JPS63149502A - Angle detector - Google Patents

Abstract

PURPOSE:To achieve the miniaturization and wt. reduction of a sensor and to detect the signal relating to an angle of rotation by constituting one end of a bimorph type piezoelectric sheet as a fixed end and constituting the other end thereof as a free end on which bending force acts, and by taking out piezoelectricity between the electrodes thereof. CONSTITUTION:A piezoelectric sheet 2 is provided over a fixed member 4 and a movable member 5, and the member 5 is connected to the end part of the member 4 in a freely revolvable manner so as to be pivoltally supported by a pin 6. Further, the sheet 2 is formed into a bimorph type wherein thin piezoelectric films 8 are provided to both surface of a flexible support plate 7. One end of the support plate engaged with and fixed to the member 4 to become a fixed end 7a and the other end thereof is extended along the member 5 to becomes a free end 7b. The film 8 is composed of a polymer piezoelectric material and electrodes each composed of a conductive metal membrane are applied to both surfaces of the film 8 by vapor deposition. When the sheet 2 is bent by the revolution of the member 5, the film 8 generates piezoelectricity and, therefore, the piezoelectric charge quantity thereof is led out from the electrodes and subjected to predetermined operational processing to make it possible to detect the angle of rotation or rotational speed of the free end 7b.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) Kokumei relates to an angle detection device that detects a signal related to a rotation angle using a polymeric piezoelectric material.

(Prior Art) In general, tachometer generators, encoders, and the like are well known as angle detection devices that detect rotation angles and rotation speeds of various rotating bodies. This tachogenerator rotates a rotor in a magnetic field in synchronization with a rotating body, and detects the rotation angle and rotation speed by utilizing the fact that the voltage induced thereby is proportional to the rotation speed.

Furthermore, the encoder processes a digital signal synchronized with the rotating body using a counter to detect the rotation angle and rotation speed.

(Problems to be Solved by the Invention) However, in addition to the angle detection device described above, the tachogenerator requires a rotating magnet or coil, and the encoder requires means for deriving a digital signal. There was a problem in that it was large and heavy.

In particular, in recent years, work robots I. have been actively developed and improved, and in this case, it is necessary to realize high-speed cooperative movements in multi-jointed structures such as robot fingers. However, if the above-mentioned tachogenerator and encoder are applied to this multi-jointed structure, the entire structure becomes large and the W
There is a problem that it becomes ffi. Therefore, there has been a strong desire for a small, lightweight angle detection device.

In view of this, the present invention has been made by the inventors to clarify the point that a polymer piezoelectric material outputs piezoelectricity proportional to bending, and to detect a signal related to the rotation angle using this piezoelectricity. The purpose of this is to reduce the size and weight of the device.

(Means for Solving the Problems) In order to achieve the above object, the means taken by the present invention are as shown in FIGS. 1 and 2. A sheet (2) is formed. One end of the piezoelectric sheet (2) is a fixed end (7).
In a), the other end is configured as a free end (7b) on which bending force acts.

The structure is such that the piezoelectricity between the polarizations of this piezoelectric sheet (2) is extracted.

(Function) According to the invention, when a load acts on the free end (7b) of the piezoelectric sheet (2) and the piezoelectric sheet (2) bends, a piezoelectric phenomenon occurs. The piezoelectricity of the piezoelectric sheet (2) generated by this piezoelectric phenomenon, that is, the piezoelectricity vJFI is extracted. The rotation angle and rotation speed of the free end (7b) are derived from this amount of charge.

Therefore, since the piezoelectric sheet (2) has a polymeric piezoelectric material as its main component, it can be downsized, and
Weight reduction can be promoted.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

As shown in Figures 1 and 2, (1) is an angle detection device that detects the rotation angle and rotation speed of a robot's joints, etc., and a signal processing means (3) is connected to a piezoelectric sheet (2). It is composed of

