JPH0447639Y2 - - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a device that can detect reaction force acting on a tool without being affected by gravity or the like.

B. Summary of Disclosure When performing grinding work, etc., gravity acts on the tool in addition to the grinding force. Therefore, when detecting the force exerted by a tool, it is necessary to remove the influence of gravity, but converting this into a digital signal and processing it requires a large-scale system. Therefore, the influence of gravity is detected by a separate load cell, and these signals are subtracted as analog signals by a differential amplifier, so that only the reaction force acting on the tool can be determined.

C. Prior Art The movable device shown in FIG. 9 consists of a fixed part 5 and a movable part 6, and a force sensor part shown in FIG. 8 is interposed between the movable part 5 and the tool 7. . The movable part 6 rotates as shown by the two-dot chain line in FIG. 9, so that the cutting tool 8 of the tool 7 grinds the object 9 in each posture. The force sensor section shown in FIG. 8 includes a tool side flange 1 and a movable device side flange 2.
A reaction force load cell 3 is interposed between the two, and the reaction force load cell 3 is equipped with a plurality of 3-component force measuring gauges 4 so that the 3-component force can be detected.
is provided.

When performing grinding work using the above-mentioned movable device, it is necessary to always push the object to be ground with a constant grinding force F. Since the detection is performed, the output value changes when the posture changes. Therefore, in order to be able to adapt even when the posture of the movable device changes, as shown in FIG. 10, the signal is converted into a digital signal and arithmetic processing is performed. That is, the signal from the force sensor unit 10 is amplified by the signal amplification circuit 11, A/D converted by the A/D converter 12, and inputted to the arithmetic processing unit 13 as sensor data, while the posture of the movable device is detected by the position detector 14. Detected by the interface circuit 15
is input to the arithmetic processing unit 13 as position data. The arithmetic processing unit 13 outputs only the reaction force F acting on the tool 7 as force data from the sensor data and position data.

D Problems to be solved by the invention In the conventional technology described above, the grinding force is determined by correcting and removing the gravity from the signal from the force sensor. Since a position detector, its interface circuit, and arithmetic processing unit are required to detect changes in the position, the system becomes large-scale and costs increase.

In view of the above-mentioned prior art, the present invention is composed of a force sensor section 16 and a signal amplification circuit 17 as shown in FIG.
It is an object of the present invention to provide a force detection device that can be used as force data of only reaction force acting on a tool by performing A/D conversion using a converter 18.

E Means and action for solving the problem The force detected by the reaction force load cell includes not only the reaction force acting on the tool but also the gravity of the tool itself, which is the first differential force. It will be amplified by an amplifier. On the other hand, the gravity correction load cell detects the gravity of the weight, and this is amplified by the second differential amplifier. At this time, the gain of the second differential amplifier depends on the mass ratio of the tool and the weight. It will be changed accordingly. Therefore, first,
When the signal from the second differential amplifier is subtracted by the third differential amplifier, only the reaction force of the tool can be determined.

F. Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a force sensor used in an embodiment of the present invention. As shown in the figure, the force sensor section includes a reaction force load cell 23 and a gravity correction load cell 25 between the tool side flange 21 and the device side flange 22.
It is constructed by intervening. The reaction force measurement load cell 23 includes an annular portion 23a and a disk portion 2 concentric with the annular portion 23a.
3b are connected via four connecting parts 23c, the disc part 23b is fixed to the tool side flange 21, and the annular part 23a is fixed to the gravity correction load cell 25. The connecting portions 23c are arranged at 90° intervals, and each connecting portion 23c is provided with four strain gauges 24 (therefore, a total of 16 strain gauges 24a to 24p) symmetrically. On the other hand, the gravity correction load cell 25 has an annular portion 25a.
and a concentric weight 27 are connected by four connecting parts 25c, and the annular part 25a is fixed to the device side flange 22 and the reaction force load cell 23. The connecting portions 25c are arranged at 90° intervals,
Each connecting portion 25c has four strain gauges 26 symmetrically (therefore, a total of 16 strain gauges 26a-
26p) is provided. The weight 27 has an annular shape, and a stopper 28 passes through the center thereof. The stopper 28 is provided protruding from the center of the device load cell 22.

The force sensor configured as described above is provided with strain gauges 24 and 26 so as to be able to detect three components of force, but since the operating principle is the same for all three components, the signal amplification circuit will be explained for one component. do.

FIG. 4 shows an embodiment of the signal amplification circuit. As shown in the figure, the reaction force load cell 23
The strain gauge resistances R _b , R _d , R _j , R _l
(The subscript corresponds to the strain gauge. The same applies below)
The bridge is constructed by and the strain gauge resistance R _b for the gravity correction load cell is
It is composed of R _d , R _j , and R _l , and a predetermined voltage is applied to these bridges. Therefore,
When the equilibrium state of each bridge collapses, the potential difference within each bridge is amplified by each differential amplifier 30 and 31 to become e ₁ and e ₂ , and the outputs e ₁ and e ₂ are subtracted by differential amplifier 32. be done. Here, e ₁ , e ₂ , e ₀
is shown by the formula below.

e ₁ = K ₁ (F + W ₁ ) e ₂ = K ₂ W ₂ e ₀ = e ₁ −e ₂ = K ₁ F + K ₁ W ₁ − K ₂ W ₂ However, F is the reaction force (grinding force) that the tool receives, W ₁ is the gravity acting on the tool, W ₂ is the gravity acting on the weight, K ₁ is the gain due to the differential amplifier 30, and K ₂ is the gain due to the differential amplifier 31.

