JP2010112864A - Force sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multiaxial force sensor compactly manufactured at low cost, and sensing a plurality of translation forces in the axial direction and a plurality of moments around axes. <P>SOLUTION: It is possible to reduce a distance for distorting a strain element for the reason that a conductivity sensing rubber or an electrostatic capacitance is used for detecting the moments (M<SB>x</SB>, M<SB>y</SB>) around two axes, thereby a sensor diameter can be reduced. Also, a structure is simplified, so that a height can be ≤10 mm, thereby eliminating the need for performing a complicated interference removal operation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a force sensor that senses force, and more particularly to a multi-axis force sensor that senses a plurality of axial translational forces and moments about a plurality of axes.

  A sensor is a device that converts a physical quantity that can be detected by, for example, the five senses of an animal into a signal that can be easily processed by an electronic device such as a computer. Various sensors such as sound, light, temperature, pressure, and flow rate are prevalent.

  Of these, the force sensing force is widely used to measure the force applied to materials and structures. Recently, in user operations via the touch panel of information devices (such as personal computers, PDAs (Personal Digital Assistants), and game machines), and further through communication with contacts with robots that are active in daily life, It is also used as a device that detects tactile movements.

  In order to be incorporated into such various products, it is desired to produce multi-axis force and to manufacture at low cost and in a small size.

  For example, a 6-component force sensor that can be easily miniaturized and can independently detect each force component of 6-component force has been proposed (see, for example, Patent Document 1). This six-axis force sensor is a tenth unit formed by integrating first and second sensor elements extending in the first and second axis directions orthogonal to each other in a cross shape at each longitudinal intermediate portion. A second cruciform sensor disposed in parallel with a gap in a third axial direction perpendicular to both the first axis and the second axis between the letter-shaped sensor and the first cruciform sensor; One of the second cruciform sensors is used to detect the translational force in the third axis direction and each moment around the first and second axes, and the other of the first and second cruciform sensors is the first and second ones. It is used to detect each translational force in the biaxial direction and moment about the third axis. In short, as shown in FIG. 17, this 6-axis force sensor is a structure composed of a strain generating body extending in each of the first to third axial directions, and outputs the output of a strain gauge adhered to the side surface of the strain generating body. Based on this, the translational force in each axial direction and the moment around each axis are detected. However, according to such a measuring method, it is necessary to sufficiently distort the strain generating body, in other words, the length of the strain generating body is required, and it is difficult to manufacture the sensor with a small diameter.

  In addition, the troublesome manual work of attaching the strain gauge can be omitted by forming the strain gauge in a process by sputtering rather than bonding the strain gauge to the strain generating body (for example, Patent Document 2). In order to sufficiently distort the strain generating body, the sensor cannot be manufactured with a small diameter.

  In addition, as shown in FIG. 18, when a plurality of pillars are built on the base and a force is applied to any of the pillars, the strain generated in the base portion near the base of the pillar (using a strain gauge not shown) A proposal has been made regarding a multi-axis sensor to be detected (see, for example, Patent Document 3). However, since the strength of each column and the distance from the center of the base to the column are necessary, the point that the sensor cannot be manufactured with a small diameter is not different from the above. In addition, even if force is applied to only one of the columns, it also affects the strain gauge at the base of the other column, so interference removal calculation is performed to extract the force and moment for each axis. There is a need.

JP 2000-266620 A JP-A-2005-300465 JP 2005-31062 A

  An object of the present invention is to provide an excellent force sensor having a multi-axis configuration that senses a plurality of axial translational forces and moments about a plurality of axes.

  A further object of the present invention is to provide an excellent multi-axis force sensor that can be manufactured at a low cost and in a small size.

The present application has been made in consideration of the above problems, and the invention according to claim 1
A first measurement unit for measuring translational forces F _x and F _y in the XY directions;
A plurality of pressure sensing units that sense a force applied in the Z direction are arranged in a distributed manner on the XY plane, and based on a plurality of Z direction forces sensed by each pressure sensing unit, a translational force F _z in the Z direction, and XY about each axis moment M _x, and a second measuring unit for measuring the M _y,
A force sensor.

  According to the invention described in claim 2 of the present application, the first measurement unit is configured by a strain sensor and a strain sensor that detects strain in two directions of the strain body.

