JPS59187493A - Detector for change of characteristic of load sensor in working device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention detects a change in the characteristics of a load sensor that detects a reaction force acting on an operating part such as a gripping claw attached to a working head of a working device. This relates to a device for

<Prior art> In a working device equipped with gripping claws, a load sensor is provided to detect the reaction force acting on the gripping claws, and the output of this load sensor is used to confirm the gripping of an article, control the gripping force, etc. Therefore, if the characteristics of the load sensor change or break down, it will no longer be possible to accurately check the grip.

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

<Purpose of the Invention> Therefore, an object of the present invention is to enable automatic detection of changes in the characteristics of such a load sensor, thereby enabling recalibration of the load sensor, determination of failure, etc. It is.

<Configuration of the Invention> FIG. 1 is an overall configuration diagram for clearly explaining the present invention. The displacement applying means (53) relatively displaces the gripping claw (operation part) 12 in the closing direction until a certain initial load is applied to the load sensor 18 based on the output signal from the load sensor 18, for example, and then further displaces the gripping claw (operation part) 12. 12 by a certain amount.

The determining means (55) detects the output of the load sensor 18 after closing the gripping claws 12 by a certain amount, determines whether it is out of a certain range, and outputs, for example, an abnormal signal if it is out of a certain range. do.

<Example> Embodiments of the present invention will be described below based on the drawings.

In FIG. 2, reference numeral 10 denotes a working head equipped with a pair of gripping claws 12, 12. This working head 10 is supported movably in three-dimensional directions by a circuit support mechanism, and is moved by servo motors SMX, SMY, and SMZ. It is now possible to do so.

The gripping claw 12 is guided so as to be horizontally movable on a support portion 11 integrally formed at the lower end of the work head 10, and is supported horizontally by a screw shaft 13 having reverse helices at both ends. Both ends are screwed together. This gear l1iIII13 is a bevel gear 15a, 1
5b, it is connected to a rotating shaft 16 that vertically passes through the center of the work head 10, and this rotating shaft 16 is connected to an output shaft of a servo motor SMU via a strain tube 17.

A load sensor 18 made of a semiconductor strain gauge or the like is attached to the outer periphery of the strain tube 17 to indirectly detect the reaction force acting on the gripping claw 12 depending on the amount of strain in the strain tube 17. The output signal is transmitted to the work bed 10 via the slip ring mechanism 19.

Further, the support portion 11 is provided with an origin stopper 4 for regulating 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, and this central processing unit 31 includes a memory 32,
A data input device 33, an ink face IFI, and an IF2 are connected, and a servo motor S is connected to the ink face IFI.
Drive units DUX, DUY, DUZ, and DUU that drive MX, SMY, SMZ, and SMU, respectively, are connected. Further, the output of the load sensor 18 is supplied to the amplifier circuit 20 via the slip ring mechanism 19, and the output of this amplifier circuit 20 is supplied to the central processing unit 31 via the AD converter 21 and the ink face IF 2. It looks like this.

When carrying out the traversing work, the central processing unit 31 executes the process shown in FIG. 3 to check whether the article W is being held. That is,
First, a pulse is supplied to the drive unit D tJ tJ in order to close the gripping claw 12 by a certain amount (40), and then the output value of the load sensor 18 is read (41). and,
Add the correction value in the correction register CR to this read value (
42,), it is determined whether this correction value exceeds the set value fs or not.43) If it is determined that it exceeds the set value f5, the circuit moves to the head movement routine and performs a predetermined operation. If it is determined that the set value fS is not exceeded and 1ζ is not exceeded, return to (40) and perform steps (40) to (42).
The same operation is repeated until the gripping claws 12 grip the article W with a predetermined force.

On the other hand, before starting the input work program, the central processing unit 31 executes the program shown in FIG. 4 to calibrate the load sensor 18 and check for abnormalities. That is, by repeating the processes (50) to (52), the central processing unit 31 causes the gripping claws 12 to come into contact with the flange 14 fixed to the work head 10, and the output of the load sensor 18 or the predetermined value. Initial load [drive unisolated until it shows 0] A pulse that closes the gripping claw 12 is distributed to DUU, and when it is detected that the initial cart fo has acted on the gripping claw 12 (52), the gripping claw 12 is lowered by a constant minute amount Δβ Distribute the pulse for further closing to the drive unit += D U Ll53)
, After this, the output F of the load sensor 18 is read again (54
). Then, it is determined whether the read output F of the load sensor 18 is within the range of AL to AH which is considered to be the limit range of use (55), and if it is not within this range, an abnormality is displayed (55). 56), stop work.

