JPH06138019A - Method for detecting static friction coefficient and its detector - Google Patents

Abstract

PURPOSE:To provide a method for detecting a static friction coefficient and its detector capable of directly detecting the static friction coefficient of an object to be detected. CONSTITUTION:A resilient member RM is brought into contact with an object to be detected, load is vertically and horizontally simultaneously given, vertical pressure for the resilient member RM is detected with a vertical pressure detection means NP and shearing force is found out with a shearing force detection means SF. In addition, a stick slip of the resilient member RM is detected with a stick slip detection means SS. Detection values detected with the vertical pressure detection means and the shearing force detection means are read in a storing means MM at specified time intervals. When the stick slip occurs on the resilient member and is detected with the stick slip detection means SS, in a static friction coefficient operation means CF the last vertical pressure detection value and the last shearing force detection value transmitted from the storing means are taken out, the latter is divided by the former and the friction coefficient is found.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a static friction coefficient detection method and a static friction coefficient detection apparatus, and more particularly to a static friction coefficient detection method and static friction coefficient detection method for directly determining the static friction coefficient by contacting an object to be detected and detecting the acting force and slippage. The present invention relates to a coefficient detection device.

[0002]

2. Description of the Related Art Conventionally, when manipulating a gripped object with a robot hand, the grip force of the robot hand has been set according to an external force applied to the object, assuming a coefficient of static friction μ. In order to set an appropriate gripping force for the robot hand, it is necessary to detect the static friction coefficient of the gripped object. Therefore, there is an urgent need to develop a sensor for detecting the coefficient of static friction, and the inventor of the present application also proposes a sensor for coefficient of static friction.

[0003]

However, in the conventional static friction coefficient sensor, there are various restrictions such as that the surface of the object to be detected is flat and uniform. Therefore, the application range of the static friction coefficient sensor is narrow, and the sensor cannot be mounted on a robot hand having various surface shapes as it is.

Therefore, an object of the present invention is to provide a static friction coefficient detecting method and a static friction coefficient detecting apparatus which can directly detect the static friction coefficient of an object to be detected.

[0005]

In order to achieve the above object, the static friction coefficient detecting method according to the present invention makes an object to be detected contact an elastic member and simultaneously applies a load to the elastic member in a vertical direction and a horizontal direction. The vertical pressure and the shearing force on the elastic member are detected, the detected values are stored at predetermined time intervals, and when the stick-slip of the elastic member is detected, the vertical pressure and the shearing force are each detected last time. Is taken out and the static friction coefficient is calculated based on the previous detected values.

The static friction coefficient detecting device of the present invention is shown in FIG.
As shown in the outline of the configuration, an elastic member RM that is in contact with an object to be detected (not shown) and to which a load is applied simultaneously in the vertical and horizontal directions, and a vertical pressure that detects the vertical pressure on the elastic member RM. Detection means NP and elastic member RM
Shear force detecting means SF for detecting the shear force with respect to, the stick slip detecting means SS for detecting the stick slip of the elastic member RM, the vertical pressure detecting value of the vertical pressure detecting means NP, and the shear force detecting value of the shear force detecting means SF. Is read at a predetermined time interval, and when the stick-slip detecting means SS detects a stick-slip of the elastic member RM, the vertical pressure detecting means NP is read from the storing means MM.
Of the previous vertical pressure detection value and the previous shear force detection value of the shear force detection means SF, and divides the previous shear force detection value by the previous vertical pressure detection value C.
And F.

The above-described static friction coefficient detecting device can be configured in various modes as exemplified below. (A) As the elastic member, a substrate made of an elastic polymer material and a pressure sensitive member arranged on the substrate with a predetermined gap are provided, and the pressure sensitive member and the substrate are respectively provided with the pressure sensitive member. A pressure sensation that includes a pair of electrodes whose gap changes according to the contact of the object to be detected with the member, and detects a vertical pressure applied to the pressure sensitive member in the vertical direction based on the change in the capacitance between the pair of electrodes. A sensor unit and a plurality of strain gauges attached on the substrate outside the pressure sensor unit,
A static friction coefficient detecting device comprising a shearing force applied to the substrate in a horizontal direction and a shift sensor for detecting stick-slip. (B) The substrate is made of a polyimide film, and the pressure sensitive portion is made of silicon rubber. (C) A groove is formed around the pressure sensor section on the substrate,
Inside the groove, a pair of strain gauges are arranged at symmetrical positions which are orthogonal to each other with the pressure sensor portion as the center. (D) A capacitance-frequency conversion means for converting a change in capacitance between the pair of electrodes into a change in frequency is provided, and a pair of strain gauges arranged at symmetrical positions orthogonal to each other are included. Configure a set of bridge circuits.