  According to the invention described in claim 3 of the present application, the plurality of pressure sensitive parts of the second measuring part are composed of a conductive pressure sensitive rubber type element whose resistance value is changed by rubber compression.

  Further, according to the invention described in claim 4 of the present application, the plurality of pressure sensitive units of the second measurement unit is a capacitance type in which the capacitance changes as the interval between the electrostatic plates changes. It consists of the element.

  According to the present invention, it is possible to provide an excellent force sensor having a five-axis configuration that senses a plurality of axial translational forces and moments about a plurality of axes.

  In addition, according to the present invention, it is possible to provide an excellent multi-axis force sensor that can be manufactured at a low cost and in a small size.

According to the invention described in claim 1 of the present application, the first measurement unit measures the translational forces F _x and F _y in the XY directions based on the strain in the two directions of the strain generating body, while the second measurement. Unit calculates a plurality of Z-direction translational forces obtained from a plurality of pressure-sensitive parts distributed on the XY plane, and together with the Z-direction translational force F _z , moments M _x around the XY axes, and to calculate the M _y, it can be fabricated and compact at a low cost.

According to the invention described in claim 2 of the present application, when the strain generating body is bent in two directions, the translational forces F _x and F _y in each direction are measured based on the measurement result by the strain gauge 3. be able to.

Further, according to the invention described in claim 3 of the present application, when a force in the Z direction is applied, it is applied to each pressure sensitive part from a change in resistance value of each pressure sensitive part of the conductive pressure sensitive rubber system. the calculated force F ₀ to F _3, the force F ₀ to F ₃ in the Z direction of the translational force F _z, and XY around the axes moments M _x, can be obtained M _y.

Further, according to the invention described in claim 4 of the present application, when a force in the Z direction is applied, each sensitivity is detected from a change in measured voltage accompanying a change in capacitance of each pressure sensitive part of the capacitance method. the calculated force F ₀ to F ₃ applied to the pressure part, a translational force in the Z direction from each force F ₀ ~F ₃ F _z, and XY around the axes moments M _x, can be obtained M _y.

According to the invention described in claim 3 and 4, the conductive pressure sensitive rubber or the capacitance of the two axes of the moment (M _x, M _y) on the grounds that used to detect the distortion of the flexure element It is possible to reduce the distance for storing. As a result, the outer diameter of the sensor can be reduced. Further, since the structure is simple, the height can be reduced to 10 mm or less, and there is no need to perform complicated interference removal calculation. In addition, since the strain gauge is used for detecting the translational forces (F _x , F _y ) in two directions, it is possible to reduce the deviation of the reference. Furthermore, because of the use of a conductive pressure-sensitive rubber part or a capacitance part and a strain gauge, the conductive pressure-sensitive rubber (tens of yen) + strain gauge (several hundred yen) + structure cost is low, and it is 1 It is possible to manufacture at about / 10.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

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

  1 and 2 show an assembly configuration and an exploded view of a five-axis force sensor according to an embodiment of the present invention, respectively.

  The illustrated five-axis force sensor 10 includes a pressure-sensitive unit 1 that changes a resistance value or capacitance according to an amount of strain generated by pressure applied in a height direction (Z-axis direction), and a resistance in the pressure-sensitive unit 1. A sensor unit 2 that measures a change in body or capacitance as a voltage signal, and a substantially quadrangular prism shape in which two sets of strain gauges 3 for measuring the amount of strain in the X-axis direction and Y-axis direction are arranged on the surface The strain body 4, the first to third structures 6 to 8 that support these sensor components 1 to 4, and the locking portion 5 that locks the structure. A strain gauge is a device that detects a minute change in mechanical dimensions as an electrical signal (well known).

  The pressure sensing unit 1 and the sensor unit 2 are sandwiched between the first structure 6 and the third structure 8. Further, the first structure 6 and the second structure 7 are pole joints, and the Nasu first structure 6 is supported by the structure 7 so as to be rotatable along the center of the arc. ing. In addition, the strain body 4 and the first structure 6 are fastened by the locking portion 5 and are applied with a certain pressure.

FIG. 3 illustrates an operating principle for the 5-axis force sensor 10 shown in FIG. 1 to measure the translational forces F _x and F _y in the horizontal direction, that is, in the X-axis direction and the Y-axis direction.

