JP2011080945A - Force sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor detecting a plurality of vector values. <P>SOLUTION: A force sensor 201 includes: a bearing 206 having three freedom degrees for receiving movement of a table 203; a bearing 207 having two freedom degrees for receiving movement of the bearing 206; an arm 205 which is secured to a base 202 to receive movement of the bearing 207; and a rod 204 whose one end is connected to the bearing 206 while the other end connected to the bearing 207, so that the table 203 is connected to the base 202. The force sensor 201 also includes: a detection element 208 which detects displacement and/or deformation of the arm 205; and a circuit board 210 containing a calculation part for calculating magnitude and/or direction of the force acting on the table 203 based on F=G-D, where a factor matrix G is used for converting matrix D, whose component is detection value of the detection element 208, into a vector F that represents force. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique that is effective when applied to a force sensor, particularly a six-axis force sensor.

  The force sensor is a device that detects a force (external force) acting on a traveling table (object) included in the force sensor, and is used, for example, to realize a tactile sensation of a human fingertip in a robot hand. The force sensor can simultaneously detect a total of six components including a force component in the three-axis direction of a three-dimensional space orthogonal coordinate system (x-axis, y-axis, and z-axis) and a moment component around the three axes. There is something. Thus, a force sensor that can detect six components is also called a six-axis force sensor.

  In Japanese Patent Laid-Open No. 10-274573 (Patent Document 1), a top plate and a bottom plate are connected by a plurality of rods, and these plates are connected to each other by a joint having two degrees of freedom on one end and three degrees of freedom on the other side. A force sensor using a joint is disclosed. The rod of the force sensor is provided with a detection element capable of detecting the compression / tensile force in the rod axis direction.

  Further, a force sensor (structure deformation mode) for detecting a force by deforming a structure is disclosed in Japanese Patent Laid-Open No. 9-318469 (Patent Document 2). For example, a six-axis force sensor combining a strain gauge and an elastic body is widely used in applications such as external force measurement in a robot that performs force control. When force or moment acts on the elastic body to which the strain gauge is attached and the elastic body is deformed, stress is generated in each strain gauge accordingly. The resulting change in the electrical resistance value of each strain gauge is output as a voltage value via a well-known bridge circuit, and further converted into a six-axis force by a predetermined calculation processing circuit or software processing.

  Japanese Patent Laid-Open No. 5-149811 (Patent Document 3) discloses triaxial forces orthogonal to each other by a plurality of strain gauges affixed to an optimal site set by FEM analysis of a flat plate-like strain generating body. A six-axis force sensor is disclosed that includes a strain detection circuit including a plurality of bridge circuits that independently detect moments about an axis.

  Japanese Patent Application Laid-Open No. 9-131690 (Patent Document 4) discloses a six-axis load detection device that controls the position and posture of a predetermined movable plate by cooperation of a plurality of actuators. A six-axis load acting on a predetermined point on a predetermined movable plate is detected by holding the movable plate at a predetermined position and posture by the cooperative operation of a plurality of actuators.

  Japanese Patent Laid-Open No. 2000-148382 (Patent Document 5) discloses that a force sense presentation mechanism for presenting and transmitting a force sense to a user wears an operating device for connecting the user and the operating device. Haptic interface having 6-axis force feedback, including 6 motion sets, 6 link sets supporting the motion platforms, 6 drive units for independently driving each link set, and 6 position sensors An apparatus is disclosed.

  Incidentally, the acceleration sensor is a device that detects the acceleration of an object having mass, and is used, for example, for posture control of a robot or detection of a collision of an automobile airbag. An angular velocity sensor (for example, a gyro sensor) is a device that detects an angular velocity at which an object having a mass rotates, and is used, for example, for industrial robots or detection of a rollover of an automobile. These acceleration sensors and angular velocity sensors are devices (motion sensors) that detect an inertial force generated from the movement of an object with respect to a force sensor that detects a force (external force) applied to the object.

  In order to detect the triaxial acceleration in the x-axis, y-axis, and z-axis directions, for example, when a uniaxial acceleration sensor is used, it is necessary to arrange three uniaxial acceleration sensors in directions orthogonal to each other. In order to detect the triaxial angular velocities in the rotation directions of the x axis, the y axis, and the z axis, for example, three uniaxial angular velocity sensors are required. For this reason, a 6-axis motion sensor that simultaneously detects 3-axis acceleration and 3-axis angular velocity is desired.

  In the present application, a motion sensor will be described as a superordinate concept of an acceleration sensor and an angular velocity sensor. That is, the motion sensor can detect acceleration and / or angular velocity.

JP-A-10-274573 JP 9-318469 A Japanese Patent Laid-Open No. 5-149811 JP-A-9-131690 JP 2000-148382 A

  For example, in order to obtain a tactile sensation similar to that of a human finger, research and development have been carried out in which a force sensor is provided at the fingertip of a robot in the medical field or daily life field. Such force sensors are required to be small and highly accurate. In addition, motion sensors such as acceleration sensors and angular velocity sensors are also required to be downsized and highly accurate because they are provided in industrial robots and consumer equipment.

  By the way, the force, acceleration, and angular velocity related to the object are vector quantities, and the force sensor that detects the force received by the object and the motion sensor that detects the movement of the object from the force as acceleration and angular velocity detect the vector quantity. It is thought that the structure to be made can be made common. Therefore, if a novel structure capable of simultaneously detecting many vector quantities is used, it becomes possible to obtain a force sensor and a motion sensor corresponding to downsizing and high accuracy.

  An object of the present invention is to provide a force sensor that detects a plurality of vector quantities. The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

から前記テーブルもしくは前記ベースに作用する力の大きさおよび／または方向を計算する演算部と、を備えている。 A force having a base, a table having six degrees of freedom with respect to the base, and arranged in opposition to the base, and six connecting portions arranged in parallel to connect the table and the base It is a sense sensor, and the connecting portion is fixed to the base, a first bearing having three degrees of freedom for receiving the movement of the table, a second bearing having two degrees of freedom for receiving the movement of the first bearing, and the base. An arm that receives the movement of the second bearing, and connects the table and the base, and the base and the arm are integrally molded so as to have a gimbal structure having a spring property, Using a detection element that detects the displacement and / or deformation of the arm, and a coefficient matrix G for converting from a matrix D having the detection value of the detection element as a component to a vector F indicating a force,

And a calculation unit for calculating the magnitude and / or direction of the force acting on the table or the base.

  The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described. A force sensor that detects a plurality of vector quantities can be provided.

It is a top view which shows typically the sensor in one embodiment of this invention. It is a side view which shows the sensor of FIG. 1 typically. It is a block diagram of the circuit which the sensor of FIG. 1 has. It is principal part sectional drawing which shows typically the sensor in other embodiment of this invention. It is a figure for demonstrating the principle of the magnetic identification element of FIG. It is a principal part top view which shows typically the sensor in other embodiment of this invention. It is principal part sectional drawing which shows typically the sensor in the XX line of FIG. It is a top view which shows typically the sensor in other embodiment of this invention. FIG. 9 is a top view schematically showing the sensor of FIG. 8 excluding a table. It is sectional drawing which shows typically the sensor in the YY line | wire of FIG. It is explanatory drawing for detecting a force. It is a side view which shows typically the sensor in other embodiment of this invention. It is a top view which shows typically the sensor in other embodiment of this invention. FIG. 14 is a top view schematically showing the sensor of FIG. 13 excluding a table. It is sectional drawing which shows the sensor of FIG. 13 typically. It is a flowchart of the iterative process which the sensor of FIG. 13 performs. It is a table | surface which shows the sensor output characteristic by measurement data.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof may be omitted.

