Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
  • H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
  • H02N2/02—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing linear motion, e.g. actuators; Linear positioners ; Linear motors
  • H02N2/06—Drive circuits; Control arrangements or methods
  • H02N2/062—Small signal circuits; Means for controlling position or derived quantities, e.g. for removing hysteresis
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
  • G01J3/12—Generating the spectrum; Monochromators
  • G01J3/26—Generating the spectrum; Monochromators using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filters

Definitions

• the invention lies in the field of piezoelectric actuator controls, and in particular relates to a control circuit which makes it possible to reduce the hysteresis of such actuators.
• piezoelectric actuators There are mainly two types of piezoelectric actuators: the direct actuators in which the displacement obtained in the order of one micrometer is equal to the deformation of the piezoelectric material, and the amplified actuators in which a mechanical circuit amplifies the movement. and thus increase the displacement which is of the order of a millimeter.
• an electric field is used to obtain a deformation of the piezoelectric material and to control the displacement.
• the control of an actuator may be a control voltage or load.
• U.S. Patent 4,263,527 to Comstock discloses a control device in charge of a piezoelectric actuator.
• U.S.7,015,621 B2 patent of Mizuuchi discloses a device for controlling the voltage of a piezoelectric actuator.
• the voltage control has a major disadvantage in that the displacement of the actuator, which is a function of the applied voltage, is not linear. This in particular is due to variations in the physical parameters of the piezoelectric material, creep and hysteresis.
• Creep (or "creep” in English) is a slow drift of deformation of the material as a function of time, which results in a slow elongation of the actuator under a constant tension and which leads to the position being set to a few percent per decade of time of the initial displacement instruction.
• Hysteresis (or hysteresis) is the property of a system that tends to remain in a certain state when an external cause that has produced the change of state has ceased.
• the piezoelectric actuators have a hysteresis between the applied voltage and the generated displacement. This non-linearity can vary between 10 and 20% depending on the nature of the material, and the movements of a piezoelectric actuator are not the same depending on whether it is a rising voltage or a decreasing voltage applied to it.
• the patent application FR2850219 of J. Agnus et al. discloses a combined voltage and load control device for a piezoelectric actuator that provides linear open-loop static behavior, thereby reducing hysteresis.
• the circuit requires the addition of switch and interrupt means to switch from one control mode to another.
• An object of the present invention is to provide a system that can combine two types of control of a piezoelectric actuator, a voltage control and a load control, in which the switching between the load control and the control voltage is automatically, depending on the nature of the voltage applied to the input of the assembly.
• the device of the present invention is simple to implement and inexpensive, using no other external circuit for controlling the piezoelectric actuators.
• the gain of the device is the same in low and high frequency thanks to the adaptation of the capacitive or resistive bridge.
• the gain of the amplifier is fixed by the resistances at low frequency or even continuously, while in high frequency, the gain is fixed by the capacitance of the capacitors formed by the piezoelectric actuator and the capacitor referred to as the reference capacitor C re f .
• the reference capacitor C re f the capacitance of the capacitors formed by the piezoelectric actuator and the capacitor referred to as the reference capacitor C re f .
• the hybrid amplifier can operate with any type of piezoelectric actuator for which there is no need to know the equivalent hysteresis model.
• the hybrid amplifier thus enables any open loop piezoelectric actuator to be controlled because the voltage - displacement characteristic is made substantially linear.
• the output voltage of the hybrid amplifier is taken across the piezoelectric actuator and not across the set (C pzt , R pzt , Cref, Rcref), in which case the hysteresis is not attenuated .
• the piezoelectric actuator control device of the invention comprises:
• an operational amplifier having an inverting input and a non-inverting input, and an output for delivering a voltage Release ;
• a capacitive circuit comprising a piezoelectric actuator and a capacitor in series, said capacitive circuit being connected by the free end of the piezoelectric actuator to the output of the operational amplifier and by the free end of the capacitor to a voltage terminal low;
• a resistive circuit comprising a first resistor and a second resistor in series, said resistive circuit being connected by the free end of the first resistor to the output of the operational amplifier and by the second resistor to a low voltage terminal; the device being characterized in that the inverting input of the operational amplifier is connected to the common ends of the piezoelectric actuator and the capacitor, and is connected to the common ends of the first and second resistor, the capacitive circuit and the circuit resistive forming an impedance bridge.
• the ratio of the impedances of the capacitive circuit is equal to the ratio of the impedances of the resistive circuit.
• a control signal at a given frequency applied to the non-inverting input of the operational amplifier provides control of the piezoelectric actuator.
• a continuous control signal applied to the non-inverting input of the operational amplifier makes it possible to obtain a voltage control of the piezoelectric actuator.
• the operational amplifier is powered between -60V and + 160V.
• the device of the invention comprises unidirectional transils diodes connected to the terminals of the piezoelectric actuator to limit the voltage at said terminals. The voltage across the piezoelectric actuator can be limited to + 150V and -20V, respectively.
• the device of the invention further comprises a resistor connected to the output of the operational amplifier for limiting the current delivered in the piezoelectric actuator.
• the invention also covers an interferometer controlled by a control device as described.
• the interferometer may be a Fabry-Perot interferometer.
• Piezoelectric actuators are used in various fields for various purposes such as active vibration control for assistance with the machining of industrial parts, control in microscopes of small displacements for scanning a surface to be probed, control of automobile injectors, the production of fine droplets in printers, the adjustment of the length of a laser cavity in opto-acoustics or the micro-positioning of mirrors in astronomy.
• Figure 1 illustrates a voltage control device of the prior art
• Figure 2 illustrates a control device in charge of the prior art
• FIG. 3 illustrates a hybrid control device according to one embodiment of the invention
• FIG. 4 illustrates an exemplary implementation of the device of the invention
• FIG. 5 illustrates a variant of implementation of the device of the invention
• FIG. 6 illustrates another variant of implementation of the device of the invention.
• FIG. 1 illustrates a voltage control device known from the prior art.
• the principle of the voltage control is to apply a voltage V s across a piezoelectric actuator (10) through an amplifier (12).
• the circuit comprises a piezoelectric actuator (10) connected at the output of an operational amplifier (12).
• the amplifier (12) is mounted in a non-inverting arrangement, and receives at a first input a control voltage V c .
• a first resistor Ri (14) is connected between the output of the amplifier (12) and a second input of the amplifier.
• a second resistor R 2 (16) is connected between the second input of the amplifier and a low voltage V 0 .
• the gain A v in voltage of the amplifier (12) is constant and defined by the resistors R1 and R2 (14, 1 6) according to the equation:
• This type of control has the disadvantage of a fairly high hysteresis, and is not suitable for the control of systems that require micropositionings, such as very precise displacements of mirrors in the field of optics, for example.
• FIG. 2 illustrates a load control device known from the prior art.
• the principle of load control is to apply a constant amount of charge to the electrodes of a piezoelectric actuator in order to obtain a linear behavior between the control and the displacement caused.
• the circuit of FIG. 2 comprises a piezoelectric actuator (20) connected between the output UT 'and the inverting input (-) of an operational amplifier (22), the assembly having the configuration of an assembly no inverter.
• An input voltage V c is applied to the second non-inverting input (+) of the amplifier.
• a so-called reference capacitor (24) is connected in series with the piezoelectric actuator (20) to the inverting input. It has a voltage Vc re f at its terminals.
• the capacity capacitor C ref receives a quantity of charge Q re proportional to the voltage across its terminals.
• the deformation of the piezoelectric actuator is linear as a function of the electrical load.
• the skilled person can refer to the work of J. Agnus, "Study, Realization, Characterization and Control of a Piezoelectric Micropince", University of Franche-Comté, 2003 which describes in more detail this relationship and shows that the application a constant amount of charges on the electrodes of a piezoelectric actuator makes it possible to obtain a linear behavior between the control and the displacement caused.
• the frequency of the output signal across the actuator (20) depends solely on the value of the output current and the input voltage V c of the amplifier.
• the gain of the amplifier in charge therefore depends only on the inherent capacitance value of the piezoelectric actuator and the capacitor in series with the latter.
• that of the actuator varies according to certain parameters including the voltage at its terminals.
• this type of load-controlled circuit has the disadvantage of having a creep effect and not allowing a continuous control.
