Ultra-low hysteresis switching piezoelectric ceramic independent driving method with integrated feedforward correction

Abstract

This invention discloses an ultra-low hysteresis switching independent drive method for piezoelectric ceramics with integrated feedforward correction. Based on a single-chip microcomputer-controlled switching independent drive, the method uses a simple quadratic polynomial as the hysteresis model to fit the hysteresis curve under independent drive. The inverse hysteresis model, or the inverse of the quadratic function, is then used as input, replacing the linear input voltage, to obtain a linear output response curve. This method significantly reduces hysteresis to 0.82% based on time-sharing independent drive, thereby improving the nonlinearity of devices using piezoelectric actuators and enhancing drive precision.

Description

Technical Field

[0001] The present invention relates to the field of precision micro-displacement platforms, and in particular to an ultra-low hysteresis switching piezoelectric ceramic independent driving method integrated with feedforward correction. Background Art

[0002] Piezoelectric actuators with nanometer-level displacement resolution have rapidly captured the market thanks to their high positioning accuracy and fast response, occupying a crucial position in precision drive systems. However, the hysteresis characteristic of piezoelectric stack actuators severely impacts positioning accuracy.

[0003] In order to reduce hysteresis, many scholars at home and abroad have proposed many methods, including charge drive method, feedforward correction of complex algorithms such as Preisach model, ellipse fitting, etc., closed-loop feedback control, etc. However, there are some shortcomings. For example, the charge drive operation is complicated, the inverse parameters of the feedforward correction of complex algorithms are difficult to solve, and the simple algorithm fitting error is large. Although closed-loop feedback control has high accuracy, the high cost and large space occupation brought by high-precision sensors cannot be ignored.

[0004] Although an existing multi-stack piezoelectric actuator independent time-sharing driving device and method can reduce hysteresis in an open-loop situation, it uses a purely analog circuit method, has poor driving flexibility, and the final hysteresis reduction is still far behind high-precision closed-loop feedback control. Summary of the Invention

[0005] In order to avoid the shortcomings of the above-mentioned existing methods, the present invention provides an ultra-low hysteresis switching piezoelectric ceramic independent driving method with integrated feedforward correction, so as to significantly reduce hysteresis and improve driving accuracy in an open-loop situation.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The present invention discloses an ultra-low hysteresis switch-type piezoelectric ceramic independent driving method with integrated feedforward correction, which is applied to a control system consisting of a single-chip microcomputer (MCU), two high-voltage operational amplifiers, a switch group, and a piezoelectric actuator. The piezoelectric actuator is composed of N piezoelectric ceramic layers, and the switch group is composed of N switches. The piezoelectric ceramic driving method includes:

[0008] Step 1: Driving the boost stage:

[0009] Step 1.1, before driving the i-th piezoelectric ceramic layer upward, the single-chip microcomputer MCU first drives the i-1-th piezoelectric ceramic layer upward using a high-voltage operational amplifier and controls the switch corresponding to the i-th piezoelectric ceramic layer to close; i belongs to [2, N];

[0010] Step 1.2: The MCU sends a linearly increasing drive signal, and another high-voltage operational amplifier boosts part of the drive signal. After disconnecting the switch corresponding to the i-1th piezoelectric ceramic layer, the boosted drive signal is sent to the i-th piezoelectric ceramic layer.

[0011] Step 1.3: The i-th piezoelectric ceramic layer is boosted according to the boosted driving signal, and the switch corresponding to the i+1-th piezoelectric ceramic layer is closed before the boosting is completed;

[0012] Step 1.4: The MCU clears the output of the high-voltage operational amplifier involved in driving the i-1th piezoelectric ceramic layer; and continues to use another high-voltage driver to boost the i-th piezoelectric ceramic layer, thereby completing the boost drive of the i-th piezoelectric ceramic layer;

[0013] Step 1.5: After assigning i+1 to i, return to step 1.1 and execute sequentially until i>N, thereby completing the voltage boost of N piezoelectric ceramic layers;

[0014] Step 2: After the linearly increasing driving signal sent by the single chip microcomputer MCU is changed to a linearly decreasing driving signal, the N-layer piezoelectric ceramic layer is driven in the step-down phase according to the process of step 1;

[0015] Step 3: Draw the hysteresis curve of the piezoelectric actuator;

[0016] Step 4: Based on the symmetry of the piezoelectric actuator, the curvature of each piezoelectric ceramic layer is the same. The hysteresis curve of any layer is fitted using the feedforward correction algorithm to obtain the relationship between the output displacement and the input voltage.

