Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L1/00—Measuring force or stress, in general
  • G01L1/16—Measuring force or stress, in general using properties of piezoelectric devices
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
  • G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge

Definitions

• the invention relates to a bending sensor device and more particularly to a bending sensor device based on elements made of piezoelectric polymer material.
• the invention finds applications in the design of a set of piezoelectric polymer sensors capable of measuring the movements of the fingers of the hand, and those of the hand itself.
• This device can be used inter alia as an input element to a computer for the manipulation of data in a space with several dimensions, and for the training of the robots.
• the proposed system can be extended to all or part of the movements of the human body (gear control%) Or to the detection of the movement of any mobile or articulated organ.
• Man-machine computer interfaces are today very varied: keyboards, mice, joysticks, trackballs, touch screens. These devices provide a 2-dimensional spatial location. More recently, devices have been introduced with localization in 3 dimensions (3 coordinates of 3D space), and in 6 dimensions (3 coordinates of 3D space and 3 angles).
• the hand-held transmission antenna comprises 3 solenoids with orthogonal axes excited respectively by 3 frequencies, which can be moved in a 3D space which comprises 3 antennae reception with orthogonal axes.
• Such systems are in particular very useful for the observation of 3D medical images calculated from X-ray or MRI scans.
• the twenty three pieces of information make it possible to manipulate data in a space of as many dimensions, for learning a robot hand by example.
• the invention therefore relates to a bending sensor device comprising at least one bimorph of piezoelectric polymers enclosed between two electrodes, characterized in that it comprises: a short-circuit device for weakly connecting the two electrodes one to the other. 'other; a voltage measuring device connected to the two electrodes - a control circuit for controlling the short-circuiting of the two electrodes by the short-circuit device at regular intervals.
• - measurement processing means connected to the measurement devices, receiving therefrom, measurement voltage values carried out between the different intervals where the electrodes are not short-circuited, and integrating these different voltage values to determine any bending variation of the bimorph.
• the invention also relates to a device characterized in that a main face has a common electrode and the other main face has a plurality d individual electrodes placed opposite the common electrode.
• the bimorph is generally elongated and the individual electrodes are arranged in the direction of the length of the bimorph, the voltage measuring devices being located at one end of the bimorph or offset by connections to the processor and being connected to the impedance matching circuits of the different individual electrodes.
• the invention also relates to a device characterized in that the protective envelope mainly comprises two parts each protecting a main face of the bimorph, one of the parts of the protective envelope being applied to a part of an animated body for that the device can detect any deformation of this part of the animated body.
• the invention relates to a device characterized in that the bimorph is either mono-stretched and has anisotropic piezoelectric properties, or isotropic and that it has slots perpendicular to the axis of bending to which the bimorph is subjected, in particular when 'it is isotropic.
• FIG. 8 an example of application of the sensor of the invention to the detection of movements of a finger of the hand
• Figure 9 an example of application of the sensor of the invention detecting the movements of the different fingers of one hand;
• the bending sensor proposed uses a bimortph of piezoelectric polymer as shown in FIG. 1, that is to say two films of piezoelectric polymers, bonded together, so that their polarizations are antiparonal.
• These polymers are preferably of the PVF2 type, the axis of the polymer chains being parallel to the axis Ox (mono oriented polymer).
• a description of such a bimorph is found in French patents No. 81 24564 and 81 24565.
• FIG. 2 shows a simplified diagram for carrying out such a process.
• the device of FIG. 2 comprises a bimorph 1 provided on its faces 10 and 11 with electrodes 12 and 13.
• a short-circuit device 2 represented by a contact and periodically controlled by a control circuit 4.
• a voltage measurement device 3 which measures the potential difference reflecting the charge variations on the faces 10 and 11 during a bimorph bending 1.
• the voltage measurement device 3 communicates the various measurements carried out in the intervals where the electrodes are not short-circuited, to measurement operating means 5.
• These operating means 5 continuously integrate the values supplied by the measuring device 3 and provides the position of the bimorph at all times 1 relative to a reference position, the non-flexed position for example.
• the deformation (bending) of bimorph 1 can be done as well at slow speed, at a jerky rhythm, or by bending, in one direction or another. Despite this, in all cases, the device will know the position of the bimorph.
• FIG. 3 provides an impedance matching circuit 6 making it possible to present a low output impedance to the voltage measuring device 3.
• the short-circuit device 2 and the impedance matching circuit can be produced, as this is represented in FIG. 4, in the form of a circuit having a first field effect transistor T1, therefore the source is connected to the electrode 13 of the bimorph 1, the grid is connected to the electrode 12 of the bimorph.
• a capacitor Ci connects the gate to the drain of this transistor.
• a second transistor T'1 has its source connected to a negative potential and to the source of transistor Tl by a connection conductor C'1 and its drain connected to the drain of transistor Tl by a connection conductor Cl.
• a bias resistor R connects the drains of the transistors to a positive potential.
• the output 50 of the circuit is connected to the drain of the transistor T'1.
• the gate of the transistor T'1 receives a train of pulses making it possible to turn on then alternately blocking the transistor T'1 and therefore the transistor Tl.
• the two electrodes 12 and 13 are therefore short-circuited periodically and between the short-circuit periods of the electrodes 12 and 13 a voltage measurement signal is supplied on the output SO.