• FIG. 3 illustrates a hybrid control device according to one embodiment of the invention, combining the two control modes, in load and in voltage.
• the device (300) combines a first circuit (302) for load control control with a second circuit (304) for voltage control control, the two circuits being coupled to an operational amplifier (30).
• the hybrid assembly of the invention allows switching between the two charge / voltage modes to be done automatically.
• the amplifier (30) receives an input voltage V e on a first non-inverting input (+), and outputs a output voltage V s at output OUT.
• the first circuit (302) comprises a piezoelectric actuator (32) and a capacitor (34) in series.
• the piezoelectric actuator (32) is connected to the OUT output and to the inverting input of the operational amplifier (30).
• the capacitor (34) in series is connected to the inverting input of the operational amplifier and to a low voltage V 0 .
• the first circuit is a capacitive circuit comprising a piezoelectric actuator and a capacitor in series, said capacitive circuit being connected by the free end of the piezoelectric actuator to the output of the operational amplifier and by the free end of the capacitor to a capacitor. low voltage terminal.
• the second circuit (304) comprises discrete serial components comprised of a first resistor (36) and a second resistor (38) in series.
• the first resistor (36) is connected to the output UT 'and to the inverting input of the operational amplifier (30).
• the second resistor (38) is connected to the inverting input of the operational amplifier and to a low voltage V 0 .
• the second circuit is a resistive circuit comprising a first resistor and a second resistor in series, said resistive circuit being connected by the free end of the first resistor to the output of the operational amplifier and by the second resistor to a voltage terminal low. The low voltage may preferentially be brought back to the ground.
• the inverting output (-) of the amplifier (30) corresponds to a common 'P c ' connection point between the two capacitive (302) and resistive (304) circuits.
• the connection point P c is common between the actuator (32) and the capacitor (34) for the first circuit (302), and between the first resistor (36) and the second resistor (38) for the second circuit (30). 304).
• the common connection point P c has a voltage marked 'Vcret'.
• the device is characterized in that the inverting input of the operational amplifier is on the one hand connected to the common ends of the piezoelectric actuator and the capacitor, and on the other hand connected to the common ends between the first and the second resistor, the capacitive circuit and the resistive circuit forming an impedance bridge.
• the device of the invention thus provides an impedance bridge formed by the capacitors (32, 34) of the first circuit (302) and by the first and second resistors (36, 38) of the second circuit (304).
• - Cret represents the capacity of the capacitor (34); - Rpzt and R re f respectively represent the first and second resistors of the second circuit (304).
• the values of the resistors of the resistive bridge (304) are defined to compensate for several effects:
• control signal must be of high frequency in order to allow the command in load
• Vs ⁇ p) "> * * Kc " + K >"* Ve (p) (1 1)
• equation (12) one skilled in the art finds that for a given input voltage, when 'p' tends to 0, the gain of the transfer function tends to 'R pzt / Rcref' and when 'p' goes to infinity, the gain of the transfer function tends to 'Cc re f / C pz t'.
• capacitors C pzt (32) and C ref (34) are equivalent to open circuits.
• the output current flows only through the resistors Rp Zt (36) and 'Rc re f' (38). In this mode, the device behaves like a voltage control circuit.
• the capacitors C pz t (32) and C ref (34) are equivalent to short circuits. All the output current flows through these two capacitors. In this mode, the device behaves like a load control circuit.
• the gain at low frequencies is set by the resistors (36,38) while at high frequencies it is fixed by the capacitors (32,34).
• the time constant ' ⁇ ' of the assembly is: ⁇ - Rpzt * C pz , (15)
• the piezoelectric actuator moves to a certain position with reduced hysteresis. It is the control mode in charge with the capacitive part of the first circuit (302), composed of C ref and Cp Zt which is involved.
• the actuator no longer moves, the displacement being maintained stable. There is therefore more creep unlike known load control devices.
• FIG. 4 illustrates an exemplary implementation of the device of the invention for an application to the control of mobile mirrors in Fabry-Perot interferometers.
• the hybrid control device as detailed in FIG. 3, is represented in FIG. 4 by the references (40) for the operational amplifier, (42) for the piezoelectric actuator C pz t, (44) for the capacitor of FIG. reference C ref, (46) and (48) respectively to the first and second resistors.