  First, the force sensor and motion sensor (Japanese Patent Application No. 2009-59679) developed by the present inventors and filed a patent application will be described in Embodiments 1 to 6, and the arithmetic units provided in these sensors in Embodiment 7 The processing function will be described. The patent application for force sensor and motion sensor (Japanese Patent Application No. 2009-59679) is a technology that has not been disclosed at the time of filing of the present application, and will be described as an invention according to the present application.

(Embodiment 1)
In the present embodiment, a case will be described in which the present invention is applied to a force sensor as a sensor having a novel structure capable of detecting a vector quantity. As shown in FIGS. 8 to 10, the sensor 101 (force sensor 101) in the present embodiment has a base 102 and six degrees of freedom with respect to the base 102, and is arranged to face the base 102. A traveling table (hereinafter simply referred to as a table) 103 and six connecting portions 104 arranged in parallel for connecting the table 103 and the base 102 are provided. This force sensor 101 has three degrees of force components Fx, Fy, and Fz in a three-dimensional space orthogonal coordinate system (x-axis, y-axis, and z-axis), and the three axes around the three axes, based on six degrees of freedom of the table 103 Can be detected as a total of six components of moment components Mx, My and Mz.

  The connecting portion 104 includes a bearing 106 having three degrees of freedom for receiving the movement of the table 103, a bearing 107 having two degrees of freedom for receiving the movement of the bearing 106, and an arm 105 fixed to the base 102 and receiving the movement of the bearing 107. The table 103 and the base 102 are connected. The bearings 106 and 107 are spherical bearings that can hold, for example, a steel ball as a spherical surface and can move with three or two degrees of freedom.

  In the present embodiment, the bearing 106 and the bearing 107 are directly connected to each other by an angle of the ball of each bearing, for example, by welding. That is, since the bearings 106 and 107 are physically large, they are directly connected at an angle. Theoretically, the centers of the upper and lower bearings 106 and 107 may be connected with a certain distance and angle, and force may be transmitted to the arm 105. Therefore, the distance between the base 102 and the table 103 can be determined by the bearings 106 and 107, and the force sensor 101 can be thinned.

  As described above, when the distance between the base 102 and the table 103 is short, it is difficult to secure an arm length between the base 102 and the table 103. In this embodiment, the arm 105 is attached to the base 102. It extends in a plane parallel to the plane.

  The structure in which the table 103 is supported by the plurality of connecting portions 104 in this way is a parallel link structure. In the present embodiment, six connecting portions 104 are arranged in order to move the table 103 in all directions (six axis directions). If a point on the plane of the table 103 is to be moved, a minimum of two connecting portions 104 are necessary.

  Here, the bearing 106 has three degrees of freedom and the bearing 107 has two degrees of freedom will be described. Consider a case where the arm 105 and the table 103 are connected not by the connecting portion 104 (bearings 106 and 107, arm 105) but only by a rigid rod. In this case, if the table 103 is moved in all directions, for example, Mz, the rod is still twisted while falling in the rotational direction. When one point of the rod is viewed from the table 103, the tilting of the rod in the rotational direction occurs when the table 103 moves in the plane direction. Two degrees of freedom are required to release the tilt of the rod in the rotational direction, and one degree of freedom is required to release the twist of the rod. Further, when one point of the rod is seen from the arm 105, the twist of the rod has already been released, so that the degree of freedom in the rotation direction of the rod is taken into consideration, so that there are two degrees of freedom.

  Therefore, in the present embodiment, the bearing 106 connected to the table 103 has three degrees of freedom, and the bearing 107 connected to the arm 105 has two degrees of freedom.

  The table 103 has a circular flat plate and is a rigid body made of a metal such as stainless steel (for example, SUS304) excellent in corrosiveness and workability. On the outer peripheral side of the table 103, six holes 103a penetrating the flat plate are formed. A bearing 106, which is a spherical bearing, is directly connected so as to fit into the hole 103a.

  The base 102 has a circular flat plate, and is a rigid body made of a metal such as stainless steel (for example, SUS304) excellent in corrosiveness and workability. A protrusion is formed at the center of the base 102, and six arms 105 extending from the protrusion to the outer periphery of the base 102 in a branch shape are formed. Each arm 105 is made of a metal such as stainless steel (for example, SUS304) excellent in corrosiveness and workability when formed integrally with the base 102, but is formed so as to extend in a branch shape. The elastic body has a sufficiently large change amount with respect to the change amount of the base 102.

  Thus, each arm 105 extends in a branch shape in parallel with the plane of the base 102. Each arm 105 is formed of a hollow body at the tip, and has a hole 105a that communicates with the hollow body. A bearing 107, which is a spherical bearing, is directly connected so as to fit into the hole 105a. As described above, the bearing 107 is directly connected to the bearing 106 at an angle, for example, by welding.

  In addition, the force sensor 101 includes a capacitance element 108 as a detection element that detects displacement and / or deformation of the arm 105 that is an elastic body. The capacitance element 108 is disposed below the tip of the arm 105 and on the base 102. Specifically, a pair of electrodes are disposed on the base 102 side and the arm side 105. Become. The change in capacitance between the pair of electrodes is detected as the displacement and / or deformation of the arm 105.

  In addition, the force sensor 101 includes a circuit board 110 having a calculation unit (for example, a CPU) that calculates the magnitude and / or direction of the force acting on the table 103 from the detection value of the capacitance element 108. The circuit board 110 is disposed on a plane facing the table 103 in the base 102.

  In this circuit board 110, a signal (analog signal) from the electrostatic capacitance element 108 (detection element SD) that has detected the displacement and / or deformation of the arm 105 is amplified by the amplifier 11 with the circuit configuration shown in FIG. After that, the analog signal is converted into a digital signal by the A / D converter 12, and the force (load) applied to the table 103 by the CPU 13 is calculated using a constant from the memory 14. That is, the CPU 13 serving as a calculation unit calculates the magnitude and / or direction of the force acting on the table 103 from the detection value detected by the capacitance element 108 (detection element SD).

  This calculation result is output as digital output from the CPU 13 and as analog output using the D / A converter 15. In order to calculate the load applied to the table 103 from the displacement and / or deformation of the arm 105, for example, a constant obtained by calculation or actual measurement is required. Based on this constant, six-axis force components Fx, Fy, Fz applied to the table 103 via the CPU 13 based on the detection values from the capacitance elements 108 (detection elements SD) provided on the six arms 105, respectively. , Mx, My, and Mz can be detected simultaneously.

  In the present embodiment, the table 103 receives a load, but the base 102 may receive a force (load). In this case, the CPU 13 included in the circuit board 110 calculates the magnitude and / or direction of the force acting on the base 102 from the detection value of the capacitance element 108.

  A case where a force component Fz in the vertical direction is added to the table 103 of the force sensor 101 will be described in order. First, the table 103 tries to move in the −Z direction by force (Fz). Since a bearing with three degrees of freedom is connected to the table 103 and a bearing with two degrees of freedom is connected to the bearing, a force (Fz / 6) is applied in the axial direction of the bearing. That is, the force (Fz / 6) is synthesized by the mounting angle of the table 103 and the bearing 106 to obtain the force (Fz).

  Next, since the bearing 106 and the tip of the arm 105 are connected by a bearing 107 having two degrees of freedom, and the other end of the arm 105 and the base 102 are fixed, a force (Fz / 6) is applied to the arm 105, and the arm 105 Deforms in one direction (planar deformation). Thus, in order to generate a force accurately on the arm 105 that is an elastic body, the bearing 106 and the bearing 107 have no sliding resistance, and the base 102 and the table 103 must be rigid bodies.

  In this way, the magnitude and / or direction of the force applied to the table 103 can be replaced with the simplest plane deformation in the arm 105, so that a highly accurate force can be detected.

