JP2008245339A - Control method of piezoelectric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method that can achieve high-speed operation while taking the non-linearity of a piezoelectric actuator into consideration. <P>SOLUTION: Using a voltage V supplied to the piezoelectric actuator and induced electric charge "q" as inputs, displacement x and load F of the piezoelectric actuator are estimated and a voltage to be supplied is set up based on the displacement x and the load F. Under the assist by an actuator model in consideration of the non-linearity, the displacement x and the load F are estimated based on a hysteresis function structured from a plurality of functions including two functions f<SB>1</SB>(q) and f<SB>2</SB>(q) of at least equation 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

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, the displacement and load of the piezoelectric actuator are estimated, and the voltage to be applied to the piezoelectric actuator based on the estimated displacement and load is calculated. The present invention relates to a method for controlling a piezoelectric actuator to be set.

  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 feed back the displacement and load information of the piezoelectric actuator to the applied voltage. However, in order to perform such feedback control, it is necessary to provide a sensor for detecting mechanical quantities such as displacement and 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).

First, the first method will be described with reference to FIGS.
FIG. 18 is a schematic diagram showing one piezoelectric element. As shown in FIG. 18, when a predetermined voltage is applied from the upper and lower ends of a 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. 19 is a schematic diagram showing a 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. 20-23. 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. 20 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. 20, the electromechanical model includes a capacitor C ′, a converter T that converts electrical energy into mechanical energy, a mechanical element 91 connected 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. 20, only the elements surrounded by the broken line 99, that is, the elements constituted by the capacitor C ′, the converter T, and the machine element 91 are considered, and the following expression is derived.

  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 the broken line 99 that describes the linear behavior of the piezoelectric actuator. Including.

FIG. 21 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. 22 is a diagram showing the relationship between the displacement x of the machine model and the force F when n = 1, and FIG. 23 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. 22 and 23, hysteresis occurs between the displacement x and the force F. 22 and FIG. 23 are compared, in the example shown in FIG. 22, 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 a 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.

  Referring back to FIG. 20, 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 mechanical model as described above, 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.

  Further, as shown in FIGS. 22 and 23, 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.

  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 nonlinearity into consideration.

ただし、ｑは変数とし、ａ_１，ｂ_１，ｃ_１，ａ_２，ｂ_２，ｃ_２は定数とする。 (1) Using the voltage and induced charge applied to the piezoelectric actuator as inputs, the displacement and load of the piezoelectric actuator are estimated, and the voltage or charge applied to the piezoelectric actuator is calculated based on the estimated displacement and load. A method for controlling a piezoelectric actuator to be set, which is based on a plurality of functions including at least the following two functions f ₁ (q) and f ₂ (q) with the assistance of an actuator model in consideration of the nonlinearity of the piezoelectric actuator. A method for controlling a piezoelectric actuator, wherein displacement and load are estimated based on a hysteresis function configured as described above.

However, q is a variable, and a ₁ , b ₁ , c ₁ , a ₂ , b ₂ , and c ₂ are constants.

According to the invention described in (1), the voltage applied to the piezoelectric actuator is determined based on the estimated displacement and load of the piezoelectric actuator. Further, here, when estimating the displacement and the load, it is based on a plurality of functions including _two functions f ₁ (q) and f ₂ (q) with the assistance of the actuator model in consideration of the nonlinearity of the piezoelectric actuator. Is estimated based on a hysteresis function constituted by 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, in Equation 7, the number of parameters that need to be input is at most six. 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.

In addition, according to the invention described in (1), hysteresis asymmetry can be easily taken into account by inputting different parameters as the functions f ₁ (q) and f ₂ (q). That is, by modeling a more realistic piezoelectric actuator considering asymmetry, it is possible to improve the estimation accuracy of displacement and load.

  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 load.

  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 the displacement and 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 target load and the estimated displacement and estimated load estimated by the displacement load estimation unit 60, and the displacement and load of the piezoelectric actuator 10 are quickly increased. The target voltage or target charge amount applied to the piezoelectric actuator 10 is set so as to converge 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 6 above. More specifically, the displacement load estimation unit 60 estimates the displacement x and the load F based on the following equation.

