JP2011209103A - Device and method for detecting slip sense - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and method for detecting a slip sense, which detects the slip sense by using a force sensor.SOLUTION: The device for detecting the slip sense which detects a slip occurring between a component P and a contact part R4 is equipped with: the force sensor 1 which detects an external force F impressed on the contact part R4, using a strain detecting resistance element S; a signal input part 9 which inputs an initial signal of a prescribed frequency to the strain detecting resistance element S; a frequency analyzing part 62 which performs frequency analysis of a sensor output signal Vs' from the strain detecting resistance element S; and a slip sense determining part 63 which determines that the slip occurs between the component P and the contact part R4, when the intensity of a frequency component different from the frequency component of the initial signal, out of the frequency components detected in the frequency analyzing part 62 exceeds a threshold, and also determines that the slip does not occur between the component P and the contact part R4, when the intensity of the frequency component different from the frequency component of the initial signal is equal to or lower than the threshold.

Description

  The present invention relates to a slip detection device and a slip detection method for detecting a slip sensation using a force sensor such as a multi-axis force sensor.

  In an automatic working machine such as a robot hand, a force is applied to a work target or an action of a force is applied from the outside world in the work operation. In this case, the automatic work machine is required to detect an external force or moment applied to itself and perform control corresponding to the force or moment. In order to perform control corresponding to force and moment with high accuracy, it is necessary to accurately detect externally applied force and moment.

  Therefore, conventionally, an elastic force sensor that measures force based on a deformation amount proportional to an external force has been proposed. As an elastic force sensor, a sensor having a structure in which a plurality of strain detecting resistance elements are provided in a portion of a strain generating body that is elastically deformed according to an external force is known. When an external force is applied to the strain generating body of the elastic force sensor, an electrical signal corresponding to the degree of deformation (stress) of the strain generating body is output from a plurality of strain detecting resistance elements. Based on these electric signals, a force of two or more components applied to the strain generating body can be detected. Measurement of stress generated by the elastic force sensor is calculated based on the electrical signal.

  As one type of elastic force sensor, a multi-axis force sensor having a plurality of strain detecting resistance elements in a strain generating body portion is known. For example, a 6-axis force sensor uses an external force as a stress component (force: Fx, Fy, Fz) in each axial direction of three axes (X axis, Y axis, Z axis) in the orthogonal coordinate system and torque in each axial direction. It is divided into components (moments: Mx, My, Mz) and detected as 6-axis components.

  As a conventional example of a six-axis force sensor, a six-axis force sensor disclosed in Patent Document 1 uses a semiconductor manufacturing process to place a plurality of strain detection resistance elements on a portion of a strain generating body on a semiconductor substrate in a predetermined arrangement pattern. It is assembled in one piece. The six-axis force sensor is composed of a plate-like semiconductor substrate having a substantially square planar shape, and includes a supporting portion in the peripheral portion, an action portion having a substantially square shape located in the central portion, and four square action portions. It is comprised from the connection part which connects between each of one side and the corresponding part of a support part. The strain detecting resistance element is provided at a boundary portion between each side of the square action portion and the connecting portion. According to this six-axis force sensor, the shape of the strain-generating body portion is improved, the arrangement pattern of a plurality of strain detection resistance elements is optimized, and at the position affected by the thermal effect equivalent to the strain detection resistance elements. In addition, by providing the temperature compensating resistance element at a position that is not affected by the stress, highly accurate stress detection can be performed.

  On the other hand, in an automatic working machine such as a robot hand, in order to prevent the grasped object from slipping and falling, the contact force received from the object, the position where the contact force is applied, etc. are measured, Detecting slip as a sense of slip has been performed.

  For example, in Patent Document 2, a fingertip piece to be directly subjected to contact force is projected through a sensor piece at the tip of a base piece to be fixed against the action of contact force. Provides a sensor for detecting a bending moment acting on each detection position at each of the first detection position closer to the base and the second detection position closer to the fingertip, and the first detection position and the second detection position There is disclosed a tactile sensor device that derives an action position of a contact force acting on a fingertip piece based on a detected value of a bending moment. According to this tactile sensor device, it is possible to detect whether or not the grasped object is slipping based on the change in the position where the contact force is applied.

JP 2006-125873 A JP-A-8-254471

However, if a tactile sensor device as described in Patent Document 2 is provided in addition to the above-described force sensor such as a multi-axis force sensor in order to cause an automatic working machine such as a robot hand to detect a slip, the number of parts This greatly increases the complexity and size of the apparatus, and increases the manufacturing cost.
Therefore, it has been desired to detect a slip sensation using only a force sensor.

  The present invention has been made in view of these circumstances, and an object thereof is to provide a slip detection device and a slip detection method for detecting a slip sense using a force sensor.

  A slip sensation detection apparatus according to the present invention is a slip sensation detection apparatus that detects slip generated between an object and a contact part that contacts the object, and uses the strain detection resistance element to detect the slip. A force sensor for detecting an external force applied to the signal, a signal input unit for inputting an initial signal of a predetermined frequency to the strain detection resistance element, and a frequency analysis unit for frequency analysis of an output signal from the strain detection resistance element When the intensity of the frequency component different from the frequency component of the initial signal among the frequency components detected by the frequency analysis unit exceeds a threshold, it is determined that slip has occurred between the object and the contact unit. And a slip sensation determining unit that determines that no slip has occurred between the object and the contact portion when the intensity of the frequency component different from the frequency component of the initial signal is equal to or less than the threshold value. With features That.

  The slip detection method according to the present invention is a slip detection method for detecting slip generated between an object and a contact part that contacts the object, and an external force applied to the contact part is detected. An initial signal input step of inputting an initial signal of a predetermined frequency to a strain detection resistance element provided in the force sensor to detect; a frequency analysis step of frequency analysis of an output signal from the strain detection resistance element; and the frequency Of the frequency components detected by the analysis unit, when the intensity of the frequency component different from the frequency component of the initial signal exceeds a threshold, it is determined that slip has occurred between the object and the contact unit, and the initial component A slip determination step for determining that slip does not occur between the object and the contact portion when the intensity of the frequency component different from the frequency component of the signal is equal to or less than the threshold value. And butterflies.

  According to such a configuration, when slippage occurs between the object and the contact portion, vibration due to friction between the object and the contact portion is transmitted to the force sensor, and the resistance value of the strain detection resistance element is periodically changed. To change. Since the initial signal of a predetermined frequency is input to the strain detection resistance element, the output signal from the strain detection resistance element is a waveform of the predetermined frequency by the initial signal and a frequency due to frictional vibration different from this frequency. It becomes a composite waveform with the waveform. The detection signal is subjected to frequency analysis, and when the intensity of the frequency component different from the frequency component of the initial signal exceeds a predetermined threshold value, it is determined that slip has occurred between the object and the contact portion. Determine. Accordingly, it is possible to detect that slip has occurred between the object and the contact portion without providing a sensor other than the force sensor.

  Moreover, it is preferable that the surface of the said contact part is coat | covered with the elastomer, and the frequency of the said initial signal is set higher than the natural period of the said elastomer.

  According to such a configuration, since the surface of the contact portion is covered with the elastomer, vibration is likely to occur when the object slips. In addition, since the natural period of the elastomer is lower (for example, about several tens of Hz) than the natural period of metal or the like, the frequency of the initial signal can be reduced by setting the frequency of the initial signal high (for example, about several kHz). The difference from the frequency component due to is clarified, and the detection accuracy can be improved.

  According to the present invention, it is possible to provide a slip sensation detection apparatus and a slip sensation detection method that detect a slip sensation using a force sensor.

1 is a schematic side view of an automatic working machine to which a slip sensation detection apparatus according to an embodiment is applied. (A) is sectional drawing of a contact part and a force sensor, (b) is a perspective view of a force sensor. It is a top view of a force sensor shown excluding wiring. It is a top view of a force sensor. It is a circuit diagram which shows the electrical connection relation of the resistance element for distortion detection, and the resistance element for temperature compensation. (A) is a block diagram which shows the processing circuit of a sensor output signal, (b) is a block diagram of a calculating part. (A) is a graph schematically showing the waveform of the sensor output signal, and (b) is a spectrum distribution diagram obtained by frequency analysis of the sensor output signal from time t1 to time t2. It is an operation | movement flowchart of a slipperiness detection apparatus.

  A first embodiment of the present invention will be described in detail with reference to the drawings. In the description, the same elements are denoted by the same reference numerals, and redundant description is omitted. In the present embodiment, a case will be described as an example where the present invention is applied to an automatic work apparatus that grips an object such as a part and assembles it onto a product.

FIG. 1 is a schematic side view of an automatic working machine to which the slip detection device according to the present embodiment is applied.
As shown in FIG. 1, the automatic working device R is, for example, a so-called robot hand, and is installed along a line of a factory that manufactures a product. The automatic working device R includes a device main body R1 installed on the floor, an arm portion R2 installed on the upper portion of the device main body R1, and a gripping portion R3 provided at the tip of the arm portion R2. .
The arm portion R2 has a plurality of joint portions r, and can be rotated in the horizontal direction or the vertical direction so that the tip gripping portion R3 can be arranged in a desired position or orientation.
The gripping part R3 has a pair of contact parts R4 that come into contact with the component P that is the object, and a drive part R5 that brings the pair of contact parts R4 close to and away from each other. A force sensor 1 for detecting an external force F received by the contact portion R4 from the component P is installed inside the contact portion R4.
The apparatus main body R1 includes a control unit R6 that controls the operation of the arm part R2 and the gripping part R3, a power supply device (not shown), and the like.
For example, according to a program stored in advance, the automatic working device R grips the part P, which is an object placed on the work table D, with the gripping portion R3, and then drives the arm portion R2 to reach the product mounting position. The part P is transported and the part P is attached to the product.

