JPH0319778A - Screw tightening control device - Google Patents

Abstract

PURPOSE:To always stabilize tightening work even for unprepared input operation by providing constitution in such a way as using a fuzzy control to perform adjustment to an optimum tightening speed or tightening torque from an input quantity, applied by an operator, and the actual tightening speed or torque of a tool. CONSTITUTION:An input operational quantity is detected, further a speed or torque value of a screw tightening tool 6 is detected by a detcting device 7. Being based on these detection signals, by the fuzzy inference used with a membership function, a drive amount of the screw tightening tool 6 for performing the predetermined tightening action is calculated in a fuzzy processor 3. In accordance with this calculated drive amount, an output speed or output torque of a means (motor) 5 for driving the screw tightening tool 6 is adjusted by a motor driving circuit 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a screw tightening control device used in a power tool or the like for tightening screws or wood screws.

(Summary of the Invention) This invention uses fuzzy control from the input amount applied by the operator and the actual rotation speed or torque of the tightening tool.
This allows stable tightening work at all times by adjusting the tightening rotation speed or tightening torque to the optimum value.

<Prior art and its problems> In conventional screw tightening control devices for electric tools, etc., where the output of the drive motor is A, the torque is T, and the number of rotations is N, the output A is a function of the torque T and the number of rotations N. , that is, A=f (N
, T).

Further, the output A is also a value corresponding to the amount of manual operation from a power tool such as a bistorusu tip.

Therefore, when attempting to tighten screws with these power tools, constant speed control or constant torque control is required.

Normally, in order to achieve these controls, the rotational speed or torque value is detected and the detected value is input to the foot hook circuit for control. This foot hook circuit is made up of analog elements and is incorporated into the power tool itself.

In the case of the conventional constant speed control device configured in this manner, as long as the same input amount is applied, the drive torque is adjusted to iJfl so that the same rotational speed is maintained even if the load torque fluctuates. For example, when this device is tightening a wood screw, the load torque increases in the latter half, but the constant speed control device operates to increase the output so as not to reduce the rotational speed.

However, in the case of this device, when the load 1·Lux increases and the output is amplified in the latter half, the operator often ends up pulling in the pistol switch with too much force.
As a result, excessive torque is applied to the wood screw, which may damage the mating material.

Similarly, in the case of a conventional constant torque control device, as long as the same input amount is applied, the rotation speed is adjusted to maintain the same torque even if the rotation speed changes. For example, when using this device to tighten a screw into a female metal thread, the load torque increases at the end and the rotational speed decreases accordingly.The constant torque control device operates to reduce the tightening torque and tighten the screw head. This prevented tool groove damage.

However, in the case of this device, when the rotation speed decreases in the second half and the output is reduced, the operator may inadvertently loosen the pistol switch and tighten the &J too loosely, or may force the screw 1-rusuinochi to be pulled in. It has passed,
The tool groove on the screw head may be damaged.

Furthermore, if the control outputs of both of the above-mentioned control devices are made to have a high degree of accuracy, the circuit configuration of the devices becomes complicated, and furthermore, it becomes difficult to derive a theoretical formula for calculating the output power.

Similarly, these control devices have problems such as not necessarily being able to follow sudden changes in load.

《Object of the invention》 This invention was made to solve the above problems, and its purpose is to provide a stable output even if the operator changes the operation amount carelessly. Moreover, it is an object of the present invention to provide a screw tightening control device that has high precision, excellent followability, and has a simple circuit configuration.

3 <Structure and Effects of the Invention> In order to achieve the above object, the present invention provides a means for detecting the input operation amount, a means for detecting the rotational speed or torque value of a screw tightening tool, and a means for detecting both of the above. From the output of the means,
Means for calculating the drive amount of a screw tightening tool to perform a predetermined tightening operation by fuzzy inference using a member symbu function, and output rotation speed or output torque of the means for driving the screw tightening tool according to the calculated drive amount. It is characterized by having a means for adjusting.

In this way, this invention uses fuzzy control to determine the optimum tightening rotation speed or tightening torque based on the input amount applied by the operator and the actual tightening tool rotation speed or torque. This enables stable tightening work at all times even when input operations are performed.

Furthermore, by using fuzzy inference in the control section, the control section can be made small and simple, and the processing speed can be increased, improving responsiveness and follow-up performance.

- 4 - Furthermore, by using fuzzy rules, it is easier to set the optimal output amount according to the detected value of each detection means, and the set fuzzy rules can also be changed and modified as necessary. There is an ease with which you can do it.

(Explanation of Examples) Next, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing a case where the screw tightening control device according to the present invention is applied to constant rotation speed control.

In the figure, the piston I/le switch 1 detects the retraction amount of the pistons 1 to 1 and sends it to the input conversion circuit 2.

The human power conversion circuit 2 converts the input trigger pull amount into an input amount X, and sends it to the fuzzy processing device 3.

The fuzzy processing unit W3 uses fuzzy rules set in advance according to the input 4] The optimal output value is calculated by fuzzy inference, the result is defuzzified, and the obtained output amount Y is sent to the motor drive circuit 4.

The mork drive circuit 4 supplies a drive current with a duty ratio corresponding to the output amount Y to the motor 5.

The motor 5 is rotationally driven by a manually applied drive current, drives the tightening tool 6 while maintaining a set rotation speed, and simultaneously sends a rotation signal to the rotation speed detection device 7.