The piezoelectric sheet (2) has a fixed member (4) and a movable member (5).
), and the movable member (5) is rotatably supported by a pin (6) at the end of the fixed member (4). Further, the piezoelectric sheet (2) is formed into a bimorph shape by providing thin piezoelectric films (8) on both sides of a flexible support plate (7), and the support plate (7) is made of synthetic resin such as acrylic. The supporting plate (7) is formed of a material such as phosphor bronze, steel plate, etc., so that it can be easily bent.One end of the support plate (7) is fitted and fixed to the fixed member (4) to become a fixed end (7a), and the other end is a movable member. (5) and is extended along the free end (7
1) ). The free 0N (7b) is restrained by a restraint member (9) provided on the movable member (5), and the restraint member (9) is configured such that two bars sandwich the free end (7b) from both sides. The restraining member (9) restrains the free end (7b) only in the movable direction of the movable member (5),
The support plate (7) is slidable in the longitudinal direction of the support plate (7), and the piezoelectric sheet (2) is provided so that only bending force is applied to the piezoelectric sheet (2) by rotation of the movable member (5). .

Further, a motor (1o) is connected to the bin (6),
The movable member (5) is moved by the motor (10) to the fixed member (4).
).

As shown in FIG. 3, the piezoelectric film (8) is made of a polymeric piezoelectric material, and conductive metal thin film electrodes (11), (11
) is formed by vapor deposition, and the piezoelectric sheet (2) is formed into a bimorph type. The piezoelectric film (8) is made of polyvinylidene fluoride (PVDF) or vinylidene-fluoride-trifluoroethylene copolymer (VDF/T
The piezoelectric film (8a) shown in FIG. 4 is formed by adding a powder solid material such as piezoelectric ceramic to the base material of the above-mentioned polymeric piezoelectric material.

The piezoelectric film (8) was formed using this polymeric piezoelectric material because its piezoelectric properties are compared with those of inorganic piezoelectric materials such as quartz as shown in Table 1.
9 R'A processing etc. is extremely easy and it can be manufactured at low cost.

Moreover, the reason why the piezoelectric film (8) is attached to both sides of the support plate (7) as shown in FIG.
The thinner the film, the greater the piezoelectric effect, but piezoelectric films made only of polymer materials such as PVDF (
8) has low rigidity and cannot be used alone with a piezoelectric film (8) with a thickness of, for example, 10 μm.
) to maintain bending rigidity. On the other hand, as shown in FIG. 4, in a piezoelectric film (8a) using a composite piezoelectric material to which a solid such as piezoelectric ceramic is added,
The piezoelectric film (8a) itself is solid and rigid without deteriorating its piezoelectricity, and the support material (7) can be omitted and processed into a membrane-like structure, and the electrode ( A bimorph type structure is constructed by connecting a piezoelectric film (8a) via a film 11).

Next, the piezoelectric sheet (2) is moved to the rotation 01 of the movable member (5).
When bent, the piezoelectric film (8) generates piezoelectricity, and the relationship between this piezoelectricity and bending will be explained.

As shown in Figure 5, two piezoelectric films (8), (8
) constitutes a bimorph type, so when bending is applied, the center electrode (11) surface becomes a neutral plane where neither tension nor compression acts, while the upper surface is subjected to tensile force and the lower surface is subjected to compressive force. , a charge I appears on the surface of each piezoelectric film (8), resulting in polarization. Then, a potential difference (voltage) is generated between the potential of the center electrode (11) and the potential of the electrode 1 (i(11)) on both end surfaces (between a and b), and this potential difference causes bending distortion, that is, the curvature 1/ ′ρ. Therefore, the relationship between this voltage and curvature is given by the following equation, where v=−
g・m・(1/ρ)...■V: Voltage (V) g: Piezoelectric constant (C/N> m: Thickness of piezoelectric film IIlm) ρ: Radius of curvature (
m) k: Constant of proportionality. The experimental results to verify this theoretical result are the 6th
As shown in the figure, it is clear that the voltage V is proportional to the curvature 1/ρ.

Furthermore, as shown in FIG. 7, the piezoelectric film (8)
In the experimental results using a servo system to compare the output signal @P and its integral signal ■ with the output signals 8G and M of a conventional tacho generator and potentiometer, When given as a function signal S, the output signal P of the piezoelectric film (8) and its integral signal ■
It is clear that G corresponds to the output signals G and M of a tacho generator or the like.

