JPH01276009A - Position detecting method for movable mechanism - Google Patents

Abstract

PURPOSE:To easily execute an origin adjustment by correcting a count value, based on an origin correction value being a difference between a count value of a counter in an origin target position of an encoder and a counter value of a counter in a mechanical origin position of a movable mechanism. CONSTITUTION:An encoder 5 rotates through a transfer mechanism by following up a motor (not shown in the figure). The encoder 5 outputs an A phase signal (a) and a B phase signal (b) which have been shifted by 90 deg. from each other by one piece each, respectively, whenever it rotates by a prescribed angle being smaller enough than one rotation, and outputs one Z phase signal (z), whenever it makes one rotation, and connected to a position counter 11 of the next stage. The counter 11 inputs the A and the B phase signals (a), (b) from the encoder 5 and detects the rotation direction and the rotation quantity from its phase relation, and obtains a count value N by counting its pulse. This value N is given to an adder 14, becomes a correction count Nc by adding an origin correction value DELTAN which has been stored in an origin correction value memory 15, and this value is given to a position data converter 12, converted to an absolute position theta of a movable mechanism and given to a controller 13.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a position detection device for a movable mechanism such as a robot arm, which detects the absolute position of a movable mechanism.

(Prior Art) In a movable mechanism such as a robot arm, various commands are given to the movable mechanism according to a position based on a preset mechanical origin, that is, an absolute position. As methods for determining the above-mentioned absolute position, there are a method using an absolute encoder and a method using an incremental encoder. In a method using an absolute encoder, a signal corresponding to the absolute position of each movable mechanism is directly output from the encoder, whereas in a method using an incremental encoder, the signal is output directly according to the displacement of the movable mechanism. - The signal output from the -da is counted by a counter, and the absolute position is determined from the count value. Therefore, in the case of a method using an incremental encoder, the count value of the counter becomes unstable when the power is turned off to -U, so when the power is turned to A again, the movable mechanism is returned to the mechanical origin and this An origin adjustment operation is required, such as setting the count value of a counter at a time to a predetermined origin value such as zero.

In addition, especially when assembling and adjusting a robot, it is necessary to adjust the origin to match the mechanical origin position of the movable mechanism and the origin signal generation position of the encoder.

FIG. 3 is a schematic configuration diagram showing a conventional example of a device for detecting the absolute position of a movable mechanism using an incremental encoder. In the figure, the rotation of a motor 1, which is a drive source, is transmitted to a movable machine such as a robot arm via a transmission mechanism 2.
43. The rotation of the motor 1 is also transmitted to an incremental rotary encoder 5 via another transmission mechanism 4, and the rotary encoder 5 changes the mutual phase by 90 degrees every time the rotary encoder 5 rotates by a certain angle that is sufficiently smaller than one revolution. Two reference signals a and b (hereinafter referred to as Δ phase signal and B phase signal) which are shifted by a degree are output, and
One reference signal Z (hereinafter referred to as a 7-phase signal) is output every time the rotary encoder 5 rotates once. Furthermore, the rotation of the motor 1 is transmitted to the origin target position detector 7 via another transmission mechanism 6. This origin target position detector 7 is for detecting that the movable mechanism 3 has reached a predetermined origin target position that is close to the preset mechanical origin of the movable mechanism 3, It is composed of a disk 8 with a light shielding plate 8a that rotates following the motor 1, and a sensor 9 consisting of a photosensor or the like arranged so as to straddle the front and back sides of this light shielding plate 8a.
-(P is output.

FIG. 4 shows the electrical configuration of the position detection device of the movable mechanism shown in FIG. 3. FIG. 1 is a schematic block diagram. In the figure,
The encoder 5 supplies the A-phase signal a and the B-phase signal S to the counter 11, and the counter 11 adjusts the force C count value N based on these signals. Further, the count value N of the counter 11 is given to a position f-ta converter 12, and is converted into a coordinate position θ of the Kasenkai structure. The control device 13 is a device that controls the entire position detection device and stores necessary data, and in addition to being given the coordinate position 〇 converted by the position data converter 12, A signal)-I P , a /phase signal/ from the encoder 5, a count i-value N from the counter 11, etc. are given. In addition, the counter 11 shows the origin value N7 in the origin adjustment operation described below! IN device 1
It is input from 3.

FIG. 5 is a schematic configuration diagram showing a J-bot arm as an example of the movable mechanism shown in FIG. In the figure, the movable mechanism 3 includes a fulcrum 31 and a rotation shaft 32 which are freely connected to the arm at 1, an arm 2 which is connected to the arm so as to be rotatable in the θ direction around the rotation axis 32, and an arm. It is composed of an end T effector 33 provided at the tip of A2. Although not shown, the rotary shaft 32 includes an encoder 5 and an encoder 5 for driving the arm A2. and an origin target position detector 7 (see FIG. 3).