  Here, in the force sensor 101 according to the present embodiment, the magnitude / or direction of the force acting on the table 103 can be detected even when the bearing 106 and the bearing 107 are directly connected. A description will be given with reference to a truss structure in which the nodes of the members shown in FIG. The bearing 106 is replaced with a bearing B1, and the bearing 107 is replaced with bearings B2 and B3.

  In FIG. 11, bearings B1, B2, and B3 are arranged at each vertex of the triangle. The bearing B1 and the bearing B2 are connected by a rod R1, and the bearing B1 and the bearing B3 are connected by a rod R2. For example, when a force Fz is applied to the bearing B1 and balanced, only the axial forces T1 and T2 act on the rods R1 and R2, the reaction force T1 on the bearing B2, and the reaction force T2 on the bearing B3. Power works. The magnitudes of these forces T1 and T2 are determined by the following equations.

T1 = Fz / sin θ ₁
T2 = Fz / sin θ ₂

From this, it can be seen that the forces T1 and T2 depend only on the respective θ ₁ and θ ₂ and are not affected by the rod length. Therefore, the force sensor 101 according to the present embodiment can detect the force acting on the table 103 even if the bearing 106 and the bearing 107 are directly connected and arranged with an angle without providing a rod. Can do. Thus, the force sensor 101 in which the bearing 106 and the bearing 107 are directly connected without providing a rod can be reduced in thickness and size.

  In the parallel link structure of the force sensor 101, when the table 103 is to be moved, a plurality of shafts (rods) are connected to the table 103, and the arm 105 is driven by changing the angle. Bearings 106 and 107 that allow the rotation of the table 103 to escape are necessary at both ends of the shaft. In this embodiment, the bearings 106 and 107 are also used as shafts (rods).

  The rigidity of the force sensor 101 is the amount of movement of the table 103, and is an amount by which the force sensor 101 is deformed when a force is applied to the table 103. In the present embodiment, the base 102, the table 103, and the bearings 106 and 107 are rigid bodies, and the arm 105 is an elastic body having a predetermined spring coefficient. For this reason, the amount of movement of the table 102 is determined by the amount of deformation of the arm 105. Although the influence on the rigidity of the force sensor 101 is smaller than the amount of deformation of the arm 105, the attachment angle between the bearings 106 and 107 and the length of the shaft (rod) are also affected.

  In a force sensor (structural deformation mode) in which a structure is deformed and the deformation is detected by a detection element (for example, a strain gauge), when a rated load of 250 N is applied and the deformation is 25 μm, the contacted object is a rigid body As a result, in order to perform 10N control, position control of 1 μm must be performed. This makes accurate force control difficult.

  Also, consider a case where force is detected by a force output structure such as a force sense interface device having force feedback as described in Patent Document 5, for example. In this structure, the amount of movement of the actuator is fed back to the driving means by the force applied to the table and is balanced with the force applied by returning the table to a predetermined position, so that the table cannot be moved.

  Therefore, in the present embodiment, the rigidity of the force sensor 101 can be easily changed by using the arm 105 as an elastic body and changing its displacement. That is, it is possible to detect a gentle force (fine force) with high accuracy (resolution).

(Embodiment 2)
In the first embodiment, the sensor that can be reduced in thickness and size by directly connecting a bearing having three degrees of freedom and a bearing having two degrees of freedom has been described. Thus, in the structure in which the bearings are directly connected, the movable range of the table that receives the force is small. Therefore, in the present embodiment, a gentle force detection with higher accuracy can be performed by providing a rod between a bearing having three degrees of freedom and a bearing having two degrees of freedom to widen the movable range of the table. A sensor capable of performing the above will be described. The sensor for detecting a plurality of vector amounts is the same as that of the first embodiment except for the difference in structure due to the provision of a rod.

  In the present embodiment, a case will be described in which the present invention is applied to a force sensor as a sensor having a novel structure capable of detecting a vector quantity. As shown in FIGS. 1 and 2, the sensor 1 (force sensor 1) in the present embodiment has a base 2 and six degrees of freedom with respect to the base 2, and is arranged to face the base 2. A traveling table (hereinafter simply referred to as a table) 3 and six connecting portions arranged in parallel for connecting the table 3 and the base 2 are provided.

  The connecting portion includes a bearing 6 having three degrees of freedom for receiving the movement of the table 3, a bearing 7 having two degrees of freedom for receiving the movement of the bearing 6, and an arm 5 fixed to the base 2 and receiving the movement of the bearing 7. The table 3 and the base 2 are coupled to each other including the rod 4 having one end connected to the bearing 6 and the other end connected to the bearing 7.

  As described in the first embodiment, the force sensor 1 in the present embodiment does not affect the length of the rod 4 when detecting the force applied to the table 3. That is, although the force sensor 1 provided with the rod 4 is shown in the present embodiment, it is theoretically the same as the force sensor 101 shown in the first embodiment.

  As described above, the force sensor 1 according to the present embodiment includes the rod-shaped rod 4 and the arm 5 that connect the base 2 and the table 3 to the connecting portion. The structure for supporting the table 3 by a plurality of connecting portions is a parallel link structure. In addition, the base 2 and the table 3 are formed in a flat plate as shown in the figure, for example, and are arranged in parallel to each other.

  The force sensor 1 determines the magnitude and / or direction of the force (load) acting on the table 3 according to the three-axis direction force component Fx in the three-dimensional space orthogonal coordinate system (x axis, y axis, z axis), It can be detected as a total of six components including Fy and Fz and moment components Mx, My and Mz around the three axes. In the present embodiment, the table 3 receives a load, but the base 2 may receive a load.

  The force sensor 1 includes one rod 4 and one arm 5 to form one connecting member, and connects the base 2 and the table 3. Six connecting members are provided along the circumferential direction of the table 3, and two connecting members are provided side by side. That is, six rods 4 are provided along the periphery of the table 3, and two rods 4 are arranged in parallel. As a result, the magnitude and / or direction of the force (load) acting on the table 3 is simultaneously determined as a total of six components including the force component in the three-axis direction of the orthogonal coordinate system in the three-dimensional space and the moment component around the three axes. Can be detected.

  Each material of the base 2, the table 3, the rod 4, the bearing 6, and the bearing 7 is a rigid body that can withstand a rated load applied to the table 3, and the arm 5 is an elastic body. For example, the base 2, the table 3, and the rod 4 are rigid bodies made of a metal such as stainless steel (for example, SUS304) excellent in corrosiveness and workability. The arm 5 is an elastic body made of a metal such as phosphor bronze that is generally used as a spring material. In addition, if the load to the table 3 is a low load of 10 N or less, it can also be comprised with resin (polyacetal etc.) instead of a metal.

  As described above, the base 2, the table 3, and the rod 4 are assumed to be rigid bodies. However, the base 2, the table 3, and the rod 4 only need to have rigidity that does not affect the measurement load accuracy, that is, the deformation amount is sufficient with respect to the deformation amount of the arm 5. It only needs to be small. The arm 5 may be a load range in which plastic deformation does not occur by determining the spring coefficient by thinning and thinning the portion to be deformed. In the fourth embodiment to be described later, a case will be described in which the arm 5 is formed of a magnetic material within a load range in which plastic deformation does not occur.

  One end of the table 3 and the rod 4 is connected by a bearing 6 having three degrees of freedom, and the other end of the rod 4 and one end of the arm 5 are connected by a bearing 7 having two degrees of freedom. The other end and the base 2 are fixed.

  In the present embodiment, the other end of the arm 5 and the base 2 are fixed via the arm mounting base 9, but the other end of the arm 5 and the base 2 may be directly fixed. For example, welding, bolting, and the base 2 and the arm 5 can be integrally formed. The integral molding of the rigid base 2 and the elastic arm 5 is such that if the portion that becomes the arm 5 is made thinner than the thickness of the base 2, that portion can have elasticity within a specific load. Molded by integration during production.

  A case where a force component Fz in the vertical direction is added to the table 3 of the force sensor 1 will be described in order. First, the table 3 tries to move in the −Z direction by force (Fz). Since the table 3 and one end of the rod 4 are connected by a bearing 6 having three degrees of freedom, and the other end of the rod 4 and one end of the arm 5 are connected by a bearing 7 having two degrees of freedom, the shaft of each of the six rods 4 A force (Fz / 6) is applied in the direction. That is, the force (Fz / 6) is synthesized by the mounting angle of the table 3 and the rod 4 to obtain the force (Fz).

  Next, since the other end of the rod 4 and one end of the arm 5 are connected by a bearing 7 having two degrees of freedom, and the other end of the arm 5 and the base 2 are fixed, force is applied from the rod 4 to the arm 5 connected thereto. (Fz / 6) is added, and the arm 5 is deformed in one direction (planar deformation).

  Here, in order to generate a force accurately on the arm 5, the bearing 6 connecting the table 3 and the rod 4 and the bearing 7 connecting the rod 4 and the arm 5 have no sliding resistance, and the table 3, The rod 4 must be rigid. Therefore, one end side of the rod 4 and the table 3 are connected by a bearing 6 having three degrees of freedom, and the other end side of the rod 4 and the base 2 are connected by a bearing 7 having two degrees of freedom.

  In this way, the rod 4 is a rigid body and the arm 5 is provided as a target for detecting displacement and / or deformation, whereby the magnitude and / or direction of the force applied to the table 3 is replaced with the simplest planar deformation in the arm 5. be able to. Thereby, as in the technique of Patent Document 1, for example, higher performance can be achieved than a force sensor in which a strain gauge is provided on a rod.

  The force sensor 1 has a circuit board 10, and as shown in FIG. 2, the circuit board 10 is provided on the surface (back surface) opposite to the surface facing the table 3 in the base 2. In the circuit board 10, a signal (analog signal) from the strain gauge 8 (detection element SD) that detects the displacement and / or deformation of the arm 5 is amplified by an amplifier 11 with the circuit configuration as shown in FIG. The analog signal is converted into a digital signal by the A / D converter 12, and the load applied to the table 3 by the CPU 13 is calculated using constants from the memory 14. In other words, the CPU 13 as the calculation unit calculates the magnitude and / or direction of the force acting on the table 3 from the detection value detected by the strain gauge 8.

  This calculation result is output as digital output from the CPU 13 and as analog output using the D / A converter 15. In order to calculate the load applied to the table 3 from the displacement and / or deformation of the arm 5, for example, a constant obtained by calculation or actual measurement is required.

  By detecting the strain gauges 8 provided on each of the six arms 5, the six-axis force components Fx, Fy, Fz, Mx, My, and Mz applied to the table 3 via the CPU 13 can be detected simultaneously. By providing the strain gauge 8 at a position where the largest distortion occurs in the arm 5, it is possible to accurately detect six-axis forces. 1 and 2 show the case where the strain gauge 8 provided on the arm 5 is provided on the surface side facing the table 3, it may be provided on the surface side facing the base 2.

  Here, a force sensor using the technique (conventional technique) of Patent Document 1 will be described in correspondence with the terms of the present embodiment. A force sensor using a conventional technique is a force sensor in which one end of a table and a rod are connected by a bearing with two degrees of freedom, and the other end of the rod and a base are connected by a bearing with three degrees of freedom. Is provided on the rod. That is, the compressive / tensile force in the axial direction of the rod is detected. For this reason, the force sensor of the prior art does not detect the displacement and / or deformation of the arm.

  Theoretically, only the axial compressive / tensile force is applied to the rod of the force sensor of the prior art. However, in reality, if the rod is not a rigid body, it is a design that takes into account deformation (buckling) other than the axial direction, that is, the contradictory conditions of having elasticity in the axial direction and rigidity in the axial diameter direction. If the force sensor is downsized, the design becomes more difficult. That is, the conventional force sensor in which the rod is provided with a detection element cannot accurately detect the load applied to the table.

  On the other hand, in the present embodiment, the rod 4 is a rigid body and provided with an arm 5 that detects displacement and / or deformation, so that the rod 4 is compressed and tensioned as a position detection of the base 2 side end. The force can be replaced with the simplest plane deformation. For example, even when the force sensor 1 is downsized, the load applied to the table 3 can be detected with high accuracy. That is, force components Fx, Fy, Fz, Mx, My, and Mz applied to the table 3 from all six directions can be detected on a plane. In other words, even the six-direction force component applied to the table 3 can be performed completely the same as the detection when a single-direction force is applied.

  As described above, the force sensor 1 according to the present embodiment is a device having a novel structure capable of detecting a plurality of forces (vector quantities). This new structure will be described below.

  Unlike the force sensor 1 of the present embodiment, in a force sensor (structural deformation mode) in which the structure is deformed and detected, as long as the structure has a certain size, for example, the force of the force sensor is used. When a force component Fz in the z-axis direction is applied to a position to be added (hereinafter referred to as a table), force components Fx and Fy are also generated in the x-axis and y-axis directions (other-axis sensitivity). In addition, it is extremely difficult to deal with output characteristics and the like that are applied with the moment of the z-axis, and an unavoidable problem arises. Further, it becomes difficult to apply forces from six directions to a specific place.

  In addition, when considering miniaturization, it is possible to reduce the size of the table in a structure such as a force sensor. However, if the size of the table changes, the design of the structure itself where the force is applied from the table has been revised. There must be. In addition, in a structure such as a force sensor, for example, when a combined force is applied such as when the force component Mz is added to the table and then the force component Fz is applied, it is difficult to detect the force component Fz characteristic. Even if it can be detected, the manufacture of the force sensor is difficult and expensive.

  However, in the present embodiment, it is only necessary to detect a unidirectional force applied to the arm 5, so even if the table 3 of the force sensor 1 is made smaller, the arm 5 that is the sensing part can also be made smaller. . That is, even when the force sensor 1 is downsized, it can be detected with high accuracy.

  Further, the force sensor 1 in the present embodiment can take out the wiring from the strain gauge 8 from an arbitrary position as compared with a structure such as a force sensor. Thereby, for example, even when the force sensor 1 is sized to be installed on the arm of the robot, the wiring can be passed through the centers of the base 2 and the table 3.

  Also, in the structure such as a force sensor, the pursuit of high accuracy, low cost, and downsizing is largely due to the examination of the bearing structure. In the force sensor 1 according to the present embodiment, since the rod 4 is a rigid body, it is easier to design and analyze the structural deformation mode.

  The force sensor 1 according to the present embodiment includes one rod 4 and one arm 5 to form one connecting member (link), and the base is formed by six (plural) connecting members (links). 2 and the table 3 are connected. For this reason, the force sensor 1 can realize high rigidity and high speed driving by making the six links have a closed link structure.

(Embodiment 3)
In the present embodiment, a case where a linear actuator is provided on the rod in the second embodiment will be described. In addition, the description which overlaps with the said Embodiment 2 may be abbreviate | omitted.

  As shown in FIG. 12, in the sensor 1a (force sensor 1a) in the present embodiment, the rod 4 has a linear actuator 4a that can expand and contract in the axial direction. The linear actuator 4a is made of, for example, a servo motor, a cylinder, a shape memory alloy, an artificial muscle, and the like, and can extend and contract the entire length of the rod 4 in the axial direction. Therefore, by providing the linear actuator 4a in the rod 4, the surface of the table 3 can be moved freely.

  As described in the first embodiment, the force sensor 1a does not affect the length of the rod 4 in detecting the force applied to the table 3. That is, in the present embodiment, the force sensor 1a provided with the rod 4 capable of extending and contracting the entire length in the axial direction is shown. Theoretically, the force sensor 1a is the same as the force sensor 101 shown in the first embodiment. is there. However, when detecting the force of the table 3, the rod 4 must be rigid. That is, even if the length of the rod 4 itself changes, only the direction of the table 3 changes, and the rod 4 does not expand or contract in the axial direction by the force applied to the table 3.

  In the force sensor 1a, by providing the linear actuator 4a in the rod 4, it is possible to detect the force applied to the table 3 moved by the expansion and contraction of the linear actuator 4a. As described in the first embodiment, since the length of the rod 4 does not affect the detection of the force acting on the table 3, the table 3 is moved by the expansion and contraction of the rod 4, and the force detection is performed by the arm 5. Because it can be done.

  For example, in the case of a robot arm having an elbow to a wrist, the base 2 on the elbow side, the table 3 on the wrist side, and the rod 4 having the linear actuator 4a from the elbow to the wrist can be configured. Thereby, the force applied to the wrist can be detected while moving.

(Embodiment 4)
In the second embodiment, the case where the displacement and / or deformation of the arm is detected by a strain gauge (detection element) has been described. However, in the present embodiment, the displacement and / or deformation of the arm is detected by a magnetic identification element (detection element). ) Will be described. In addition, the description which overlaps with the said Embodiment 2 may be abbreviate | omitted.

  As shown in FIG. 4, the magnetic identification element 20 is embedded (provided) on one end side of the arm 5 and in the base 2 below it. FIG. 4 is a cross-sectional view schematically showing the main part of the force sensor according to the present embodiment. Only part of the force sensor is hatched for easy explanation.

  The magnetic discriminating element 20 is composed of two magnetoresistive elements 20a and a magnet 20b. As shown in FIG. 5, a power supply voltage (Vcc) is applied to a reference potential (GND) in advance. The change of the magnetic flux applied to the magnetoresistive element 20a is detected as the output voltage (Vout). Here, the resistance value of the magnetoresistive element 20a changes in proportion to the strength of the magnetic field.

  The arm 5 may be made of any material that can withstand the rated load applied to the table 3, but in the present embodiment, the arm 5 is made of a magnetic material. If two elements are placed in a static magnetic field, and the magnetic material moves, the magnetic field changes and the resistance balance is lost. For this reason, when the arm 5, which is a magnetic body, is displaced (indicated by reference symbol A), the magnetic flux applied to the magnetoresistive element 20 a changes, so that the output voltage (Vout) is detected as the displacement and / or deformation of the arm 5. be able to.

  In the present embodiment, the magnetic identification element 20 is provided on the base 2 under one end of the arm 5 connected to the other end of the rod 4. Since the other end side of the arm 5 is fixed to the base 2, one end (front end) of the arm 5 is displaced most by the force applied to the arm 5. It is provided on the lower base 2.

  Further, as shown in FIG. 4, one end of the arm 5 moves up and down, so that when the table 3 is overloaded, the arm 5 may come into contact with the base 2 (magnetic identification element 20). In order to prevent this, in the present embodiment, a stopper 21 is provided on a surface on one end side of the arm 5 and facing the base 2. The above-described structure such as a force sensor is difficult because there is no degree of freedom of design change. However, the force sensor according to the present embodiment only needs to catch deformation in one direction of the arm 5, so the arm 5 However, a stopper structure against overload may be provided.

  By providing the rod 4 as a rigid body and the arm 5 as a target for detecting displacement and / or deformation in this way, the compression / tensile force of the rod 4 can be replaced with the simplest plane deformation. Can be detected with high performance even if it is provided on the base 2 below one end of the arm 5.

(Embodiment 5)
In the second embodiment, the case where the displacement and / or deformation of the arm is detected by a strain gauge (detection element) has been described. In the present embodiment, the arm and the base are integrally molded using a gimbal structure, A case where the displacement and / or deformation of the arm (gimbal) is detected by a capacitance element (detection element) will be described. In addition, the description which overlaps with the said Embodiment 2 may be abbreviate | omitted.

  As shown in FIGS. 6 and 7, in this embodiment, a gimbal 5a, which is an arm, is integrally formed with the base 2a as a gimbal structure. In order to explain the integral molding, in the plan view of FIG. 6 and the cross-sectional view of FIG. 7, the gimbal 5a and the base 2a are given the same hatching.

  In the present embodiment, a gimbal structure is adopted for each of the six rods 4 (see FIGS. 1 and 2) provided along the circumferential direction of the table 3. In FIGS. 6 and 7, it is shown corresponding to one rod 4. One end of the rod 4 is connected to the table 3 (see FIG. 2), and the other end of the rod 4 is connected to the gimbal 5a by a two-degree-of-freedom bearing 7a (see FIG. 7).

  The gimbal 5a is provided with a capacitance element 30 including two opposing plate-like electrodes 30a and 30b. The electrostatic capacitance element 30 is a detection element that detects displacement and / or deformation of the gimbal 5a by a change in electrostatic capacitance. In the present embodiment, one electrode 30 a of the capacitive element 30 is provided on the gimbal 5 a through the connection portion 31. The other electrode 30b of the capacitive element 30 is provided on a circuit board 10 that is fixed to a surface opposite to the surface facing the table 3 in the base 2a. That is, the other electrode 30b of the capacitive element 30 is provided on the base 2a. The change in capacitance of the capacitive element 30 can be converted into the vertical displacement of the gimbal 5a (for example, indicated by the symbol A in FIG. 7).

  Also in the force sensor in the present embodiment, the magnitude and / or direction of the force acting on the table 3 is detected by the displacement and / or deformation of the gimbal 5a which is an arm, as in the second embodiment. . Here, in the present embodiment, the electrode 30a constituting the capacitive element 30 is provided at the other end of the rod 4 which is a rigid body, but when the gimbal 5a (arm) which is an elastic body is displaced, The position of the electrode 30a is displaced together with the other end of the rod 4, and the capacitance of the capacitance element 30 changes. That is, the change in the capacitance of the capacitance element 30 can be regarded as the displacement of the gimbal 5a and converted as the magnitude and / or direction of the force acting on the table 3. The signal (detected value) of the capacitive element 30 (detection element SD) that detects the displacement and / or deformation of the gimbal 5a is sent to the circuit board 10 and processed by the circuit configuration as shown in FIG. The

  In the present embodiment, the capacitive element 30 is configured by providing the electrode 30a on the gimbal 5a via the connecting portion 31 and providing the electrode 30b at a position facing the electrode 30a. Not only this but the electrode 30a may be provided in the gimbal 5a of the surface side which opposes the electrode 30b instead of via the connection part 31. FIG. As described above, it is only necessary that the change in the capacitance of the capacitance element 30 can be regarded as the displacement and / or deformation of the gimbal 5a and converted into the magnitude and / or direction of the force acting on the table 3. It is.

  Thus, by providing the rod 4 as a rigid body and providing an elastic gimbal 5a (arm) as a target for detecting displacement and / or deformation, the compression / tensile force of the rod 4 can be replaced with the simplest plane deformation. Therefore, the force sensor in the present embodiment can detect a load applied to the table 3 with high performance.

  In this embodiment, the arm is integrally formed with the base 2a as the gimbal 5a, so that the rod-like arm 5 as shown in the second embodiment extends in the height direction from the base 2 to the table 3. Not done. In other words, the gimbal 5a serving as an arm extends in the plane direction of the base 2a. For this reason, the height of the arm 5 as shown in the second embodiment can be cut, and the force sensor can be further downsized.

(Embodiment 6)
In the first to fifth embodiments, the case where the sensor is applied to a force sensor is described as a sensor having a novel structure capable of detecting a vector quantity. In the present embodiment, a case where the sensor is applied to a motion sensor will be described. In addition, the description which overlaps with the said Embodiment 1-5 may be abbreviate | omitted.