• capacitors may be added to enable decoupling of the supply voltages (+ V DC , -V cc ), unidirectional transils diodes (D1, D2) for limiting the voltage across the piezoelectric actuator (42).
• im can be added to limit the current delivered in the actuator and a phase compensation capacitor C cmp .
• Diodes (D3, D4) for protecting the differential input of the amplifier (40) can be added, as well as transil diodes (D5, D6) to protect the circuit against overvoltages and polarity inversions of the voltages of the amplifier. 'food.
• the amplifier may be a high voltage amplifier powered between -60V and + 160V, the voltage across the actuator limited to + 150V and -20V respectively, the current output in the actuator limited to 130mA.
• Hybrid voltage reduction amplifier control 1 19.01% 0.76% 96.00%
• FIG. 5 illustrates a variant of implementation of the device of the invention in the context of a unipolar control.
• the hybrid control device as detailed in FIG. 3, is represented in FIG. 5 by the references (50) for the operational amplifier, by (52) for the piezoelectric actuator C pzt , by (54) for the capacitor reference C ref, and by (56) and (58) respectively to the first and second resistors.
• one terminal of the actuator (52) is connected to ground, the other terminal participating in the midpoint of the impedance bridge.
• unidirectional transils diodes may be added to limit the voltage across the piezoelectric actuator (52).
• an instrumentation amplifier (510) is added, whose purpose is to equalize the reference voltage and the voltage across the assembly (R ref, C ref).
• One input of the instrumentation amplifier receives the output of the operational amplifier, the other input of the instrumentation amplifier being connected to the midpoint of the impedance bridge. The output of the instrumentation amplifier is looped back to the inverting input of the operational amplifier.
• the operation of the hybrid amplifier is the combination of the two control modes (voltage and load), it is important to identify the frequency range where each mode of operation is dominant. This frequency range is characterized by the central frequency defined by the equation:
• Such an assembly is particularly suitable for the unipolar control of piezoelectric actuators whose control does not require high voltages, of the order of 10V.
• FIG. 6 illustrates a variant of implementation of the device of the invention in the context of a unipolar control for the cases where the control voltage is high, such as the cases of large displacements.
• a non-inverting amplifier 60
• the first amplifier 60
• the gain of this amplifier is then given by the relation: 8 .
• the second part of the assembly consists of the hybrid amplifier (400) having one of the terminals of the actuator connected to ground.
• the hybrid amplifier of the invention makes it possible to significantly reduce the hysteresis amplitude of the piezoelectric actuators.
• the proposed device thus makes it possible to linearize the displacement of an actuator as a function of the voltage applied across its terminals or of the setpoint voltage.
• Another advantage of the device of the invention is that it does not require a hysteresis model (Preisach, Maxwell, ...) and can therefore operate with any piezoelectric actuator, within the limits of the electronic assembly.
• the only parameters to know for its implementation are the inherent capacity of the piezoelectric actuator at rest and its bandwidth, such data being generally available in the catalogs of manufacturers of piezoelectric actuators.
• the application areas of the hybrid amplifier of the invention may be for example nano and micropositioning, mechatronic applications or the field of virtual reality.

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• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• General Physics & Mathematics (AREA)
• General Electrical Machinery Utilizing Piezoelectricity, Electrostriction Or Magnetostriction (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2015
  • 2015-06-12 FR FR1555381A patent/FR3037454B1/fr not_active Expired - Fee Related
• 2016
  • 2016-06-10 JP JP2017564641A patent/JP2018520514A/ja active Pending
  • 2016-06-10 US US15/735,443 patent/US10389277B2/en not_active Expired - Fee Related
  • 2016-06-10 CA CA2989250A patent/CA2989250A1/en not_active Abandoned
  • 2016-06-10 CN CN201680040955.7A patent/CN107924983B/zh not_active Expired - Fee Related
  • 2016-06-10 EP EP16730318.9A patent/EP3308409A1/de not_active Withdrawn
  • 2016-06-10 KR KR1020187001063A patent/KR20180032556A/ko not_active Withdrawn
  • 2016-06-10 WO PCT/EP2016/063355 patent/WO2016198639A1/fr not_active Ceased

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