JPS5872277A - Processing method for component force in touch type coordinate input device - Google Patents

Abstract

PURPOSE:To remove troubles due to a hinged joint and maintain a linear property by finding the coordinates of a force-applied point relating to a non-linear property from a component force signals of a strain gauges sticked to the surface of plate springs. CONSTITUTION:A face plate 12 is coupled with a supporting frame 14 through plate springs 13 and both the ends of the plate springs 13 are coupled with the face plate 12 and the supporting frame 14. Strain gauge 15 are sticked to the surface of the springs 13 and strain signals epsilon1, epsilon2, epsilon3, epsilon4 corresponding to the bending deformation of springs 13 are outputted. On the basis of the formula 1, the coordinates of a force-applied point P (x, y) are found from the strain signals epsilon1, epsilon2, epsilon3, epsilon4 having non-linear relation to the coordinate values P (x, y) and undifined factors a0-an, b0-bn.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting component force signals output from a force detector of a force-sensing deaf-touch coordinate input device (hereinafter abbreviated as a touch panel), which is mainly used as a coordinate input device in the computer application field. This relates to a processing method.

Conventional coordinate input devices include those that use electromagnetic force, static electricity, light pens, etc., but these require special pens and are inconvenient to use. To improve this inconvenience, several methods have been proposed that allow coordinates to be easily input by touching with a finger or the like. Among them, regarding touch panels using force detection method,
Its principle and basic configuration are known from Japanese Patent Publication No. 49-34247.

FIG. 1 shows the basic configuration of the above-mentioned known example. The principle is 3
The outputs of the force detectors 1.2.3 are processed using a nine-point calculation formula using force and moment balance conditions, and the coordinates of the position 5 of the force acting on the face plate 4 are determined. However, in this method, the joint between the force detectors 1, 2.3 and the face plate 4 needs to be a sliding joint, which results in a complicated structure. Also,
Since the force detectors 1, 2.3 receive forces that change between positive and negative, the detection mechanism needs to be devised.

Figure 2 shows a known example of force detection ability (Utility Model Application No. 55-100136
No.). In this case, a recess 6 is provided in the face plate 4 and a protrusion 8 is provided in the support 7 to realize a sliding joint. The force is measured by a strain gauge 11 attached to the surface of a leaf spring 10 that connects the support 7 and the support frame 9.
In this example, there is a possibility that an error may occur due to the non-linearity of the friction characteristics between the recess and the protrusion, and troubles due to dirt entering the recess and a decrease in accuracy due to wear of the protrusion are expected. Furthermore, due to the influence of backlash between the recess and the protrusion, it becomes difficult to ensure linearity when the force is switched between positive and negative.

The purpose of the present invention is to realize a face plate support structure that does not require a slide in the face plate support part, in order to eliminate various difficulties caused by the slide, and which has nonlinearity due to the elimination of the slide. The present invention provides a method for processing component force signals.

An embodiment of the present invention will be described below with reference to FIG. Third
In the figure, the face plate 12 is connected to the support frame 14 via four leaf springs 13, and both ends of the leaf springs 13 are attached to the face plate 1.
2 and the support frame 14. A strain gauge 15 is attached to the surface of the leaf spring 13, and outputs a strain signal corresponding to the bending deformation of the leaf spring. 16 indicates the position of force.

Now, when a suitable orthogonal coordinate system is set on the face plate 12 and a force is applied to one point P (x, y), strain signals ε1, ε2, ε3, and ε4 are generated from the four strain gauges 15, respectively. Monotosu. Generally, the coordinate values x and y of the force application point and the strain signals ε1, ε2, ε3. A linear relationship does not hold between ε4. Therefore, undetermined coefficients a0, a1, a2..., b
0.

Let's introduce b1, b2... and express the relationship between them as follows, for example: x=a0+(a1ε1+a2ε2+a3ε3+a4ε4
)+(a5ε12+a6ε1ε2+a7ε1ε3+a8
ε1ε4+a9ε22+a10ε2ε3a11ε2ε3
+a12ε32+a13ε3ε4+a14ε42)+(
a15ε13+...)+...(1) y=b0+(b1ε1+b2ε2+b3ε3+b4ε4
)+(b5ε12+b6ε1ε2+b7ε1ε3+b8
ε1ε4+b14ε42)+(b15ε13+...+)
...(2) Here, εi=ε1/(ε1+ε2+ε3+ε4) (i=1, 2
, 3, and 4) are each proportional to the magnitude of the applied force, so if ε1 is used instead of ε1, the influence of the magnitude of the applied force can be eliminated.

Now, if we take up to the quadratic term of ε as approximate expressions for equations (1) and (2), the undetermined coefficients are a0, a1, ... a14, b0
, b1, . . . b14. To determine these, proceed as follows. First, select an appropriate point on the panel (x1
, y1). At this time, the output ε1 of each strain gauge
Find ε1 to ε4 from ~ε4 and use (I) with x1 and y1
, substituting into the approximate expression of equation (2), εj, bj (j=0
. 1, 2. ..., 14) is an unknown quantity. Below, different points (xR, yR) (R=2, 3, 4
...If you apply force to 15) and repeat the same operation, 3
0 equations are created. If these are solved as simultaneous −order equations, all undetermined coefficients can be found.

A microcomputer equipped with a touch panel device has
If we give the approximate expressions (1) and (2) and the values of the coefficients found above, we can calculate the coordinates (x, y) of the addition point when force is applied and ε1-ε4 is output. You can find the value.

Note that the functional forms of equations (1) and (2) are not limited to polynomials, and functions of various forms can be applied.

As described in detail above, by employing the component force signal processing method of the present invention, it is possible to eliminate slips from the face plate support portion of a touch panel, and various difficulties caused by the presence of slips, such as slips, can be eliminated. It is possible to prevent detection errors in coordinate values due to the frictional characteristics of the joints, troubles caused by dirt entering the joints, and decreased accuracy due to wear of the joints.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the basic structure of a touch panel, FIG. 2 is a cross-sectional view of a force detection section of the touch panel, and FIG. 3 is a schematic diagram of an apparatus for implementing the method of the present invention. 12... Face plate, 13... Leaf spring, 14... Support frame, 15... Strain gauge.

Claims (1)

[Claims] A face plate supported without using slides at three or more points, a force detection device installed at each support point, and the coordinates of the force application point on the face plate by processing the detected force signal. In a touch-type coordinate input device that has an arithmetic circuit that has the function of calculating A component force signal processing method for a touch coordinate input device, characterized by: