JPH0575055B2 - - Google Patents

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 can be achieved. Various sensors have been proposed to meet such demands. The 9th sensor used at the Jet Propulsion Laboratory in the United States
As shown in the figure (Automation Technology, Volume 13, No. 1, No. 49-
page 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 connected to a first receiving rod (not shown) through a hole provided in its central portion.
is firmly fixed. In addition, the outer peripheral support 10
2 is firmly fixed by its periphery to a second receiving rod (not shown). Further, a plurality of strain gauges (illustrated as 107) are bonded to the surfaces of the plurality of beams, so that deformation (that is, strain) of each beam can be detected. The second receiving rod is located, for example, on the main body side of the robot arm, and the first receiving rod is located, for example, on the object side of the robot arm. In such a configuration, when the grippers or fingers grasp and lift an object 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, shape, center of gravity position, and posture of the arm of the target object. These forces and moments are about the X, Y, and Z axes shown in Figure a.
The six components shown in figure b are F _X (force in the X-axis direction), F _Y (force in the Y-axis direction), F _Z (force in the Z-axis direction),
M _X (moment around the X axis), M _Y (moment around the Y axis), M _Z (moment around the Z axis)
It is possible to define a combination of Also,
When these six components are induced, eight deformations shown as W ₁ to W ₈ in the figure b occur in the four beams. This deformation is detected individually by strain gauges bonded to each beam, as described above. In other words, from the strain gauge output signal,
Eight deformations are obtained, and furthermore, the above six components can be obtained using a matrix shown in the following equation. _{F X F Y F Z M _ _ _ _ _ _ _ _ 65} O O k ₃₆ O k ₅₆ Ok ₁₇ O O O O O k ₆₇ O O k _{38 k 48 O} OW ₁ W ₂ W ₃ W ₄ W ₅ W ₆ W ₇ W _8Here , k _no is mainly due to the stiffness of the beam. This is a determined conversion coefficient, and by changing the rigidity, the detection sensitivity of the six components can be changed. The method of changing the rigidity is achieved by appropriately determining the material, 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
Needless to say, the signal must be converted into a digital quantity using a resistance/voltage conversion circuit, voltage amplification circuit, characteristic compensation circuit, A/D converter, etc. before being 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. That is, 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 miniaturize the structure. Furthermore, the machining accuracy in cutting is about 10 μm, so as the size becomes smaller,
The relative accuracy of the beam (here, the ratio of the processing accuracy to the beam cross-sectional size is considered as an example) deteriorates, and the variation in the detection accuracy in the previous item (1) increases. (3) When gluing 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 gripper or finger grips a target object for a fairly long period of time. Depending on the content of the work, it can take up to 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 may 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 millivolts, and its output impedance is as high as several hundreds of ohms.
In order to amplify such low voltage signals to a desired level, an expensive DC amplifier called a signal conditioner is required. Furthermore, signal transmission lines and disturbance noise removal circuits for efficiently transmitting the low-level signals with high output impedance without being mixed with disturbance noise are unavoidable, leading to higher prices for 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 robot control are sacrificed, making it difficult to improve the sophistication of the control. As described above, conventional sensors have limitations in terms of miniaturization, cost reduction, reduction of variation in detection sensitivity, long-term stability, etc., and are not satisfactory as sensors for robot control. (Objective of the Invention) An object of the present invention is to eliminate the drawbacks of the prior art, to provide a sensor suitable for robot control and capable of expanding 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 A first and a second semiconductor gauge resistor are embedded in the outer peripheral support, and a third and fourth semiconductor gauge resistor are embedded in the central support, respectively, and the second beam is located at a position opposite to the first beam. A fifth semiconductor gauge resistor is embedded on the outer peripheral support side, and a sixth semiconductor gauge resistor is embedded on the central support side, and the first, third, fifth, and sixth semiconductor gauge resistor groups form a first full bridge circuit. The connection nodes of the first and fifth resistors are connected to the terminals of the excitation power source having the first polarity, and the connection nodes of the third and sixth resistors are connected to the terminals of the power source having the second polarity. The connecting node of the fifth and sixth resistors is connected to the first output terminal, and the connecting node of the first and third resistors is connected to the second output terminal. ,
A second full bridge circuit is configured by the fourth, second, fifth, and sixth semiconductor gauge resistor groups;
A sensor is obtained, characterized in that the connection node of the resistor has means connected to the third output terminal. (Examples) The present invention will be explained in detail below using examples. FIG. 1 is a diagram showing an embodiment of the present invention. Figure a is a plan view of the semiconductor substrate 10 constituting the sensor, and figures b and c are cross-sectional views taken along lines A-A' and B-B' shown in figure a, respectively. In the figure, the material of the substrate 10 is, for example, single crystal silicon. 1 is a central support, 2 is a peripheral support, 3 and 4 are first and second beams connecting the supports 1 and 2, and 1 to 4 of 2 are integrally constructed of the same semiconductor material. has been done. Although four beams are shown in Figure a, the number is not limited to four and 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 with 1
1, 12), and third and fourth semiconductor gauge resistors (13, 14, respectively) on the central support side.
is buried. A fifth semiconductor gauge resistor 15 and a sixth semiconductor gauge resistor 16 are embedded in the outer peripheral support side of the second beam 4 located opposite the first beam 3, and the sixth semiconductor gauge resistor 16 in the central support side. 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 shown in 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 and 4, 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 the sensitivity, offset, and other characteristics of the sensor, so it is necessary to ensure sufficient positional accuracy and to bury the resistor at a desired position. Note that in order to ensure positional accuracy, the steps (1) and (2) 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, 20 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 exemplified as cylindrical rods. Further, in the figure, the cross section of the semiconductor substrate 10 is shown as a cross section taken along line BB' in FIG. 1a, similar to FIG. 1c. 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 okay. Further, 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, these bonds are required to have a large bonding force and to have little 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 pole or a combination of a square pole and a cylinder. Regarding the selection of such a shape, it is sufficient that one end of each can be easily connected to the semiconductor substrate 10 , and the vicinity of the other end can be easily connected to other mechanical elements, such as the gripper or finger of the robot arm, or the arm body. Of course, it is necessary that the material of the receptacles 20, 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, a semiconductor substrate 1
The cross section of 0 is the same as that of FIG. 2b, and is A-
It is illustrated as a cross-sectional view at A'. Further, as in FIG. 2, the receiving rods 20 and 21 are both shown as having a cylindrical shape. In the figure, one receiving rod 21
is mechanically fixed, and the deformation of the other receiving rod 20 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 moment 30, "bending" occurs in beams 3 and 4, and this "bending"
Correspondingly, tensile and compressive stresses are induced in the beams 3, 4. In FIG. 4, the resistor 12,
A tensile force acts on the resistor 16, and a compressive force acts on the resistors 14 and 15. Under such stress, due to the well-known piezoresistive effect, the resistance groups 12, 14, 1
The resistance values of 5 and 16 change. That is, the receiving rod 2
The moment applied between 0 and 21 can be detected as an electrical signal (ie, a change in resistance value). FIG. 5 shows the same sensor as in FIG.
This conceptually shows the deformation when the force shown in is applied. By supplying such force 40, beams 3 and 4 have a symmetrical "bend".
occurs. The shape of the "bend" is equal to the shape when the free end of the cantilever is moved under fixed boundary (referred to as built-in edge) conditions. Tensile or compressive stress is induced in the beam in response to the "bending" deformation. In the figure, resistors 11,1
A compressive force acts on the resistor 5, and a tensile force acts on the resistors 13 and 16. Under such stress, the resistance values of the resistor groups 11, 13, 16, and 15 change due to the well-known piezoresistive effect. That is, the compressive force and tensile force applied between the receiving rods 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 described using FIG. 1a.