  The force sensor is a device that detects an external force received by an object, and the motion sensor is a device that detects acceleration and angular velocity from the inertial force received by the object, and both detect force (external force, inertial force). For this reason, also in the motion sensor in this Embodiment, the novel structure which detects the force demonstrated in the said Embodiment 1-5 can be used in common.

  For example, referring to FIG. 1 and FIG. 2, the sensor 1 (motion sensor 1) in the present embodiment has the following structure. First, a base 2, a table 3 disposed to face the base 2, and a rod 4 and an arm 5 that connect the base 2 and the table 3 are provided. One end of the table 3 and the rod 4 is connected by a bearing 6 having 3 degrees of freedom, and the other end of the rod 4 and one end of the arm 5 are connected by a bearing 7 having 2 degrees of freedom. The end and the base 2 are fixed. Further, the motion sensor 1 includes a strain gauge 8 (detection) that detects the magnitude and / or direction of the inertial force received by the movable part (the table 3, the rod 4, and the bearings 6 and 7) by the displacement and / or deformation of the arm 5. Element) and a CPU 13 (see FIG. 3) which is a calculation unit for calculating the magnitude and / or direction of the inertial force received by the movable part from the detected value of the strain gauge 8.

It will be described for detecting such by the motion sensor 1 z-axis direction of the acceleration a _z (calculated). For example, when the motion sensor 1 is placed on the fixed horizontal base on the base 2 side, the sensor 1 receives gravitational acceleration. At this time, in the motion sensor 1, the mass of the table 3, the rod 4, and the bearings 6, 7 is associated with each arm 5, and all the arms 5 are displaced by the same amount in the direction approaching the base 2 and / or. Deform (plane deformation). Since the displacement amount is the z-axis direction force Fz, the motion equation m · a z ₌ Fz, the acceleration a _z in the z axis direction can be detected (calculated). The calculation of the acceleration _az can be performed by, for example, the CPU 13 shown in FIG. Here, m in the equation of motion is the mass of the movable part (table 3, rod 4, and bearings 6, 7).

A case where the motion sensor 1 detects (calculates) the angular velocity ωz in the _z- axis direction will be described. When the motion sensor 1 is attached to the center of the rotary table placed in the horizontal direction on the base 2 side and rotational motion is given to the rotary table, twisting occurs between the base 2 and the table 3 at the start of rotation. At this time, in the two adjacent arms 5, a displacement in a direction approaching the base 2 appears in one arm 5, and a displacement and / or deformation (plane deformation) in a direction away from the base 2 appears in the other arm 5. The moment Mz of the force around the z axis can be detected.

Since the relationship of I · a _z = Mz is established between the force moment Mz and the moment of inertia I, the angular acceleration a _z can be calculated. Therefore, the angular velocity ω _z can be obtained by calculating and integrating the angular acceleration a _z every minute time. The calculation of the angular velocity omega _z can be performed by CPU13 shown in FIG. 3, for example. Note that the moment of inertia I is such that when the movable part (table 3, rod 4, and bearings 6 and 7) is divided into minute parts, the minute part is regarded as a mass point, the i-th mass point is _mi , and the movable part center If the distance from is r _i , then I = Σ (m _i · r _i ² ).

  Here, a case where an angular velocity around the z-axis is detected using a conventional sensor as described in Patent Document 1 will be described. A sensor using a conventional technique is a sensor in which one end of a table and a rod are connected by a bearing with two degrees of freedom, and the other end of the rod and a base are connected by a bearing with three degrees of freedom, and a strain gauge is provided on the rod. It becomes a structure. That is, the compressive / tensile force in the axial direction of the rod, which is an elastic body, is detected.

  When a sensor of the prior art is attached to the center of the rotary table and the angular velocity around the z axis is detected, due to the inertial mass of the rod itself, an elastic rod is generated and an accurate force cannot be detected. it is conceivable that. On the other hand, in the motion sensor 1 according to the present embodiment, the arm 5 is a mechanism that causes displacement and / or deformation (plane deformation) only in the z-axis direction, and the influence of distortion due to inertial mass is very small. Therefore, the inertial force can be detected with high accuracy.

  In the motion sensor 1 in the present embodiment, the base 2, the table 3, the rod 4, and the bearings 6 and 7 are rigid bodies, and the elastic body as an object for detecting displacement and / or deformation is the arm 5, whereby the table 3 Furthermore, the magnitude and / or direction of the force applied to the rod 4 can be replaced with the simplest plane deformation in the arm 5. In other words, the inertial force received by the motion sensor 1 due to the displacement and / or deformation of the arm 5 can be detected, and the acceleration and angular velocity can be detected.

  In the motion sensor 1, the base 2 and the table 3 are connected by forming one connecting member including one rod 4 and one arm 5. Six connecting members are provided along the circumferential direction of the table 3, and all connecting members are arranged so as not to face the apex in the virtual conical surface formed by the connecting members. As a result, the magnitude and / or direction of the inertial force received by the movable part (table 3, rod 4, and bearings 6 and 7) can be determined from the three-axis direction force component of the three-dimensional space and the three axes. It can be detected simultaneously as a total of six components of the surrounding moment components.

  Therefore, the motion sensor 1 according to the present embodiment can detect (calculate) the triaxial acceleration from the components in the three axial directions, and can detect the triaxial angular velocity from the moment components around the three axes. It can be said to be an axial motion sensor.

  The motion sensor 1 according to the present embodiment includes a process in which the CPU 13 which is a calculation unit calculates acceleration and a process in which angular velocity is calculated. Therefore, the motion sensor 1 can be configured as an acceleration sensor if only the acceleration is detected by the CPU 13, for example, and as an angular velocity sensor if only the angular velocity is detected.

  In the present embodiment, the case where the motion sensor 1 is provided on the base 2 side of the motion sensor 1 or the center of the rotary table has been described. Acceleration and angular velocity can be detected.

(Embodiment 7)
In this embodiment, the force sensor 201 shown in FIGS. 13 to 15 is used as a sensor, and a processing function of a calculation unit (for example, CPU) provided in the force sensor 201 will be described. 13 is a top view schematically showing the force sensor 201, FIG. 14 is a top view schematically showing the force sensor 201 excluding the table 203, and FIG. 15 schematically shows the force sensor 201. It is sectional drawing shown.

  The force sensor 201 has a base 202, a table 203 having six degrees of freedom with respect to the base 202, and six parallelly arranged tables that connect the table 203 and the base 202 to each other. And a connecting portion. The structure in which the table 203 is supported by the plurality of connecting portions in this way is a parallel link structure. The force sensor 201 having a parallel link structure has force components Fx, Fy, Fz in the three-axis direction of the orthogonal coordinate system (x-axis, y-axis, z-axis) of the three-dimensional space, with six degrees of freedom of the table 203, It can be detected as a total of six components of the moment components Mx, My and Mz around the three axes. Although the table 203 shows a case where the table 203 receives a load, the base 202 side may receive a force (load).

  The connecting part of the force sensor 201 is fixed to the bearing 206 having three degrees of freedom for receiving the movement of the table 203, the bearing 207 having two degrees of freedom for receiving the movement of the bearing 206, and the base 202. The table 203 and the base 202 are coupled to each other including a receiving arm 205 and a rod 204 having one end connected to the bearing 206 and the other end connected to the bearing 207. As shown in FIG. 13 and FIG. 14, the force sensor 201 is arranged so that the positional relationship between the shaft mounting 206 in the table 203 surface and the bearing 207 in the base 202 surface is shifted. .