• the proposed scheme represented in FIG. 2 provides a detailed embodiment of the device of the invention.
• the gain of the adaptation stage is less than 1, and the output impedance of the order of lk ⁇ , or less depending on the transistor and R.
• the sampler In its 0 most simple the sampler consists of a transistor which periodically short-circuits the output of the adaptation transistor, therefore the bimorph, via the capacitor Ci.
• FIG. 5 represents a sensor device in which the bimorph 1 has an elongated shape.
• the face 10 has several electrodes El, E2, E3 arranged in the direction of the length of the bimorph 1. At each electrode
• El, E2, E3 is associated with a field effect transistor Tl, T2,
• connection conductor (Cl, C2, C3) to the drain of a second corresponding field effect transistor (T'1, T'2, T'3).
• the transistors T'1, T'2, T'3 are arranged at the end 14 of the bimorph 1 according to the example in FIG. 5. But they can also be deported to external circuits not shown
• the sources of the transistors Tl, T2, and T3 are connected to the electrode 13. According to the example in FIG. 6, this connection is made using a connection conductor crossing in the thickness direction the bimorph 1. According to the exemplary embodiment of FIG. 7, this connection is made by providing for housing each transistor T1, T2 and T3 in a cavity formed in the thickness of the bimorph 1.
• Each pair of transistors Tl-T'l, T 2-T'2, T 3-T'3 is arranged like the circuit of FIG. 4.
• the device of FIG. 5 thus makes it possible to detect any bending in different zones (3 zones according to the example taken) of the bimorph.
• the device of the invention can be applied to the detection of movement of any animated body and in particular of any articulated body. More specifically, it can be applied to the detection of movements of the members of a human body.
• one or more sensors such as that of FIG. 5 are placed in a protective envelope and one of the faces, 11 for example, is pressed against the member whose movements are to be detected.
• the protective envelope makes it possible to apply the bimorph against the member so as to make it almost integral with the member.
• a sensor per joint will be pre-flight, that is to say 3 flexion sensors per finger.
• a bimorph then has the length between the end of the finger and the wrist, its width is about 5mm. It is sandwiched between two gloves of fabric or polymer threaded one inside the other, so as to be all along in contact with the finger considered, either on the top of the hand, or inside hand (see Figure 8).
• the internal electrode of the bimorph covers the entire surface of the bimorph; this electrode 13, common to all the sensors is for example at zero potential.
• These three electrodes preferably have identical surfaces in order to have the same piezoelectric response to the same stress. These surfaces can be different, if one wishes to weight the 3 bending signals of the three joints.
• Glued near the electrodes E .., E réelle, E clarity are the matching transistors T .., T réelle, T.,.
• the sources of these transistors are joined to the common electrode by a connection passing through a hole made in the bimorph film.
• Transistors in micro-boxes can be used for the minimum additional thickness; these transistors can themselves be housed in cavities of the polymer (see FIG. 7), if their thickness is close to that of bimorph 1. These transistors can be made transistors. in thin layers
• the outputs of the sensors are made by metal tracks deposited on the side of the electrodes E .., E Stamm, E réelle as described previously in relation to FIG. 5.
• the circuit constituted by E j , E-, E- C ⁇ j C ⁇ . C is obtained all at once by metallic evaporation through a mask, (Cr + Al), or by etching of a solid electrode.
• the previous structure can be extended to the five fingers of the hand as shown in Figure 9, we then provide 5 bands of bimorphs with a total of 14 sensors (electrodes) arranged on these bimorphs.
• 11 can be provided four abduction sensors measuring the angular differences between fingers, in a plane, or 18 sensors per hand.
• the abduction sensors are also provided.
• Sensors for detecting the movements of the different fingers of one hand will be produced by providing an inner glove GI and an outer glove GE, the sensors being housed and held in place between these two gloves
• the two gloves are polarized in
• the configuration of the sensor is the role of selecting the bending axis.
• the purpose of these slots is to remove any mechanical tension in the direction parallel to the preferred bending axis.
• a bending sensor can be produced as shown in FIG. 10 by providing in a bimorph plate 1, produced in a material of the 0 P type (VF 2 -TrFE) (see above) of the FI slots. , F2, F3.
• the faces 10 and 11 are coated with electrodes 12, 13.
• the sensor thus obtained will react to any bending having the effect of making the bimorph bend around a bending axis XX perpendicular to the slots FI, F2, F3.
• the device of the invention can of course be applied to the case of mono-stretched polymers, the slits being parallel to the direction of the chains: the discrimination of the flexions perpendicular and parallel to the chains will be increased.
• the devices described above can be extended to any joint (elbow, knee, shoulder, neck, etc.). The ultimate extension of the glove is the whole body garment.
• such a sensor provides dynamic and non-static information starting, for example, from the configuration . flat, a bending generates a certain quantity of charges, which flow in a few seconds, even a few minutes through the leakage resistance of the piezoelectric; beyond the relaxation time of the charges tr, the potential difference initially generated is canceled out, and it is therefore no longer possible to determine the static bending. Also, it is necessary to integrate the signals supplied (sampling, digitization, digital integration) to determine a static bending, from a reference state, for example, the zero bending. It is obvious that the above description has been given only by way of nonlimiting example and that other variants can be envisaged without departing from the scope of the invention. Numerical examples and material types have been given only to illustrate the description.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

Applications Claiming Priority (2)

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Cited By (1)

Citations (5)

• 1988
  • 1988-12-23 FR FR8817084A patent/FR2641077B1/fr not_active Expired
• 1989
  • 1989-12-22 WO PCT/FR1989/000671 patent/WO1990007700A2/fr unknown

Patent Citations (5)

Non-Patent Citations (2)

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