[0008]

In the above static friction coefficient detecting method, first, the object to be detected is brought into contact with the elastic member, and a load is applied simultaneously to the elastic member in the vertical and horizontal directions. At this time, the vertical pressure and shearing force to the elastic member are applied. Is detected and each detected value is stored at a predetermined time interval. Then, when the stick slip of the elastic member is detected, the previous detection values of the vertical pressure and the shearing force are taken out, and the shearing force is divided by the vertical pressure based on these detection values to obtain the static friction coefficient.

Further, in the static friction coefficient detecting device constructed as shown in FIG. 1, when the elastic member RM contacts an object to be detected (not shown) and a load is applied simultaneously in the vertical and horizontal directions. The vertical pressure detection unit NP detects the vertical pressure on the elastic member RM, and the shear force detection unit SF detects the shear force on the elastic member RM. Moreover, the stick-slip of the elastic member RM is detected by the stick-slip detecting means SS. The vertical pressure detecting means NP and the shearing force detecting means SF
The detection value detected by is read into the storage means MM at a predetermined time interval. Then, when a stick slip occurs in the elastic member RM and this is detected by the stick slip detecting means SS, the static friction coefficient calculating means CF
In, the previous vertical pressure detection value and the previous shearing force detection value are retrieved from the storage means MM, and the latter is divided by the former to obtain the static friction coefficient μ. Thus, the value of the coefficient of static friction μ can be displayed in various formats, for example via an output device (not shown).

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 2 and 3 relate to an embodiment of the static friction coefficient detecting device of the present invention, and FIG. 2 shows the structure of the sensor FS.
A pressure sensor section FS1 and a shift sensor section FS2 are formed on a base film 1 having a polyimide film as a base material.

First, the pressure sensor FS1 has a side wall 1a extending from the surface of a disk-shaped polyimide base film 1 so as to surround a predetermined section, and is formed into a circular container shape. The side wall 1a is surrounded by the side wall 1a. An air gap 2 is formed in the. The side wall 1a is formed by first embossing a rough convex shape on the surface of the polyimide film and then by precision etching a fine concave shape. A bottom electrode 3 is formed by vapor-depositing aluminum on a bottom surface of a portion surrounded by the side wall 1a, and a notch 1c is formed in the side wall 1a to take out a lower wiring 4 connected thereto.
Is provided. The side wall 1a is not limited to a circular shape, but may be formed in a container shape of other shapes such as a square shape.

The upper electrode 5 is arranged so as to cover the portion surrounded by the side wall 1a. That is, aluminum is vapor-deposited on one surface of the pressure sensitive member 8 made of a circular flat plate-shaped silicon rubber to form the upper electrode 5,
The upper electrode 5 is bonded to the upper end surface of the side wall 1a with an adhesive 7 via a dielectric 6. The dielectric 6 is provided to prevent a short circuit between the lower electrode 3 and the upper electrode 5, and is formed of a phenol resin solution in this embodiment. As the adhesive agent 7, a cyanoacrylate adhesive agent (instantaneous adhesive agent) is adopted. Either the upper wiring (not shown) electrically connected to the upper electrode 5 or the lower wiring 4 is grounded.

On the other hand, the displacement sensor FS2 has a groove 1b formed on the outer periphery of the side wall 1a on the base film 1, and has strain gauges 11 to 14 attached to the bottom surface thereof. That is, as shown in FIG. 3, a pair of strain gauges 11 and 12 and a pair of strain gauges 13 and 14 are arranged at symmetrical positions which are orthogonal to the radial direction, respectively, and are arranged according to the displacement in the Y direction and the X direction, respectively. The resistances R1, R2 and R3, R4 are changed.

The outputs of the pressure sensor unit FS1 and the displacement sensor unit FS2 are input to the electronic control unit 50, where input / output processing, storage and calculation are performed and output to the output unit 60. The electronic control unit 50 is configured as shown in FIG. 3, and includes Schmitt trigger inverters 21 and 22, a counter 23, bridge circuits 31 and 41, operational amplifiers 32 and 4.
2, amplifiers 33 and 43, A / D converters 34 and 44,
Band pass filters 35 and 45, comparators 36 and 4
6, a microprocessor 51, a memory 52,
Built-in timer 53, interface 54, etc.
The counter 23, the A / D converters 34 and 44, and the output device 60 are connected to the interface 54.

