JPH0411345B2 - - Google Patents

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a working device equipped with a load sensor that detects a reaction force acting on an operating section attached to an operating head of the working device. The present invention relates to a device for correcting.

<Prior art> A work device equipped with a gripping claw is provided with a load sensor to detect the reaction force acting on the gripping claw, and the output of this load sensor is used to confirm the gripping of an article, control the gripping force, etc. Therefore, if the gain characteristics of the load sensor change, grip confirmation etc. cannot be performed accurately.

However, in conventional work devices, such changes in the gain of the load sensor cannot be automatically corrected, and there is a risk that inaccurate work may be performed due to changes in the characteristics of the load sensor.

<Object of the invention> Therefore, the present invention automatically detects the gain change of the load sensor using the movement of the operation part, and automatically performs correction based on this, so that work can be carried out reliably. The purpose of this is to ensure that the

<Structure of the Invention> The driving means opens and closes the gripping claw, and by this driving means, the first displacement applying means closes the gripping claw until a certain initial load is applied to the load sensor, based on the output from the load sensor, for example. relative displacement in the direction. Thereafter, the second displacement applying means further relatively displaces the gripping claws by a certain amount in the closing direction by this driving means.

The detection means detects the output fo of the load sensor when the initial load is applied and the output after a certain amount of relative displacement by the second displacement applying means, and the calculation means:
The amount of change in the characteristics of the load sensor is calculated from the output value detected by the detection means and the amount of increase in the load applied to the load sensor, and the correction means is configured to calculate the amount of change in the characteristics of the load sensor based on the amount of change calculated by the calculation means. Correct the output value of the load sensor.

<Examples> Examples of the present invention will be described below based on the drawings. In FIG. 2, 10 is a pair of gripping claws 12,
12, this working head 10
is supported movably in three dimensions by a support mechanism (not shown), and the servo motors SMX, SMY, SMZ
It is now being moved by

The gripping claws 12 are guided so as to be movable in a flat state on a support portion 11 integrally formed at the lower end of the work head 10, and are supported in a horizontal state and attached to both ends of a screw shaft 13 having reverse threads at both ends. Each part is screwed together. This screw shaft 13 is
It is connected via bevel gears 15a and 15b to a rotating shaft 16 that vertically passes through the center of the work head 10, and this rotating shaft 16 is connected to the output shaft of a servo motor SMU via a strain cylinder 17. has been done.

On the outer periphery of the strain cylinder 17, there is a load sensor 18 made of a semiconductor strain gauge or the like that indirectly detects the reaction force acting on the gripping claws 12 depending on the amount of strain in the strain cylinder 17.
is attached, and the output signal of this load sensor 18 is sent to the work head 10 via a slip ring mechanism 19.
It is now transmitted to the side.

Further, the support portion 11 is provided with a stopper 14 for the origin, which restricts the closed end of the gripping claw 12.

Next, to explain the configuration of the control circuit, the central processing unit 31 in the numerical control device 30 is configured by a microprocessor.
A memory 32, a data input device 33, and interfaces IF1 and IF2 are connected to the interface IF1, and servo motors SMX, SMY, and
Drive units DUX, DUY, DUZ, and DUU are connected to drive SMZ and SMU, respectively.
Further, the output of the load sensor 18 is supplied to the amplifier circuit 20 via the slip ring mechanism 19,
The output of this amplifier circuit 20 is supplied to a central processing unit 31 via an AD converter 21 and an interface IF2.

Next, to explain the operation of the central processing unit 31, the central processing unit 31 executes the program shown in FIG. Perform processing. That is, the central processing unit 31 repeats the processes (40) to (42) to remove the gripping claw 12 from the stopper 1 fixed to the work head 10.
4 and load sensor 18 as shown in FIG.
The pulse that closes the gripping claws 12 is distributed to the drive unit DUU until the output F of shows a predetermined initial load fo, and when it is detected that the initial load fo has acted on the gripping claws 12 (42), the gripping claws 12 are Minute amount Δl
The pulse for further closing is distributed to the drive unit DUU (43), and after this, the load sensor 18
The output F of is read again (44). And after this f
-fo is calculated to calculate the output change amount Δf, and this output change amount Δf and the load sensor 18
Find the deviation Δfε from the reference variation Δf _S measured and memorized at the time of assembly using the calculation Δf _S −Δf (45), store this in the variation register VR (46), and return to the main routine (not shown). do.