2A is a cross-sectional view of the contact portion and the force sensor, and FIG. 2B is a perspective view of the force sensor.
As shown in FIG. 2A, the contact portion R4 has a metal main body portion R4a having a hollow cylindrical shape, and an elastomer R4b coated on the surface of the main body portion R4a.
A reaction force F1 received from the component P when the component P is gripped and a frictional force F2 generated between the component P and the elastomer R4b when the component P slides act on the contact portion R4.
In the following description, the reaction force F1 and the friction force F2 may be collectively referred to as an external force F.

The distal end side of the main body portion R4a is formed and closed in a dome shape, and the proximal end side of the main body portion R4a is connected to the driving portion R5 (see FIG. 1).
The elastomer R4b is a so-called rubber, and is made of, for example, silicone rubber or fluorine rubber. Elastomer R4b has a lower natural frequency than the metal material that constitutes main body R4a, and generates vibration at a low frequency when slippage occurs between contact portion R4 and component P. It has a function to make it.

The force sensor 1 is, for example, a six-axis force sensor, and the external force F is converted into stress components (forces: Fx, Fy, Fz) in the three axial directions (X axis, Y axis, Z axis) of the orthogonal coordinate system. And a torque component (moment: Mx, My, Mz) in each axial direction, and has a function of detecting as a six-axis component.
As shown in FIGS. 2A and 2B, the force sensor 1 includes a pedestal 11, a cylindrical damping mechanism 12, and a force sensor chip 2.

  The pedestal 11 forms a support base portion made of, for example, stainless steel (SUS). On one end side (lower side in FIG. 2) of the pedestal 11, a sensor chip support portion 11a is provided at the center portion, and an attenuation mechanism support portion 11b is provided at the peripheral portion. The force sensor chip 2 is attached to the sensor chip support portion 11a via a glass pedestal 13 and a bonding layer. In addition, the damping mechanism 12 is attached to the damping mechanism support portion 11b through the bonding layer 15. The other end 11c of the base 11 is fixed to a resin or the like filled in the main body R4a.

  The damping mechanism 12 is a buffer mechanism that weakens the external force transmitted to the force sensor chip 2 when receiving the external force or load and transmitting the external force to the force sensor chip 2 via the connecting rod 16. . The damping mechanism 12 has a cylindrical holding portion 12a that holds one end side of the connecting rod 16 via the joint portion 18, and a cylindrical shape that has a larger diameter than the holding portion 12a and covers the force sensor chip 2. And a case portion 12b. The holding part 12a is fixed to the inner wall on the distal end side of the main body part R4a. In the case portion 12b, a plurality of elongated holes 12c are formed along the circumferential direction.

  As shown in FIG. 2A, the connecting rod 16 is a columnar member, one end side is held by the holding portion 12 a via the joint portion 18, and the other end side is the action of the force sensor chip 2. It connects to the part 21 (refer FIG. 3) via the junction part 19 which has insulation.

Next, the configuration of the force sensor chip 2 will be described in detail with reference to FIGS. 3 and 4. FIG. 3 is a plan view of the force sensor excluding the wiring. FIG. 4 is a plan view of a force sensor including wiring.
The force sensor chip 2 is a six-axis force sensor chip, and is configured on a substantially square base member 20 in plan view as shown in FIG. As shown in FIG. 3, the base member 20 includes an action part 21 to which an external force F (see FIG. 2, F <b> 1 and F <b> 2) is transmitted, and a support part that supports the action part 21 via the connection part 23. 22, and a connecting portion 23 that connects the action portion 21 and the support portion 22.

  Further, as shown in FIG. 3, a strain detection resistance element S for detecting the magnitude and direction of the external force F and an element for performing temperature compensation of the strain detection resistance element S are provided at predetermined positions on the base member 20. And a temperature compensating resistor element 27 are arranged. The strain detecting resistance element S and the temperature compensating resistance element 27 are connected to the signal electrode pad 25 and the GND electrode pad 26 through the wiring 28 as shown in FIG.

The base member 20 is a member that becomes a base of the force sensor chip 2. As shown in FIG. 3, the base member 20 includes an action part 21, a support part 22, and a connection part 23. Further, as shown in FIG. 3, through holes G, H, I, J, K, L, M, and N are formed in the base member 20. The base member 20 can be composed of a semiconductor substrate such as silicon, for example.
A substantially square ring-shaped GND (GROUND) wiring 29 is formed on the outer peripheral edge of the base member 20 with a required width along each side. A GND electrode pad 26 to be described later is connected to the GND wiring 29. Note that the square ring-shaped GND wiring 29 is an example, and any wiring can be used as long as it has a constant potential.

  The action portion 21 is a region to which an external force F is applied. As shown in FIG. 3, the action portion 21 is formed at the center of the force sensor chip 2. As described above, the action portion 21 is joined to the connecting rod 16 of the damping mechanism 12 via the joint portion 19 having an insulating property (see FIG. 2A).

  The support portion 22 is a region that supports the action portion 21 via the connecting portion 23. As shown in FIG. 3, the support portion 22 is formed at the peripheral portion of the force sensor chip 2 and has a rectangular frame shape. Further, as described above, all or part of the support portion 22 is bonded to the sensor chip support portion 11a of the pedestal 11 via the glass pedestal 13 and the bonding layer 14 (see FIG. 2A). The shape of the support portion 22 is not limited to a square frame shape as long as the action portion 21 can be supported, and may be a circular frame shape, for example.

  The connection part 23 is an area for connecting the action part 21 and the support part 22. As shown in FIG. 3, the connecting portion 23 is formed between the action portion 21 and the support portion 22. Further, as will be described later, the connecting portion 23 is formed with elongated slit-like through holes G, H, I, J, K, L, M, and N at predetermined positions.

  As shown in FIG. 3, the connecting portion 23 includes T-beam shaped regions 23a, 23b, 23c, and 23d that are made up of elastic portions 23a1, 23b1, 23c1, and 23d1 and bridge portions 23a2, 23b2, 23c2, and 23d2. Each has. As shown in FIG. 3, the elastic portions 23a1, 23b1, 23c1, 23d1 are connected to the inner periphery of the support portion 22 at both ends in the length direction, and the bridge portions 23a2, 23b2, 23c2, respectively corresponding to the center portions. It is connected to one end of 23d2. Further, as shown in FIG. 3, the bridge portions 23a2, 23b2, 23c2, and 23d2 are connected to the elastic portions 23a1, 23b1, 23c1, and 23d1 corresponding to the respective ends in the length direction, and the other end portions. Is connected to the action part 21.

  The T-beam shaped regions 23a, 23b, 23c, and 23d correspond to the four sides of the force sensor chip 2 so as to be four times symmetrical with respect to the center of the action portion 21, as shown in FIG. Preferably formed. In this way, by forming the T-beam shaped regions 23a, 23b, 23c, and 23d so as to be four-fold symmetric about the action part 21, the support part 22 supports the action part 21 in a balanced manner from four directions. can do.

  As described above, the T-beam-like regions 23a, 23b, 23c, and 23d are divided into the low-rigidity region and the high-rigidity region, so that when the external force F is applied to the action portion 21, elasticity The portions 23a1, 23b1, 23c1, and 23d1 absorb excess distortion applied to the bridge portions 23a2, 23b2, 23c2, and 23d2, and the distortion of the entire force sensor chip 2 due to the application of force or moment in one direction is generated. Can be suppressed. Therefore, a strain can be selectively generated in the strain detecting resistance element S corresponding to a force or moment in a specific direction, and other-axis interference can be significantly suppressed.

  The other-axis interference means that when a single component force is input, the measurement result is “0” due to disturbance such as noise even though the input of the force of the other component is “0”. This is a phenomenon that does not occur, that is, a phenomenon in which the measured value of the force or moment varies with the force or moment of the other axis.

  As shown in FIG. 3, the through holes (first through holes) G, H, I, and J are substantially linear slit holes formed so as to penetrate in the thickness direction of the base member 20. The through holes G, H, I, and J play a role of functionally separating the action part 21, the support part 22, and the connection part 23. The force sensor chip 2 has such through-holes G, H, I, and J, so that the external force F applied to the action portion 21 is not dispersed in the support portion 22 and the like, and the strain detection later described. It can be concentrated on the resistance element S, and the external force F applied to the action part 21 can be detected more accurately.

  As shown in FIG. 3, the through holes (second through holes) K, L, M, and N are bowl-shaped slit holes formed so as to penetrate in the thickness direction of the base member 20. The through holes K, L, M, and N are functionally composed of the elastic portions 23a1, 23b1, 23c1, and 23d1 that are the low-rigidity regions and the bridge portions 23a2, 23b2, 23c2, and 23d2 that are the high-rigidity regions. Plays the role of separating. The force sensor chip 2 has such through holes K, L, M, and N, so that the external force F applied to the action portion 21 is not dispersed in the support portion 22 and the like, and the strain detection later described. It can be concentrated on the resistance element S, and the external force F applied to the action part 21 can be detected more accurately.

  The strain detecting resistance element S is an element for detecting the magnitude and direction of the external force F in the force sensor chip 2. The strain detecting resistance element S is made of a material whose resistance value changes in proportion to deformation, and detects strain due to application of the external force F as a change in resistance value. The strain detecting resistance element S can be formed, for example, by ion-implanting impurities such as boron into the base member 20 in a semiconductor manufacturing process. The resistance element S for strain detection decreases in resistance when strain due to compression occurs, and increases in resistance when strain due to tension occurs.

As shown in FIG. 3, the strain detecting resistance element S is formed on the base member 20, and a plurality of strain detecting resistance elements S are formed on a deformation generating portion corresponding to a connection portion between the action portion 21 and the connecting portion 23. Here, as shown in FIG. 3, the deformation generating portion means the vicinity of the connecting portion between the acting portion 21 where the distortion due to the external force F applied to the acting portion 21 is most generated and the bridge portions 23a2, 23b2, 23c2, and 23d2. Pointing. As shown in FIG. 3, the strain detecting resistance element S is formed so as to be parallel to the major axis direction of the bridge portions 23a2, 23b2, 23c2, and 23d2.
As shown in FIG. 4, the strain detecting resistance element S is connected to the signal electrode pad 25 and the GND electrode pad 26 via the wiring 28.

The signal electrode pad 25 and the GND electrode pad 26 are electrode pads for applying a voltage signal having a predetermined frequency to the strain detecting resistance element S and the temperature compensating resistance element 27. As shown in FIG. 4, the signal electrode pad 25 and the GND electrode pad 26 are connected to the respective strain detection resistance elements S and temperature compensation resistance elements 27 via wirings 28.
The signal electrode pad 25 is connected to a signal input unit 9 (see FIG. 5) described later.

  The temperature compensating resistance element 27 is an element for performing temperature compensation of the strain detecting resistance element S. The temperature compensating resistance element 27 is made of a material whose resistance value changes with a change in environmental temperature, and detects a change in environmental temperature as a change in resistance value. The temperature compensating resistance element 27 can be formed, for example, by ion-implanting impurities such as boron into the base member 20 in the semiconductor manufacturing process.

  The temperature compensating resistance element 27 is configured by an element having the same temperature condition as the strain detection resistance element S. Further, as shown in FIG. 3, the temperature compensating resistance element 27 is formed on the base member 20, and is associated with the twelve strain detection resistance elements S on the base member 20, so as to correspond to the strain detection resistance. Twelve are arranged at predetermined positions in the vicinity of the element S.

As shown in FIG. 3, the temperature compensating resistance element 27 is disposed at a location that is not affected by the distortion caused by the applied external force F. That is, as shown in FIG. 3, each of the temperature compensating resistive elements 27 is in the vicinity of the corresponding strain detecting resistive element S and inside the through holes K, L, M, and N that are free ends. It is arranged near the periphery. The force sensor chip 2 can detect only the ambient temperature around the chip by disposing the temperature compensating resistance element 27 in a place not affected by the external force F in this way.
As shown in FIG. 4, the temperature compensating resistance element 27 is connected to the signal electrode pad 25 and the GND electrode pad 26 via the wiring 28.

  As shown in FIG. 4, the wiring 28 is a wiring for connecting the strain detection resistance element S, the temperature compensation resistance element 27, the signal electrode pad 25, and the GND electrode pad 26. The wiring 28 connects the strain detection resistance element S and the temperature compensation resistance element 27 on the base member 20 so that a bridge circuit as will be described later can be formed.

Next, the electrical connection relationship between the strain detection resistance element S and the temperature compensation resistance element 27 in the force sensor chip 2 will be briefly described with reference to FIG. FIG. 5 is a circuit diagram showing an electrical connection relationship between the strain detection resistance element and the temperature compensation resistance element.
As shown in FIG. 5, the strain detecting resistive element S and the temperature compensating resistive element 27 constitute a half bridge circuit HB corresponding to the lower half of the full bridge circuit FB inside the force sensor chip 2. Yes.

As shown in FIG. 5, one end side (the lower side in the figure) of the strain detection resistance element S and the temperature compensation resistance element 27 are connected to each other via a wiring 28 and also connected to a ground potential GND (GND). It is connected to the wiring 29). Further, the other end side (upper side in the figure) of the strain detecting resistance element S and the temperature compensating resistance element 27 is connected to the signal electrode pad 25, respectively. The other end side (the upper side in FIG. 5) of the signal electrode pad 25 is connected to the external resistors 31 and 32 provided outside the force sensor chip 2 and then connected to each other. Is connected to a signal input unit 9 provided in the.
The signal input unit 9 is composed of, for example, an AC power supply, and has a function of inputting an initial signal of a predetermined voltage at a predetermined frequency A to the strain detection resistance element S and the temperature compensation resistance element 27.

  In the full bridge circuit FB configured as described above, the other end side (external resistors 31 and 32 side) of the strain detecting resistor element S and the temperature compensating resistor element 27 is a filter section described later as shown in FIG. The difference (Vs−Vm) between the output signals detected by the strain detecting resistive element S and the temperature compensating resistive element 27 is the sensor output signal Vs ′.

  Here, the sensor output signal Vs in the present embodiment is a signal obtained by taking a change in resistance value corresponding to the strain generated in the strain detecting resistance element S in response to a change in the external force F as a change in voltage value. pointing. The sensor output signal Vs includes the frequency component of the initial signal input by the signal input unit 9 and the frictional force input to the contact portion R4 (more specifically, the force sensor 1) as the component P slides with respect to the contact portion R4. And a frequency component of F2.

The temperature compensated output signal Vm refers to a signal obtained by taking out a change in resistance value corresponding to the strain generated in the temperature compensating resistance element 27 as a change in voltage value in proportion to a change in environmental temperature. Yes. The temperature compensation output signal Vm has the frequency component of the initial signal input by the signal input unit 9.
Since the temperature compensating resistance element 27 is arranged at a position where the resistance value changes only depending on the environmental temperature as described above, the temperature compensation output signal Vm is a pure environment not affected by the external force F. A value indicating the temperature. The temperature compensation output signal Vm is used as a means for temperature compensating the sensor output signal Vs including the influence of the environmental temperature to the sensor output signal Vs ′ not including the influence of the environmental temperature.

  The force sensor chip 2 is configured as a full bridge circuit FB as a whole circuit, thereby more appropriately canceling a change in resistance value due to a change in environmental temperature from a change in resistance value of the strain detection resistance element S, Only the change in resistance value due to the external force F in the strain detecting resistance element S can be taken out appropriately. Therefore, the external force F applied to the action part 21 can be detected more accurately.

  In this embodiment, the external resistors 31 and 32 are provided outside the force sensor chip 2. However, the external resistors 31 and 32 are provided inside the force sensor chip 2 to provide a force sense. A full bridge circuit FB may be configured inside the sensor chip 2.

Next, the configuration of the processing circuit for the sensor output signal Vs and the temperature compensation output signal Vm will be described with reference to FIGS.
FIG. 6A is a block diagram illustrating a sensor output signal processing circuit, and FIG. 6B is a block diagram of a calculation unit.
As shown in FIG. 6, the processing circuit for the sensor output signal Vs and the temperature compensation output signal Vm includes a filter unit 51, a buffer unit 52, an A / D conversion unit 53, a calculation unit 60, an output unit 54, It has.

The filter unit 51 removes unnecessary frequency components (noise) included in the sensor output signal Vs and the temperature compensation output signal Vm. The filter unit 51 is, for example, a low-pass filter, and although not shown, can be realized by a capacitor in parallel with the input signal and a resistor in series with the input signal.
The buffer unit 52 is an amplifier that amplifies the voltage waveforms of the sensor output signal Vs and the temperature compensation output signal Vm.
The A / D converter 53 converts an analog signal that is a continuous quantity into a discrete digital signal. The A / D converter 53 is configured by, for example, a known A / D converter.
As a result, the sensor output signal Vs and the temperature compensation output signal Vm are noise-cut in the filter unit 51, amplified in the buffer unit 52, converted from an analog signal to a digital signal in the A / D conversion unit 53, and temperature compensated. The sensor output signal Vs ′ is output to the calculation unit 60.

The computing unit 60 has a function of performing frequency analysis on the sensor output signal Vs ′ and determining whether or not the component P is slipping with respect to the contact part R4. The arithmetic unit 60 includes, for example, a central processing unit (CPU), a storage device such as a RAM (Random Access Memory) and a ROM (Read Only Memory), and a function program stored in the storage device. Has been.
As shown in FIG. 6B, the calculation unit 60 includes an output value storage unit 61, a frequency analysis unit 62, a slip sensation determination unit 63, and a reference value storage unit 64 as functional blocks. .

  The output value storage unit 61 stores the sensor output signal Vs ′ converted into a digital signal by the A / D conversion unit 53 in time series in association with time t (see FIG. 7A).

The frequency analysis unit 62 reads out the data of the sensor output signal Vs ′ stored and held in the output value storage unit 61 in a predetermined time unit, analyzes the frequency, and obtains a spectrum distribution. As a frequency analysis method, for example, FFT (Fast Fourier Transform) or MEM (Maximum Entropy Method) can be used.
The frequency analysis unit 62 outputs the detected frequency component and its intensity to the slip sensation determination unit 63.

Here, frequency components included in the sensor output signal Vs ′ will be described with reference to FIG. FIG. 7A is a graph schematically showing the waveform of the sensor output signal, and FIG. 7B is a spectrum distribution diagram obtained by frequency analysis of the sensor output signal from time t1 to time t2.
As shown in FIG. 7A, in the initial state, an initial signal having a predetermined frequency A is input to the strain detecting resistance element S of the force sensor chip 2 by the signal input unit 9. Here, for convenience of explanation, it is assumed that an initial signal by the signal input unit 9 is f (t) = sinAt.
When the gripping part R3 (see FIG. 2) grips the component P with a constant force, the reaction force F1 received by the contact part R4 is constant, so the amplitude of the initial signal f (t) is also constant.

When the part P slips from the time t1 to the time t2, the frictional force F2 acts on the contact portion R4 (see FIG. 2). When the frictional force F2 is an input having a periodicity of the frequency B, the frictional force F2 is input to the action unit 21 of the force sensor chip 2 as a vibration of the frequency B, and a strain detecting resistance element is accordingly generated. The resistance value of S changes.
For convenience of explanation, assuming that the input by the frictional force F2 is g (t) = sinBt, the sensor output signal Vs ′ from the time t1 to the time t2 is expressed by the following equation.
f (t) + g (t) = sinAt + sinBt
= 2 sin (A / 2 + B / 2) cos (A / 2-B / 2)

Therefore, by performing frequency analysis on the sensor output signal Vs ′ obtained from time t1 to time t2 by the frequency analysis unit 62, as shown in FIG. 7B, the frequency component A, frequency component B, frequency component ( The four frequency components A / 2 + B / 2) and the frequency component (A / 2−B / 2) and their intensities are detected.
Note that the frequency component shown in FIG. 7B is an example, and it is needless to say that the present invention is not limited to this.

The slip sensation determination unit 63 determines whether or not a slip has occurred between the contact portion R4 and the component P based on the frequency component detected by the frequency analysis unit 62 and its intensity. The slip sensation determination unit 63 is configured to be able to read data from a reference value storage unit 64 to be described later, and to output a determination result to an output unit 54 to be described later.
A specific determination method in the slip sensation determination unit 63 will be described in detail later with reference to FIG.

  The reference value storage unit 64 stores the value of the frequency component A of the initial signal and a threshold set in advance with respect to the intensity of the frequency component. The threshold value can be obtained in advance by conducting a preliminary experiment for confirming the detection accuracy of the slip sensation.

As illustrated in FIG. 6A, the output unit 54 outputs a command signal related to a predetermined operation based on the determination result of the slip sensation determination unit 63. The output unit 54 includes, for example, a central processing unit, a storage device, a function program, and the like that are common to the calculation unit 60.
In the present embodiment, the output unit 54 increases the gripping force of the gripping unit R3 when, for example, the slip sensation determination unit 63 determines that slippage has occurred between the contact unit R4 and the component P. The command signal is set to be output to the control unit R6 of the automatic work device R.
The setting of the output unit 54 is not limited to this, and a setting may be made such that a warning lamp (not shown) is turned on or the part P is returned to the work table D.

  Next, the operation of the slip detection device according to the present embodiment will be described with reference to FIGS. 1 to 8 (particularly FIG. 8). FIG. 8 is an operation flowchart of the slip detection device.

For example, as shown in FIG. 1, when the operation of the automatic working device R is started, a predetermined voltage is applied from the signal input unit 9 (see FIG. 5) to the strain detection resistance element S provided in the force sensor 1. An initial signal is input at a predetermined frequency (step S1).
At this time, a reaction force F1 of a force for gripping the component P is applied to the contact portion R4 of the automatic working device R, and this reaction force F1 is detected by the force sensor 1. Note that the detection of the reaction force F1 by the force sensor 1 is described in detail in, for example, Japanese Patent Application Laid-Open No. 2006-125873, and thus the description thereof is omitted.

On the other hand, when the component P slips with respect to the contact portion R4, as indicated by a broken line in FIG. 8, vibration due to the slip of the component P is input to the force sensor 1 as a frictional force F2 (see FIG. 2). (Step S2).
When the vibration due to the slip of the component P has a periodicity different from the frequency component A of the initial signal, the sensor output signal Vs output from the strain detecting resistance element S has a frequency component different from the frequency component A of the initial signal. Will be included.

  Next, as shown in FIG. 6A, the sensor output signal Vs and the temperature compensated output signal Vm are noise-cut in the filter unit 51, amplified in the buffer unit 52, and analog signals in the A / D conversion unit 53. Is converted into a digital signal and is output to the calculation unit 60 as a temperature compensated sensor output signal Vs ′ (step S3).

  Then, the frequency analysis unit 62 performs frequency analysis on the sensor output signal Vs ′ input to the calculation unit 60, and obtains a spectrum distribution as shown in FIG. 7B (step S4).

Next, the slip sensation determination unit 63 determines whether or not the sensor output signal Vs ′ includes a frequency component different from the frequency component A of the initial signal (step S5).
Specifically, for example, the difference between each frequency component input from the frequency analysis unit 62 and the frequency component A of the initial signal read from the reference value storage unit 64 is sequentially calculated. Then, when all the differences are 0, the slip sensation determining unit 63 determines that no frequency component other than the frequency component A of the initial signal is included (step S5, No), and the contact R4 and the component P It is determined that no slip has occurred between the two (step S8).

  On the other hand, when the slip sensation determination unit 63 includes a frequency component in which the difference from the frequency component A of the initial signal is not 0 among the frequency components input from the frequency analysis unit 62 (step S5, Yes). Next, the intensity of the frequency component is compared with a preset threshold value (step S6).

Then, when the intensity of the frequency component different from the frequency component of the initial signal is equal to or less than a preset threshold value (step S6, No), the slip sensation determination unit 63 is between the contact portion R4 and the component P. It is determined that no slip has occurred (step S8).
In addition, when there are a plurality of frequency components different from the frequency components of the initial signal, no slip occurs between the contact portion R4 and the component P when the intensity of all the frequency components is equal to or less than a preset threshold value. Is preferably determined.

On the other hand, when the intensity of the frequency component different from the frequency component of the initial signal exceeds a preset threshold value (Yes in step S6), the slip sensation determination unit 63 slips between the contact portion R4 and the component P. Is determined to have occurred (step S7).
In addition, when there are a plurality of frequency components different from the frequency components of the initial signal, if the intensity of at least one of the frequency components exceeds a preset threshold value, the slip between the contact portion R4 and the component P will occur. It is preferable to determine that occurrence has occurred.

  When the slip sensation determining unit 63 determines that slip has occurred between the contact portion R4 and the part P, the output unit 54 sends an instruction signal for increasing the gripping force of the gripping portion R3 to the automatic operation. It outputs to the control part R6 of the apparatus R (step S9).

  As described above, according to the slip sensation detection device according to the present embodiment, the frequency of the sensor output signal Vs (Vs ′) from the strain detection resistance element S is analyzed, and a frequency component different from the frequency component A of the initial signal is detected. When the strength exceeds a predetermined threshold value set in advance, it is determined that a slip has occurred between the component P and the contact portion R4, so that the component P and the contact portion are not provided without providing a sensor other than the force sensor 1. It is possible to detect that slip has occurred between R4 and R4.

  Moreover, since the surface of the contact portion R4 is covered with the elastomer R4b, vibration is likely to occur when the component P slips. In addition, since the natural period of the elastomer R4b is lower (for example, about several tens of Hz) than the natural period of metal or the like, by setting the frequency of the initial signal high (for example, about several kHz), the frequency component of the initial signal The difference from the frequency component due to the slip becomes clear, and the detection accuracy can be improved.

  As mentioned above, although embodiment of this invention was described in detail with reference to drawings, this invention is not limited to this, In the range which does not deviate from the main point of invention, it can change suitably.

  For example, in the present embodiment, it is determined whether or not the intensity of the frequency component different from the frequency component A of the initial signal exceeds the threshold. However, by setting the threshold to 0 (zero), the intensity can be substantially determined. It may be omitted and it may be determined that the component P has slipped immediately when a frequency component different from the frequency component A of the initial signal is detected.

  Further, a correlation between the frictional force F2 input to the contact portion R4 and the intensity of the frequency component different from the frequency component of the initial signal detected by the force sensor 1 is previously stored in, for example, the reference value storage unit 64 by a preliminary experiment. If a frequency component that is different from the frequency component of the initial signal is detected, the frictional force is determined based on the strength of the frequency component different from the frequency component of the initial signal by referring to the correlation stored in advance. The intensity of F2 may be calculated.

  In the present embodiment, as shown in FIG. 2, the elastomer R4b is provided on the surface of the contact portion R4. However, the present invention is not limited to this, and the elastomer R4b may be omitted. Even in such a case, if the difference from the frequency of vibration due to friction is clarified by adjusting the frequency of the initial signal input from the signal input unit 9, the frequency component due to the slip of the component P is obtained in the frequency analysis unit 62. Can be suitably detected.

  Further, in the present embodiment, as illustrated in FIG. 1, the automatic work apparatus R in the factory has been described as an example. However, the present invention is not limited to this, and a large number of fingers (for example, five fingers) such as a humanoid robot are used. Needless to say, the present invention may be applied to a gripping portion (not shown) provided with ().

R Automatic working device R4 Contact part R4a Main body part R4b Elastomer 1 Force sensor 2 Force sensor chip S Strain detection resistance element 60 Operation part 61 Output value storage part 62 Frequency analysis part 63 Slip sensation judgment part 64 Reference value storage part

Claims (3)

A slip sensation detection device that detects slip generated between an object and a contact portion that contacts the object,
A force sensor for detecting an external force applied to the contact portion using a strain detecting resistance element;
A signal input unit for inputting an initial signal of a predetermined frequency to the strain detecting resistance element;
A frequency analysis unit for frequency analysis of an output signal from the strain detection resistance element;
Of the frequency components detected in the frequency analysis unit, when the intensity of the frequency component different from the frequency component of the initial signal exceeds a threshold, it is determined that slip has occurred between the object and the contact unit, When the intensity of the frequency component different from the frequency component of the initial signal is equal to or lower than the threshold value, a slip sensation determination unit that determines that no slip has occurred between the object and the contact portion;
A slip detection device comprising:   The slip detection device according to claim 1, wherein a surface of the contact portion is covered with an elastomer, and a frequency of the initial signal is set to be larger than a natural period of the elastomer. A slip sensation detection method for detecting slip generated between an object and a contact portion that contacts the object,
An initial signal input step of inputting an initial signal of a predetermined frequency to a strain detecting resistance element provided in a force sensor that detects an external force applied to the contact portion;
A frequency analysis step of performing a frequency analysis of an output signal from the strain detection resistance element;
Of the frequency components detected in the frequency analysis unit, when the intensity of the frequency component different from the frequency component of the initial signal exceeds a threshold, it is determined that slip has occurred between the object and the contact unit, When the intensity of the frequency component different from the frequency component of the initial signal is equal to or less than the threshold value, a slip determination step for determining that slip does not occur between the object and the contact portion;
A slip sensation detection method comprising:

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