JPS61223626A - Sensor - Google Patents

Abstract

PURPOSE:To make a sensor small in size simple, and high-precise by the integrated circuit technique and joining a semiconductor gauge resistance with a beam into one body to improve the reliability for a long time by separating a force and a moment from the sensor using a semiconductor, and detecting them simultaneously. CONSTITUTION:Center and outside peripheral supporting bodies 1 and 2 and beams 3 and 4 connecting them are constituted into one body with common semiconductor materials, and semiconductor gauge resistances 11 and 12 and semiconductor gauge resistances 13 and 14 are buried on sides of supporting bodies 2 and 1 of the beam 3 respectively. Semiconductor gauge resistances 15 and 16 are buried on sides of supporting bodies 2 and 1 of the beam 4, and resistances 11, 13, 15, and 16 constitute the first full-bridge circuit, and connection nodes of resistances 15 and 16 and resistances 11 and 13 are connected to output terminals 64 and 65. Resistances 14, 12, 15, and 16 constitute the second full-bridge circuit, and the connection node of resistances 14 and 12 is connected to an output terminal 66. In such a constitution, the first bridge is out of balance to generate an output between terminals 64 and 65 when the moment is applied, and the second bridge goes to out-of-balance to generate an output between terminals 64 and 65 when the force is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sensor for detecting force and moment used in a robot arm or the like.

(Prior Art and its Problems) Conventionally, in the field of robot applications, there has been a strong desire to detect the gripping force when a gripper or finger grips an object, that is, the reaction force from the object. If such a gripping force is detected, by controlling the opening/closing amount of the gripper according to the gripping force, even if the object is soft or brittle, it can be gripped without breaking and the desired movement can be achieved. This is because it is possible to achieve Various sensors have been proposed to meet such demands. FIG. 9 shows a sensor used at the US Jet Propulsion Laboratory (Automation Technology, Vol. 13, No. 1, pp. 49-52). In the figure (a), 101 is a central support, 102 is an outer peripheral support, and 103 to 106 are beams. Typically, the central support 101 is rigidly fixed to a first receiving rod (not shown) through a hole provided in its center. Further, the peripheral support 102 is firmly fixed to a second receiving rod (not shown) using its peripheral portion. Furthermore, a plurality of strain gauges (illustrated as 107) are bonded to the surfaces of the plurality of beams, so that deformation (i.e., strain) of each beam can be detected. The first receiving rod is located on the body side of the robot arm, and the first receiving rod is located on the object side of the robot arm, for example. In such a configuration, when a gripper or finger grasps an object and lifts it into the air, forces and moments are induced between the first and second receiving rods. It is known that such force and moment are determined depending on the load of the target object, the position of the center of gravity of the shape, and the posture of the arm. Such forces and moments are expressed in the same figure (b) with respect to the
), namely, Fx (force in the X-axis direction), F
It can be defined by a combination of Y (force in the Y-axis direction), Fz (force in the Z-axis direction IMx (moment about the X-axis) 1My (moment about the Y-axis), and Mz (moment about the z-axis). In addition, when these six components are induced, the four beams have W2N as shown in Figure (b).
The eight transformations shown in the town occur. This deformation is detected individually by strain gauges glued to each beam, as described above.

In other words, eight deformations can be determined from the output signal of the strain gauge, and further, the six components can be determined using the matrix shown in the following equation.

Here, %k17111 is a conversion coefficient mainly determined by the stiffness of the beam, and by changing the stiffness, the detection sensitivity of the six components can be changed. Material for how stiffness changes.

This is achieved by appropriately determining the cross-sectional shape, thickness, length, etc. The calculation of the matrix shown in the above equation is normally performed by a microprocessor or the like stored in the robot controller. Of course, minute changes in resistance that occur in strain gauges can be handled by resistance/voltage conversion circuits, voltage amplification circuits,
Needless to say, the data must be converted into a digital quantity using a characteristic compensation circuit, an A/D converter, etc., and then supplied to the microprocessor. The conventional sensor illustrated in FIG. 9 has the following problems.

(1) The central support, peripheral support, and multiple beams are
It is usually formed by cutting from a metal block.

