STM32-based four-point piezoelectric driving fast oscillating mirror control system

Abstract

The invention discloses a four-point piezoelectric driving fast oscillating mirror control system based on STM32. The four-point piezoelectric driving fast oscillating mirror control system comprises a piezoelectric driving fast oscillating mirror, a PSD position sensitive detector, an AD acquisition module, a DA output module, a piezoelectric driving controller, a piezoelectric actuator, an STM32 control module and a PSD position sensitive detector. An electric signal of an object to be tracked is transmitted back to the STM32 controller through the AD acquisition module, the driving voltage of each piezoelectric ceramic actuator is obtained through an improved ADRC algorithm, then the STM32 controller sends a control signal through the DA output module, and the control of the rotation angle of the fast oscillating mirror is completed through the driving of the piezoelectric ceramic actuators. According to the method, the parallel computing advantage of the STM32 is fully utilized, the system delay is reduced, high-precision, real-time and synchronous multi-piezoelectric compensation and control are realized, and the method is of great significance to researches such as closed-loop testing of a fast oscillating mirror controller, piezoelectric ceramic hysteresis nonlinear modeling and model parameter identification.

Description

Technical Field

[0001] The invention relates to a two-dimensional fast-swing mirror of a piezoelectric ceramic driving element, and in particular to a piezoelectric driven fast-swing mirror control system based on STM32. Background Art

[0002] Large-aperture fast-steering mirrors (FSM) are used to perform high-precision and high-dynamic pointing of the beam propagation direction. As an important component of optoelectronic tracking systems, they have the advantages of fast response speed, high resolution, high precision, and high bandwidth. They are widely used in the fields of line-of-sight stabilization and image motion compensation, optical scanning, optoelectronic stabilization tracking, laser weapons, and space laser communications. FSM is mainly divided into two types according to different driving modes: piezoelectric ceramic drive and voice coil motor drive. Resistive strain displacement sensors and capacitive displacement sensors are used to measure piezoelectric ceramic deformation and fast-steering mirror swing, and closed-loop control is used to achieve fast and precise positioning.

[0003] The FSM driven by piezoelectric ceramics has the characteristics of large output torque and high response bandwidth. It is often used in situations with high frequency band requirements. It is a commonly used driving device for fast swing mirror actuators in image stabilization systems. Compared with voice coil motors (VCA), it has higher resonance frequency and displacement resolution. However, the total stroke of the FSM under this driving mode is small, the driving voltage is large, and its driving circuit is relatively complex. The piezoelectric ceramics themselves have nonlinear characteristics such as hysteresis and creep, which require compensation through software algorithms.

[0004] At present, the most common method for controlling the fast-swing mirror is PID control. This control method has a simple principle, is relatively easy to implement in engineering, and can be applied to most scenarios. However, PID control also has many problems. Since the application scenario of the fast-swing mirror in this patent is optical path stabilization, it requires high control accuracy and is a nonlinear system; therefore, traditional PID linear control is difficult to meet actual work needs.

[0005] STM32 is a powerful chip designed by STMicroelectronics based on the Cortex-M series core. The STM32 series chips have powerful functions, low cost, good performance and easy operation. It also has more abundant I / O resources, which can be easily connected with other modules to achieve the purpose of fast communication. Users can reconfigure the I / O resources of STM32 and select corresponding peripherals such as IIC, SPI, etc. according to their own needs, thereby saving the cost of purchasing additional external devices. The main frequency can reach 72MHz, which enables high-speed and complex hysteresis compensation operations to be stably executed. It is a single-chip microcomputer series with a very high cost performance. Therefore, STM32 is used to complete the piezoelectric drive fast swing mirror control system.

[0006] Active disturbance rejection control (ADRC) technology was proposed by researcher Han Jingqing in 1980. It is a control strategy that relies very little on the mathematical model of the controlled object. It uses feedback control technology to estimate and compensate for internal and external disturbances of the system in real time, achieves precise control of motor output, and has strong robustness.