On the other hand, when performing normal work, the central processing unit 3
1 executes the process shown in FIG. 4 to check whether the article W is held. That is, first, a pulse is supplied to the drive unit DU in order to close the gripping claws 12 by a certain amount (50), and then the output value f of the load sensor 18 is read (51), and f'=f+(Δfε・X/
The correction value f' is approximately calculated using the correction formula Δl). In the above formula, X means that the gripping claws 12 are the article W.
This is the number of pulses distributed to the servo motor SMU after contact with the This is the output value of the load sensor 18 when there is no load sensor.

Then, it is determined whether or not this correction value f' exceeds the set value f _S (53), and if it is determined that it exceeds the set value f _S , the head movement routine (not shown) is performed and the head is moved to a predetermined position. If it is determined that the set value f _S has not been exceeded, the process returns to (50) and processes (50) to (52) are performed again so that the gripping claws 12 hold the article at the set load f _S. The same operation is repeated until W is grasped.

In the above embodiment, a pressing reaction force is applied to the gripping claws 12 by pressing the gripping claws 12 against the stopper 14 provided on the work head 10, but as shown by the two-dot chain line in FIG. It is also possible to attach the fixing block 23 to the fixed part and press the gripping claw 12 against the fixing block 23, thereby applying a pressing reaction force to the grasping claw 12.

The present invention can also be applied to output correction of a load sensor for detecting press force in a press-fitting device and a load sensor for detecting tightening torque in a nut runner.

<Effects of the Invention> As described above, in the present invention, a predetermined load is applied to the load sensor by bringing the gripping claw on the work head into contact with the contact portion, and the load applied to the load sensor is The configuration is configured to detect the amount of change in the output of the load sensor with respect to the change in size, derive the amount of change in the gain of the load sensor, and correct the output of the load sensor based on this, so the change in the gain of the load sensor can be corrected. This has the advantage that it can be automatically detected and corrected, and that gripping work etc. using a working device can be performed reliably.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram for clearly demonstrating the present invention.
2 to 5 show embodiments of the present invention,
FIG. 2 is a sectional view of the working head with a block diagram showing the control circuit, FIGS. 3 and 4 are flowcharts showing the operation of the central processing unit 31 in FIG. 2, and FIG. 3 is a diagram showing the relationship between the displacement of the claw 12 and the output of the load sensor 18. FIG. 10... Working head, 12... Gripping claw, 13...
... Screw shaft, 14 ... Stopper, 17 ... Strain tube,
18...Load sensor, 31...Central processing unit,
DUU...drive unit, SMU...servo motor.

Claims (1)

[Claims] 1. A working device equipped with a load sensor that detects an operation reaction force acting on a gripping pawl attached to a working head of the working device, including a drive means for opening and closing the gripping pawl, and a driving means for driving the gripping pawl to open and close the gripping pawl. a first displacement applying means for displacing the gripping claw in a direction to press it against the contact portion until the output of the load sensor acting on the load sensor reaches a set value; and a relative displacement of the gripping claw by the first displacement applying means. Further, a second displacement applying means for displacing the gripping claw by a certain amount in a direction of pressing the gripping claw against the contact portion by the driving means, and an operation that acts on the gripping claw by the second displacement applying means. a detection means for detecting the output of the load sensor in response to a reaction force; a calculation means for calculating the amount of change in characteristics of the load sensor based on the detection value detected by the detection means; and a correction means for correcting the output of the load sensor according to the amount of change in the output of the load sensor in a working device.