FIG. 6 shows the rotation angle θ as the absolute position of the arm A2 shown in FIG. 4, and the aforementioned signals HP, z, and a.

The timing diagrams 1 to 1 show the relationship between b and N.

As shown in the figure, the rotation range of 2 to the arm θmin ~ θ
- point is the mechanical origin position θ. is determined and is 1Ila×. Mechanical origin position θ. is determined from the structure of the movable mechanism; for example, in the example shown in FIG.

As shown in Figures 6 (1) and (4), mechanical I
It is adjusted so that one of the /phase signals of the encoder 5 is generated when J5 is at the zero point position θ0, and this is called the Z-phase origin signal 2°.

Also, the mechanical origin position θ. The origin target position θHP is provided in the direction in which the rotation angle θ is smaller near . Origin target position θ14. corresponds to the generation position of one edge where the detection signal I P goes to the "T + '" level (J). Note that the detection signal HP goes to the "H" level at the point shown in Fig. 3. In the origin target position detector 7, the light shielding plate 8a
corresponds to the state where the photo sensor is at the 9 position.

FIG. 7 is a flowchart showing the procedure of origin alignment and origin adjustment of a conventional encoder using this position detection device. First, after turning on the power in step S1, the origin alignment operation in steps 82 to S4 is performed. In the origin alignment operation, in step S3, the origin target position θ11. Search for. Specifically, this corresponds to driving the arm Δ2 in FIG. 5 by the motor and searching for the position where the detection signal HP in FIG. Search for the Z rough origin signal Z that has a predetermined positional relationship with the target position θ□.In the example of FIG. It's a signal.

Z Kashiwa origin signal 2 is originally the mechanical origin position θ of arm A2. It should be set to match. However, when assembling a robot, these relationships may deviate. FIG. 6(2) shows an example in which, for example, the position coordinate θ of arm A2 is shifted by Δθ as a whole and becomes θ'. Here, coordinates θ and θ' indicate the same mechanical position of arm A2, but other signals HP, Z,
a.

There is a deviation in the relationship between b and N.

That is, actually the absolute position θ(-θ') of arm A2
The signals) -1p, z, a, and b are shifted from each other, but for convenience of illustration, the position coordinate θ is shifted to θ'. In such a case, the process proceeds from step S5 to step S6, and the mechanical origin position θ is determined. and 2 Kashiwa origin signal Z. It is necessary to adjust the origin to match the position of occurrence.

Now, by adjusting the origin up to step S4, arm A
is the Z coarse origin signal Z. It is located at the position θ' where . Here, θ′ 100′0+Δθ. The state of arm Δ2 at this time is shown by the broken line in FIG. In the conventional origin adjustment method, first, arm A2 is manually adjusted to the mechanical origin position θ. Match. After that, the encoder 5 is installed by adjusting the position or the positional relationship between the photosensor 9 of the origin target position detector 7 and the light shielding plate 8a, or both, and adjusting the position where the Z rough origin signal Z is generated and the mechanical origin of the arm A2. The positions θ0 are made to match. As a result, the position coordinate θ' in FIG. 6 is almost corrected to the correct position coordinate θ. After that, the process returns to step S2, and the origin alignment operation is performed again, and in step S5, the Z rough origin signal Z is output. detection position and the origin position θ of arm A2. Step S until exactly match
2 to repeat the procedure from step S6. Then, in step S5, the Z coarse origin signal Z is generated. The stopped position and the mechanical origin position θ of arm A2. If it matches,
In step S7, the origin value NZ is written into the counter 1, and the origin alignment and origin adjustment are completed.

(Problems to be Solved by the Invention) Conventionally, as described above, when the origin signal generation position of the encoder and the mechanical origin of the movable mechanism do not match, the mechanical It was necessary to perform origin adjustment to adjust the attachment, and it was also necessary to repeat the origin adjustment and origin alignment operations, so there was a problem that the adjustment required time and effort.

In addition, if the motor and encoder are integrated, it is difficult to adjust the position when installing the encoder as described above, so it is necessary to easily adjust the origin when using such a motor. There has been a desire to develop a position detection device that can do this.

(Object of the Invention) This invention was made to solve the problems of the prior art as described above, and when the origin signal generation position of the encoder and the mechanical origin position of the movable mechanism do not correspond, It is an object of the present invention to provide a position detection device for a movable mechanism that can easily adjust its origin.