In the figure, for convenience, the number of the resistor and the resistor as a circuit element are represented by the same number. Furthermore, the same figure also shows changes in resistance values of each gauge resistor. That is, when a moment as shown in Fig. 3 is applied in Figure a, and a force as shown in Figure 5 is applied in Figure b, the resistance value increases due to the piezoresistive effect. An upward arrow is indicated for the case, and a downward arrow is indicated for the decrease. 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 true in all cases, it holds true for the gauge resistor arranged in the 110 direction of silicon, and is also assumed for convenience in this description. In FIG. 6, first, third, fifth, and sixth semiconductor gauge resistance groups 11, 13, 15, and 16 form a first full bridge circuit using wiring formed on a semiconductor substrate by lithography technology. It consists of
The first and fifth resistance connection nodes are connected to a terminal 62 having a first polarity of an excitation voltage source 60 or an excitation current source 61, while the third and sixth resistance connection nodes are connected to an excitation voltage source 60, Or the second one of the excitation current source 61
The terminals 63 are respectively connected to terminals 63 having polarities of . Similarly, the fifth and sixth resistance connection nodes have means connected to the first output terminal 64, and the first and third resistance connection nodes have means connected to the second output terminal 65. Similarly, the fourth, second, fifth, and sixth semiconductor gauge resistance groups 14, 12, 15, 16
has means for configuring a second full bridge circuit, and the second and fourth resistance connection nodes have means for being connected to the third output terminal 66. The full bridge circuit used in the above description is also called a four-arm active bridge circuit, and it is well known that it has a function of stably converting minute changes in resistance value into voltage output. From the description of this circuit configuration, the fourth and fifth resistance connection nodes are connected to the terminal 62,
Further, it is obvious that the second and sixth resistance connection nodes are connected to the terminal 63. In Figure a, when the moment acts, the balance of the first full bridge circuit is lost, and the terminals 64, 65
A voltage signal is output between them. 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 Figure b, when the force is applied, the balance of the first full bridge circuit does not collapse and the terminal 6
No voltage signal is output between 4 and 65. on the other hand,
Since the second full bridge circuit is unbalanced, a voltage signal is output between the terminals 64 and 66. In FIG. 6, the six semiconductor gauge resistors all have the same resistance value when no force or moment is applied, and the amount of change in resistance value of the resistors due to the piezoresistance effect is all the same. These conditions can be achieved by making the shape of the resistor group and the impurity concentration conditions equal to each other as shown in FIG. easily achieved. Of course, if such conditions are not completely satisfied due to various error factors in the manufacturing process, a correction resistor may be added in parallel and series to one of the gauge resistor groups or to each of the multiple gauge resistor groups. By inserting a plurality of them, it is possible to substantially satisfy this condition. 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. If the above operation is followed, it is clear that a signal corresponding only to the moment can be obtained between the output terminals 64 and 65, and a signal corresponding only to the force can be obtained between the output terminals 64 and 66. 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. Furthermore, if a semiconductor gauge resistor is placed horizontally in the plan view shown in Fig. 1a and embedded in the opposing beam, and a circuit similar to the circuit shown in Fig. 6 is constructed, the circuit shown in Fig. 3 can be constructed. It becomes possible to detect moments acting in a direction perpendicular to the moment 30. As a result, it is clear that moments 30 and moments other than the moment orthogonal to 30 can also be detected separately as their respective moment components. In the configuration of FIG. 6, the first and second full bridge circuits share the common resistors 15 and 16.
This configuration was adopted to simplify the circuit. Of course, the first and second full bridge circuits may be separated. Such a configuration is illustrated in FIG. 7, and the newly required fifth and sixth
The seventh and eighth gauge resistors 17 and 18 corresponding to the semiconductor gauge resistors 17 and 18 are located in the beam 4 region of FIG.
You can use . In such a case, voltage signals are output separately between output terminals 64' and 65 and between output terminals 64'' and 66. In the configuration of FIG. 6, a single power supply indicated by 60 is used as an excitation voltage source. However, the present invention is not limited to this, and a power supply 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. Since the gauge resistor used in the present invention uses the piezoresistance effect of semiconductors, it has many advantages in forming wiring for the same stress (or strain) compared to conventional metal foil gauge resistors. It has the advantage that the change in resistance value is approximately two orders of magnitude larger.As a result, when a full bridge circuit is configured, the output voltage reaches approximately 100mV or more, and even if the output voltage is wired with a cable, the influence of disturbance noise is relatively However, it has the advantage of being able to reduce
Sensitivity changes greatly depending on operating temperature. That is, it has the disadvantage of poor temperature characteristics. 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 have a central support 1 and a peripheral support 2.