In addition, the bimorph structure piezoelectric films (8) and (8)
), as shown in Fig. 8, when compressive force is applied by force acting from both sides, the amount of electricity is canceled out between the electric machine (11) in the center and the electrodes (11) on both end faces, and the rain and snow ff1 (11 ),
(11) No potential difference occurs between (a and b).

Therefore, there is no output for tension and compression, and they are compensated. Furthermore, the same effect as described above occurs even when the temperature changes, and there is no output, and temperature compensation is performed.

Next, the piezoelectric sheet t-(2> song: 4?, 1/ρ
The relationship between the rotation angle θ of the free end (7b) and the rotation angle θ of the free end (7b) will be explained based on the cantilever beam M shown in FIG. Since the free end (7b) of the piezoelectric sheet (2) rotates around the pin (6) of the movable member (5), the free end of the beam M is displaced by δ in the concentration direction ff1W and rotates around the pin (6). Rotate by θ. And beam A
The length of 91. Assuming that the quality of the fixed end and the bottle (6) is intersection 2, the bending of beam A is expressed by the following formula according to the Bernoulli-Euler law: 1/ρ-M/E I...■M
: Bending moment E: Young's modulus, r: Sectional quadratic 7-men]. The displacement δ and rotation angle θ are expressed by the following formula, δ=βWQ+3/El...■tan
θ=δ/(R++Qz)−■ β: Becomes a constant. Then, if we transform the above formulas ■ to ■, we get 1/
ρ − (1+ Q' 2 / 11 dens)
tan θ /β G+...■, and this β9. Since Q+, 1!2 is constant, 0
The formula is expressed as follows.

1/ρ−ktanθ...■:
Constant Therefore, as mentioned above, from the formula 0, the voltage V, that is, the charge ff1Q output by the piezoelectric film (8), and the curvature 1/ρ have the following relationship, so Q(Xj/ρ...00 formula From the relationship, Q Oc1/ ρCX:tanθ...
・■, and the amount of piezoelectric charge Q of the piezoelectric film (8) is proportional to the rotation angle θ of the free end (7b).

At this time, since the output signal of the piezoelectric film (8) extracts the charge, it becomes a differential value as shown in FIG. 7, so the equation 0 becomes dQ/dtccd (1/p) / dtocsec
2 θdθ/ d t ... is transformed into ■.

Next, to explain the signal processing means (3), the signal processing means (3) processes the output signal of the piezoelectric sheet (2), that is, the piezoelectricity (charge color Q) of the two piezoelectric films (8). The rotation angle θ and the rotation speed ω of the free end (7b) are calculated based on the relationship expressed by Equation 0.

As shown in FIG. 2, the signal processing means (3) is constructed by linking an operational amplifier (21) with an integral calculation circuit (22) and a leap number operator circuit (23). And an electrode (11) on the support plate (7) side of the piezoelectric film (8)
is grounded, and the outer electrode (11) on which a tensile or compressive force acts is connected to the negative terminal of the operational amplifier (21). The positive terminal of the operational amplifier (21) is grounded, and outputs the charges on the outside of the two piezoelectric films <8> with reference to the charge on the central electrode. At this time, the amount of charge taken out is taken out from the tension side and compression side, so the curvature is 1/'ρ
J5 is twice that of J5, and the differential value with respect to time is d(1/ρ)/dt.

The integral calculation circuit (22) integrates the differential signal of the operational amplifier (21), and calculates and outputs the rotation angle θ from the inverse function of equation 0. Further, the function calculation circuit (23) calculates a cosine function etc. from the differential signal of the operational amplifier (21) based on equation 0, calculates and outputs the rotational speed ω (=dθ/dt>).

Therefore, when the movable member (5) is rotated by the motor (10) around the bottle (6) on the extension of the fixed member (4) (see the chain line in Figure 2), the free end (7b) of the piezoelectric sheet (2) ) rotates while being restrained by the restraining member (9) only in the rotational direction.

This rotation causes charges to appear on the surfaces of both piezoelectric films (8), (8).