[0007] Sliding Mode Control (SMC) is a control theory based on modern control theory. The core of sliding film control is to establish a sliding surface, pull the controlled system onto the sliding surface, and make the system move along the sliding surface. The advantage of sliding film control is that it ignores external disturbances and uncertain parameters and takes a more violent approach to achieve the control purpose. Summary of the invention

[0008] In view of the above problems existing in the prior art, the present invention proposes a four-point piezoelectric driven fast-swing mirror control system based on STM32.

[0009] The present invention adopts the following technical solution:

[0010] The invention discloses a four-point piezoelectric driven fast-swing mirror control system based on STM32, comprising a piezoelectric driven fast-swing mirror, a PSD position sensitive detector, an AD acquisition module, a DA output module, a piezoelectric ceramic driver, a piezoelectric ceramic actuator and an STM32 control module; the PSD position sensitive detector transmits an electrical signal of an object to be tracked back to the STM32 controller through the AD acquisition module, and obtains a driving voltage of each piezoelectric ceramic actuator through an improved ADRC algorithm; then the STM32 controller sends a control signal through the DA output module, and the control is completed through the piezoelectric ceramic driver driving the fast-swing mirror.

[0011] Furthermore, the improved ADRC algorithm adopts a linear state error feedback control system based on sliding mode control; the linear state error feedback control system based on sliding mode control is expressed in ADRC as follows:

[0012]

[0013] Where, e represents the system output error, v represents the reference input generated by the tracking differentiator (TD), and z represents the system state estimated by the extended observer (ESO). represents the target value of the controlled quantity; and k are gain coefficients; c is the sliding surface parameter; is the disturbance compensation, which represents the characteristics of the controlled object and can be derived from the initial acceleration of the step object. The larger it is, the weaker the anti-interference ability is. u is the output that directly acts on the controlled object.

[0014] Furthermore, the STM32 control module adopts an improved ADRC algorithm to track the target signal by tracking the differentiator output transition signal, and uses the differential signal of the differentiator output transition signal as the target differential signal. At the same time, the differential signal of the extended state observer ESO output feedback state is introduced as the actual differential signal to achieve effective tracking of the differentiator and avoid jitter problems, so as to improve the stability and robustness of the system.

[0015] Furthermore, the piezoelectric driven fast swing mirror uses a piezoelectric actuator as a driver, drives the mirror surface through a flexible support micro-displacement amplification mechanism, and the two-dimensional deflection of the mirror surface adopts a four-point parallel drive method. Four piezoelectric actuators are distributed in a rectangular shape around the center of the mirror surface.

[0016] Furthermore, the piezoelectric drive controller is connected to the STM32 control module, and the piezoelectric drive controller includes a power supply module, a DA module, an AD module, a sensor module, a servo module, and a drive module, wherein the drive module includes four independent drive channels for parallel driving of four-point piezoelectric ceramic actuators.

[0017] Furthermore, the AD module input is 0~10v, the sampling rate is not less than 20kHZ, and the DA module output is 0~10v.

[0018] Furthermore, the piezoelectric drive controller is connected to the DA output module, and a drive circuit is used to amplify the output voltage of the DA output module, amplifying the analog signal of 0 to 10v into a high-voltage output of 0 to 120v, thereby realizing the driving of the piezoelectric driven fast-swing mirror.

[0019] Furthermore, the PSD position sensitive detector is connected to the STM32 control module and is used for collecting the centroid of the light spot, and helps the fast-swing mirror point to the correct position by converting the optical signal into an electrical signal.

[0020] Furthermore, the piezoelectric actuator is connected to a piezoelectrically driven fast-oscillating mirror, the driving voltage is 0-150V, and piezoelectric ceramics are used as basic components to output displacement and force.

[0021] Furthermore, the piezoelectric-driven fast-oscillating mirror is controlled by four piezoelectric ceramic actuators. When the mirror needs to rotate along the Y-axis, one group of piezoelectric actuators on the same side is maintained, and the other group of piezoelectric actuators on the same side is actuated; when the mirror needs to rotate along the X-axis, one group of diagonal piezoelectric actuators is maintained, and the other group of diagonal piezoelectric actuators is actuated.