(Means for Achieving the Object) In order to achieve the above-mentioned object, the present invention outputs a first pulse every time the movable mechanism operates by a unit displacement amount, and the movable mechanism an encoder that outputs a second pulse every time the encoder operates by an amount of displacement; a counter that counts the second pulse that the encoder outputs; and a counter that counts the second pulse outputted by the encoder; storage means for storing an origin correction value that is a difference between a count value and a count value of the counter at an origin target position n that is set near the mechanical origin position and causes the generation of the first pulse; By correcting the count value of the counter when the movable mechanism is at an arbitrary position with the origin correction value, the condition is established that when the movable mechanism is at the mechanical origin position, the count value of the counter becomes equal to the predetermined origin count value. The apparatus includes a calculation means for determining a suitable correction count value, and a position data conversion means for converting the correction count value into position data of the movable mechanism.

Note that in this Specification S, "position" and "displacement" are used in a broad sense including angles.

(Function) When the encoder origin target position and the mechanical origin position deviate from each other, a count value corresponding to the difference between these positions is stored in the storage means as an origin correction value. Then, based on this origin correction value and the count value of the counter, the correction count value obtained by the performance means is equal to the origin count value when the movable mechanism is at the mechanical origin, so it is essentially the origin adjustment. The corrected count value is given to the position data conversion means, so that the position of the movable mechanism can be detected correctly.

(Embodiment) FIG. 1 is a schematic block diagram showing the configuration of a position detection device with a variable f/1 mechanism, which is an embodiment of the present invention.

In the figure, the encoder 5 is linked to a motor that is a drive source of a movable mechanism (not shown) via a transmission mechanism so as to follow and rotate the motor. This encoder 5 outputs one A-phase signal a13 and one BK1 signal each having a mutual phase shift of 5)0 degrees each time it rotates by a certain angle smaller than one rotation by -1-9.
It has a function of outputting one seven-phase signal 2 every time it rotates, and is connected to the position counter 11 at the next stage. This position counter 11 is the A phase signal Q output from the encoder 5.
This is to input the a and B phase signals, detect the rotation direction and rotation amount (position n pulses) from their phase relationship, and obtain a count WXN by counting the pulses. The count value N of the position counter 11 is the
is added to the origin correction value ΔN stored in the origin correction value memory 15 to obtain a correction value l-(ii'I
It becomes No. Then, this corrected count value N. is given to the position data converter 12 and converted into the absolute position θ of the movable mechanism. The absolute position θ of the movable mechanism thus obtained is given to the control tlI15A position 13. The origin target position detector 7 is for detecting that the movable mechanism has reached a predetermined origin target position very close to the preset mechanical origin of the movable mechanism, and its specific configuration is as described above. Since this is the same as in the conventional example, the explanation will be omitted here. The control oil control device 13 is the i
It is a device that performs 7-phase signal Z from encoder 5, input signal Z from position counter 1 to run 1 (direct N, absolute position θ from position data converter 12, and stores necessary data. Origin target position detector 7
The detection signal [-1P is input from the machine, and when the origin is adjusted, it serves to set the origin !1flN7 on the device counter 1.

Next, the operating procedure of origin alignment and origin adjustment of the above-mentioned position detection device will be explained along the flowchart shown in FIG. In the following explanation, the configuration example of the movable mechanism shown in FIG. 4 and the output signal a of the encoder 5 shown in FIG.
, b, z or the output signal 1-( of the origin target position detector 7
Since the relationship between P and the arm device θ is the same as the conventional one, it will be explained with reference to these figures (X).

First, in step S11, after turning on the power, in step S11,
In steps 12 to 814, origin alignment is performed. These steps 812 to 814 are similar to steps 82 to S4 of the conventional origin alignment shown in FIG. That is, in step S13, the 7-mm A is driven and the origin target position θ1. Then, in step 814, an operation is performed to detect the Z Kashiwa origin signal 2. Z Kashiwa origin signal 2
The position where ° is detected is, for example, position θ'1 in FIG. 6, as in the conventional case.

Then, in step S15, the Z Kashiwa origin signal z is output.

At the detected position θ'1, the origin value N2 is written from the control device 13 to the position counter 1. As a result, even if the arm A2 is moved thereafter, the count value at the detection position 〇' of the second origin signal Z will always be the origin value N2. Then, with this position as a reference, the position counter 1 counts up or down the device pulses made up of the A-phase signal a and the B-phase signal S of the encoder.

Next, in step 816, the position θ'1 and the mechanical origin position θ are determined. Measure the deviation Δθ from That is, when the detection position θ'1 of the Z-axis origin signal 2° is at the position indicated by the broken line in FIG. 5, the mechanical origin (θ.=90°) of arm A2 is detected.
Measure the deviation Δθ from This measurement is performed by an operator using a predetermined ruler or the like.