Further, as shown in FIG. 5, the output F of the load sensor 18 is A
If it is in the range of ~AH, then further A~A +-
Normal range N~Nl-1 set sufficiently narrower than 1
57), and if it is outside the range, calculate the deviation amount ΔF between the detected value F and the standard value by calculating F-fS, and store this in the correction register. Cent to CR (58). As a result, when the gripping confirmation routine described above is executed again, the output of the load sensor 18 is corrected according to the contents of the correction register CR, and changes in the characteristics of the load sensor 18 are corrected with high accuracy.

In the above embodiment, a pressing reaction force was 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. The fixing block 23 may be attached to the fixed part and the grasping claw 12 may be pressed against the fixing block 23 to apply a pressing reaction force to the grasping claw 12. As shown in FIG. 6, the grasping claw 12 may be closed. By making the stoppers 12a provided on each of the gripping claws 12 come into contact with each other, and by bringing the stoppers 1-2a of the gripping claws 12 into contact with each other, a reaction force is applied to the gripping claws 12. It's fine.

Further, in the above embodiment, either the gripping claw 12 or the stopper 1
By rotating the servo motor SMU a certain amount after contacting a contact member such as 2a, a certain reaction force was applied to the gripping claws 12. A constant reaction force may be applied to the gripping claws 12 by moving the gripping claws 12 until the output of the current detector reaches a set value.

Furthermore, as shown in FIG. 7, the gripping claw 12 is moved until the output of the load sensor 18 reaches the set value rs, and the drive current of the servo motor S M U or the gripping claw 1 at this time is
This driving current or the gripping claw 12 is detected.
The need for calibration of the load sensor 18 and the presence or absence of an abnormality may be determined based on whether or not the position is outside the allowable ranges A to A H, N L to N H. The flowchart in FIG. 8 shows the processing of the central processing unit 31 in this case.

The present invention can also be applied to detecting changes in characteristics of load sensors for detecting press force in engineering equipment and load sensors for detecting tightening torque in nut runners.

<Effects of the Invention> As described above, in the present invention, a constant pressing force is applied to the operating part by using the movement of the operating part on the work head, and the output of the load sensor in this state is detected. Based on the relationship between the magnitude of this detected value and the pressing force acting on the operating section, it is possible to detect changes in the load sensor's characteristics from the predetermined characteristics, so changes in the characteristics of the load sensor can be automatically detected. It becomes possible to do so. Therefore, it becomes possible to automatically calibrate the load sensor or check for abnormalities, which has the advantage of greatly improving the reliability of the working device.

[Brief explanation of drawings]

Figure 1 is an overall configuration diagram for clearly demonstrating the present invention, Figures 2-
FIG. 8 shows an embodiment of the present invention, FIG. 2 is a sectional view of the working head and a block diagram showing the control circuit, and FIGS. 3 and 4 are the central processing unit in FIG. 2. 3
1, a flowchart showing the operation of the gripping claw 12, FIG.
Fig. 6 shows the relationship between the displacement of the load sensor 18 and the output of the load sensor 18.
FIG. 7 is a partial cross-sectional view of a working head showing another embodiment of the present invention, FIG. 7 is another diagram showing the relationship between the displacement of the gripping claw 12 and the output of the load sensor 18, and FIG. 8 is a modification of the present invention. 3 is a flowchart showing an example. 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. Patent applicant: Toyoda Machine Tool Co., Ltd. Figure 5F Figure 6

Claims (1)

[Claims] (1) A characteristic change detection device for a load sensor in a working device having a load sensor that detects an operation reaction force acting on an operating portion such as a gripping claw attached to a work head of the working device, a displacement applying means for displacing the operating section in a direction of pressing the operating section against the contact section until the operation reaction force to be applied or the output of the load sensor reaches a set value; and after the relative displacement of the operating section by the displacement applying means; and determining means for detecting a change in the characteristics of the load sensor when the relationship between the magnitude of the output of the load sensor and the operation reaction force acting on the operation section deviates from a predetermined range. A device for detecting changes in characteristics of load sensors in working equipment.