For this reason, the processing time for creating the structure is long, and the cutting accuracy (particularly the shape and dimensions of the beam) affects the accuracy of the detection sensitivity of the six components. In other words, it is difficult to inexpensively mass-produce the structure with high precision and little variation in detection sensitivity (2) When creating the central support, the peripheral support, and multiple beams by cutting, It is difficult to downsize the body. Furthermore, since the machining accuracy in cutting is approximately 10 μm, as the size of the beam decreases, the relative accuracy of the beam (here, the ratio of the machining accuracy to the beam cross-sectional dimension is considered as an example) deteriorates, and as described in the previous section (1). ) The variation in the detection accuracy becomes large.

(3) When bonding strain gauges, a creep phenomenon occurs due to the adhesive, making it difficult to maintain long-term stability of the sensor. In the field of robots, which is the subject of the present invention, it is assumed that the period during which a gripper or finger grips a target object is quite long. It depends on the content of the work, but
It may last several tens of minutes. If the creep phenomenon occurs when a certain target object gripping state and arm posture are achieved within such a long period of time, the output from the sensor changes, so the robot controller Since the state and the posture of the arm appear to be changing, undesired malfunctions of the robot occur.

(4) The strain gauge is usually detected as a voltage signal by a bridge circuit, but this voltage signal value is on the order of milliports, and its output impedance is as high as several hundreds of ohms. Expensive DC amplifiers called signal conditioners are required to amplify such low voltage signals to the desired level. Furthermore, a signal transmission line and a nuclear disturbance noise removal circuit are necessary to efficiently transmit the low-level signal with high output impedance without being mixed with disturbance noise, which leads to an increase in the cost of peripheral circuits. , the widespread use of such sensors has been hindered.

(5) When the matrix calculation is performed using software inside the controller, the time required for the calculation is long, making it difficult to operate the robot at high speed. Furthermore, in order to perform the calculation, other calculations for controlling the robot are sacrificed, making it difficult to improve the sophistication of the control.

As mentioned above, conventional sensors are smaller, cheaper,
There were limitations in terms of reducing variation in detection sensitivity, long-term stability, etc., and it was not a satisfactory sensor for robot control.

(Object of the Invention) An object of the present invention is to provide a sensor that eliminates the drawbacks of the prior art, is suitable for robot control, and can expand the field of application.

(Structure of the Invention) According to the present invention, the central support body, the peripheral support body, and the plurality of beams connecting them are integrally constituted by a common semiconductor material, and the first beam constituting the plurality of beams on the outer peripheral support side. A second semiconductor gauge resistor is located on the side of the central support, and a third. Fourth semiconductor gauge resistors are buried respectively, a fifth semiconductor gauge resistor is buried on the outer peripheral support side of the second beam, and a sixth semiconductor gauge resistor is buried on the central support side of the second beam, which are located opposite to the first beam. It is buried, and the first. Third. Fifth. A first full-bridge circuit is configured by the sixth semiconductor gauge resistor group, and the first. The connection node of the fifth resistor is connected to the terminal having the first polarity of the excitation power source, and
．． The connection nodes of the sixth resistor have means respectively connected to terminals of the second polarity of the power supply; The connection node of the sixth resistor is connected to the first output terminal, and the connection node of the sixth resistor is connected to the first output terminal. The connection node of the third resistor has means connected to the second output terminal; Second. Fifth. A second full-bridge circuit is configured by the sixth semiconductor gauge resistor group, and the fourth. A sensor is obtained, characterized in that the connection node of the second resistor has means for being connected to the third output terminal.

(Example) The present invention will be explained in detail below with reference to Examples.

FIG. 1 is a diagram showing an embodiment of the present invention. Same figure (,)
is a plan view of the semiconductor substrate No. composing the sensor, and FIGS.
, is a cross-sectional view taken along line B-B. In the same figure.

The material of the substrate 10 is, for example, single crystal silicon.

1 is the central support, 2 is the outer peripheral support, and 3 and 4 are the supports 1
and 2. This is the second beam.

