JPH0473303B2 - - Google Patents

Description

Detailed description of the invention [Technical field to which the invention pertains] The present invention is directed to a three-component force detection pressure-sensitive module that detects force such as a load applied to a pressure-receiving surface by decomposing it into three component forces in three mutually orthogonal directions. The present invention relates to a pressure sensor suitable for constructing one distributed load cell unit or the like by arranging a large number of pressure sensitive modules in an array.

[Prior art and its problems] The pressure-sensitive module is capable of decomposing forces such as the loads mentioned above into a basic orthogonal coordinate system and detecting them separately as components of force in three directions. By synthesizing it using an arithmetic expression, it is possible to determine the magnitude and direction of the force, and furthermore, it is possible to determine the force in any direction, so it is of course useful as a single load meter, etc. In particular, pressure sensors arranged in an array have relatively new uses because they can determine the distribution of force, the center of force (center of gravity), and the resultant force acting on it.

An example of this can be seen in the human body dynamics experiment shown in FIG. The figure shows the foot 2 of a person walking on the pressure sensor 1, and in the state on the right side of the figure, the heel of the foot is in contact with the load cell 1, which is indicated by the tip of the bag-shaped arrow. In the state on the left side of the figure, the toe is in contact with the pressure sensor 1. As the walking dynamics progress, the distribution of the load applied to the pressure sensor and the three component forces Fx, Fy, and Fz of the load naturally change over time. Measuring the load during walking dynamics using an ordinary weight scale does not provide very useful information, even if it is possible to measure the temporal changes in the overall load. However, if it is possible to accurately measure the planar distribution of load and the transition of component forces during walking dynamics, it is known that very useful knowledge can be obtained regarding individual differences in walking dynamics and patterns of physical disorders. It is being Furthermore, by attaching this pressure sensor 1 to the back of the robot's foot, it becomes possible to provide the robot with a sophisticated walking control function.

The need to detect the distribution of such load components exists widely in the industrial field, and an example of a pressure sensor for a robot is shown in FIG. In the figure, one of the robot hands 4 attached to the tip of the multi-joint arm 3 is shown.
A state in which an object 6 is gripped by a pair of fingers 5, 5 is shown. If the object 6 has sufficient hardness and strength, such as many industrial parts, there will be no problem, but if the object 6 is soft or perishable, such as fruit, it may be difficult to use strong force. Gripping is not allowed. In order to handle this type of object with a robot without damaging it, the gripping force, that is, the component force of the load applied to the fingers 5 and its distribution, must be measured fairly accurately, and the gripping force must be measured with a moderate amount of force that will not damage the object or cause it to fall. must be grasped.

Also, in order to know whether the grip is being performed correctly, it is useful to know the planar distribution of the load component force. For example, when gripping a relatively elongated object 6 as shown in the figure, the distribution of the load component force differs depending on the part of the object to be gripped, so if the distribution is abnormal, the gripping may be performed inappropriately. I know that there is. Furthermore, when a soft object is being gripped with a relatively small gripping force, the risk of the object falling off can be predicted from the time course of the load component force.

FIG. 3 shows an outline of the configuration of such a pressure sensor. In the illustrated pressure sensor 1, a large number of pressure sensitive modules 10 are arranged in a plane array in both the x and y directions on a common substrate 30, and each pressure sensitive module 10
The pressure-sensitive cells 20 receive loads having component forces Fx, Fy, and Fz through the pressure-receiving plates 40, respectively, and the pressure-sensitive cells 20 detect not only the vertical force Fz that the pressure-receiving plates 40 receive, but also the lateral forces Fx and Fy. do. For example, as illustrated in Fig. 1, in addition to the distribution of the human body's weight applied to the pressure sensor 1, it is possible to determine the magnitude and distribution of the force Fx that kicks backwards and the force Fy that pushes out in a lateral direction with respect to the walking direction. can be known. Each pressure sensitive module 1
0 indicates a cell 20 as a pressure sensitive structure, a substrate 30, and a pressure receiving plate 4 as shown surrounded by a dashed line in the figure.
It consists of 0.

However, such a conventional pressure-sensitive module 1
0, as shown in FIG.
Since each cell 20 receives a load through an independent upper pressure receiving plate 40 for each cell 20, the unbalanced load Fz deviates from the mounting position of the cell 20 as shown in FIG.
is applied to the pressure receiving plate 40, it is applied to the pressure receiving plate 40.
Even if the load is perpendicular to zero, a bending moment M is generated on the cell 20 as shown in Figure 6, and the strain gauge for detecting the load in the y direction generates a bending moment M.
The drawback was that a false detection output equivalent to Fy was produced. Furthermore, because of the single cell structure, it was mechanically weak and could not withstand relatively large forces.

[Object of the Invention] An object of the present invention is to provide a pressure sensor that eliminates the generation of moments that cause detection errors as described above, and further has a stronger structure of the pressure-sensitive module.

[Summary of the Invention] The present invention eliminates the generation of moments and further strengthens the structure by integrally constructing a pressure-sensitive module with two three-direction force detection cells.