As shown in FIGS. 1 and 2, the structure body 7 is fastened to the strain body 4 via the structure body 6. Therefore, when the translational forces F _x and F _y are applied to the structure 7, the structure 7 slides in the horizontal direction (that is, in the XY plane), and accordingly, the strain body 4 moves in the X-axis or Y-axis direction. Since the bending occurs, the translational forces F _x and F _y can be measured based on the measurement result by the strain gauge 3. Such strain gauge type sensor configurations are well known in the art and will not be described further herein. The function of measuring the translation forces F _x and F _y in the two directions corresponds to the first measurement unit in claim 1 of the present application.

FIG. 4 shows a configuration example of the pressure sensitive unit 1. In the illustrated example, the pressure-sensitive part 1 is composed of four uniform conductive pressure-sensitive rubber parts 1-0, 1-1, 1-2, and 1-3, and the resistance value changes in accordance with the amount of strain. Acting as variable resistors R _{0 to} R ₃ . The pressure sensitive unit 1 corresponds to a second measuring unit in claim 1 of the present application.

FIG. 5 shows an arrangement example of the variable resistors R _{0 to} R _{3 including} the conductive pressure-sensitive rubber portions 1-0, 1-1, 1-2, and 1-3.

With respect to the XY plane for measuring the translational forces F _x and F _y using the strain body 4, the variable resistors R _{0 to} R ₃ are in concentric circles separated from the origin by a distance L in the first to fourth quadrants. Just distributed.

FIG. 6 shows an equivalent circuit of the sensor unit 2 that measures the resistance values of the variable resistors R _{0 to} R _{3 included in} the pressure sensing unit 1.

The addition of Z-direction force to the pressure sensing section 1, the resistance value of the variable resistor R ₀ to R ₃ are changed. The sensor unit 2 measures changes in the resistance values R _{0 to} R ₃ as changes in the voltages V _{0 to} V ₃ , respectively.

Each variable resistor R ₀ to R relative to the measurement voltage V ₀ ~V ₃ from _3, by performing a predetermined calibration, the conductive pressure sensitive rubber portion 1-0,1-1,1-2, It can be converted into forces F _{0 to} F ₃ applied to 1-3. Further, by the following equation (1), each force F ₀ to F ₃ in the Z direction of the translational force F _z, and XY around the axes moments M _x, can be obtained M _y.

Figure 7, is a 5-axis force sensor 10 shown in FIG. 1, the translational force in the height direction, that is Z-axis direction F _z, and X-axis or Y-axis moment M _x, the operation for measuring the M _y Illustrates the principle.

Pressing the Z-axis direction of the entire construction 7 from above, the conductive pressure sensitive rubber portion 1-0,1-1,1-2,1-3 in response to forces F _z that pressure sensing section 1 is applied almost By being uniformly compressed, each of the resistance values R _{0 to} R ₃ changes almost the same. Then, the sensor unit 2 can convert the change in resistance in the pressure sensing section 1 into a voltage signal, measuring the translational force F _z in the X-axis direction in accordance with further the above equation (1). When the moment component is not included in the force applied to the structure 7, forces F _{0 to} F ₃ measured from the conductive pressure-sensitive rubber portions 1-0, 1-1, 1-2, _1-3. since the constant in the above equation (1), the moment M _x, M _y are both zero.

On the other hand, when the end of the structure 7 is pushed in the Z direction, only a part of the conductive pressure-sensitive rubber parts 1-0, 1-1, 1-2, 1-3 is compressed (or compressed non-uniformly). Each of the resistance values R _{0 to} R ₃ varies non-uniformly. Then, the sensor unit 2 converts the change of the resistor in the pressure sensing unit 1 into a voltage signal, and further translates the translation force F _{z in} the X-axis direction and the moment M _x about the X-axis or Y-axis according to the above equation (1). , it can be measured M _y.

According to the embodiment in which the pressure sensitive part 1 as shown in FIGS. 4 to 6 is composed of four uniform conductive pressure sensitive rubber parts 1-0, 1-1, 1-2, 1-3. the conductive pressure-sensitive rubber 2 about the axis of the moment (M _x, M _y) on the grounds that used to detect, it is possible to reduce the distance to distort the flexure element. As a result, the outer diameter of the sensor can be reduced. Further, since the structure is simple, the height can be reduced to 10 mm or less, and there is no need to perform complicated interference removal calculation. In addition, since the strain gauge is used for detecting the translational forces (F _x , F _y ) in two directions, it is possible to reduce the deviation of the reference. Furthermore, because of the use of the conductive pressure-sensitive rubber part and strain gauge, it is possible to produce the conductive pressure-sensitive rubber (several tens of yen) + strain gauge (several hundred yen) + structure cost at a low cost. The price corresponds to about 1/10 of the ready-made product.

The 8 to 12, in 5-axis force sensor 10 shown in FIG. 1, the translational force _{F x, F y, F z} , and X-axis or Y-axis moment M _x, the output obtained by measuring the M _y The data is illustrated. In each figure, the horizontal axis is time [second], and the vertical axis is output voltage value [V]. However, in all cases, the sampling rate is 100 microseconds.

  4 to 6 show an embodiment in which the pressure-sensitive part 1 is composed of four uniform conductive pressure-sensitive rubber parts 1-0, 1-1, 1-2, and 1-3. Instead of the pressure rubber, the pressure-sensitive portion 1 can be configured by using four capacitance portions that change the capacitance according to the pressure.

FIG. 13 shows an arrangement example of the capacitance units C _{0 to} C ₃ . With respect to the XY plane in which the translational forces F _x and F _y are measured using the strain body 4, the capacitance units C _{0 to} C ₃ are first to fourth on concentric circles separated by a distance L from the origin. Distributed just in the quadrant.

FIG. 14 shows an equivalent circuit of the sensor unit 2 that measures the capacitances of the capacitance units C _{0 to} C _{3 included in} the pressure-sensitive unit 1.

  The capacitance C of the capacitor is determined by the dielectric constant ε between the opposing electrode plates, the area S of the electrode plates, and the distance d between the electrode plates, and C = εS / d is established (well known). Therefore, when a force is applied to the capacitance portion and the distance d between the electrode plates decreases, the charge curve changes as shown in FIG. 15 according to the amount of change in the capacitance C associated therewith.

The sensor unit 2 measures voltages V _{0 to} V ₃ from the capacitance units C _{0 to} C _{3 at} time t ₁ . Then, for each measurement voltage V ₀ ~V _3, by performing a predetermined calibration can be converted to a force F ₀ to F ₃ applied to the capacitive element C ₀ -C _3. Further, by the following equation (2), each force F ₀ to F ₃ in the Z direction of the translational force F _z, and XY around the axes moments M _x, can be obtained M _y.

As shown in FIG. 7, when the entire structure 7 is pushed in the Z-axis direction from above, each electrostatic capacity part is compressed almost uniformly according to the force F _z applied by the pressure-sensitive part 1, Each of the capacitance values C _{0 to} C ₃ changes almost the same. Then, the sensor unit 2 can convert the change in capacitance in the pressure sensing section 1 into a voltage signal, measuring the translational force F _z in the X-axis direction in accordance with further the above equation (2).

On the other hand, when the end portion of the structure 7 is pushed in the Z direction, only a part of the capacitance portion is compressed (or compressed non-uniformly), and the capacitance values C _{0 to} C ₃ become non-uniform. Change. The sensor unit 2 converts the capacitance change in the pressure sensing unit 1 into a voltage signal, and further translates the translation force F _{z in} the X-axis direction and the moment M about the X-axis or Y-axis according to the above equation (2). _x, it is possible to measure the M _y.

According to the embodiment the pressure sensitive portion 1 as shown in FIGS. 13 14 are constituted by four uniform capacitance unit, the capacitance section 2 about the axis of the moment (M _x, M _y ), The distance for distorting the strain generating body can be reduced. As a result, the outer diameter of the sensor can be reduced. Further, since the structure is simple, the height can be reduced to 10 mm or less, and there is no need to perform complicated interference removal calculation. In addition, since the strain gauge is used for detecting the translational forces (F _x , F _y ) in two directions, it is possible to reduce the deviation of the reference. Furthermore, because it uses a capacitance part and a strain gauge, it can be manufactured at a low cost: capacitance part (tens of yen) + strain gauge (several hundred yen) + structure cost. Corresponds to about 1/10 of the ready-made product.

Up to now, the 5-axis force sensor has been described, but if the strain gauge attached to the strain generating body 4 is arranged so that the two strain gauges intersect at 90 degrees as shown in FIG. The torsional moment _Mz can be detected, and a six-axis force sensor can be configured. In other words, the gist of the present invention is not limited to 5-axis detection.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention.