  Specifically, in the circular table 203, the six bearings 206 are arranged on the circumference thereof at an angle of, for example, 60 °, and in the circular base 202, the six bearings 207 are paired, for example, 120 °. They are arranged on the circumference at an angle. Since a force that cannot be detected is generated in a structure in which the bearing 206 and the bearing 207 overlap in plan view, in this embodiment, the positional relationship between the bearing 206 in the surface of the table 203 and the bearing 207 in the surface of the base 202 is determined. It arranges so that it may shift.

  The bearings 206 and 207 of the force sensor 201 are spherical bearings that hold, for example, a steel ball as a spherical surface and can move with three or two degrees of freedom. Each material of the base 202, the table 203, and the rod 204 is a rigid body that can withstand a rated load applied to the table 203, and the arm 205 is an elastic body. For example, the base 202, the table 203, and the rod 204 are rigid bodies made of a metal such as stainless steel (for example, SUS304) that is excellent in corrosiveness and workability.

  The arm 205 of the force sensor 201 is formed so as to extend in a branch shape from the protruding portion protruding from the center of the base 202 toward the outer peripheral portion of the base 202. Each arm 205 is made of a metal such as stainless steel (eg, SUS304) excellent in corrosiveness and workability when formed integrally with the base 202 so as to have a gimbal structure, but extends in a branch shape. Therefore, the elastic body has a sufficiently large change amount with respect to the change amount of the base 202.

  The force sensor 201 includes a detection element (displacement sensor) 208 that detects displacement and / or deformation of the arm 205 that is an elastic body. The force sensor 201 includes a circuit board 210 having a calculation unit (for example, a CPU) that calculates the magnitude and / or direction of the force acting on the table 203 from the detection value of the detection element 208. The circuit board 210 is disposed on a plane facing the table 203 in the base 202.

からテーブル２０３に作用する力の大きさおよび／または方向を計算するものである。 The calculation unit in the present embodiment uses a force conversion algorithm (force conversion program) of the force sensor 201 having a parallel link structure that focuses on arm deformation. The arithmetic unit provided on the circuit board 210 uses a coefficient matrix G for converting the matrix D having the detection value of the detection element 208 as a component into a vector F indicating force,

From this, the magnitude and / or direction of the force acting on the table 203 is calculated.

  Thus, if the coefficient matrix G is known from the equation (1), the force vector F can be obtained from the matrix D of detected values (physical quantities) detected. The components of the coefficient matrix G can be obtained by calculation in advance or can be determined by measuring the output of the uniaxial force sensor 201 in a state where a rated load or the like is applied.

[1. About kinematics and inverse kinematics]
In determining the coefficient matrix G, kinematic analysis / inverse kinematic analysis necessary for the analysis is performed in advance. As shown in FIGS. 13 to 15, the structural parameters include table height h, table joint arrangement radius rT, base radius rB, arm length 1B, rod length 1S (not shown), table joint arrangement angle φT, base joint arrangement angle. φB and arm displacement angle θi.

とする。これからテーブル２０３の中心座標・姿勢が（ｘ、ｙ、ｚ、ａ、ｂ、ｇ）へ変位したときのｔ１〜ｔ６は次式で求められる。

[Calculation of table bearing (joint) coordinates]
When the coordinates of the bearings 206 arranged on the table 203 are t1 to t6, the initial coordinates are

And From now on, t1 to t6 when the center coordinates and orientation of the table 203 are displaced to (x, y, z, a, b, g) are obtained by the following equations.

[Calculation of arm bearing (joint) coordinates]
When the coordinates of the bearing 207 arranged on the arm 205 are represented by b1 to b6, the following expression is obtained.

の関係が成り立つ。それぞれのｘ、ｙ、ｚ成分に着目して書き直すと、次式となる。

ここで、アーム２０５の軸受け２０７に着目すると、

となる。本実施の形態における力覚センサ２０１では、アーム２０５の変位は微小であるため、ｃｏｓ（θｉ）＝１、ｓｉｎ（θｉ）＝θｉと近似することで、ｂｉｘ、ｂｉｙは固定値とみなすことができる。よって、ｂｉｚのみに注目すればよく、ｌＢｓｉｎ（θｉ）＝ｂｉｚより、

アーム変位角度θｉを算出することができる。 [Inverse kinematics]
Inverse kinematics for calculating an operation amount θ (displacement angle) necessary for displacing the table 203 (moving to the target coordinates X (x, y, z, a, b, g)) in the parallel link structure. Perform analysis. Since the coordinates of the bearing 206 of the table 203 can be calculated by the equation (6), the coordinates of the bearing 207 of the arm 205 will be considered. No matter how the table 203 and arm 205 are displaced, the rod length 1S is always constant.

The relationship holds. Rewriting with attention to each x, y, z component, the following equation is obtained.

Here, paying attention to the bearing 207 of the arm 205,

It becomes. In the force sensor 201 according to the present embodiment, since the displacement of the arm 205 is very small, by approximating cos (θi) = 1 and sin (θi) = θi, bix and by can be regarded as fixed values. it can. Therefore, it is only necessary to focus on biz, and since lBsin (θi) = biz,

The arm displacement angle θi can be calculated.

から、次式となる。

ゆえに、（θｄ）’−（θ）’＋Ｋ（θｄ−θ）＝０となり、θｄ−θ＝ｅとおくと、次式のような微分方程式となる。

この微分方程式を解くと、

が得られる。ここで、ｔを無限大とすると、ｅ（ｔ）＝０となることから、終局的にθ→θｄとなり、テーブル座標Ｘが精度高く得られたことになる。なお、実際の計算式、計算プログラムは省略する。 [Kinematics]
Next, kinematic analysis necessary for calculating the table displacement X from the operation amount θ (displacement angle) of the arm 205 is performed. Since numerical iterative processing is used as a kinematic analysis of the parallel link structure, the flow diagram is shown in FIG. Here, s is a differential operator, and K is a proportionality constant. When the displacement angle cos (θi) is input, after performing feedback calculation several times, it converges to obtain X (table displacement). From FIG.

From the following equation:

Therefore, when (θd) ′ − (θ) ′ + K (θd−θ) = 0 and θd−θ = e, a differential equation such as the following equation is obtained.

Solving this differential equation,

Is obtained. Here, if t is infinite, e (t) = 0, so that θ → θd is finally obtained, and the table coordinates X are obtained with high accuracy. The actual calculation formula and calculation program are omitted.

[2. How to find coefficient matrix G]
[2-1. Calculation by iterative processing]
First, the coefficient matrix G is calculated by iterative processing. Each rod 204 connected to the bearings 206 and 207 is in a so-called pin connection state. Only axial force acts on the pin-connected object, and no other force is generated. This axial force can be decomposed into x, y, and z components when the rod 204 is regarded as a vector from the coordinates of both ends of the rod 204. When the axial force is represented by Ti and the x, y, and z components thereof are represented by FTix, FTy, and FTiz, Fx, Fy, and Fz can be obtained by the following equations.

となり、θｘ、θｙ、θｚはロッド２０４と、ｘ、ｙ、ｚ軸との角度であり、

で求められる。 Here, FTix, FTy, and FTiz are

Θx, θy, θz are angles between the rod 204 and the x, y, z axes,

Is required.

Further, Mx, My, and Mz can be obtained by the same concept as that for Fx, Fy, and Fz. When the x, y, and z components of the axial force of the rod 204 are expressed as MTix, MTy, and MTiz, and the distances from the x, y, and z axes to the coordinates of the bearing 206 of the table 203 are lix, lyy, and liz, Mx, My and Mz can be obtained by the following equations.