2, 1 to 4 are integrally constructed of the same semiconductor material. The same figure (Hata) shows four beams,
The number is not limited to four, but may be two or more. However, as will become clear in the discussion below, the four beam case is most preferred. First and second semiconductor gauge resistors (each 11.12) are embedded in the outer peripheral support side of the beam 3, and third and fourth semiconductor gauge resistors (each 13.14) are embedded in the central support side. There is. A fifth semiconductor gauge resistor 15 is disposed on the outer circumferential support side of the second beam 4 located opposite the first beam 3, and a sixth semiconductor gauge resistor 1 is disposed on the central support side.
6 are buried in each. The semiconductor gauge resistor group is formed using well-known semiconductor technology; for example, if the substrate 10 is n-type, the resistor group is p-type. The semiconductor substrate indicated by 10 is produced by the manufacturing method illustrated below.

(1) The semiconductor gauge resistor group is formed at a desired position by thermal diffusion and ion implantation techniques. Since the resistor is not glued, there is no creep phenomenon caused by adhesives, and it is stable over a long period of time.

(2) Patterning is performed along the inner and outer peripheries of the outer peripheral support 2, the outer periphery of the central support 1, and the outer edges of the beams 3, 4, etc., and unnecessary portions of the semiconductor substrate are removed. This removal method includes well-known methods such as isotropic etching using a mixed solution of nitric acid and hydrofluoric acid, anisotropic etching using an alkaline solution, and the like. Note that the buried position of the resistor within the beam has a negative effect on characteristics such as sensitivity and offset of the sensor, so it is necessary to ensure sufficient positional accuracy and bury the resistor at a desired position. In addition, in order to ensure positional accuracy, the process of Tl)f21 above may be reversed. The operation of the embodiment shown in FIG. 1 produced by such a manufacturing method will be described next. FIG. 2 is an example of a structural cross-sectional view when the semiconductor substrate shown in FIG. 1 is configured as a sensor for detecting force and moment. In the figure, 2
0 is a first receiving rod coupled to the central support, and a cylindrical rod is illustrated. Reference numeral 21 denotes a second receiving rod coupled to the outer peripheral support, and both 20 and 21 are cylindrical rods. Further, in the figure, a semiconductor substrate 10
The cross section of B in Figure 1 (,) is similar to Figure 1 (c).
A cross-sectional view at -B' is shown. There are no restrictions on the means for connecting the receiving rod 20 and the support 1. For example, bonding with adhesive, bonding with eutectic alloy, screw connection with a hole (not shown) provided in the center of 1 and a female thread (not shown) provided in the center of 20, etc. It's fine. Furthermore, there is no restriction on the means for connecting the receiving rod 21 and the support body 2. For example, the bonding may be performed using an adhesive, a eutectic alloy, or the like. Of course, as mentioned above, these bonds are required to have a large bonding force and to have a small effect of thermal distortion due to fluctuations in operating temperature. Although the receiving rods 20 and 21 are illustrated as having a cylindrical shape, they may have other shapes, such as a square prism or a combination of a rectangular prism and a cylinder. Regarding the selection of such a shape, it is sufficient that one end of each can be easily coupled to the semiconductor substrate 10, and the vicinity of the other end can be easily coupled to another mechanical element, such as a gripper or finger of a robot arm, or the arm body. Of course, it is necessary that the material of the receiving sides 20 and 21 has high mechanical strength and high mechanical rigidity due to the material and shape.

FIG. 3 is a cross-sectional view of the sensor structure similar to FIG. 2, showing the case where a moment is applied to one of the receiving rods. In the figure, the cross section of the semiconductor substrate rice grain is shown in Figure 2 (b
), it is illustrated as a cross-sectional view at A-, < in FIG. 2(,). Also, similar to Fig. 2, the receiving rod 20.21
are both shown as cylindrical shapes. In the figure, one receiving rod 21 is mechanically fixed, and the other receiving rod 20 is
The deformation when a moment 30 in the plane of the paper is applied is conceptually shown. This modification is shown in more detail in FIG. If the amount of deformation caused by the moment 30 is minute and both beams 3 and 4 behave in accordance with the thin plate theory, the deformations in beams 3 and 4 will be the same as shown in the figure. Of course, under such an assumption, the central support would be oblique, which would seem to contradict the shape shown in the figure.

However, such a situation occurs only because the vertical direction of FIG. 4 is exaggerated.