[Embodiments of the Invention] The present invention will be described in detail below with reference to the drawings.

FIG. 7 shows an embodiment of the present invention, in which two ring-shaped cells 20, 20 are placed between a lower substrate 30 and an upper pressure receiving plate 40 so that their end surfaces 20a are parallel to each other. and each cell 20
The protrusion 20b at the lower end of the figure is fitted into the groove 31 of the substrate 30 and fixed to the substrate 30 by adhesive or other means. The upper end of the cell 20 is also fixed to the pressure receiving plate 40 in the same manner.

In this way, the two cells 20, 20 are connected to the substrate 30.
and fix it vertically on the top of the cell 2.
By placing and fixing the pressure receiving plate 40 on a set of 0 and 20, one pressure sensitive module 5 is formed.
0, even if an unbalanced load in the z direction (vertical direction) as shown in FIG. 5 is applied to the pressure receiving plate 40, almost no bending moment as shown in FIG. Directional load detection sensor 22
No error output is generated from yt, 22yc.
In addition, since the two vertical cells 20, 20 whose ends are fixed to the substrate 30 and the pressure receiving plate 40 receive the load, the pressure sensitive module 50 becomes a single mechanically strong structure, which improves reliability. Improvements can also be obtained.

In this example, each cell 20 is made of single crystal silicon, and a plurality of strain gauges 22xt, 22xc, 22yt,
22yc, 22zt, and 22zc are formed in an arrangement as shown in FIG. 8 by a known diffusion technique. In order to avoid interference between component forces, the angle α is preferably chosen to be α=39.6°, which satisfies the equation sinα=2/π. These eight strain gauges for measuring Fx, Fy, and Fz component forces are each connected to two bridge circuits connected in series as shown in Fig. 9A to C, so that they can be used to measure regular force. The strain detection signals A, B, and C are added to each other, and the error signals α, β, and γ caused by interference between the force components cancel each other out. As a result, the output signals Ez, Ex, and Ey from each of the circuits shown in FIGS. 9A to 9C become detection signals representing the component forces Fz, Fx, and Fy independently of each other, with error signals due to interference cancelled. Furthermore, since a pressure sensor is formed by arranging a plurality of pressure-sensitive modules 50 configured in this way in an array as shown in FIG. 10, measurement errors and interference between component forces are minimized. Highly accurate distributed load detection can be obtained.

[Effects of the Invention] According to the present invention, one pressure-sensitive module is constituted by a set of two three-direction force detection cells mounted on a substrate, and the pressure-sensitive modules are arranged in an array to detect pressure. Since the sensor is formed in such a way that even when an unbalanced load in the vertical direction (z direction) is applied to the pressure receiving surface of each cell, an error output does not occur from the horizontal direction (y direction) load detection sensor and the output is high. Accurate distributed load detection can be obtained. In addition, since the load is applied to a set of two cells, the pressure-sensitive module becomes stronger and its reliability is improved.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an example in which the pressure sensor to which the present invention is applied is used to measure the walking dynamics of a human body, and Fig. 2 is an explanatory diagram showing an example in which the pressure sensor is used as a sensor for controlling a robot hand. , Fig. 3 is a perspective view showing an example of the basic configuration of a pressure sensor that integrates a conventional pressure-sensitive module, Fig. 4 is a perspective view showing the conventional pressure-sensitive module, and Figs. FIG. 7 is a schematic diagram showing a pattern of deformation in response to a load in a pressure-sensitive module. FIG. 7 is a perspective view showing a configuration example of a pressure-sensitive module forming a pressure-sensitive sensor of the present invention. FIG. 8 is a cell of the pressure-sensitive module shown in FIG. 7. 9A to 9C are circuit diagrams showing the connection mode of the strain gauges in FIG. 8, and FIG. 10 is a perspective view showing a configuration example of the pressure sensor of the present invention. . DESCRIPTION OF SYMBOLS 1... Pressure sensor, 10, 50... Pressure sensitive module, 20... Ring-shaped cell, 30... Substrate, 40... Pressure receiving plate.

Claims (1)

[Scope of Claims] 1. A cell that detects the force applied to the pressure-receiving surface of the silicon by decomposing it into three components based on a change in the resistance value of a diffusion-type strain gauge formed on the surface of single-crystal silicon. A two-cell pressure sensor comprising a pressure module and having a plurality of pressure-sensitive modules arranged in an array, wherein each of the pressure-sensitive modules includes two cells. 2. In the pressure sensor according to claim 1, the pressure-sensitive module includes two cells between a pressure-receiving plate and a substrate that are arranged parallel to each other, and the end surfaces of the cells are parallel to each other. A two-cell pressure sensor, characterized in that the end faces are fixed so as to be orthogonal to both the plates. 3. A pressure sensing module configured with a cell that detects the force applied to the pressure-receiving surface of the silicon by decomposing it into three components based on changes in the resistance value of a diffusion type strain gauge formed on the surface of single-crystal silicon. A two-cell pressure sensor, wherein each of the pressure-sensitive modules includes two cells.