JP5284005B2 - Control method of piezoelectric actuator - Google Patents

Description

  The present invention relates to a method for controlling a piezoelectric actuator. More specifically, the voltage applied to the piezoelectric actuator and the induced charge are input, and the displacement and / or load of the piezoelectric actuator is estimated, and the piezoelectric actuator is determined based on the estimated displacement and / or load. The present invention relates to a method for controlling a piezoelectric actuator that sets a voltage to be applied.

  Conventionally, a piezoelectric actuator is known as an actuator used for a minute positioning mechanism, a minute drive mechanism, and the like. This piezoelectric actuator utilizes the extension of the crystal constituting the element by applying a voltage, whereby the positioning object or the driving object can be displaced with high accuracy.

  By the way, this piezoelectric actuator has a hysteresis between the applied voltage and the generated displacement or load, and cannot be handled by a monovalent function. For this reason, when controlling the piezoelectric actuator with high accuracy, it is necessary to control the displacement and / or load information of the piezoelectric actuator by feeding it back to the applied voltage. However, in order to perform such feedback control, it is necessary to provide a sensor for detecting a mechanical amount such as displacement and / or load on the piezoelectric element.

  Therefore, in Non-Patent Document 1, an electrical quantity, for example, a voltage and a charge quantity is detected without detecting a mechanical quantity such as an actual displacement or a load of the piezoelectric actuator, and the detected voltage and charge are detected. A piezoelectric actuator control method for estimating displacement and load of the piezoelectric actuator based on the quantity has been proposed.

  By the way, as a control method shown in Non-Patent Document 1, various methods have been proposed as a method for estimating the displacement and the load based on the voltage and charge of the piezoelectric actuator. The first is a method based on a so-called piezoelectric equation, and the second is a method based on an electromechanical model that reproduces the behavior of a piezoelectric actuator (see Non-Patent Document 2).

ここで、Ｙは素子のヤング率であり、ε_３３は誘電率であり、ｄ_３３は圧電定数である。 First, the first method will be described with reference to FIGS. 16 and 17.
FIG. 16 is a schematic diagram showing one piezoelectric element. As shown in FIG. 16, when a predetermined voltage is applied from the upper and lower ends of the substantially cubic piezoelectric element, an electric field having an electric flux density D ₃ and an electric field strength E ₃ is generated in the piezoelectric element along the vertical direction. At the same time, due to the longitudinal piezoelectric effect, the T ₃ stress and the S ₃ distortion are generated in the vertical direction in the piezoelectric element. Here, from the piezoelectric equation, the following relational expression is derived with respect to the electric flux density D ₃ , the electric field strength E ₃ , the stress T ₃ , and the strain S ₃ .

Here, Y is the Young's modulus of the element, ε ₃₃ is the dielectric constant, and d ₃₃ is the piezoelectric constant.

  FIG. 17 is a schematic diagram showing the configuration of a stacked piezoelectric actuator, and shows a piezoelectric actuator configured by stacking n piezoelectric elements shown in FIG. Here, assuming that the thickness of one piezoelectric element along the vertical direction is d and the cross-sectional area is A, the following equation is derived from the piezoelectric equation for one piezoelectric element described above.

Here, q is the amount of charge induced in each electrode, and is represented by q = D ₃ A ² . K is the rigidity of the piezoelectric element, and is represented by K = YA / nd. C is a capacitance and is represented by C = ε ₃₃ nA / d. V is a voltage and is indicated by V = E ₃ d. x is the displacement and is indicated by x = ndS ₃ . F is a load and is indicated by T ₃ A. Further, α = Knd ₃₃ and C ′ = C− (nd ₃₃ ) ² K were set.

  According to the simultaneous equations of Formula 2 derived based on the piezoelectric equation as described above, the displacement x and the load F can be calculated by detecting the voltage V and the charge amount q of the piezoelectric actuator. . However, the equation (2) does not consider the nonlinearity of the piezoelectric actuator such as hysteresis.

  Next, the 2nd method described in the nonpatent literature 2 is demonstrated, referring FIGS. 18-21. The second method reproduces the behavior of the piezoelectric actuator based on an electromechanical model configured by combining an electric element and a mechanical element. In addition to the first method described above, the second method is a nonlinear method of the piezoelectric actuator. Sex is considered.

  FIG. 18 is a circuit diagram illustrating a configuration of an electromechanical model of the piezoelectric actuator disclosed in Non-Patent Document 2. As shown in FIG. 18, the electromechanical model includes a capacitor C ′, a converter T that converts electrical energy into mechanical energy, a mechanical element 91 coupled to the converter T, a capacitor and a resistor. And an MRC (Maxwell Resistive Capacitance) element 92 configured by combining the elements.

Mechanical element 91 is constituted by connecting the object of mass 0 at the spring of spring constant K _E. Transducer T, the output is connected so as to act on the object machine element 91 as an external force F _P. Here, in the circuit of FIG. 18, the following equation is derived considering only the elements surrounded by the broken line 99, that is, the elements composed of the capacitor C ′, the converter T, and the mechanical element 91.

  That is, the element surrounded by the broken line 99 is a model equivalent to the above-described formula 2. The electromechanical model shown in Non-Patent Document 2 includes an MRC element 92 as an element that reproduces the hysteresis of the piezoelectric actuator in addition to the element surrounded by a broken line 99 that describes the linear behavior of the piezoelectric actuator. Including.

FIG. 19 is a schematic diagram showing a configuration of a mechanical model (Maxwell Slip Model) equivalent to the MRC element 92. This machine model is formed by connecting n machine elements connected in parallel with an object having a mass of 0 by a spring having a spring constant K _i . The object of each element is under the action of a normal drag, whereby a static friction force f _i acts. Here, when x and F are the displacement and acting force of the entire element, and x _bi and F _i are the displacement and acting force of each object, the following equations are derived.

FIG. 20 is a diagram showing the relationship between the displacement x of the machine model and the force F when n = 1, and FIG. 21 shows the relationship between the displacement x and the force F of the machine model in which a plurality of machine elements are arranged in parallel. FIG. As shown in FIGS. 20 and 21, hysteresis occurs between the displacement x and the force F. 20 and 21 are compared, in the example shown in FIG. 20, since n = 1, that is, the number of machine elements is one, this hysteresis is a combination of straight lines. On the other hand, in the model in which a plurality of machine elements are arranged in parallel, different constants k _i and f _i are input to each machine element, and the plurality of machine elements are arranged in parallel, so that as shown in FIG. The linear behavior of elements can be approximated by a smooth curve.

  Returning to FIG. 18, when the relational expression is derived for the force F acting on the object, the charge q, and the potential difference V for the electromechanical model including the MRC element 92 equivalent to the above mechanical model, the following expression is obtained. become.

Here, the potential difference V _h between the MRC elements 92 is described by the following equation with ν _i and C _i as constants by analogy with the above-described machine model.

According to the electromechanical model shown in Non-Patent Document 2, the behavior of the piezoelectric actuator taking nonlinearity into consideration can be reproduced by combining the above equations 5 and 6. In particular, the hysteresis of the piezoelectric actuator can be reproduced by including the potential difference V _h between the MRC elements 92 shown in Equation 6. Further, according to this electromechanical model, a hysteresis curve having a plurality of inflection points can be reproduced depending on the values of the parameters ν _i and C _i .
C. Raupach, J. Melbert, “Advanced Injection System by Means of Sensor Actuator Function,” SAE, no. 2005-01-0908, April 2005 M. Goldfarb, N. Celanovic, “Modeling piezoelectric stack actuators for control of micromanipulation,” IEEE Control Systems Magazine, vol. 17, no. 3, pp. 66 -79, June 1997

However, in the electromechanical model shown in Non-Patent Document 2 described above, it is necessary to input two parameters ν _i and C _i for each machine element as shown in Equation 6. As described above, in order to reproduce the hysteresis curve with a smoother curve, it is necessary to provide a large number of elements, and thus it is necessary to input a larger number of parameters ν _i and C _i . For this reason, there is a possibility that an arithmetic unit capable of high-speed calculation is required.

  As shown in FIGS. 20 and 21, in the hysteresis according to the above-described model, the path when the displacement increases and the path when the displacement decreases become, for example, symmetrical paths around the origin. However, the hysteresis generated in the piezoelectric actuator generally does not have such symmetry. Therefore, the electromechanical model shown in Non-Patent Document 2 is not a model that reproduces the behavior of an actual piezoelectric actuator.

  Further, when residual displacement occurs after the first voltage application after the power is turned on, there is no model that takes into account that the first and second displacement loci are different.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for controlling a piezoelectric actuator capable of high-speed computation while taking into account the nonlinearity and displacement trajectory of the piezoelectric actuator. To do.

ただし、ｑ，Ｖｈは変数とし、α，ａ，Ｖｈｍａｘは定数とする。 (1) The voltage applied to the piezoelectric actuator and the induced charge are input, the displacement and / or load of the piezoelectric actuator is estimated, and the voltage applied to the piezoelectric actuator based on the estimated displacement and / or load. Alternatively, a method for controlling a piezoelectric actuator that sets an amount of charge, wherein a displacement and / or based on a hysteresis function configured based on at least the following function from a voltage applied to the piezoelectric actuator and an induced charge: A method for controlling a piezoelectric actuator, characterized by estimating a load.

However, q and Vh are variables, and α, a, and Vhmax are constants.

  According to the invention described in (1), the voltage applied to the piezoelectric actuator is determined based on the estimated displacement and / or load of the piezoelectric actuator. Here, when the displacement and / or load is estimated, the displacement and / or load is estimated based on a hysteresis function configured based on Equation 7. Thereby, the piezoelectric actuator can be controlled in consideration of its hysteresis.

Here, the above formula 7 is compared with the formula 6 based on the electromechanical model of Non-Patent Document 2. As described above, according to the electromechanical model of Non-Patent Document 2, in order to reproduce hysteresis with a smoother curve, it is necessary to provide more elements as necessary. On the other hand, the number of parameters that need to be input in _Equation 7 is three (α, a, V _hmax ). Therefore, in comparison with the electromechanical model based on the Maxwell Slip Model shown in Non-Patent Document 2, the nonlinearity of the piezoelectric actuator can be reproduced with a smaller number of parameters, so that an arithmetic unit capable of high-speed calculation is not provided. The piezoelectric actuator can be driven stably.

  Further, residual displacement may occur after the first voltage application after the power is turned on, and the second and subsequent voltage application can be accurately expressed by taking into account the characteristics due to the effect of the residual displacement using the hysteresis function of Equation 7. Therefore, it is possible to improve the estimation accuracy of displacement and / or load by modeling a more realistic piezoelectric actuator.

(2) A method for controlling a piezoelectric actuator, wherein constants α, a, and V _hmax are set in accordance with the sign of q change amount (dq / dt).

  According to the invention described in (2), depending on whether the amount of change in q (dq / dt) is positive or negative, for example, by switching the constant between dq / dt ≧ 0 and dq / dt <0. Since the hysteresis loop can be expressed as asymmetric, a more realistic piezoelectric actuator can be modeled, and the displacement and / or load estimation accuracy can be improved.

  (3) The voltage applied to the piezoelectric actuator and the induced charge are input, the displacement and / or load of the piezoelectric actuator is estimated, and the voltage applied to the piezoelectric actuator based on the estimated displacement and / or load. Alternatively, a method for controlling a piezoelectric actuator that sets a charge amount, wherein a displacement and / or a load is estimated from at least one hysteresis function from a voltage applied to the piezoelectric actuator and an induced charge, and the hysteresis The function is a method of controlling a piezoelectric actuator, wherein a trajectory due to the first voltage application after power-on is different from a trajectory due to the second voltage application.

  According to the invention described in (3), similarly to the above (1), the piezoelectric actuator can be controlled in consideration of its hysteresis, and an electric machine based on the Maxwell Slip Model shown in Non-Patent Document 2 Compared with the model, the nonlinearity of the piezoelectric actuator can be reproduced with a smaller number of parameters, so that the piezoelectric actuator can be driven stably without providing a calculator capable of high-speed calculation. Moreover, since the voltage application after the second time can be accurately expressed by considering the characteristics due to the influence of the residual displacement, the displacement and / or the load can be reduced by modeling a more realistic piezoelectric actuator. The estimation accuracy can be improved.

  According to the present invention, the piezoelectric actuator can be controlled in consideration of its hysteresis. Compared with the electromechanical model based on Maxwell Slip Model, the nonlinearity of the piezoelectric actuator can be reproduced with a smaller number of parameters, so the piezoelectric actuator can be driven stably without providing an arithmetic unit capable of high-speed calculation. . In addition, by modeling a more realistic piezoelectric actuator considering asymmetry, it is possible to improve the estimation accuracy of displacement and / or load.

  Furthermore, since the voltage application after the second time can be accurately expressed by considering the characteristics due to the effect of the residual displacement, the displacement and / or load can be reduced by modeling a more realistic piezoelectric actuator. The estimation accuracy can be improved.

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

  FIG. 1 is a block diagram showing a configuration of a piezoelectric actuator control apparatus 1 as an embodiment according to a method for controlling a piezoelectric actuator of the present invention. The piezoelectric actuator control device 1 includes an F / B control unit 20 that sets a target voltage to be applied to the piezoelectric actuator 10, an actuator driving unit 30 that drives the piezoelectric actuator 10 with the set target voltage, and a voltage of the piezoelectric actuator 10. And a detection unit 50 that detects electric charge, and a displacement load estimation unit 50 that estimates displacement and / or load of the piezoelectric actuator 10 based on the detected voltage and electric charge.

  The F / B control unit 20 calculates the difference between the input target displacement and / or target load and the estimated displacement and / or estimated load estimated by the displacement load estimation unit 60, and the displacement of the piezoelectric actuator 10 And / or the target voltage or target charge amount applied to the piezoelectric actuator 10 is set so that the load quickly converges to the target value. Hereinafter, the F / B control unit 10 sets a target voltage to be applied to the piezoelectric actuator 10, but is not limited thereto. The actuator driving unit 30 drives the piezoelectric actuator 10 by outputting a driving signal corresponding to the target voltage set by the F / B control unit 20.

  FIG. 2 is a block diagram illustrating a configuration of the displacement load estimation unit 60. The displacement load estimation unit 60 is a circuit that estimates the displacement x and the load F according to the input charge q and voltage V based on the simultaneous equations shown in Equation 7 above. More specifically, the displacement load estimation unit 60 estimates the displacement x and the load F based on the following equation.

Here, the above equation 8 is a hysteresis function. More specifically, the displacement load estimation unit 60 includes a hysteresis calculating portion 61 for calculating the voltage V _h based on the differential equations discussed above, the displacement calculating unit 62 which calculates the amount of displacement x, the. In addition, the displacement load estimation unit 60 includes a first amplifier 63, a second amplifier 65, a first subtractor 66, and a second subtractor 67.

The hysteresis calculating unit 61 receives the charge q and calculates the voltage V _{h according} to a procedure described in detail later with reference to FIG. First subtractor 66, a voltage V that is input, the voltage V _h calculated by the hysteresis calculating portion 61 subtracts outputs a V _C. Displacement calculating unit 62, based on _{V C} and q inputted, calculates the _{(q-C'V C) / K} E, and outputs it as a displacement x. The first amplifier 63 and the second amplifier 65 respectively multiply the input by α times and K _E and output. The second subtractor 67 calculates the input K _E x-αV _C and outputs it as a load F. With the configuration as described above, the displacement load estimation unit 60 estimates the displacement x and the load F. Note that the displacement load estimation unit 60 can also estimate only one of the displacement x and the load F.

Next, the configuration of the hysteresis calculation unit 61 will be described with reference to FIGS. The hysteresis calculating portion 61 inputs the charge q, and outputs the V _h based on differential equations considering hysteresis. Here, the function dq / dt calculates V _h by a hysteresis function described based on the following function.

ただし、ｑ，Ｖｈは変数とし、α，ａ，Ｖｈｍａｘは定数とする。

However, q and Vh are variables, and α, a, and Vhmax are constants.

FIG. 3 is a diagram illustrating a hysteresis function configured based on the function of Equation 9. Specifically, the first voltage application after power-on loops from P ₀ (q ₀ = 0, V _h = 0) to P _max (q _max , V _hmax ), and the first return remains. Due to the influence of the displacement, it loops to P _min (q _min , V _hmin ) instead of P ₀ . After the second time, a loop from P _min to P _{max and} a loop from P _max to P _min are alternately repeated.

The hysteresis calculation unit 61 calculates V _h for the input q using a hysteresis function. Here, when the amount of change in q becomes large, that is, when dq / dt ≧ 0, the hysteresis function sets V _h based on constants α = α ₁ , a = a ₁ , V _hmax = V _hmax1. When q is changed and dq / dt <0, V _h is determined based on constants α = α ₂ , a = a ₂ , and V _hmax = V _{hmax 2} . That is, an asymmetric hysteresis loop can be expressed by setting each constant according to the increase or decrease in the amount of change in q. The intersection points P _min and P _max are turning points with the minimum value q _min and the maximum value q _max of q in the hysteresis function as input values, respectively.

Next, a procedure for calculating V _h for the input q based on the hysteresis function as described above will be described. FIG. 4 is a flowchart showing a procedure of hysteresis calculation processing in the hysteresis calculation unit 61.

First, the hysteresis calculation unit 61 acquires the input q and the rate of change dq / dt (step S1), and proceeds to step S2. In step S2, it is determined whether or not dq / dt ≧ 0. If this determination is YES, the process proceeds to step S3, and if NO, the process proceeds to step S4. In step S3, the outputs _{V h} based on the constant _{α = α 1, a = a} 1, V hmax = V hmax1, ends the hysteresis processing. In step S4, the outputs _{V h} based on the constant _{α = α 2, a = a} 2, V hmax = V hmax2, ends the hysteresis processing.

  FIG. 5A is a diagram showing the time change of the input voltage, and FIG. 5B is a diagram showing the time change of the displacement. Although the time change of the input voltage is constant, the displacement does not return to 0, which indicates that a residual displacement has occurred after the first voltage application.

<Comparative example>
Next, the displacement and load of the piezoelectric actuator 10 estimated by the piezoelectric actuator control device 1 configured as described above are compared with the measured displacement and load with reference to FIGS.

  FIG. 6 is a schematic diagram showing the configuration of a test apparatus 80 that measures the displacement and load of the piezoelectric actuator 10.

  The test apparatus 80 includes a target member 81 as a driving object to be displaced by driving the piezoelectric actuator 10 with the piezoelectric actuator control apparatus 10 described above, a displacement sensor 82 for measuring the displacement [m] of the target member 81, A load sensor 83 that measures a load [N] generated in the piezoelectric actuator 10, and a housing member 84 that houses the piezoelectric actuator 10, a target member 81, a displacement sensor 82, and the load sensor 83 are provided.

  The accommodating member 84 is substantially cylindrical, and the load sensor 83, the piezoelectric actuator 10, and the target member 81 are accommodated in order from the lower end to the upper end. The target member 81 is slidable according to the expansion and contraction of the piezoelectric actuator 10. A spring 85 that constantly presses the target member 81 toward the upper end side of the piezoelectric actuator 10 is interposed between the upper end portion of the housing member 84 and the upper end portion of the target member 81. The target member 81 and the load sensor 83 are sandwiched.

  The displacement sensor 82 measures the displacement of the target member 81 assuming that the position of the target member 81 in a state where no voltage is applied to the piezoelectric actuator 10 is 0, and is positive in the direction in which the piezoelectric actuator 10 extends. The load sensor 83 measures a load acting along the direction in which the piezoelectric actuator 10 extends.

  In addition to the spring 85 described above, a compressed sample 86 that is compressed by the target member 81 when the piezoelectric actuator 10 is driven is provided between the upper end portion of the housing member 84 and the upper end portion of the target member 81. Yes. The compressed sample 86 simulates a resistance force acting on the target member 81 when the target member 82 is displaced, and can be exchanged for a sample formed of a different material. That is, the resistance force acting on the target member 81 can be changed by changing the material of the compressed sample 86.

FIG. 7 is a diagram showing changes in displacement and load measured when different voltages are applied to the piezoelectric actuator 10. In the case where the samples 1 to 3 are used as the compression sample 86 and the case where no sample is provided. It is a figure which shows the change of a displacement and a load. Here, the horizontal axis is displacement [m ⁻⁶ ], and the vertical axis is load [N]. Samples 1 to 3 are made of materials whose rigidity decreases in the order of samples 1, 2, and 3, respectively.

  A voltage for driving the piezoelectric actuator 10 is applied to the piezoelectric actuator 10 in a pulse shape over a predetermined time so that the peak value becomes a predetermined maximum value. Here, FIG. 7 shows changes in displacement and load when the maximum value of the applied voltage is 20, 40, 60, 80, 100, 120, 140 [V].

  As shown in FIG. 7, when the voltage applied to the piezoelectric actuator 10 is changed over a predetermined time, the displacement and the load measured by the displacement sensor 82 and the load sensor 83 draw a hysteresis. Further, as the maximum value of the voltage applied to the piezoelectric actuator 10 is increased, the maximum values of displacement and load measured by the displacement sensor 82 and the load sensor 83 are also increased. Further, as the rigidity of the compressed sample 86 becomes smaller, the maximum load value measured by the load sensor 82 becomes smaller and the displacement measured by the displacement sensor 82 becomes larger.

  Further, when no sample is provided as the compressed sample 86, the only member that presses the piezoelectric actuator 10 against the load sensor 83 against the expansion of the piezoelectric actuator 10 is the spring 85, so that the maximum displacement is applied. It is substantially 0 regardless of the magnitude of the voltage.

  Next, referring to FIGS. 8 to 15, the displacement and load measured by the displacement sensor 82 and the load sensor 83 and the piezoelectric actuator control device 1 when the maximum value of the applied voltage is changed as described above. Compare the estimated displacement and load.

  Here, in each of FIGS. 8 to 15, the upper graph in the figure shows a comparative example of the displacement or load estimated by the conventional piezoelectric actuator control device and the measured displacement or load. The lower graph shows a comparative example of the displacement or load estimated by the piezoelectric actuator control device 1 and the measured displacement or load.

  Here, the conventional piezoelectric actuator control device refers to a piezoelectric actuator control device that estimates displacement and load based on the above formulas 5 and 6 in which asymmetry of the hysteresis function is not considered.

  FIGS. 8 and 9 are diagrams showing temporal changes in displacement and load when the sample 1 having the highest rigidity is used as the compressed sample 86 of the test apparatus 80, respectively. FIGS. 10 and 11 are diagrams showing temporal changes in displacement and load when the sample 2 having the second highest rigidity is used as the compressed sample 86 of the test apparatus 80, respectively. FIGS. 12 and 13 are diagrams showing temporal changes in displacement and load when the sample 3 having the lowest rigidity is used as the compressed sample 86 of the test apparatus 80, respectively. FIG. 14 and FIG. 15 are diagrams showing temporal changes in displacement and load when the test apparatus 80 is not provided with the compressed sample 86, respectively.

  In FIGS. 8 to 15, the solid line indicates the time variation of the displacement or load measured by the displacement sensor 82 or the load sensor 83 with respect to each maximum voltage, and the broken line composed of a plurality of dots indicates each maximum voltage. It shows the time variation of displacement or load estimated with respect to voltage.

  As shown in FIGS. 8, 10, 12, and 14, the time variation of the displacement estimated by the piezoelectric actuator control device 1 (see the lower graph in the figure) is the displacement time estimated by the conventional piezoelectric actuator control device. Compared to the change (refer to the upper graph in the figure), it is closer to the time change of the measured displacement indicated by the solid line. That is, the displacement estimation performance by the piezoelectric actuator control device 1 is improved as compared with the conventional piezoelectric actuator control device. As shown in FIGS. 8, 10, 12, and 14, the estimated performance is improved regardless of the material of the compressed sample 86, that is, the magnitude of the resistance acting on the target member 81. Further, this estimated performance is improved regardless of the maximum value of the voltage applied to the piezoelectric actuator 10.

  In these FIGS. 8, 10, 12, and 14, the displacements are estimated in the regions 70, 72, 74, and 76 surrounded by the broken lines, that is, in the regions where the displacement converges toward 0 after reaching the maximum value. The performance is particularly improved. This is because the piezoelectric actuator control device 1 considers the hysteresis asymmetry of the piezoelectric actuator 10.

  As shown in FIGS. 9, 11, 13, and 15, the time change of the load estimated by the piezoelectric actuator control device 1 (see the lower graph in the figure) is the load time estimated by the conventional piezoelectric actuator control device. Compared to the change (see the upper graph in the figure), it is closer to the time change of the measured load indicated by the solid line. That is, the load estimation performance by the piezoelectric actuator control device 1 is improved as compared with the conventional piezoelectric actuator control device. As shown in FIGS. 9, 11, 13, and 15, the estimated performance is improved regardless of the material of the compressed sample 86, that is, the magnitude of the resistance acting on the target member 81. Further, this estimated performance is improved regardless of the maximum value of the voltage applied to the piezoelectric actuator 10.