As described above, the output of the pressure sensor section FS1 changes in capacitance, but the capacitance value is as small as several pF, and the circuit must have low loss. Therefore, as shown in FIG. 3, the CMOS Schmitt trigger inverter 21 is used. The period T of the oscillation pulse of this circuit is theoretically obtained by the following equation. T = 2 (logV _p −logV _n ) CR where V _p is the high level threshold voltage of the Schmitt trigger and V _n is the low level threshold voltage. When the power supply voltage is V _cc (V _p + V _n = V _cc ) is satisfied. The output signal is taken out and transmitted through the buffer of the Schmitt trigger inverter 22. The Schmitt trigger inverter 22 is provided to prevent the counter 23 connected in the subsequent stage from affecting the oscillation cycle thereof. The pulse period T with respect to the capacitance C is substantially proportional to the capacitance C of the pressure sensor unit FS1 with respect to a vertical load (indicated by an arrow N in FIG. 2).
The characteristics of are as shown in FIG.

On the other hand, the strain gauge 1 of the shift sensor FS2
One end of 1 to 14 is grounded and the other end is connected to resistors R5 to R8 as shown in FIG.
1, 41 are configured. These bridge circuits 3
A power supply voltage V _cc is applied to 1 and 41, and their outputs are taken out as voltages Ex and Ey via operational amplifiers 32 and 42, and these are amplified by amplifiers 33 and 43, respectively, and A /
It is converted into a digital value by the D converters 34 and 44.
That is, the x component and the y component of the shearing force F applied to the base film 1 of the displacement sensor unit FS2 by the voltages Ex and Ey.
The components are obtained as (Fx = k · Ex) and (Fy = k · Ey). However, k is a coefficient obtained from an experiment.
Thus, the vertical load (N) is uniformly applied to the entire surface of the pressure sensitive member 8.
The characteristics when a shearing force (indicated by an arrow F in FIG. 2) is applied in the horizontal direction in the state of being applied are as shown in FIG.

The operational amplifiers 32 and 42 are connected to the bandpass filters 35 and 45 and the comparators 36 and 46, respectively. Here, the output voltages of the operational amplifiers 32 and 42, which are the outputs of the bridge circuits 31 and 41, have the characteristics shown in FIG. 7 at the time of stick slip. That is, after stick-slip occurs at the portion indicated by the arrow in FIG. 7, the output voltage of the operational amplifiers 32 and 42 includes a frequency component of about 10 Hz caused by the stick-slip. Therefore, if the operational amplifiers 32 and 42 are connected to the bandpass filters 35 and 45 so that only the output of the frequency near 10 Hz can pass, the stick slips are generated by the comparators 36 and 46 when the output of this band is present. To be detected. In this case, for example, when the load on the pressure sensitive member 8 is increased, stick-slip occurs, and a large load is applied to the pressure sensitive member 8 in advance to make it in a slip state, and the pressure is gradually reduced. Will cause the stick-slip to stop, but in any case, "stick-slip detection"
Is treated as.

Then, in the electronic control unit 50, a series of arithmetic processing for obtaining the coefficient of static friction is performed according to the program executed by the microprocessor 51, and is output to the output unit 60. This program comprises, for example, the routine shown in FIG. 4, and is repeatedly executed at a predetermined time interval, that is, a predetermined calculation cycle. Incidentally, in FIG. 4, general processing such as initialization is omitted.

First, in step 100, the x component (Fx _n ) and the y component (Fy _n ) of the n-th shearing force are calculated based on the outputs of the A / D converters 34 and 44, and the memory 5
Read in 2. Then, in step 200,
The n-th vertical pressure N _n is calculated based on the output of the counter 23 and read into the memory 52. Next, step 3
At 00, stick-slip is determined based on the outputs of the comparators 36 and 46.

If no stick slip is detected in step 300, the process returns to step 100 and the next (n +
1) The reading is performed for the first time, but if stick-slip is detected, the process proceeds to step 400, and the previous time (that is, (n
The x component (Fx _(n-1) ) and the y component (Fy _(n-1) ) of the ₍ -1) th) shearing force are fetched from the memory 52, and an operation for combining the two components is performed. Is required. Subsequently, the routine proceeds to step 500, where the previous vertical pressure N _(n-1) is made the vertical pressure N. Then these values are
It is divided (F / N) by 00 to obtain the static friction coefficient μ. Since the time interval of this calculation processing, that is, the calculation cycle is set to a time sufficiently shorter than the vibration cycle of the sensor FS, there is no need to worry about noise due to vibration.

