG. 7 explains return to origin. This is a diagram. 1...Arm (object to be controlled), 2...
Reducer, 3...Electric motor, 4...Rotary encoder, 5...Encoder body, 6...
... Counter, 7 ... Backup power supply, 8 ... Position detection means. Name of agent: Patent attorney Haruaki Ogata and two others

Claims (1)

[Claims] An electric motor that drives the controlled object, A-phase and B-phase signals with a 90 degree phase difference that are connected to the electric motor, and one or more C-phase (Z-phase) signals during one rotation of the encoder.
A rotary encoder that outputs a signal, a means for determining the order of the plurality of C-phase signals, a counter that counts the amount of rotation of the encoder, a backup power source for the counter, a count value of the counter, and a means for determining the order of the C-phase signals. An initial position detecting device for a controlled object, comprising: position detecting means for determining the position of the controlled object based on the order of signals.