  9, 11, 13, and 15, the load estimation performance is particularly improved in the broken lines 71, 73, 75, and 77, that is, in the region where the load converges toward 0 after reaching the maximum value. This is because the piezoelectric actuator control device 1 considers the hysteresis asymmetry of the piezoelectric actuator 10.

  The embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments, and includes designs and the like that do not depart from the gist of the present invention.

It is a block diagram which shows the structure of the piezoelectric actuator control apparatus as one Embodiment which concerns on the control method of the piezoelectric actuator of this invention. It is a block diagram which shows the structure of the displacement load estimation part of the said piezoelectric actuator control apparatus. It is a figure which shows the hysteresis function comprised based on the function dq / dt. It is a flowchart which shows the procedure of the hysteresis calculation process of the piezoelectric actuator control apparatus which concerns on the said embodiment. It is a figure for demonstrating that the residual displacement has arisen after the voltage application of the 1st time. It is a schematic diagram which shows the structure of the test apparatus which measures the displacement and load of a piezoelectric actuator. It is a figure which shows the displacement and load change which were measured when a different voltage was applied to a piezoelectric actuator. It is a figure which shows the time change of the displacement at the time of using the sample with the highest rigidity as a compression sample. It is a figure which shows the time change of the load at the time of using the sample with the highest rigidity as a compression sample. It is a figure which shows the time change of the displacement at the time of using the sample with the 2nd highest rigidity as a compression sample. It is a figure which shows the time change of the load in the case of using the sample with the 2nd highest rigidity as a compression sample. It is a figure which shows the time change of the displacement at the time of using the sample with the lowest rigidity as a compression sample. It is a figure which shows the time change of a load in case the sample with the lowest rigidity is used as a compression sample. It is a figure which shows the time change of the displacement in the case where the compression sample is not provided. It is a figure which shows the time change of the load in the case where the compression sample is not provided. It is a schematic diagram which shows the structure of a piezoelectric element. It is a schematic diagram which shows the structure of a laminated type piezoelectric actuator. It is a circuit diagram which shows the structure of an electromechanical model. It is a schematic diagram which shows the structure of a machine model. It is a figure which shows the relationship between the displacement x and force F of a machine model in the case of n = 1. It is a figure which shows the relationship between the displacement x of the mechanical model which arranged the some element in parallel, and force F.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Piezoelectric actuator control apparatus, 10 ... Piezoelectric actuator, 20 ... F / B control part, 30 ... Actuator drive part, 50 ... Detection part, 60 ... Displacement load estimation part, 61 ... Hysteresis calculation part, 62 ... Displacement amount calculation part 63... First amplifier 65. Second amplifier 66. First subtractor 67.

Claims (2)

As the input voltage V and the induced charges q that is applied to the piezoelectric actuator, and estimates the displacement x and the load F of the piezoelectric actuators, the voltage applied to the piezoelectric actuator based on the displacement x and the load F is the estimated or A method for controlling a piezoelectric actuator for setting a charge amount,
From the voltage V applied to the piezoelectric actuator and the induced charge q, the voltage Vh is calculated based on a hysteresis function configured based on at least the function expressed by the following [Equation 1], and at least A method for controlling a piezoelectric actuator, wherein the displacement x and the load F are estimated based on a relational expression expressed by [Equation 2] .

In the formula, q is an induced charge , Vh is a voltage calculated from a hysteresis function , q and Vh are variables, and α, a, and Vhmax are constants .

In the formula, x is displacement, F is a load, V is an applied voltage, q is an induced charge, and K _E , α, and C ′ represent constants. With respect to the constants α, a, and Vhmax in the function expressed by [Equation 1], when the amount of change in q (dq / dt) is zero or more, the constants α, a, and Vhmax are predetermined values α1, When a1 and Vhmax1 are set and a change amount (dq / dt) of q is negative, different values α2, a2, and Vhmax2 are set as constants α, a, and Vhmax, respectively. Item 2. A method for controlling a piezoelectric actuator according to Item 1.

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