[0022] The present invention has the following beneficial effects:

[0023] The present invention makes full use of the parallel computing advantages of STM32, reduces the system calculation delay, improves the system response speed, and realizes high-precision, real-time and synchronous multi-piezoelectric compensation and control. It is of great significance to the closed-loop test of fast-swing mirror controller, piezoelectric ceramic hysteresis nonlinear modeling, model parameter identification and other research. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the working principle diagram of the four-point piezoelectric driven fast-swing mirror mechanism.

[0025] Figure 2 This is the hardware connection diagram of the four-point piezoelectric driven fast-swing mirror control system.

[0026] Figure 3 This is the structural block diagram of the four-point piezoelectric driven fast-swing mirror control system.

[0027] Figure 4 It is the structural block diagram of the ADRC algorithm model.

[0028] Figure 5 It is the block diagram of the improved sliding mode ADRC control principle. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0030] The present invention provides a high-precision, fast-response piezoelectric-driven fast-swing mirror control system based on STM32, the system comprising a piezoelectric-driven fast-swing mirror, a PSD position sensitive detector, an AD acquisition module, a DA output module, a piezoelectric drive controller, a piezoelectric actuator, and an STM32 control module. The hardware connection is as follows: Figure 2 As shown, the system structure is as Figure 3 As shown in the figure, the PSD position sensitive detector transmits the electrical signal of the light spot to be tracked back to the STM32 controller through the AD acquisition module, and obtains the driving voltage of each piezoelectric ceramic actuator through the improved ADRC algorithm. Then the STM32 controller sends a control signal through the DA output module, which is driven by the piezoelectric ceramic driver to complete the control of the fast swing mirror angle.

[0031] In the improved ADRC algorithm designed in the STM32 control module, the tracking differentiator (TD) outputs a transition signal to track the target signal to avoid large initial errors. The tracking differentiator (TD) can output the differential signal of the transition signal as the target differential signal, and at the same time introduce the extended state observer (ESO) to output the differential signal of the feedback state as the actual differential signal, which realizes the effective tracking of the differentiator and avoids the jitter problem, thereby improving the stability and robustness of the system.

[0032] The improved ADRC algorithm adopts a linear state error feedback control system based on sliding mode control (sliding mode control-linear state error feedback, SMC-LSEF) to solve the problems of weak anti-interference ability and poor control performance of PD control in the linear state error feedback control law (LSEF) in the traditional ADRC algorithm.

[0033] Preferably, the four-point piezoelectric driven fast-swing mirror uses a piezoelectric ceramic actuator as an actuator, drives the mirror surface through a flexible support micro-displacement amplification mechanism, and the two-dimensional deflection of the mirror surface adopts a four-point parallel drive method. The four piezoelectric ceramic actuators are distributed in a rectangular shape around the center of the mirror surface.

[0034] Preferably, the piezoelectric driver is connected to the STM32 control module, and the piezoelectric driver includes a power supply module, a DA module, an AD module, a sensor module, a servo module, and a drive module. The drive module includes four independent drive channels for parallel driving of four-point piezoelectric ceramic actuators. The AD module input is 0~10v, and the sampling rate is not less than 20kHZ. The DA module output is 0~10v.

[0035] Preferably, the piezoelectric driver is connected to the 16-bit DAC, and the output voltage of the DAC is amplified by a driving circuit, and the analog signal of 0-10v is amplified to a high-voltage output of 0-120v, thereby realizing the driving of the piezoelectric-driven fast-oscillating mirror. The piezoelectric actuator is connected to the piezoelectric-driven fast-oscillating mirror, the driving voltage is 0-150v, and the piezoelectric ceramic is used as the basic element to output displacement and output.

[0036] Preferably, the position sensitive detector (PSD) is connected to the STM32 control module and is used for collecting the centroid of the light spot, and helps the fast-swing mirror point to the correct position by converting the optical signal into an electrical signal.