The rotation speed detection device 7 detects the rotation speed of the mork 5 and sends it to the fuzzy processing device 3.

In other words, in this screw tightening control device, the input amount X corresponding to the trigger operation amount input from the pistol switch 1 is
From the returned rotational speed N of the moke 5, fuzzy inference can be made to determine the output amount Y to keep the rotational speed of the tightening tool 6 constant even if the rotational speed is about to change due to fluctuations in the load torque. Calculated by Similarly, even if the trigger is operated and the input amount X fluctuates, the output amount Y for making the tightening operation appropriate can be obtained.

FIG. 2 is a diagram showing an example of fuzzy rules set in the fuzzy processing device 3.

The fuzzy rule set here is Ifthen (
These are called rules (if, then), and include, for example, the following rules:

(Rule 1) If the input quantity χ is a medium negative value and the rotational speed N is zero, set the output quantity Y to a medium positive value.

This rule can be expressed simply as follows.

If X=NM and N=ZRthen
Y=PM A plurality of rules obtained in this way are shown in FIG.

Linguistic expressions used in rules here (fuzzy rahel)
NL is a large negative value, NM is a medium negative value, NS
is a small negative value, ZR is almost zero, PS is a small positive value,
PM represents a truly medium value, and PL represents a truly large value.

Furthermore, these rules can be changed or added to more appropriate ones depending on the application of the screw tightening control device and the situation of the object to be controlled.

FIG. 3 shows the input amount x2 input to the fuzzy processing device 3.
It is a graph showing a member simp function used when fuzzyizing the rotation speed N and further defuzzifying the calculation result into a specific output amount Y.

Figure a shows a Menhaship function representing the degree of compatibility between the input quantity X and each fuzzy rahel. Figure b is a Menha Symp function representing the number of rotations N and the degree of fitness of each fuzzy rahel. The horizontal axis of each of these figures represents specific detected values. Further, Figure C shows the membership function regarding the output i1Y. These member synoptic functions are optimally set according to the specific capacity of the mork 5, tightening load, etc. In addition, the shape of these Menchasimp functions can also be set to any shape other than a triangle, such as a trapezoid.

The fuzzy rules shown in FIG. 2 are used in the case of constant rotation speed control, and by setting these rules, the fuzzy processing device 3 can control the human power iX and the rotation speed N.
When input, the goodness of fit of the Menhasisop function in the fuzzy rule described above is calculated, and the well-known MIN-
The output amount Y is calculated using a fuzzy inference method such as MAX calculation.

By adjusting the duty ratio of the drive current by the motor drive circuit 4 according to the obtained output amount Y, the rotation of the motor 5 is always kept constant, and even if there is a change in the amount of retraction of the trigger of the bistorusu inochi 1, Stable tightening work can be performed even when the load fluctuates.

Note that the rotation speed detection device 7 in the above embodiment is replaced with a torque detection device, and the fuzzy processing device 3 detects the detected torque T.
By performing fuzzy inference based on this, constant torque control can be realized. Of course, the fuzzy rules and Menchasimp functions in that case are set for constant l-lux control.

By constructing these embodiments as described above, the following effects can be obtained.

(1) Even if it is not possible to derive a theoretical formula for correcting fluctuations in rotational speed N or 1·Lk T to a constant level, modify the fuzzy rules shown in Figure 2 as appropriate and repeat the trial. Appropriate fuzzy rules are then set to enable comprehensive control.

(2) By modifying the Menharship function shown in Figure 3, it is possible to improve the ability to follow sudden changes in the rotation speed N and torque T. Even if the temperature drops to zero, by setting a corresponding fuzzy rule in advance, it is possible to restore it smoothly, and it is possible to provide an excellent function in terms of safety design.

(3) It is possible to design with consideration for human ease of use. In other words, when the load torque increases by 1 and the rotational speed decreases, the operator reflexively pulls in the pistol switch and tries to restore the rotational speed, but if the amount of retraction is large, the rotational speed is instantaneously over-increased. It is conceivable that this may be increased. In this case as well, by modifying the member symp function shown in FIG. 3 in consideration of human reflex characteristics and changing the fuzzy rules through repeated trials, it is possible to obtain an apparatus that can sufficiently respond to human operating characteristics.

[Brief explanation of the drawing]

FIG. 1 is a brochure diagram showing the case where the screw tightening control device according to the present invention is applied to constant rotation speed control, and FIG. 2 is a diagram showing an example of fuzzy rules set in the fuzzy processing device.
FIG. 3 is a graph showing the menharship function set in the fuzzy processing device. 1... Bistonless inch 2... Input conversion circuit 3... Fuzzy processing device 4... Mork drive circuit 5... Mork 6... Tightening tool 7... Rotation speed detection device・・Input amount N・・Rotation speed Y・・Output amount

Claims (1)

[Claims] 1. Means for detecting the input manipulated variable; Means for detecting the rotational speed or torque value of a screw tightening tool; Fuzzy inference using a membership function from the outputs of both of the above detecting means. means for calculating the drive amount of the screw tightening tool to perform a predetermined tightening operation; and means for adjusting the output rotation speed or output torque of the means for driving the screw tightening tool according to the calculated drive amount. A screw tightening control device characterized by comprising: