JP2006017671A - Shear force detection method and slip detection method - Google Patents

Abstract

A shearing force can be detected using a distributed sensor having a simple structure without a shearing force detection structure.
A distributed pressure-sensitive sensor S in which a plurality of pressure-sensitive elements 1 are distributed is brought into contact with an object, and all the outputs of the plurality of pressure-sensitive elements 1 are applied in a state where only pressure acts between the objects. The state is recorded and all the outputs of the plurality of pressure sensitive elements 1 are periodically observed while confirming that the actual contact position is not moved due to the geometric constraints of the outside world. By comparing the output of the pressure-sensitive element 1 being observed with the previously recorded output state, the change in the output region is examined, and when the output region moves or expands in one direction, a shearing force τ is generated. At the same time, it is determined that the direction of the shearing force τ is determined.
[Selection] Figure 3

Description

  The present invention relates to a shear force detection method for detecting a shear force using a distributed pressure sensor and a slip detection method for detecting a slip based on detection information of the shear force.

  As one of distributed pressure sensors, a sensor that measures a pressure distribution and a frictional force distribution at a time has been proposed (for example, see Patent Document 1).

The distributed pressure-sensitive sensor described in Patent Document 1 includes a pair of pressure plates having a large number of concavities and convexities that are fitted to each other on opposite surfaces, and a sheet-like pressure sensor sandwiched between the opposite surfaces of the pressure plates. A detecting portion is formed by disposing electrodes facing the top and bottom surfaces of the concavity and convexity of the opposing surface of the pressure plate, and an intermediate plane therebetween, and between the electrodes in each detecting portion Detection means for detecting conductivity is provided. Based on the detected conductivity, the pressure distribution acting in the direction perpendicular to the sensor surface, which is the outer surface of the pressure plate, and the frictional force (shearing force) distribution acting in parallel with the sensor surface are measured.
JP 2003-98022 A

  By the way, according to the distributed pressure sensor described in Patent Document 1 described above, when the sensor is bent and applied to a substantially cylindrical surface having a small diameter, the parallelism between the upper and lower inclined surfaces is shifted due to a difference in radius, or bent. The internal stress due to may appear in the sensor output of the inclined surface and may not be used as it is. Further, in the conventional tactile sensor including the distributed pressure sensor described in Patent Document 1, when detecting a shearing force or slip, a method of adding an element for detecting a shearing force in the same sensor is employed. The sensor structure is complicated. Furthermore, since the number of detection elements increases, the increase in signal processing load and the increase in the size of sensors and robot fingers or hands mounting the sensors have become problems.

  The present invention has been made in view of such circumstances, and a shear force detection method capable of easily detecting a shear force using a distributed pressure sensor having a simple structure without a shear force detection structure. It is an object of the present invention to provide a slip detection method that detects a slip based on detection information of such a shear force detection method.

  The shear force detection method of the present invention uses a distributed pressure sensor in which a plurality of pressure sensitive elements are distributed on a convex curved surface such as a cylindrical surface, and the pressure sensitive elements are entirely covered with a surface layer. The distributed pressure sensor is brought into contact with an object, and all output states of the plurality of pressure sensitive elements are recorded in a state where only pressure acts between the contact object and the contact object, Under the condition that the position of contact with the contact object does not change, all the outputs of the plurality of pressure sensitive elements are periodically observed, and the output of the pressure sensitive element being periodically observed is recorded first. The change of the output area is compared with the current output state, and when the output area moves or spreads in one direction, it is determined that shear force is generated, and at the same time, the direction (direction) of the shear force It is characterized by determining.

  The detection method of the present invention will be described more specifically.

  First, a distributed pressure sensor is used in which a plurality of pressure sensitive elements are distributed on a convex curved surface such as a cylindrical surface, and the pressure sensitive elements are entirely covered with a surface layer. When pressed, an output appears on the pressure sensitive element at the contact position. Further, when receiving a shearing force from the object, the surface layer finely moves in the direction of the shearing force, and pressure is also applied to the pressure-sensitive element in the non-contact region located in a non-contact position with the object, and an output appears. Therefore, the output of all pressure-sensitive elements is recorded in the storage device at the time of contact, and then all pressure-sensitive elements are periodically checked while confirming that the actual contact position does not move due to external geometric constraints. The output of the element is observed and compared with the recorded value recorded earlier. When the output region changes, it is determined that shear force has occurred, and at the same time, the direction (direction) of the shear force is determined. Furthermore, when the direction of the shearing force is constant and the strength (output of the pressure-sensitive element in the non-contact region) is oscillating with time, it is determined that slip has occurred.

  In the shear force detection method of the present invention, a plurality of pressure-sensitive elements in a state where only pressure acts between the contact objects are converted into multi-stage digital values, recorded, and periodically observed. The output of the pressure sensitive element is converted into a multi-stage digital value to obtain the center of gravity, and the center of gravity is compared with the position of the center of gravity of the digital value of the recording. At the same time as determining that the shearing force is being applied, the direction (orientation) of the shearing force may be determined.

  In addition, a plurality of pressure-sensitive elements in a state where only pressure is applied to the contact object are converted into two-stage digital values and recorded, and outputs of the plurality of pressure-sensitive elements observed periodically are recorded. A centroid is obtained by converting into a two-stage digital value, the centroid position is compared with the centroid position of the digital value of the recording, and shear force is generated when there is a misalignment of the centroid. At the same time, the direction (orientation) of the shear force may be determined.

  In the slip detection method of the present invention, the slip occurs when the direction of the shear force determined by the shear force detection method having the above characteristics is constant and the strength of the shear force changes with time. It is characterized by judging.

  According to the present invention, a distributed pressure-sensitive sensor is brought into contact with an object, and all output states of a plurality of pressure-sensitive elements are recorded in a state where only pressure acts between the object and the contact object. Under the condition that the contact position does not change, all the outputs of the plurality of pressure sensitive elements are periodically observed, and the output of the pressure sensitive elements that are periodically observed and the output state that has been previously recorded are determined. In comparison, the change in the output area is examined, and when the output area moves or spreads in one direction, it is determined that shear force is generated, and at the same time, the direction of the shear force is determined. The shear force can be detected using a distributed pressure sensor that does not have a shear force detection structure. Further, the occurrence of slip can be detected based on the detection information of the shear force.

  As described above, since a shearing force and slip can be detected by a distributed pressure sensor using a pressure-sensitive element arrangement that detects only a force in the normal direction, a plurality of pressure-sensitive elements are formed on a substantially cylindrical surface having a small diameter. Even a distributed sensor that distributes can detect shearing force and slip, and can be effectively used for detection in a small, substantially cylindrical portion such as a fingertip of a robot. In addition, since all the pressure sensitive elements are used as elements exclusively for pressure detection, the position resolution of pressure detection can be increased as compared with those having a shear force detection structure.

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

-Distributed pressure sensor-
FIG. 1 is a diagram schematically showing the structure of a distributed pressure sensor used in the shearing force detection method of the present invention.

  The distributed pressure sensor S shown in FIG. 1 is a cylindrical surface distributed pressure sensor, and includes a plurality of pressure sensitive elements 1... 1 and a core 2 whose outer peripheral surface is a cylindrical surface. The pressure sensitive elements 1... 1 are arranged on the outer peripheral surface of 2. The entire pressure-sensitive elements 1... 1 are covered with a surface layer 3, and the surface layer 3 is coupled to the core 2 via a coupling portion 4. In the distributed pressure sensor S of this example, a plurality of pressure sensitive elements 1 are also arranged in a direction (depth direction) orthogonal to the paper surface of FIG.

  The pressure sensitive element 1 detects and outputs a force acting in the normal direction of the core 2. Specific examples of the pressure-sensitive element 1 include, for example, a structure in which a pressure-sensitive conductive material such as conductive rubber or conductive ink is combined with a matrix-arranged electrode or individual pairs of positive and negative electrodes, or a piezoelectric element. The device is available.

  The core 2 is a columnar member, and the outer peripheral surface thereof is a cylindrical surface. The outer peripheral surface of the core 2 is not limited to a cylindrical surface, and may be a substantially cylindrical surface having a curvature close to a cylindrical surface (perfect circle) or a convex curved surface having another curvature.

  The surface layer 3 is disposed so as to cover the whole of the plurality of pressure sensitive elements 1. The material constituting the surface layer 3 is suitably a flexible material from the viewpoints of dispersing and uniformizing the detection region of the pressure-sensitive element 1 and increasing the friction with the target object T. Note that a hard material may be used from the viewpoint of shear force detection.