As shown in equation 0 and Figure 6, this charge mQ has a curvature of 1/ρ
Since it is proportional to the amount of charge, the operational amplifier (21)
Derive it as After that, the output signal @(differential value d(1/ρ)/dt) of this operational amplifier (21) is sent to the integral calculation circuit.
22) and a function calculation circuit (23) to calculate and output the rotation angle θ and rotation speed ω. Thereby, the rotation angle θ and rotation speed ω of the movable member (5) are detected.

Since the piezoelectric film (8) is made of a polymeric piezoelectric material or the like, it is lightweight and small, and an ultra-lightweight and ultra-small sensor is realized.

Next, an example of a shell body in which the angle detection @position (1) described above is applied to a robot will be described based on FIGS. 10 to 13.

As shown in FIGS. 10 and 11, (41) is the robot's hand, (42), (42), . . . are fingers provided on the hand (41), and a leg (42).

An IC board (43) is held between (42).

Above (42) is the proximal part (44) and the intermediate part (45)
and a distal portion (46) are successively connected via a joint (47). The intermediate part (45) becomes the supporting part, and conversely, the intermediate part (45) becomes the proximal part (4
4), and the distal end portion (46) is a movable portion relative to the intermediate portion (45). The above joint (4
7) each part (44), (45) by bottle (6).

(46) is rotatably supported, and although not shown, a motor (10) is connected to the pin (6) to rotate the intermediate portion (45) and the tip portion (46). It is configured as follows.

A piezoelectric sheet (2) is provided between the base end portion (44) and the intermediate portion (45), and between the intermediate portion (45) and the tip portion (46).

As mentioned above, the piezoelectric sheet (2) has a fixed end (7a
) is fixed to the proximal part (44) or the intermediate part (45), and the free end (7b) is attached to the intermediate part (44) through the restraining member (9).
45) or the distal end portion (46) so as to be restricted only in the direction of rotation.

Further, as shown in FIGS. 12 and 13, the signal processing means (3) connected to the piezoelectric sheet (2) has an electrode (11) on the outside of both piezoelectric films (8), <8>. It is connected to an operational amplifier (21) to extract piezoelectricity (charge). The operational amplifier (21) is connected to the integral calculation circuit (22) and the function calculation circuit (23), and the operational amplifier (21) is connected to the integral calculation circuit (22) and the function calculation circuit (23).
) is the differential signal d (1/
ρ)/dt is integrated over time t to calculate the curvature 1/ρ and output it to the inverse rlJ@impairing circuit (24). The inverse function calculation circuit (24) calculates the rotation angle θ from jan'(1/ρ) based on the formula 0, and connects the amplifier (25) and the function calculation circuit (2
3) is output.

The function calculation circuit (23) constitutes a differential calculation circuit with a cosine function circuit (26) and a multiplication circuit (27),
In other words, the 0 equation that is differentiated from the 0 equation is transformed as follows, dθ/dt(X-cos 2 θ, d (1/f)
) /dt-...◎From this formula 0, rotation speed ω(=dθ
/dt) is calculated. Therefore, the above cosine function circuit (
26) calculates the cosine function CO52θ from the rotation angle θ of the inverse function calculation circuit (24), and the multiplication circuit (27) calculates the cosine function cos 2 θ and the differential function d( of the operational amplifier (21)).
1/ρ) and /dt to equalize the rotational speed ω and output it to the amplifier (28).

Furthermore, the output signal θ of each of the above amplifiers <25), (28),
ω is compared with the lower command value in the subtraction circuit (29), and this comparison value is fed back to the motor (10) via the amplifier (30) to control the rotation of each part (45) and (46). It is configured as follows.

Next, the above control (42) will be explained.

For example, when the tip portion (46) is rotated by the motor (1o), the piezoelectric sheet (
2) The free end (7b) is a restraining member (9) and the tip part (4)
6), and both piezoelectric films (8), (8) are bent by bending force. And both piezoelectric films (8).

In (8), a charge amount Q proportional to the curvature 1/ρ is generated. This charge ff1Q is extracted as a differential value by an operational amplifier (21). Next, the differential signal d (1/ρ)/dt of the operational amplifier (21) is sent to the integral calculation circuit (22).
Then, an inverse function calculation circuit (24) performs integration and inverse function processing to calculate the rotation angle θ.

