JP2008096240A - Force detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost force detector that is of a simple structure and is high in performance. <P>SOLUTION: Single axis force sensors 2-1, 2-2, 2-3 are provided between a support 1 and a force-receiving body 3. The single axis force sensors 2-1, 2-2, 2-3 detect only force F1, F2, F3 in a Z-axis direction (direction vertical with respect to the support 1) operating on detection points P1, P2, P3 with the points P1, P2, P3 obtained by dividing the circumference with a prescribed radius (r) in the same plane, with a connection point (origin O) between the force-receiving body 3 and a force-transmitting body 4 as a center, at an interval of 120° as detection points. With the forces F1, F2, F3 that are detected by the single axis force sensors 2-1, 2-2, 2-3, force components Fx, Fy, Fz in the direction of each axis of the forces X, Y, Z to be detected acting on a force-receiving point P are obtained by a prescribed arithmetic expression. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a force detection device that detects a force to be detected that acts on a force receiving point.

  Conventionally, as a force detection device of this type, a cross-shaped body in the X and Y directions is formed by parallel leaf springs that are displaceable in the X, Y, and Z directions orthogonal to each other, and distortion is applied to the parallel leaf springs on each side of the cross. A force detection device provided with a gauge is used (see, for example, Patent Document 1).

  In this force detection device, the force component in the X, Y, and Z axial directions of the force to be detected acting on the center of the cross is easily detected from the output of the strain gauge provided on the parallel leaf springs on each side of the cross. can do. However, this force detection device requires a cross-shaped body made up of parallel leaf springs that can be displaced in the X, Y, and Z directions, and has a drawback that the structure is complicated.

  On the other hand, in the force detection device disclosed in Patent Document 2, a support body is disposed below the power receiving body that receives the force to be detected, and at least two force transmissions are provided between the power receiving body and the support body. The direction perpendicular to the support is defined as the Z-axis direction from the change in the capacitance value of the capacitive element type multi-axis force sensor provided at the joint between each force transmission body and the support. The force components in the X, Y, and Z axial directions of the detection target force are detected. This makes the structure simple and suitable for mass production.

Japanese Patent Application Laid-Open No. 61-292029 JP 2004-354049 A

  However, the force detection device disclosed in Patent Document 2 described above is simple in structure, but is expensive because it uses a capacitive element type multi-axis force sensor. In addition, since the capacitive element type multi-axis force sensor has high electrical impedance, noise is increased and it is easily affected by ambient temperature.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide an inexpensive force detection device having a simple structure and high performance.

  In order to achieve such an object, the present invention is provided between a force receiving body that receives a force to be detected acting on the force receiving point via a force transmitting body, and between the force receiving body and the support body, The direction perpendicular to the support is defined as the Z-axis direction, and three or more points on the circumference of a predetermined radius within the same plane centering on the coupling point of the force receiving body with the force transmitting body are used as detection points. From the force sensor that detects only the force in the Z-axis direction that acts on each of these detection points, and the force that the force sensor detects, the forces of the detection targets that act on the force-receiving point are mutually determined using a predetermined arithmetic expression. Force component calculation means for obtaining force components in the X, Y, and Z axis directions orthogonal to each other is provided.

  According to the present invention, when the force receiving point is, for example, point P, the force to be detected acting on the point P is applied to the force receiving member via the force transmitting member. The force of the detection target received by the force receiving body appears in a distributed manner at each detection point on the circumference of a predetermined radius within the same plane centering on the coupling point (origin O) of the force receiving body with the force transmitting body. Only the force acting in the Z-axis direction (direction perpendicular to the support) at each detection point is detected by a force sensor (single-axis force sensor). Then, based on the force detected by the force sensor, the force components (Fx, Fy) in the X, Y, and Z axial directions of the detection target force acting on the force receiving point (P point) using a predetermined arithmetic expression. , Fz).

  In the present invention, the coupling point of the force receiving body with the force transmitting body is defined by defining the surface of the power receiving body in contact with the force transmitting body as the front side of the power receiving body. Included points are also included. That is, not the point on the surface of the force receiving body that contacts the force transmitting body, but the point on the back surface side of the force receiving body facing this surface also refers to the coupling point in the present invention.

  In the present invention, for example, detection points P1, P2, and P3 obtained by dividing the circumference of a predetermined radius r in the same plane centered at the origin O at intervals of 120 ° are detected points P1 detected by the force sensor. , P2 and P3 in the Z-axis direction are F1, F2, and F3, the following formulas (1), (2), and (3) are used as the predetermined calculation formulas. A force component Fx in the X-axis direction, a force component Fy in the Y-axis direction, and a force component Fz in the Z-axis direction of the acting detection target force are obtained. In the following equations (1) and (2), L is the distance from the origin O to the force receiving point P in the Z-axis direction.

  In the present invention, it is conceivable that a moment force centered on the detection point is generated at each detection point of the force receiving body. In order to absorb such moment force, a diaphragm portion having a predetermined range thinned around the detection point is provided for each detection point of the force receiving body, and the end surface of the force sensor is provided in contact with the diaphragm portion. Alternatively, a ball joint may be provided at each detection point of the force receiving body, and the force in the Z-axis direction acting on each detection point via this ball joint may be detected by a force sensor.

  Further, in the present invention, when a force transmission body is used as a work and the work is gripped with a hand, a moment force centered on the force receiving point, especially a moment force around the Z axis may be received. It is done. In order to absorb such moment force, a rotary joint may be provided at the coupling portion between the force transmission body and the force receiving body. Further, it is possible to combine the provision of a rotation joint at the coupling portion between the force transmission body and the force receiving body and the thinning of a predetermined range including the detection point for each detection point of the force receiving body. Alternatively, a combination of providing a ball joint at each detection point of the force receiving member may be combined.

  According to the present invention, three or more points on the circumference of a predetermined radius in the same plane centering on the coupling point of the force receiving body with the force transmitting body are set as detection points, and Z acting on each of these detection points. Only the force in the axial direction is detected by a force sensor, and the force component in each axial direction of X, Y, and Z to be detected that acts on the force receiving point using a predetermined arithmetic expression from the force detected by the force sensor. Therefore, the structure can be simplified, and the cost sensor can be reduced as a single-axis force sensor that does not use a capacitive element. In addition, it is possible to reduce the electrical impedance, make it less susceptible to noise and ambient temperature, and improve performance.

Hereinafter, the present invention will be described in detail with reference to the drawings.
[Embodiment 1]
FIG. 1 is a diagram showing a main part of an embodiment of a force detection device according to the present invention. 1A is a plan view and FIG. 1B is a side view. In the figure, 1 is a base support, 2 (2-1, 2-2, 2-3) is a single-axis force sensor, 3 is a force receiving body, 4 is a force transmission body, and 5 is a force component calculation unit. It is.

  In this example, the force transmission body 4 is a shaft body, the point P of the upper end surface 4 a is the force receiving point where the force to be detected acts, and the lower end surface 4 b is at the center of the force receiving body 3. It is fixed. Further, the support body 1 and the force receiving body 3 are formed in a disk shape, and the upper end surface 2a is in contact with the force receiving body 1 between the support body 1 and the force receiving body 3, and the lower end surface 2b is supported. In contact with the body 1, single-axis force sensors 2-1, 2-2, 2-3 are provided.

  The single-axis force sensors 2-1, 2-2, 2-3 are force sensors that detect only the force acting in the axial direction, and are the connection points of the force receiving body 3 and the force transmitting body 4 (origin O). The points P1, P2, and P3 obtained by dividing the circumference of the predetermined radius r in the same plane centered at 120 ° intervals (equal angular intervals) are used as detection points, and are positioned at the detection points P1, P2, and P3. Has been placed.

  In this embodiment, when the surface of the force receiving body 3 that contacts the force transmitting body 4 is the front surface side of the force receiving body 3, the point O located on the back surface side of the force receiving body 3 is defined as the force receiving body 3. The connection point with the force transmission body 4 is used. Considering not only the surface of the force receiving body 3 in contact with the force transmitting body 4 but also the force transmitting body 4 including the thickness of the force receiving body 3, the point O located on the back side of the force receiving body 3 is It can be said that this is a connection point between the force receiving body 3 and the force transmitting body 4.

  As a result, the single-axis force sensors 2-1, 2-2, 2-3 take the direction perpendicular to the support 1 as the Z-axis direction and act on the detection points P1, P2, P3 in the Z-axis direction. Only the forces F1, F2 and F3 are detected. In this embodiment, a strain gauge type force sensor with minimal displacement is used as the single-axis force sensor 2 (2-1, 2-2, 2-3). The single-axis force sensor 2 is a rigid body and does not deform even when a force in the X, Y, and Z directions is applied to the force receiving point P.

  The force component calculation unit 5 receives the forces F1, F2, and F3 detected by the single-axis force sensors 2-1, 2-2, and 2-3, and uses the forces F1, F2, and F3 as a predetermined calculation formula below. Using the equations (4), (5), and (6), the force component Fx in the X-axis direction, the force component Fy in the Y-axis direction, the force component Fy in the Y-axis direction, and the force in the Z-axis direction. It has a function for obtaining the force component Fz.

[Derivation of arithmetic expression]
The above equations (4), (5), and (6) are derived as follows.
In the three-dimensional space of XYZ, the coordinate positions of the detection points P1, P2, and P3 are expressed by the following equations (7), (8), and (9) (see FIG. 2). Further, assuming that the force receiving point P at which the force to be detected acts is P4 and the distance from the origin O to the force receiving point P4 is L, the coordinate position of the force receiving point P4 is expressed by the following equation (10). (See FIG. 3).

  Here, the forces acting on the points P1, P2, P3, and P4 are assumed to be vectors f1, f2, f3, and f4. The force components in the Z-axis direction of f1, f2, and f3 are forces F1, F2, and F3 detected by the single-axis force sensors 2-1, 2-2, and 2-3. Expressions for obtaining the force component f4x in the X-axis direction, the force component f4y in the Y-axis direction, and the force component f4z in the Z-axis direction of the detection target force f4 acting on the force receiving point P4 using the forces F1, F2, and F3 To derive.

  In this case, the balance between static force and moment is used to derive the force components f4x, f4y, and f4z. The balance of force is expressed by the following equation (11). The balance of moment is expressed by the following equation (12). In Equation (12), Mn is a moment force generated around each point Pn, and Pn × fn is a moment force generated around the origin O by the force fn acting on each point Pn.

  Further, in the equation (12), Pn × fn is an X axis that acts on the coordinate position in the X axis direction at the point Pn as Pnx, the coordinate position in the Y axis direction as Pny, the coordinate position in the Z axis direction as Pnz, and the Pn point. When the force component in the direction is fnx, the force component in the Y-axis direction is fny, and the force component in the Z-axis direction is fnz, it is expressed by the following equation (13).

  Here, when a condition that no moment force is generated at each point Pn is added, the above expression (12) becomes the following expression (14). In this equation (14), P1 × f1, P2 × f2, P3 × f3, and P4 × f4 are expressed by the following equation (15) from the above equation (13).

  In this equation (15), since the added values of P1 × f1, P2 × f2, P3 × f3, and P4 × f4 are 0, the added value for each of the x, y, and z components is also 0. In this case, the added value for each x, y, z component is expressed by the following equation (16).

  From this equation (16), the force component f4x in the X-axis direction and the force component f4y in the Y-axis direction of the force f4 acting on the force receiving point P4 are expressed by the following equations (17) and (18). It becomes. Further, from the equation (11), the force component f4z in the Z-axis direction of the force f4 acting on the force receiving point P4 is represented by the following equation (19).

  Here, when the force component f4x in the X-axis direction of the force f4 acting on the force receiving point P4 is Fx, the force component f4y in the Y-axis direction is Fy, and the force component f4z in the Z-axis direction is Fz, f1z is a single-axis force. Forces F1 and f2z in the Z-axis direction acting on the detection point P1 detected by the sensor 2-1 are forces F2 and f3z in the Z-axis direction acting on the detection point P2 detected by the single-axis force sensor 2-2 and are uniaxial forces. Since it is the force F3 in the Z-axis direction acting on the detection point P3 detected by the sensor 2-3, the expression (17) is expressed as an expression (4), the expression (18) is expressed as an expression (5), ( The equation 19) is expressed as the equation (6).

  Thus, in the present embodiment, from the forces F1, F2, and F3 in the Z-axis direction acting on the detection points P1, P2, and P3 detected by the single-axis force sensors 2-1, 2-2, and 2-3. Formulas (4), (5), and (4) for obtaining a force component Fx in the X-axis direction, a force component Fy in the Y-axis direction, and a force component Fz in the Z-axis direction of the force to be detected acting on the force receiving point P (P4). (6) is derived.

[Operation]
In this force detection device, the force to be detected acting on the force receiving point P is applied to the force receiving body 3 via the force transmitting body 4. The detection target force received by the force receiving body 3 is a detection point P1 obtained by dividing the circumference of a predetermined radius r centering on the coupling point (origin O) between the force receiving body 3 and the force transmitting body 4 at intervals of 120 °. , P2 and P3, and only the forces F1, F2 and F3 acting in the Z-axis direction at the detection points P1, P2 and P3 are detected by the single-axis force sensors 2-1, 2-2 and 2-3. To the force component calculation unit 5.

  The force component calculation unit 5 uses the above formulas (4), (5), (6) from the forces F1, F2, F3 sent from the single-axis force sensors 2-1, 2-2, 2-3. Is used to determine the force component Fx in the X-axis direction, the force component Fy in the Y-axis direction, and the force component Fz in the Z-axis direction of the force to be detected acting on the force receiving point P.

  In this way, in the present embodiment, the detection target X, Y, and Y acting on the force receiving point P from the forces F1, F2, and F3 detected by the single-axis force sensors 2-1, 2-2, and 2-3. Since the force components Fx, Fy, and Fz in the Z-axis directions are obtained, the cost can be reduced as compared with the conventional method using the capacitive element type multi-axis force sensor. Become. In addition, it is possible to reduce the electrical impedance, make it less susceptible to noise and ambient temperature, and improve performance.

  FIG. 4 is a diagram showing an example in which this force detection device is applied to the tip of a robot arm. In this example, the force transmission body 4 is a work, and the work 4 is gripped by the hand 6 and is inserted into a hole (not shown) so that the robot can perform the work. In this case, the work 4 enters the inside of the hand 6, and the lower end surface 4 b abuts against the center of the force receiving body 3, thereby transmitting the detection target force acting on the force receiving point P to the force receiving body 3.

  In this application example to the robot, the work 4 and the force receiving body 3 are not fixed, and when the work is finished, the work 4 is separated from the force receiving body 3, but the work 4 is in contact with the force receiving body 3. In the present invention, it is assumed that the force transmission body and the force receiving body are in a coupled state. That is, not only the state in which the work 4 is fixed to the force receiving body 3 but also the state in which the work 4 is in contact with the force receiving body 3 is regarded as a coupled state. The same applies to the coupling of the single-axis force sensor 2 with the support 1 and the force receiving body 3.

[Embodiment 2]
In the first embodiment, the above arithmetic expressions (4), (5), and (6) are derived on the condition that no moment force is generated at the detection points P1, P2, and P3. In this case, when a moment force is generated at the detection points P1, P2, and P3, the force component Fx in the X, Y, and Z axial directions of the detection target force acting on the force receiving point P obtained by the force component calculation unit 5 is obtained. , Fy, and Fz have errors.

  Therefore, in the second embodiment, in order to absorb the moment force generated at the detection points P1, P2, and P3, as shown in FIG. 5, the detection point is set for each of the detection points P1, P2, and P3 of the force receiving body 3. Diaphragm portions 3a, 3b, and 3c having a predetermined thickness as a center are provided, and the diaphragm portions 3a, 3b, and 3c are provided in contact with the end surfaces of the single-axis force sensors 2-1, 2-2, and 2-3. Like that.

  In this case, the moment force generated at the detection points P1, P2, P3 is absorbed by the deformation of the diaphragm portions 3a, 3b, 3c, and the detection target force X acting on the force receiving point P determined by the force component calculation unit 5 is obtained. , Y, Z axial force components Fx, Fy, Fz are less likely to cause errors.

[Embodiment 3]
In the second embodiment, the diaphragm 3a, 3b, 3c is provided on the force receiving body 3 in order to absorb the moment force generated at the detection points P1, P2, P3. However, as shown in FIG. Ball joints 7-1, 7-2, 7-3 are provided at P2, P3, and the forces in the Z-axis direction acting on the detection points P1, P2, P3 are applied to the ball joints 7-1, 7-2, 7-3. May be detected by the single-axis force sensors 2-1, 2-2, 2-3.

  In this case, the moment force generated at the detection points P 1, P 2, P 3 is absorbed by the slip of the ball joints 7-1, 7-2, 7-3 and acts on the force receiving point P determined by the force component calculation unit 5. Errors are less likely to occur in the force components Fx, Fy, and Fz in the X, Y, and Z axial directions of the force to be detected.

[Embodiment 4]
As shown in FIG. 4, when the work is performed with the force transmission body 4 as a work and the work 4 is held by the hand 6, the moment force around the force receiving point P, particularly the moment about the Z axis. It is possible to receive power. Therefore, in the fourth embodiment, in order to absorb such moment force, as shown in FIG. 7, a rotary joint 8 is provided at a joint portion between the workpiece 4 and the force receiving body 3.

  The rotary joint 8 is composed of a rotary bearing and a thrust bearing, and rotates when receiving a moment force around the Z axis while receiving a load in the Z axis direction. As a result, the moment force around the Z axis centered on the force receiving point P is absorbed, and the X, Y, and Z axial directions of the detection target force acting on the force receiving point P determined by the force component calculation unit 5 An error is less likely to occur in the force components Fx, Fy, and Fz.

  In the second embodiment (FIG. 5) and the third embodiment (FIG. 6), as in the fourth embodiment, the rotary joint 8 is provided at the joint between the workpiece 4 and the force receiving body 3. Also good.

  In the first to fourth embodiments described above, the points P1, P2, and P3 obtained by dividing the circumference of the predetermined radius r around the origin O of the force receiving member 3 at intervals of 120 ° are used as detection points. The points P1, P2, and P3 are not necessarily provided at intervals of 120 ° (equal angular intervals). That is, the detection points P1, P2, and P3 may be provided on the circumference of the predetermined radius r at unequal angular intervals. Further, the number of detection points is not limited to three of P1, P2, and P3, and the number thereof may be further increased.

  When Fx, Fy, and Fz are obtained from the X, Y, and Z components by generalizing the above equations (11) and (12), the following equation (20) can be derived. From this equation, even if a plurality of detection points are freely arranged on the same plane of the origin O, the three-axis component of the force at the force receiving point P can theoretically be obtained. However, the condition is that no moment is generated at each detection point.

  However, in this equation (20), the number of force detection points: N, the coordinates of the force detection points: (Pnx, Pny, 0), the force of the force detection points: (fnx, fny, fnz), the force receiving point P Coordinates: (0, 0, L), L ≠ 0, force at force receiving point P: (Fx, Fy, Fz), force detection point and moment around force receiving point P: 0.

It is the top view and side view which show the principal part of one Embodiment of the force detection apparatus which concerns on this invention. It is a figure which shows the coordinate position of detection point P1, P2, P3 in this force detection apparatus. It is a figure which shows the coordinate position of the detection point P4 in this force detection apparatus. It is a figure which shows the example (Embodiment 1) which applied this force detection apparatus to the front-end | tip of the arm part of a robot. It is a figure which shows the example (Embodiment 2) which provided the diaphragm part in the detection point of the power receiving body. It is a figure which shows the example (Embodiment 3) which provided the ball join in the detection point of the power receiving body. It is a figure which shows the example (Embodiment 4) which provided the rotation join in the coupling | bond part of a workpiece | work (force transmission body) and a power receiving body.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Support body, 2 (2-1, 2-2, 2-3) ... Single-axis force sensor, 2a ... Upper end surface, 2b ... Lower end surface, 3 ... Power receiving body, 3a, 3b, 3c ... Diaphragm part, 4 ... Force transmission body (work), 4a ... Upper end surface, 4b ... Lower end surface, 5 ... Force component calculation unit, O ... Connection point (origin), P (P4) ... Power receiving point, P1, P2, P3 ... Detection Point, 6 ... hand, 7 (7-1, 7-2, 7-3) ... ball joint, 8 ... rotary joint.

Claims (5)

A force receiving body that receives a force to be detected acting on the force receiving point via a force transmitting body;
Provided between the force receiving body and the support body, the direction perpendicular to the support body is set as the Z-axis direction, and the force receiving body is within the same plane centering on the coupling point with the force transmitting body. A force sensor for detecting only the force in the Z-axis direction acting on each detection point, with each of three or more points on the circumference of the predetermined radius as detection points;
Force component calculation for obtaining force components in the X, Y, and Z axial directions of the detection target force acting on the force receiving point, which are orthogonal to each other, from a force detected by the force sensor. And a force detecting device. The force detection device according to claim 1,
Each detection point in the force receiving body is a point obtained by dividing the circumference of the predetermined radius at equal angular intervals. The force detection device according to claim 1,
The force receiving body has a diaphragm portion in which a predetermined range is thinned around the detection point for each detection point;
The force sensor is provided such that an end surface thereof is in contact with a diaphragm portion of the force receiving body. The force detection device according to claim 1,
The force receiving body includes a ball joint at each detection point,
The force sensor detects a force in the Z-axis direction acting on the detection point via the ball joint. In the force detection apparatus described in any one of Claims 1-4,
A force detection device, wherein a rotation joint is provided at a coupling portion between the force transmission body and the force receiving body.

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