[0017] Step 5: Input a set of linearly growing arithmetic progressions into the relationship formula in sequence within the range of the output displacement, and output a set of voltage values ​​that grow in a curve;

[0018] Step 6: Input a set of linearly decreasing arithmetic progressions into the relationship formula in sequence within the range of the output displacement, and output a set of voltage values ​​that decrease in a curve;

[0019] Step 7: The MCU obtains a driving signal with an increasing curve according to the increasing voltage value of the curve, thereby driving the N-layer piezoelectric ceramic layer in the boost stage according to the process of step 1 to reduce the boost hysteresis of the piezoelectric actuator;

[0020] Step 8: The MCU obtains a driving signal with a decreasing curve according to the voltage value of the decreasing curve, thereby driving the N-layer piezoelectric ceramic layer in the voltage reduction stage according to the process of step 1 to reduce the voltage reduction hysteresis of the piezoelectric actuator.

[0021] The ultra-low hysteresis switching piezoelectric ceramic independent driving method with integrated feedforward correction described in the present invention is also characterized in that the feedforward correction algorithm is a quadratic polynomial fitting algorithm or a high-order polynomial fitting algorithm.

[0022] The present invention provides an electronic device, comprising a memory and a processor, wherein the memory is used to store a program that supports the processor to execute the piezoelectric ceramic driving method, and the processor is configured to execute the program stored in the memory.

[0023] The present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program is configured to execute the steps of the piezoelectric ceramic driving method when the computer program is executed by a processor.

[0024] Compared with the existing technology, the beneficial effects of the present invention are embodied in:

[0025] 1. The present invention proposes an ultra-low hysteresis switching piezoelectric ceramic independent driving method with integrated feedforward correction. A simple and convenient feedforward control algorithm is applied on the basis of the original independent time-sharing drive of multi-layer piezoelectric actuators, which greatly reduces the hysteresis and enables the driven device to obtain better linearity.

[0026] 2. The quadratic polynomial fitting proposed in the present invention is the simplest polynomial fitting, and the inverse parameters are very easy to calculate, which avoids the problem that the previous complex feedforward algorithm is difficult to solve, thereby improving the efficiency of system driving, especially when the inverse function is automatically calculated by the single-chip computer algorithm, which greatly improves the driving speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of the overall control method of the present invention;

[0028] Figure 2 It is the driving waveform of the switching dual op amp driving method;

[0029] Figure 3 The displacement curve of the piezoelectric actuator driven by the switching independent time-sharing method under linear voltage drive;

[0030] Figure 4 The displacement curve of the single-layer piezoelectric ceramic and its polynomial fitting curve;

[0031] Figure 5 This is the piezoelectric ceramic hysteresis curve after being corrected by the ultra-low hysteresis switching piezoelectric ceramic independent driving method integrated with feedforward correction;

[0032] Figure 6 Schematic diagram of the experimental setup. DETAILED DESCRIPTION

[0033] The present invention is further described below with reference to the accompanying drawings and specific embodiments.

[0034] In this embodiment, an ultra-low hysteresis switch-type independent driving method with integrated feedforward correction is applied to a control system consisting of a single-chip microcomputer MCU, two high-voltage operational amplifiers, a switch group and a piezoelectric actuator. The piezoelectric actuator is composed of N layers of piezoelectric ceramic layers, and the switch group is composed of N switches. Figure 1 As shown in the figure, the microcontroller controls the on and off of the switch to control which layer of the piezoelectric ceramic layer is selected. At the same time, the microcontroller also sends a driving waveform to control the motion trajectory of the corresponding piezoelectric ceramic layer. The driving waveform applied to the piezoelectric stack is as follows: Figure 2 As shown; the piezoelectric ceramic driving method includes:

[0035] Step 1: Driving the boost stage:

[0036] Step 1.1: Before driving the i-th piezoelectric ceramic layer upward, the MCU first uses a high-voltage operational amplifier to drive the i-1-th piezoelectric ceramic layer upward, as shown in the following example: Figure 2 t0-t1 in the equation is applied to the first layer of the piezoelectric ceramic through the switch S1, and the switch corresponding to the i-th piezoelectric ceramic layer is controlled to be closed; i belongs to [2,N];

[0037] Step 1.2: The MCU sends a linearly increasing driving signal, and another high-voltage operational amplifier boosts part of the driving signal. After disconnecting the switch corresponding to the i-1th piezoelectric ceramic layer, the boosted driving signal is sent to the i-th piezoelectric ceramic layer. Figure 2 At time t1, the voltage applied to the first layer reaches its maximum value and maintains the same voltage, providing sufficient time margin for the switch to be disconnected. At the same time, switch S2 is closed and another drive signal US2 is applied to the second layer of the piezoelectric ceramic. From t1 to t2, due to the use of two amplifiers, switch S1 has enough time to be disconnected and can be closed at any time between t1 and t2. This can greatly prevent the displacement loss caused by the long switch disconnection time.