となり、θｚは式（１８）で求められる値、θｘｙはｘｙ平面とロッド２０４のなす角、ａ、ｂ、ｇはアーム変位角度θｉから算出されたテーブル変位（回転角）である。また、符合±はロッド２０４の取り付け角度によって決まる。 Here, MTix, MTy, MTiz are

Θz is a value obtained by Expression (18), θxy is an angle formed by the xy plane and the rod 204, and a, b, and g are table displacements (rotation angles) calculated from the arm displacement angle θi. The sign ± is determined by the mounting angle of the rod 204.

  Next, consider the relationship between the rod axis direction force Ti and the arm displacement angle θi. Assuming that the rod 204 and the arm 205 are vertically connected, the axial force Ti of the rod 204 acts as a torque for deforming the arm 205. However, since Ti is actually connected with a certain angle instead of vertical, it is necessary to replace Ti with a virtual axis perpendicular to the arm 205.

より、ロッド軸方向の力Ｔｉは、

となる。 When the virtual axis perpendicular to the arm 205 is Q, the magnitude of the force acting on the arm 205 can be obtained from the angle (θTi) formed by Q and the rod 204. Since the arm 205 has a spring property, the displacement angle θi of the arm 205 is calculated in consideration of a uniform spring coefficient k.

From the above, the force Ti in the rod axis direction is

It becomes.

となり、行列式で表すと、

となる。 Substituting equation (17) into equation (16) and equation (20) into equation (19), and substituting the above equation there,

And expressed as a determinant:

It becomes.

  In order to obtain the coefficient matrix G, each bearing coordinate is required. In the state where an external force is applied to the force sensor 201, all bearing coordinates are displaced, so the coordinates of the table 203 must be calculated from the arm displacement angle θi, and iterative processing is required here. In the force sensor 201, since the table displacement amount and the arm displacement angle θi are very small, a method of calculating and using the coefficient matrix G in an approximately equilibrium state is also possible.

  As is clear from the comparison between the equations (1) and (24), the force f can be obtained from the displacement angle θi of the arm 205 which is the detected physical quantity. That is, the force sensor 201 can detect a plurality of vector amounts as the force (load) applied to the table 203.

[2-2. Calculation by linear model]
First, the analysis of position kinematics will be described. When Expression (8) is set to | ti−bi | ² −1S ² = 0, the left side is a function of x, y, z, a, b, g, and θi, so this is replaced as follows.

が得られる。ここでδｘ、δθはそれぞれｘ、θの平衡状態からの微小な変化を表し、Ｏ（δ・^２）はδｘ、δθの２次以上の項を意味する。ｌＳが常に一定であることからψ（０，０）＝０であり、高次項Ｏ（δ・^２）を無視すると式（２６）は、

となる。これを整理するとテーブル２０３の微小変位δｘに対するアーム２０５の微小変位θの関係が、

で求められる。 If equation (25) is expanded in the vicinity of the equilibrium state ((x, θ) = 0),

Is obtained. Here, δx and δθ represent minute changes from the equilibrium state of x and θ, respectively, and O (δ · ² ) means a second or higher order term of δx and δθ. Since lS is always constant, ψ (0,0) = 0, and ignoring the high-order term O (δ · ² ),

It becomes. To summarize this, the relationship of the minute displacement θ of the arm 205 to the minute displacement δx of the table 203 is

Is required.

Next, the characteristics of the force sensor 201 will be described. Between the external force applied to the table 203 (f = [Fx Fx Fy Fz Mz My Mx]) and the torque (τ = [τ1 τ2 τ3 τ4 τ5 τ6]) applied to the bearing 207 of the arm 205 (deforms the arm 205) The following relationship holds from the principle of virtual work.

となり、軸受けトルクτｉはアーム２０５の回転変位δθｉに比例することから、テーブル２０３に加わる力とアーム２０５の回転変位の関係が、

として得られる。 Substituting equation (28) into the above equation, the relationship between the force applied to the table 203 and the torque around the bearing 207 of the arm 205 is

Since the bearing torque τi is proportional to the rotational displacement δθi of the arm 205, the relationship between the force applied to the table 203 and the rotational displacement of the arm 205 is

As obtained.

  As can be seen by comparing the equations (1) and (30), the force f can be obtained from the rotational displacement δθi of the arm 205, which is the detected physical quantity. That is, the force sensor 201 can detect a plurality of vector amounts as the force (load) applied to the table 203.

[2-3. Calculation based on measurement data]
For example, the output when a rated load is applied is measured for each axis (Fx Fy Fz Mz My Mx) of the force sensor 201. FIG. 17 shows a table of output characteristics of the force sensor 201. On the basis of this result, it is only necessary to obtain a coefficient that can output only a specific axis for an inspection axis having a certain characteristic. This is a correction matrix coefficient H such that the rated load is a diagonally arranged matrix.

であり、この右辺へ補正行列係数Ｈを掛けることで、次式に示す力が得られる。

The relationship between the arm displacement angle (θ) and the output (v) can be expressed by a formula in the table of FIG.

By multiplying the right side by the correction matrix coefficient H, the force shown in the following equation is obtained.

  As is clear from the comparison between Expression (1) and Expression (34), the force f can be obtained from the displacement angle θ of the arm 205 which is the detected physical quantity. That is, the force sensor 201 can detect a plurality of vector amounts as the force (load) applied to the table 203.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  For example, as a detection element for detecting displacement and / or deformation of the arm, a piezoelectric element may be provided on the arm, a capacitive element, an optical element (for example, a laser), or the like may be provided on the base. In addition, the arm can be made of quartz to capture changes in natural vibration. As described above, the detection of the displacement and / or deformation of the arm can be performed from, for example, an electric signal obtained by converting the distortion and change amount of the arm.

  For example, when a force sensor or a motion sensor is installed in an installation part, if the installation part is regarded as a base and an arm, a bearing, a rod, a table, etc. are assembled on the installation part, a structure without a base is obtained. It can be set as a force sensor or a motion sensor.

  The present invention is widely used in the field of force sensors, motion sensors, and robots using the same.

1, 1a sensor (force sensor)
2, 2a Base 3 Table 4 Rod 4a Linear actuator 5 Arm 5a Gimbal (arm)
6 Bearing (first bearing)
7, 7a Bearing (second bearing)
8 Strain gauge (detection element)
9 Arm Mounting Base 10 Circuit Board 11 Amplifier 12 A / D Converter 13 CPU (Calculation Unit)
14 Memory 15 D / A Converter 20 Magnetic Identification Element (Detection Element)
20a Magnetoresistive element 20b Magnet 21 Stopper 22 Magnetoresistive element 23 Magnet 30 Capacitance element (detecting element)
30a, 30b Electrode 31 Connection part 101 Sensor (force sensor)
102 base 103 table 103a hole 104 connecting portion 105 base 105a hole 106 bearing (first bearing)
107 Bearing (second bearing)
108 Capacitance element (detection element)
110 circuit board 201 sensor (force sensor)
202 Base 203 Table 204 Connecting portion 205 Arm 206 Bearing (first bearing)
207 Bearing (second bearing)
208 detecting element 210 circuit board SD detecting element

Claims (2)

Base and
A table having six degrees of freedom with respect to the base and disposed opposite the base;
6 connecting portions arranged in parallel to connect the table and the base;
A force sensor comprising:
The connecting portion is fixed to the base, a first bearing having three degrees of freedom to receive the movement of the table, a second bearing having two degrees of freedom to receive the movement of the first bearing, and the second bearing An arm that receives the movement, and the table and the base are connected,
The base and the arm are integrally molded so as to have a gimbal structure having a spring property,
A detection element for detecting displacement and / or deformation of the arm;
Using a coefficient matrix G for converting the matrix D having the detection value of the detection element into a vector F indicating force,

A calculation unit for calculating the magnitude and / or direction of the force acting on the table or the base from
A force sensor characterized by comprising:   The force sensor according to claim 1, wherein the component of the matrix D is a displacement or a displacement angle of the arm.

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