  The coupling portion 4 is provided to prevent the surface layer 3 from moving away from the core 2 and sliding indefinitely with respect to the core 2. Note that the pressure-sensitive element 1 and the surface layer 3 are not coupled, and the surface layer 3 can slide relative to the pressure-sensitive element 1. Further, the surface layer 3 is coupled to the core 2 via the coupling portion 4 in a region where the pressure sensitive element 1 is not disposed.

  The outputs of the pressure sensitive elements 1 of the distributed pressure sensor S are input to the detection processing device 10 as shown in FIG. The detection processing device 10 includes a calculation device 11 such as a CPU and a storage device 12 such as a semiconductor memory.

<Example 1>
Next, an embodiment of a method for detecting shearing force and slip using the above distributed pressure sensor S will be described.

  First, as shown in FIG. 3A, all the pressure sensitive elements 1 of the distributed pressure sensor S in a state where only the pressure P is applied from the target object T to the distributed pressure sensor S (reference state). .. 1 is converted into a multi-stage digital value by the calculation device 11 and recorded in the storage device 12 as a reference output state.

  After the recording of the reference output state is completed, the outputs of all the pressure sensitive elements 1... 1 of the distributed pressure sensor S are periodically observed by the calculation device 11 of the detection processing device 10. At this time, it is confirmed by surrounding geometric constraint conditions that the actual contact position is not moving. For example, when the distributed pressure sensor S of this example is used for a robot finger, the target object T is held by a plurality of fingers, the object position is constrained, and the contact position is fixed.

  Next, the outputs of the pressure-sensitive elements 1,... 1 that are periodically observed are sequentially converted into multi-stage digital values, the center of gravity of the pressure data after the digital conversion is obtained, and the position of the center of gravity and the storage device 12 Are sequentially compared with the position of the center of gravity of the digital value (pressure data) recorded in the table, and it is determined that a shear force is generated when there is a position shift of the center of gravity.

  Specifically, for example, as shown in FIG. 3B, when a downward shearing force τ is applied, the surface layer 3 of the distributed pressure sensor S is pulled downward, and the distributed pressure sensor Since a force is also applied to the pressure sensitive element 1 in the non-contact area B on the upper side of S and an output appears, the output area of the observed sensor output spreads upward with respect to the reference output state, and the center of gravity position is in the upward direction. Shift. When such a shift of the center of gravity occurs, it is determined that the shearing force τ is generated. Furthermore, since the shift of the center of gravity position is upward, it is determined that the shearing force τ is applied downward. Further, when the direction of the shearing force τ determined by such a detection process is constant, and the strength of the shearing force τ, that is, the output of the pressure-sensitive element 1 in the non-contact region B changes with time. It is determined that a slip has occurred.

  As described above, according to this embodiment, it is possible to detect shear force and slip using a distributed pressure sensor (cylindrical surface distributed pressure sensor) S using only the pressure sensitive element 1. It can be effectively used for detection at a small, substantially cylindrical portion such as a fingertip of a robot.

  In the above example, the center of gravity is obtained by converting the outputs of all the pressure sensitive elements 1... 1 of the distributed pressure sensor S into multistage digital values, but the pressure sensitive elements 1. May be converted into a two-stage digital value to obtain a centroid, and the shear force and slip may be detected based on the misalignment of the centroid. In this case, the shearing force / slip detection process can be performed in the same manner as in the case of the center of gravity.

  Further, when the determination is performed by performing two-stage digital conversion (binary observation), the positions of the upper and lower ends (element end) of the pressure-sensitive element 1 existing in the output region A in the basic detection state (FIG. 3A). Part) is recorded, and it is determined that the shearing force is generated when the pressure-sensitive element 1 generating the output moves from the end position of the recorded element, and the direction of the movement is further upward. (FIG. 3B), it may be determined that the shearing force is applied downward.

  Here, in the distributed pressure sensor S used in this example, how the shearing force is transmitted differs depending on the material of the surface layer 3. A specific example will be described below.