[0038] Step 1.3: The i-th piezoelectric ceramic layer is boosted according to the boosted driving signal, and the switch corresponding to the i+1-th piezoelectric ceramic layer is closed before the boosting is completed, as shown in FIG. Figure 2 , switch S3 is closed between t1 and t2, which can reduce the rigid impact caused by the use of the switch;

[0039] Step 1.4: The MCU clears the output of the high-voltage operational amplifier involved in driving the i-1 layer of piezoelectric ceramics, as shown in the following example: Figure 2At t2, the driving signal of amplifier 1 returns to 0 to prepare to drive the third layer; and another high-voltage driver continues to boost the voltage of the i-th piezoelectric ceramic layer, thereby completing the boost drive of the i-th piezoelectric ceramic layer;

[0040] Step 1.5: After assigning i+1 to i, return to step 1.1 and execute sequentially until i>N, thereby completing the voltage boost of N piezoelectric ceramic layers;

[0041] Step 2: After changing the linearly increasing driving signal sent by the MCU to a linearly decreasing driving signal, the N-layer piezoelectric ceramic layer is driven in the step-down phase according to the process of step 1;

[0042] Step 3: Draw the hysteresis curve of the piezoelectric actuator under linear drive, such as Figure 3 As shown;

[0043] Step 4: According to the symmetry of the piezoelectric actuator, the curvature of each piezoelectric ceramic layer is the same. The hysteresis curve of any layer is fitted using the feedforward correction algorithm. The results are as follows: Figure 4 As shown, the quadratic function relationship in which the independent variable is the voltage value and the dependent variable is the displacement value is solved to obtain the relationship between the output displacement and the input voltage; in this embodiment, the feedforward correction algorithm is a quadratic polynomial fitting algorithm or a high-order polynomial fitting algorithm.

[0044] Step 5: When the input voltage is linear, the output displacement S is a curve. Now we want the output displacement to be a straight line. We artificially let S increase linearly. Within the range of the output displacement, we sequentially input a set of linearly growing arithmetic progressions into the relationship. For each input displacement S value, we substitute the obtained quadratic function curve and solve for the corresponding voltage U value. Although the quadratic equation solution is very simple, it still has two sets of real roots. Based on the actual situation of voltage U and the limitation of the output voltage range, we discard the extra real root and retain only one real number solution. Then we output a set of voltage values ​​that increase in a curve.

[0045] Step 6: Input a set of linearly decreasing arithmetic progressions into the relationship formula in sequence within the range of the output displacement, and output a set of voltage values ​​that decrease in a curve;

[0046] Step 7: The MCU obtains a driving signal with an increasing curve according to the increasing voltage value of the curve, thereby driving the N-layer piezoelectric ceramic layer in the boost phase according to the process of step 1 to reduce the boost hysteresis of the piezoelectric actuator;

[0047] Step 8: The MCU obtains the driving signal of the decreasing curve according to the decreasing voltage value of the curve, and then drives the N-layer piezoelectric ceramic layer in the step-down stage according to the process of step 1 to reduce the step-down hysteresis of the piezoelectric actuator. The final effect is as follows Figure 5 shown.

[0048] Example 1: Feedforward correction hysteresis measurement under the switch-type independent drive method;

[0049] Experimental setup such as Figure 6 As shown in the figure, the piezoelectric actuator used is AL1.65*1.65*5D-4F from Japan's NEC company. Seven piezoelectric ceramics are glued together with epoxy resin. Initially, the STM32 microcontroller is used to directly send two 0.1Hz amplitude 2V driving signals under linear voltage drive. The signals are amplified to 82V by the signal amplifier module. After that, the signals are applied to the piezoelectric actuator through the switch group gate layer controlled by the STM32 microcontroller to generate displacement. The displacement is then collected by the eddy current sensor and converted into an electrical signal for output to the data acquisition module. The collected data is analyzed and processed to obtain the Figure 3 The hysteresis curve under linear drive is shown. Then one of the layers is selected for quadratic polynomial fitting to obtain Figure 3 The fitting curve shown in the figure is obtained, and the quadratic function relationship expression with the independent variable being the voltage value U and the dependent variable being the displacement value S is solved:

[0050] S=-0.000000322U 2 +0.00217U+0.0438

[0051] U∈[0,2000] S∈[0,3.139]

[0052] Now we want the output displacement to be a straight line, so we artificially let S increase linearly. We insert a set of linearly increasing arithmetic progression values ​​evenly within the range of the displacement S. In order to better correspond to the DAC output voltage, we choose to insert 2000 arithmetic progression terms, with the first term being 0 and the last term being 3.139. Then, for each input displacement S value, we substitute it into formula 4.1 and solve for the corresponding voltage U value. Since the quadratic equation solution is very simple, there are still two sets of real roots. Based on the actual voltage U, the range of values ​​is 0 to 2000. We discard the extra real root and keep only one real number solution. These two thousand solutions are used as input to the microcontroller DAC output, and the output is Figure 4 The inverse function of the displacement response curve shown in FIG, thereby obtaining a linear output such as Figure 5 The calculated hysteresis is reduced from 2.1% without the feedforward algorithm to 0.82%.