5-axis force sensor according to the present invention, for example, attached to the end effector, such as a fingertip of the robot, translational forces in three axial directions _{F x, F y, F z} , and 2 about the axis of moment M _x, the M _y Although it can be used for sensing, the gist of the present invention is not limited to this. For example, the 5-axis force sensor according to the present invention can be applied to information equipment, home appliances, and various industrial equipment.

  In short, the present invention has been disclosed in the form of exemplification, and the description of the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

FIG. 1 is a view showing an assembly configuration of a five-axis force sensor according to an embodiment of the present invention. FIG. 2 is an exploded view of a 5-axis force sensor according to an embodiment of the present invention. FIG. 3 is a diagram for explaining an operating principle for the 5-axis force sensor 10 shown in FIG. 1 to measure the translational forces F _x and F _y in the X-axis direction and the Y-axis direction. FIG. 4 is a diagram illustrating a configuration example of the pressure sensitive unit 1. FIG. 5 is a diagram showing an arrangement example of the variable resistors R _{0 to} R _{3 including} the conductive pressure-sensitive rubber portions 1-0, 1-1, 1-2, and 1-3. FIG. 6 is a diagram illustrating an equivalent circuit of the sensor unit 2 that measures resistance values of the variable resistors R _{0 to} R _{3 included in} the pressure-sensitive unit 1. Figure 7 is a five-axis force sensor 10 shown in FIG. 1 is the Z-axis direction of the translational force F _z, and X-axis or Y-axis moment M _x, for explaining the operating principle for measuring the M _y FIG. Figure 8 is a diagram showing an output example of data obtained by measuring the translational force F _x in the 5-axis force sensor 10 shown in FIG. Figure 9 is a diagram showing an output example of data obtained by measuring the translational force F _y in 5-axis force sensor 10 shown in FIG. Figure 10 is a diagram showing an output example of data obtained by measuring the translational force F _z in the 5-axis force sensor 10 shown in FIG. FIG. 11 is a diagram illustrating an example of output data obtained by measuring the moment M _x about the X axis in the five-axis force sensor 10 illustrated in FIG. 1. Figure 12 is a diagram showing an output example of data obtained by measuring the moment M _y around the Y axis in the 5-axis force sensor 10 shown in FIG. FIG. 13 is a diagram illustrating an arrangement example of the capacitance units C _{0 to} C ₃ . FIG. 14 is a diagram illustrating an equivalent circuit of the sensor unit 2 that measures the capacitances of the capacitance units C _{0 to} C _{3 included in} the pressure-sensitive unit 1. FIG. 15 is a diagram illustrating charge curves of the capacitance units C _{0 to} C ₃ . FIG. 16 is a view showing a modification of the strain body 4 and the strain gauge 3. FIG. 17 is a diagram exemplifying a structure made of a strain generating body extending in each of the first to third axial directions. FIG. 18 is a diagram showing a multi-axis sensor that detects a strain generated in a base portion near the base of a pillar when a plurality of pillars are built on the base and a force is applied to any of the pillars.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pressure-sensitive part 2 ... Sensor part 3 ... Strain gauge 4 ... Strain body 5 ... Locking part 6 ... 1st structure 7 ... 2nd structure 8 ... 3rd structure 10 ... 5-axis force sensor

Claims (4)

A first measurement unit for measuring translational forces F _x and F _y in the XY directions;
A plurality of pressure sensing units that sense a force applied in the Z direction are arranged in a distributed manner on the XY plane, and based on a plurality of Z direction forces sensed by each pressure sensing unit, a translational force F _z in the Z direction, and XY about each axis moment M _x, and a second measuring unit for measuring the M _y,
A force sensor comprising: The first measurement unit includes a strain body and a strain sensor that detects strain in two directions of the strain body.
The force sensor according to claim 1. The plurality of pressure-sensitive parts of the second measurement unit are composed of a conductive pressure-sensitive rubber type element whose resistance value is changed by rubber compression.
The force sensor according to claim 1 or 2, wherein The plurality of pressure sensing units of the second measurement unit are composed of capacitance type elements in which the capacitance changes as the interval between the electrostatic plates varies.
The force sensor according to claim 1 or 2, wherein