Thus, according to this embodiment, the pressure sensitive member 8
When the vertical pressure N and the shearing force F are detected by the pressure sensor unit FS1 and the displacement sensor unit FS2 in a state in which is in contact with the detection target member (not shown), and a stick slip is detected in the electronic control unit 50. The static friction coefficient μ is calculated based on each detected value. That is, the coefficient of static friction μ of the object to be detected can be directly detected. Moreover, since the base film 1 and the pressure sensitive member 8 are respectively formed of polyimide and silicon rubber which are elastic members, even if the support surface of the robot hand or the like to be mounted is a curved surface, the detection accuracy can be ensured without impairing the detection accuracy. Can be attached to.

[0022]

Since the present invention is configured as described above, it has the following effects. That is, according to the static friction coefficient detecting method of the present invention, the detected values of the vertical pressure and the shearing force simultaneously applied to the elastic member are stored at predetermined time intervals, and the stick slip of the elastic member is detected. At this time, the previous detection values of vertical pressure and shear force are taken out, and the static friction coefficient is calculated based on these detection values.
It can be detected with good detection accuracy.

Further, in the static friction coefficient detecting device of the present invention, when the stick-slip of the elastic member in contact with the object to be detected is detected by the stick-slip detecting means, the static friction coefficient calculating means detects the previous vertical pressure detection value. Since the static friction coefficient is calculated based on the shear force detection value, the static friction coefficient of the detection target object can be directly detected, and good detection accuracy can be secured. Moreover, since the elastic member can be appropriately bent and the static friction coefficient can be detected in that state, the elastic member can be properly mounted without being affected by the shape of the supporting surface to be mounted.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a static friction coefficient detecting device of the present invention.

FIG. 2 is a vertical cross-sectional view of a sensor in the static friction coefficient detecting device according to the exemplary embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a static friction coefficient detection device according to an exemplary embodiment of the present invention.

FIG. 4 is a flowchart showing the processing of the electronic control unit in the embodiment of the present invention.

FIG. 5 is a graph showing a capacitance characteristic of a pressure sensor unit with respect to vertical pressure according to an embodiment of the present invention.

FIG. 6 is a graph showing an output voltage characteristic with respect to a shearing force of the displacement sensor unit in the embodiment of the present invention.

FIG. 7 is a graph showing the situation of stick-slip occurrence in an example of the present invention.

[Explanation of symbols]

 1 Base Film (Elastic Member) 1a Bottom, 1b Groove, 1c Notch 2 Air Gap 3 Lower Electrode 4 Lower Wiring 5 Upper Electrode 6 Dielectric 7 Adhesive 8 Pressure Sensitive Member (Elastic Member) 11-14 Strain Gauge 21, 22 Schmidt Trigger inverter 31,41 Bridge circuit 50 Electronic control device 60 Output device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Imai 2003-2003 Nakahira 5-chome, Tenpaku-ku, Nagoya-shi, Aichi

Claims (2)

[Claims] 1. A detection target object is brought into contact with an elastic member, and a load is simultaneously applied to the elastic member in a vertical direction and a horizontal direction to detect a vertical pressure and a shearing force with respect to the elastic member. Is stored at a predetermined time interval, and when the stick slip of the elastic member is detected, the previous detection values of the vertical pressure and the shearing force are taken out, and the static friction coefficient is calculated based on the detection values of the previous time. Coefficient detection method. 2. An elastic member, which is in contact with an object to be detected and to which a load is applied simultaneously in the vertical and horizontal directions, a vertical pressure detecting means for detecting a vertical pressure on the elastic member, and a shearing force for the elastic member. Shearing force detection means,
Stick-slip detection means for detecting stick-slip of the elastic member; storage means for reading the vertical pressure detection value of the vertical pressure detection means and the shear force detection value of the shear force detection means at predetermined time intervals; When the detection means detects the stick-slip of the elastic member, the previous vertical pressure detection value of the vertical pressure detection means and the previous shear force detection value of the shear force detection means are retrieved from the storage means to detect the previous shear force. A static friction coefficient detecting device comprising: static friction coefficient calculating means for dividing the value by a previous vertical pressure detection value.