[0053] In summary, this method can be applied to devices that use piezoelectric actuators as drives, such as atomic force microscopes, scanning tunneling microscopes, and piezoelectric deflection mirrors. It can greatly improve nonlinearity, avoid image distortion caused by hysteresis during the reciprocating stroke of the atomic force microscope, and improve driving accuracy.

[0054] In this embodiment, an electronic device includes a memory and a processor. The memory is used to store a program that supports the processor to execute the above-mentioned piezoelectric ceramic driving method. The processor is configured to execute the program stored in the memory.

[0055] In this embodiment, a computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the piezoelectric ceramic driving method are executed.

Claims

1. A method for independently driving an ultra-low hysteresis switching piezoelectric ceramic with integrated feedforward correction, characterized in that: The invention is applied to a control system composed of a single-chip microcomputer (MCU), two high-voltage operational amplifiers, a switch group and a piezoelectric actuator, wherein the piezoelectric actuator is composed of N layers of piezoelectric ceramic layers, and the switch group is composed of N switches; the piezoelectric ceramic driving method includes: Step 1: Driving the boost stage: Step 1.1, before driving the i-th piezoelectric ceramic layer upward, the single-chip microcomputer MCU first drives the i-1-th piezoelectric ceramic layer upward using a high-voltage operational amplifier and controls the switch corresponding to the i-th piezoelectric ceramic layer to close; i belongs to [2, N]; Step 1.2: The MCU sends a linearly increasing drive signal, and another high-voltage operational amplifier boosts part of the drive signal. After disconnecting the switch corresponding to the i-1th piezoelectric ceramic layer, the boosted drive signal is sent to the i-th piezoelectric ceramic layer. Step 1.3: The i-th piezoelectric ceramic layer is boosted according to the boosted driving signal, and the switch corresponding to the i+1-th piezoelectric ceramic layer is closed before the boosting is completed; Step 1.4: The MCU clears the output of the high-voltage operational amplifier involved in driving the i-1th piezoelectric ceramic layer; and continues to use another high-voltage driver to boost the i-th piezoelectric ceramic layer, thereby completing the boost drive of the i-th piezoelectric ceramic layer; Step 1.5: After assigning i+1 to i, return to step 1.1 and execute sequentially until i>N, thereby completing the voltage boost of N piezoelectric ceramic layers; Step 2: After the linearly increasing driving signal sent by the single chip microcomputer MCU is changed to a linearly decreasing driving signal, the N-layer piezoelectric ceramic layer is driven in the step-down phase according to the process of step 1; Step 3: Draw the hysteresis curve of the piezoelectric actuator; Step 4: Based on the symmetry of the piezoelectric actuator, the curvature of each piezoelectric ceramic layer is the same. The hysteresis curve of any layer is fitted using the feedforward correction algorithm to obtain the relationship between the output displacement and the input voltage. Step 5: Input a set of linearly growing arithmetic progressions into the relationship formula in sequence within the range of the output displacement, and output a set of voltage values ​​that grow in a curve; Step 6: Input a set of linearly decreasing arithmetic progressions into the relationship formula in sequence within the range of the output displacement, and output a set of voltage values ​​that decrease in a curve; Step 7: The MCU obtains a driving signal with an increasing curve according to the increasing voltage value of the curve, thereby driving the N-layer piezoelectric ceramic layer in the boost stage according to the process of step 1 to reduce the boost hysteresis of the piezoelectric actuator; Step 8: The MCU obtains a driving signal with a decreasing curve according to the voltage value of the decreasing curve, thereby driving the N-layer piezoelectric ceramic layer in the voltage reduction stage according to the process of step 1 to reduce the voltage reduction hysteresis of the piezoelectric actuator.

2. The ultra-low hysteresis switching piezoelectric ceramic independent driving method with integrated feedforward correction according to claim 1 is characterized in that: The feedforward correction algorithm is a quadratic polynomial fitting algorithm or a high-order polynomial fitting algorithm.

3. An electronic device comprising a memory and a processor, characterized in that: The memory is used to store a program that supports a processor to execute the piezoelectric ceramic driving method according to claim 1 or 2, and the processor is configured to execute the program stored in the memory.

4. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the piezoelectric ceramic driving method according to claim 1 or 2 are executed.

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