  First, when a material that is relatively easy to bend but hardly stretches is used as the material of the surface layer 3, the surface layer 3 is moved downward by a shearing force τ at the contact position with the target object T as shown in FIG. By pulling and sliding with respect to the core 2, the upper gap is narrowed, and a pressure is applied to the pressure-sensitive element 1 in the non-contact region B (Example 2-1).

  Further, when the material of the surface layer 3 is a hard material, the surface layer 3 can be regarded as a rigid body. Therefore, as shown in FIG. 3 (b), the surface is formed by the combined force of the pressure and the shearing force at the contact position with the target object T. The entire layer 3 is moved slightly so that pressure is applied to the pressure-sensitive element 1 in the non-contact region B (Example 2-2).

  Further, in the distributed pressure sensor S of FIG. 1, when the pressure sensitive element 1 and the surface layer 3 are combined with a flexible material sandwiched between the outer surface of the pressure sensitive element 1 and the surface layer 3, Since the pressure element 1 and the surface layer 3 cannot slide, the pressure is applied to the pressure sensitive element 1 in the non-contact region B according to the same principle as in Example 2-2 in which a hard material is used for the surface layer 3. (Example 2-3).

<Example 3>
FIG. 5 is an explanatory diagram of another embodiment of the present invention.

  This example is characterized in that shear force is detected using two distributed pressure sensors S, S. Specifically, the shear force is detected by sandwiching the columnar object T1 from both sides by the two distributed pressure sensors S, S. At this time, it is known from the geometrical constraint by the two distributed pressure sensors S, S that the contact position does not change, and therefore, when the object T1 is sandwiched between the two distributed pressure sensors S, S. The output of the pressure sensitive element 1 at the contact position is recorded, and when the output of the pressure sensitive element 1 changes thereafter, the direction of the shear force applied to the two distributed pressure sensors S and S is integrated. It can be determined that the translational force F1 (FIG. 5A) or the torsional force F2 (FIG. 5B) is applied. In this example, the detection of the shearing force by each distributed pressure sensor S, S is determined by the same processing as in the above-described <Example 1>.

  Note that, when an object is sandwiched using a plurality of distributed pressure sensors S, S, there is a possibility that a shearing force is generated due to an internal force between the sensors. The generated shearing force is detected by the method of the present invention. In such a case, the shearing force due to the external force applied to the object is detected by recording the output of the pressure-sensitive element 1 in the absence of external force when the object is sandwiched. It becomes possible.

  Here, according to the detection method of the present invention, it is possible to detect shear force and slip using a distributed pressure sensor having a simple structure that does not have a shear force detection structure. It can be effectively used for detection at a small, substantially cylindrical portion such as a fingertip of a robot hand that grips. A robot hand to which the detection method of the present invention is applied will be described below.

  First, a robot hand having a structure similar to that of a human hand has a plurality of finger mechanism portions mounted on a base corresponding to the palm, and each finger mechanism portion sequentially connects a plurality of frame portions via a plurality of joint portions. Is configured. And the actuator which act | operates each joint part is provided in the appropriate location. Such a robot hand not only grips an object with a plurality of finger mechanisms, but also includes the distributed pressure sensor (cylindrical surface distribution type sensor) S of the above-described embodiment, and a shear force by the above detection process. By determining the slippage, it is possible to realize gripping of a wide variety of objects having different hardness, material, shape, surface condition, and the like.

  6 to 9 show an example of the robot hand. FIG. 6 is a plan view (top view) of the robot hand seen from the back side of the hand, FIG. 7 is a side view seen from the thumb side, and FIG. 8 is the little finger side. FIG. 9 is a plan view (bottom view) viewed from the palm side.

  The robot hand includes a base 101 corresponding to a palm, a plurality of finger mechanisms 102, 103, 104, 105, 106 (same as human fingers in this example) mounted on the base 101, and each finger. And a drive unit that drives the mechanism units 102, 103, 104, 105, and 106. The drive unit includes a plurality of motors as actuators, and a wire (not shown) as a power transmission unit that transmits the driving force of each motor to the finger mechanism units 102, 103, 104, 105, and 106.