  Here, the function f (q) is a hysteresis function, and is a multivalent function configured by combining a plurality of functions, as will be described in detail later.

More specifically, the displacement load estimation unit 60 includes a hysteresis calculation unit 61 that calculates the voltage V _h based on the above-described multivalent function, and a displacement amount calculation unit 62 that calculates the displacement amount x. 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 calculation unit 61 receives the charge q and calculates the voltage V _{h according} to a procedure that will be described in detail later with reference to FIGS. 4 and 5. 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.

Next, the configuration of the hysteresis calculating 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 polyvalent function considering hysteresis. Here, as the multivalent function f (q), a function constituted by combining a plurality of functions satisfying the following two conditional expressions is used.

More specifically, the hysteresis calculation unit 61 translates and symmetrically moves the following two functions f ₁ (q) and f ₂ (q) and these functions f ₁ (q) and f ₂ (q). calculating a V _h hysteresis function described based on a function.

ただし、ｑは変数とし、ａ_１，ｂ_１，ｃ_１，ａ_２，ｂ_２，ｃ_２は定数とする。

However, q is a variable, and a ₁ , b ₁ , c ₁ , a ₂ , b ₂ , and c ₂ are constants.

FIG. 3 is configured based on the functions f ₁ (q) and f ₂ (q) of Formula 10 and the function g ₂ (q) obtained by translating and symmetrically moving f ₂ (q) among these functions. It is a figure which shows the hysteresis function to be performed. Specifically, the intersection of f ₁ (q) and f ₂ (q) is P _min and P _max, and the midpoint of a straight line connecting these intersections P _min and P _max is I, and the function g ₂ (q) Is constructed by moving the function f ₂ (q) symmetrically with respect to the midpoint I.

Of these functions, the hysteresis calculation unit 61 calculates V _h for the input q by a hysteresis function constituted by a closed curve formed by f ₁ (q) and g ₂ (q). Here, the hysteresis function determines V _h based on the function f ₁ (q) when q increases, that is, when dq / dt ≧ 0, and when q decreases, that is, dq / dt. If <0, V _h is determined based on the function g ₂ (q). That is, the intersection points P _min and P _max described above 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 q is a maximum value or a minimum value based on the rate of change dq / dt. If this determination is YES, the process proceeds to step S3, and if NO, Move on to S4. Specifically, in this step S2, based on the rate of change dq / dt, it is determined whether the input q is an input corresponding to one of the turning points P _min and P _max shown in FIG. To do.

  In step S3, a hysteresis function update process, which will be described in detail later with reference to FIG. 5, is performed, and the process proceeds to step S4. This hysteresis function update process S3 is a process for updating the turning point of the hysteresis function in response to the input q being a maximum value or a minimum value.

In step S4, it is determined whether dq / dt ≧ 0. If this determination is YES, the process proceeds to step S5, and if NO, the process proceeds to step S6. In step S5, and outputs a _{V h} based on a function _f 1 (q), and ends the hysteresis processing. In step S6, the output _{V h} based on a function _g 2 (q), and ends the hysteresis processing.

  Next, a procedure for updating the hysteresis function will be described. FIG. 5 is a flowchart showing a procedure of hysteresis function update processing in the hysteresis calculation unit 61.

First, the hysteresis calculation unit 61 determines whether or not q> q _max . If this determination is YES, the process proceeds to step S15. If NO, the process proceeds to step S12. More specifically, based on the history of the input q stored in a predetermined storage area, it is determined whether or not the input value is greater than the input value q _max corresponding to the turning point P _max of the hysteresis function.

In step S12, q _min and V _{h_min} are updated, and the process _proceeds to step S13. Specifically, the input q updates the _{q min} as the minimum value, it calculates a _f 1 _{(q min)} for the _{q min} and _{V H_min,} updates the turning point _{P min.}

In step S13, the function f ₁ (q) is translated, a function f ₁ ′ (q) is calculated, and the process proceeds to step S14. Specifically, as shown in FIG. 6, translated function _f 1 (q), and the turning point _{P min} that was updated in step S12 described _above, the function _f 1 passing through the _{P max} '(q) Is calculated. In step S14, the calculated f ₁ ′ (q) is redefined as f ₁ (q), and the process proceeds to step S4 in FIG.