Due to the presence of the moment 30, "bending" occurs in the beams 3 and 4, and in response to this "bending", the beams 3 and 4
tensile and compressive stresses are induced in the In FIG. 4, resistor 12.16 has a tensile force and resistor 14.
A compressive force is acting on 15. Under such stress, due to the well-known piezoresistive effect, the resistors #12, 14, 15
．． The resistance value of 16 changes. That is, the moment applied between the five receiving rods 20 and 21 can be detected as an electrical signal (ie, a change in resistance value).

FIG. 5 conceptually shows the deformation when a force indicated at 4° is applied to the same sensor as in FIG. 3. By applying such a force 40, a symmetrical "bend" is generated in the beams 3 and 4. The shape of the “bend” connects the free end of the cantilever to a fixed boundary (built
It becomes the same shape as when moved under conditions (referred to as blult-in edge). Tensile or compressive stress is induced in the beam in response to the "bending" deformation. In the figure, resistance 1
A compressive force acts on resistance 1.15, and a tensile force acts on resistance 13.16. Under such stress, the resistance values of the resistors $11.13 and 16.15 change due to the well-known piezoresistive effect. That is, the compressive force and tensile force applied between the receiving plates 20 and 21 (the situation is opposite to that in FIG. 5) can be detected as an electrical signal (ie, a change in resistance value).

FIG. 6 is a diagram illustrating the circuit configuration of the semiconductor gauge resistor group explained using FIG. It is represented by a number. Furthermore, the same figure also shows changes in resistance values of each gauge resistor. That is, when the moment shown in Fig. 3 is applied, the same figure (,) also shows that the same figure (b)
) is shown by an upward arrow if the resistance value increases due to the vinyl/resistance effect, and a downward arrow if it decreases when the force shown in Figure 5 is applied. There is. However, in FIGS. 3 and 5, it is assumed that the resistance value decreases when compressive stress is applied, and the resistance value increases when tensile stress acts. Although this assumption does not hold in all cases, silicon (
110) direction is true, and is also assumed for convenience in this description.

In Figure 6, happiness 1. Third. Fifth. The sixth semiconductor gauge resistance group 11, 13, 15, 16 constitutes a first full bridge circuit with wiring formed on a semiconductor substrate by phosphorography technology. The fifth resistive connection node is the excitation voltage source 60. Alternatively, the third . The sixth resistor connection node is connected to the excitation voltage J160 or to the terminal 63 of the excitation current source 61 having the second polarity, respectively.

Similarly, the fifth. The sixth resistor connection node is connected to the first output terminal 64 and the first . The third resistive connection node has means for being connected to the second output terminal 65. Similarly, the fourth. Second. Fifth. @6 semiconductor gauge resistance group 14,
12, 15, and 16 have means for configuring a second full bridge circuit; The fourth resistive connection node has means connected to the third output terminal 66. The full bridge circuit used in the above description is a 4-arm active circuit.
It is also known as a bridge circuit, and it is well known that it has the function of stably converting minute changes in resistance value into voltage output. From the explanation of this circuit configuration, Section 4. A fifth resistor connection node is connected to terminal 62 and the second . It is obvious that the sixth resistance connection node is connected to the terminal 63. Same figure (,
), when the moment acts, the first full-bridge circuit is unbalanced and a voltage signal is output between terminals 64 and 65. On the other hand, since the second full bridge circuit does not lose its balance, no voltage signal is output between the terminals 64 and 66. Furthermore, in FIG. 2B, when the force is applied, the balance of the first full-bridge circuit is lost and no voltage signal is output between the terminals 64 and 65. On the other hand, in the second full bridge circuit, the balance is lost, so a voltage signal is output between terminals 64 and 66. By the way, in Fig. 6, the six semiconductor gauge resistors are
The resistance values when no force or moment are applied are all equal, and the amount of change in resistance value of the resistors due to the piezoresistance effect is all the same. Such conditions are such that the shape and impurity concentration conditions of the resistor group shown in FIG. easily achieved. Of course, if such conditions are not completely satisfied due to various error factors in the manufacturing process, a plurality of correction resistors may be connected in parallel and series to any of the gauge resistors or to each of a plurality of gauge resistor groups. It is possible to substantially satisfy this condition by inserting two.

Such adjustment methods are well known to those skilled in the art and are not essential to the present invention, so they will not be described in detail. According to the above operation, a signal corresponding only to the moment is transmitted between the output terminals 64 and 65, and
．． 66, it is clear that a signal corresponding only to force is obtained. That is, according to this embodiment of the present invention, the drawback of separating moment and force by matrix calculation in the prior art is completely eliminated.