Also, W ₁ = M ₁ g, W ₂ = M ₂ g where M ₁ is the tool mass, M ₂ is the weight mass, and g is the gravitational acceleration.

Therefore, if K ₁ W ₁ −K ₂ W ₂ = 0, the influence of gravity is completely removed from the output of the differential amplifier 32, so the gain K ₂ of the differential amplifier 31
=K ₁ W ₁ /W ₂ =K ₁ M ₁ /M ₂ . Furthermore, even if acceleration α occurs in addition to gravitational acceleration, its influence is removed. That is, as shown in the equation below, the same gain setting is sufficient even in the case of gravitational acceleration.

K ₂ = K ₁ F ₁ /F ₂ = K ₁ M ₁ α / M ₂ α = K ₁ M ₁ /M ₂ However, F ₁ is the force that causes acceleration α on the tool, and F ₂ is the force that causes acceleration α on the weight. It is the force that causes

Furthermore, if the same tool is used while attached to the movable device, the gain of the differential amplifier 31 may be set by the volume, but this is inconvenient if the tool is automatically replaced. Therefore, in such a case, as in the other embodiments shown in FIGS. 5 and 6, the differential _amplifier 31 is
It is better to make the gain variable. That is,
In the embodiment shown in FIG. 5, by using a multiplier 33, the gain of the differential amplifier 31 is made variable by an external control signal e _c . Further, in the embodiment shown in FIG. 6, a D/A converter 34 is added so that the gain of the differential amplifier 31 can be set using a digital signal. In addition, other configurations are as follows.
This is similar to the embodiment shown in FIG. Furthermore, in the embodiments described above, the selection of strain gauge resistors constituting the bridge is not limited to those exemplified above, and can be changed as appropriate depending on the direction of the force to be detected.
Furthermore, it is not necessary to use strain gauge resistors as all the resistors of the bridge; at least one strain gauge resistor may be used and the others may be fixed resistors.

Furthermore, since the strain gauge signal is weak, it is desirable to keep the wiring as short as possible. Therefore,
As shown in FIG. 7, it is preferable to mount the force sensor section 35 and the signal amplification circuit 36 in the same package as a force sensor unit 37. This has the advantage of being less susceptible to noise, leading to improved reliability, and making it easier to interface with other equipment such as a sequencer.

G. Effects of the invention As specifically explained above based on the embodiments, the invention has the following effects.

(1) The influence of gravity on the tool and the influence of acceleration of the movable device can be canceled in real time, and the actual reaction force (grinding force) being applied to the tool can be detected without using a microcomputer.

(2) The system has a very simple configuration because it does not require calculations by a microcomputer.

(3) Since microcomputer calculations are not required, there is no delay in computer calculations and the response is good.

[Brief explanation of the drawing]

Figures 1 to 7 relate to embodiments of the present invention;
The figure is a cross-sectional view showing an example of the force sensor section, Figures 2a and b are a front view and a cross-section of a load cell for measuring reaction force, and Figures 3a and b are a front view and a cross-section of a load cell for gravity correction. 4, 5, and 6 are block diagrams showing the first, second, and third embodiments of the signal amplification circuit, respectively, FIG. 7 is a configuration diagram of the force sensor unit, and FIG. A cross-sectional view showing a conventional force sensor section,
Fig. 9 is an explanatory diagram showing the position of the movable part of the movable device and the load component force, Fig. 10 is a conventional force measurement block diagram,
FIG. 11 is a force measurement block diagram of the present invention. In the drawing, 21 is a tool side flange, 22 is a device side flange, 23 is a load cell for measuring reaction force, 24,
26 is a strain gauge, 25 is a gravity correction load cell, 27 is a weight, 28 is a stopper, 30,
31 and 32 are differential amplifiers, 33 is a multiplier, and 34 is a D/A converter.

Claims (1)

[Claims for Utility Model Registration] (1) A force sensor section and amplifying the signal of the force sensor section;
In a force detection device comprising a signal amplification circuit for calculation, the force sensor section includes a tool-side flange for attaching a tool, a device-side flange for fixing to a movable device, and a device-side flange for detecting reaction force caused by the tool. The signal amplification circuit includes a reaction force load cell, a weight for correcting gravity or other acceleration, and a gravity correction load cell for detecting the force acting on the weight, and the signal amplification circuit is configured to detect the signal of the reaction force load cell. a first differential amplifier that amplifies the signal of the gravity correction load cell, a second differential amplifier that amplifies the signal of the gravity correction load cell, and subtracting the output of the second differential amplifier from the output of the first differential amplifier. A gravity-corrected applied force detection device comprising: a third differential amplifier that calculates only the reaction force acting on the tool. (2) Utility model registration Claim 1, wherein the gain of the second differential amplifier is made variable by a multiplier when an external analog voltage signal is input. Detection device. (3) Utility model registration Claim 1, characterized in that the gain of the second differential amplifier becomes variable by a multiplier and a D/A converter when an external digital signal is input. Gravity correction force detection device. (4) Utility Model Registration Claim 1: The gravity-corrected applied force detection device, characterized in that the force sensor section and the signal amplification circuit are mounted in the same package.