In step S15, q _max and V _{h_max} are updated, and the process proceeds to step S16. Specifically, updates the _{q max} as the maximum value the input q, we calculate the _f 2 _{(q max)} for the _{q max} and _{V H_max,} updates the turning point _{P max.}

In step S16, f ₂ (q) is translated, a function f ₂ ′ (q) is calculated, and the process proceeds to step S17. Specifically, as shown in FIG. 6, translated function _f 2 (q), and the turning point _{P max} that was updated in step S15 described _above, the function _f 2 which passes through the _{P min} '(q) Is calculated. In step S17, the calculated f ₂ ′ (q) is redefined as f ₂ (q), and the process proceeds to step S18.

In step S18, f ₂ (q) is moved symmetrically, the corresponding function g ₂ (q) is calculated, and the process proceeds to step S4 in FIG. Specifically, the function g ₂ (q) is calculated by moving the function f ₂ (q) symmetrically with respect to the midpoint I, where I is the midpoint of the straight line connecting the turning points P _min and P _max. To do.

A specific example of this symmetrical movement of f ₂ (q) will be described in detail with reference to FIG. FIG. 7 is a diagram showing a specific example of the symmetrical movement of the function f ₂ (q) in step S18, and shows an example in which the turning points P _min are set to q _min = 0 and V _{h_min} = 0.

First, the function f ₂ (q) passing through the turning points P _min and P _max is moved point-symmetrically with respect to the turning point P _min to calculate the function h ₂ (q). Specifically, in this example, the function h ₂ (q) is calculated as h ₂ (q) = − f ₂ (−q). Next, the function _{h 2 (q), q max} -q min moved parallel to the q-axis direction, move _{V h_max -V h_min} parallel to _{V h} axis direction, it calculates the function _g 2 (q). As described above, the function g ₂ (q) is calculated by moving the function f ₂ (q) symmetrically and parallelly.

<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. 8 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. 9 is a diagram showing changes in displacement and load measured when different voltages are applied to the piezoelectric actuator 10, and 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. 9 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. 9, 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. 10 to 17, 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 FIG. 10 to FIG. 17, 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. 10 and 11 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. FIG. 12 and FIG. 13 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. 14 and 15 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. FIGS. 16 and 17 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. 10 to 17, the solid line indicates the time change 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. 10, 12, 14, and 16, the time variation of 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. 10, 12, 14, and 16, 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. 10, 12, 14, and 16, the displacements are estimated in the regions 70, 72, 74, and 76 surrounded by the broken lines, that is, in the regions where the displacements converge 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. 11, 13, 15, and 17, 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. 11, 13, 15, and 17, 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 FIGS. 11, 13, 15, and 17, 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 embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes a design and the like within a scope not departing 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 diagram showing a hysteresis function configured based on a function _f 1 (q) and _f 2 (q). 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 flowchart which shows the procedure of the hysteresis function update process of the piezoelectric actuator control apparatus which concerns on the said embodiment. Is a diagram showing a hysteresis function configured based on a function _f 1 '(q) and _f 2' (q). It is a diagram showing a specific example of a symmetrical movement of the function f _{2 (q).} 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. FIG.

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 (1)

A piezoelectric device that estimates the displacement and load of the piezoelectric actuator using the voltage and induced charge applied to the piezoelectric actuator as inputs, and sets the voltage or charge amount to be applied to the piezoelectric actuator based on the estimated displacement and load. An actuator control method comprising:
Displacement based on a hysteresis function configured based on a plurality of functions including at least the following two functions f ₁ (q) and f ₂ (q) with the assistance of an actuator model that takes into account the nonlinearity of the piezoelectric actuator And a method of controlling the piezoelectric actuator, wherein the load is estimated.

However, q is a variable, and a ₁ , b ₁ , c ₁ , a ₂ , b ₂ , and c ₂ are constants.

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