In addition, in the plan view shown in Figure 1 (,), starting a business in the horizontal direction,
By embedding a semiconductor gauge resistor in the opposing beam and configuring a circuit similar to the circuit shown in Figure 6, it will be possible to detect moments acting in a direction perpendicular to the moment 30 shown in Figure 3. Become. As a result, moment 3
It is clear that moments other than the moments orthogonal to 0 and 30 can also be detected separately as respective moment components.

In the configuration of FIG. 6, the first. A second full bridge circuit shares the common resistor 15,16.

This configuration was adopted to simplify the circuit. Of course, the first. The second full bridge circuit may be separated. Such a configuration is illustrated in FIG. 7, and the newly required 5. The seventh resistor corresponds to the sixth semiconductor gauge resistor. The eighth gauge resistor 17.18 is shown in FIG.
), the resistor group 17.18 adjacent to 15.16 may be used in the beam 4 region. In such a case, the voltage signal is output separately between the output terminals 64' and 65 and between the output terminals 64'' and 66.

In the configuration of FIG. 6, a single power supply indicated at 60 is illustrated as the excitation voltage source. The present invention is not limited to this, and a power source that generates positive and negative voltages having the same absolute value may be used. In such a case, since the potential of the output terminal 64 in FIG. 6 is approximately the ground potential, there are many advantages in forming wiring from the output terminal.

The gauge resistor used in the present invention uses the piezoresistance effect of semiconductors, so compared to conventional metal foil gauge resistors,
The resistance value changes by about 2 for the same stress (or the same strain)
It has the advantage of being an order of magnitude larger.

Therefore, when a full bridge circuit is configured, the output voltage reaches approximately 100 mV or more, and even if the output voltage is wired using a cable, there is an advantage that the influence of disturbance noise can be relatively reduced. However, there is a drawback that the sensitivity changes greatly depending on the operating temperature, that is, the temperature characteristics are poor. Since the sensor uses a semiconductor substrate, there is a new advantage in that the sensor can be integrated with a well-known semiconductor integrated circuit. For example, in FIG. 1, the central support 1 and the peripheral support 2 are exposed to stresses induced from forces and moments applied between said receptors 20, 21, as will be apparent from the detailed description of the invention. Since there are almost no components, even if a signal processing circuit is integrated in such a support region, it has nothing to do with the stress. Such signal processing circuits include amplifier circuits, temperature compensation circuits, various arithmetic circuits, output circuits, etc., all of which can be realized by making full use of known circuit technology. Of course, the signal processing circuitry should be appropriately designed so that the stress does not change the circuit operation. For example, if the circuit operation is determined only by the size ratio of the transistors, it becomes possible to integrate a signal processing circuit in the beam region.

Although FIG. 1 shows a case where the central support and the peripheral support are circular, this is not the case. That is, since all of the supports need only have the function of fixing both ends of the beam, they may have a square shape instead of a circular shape. Such a choice is not the essence of the invention, but rather should be made taking into account ease of binding to receptors and ease of implementation in robotic components.

Further, the arrangement of the semiconductor gauge resistors embedded in the beam can be arbitrarily selected regardless of the present invention. Of course, it is a good idea to increase the conversion coefficient when converting the induced stress into a resistance value change, and to adopt an arrangement in which the coefficient is constant (that is, the stress/resistance value change is linear). Yes.

FIG. 8 is a diagram showing another embodiment of the present invention.