On the other hand, the angle signal θ of the inverse function calculation circuit (24) is converted into a cosine function cos 2θ by the cosine function circuit (26), and then the differential signal d (1/ρ )/d is multiplied to calculate the rotational speed ω.

After that, the angle signal θ and the speed signal ω are sent to the amplifier (25), (
28> and is compared with the lower command value, and fed back to the motor (1o) via the amplifier (30), thereby controlling the rotation of the tip portion (46).

14 and 15 show another piezoelectric sheet (2a), in which the piezoelectric sheet (2) of the previous embodiment had piezoelectric films (8), (8) provided on both sides of the support plate (7). Instead, two piezoelectric films (8), (8) are superimposed on one side of the support plate (7), and the two piezoelectric films (8),
An electrode (11) is provided between (8). The rest is the same as the previous embodiment.

FIG. 16 shows another embodiment, and FIGS. 12 and 13 are expressed using analog circuits, but as shown in FIG.
<A/D Converter), the circuit section (32) shown by the dashed line in Fig. 16 is processed by a computer, and the output is converted back to analog using a digital-to-analog converter (33) (D/△C0nverter). The motor operating voltage may be applied to the amplifier (30) by using the amplifier (30), and an operation similar to that shown in FIG. 13 can be realized.

In addition, the restraining member (
9) is composed of two bars, but if it rotates in only one direction, one bar may be used.In addition to the bar, it may also be composed of a plate, an engagement protrusion, an engagement groove, etc. In short, it is sufficient if it is movable in the longitudinal direction and restricted only in the direction of rotation.

Further, the angle detection device (1) is connected to the fingers (42) of the robots 1 to 1.
), but it is of course possible to provide it at other various joints, and furthermore, it may be provided at various rotating parts in measuring human body motion.

(Effects of the Invention) As described above, according to the angle detection device of the present invention, since the bimorph piezoelectric sheet is formed of a polymeric piezoelectric material,
Since the rotation angle, rotation speed, etc. can be derived from piezoelectricity, it is possible to omit magnets and coils like in conventional tachogenerators, and the rotation signal extraction part like in encoders, making it extremely small and lightweight. can do. Therefore, since it can be provided even in a narrow space such as a robot's finger, these various controls can be performed in a small space.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is a perspective view showing the mounting state of the piezoelectric sheet, FIG. 2 is a schematic configuration diagram of the angle detection device, FIG. 3 is an enlarged view of the piezoelectric sheet, and FIG. Enlarged view of other piezoelectric films, Figure 5 is a schematic diagram of a piezoelectric sheet showing the piezoelectric phenomenon, Figure 6 is a diagram of the relationship between voltage and curvature, and Figure 7 is the output waveform of the piezoelectric sheet, tachogenerator, and potentiometer. Fig. 8 is a schematic diagram of a piezoelectric sheet showing other piezoelectric phenomena, Fig. 9 is a plan view of a cantilever beam showing the relationship between curvature and rotation angle, and Figs. 10 to 13 are applied to a robot. 10 is a side view of the robot's hand, FIG. 11 is a plan view of the finger, FIG. 12 is a block diagram of the angle detection device, FIG. 13 is a block diagram of the same circuit, and FIG. Figure 14 is a plan view showing another piezoelectric sheet, and Figure 15 is Figure 14B.
FIG. 16 is a circuit block diagram showing another example of the angle detection device. (1)...Angle detection device, (2), (2a>...Piezoelectric sheet, (3)...Signal processing means, (6)...Bin, (7)...Support plate, (7a)...Fixed end, (7
b)...Free end, (8), (8a)...Piezoelectric film, (9)...Restriction member. Figure 4 Figure 3 Figure 9 Figure 7 Figure 8 Figure 2n Figure 6 Figure 5

Claims (1)

[Claims] (1) Equipped with a bimorph piezoelectric sheet (2) mainly composed of a polymeric piezoelectric material, one end of which is a fixed end (7a), and the other end is a free end (7a) on which bending force acts. 7
An angle detection device configured as in b), characterized in that it is configured to extract piezoelectricity between the polarizations of the piezoelectric sheet (2).