Since the stress component induced by the force and moment applied between 0 and 21 is almost non-existent, 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 well-known circuit technology, and of course, by appropriately designing the signal processing circuit. To prevent circuit operation from changing even when stress occurs. 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. In other words, since all of the supports need only have the function of fixing both ends of the beam, it is possible to
You may also use a square shape. Such a selection is not essential to the invention, but rather should be made taking into account ease of binding to receptors and ease of implementation into 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 preferable to adopt an arrangement in which the conversion coefficient when converting the induced stress into a resistance value change is large and the coefficient is constant (that is, the stress/resistance value change is linear). . 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. Figures a, b, and c are a plan view, a cross-sectional view taken along line A-A', and a cross-sectional view taken along line B-B', respectively, of the semiconductor substrate 10 in this embodiment. The first difference from the previous embodiment is that, as shown in FIG. As shown in FIG.
The point is that the width of etc. has been reduced. This shape was selected so that even if the force and moment applied to the receptor (not shown) are minute, the change in resistance value becomes 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. The first and second buffer layers are adopted to reduce the difference in thermal expansion coefficients, and are made of a material having an intermediate value of thermal expansion coefficients between the semiconductor substrate and the receptor, or A material having a coefficient of thermal expansion approximately equal to that of the semiconductor substrate is preferable. More specifically, borosilicate glass such as Pyrex is preferred, but it is not limited thereto. When the buffer layers 50 and 51 are made of pyrex or the like, anodic bonding techniques can be used for adhesion to the semiconductor substrate 10 . In this example,
The bond with the receptor (not shown) is the semiconductor substrate 1.
Needless to say, this is done through the buffer layer without being directly connected to 0. 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, the central support 1
51 may be provided on the surface of the outer peripheral support 2. In the above, a detailed explanation has been given of examples of a novel sensor capable of detecting force and moment. According to such an invention, since the sensor can be manufactured using semiconductor integrated circuit technology, miniaturization 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 has significantly contributed to the advancement of robotics, and its effects are significant. (Effect of the invention) According to such an invention, it becomes possible to separate force and moment and detect them simultaneously using a sensor using a semiconductor, so it is applicable not only to the above-mentioned robot application field but also to many other applications. Application to the mechanical engineering field becomes possible. For example, the present invention can be applied to a touch sensor for a three-dimensional measuring machine, and its effects are 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. 10 ...Semiconductor substrate, 1,101...Central support, 2,102...Outer support, 3,4,10
3,104,105,106...beam, 11,
12, 13, 14, 15, 16, 17, 18...
Semiconductor gauge resistance, 20, 21...Receptor, 30
...Moment, 40...Force, 50,51...Buffer layer, 62,63,64,64'64'',65,6
6...terminal, 60, 61...excitation power supply.

Claims (1)

[Claims] 1 The central support body, the peripheral support body, and a plurality of beams connecting the two are integrally constructed of a common semiconductor material, and a first beam, a second beam, and a second beam are placed on the side of the peripheral support body of the first beam constituting the plurality of beams. A third and a fourth semiconductor gauge resistor are embedded in the central support side, respectively, and a fifth semiconductor gauge resistor is embedded in the outer peripheral support side of the second beam, which is located at a position facing the first beam. A sixth semiconductor gauge resistor is embedded in the central support side, and the first, third, fifth, and sixth semiconductor gauge resistor groups constitute a first full bridge circuit, and the first and fifth semiconductor gauge resistors are A connecting node of the resistor has means for connecting to a terminal having a first polarity of the excitation power source, and a third and a sixth connecting node of the resistor have means respectively connected to a terminal having a second polarity of the power source; 5. The connection node of the sixth resistor is the first
The connection nodes of the first and third resistors have means connected to the second output terminal, and the fourth, second, fifth and sixth groups of semiconductor gauge resistors are connected to the second output terminal. A sensor comprising a full bridge circuit, and a connection node between the fourth and second resistors having means connected to a third output terminal.