In step 817, an origin correction value ΔN corresponding to the deviation Δθ is calculated using the following equation.

ΔN = Δθ·n (1) Here, n is a count value for a unit arm angle difference.

The origin correction value ΔN obtained in this manner is input to the origin correction value memory 15 shown in FIG. 1 from an external operation panel (not shown) or the like. The above simple operations complete the origin alignment and origin adjustment.

As a result of the origin alignment and origin adjustment as described above, the 6th
The arm position θ' and the signals HP, z, and a in the figure.

The relationship between b and N remains maintained. On the other hand, in FIG. 1, the count value N of the position counter 11 and the origin correction value ΔN are added by an adder 14 to obtain a correction count value N.

The position data is then given to the position data converter 12. As a result, the arm position θ' in FIG. 6 is effectively adjusted to the correct arm position θ, as shown below.

That is, when arm A2 is at position θ'0, count value N in FIG. 6(7) is (N2-ΔN). Therefore, the corrected count value N at this time becomes N2. Further, when arm A is at position θ'1, count value N is N2. Therefore, the correction count IN at this time
becomes (N2+ΔN).

On the other hand, as described above, the arm positions θ and θ' in FIG. 6 indicate the same mechanical position of the arm A2.

Therefore, the corrected count value N. is the mechanical origin position θ of arm A2. This means that the odor has been corrected to the origin value N2. As a result, the corrected count value N. The absolute position θ obtained by converting by the position data converter 12
is a value that accurately indicates the position θ of arm A2.

Note that the present invention is not limited to the above-mentioned embodiments, and for example, the following modifications are also possible.

■ The counter correction value ΔN in step 816 and step S17 in FIG. 2 is calculated by the operator measuring the angle deviation Δθ of arm A2 using a predetermined jig that also doubles as a ruler, and calculating from the deviation Δθ. It was. However, the invention is not limited to this, for example, after setting the origin 1i6N on the counter 1 at the generation position of the Z Kashiwa origin signal, the arm angle is set to the origin position θ. The count value N of position counter 1 at that position. Read the count value N. The difference between the origin value NZ and the origin value NZ may be determined as the counter correction value ΔN.

(2) If a nonvolatile memory is used as the origin correction value memory 5 shown in FIG. 1, there is an advantage that the origin adjustment only needs to be performed once, and there is no need to perform the origin adjustment when the power is turned on again. From the same point of view, the origin correction value memory 5 may be a switch or the like that can store the origin correction value ΔN even when the power is not turned on. In this case as well, the origin alignment operation is necessary when the power is turned on again.

(2) The encoder may be of an incremental type, and the present invention is also applicable to an encoder using a linear encoder.

<Effects of the Invention> As described above, according to the present invention, there is no need to adjust the mounting position of the encoder, etc., and the counting of the counter at the origin target position of the encoder (direct and mechanical origin of one movable structure) The count value is corrected based on the origin correction value, which is the difference between the count value of the counter at the position, and the origin adjustment is performed, so that the origin signal generation position of the encoder and the origin position of the movable mechanism match. This has the effect that even if the origin is not adjusted, the origin can be easily adjusted.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a position detection device for a movable mechanism which is an embodiment of the present invention, and Fig. 2 shows the operating procedure of origin alignment and origin adjustment.
Figure 3 is a schematic diagram of a hob showing a configuration example of the position detection H position of the movable mechanism, Figure 4 is a block diagram without showing the conventional position detection device of the movable mechanism, and Figure 5 is a configuration example of the movable mechanism. FIG. 6 is a timing chart showing the relationship between the position of the movable i-structure and each signal, and FIG. 7 is a flowchart showing the operating procedure of a conventional position detection device for a movable mechanism. 5... Encoder, 11... Position counter, 12... Position data converter, 15... Origin correction value memory, N... Count value, N
...Corrected Curran 1-value, N7...Origin value, ΔN
...Origin correction (direct

Claims (1)

[Claims] (1) an encoder that outputs a first pulse each time the movable mechanism moves by a unit displacement amount, and outputs a second pulse every time the movable mechanism moves by a smaller displacement amount than the unit displacement amount; a counter that counts the second pulse output by the encoder; a count value of the counter at a predetermined mechanical origin position of the movable mechanism; and a counter that is set near the mechanical origin position and counts the first pulse. storage means for storing an origin correction value that is a difference between the count value of the counter at the origin target position that causes the generation; calculating means for calculating a correction count value that satisfies a condition that the movable mechanism is equal to a predetermined origin count value when the movable mechanism is at the mechanical origin position; 1. A position detection device for a movable mechanism, comprising: position data conversion means for converting position data into a position data.