  The motor which is a drive part is stored in 3 planes in the base 101 part. Thumb motors 112, 113, 114 for driving the thumb finger mechanism 102 are arranged on the first plane, and index finger motors 116, 117 for driving the index finger mechanism 103 on the second plane. , 118 and a ring finger / little finger motor 121 that drives the ring finger mechanism 104 and the pinky finger mechanism 105. In addition, a motor 111 for driving the thumb finger mechanism 102 in parallel with the palm and a motor 115 for driving the index finger mechanism 103 in parallel with the palm are arranged on the third plane. Middle finger motors 119 and 120 for driving the finger mechanism 104 are disposed.

  Each finger mechanism 102, 103, 104, 105, 106 includes three joints 123, 124, 125, two frame parts 126, 127 connected by the joints 123, 124, 125, and one fingertip part. 128, each joint 123, 124, 125 is driven by the corresponding motor.

  In the robot hand having such a structure, the distributed pressure sensor (cylindrical surface distribution type sensor) S of the above-described embodiment is attached to the fingertip portion 128 and the like, and by detecting the shearing force and slip by the detection process, Smooth gripping of a wide variety of objects with different hardness, material, shape, surface condition, etc. is possible.

  Since the present invention can detect shear force and slip using a distributed pressure sensor without a shear force detection structure, for example, a finger of a robot hand that grips an object with a plurality of finger mechanisms. It can be effectively used for detection in a small, substantially cylindrical portion.

It is a figure which shows typically the structure of the distributed pressure sensor used for this invention. It is a block diagram which shows the structure of the apparatus which implements the shearing force detection method of this invention. FIG. 2 is a diagram illustrating a state (a) when pressure is applied to the distributed pressure sensor of FIG. 1 and a state (b) when pressure and shear force are applied. It is explanatory drawing of the coupling | bond part of the distributed pressure sensor of FIG. It is a figure which shows together and shows the example (a) in the case of detecting a translational force using two distributed pressure sensors, and the example (b) in the case of detecting a torsional force. It is the top view which looked at the robot hand from the back side of the hand. It is the side view which looked at the robot hand from the thumb side. It is the side view which looked at the robot hand from the little finger side. It is the bottom view which looked at the robot hand from the palm side.

Explanation of symbols

DESCRIPTION OF SYMBOLS S Distributed pressure sensor 1 Pressure sensitive element 2 Core 3 Surface layer 4 Coupling part 10 Detection processing apparatus 11 Calculation apparatus 12 Memory | storage device T Target object T1 Columnar object P Pressure (tau) Shear force F1 Translation force F2 Torsional force

Claims (4)

A method of detecting a shear force using a distributed pressure sensor in which a plurality of pressure sensitive elements are distributed on a convex curved surface and the whole of the pressure sensitive elements is covered with a surface layer,
The distributed pressure sensor is brought into contact with an object, and all output states of the plurality of pressure sensitive elements are recorded in a state where only pressure acts between the distributed pressure sensor and the contact position with the contact object is determined. Under the conditions that do not change, all outputs of the plurality of pressure sensitive elements are periodically observed, and the outputs of the pressure sensitive elements that are periodically observed are compared with the previously recorded output state. The shear force detection is characterized by examining the change in the output area and determining that the shear force is generated when the output area moves or spreads in one direction and at the same time determines the direction of the shear force. Method.   The shear force detection method according to claim 1, wherein a plurality of pressure sensitive elements in a state where only pressure acts with a contact object are converted into multi-stage digital values, recorded, and periodically observed. The output of multiple pressure-sensitive elements is converted into multi-stage digital values to obtain the center of gravity, and the center of gravity is compared with the center of gravity of the digital value of the recording. A shear force detection method characterized by determining the direction of the shear force at the same time that it is determined that the phenomenon has occurred.   The shear force detection method according to claim 1, wherein a plurality of pressure sensitive elements in a state in which only pressure acts with a contact object are converted into two-stage digital values, recorded, and periodically observed. The output of a plurality of pressure-sensitive elements is converted into a two-stage digital value to obtain a centroid, and the centroid position is compared with the centroid position of the digital value of the recording, and there is a misalignment of the centroid A method for detecting a shearing force, characterized in that a shearing force is generated and at the same time the direction of the shearing force is determined. A method for detecting slip on the basis of information on the shear force obtained by the shear force detection method according to claim 1, wherein the direction of the shear force determined by the shear force detection method is constant. A slip detection method characterized in that it is determined that slip occurs when the strength of the shear force changes with time.

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