In the figure, the same numbers as in FIG. 1 indicate the same components. Further, the gauge resistor group is omitted. Same figure (
a) and (bHc) are a plan view, a sectional view at the h-1 section, and a sectional view at the B-B' section, respectively, of the semiconductor substrate (2) in this embodiment. The first difference from the above embodiment is as shown in the same figure (
As shown in b), using well-known techniques such as etching,
The thickness of the beams 3, 4, etc. is made thinner than the thickness of the supports 1 and 2, and the width of the beams 3, 4, etc. is made small, as shown in the figure (,). This shape was selected so that even if the force and moment applied to the receptor (not shown) are minute, the resistance value change will be large. That is, selection of such a shape is effective in increasing the sensitivity of the sensor. The second difference between this embodiment and the above embodiments is that a first buffer layer 50 is provided on the surface of the central support to improve thermal stability, and a first buffer layer 50 is provided on the back surface of the peripheral support. The second buffer layer 51 is provided to improve physical stability. Since the coefficient of thermal expansion of a semiconductor material such as silicon is usually small, thermal strain caused by the difference in coefficient of thermal expansion between the material and the receptor causes characteristic deterioration. In particular, when the receptor is made of metal, such deterioration of characteristics becomes a particularly significant problem. 1st. The second buffer layer is adopted to reduce the difference in thermal expansion coefficient, and is made of a material having an intermediate value of thermal expansion coefficient between the semiconductor substrate and the receptor, or a material of the semiconductor substrate. A material having a value approximately equal to the coefficient of thermal expansion is preferable.

More specifically, borosilicate glass such as Pyrex is preferred, but is not limited thereto. When the buffer layers 50, 51 are made of Pyrex or the like, anodic bonding techniques can be used for adhesion to the semiconductor substrate 10. In this embodiment, it goes without saying that the bonding with the receptor (not shown) is not made directly with the semiconductor substrate 10, but through the buffer layer. It is possible to use anodic bonding for such bonding. Further, the positional relationship between the buffer layers 50 and 51 with respect to the substrate 10 is not limited to the illustrated side. That is, on the back side of the central support 1, 51 is attached to the outer peripheral support 2.
It may be provided on the surface of.

Above, a detailed explanation has been given with reference to examples of a novel sensor capable of detecting force and moment. According to such an invention, the sensor can be manufactured using semiconductor integrated circuit technology, so it can be miniaturized and Lower costs and higher precision can be easily achieved. Furthermore, since the semiconductor gauge resistor is integrated with the beam without using an adhesive, no creep phenomenon occurs and excellent long-term reliability can be ensured. Furthermore, output signals corresponding to force and moment can be separated and obtained individually from the sensor without performing complex matrix calculations within the robot controller. The sensor according to the present invention significantly contributes to the advancement of robotics, and its effects are significant.

(Effect of the invention) According to such an invention, it becomes possible to separate and simultaneously detect sensor placement and moment using semiconductors, so it is applicable not only to the above-mentioned robot application fields but also to many other applications. Application to the mechanical engineering field becomes possible. for example,
The present invention can also be used in touch sensors for three-dimensional measuring machines.
The effect is significant.

[Brief explanation of the drawing]

1 to 8 are diagrams showing embodiments of the present invention. FIG. 9 is a diagram showing a conventional example of a sensor for detecting force and moment. 105, 106... Beam 11.12, 13, 14, 15, 16, 17.18...
・Semiconductor gauge resistance 20.21...Receptor 30・
...Moment 40...Force 50,51.
...Buffer layer 62, 63, 64, 64', 6e, 65, 6
6...Terminal 60.61...Excitation power supply boar 1 Figure A (a) (b) Invitation 2 Figure 4 Figure 5'FaQ sword Figure 6 (α) (b) Figure 7 Ari 6 Figure

Claims (1)

[Claims] The central support body, the peripheral support body, and a plurality of beams connecting them are integrally constructed of a common semiconductor material, and a first beam constituting the plurality of beams has a first beam on the side of the peripheral support body.
A second semiconductor gauge resistor has third and fourth resistors on the central support side.
A fifth semiconductor gauge resistor is embedded in the outer peripheral support side of the second beam located opposite the first beam, and a sixth semiconductor gauge resistor is embedded in the central support side of the second beam. The first, third,
A first full-bridge circuit is configured by the fifth and sixth semiconductor gauge resistor groups, and the connection node of the first and fifth resistors is connected to the terminal having the first polarity of the excitation power supply, and the third and sixth The connection nodes of the resistors have means respectively connected to terminals having a second polarity of the power supply, and the connection nodes of the fifth and sixth resistors have means connected to the first output terminal and the first and third The connection node of the resistor is the second
means connected to the output terminals of the fourth, second, and fifth output terminals;
, wherein the sixth semiconductor gauge resistor group constitutes a second full bridge circuit, and a connection node between the fourth and second resistors has means for connecting to a third output terminal.