[0037] Preferably, the tracking differentiator (TD) in the ADRC algorithm designed in the STM32 control module outputs a transition signal to track the target signal to avoid a large initial error. The tracking differentiator (TD) can output a differential signal of the transition signal as the target differential signal, and at the same time introduce an extended state observer (ESO) to output a differential signal of the feedback state as the actual differential signal, thereby achieving effective tracking of the differentiator and avoiding jitter problems, thereby improving the stability and robustness of the system.

[0038] Preferably, the piezoelectric driven fast swing mirror is controlled by four piezoelectric ceramic actuators. When the reflector needs to rotate along the Y axis, piezoelectric actuators No. 1 and No. 4 are kept, and piezoelectric actuators No. 2 and No. 3 are actuated. Similarly, when the reflector needs to rotate along the X axis, piezoelectric actuators No. 1 and No. 2 are kept, and piezoelectric actuators No. 3 and No. 4 are actuated. Figure 1 shown.

[0039] Preferably, in order to solve the problems of weak anti-interference ability and poor control performance of PD control in the linear state error feedback control law (LSEF) in the traditional ADRC algorithm, a linear state error feedback control system based on sliding mode control (sliding mode control-linear state error feedback, SMC-LSEF) is adopted.

[0040] The present invention adopts ADRC algorithm to overcome the problem that traditional PID algorithm is not quick enough to react to errors and not accurate enough to compensate. Traditional PID algorithm can only compensate and control after the error occurs, while ADRC compensates the observed disturbance to the output end immediately. And through the 16bits DA module circuit output, the piezoelectric ceramic driver drives the four-way piezoelectric ceramic actuator, thereby improving the stability and robustness of the system. Figure 4 shown.

[0041] The traditional PID algorithm is prone to the contradiction between rapidity and overshoot when it comes to step response or when the initial error is large. The ADRC algorithm introduces a tracking differentiator (TD) to output a transition signal to track the target signal to avoid the situation where the initial error is large. Although the D-term differential signal in the traditional PID algorithm has a predictive function, it only subtracts the error of the previous time from the error of this time to obtain a very crude differential result, which is difficult to obtain in practice. The tracking differentiator can output the differential signal of the transition signal as the target differential signal, and at the same time introduce an extended state observer (ESO) to output the differential signal of the feedback state as the actual differential signal. Their difference is the error of the differential action term of ADRC. The discrete mathematical form of the tracking differentiator is shown in formula (1):

[0042] x1(k+1)= x1(k)+T* x2(k)

[0043] x2(k+1)= x2(k)+T* fhan(x1(k)-v,x2(k),r,h) (1)

[0044] Among them, T is the integration step length and the sampling time. Fhan is a non-linear function, also known as the fast control optimal synthesis function, with inputs e = x1 - v, x2, the speed factor r, and the filtering factor h. For this function, the larger r is, the faster the tracking speed; the smaller h is, the better the noise filtering effect.

[0045] The extended state observer can expand the uncertain factors in the system into new state variables and estimate them in real time. The ESO does not require an accurate mathematical model of the controlled object and can well estimate the internal state and uncertain factors of the system based on input-output information. Its mathematical expression is as follows:

[0046] ε1 = z1(k) - y(k)

[0047] z1(k + 1) = z1(k) + h[z2(k) - β01ε1]

[0048] z2(k + 1) = z2(k) + h[z3(k) - β02fal(ε1, 1 / 2, δ) + bu]

[0049] z3(k + 1) = z3(k) + hβ02fal(ε1, 1 / 4, δ)

[0050] Among them, z is the real-time estimated quantity of the internal state variable of the system, and the parameter β is determined by the sampling time and order of the controlled object. The fal(ε1, a, δ) function is a continuous power function, e is the system error, a is the exponent, and δ is the boundary for distinguishing the magnitude of the error e.

[0051] The traditional PID control method generates the control quantity based on the "linear weighted sum" of the error proportion, differential, and integral. Although this method is simple, it may not be the best. Therefore, in ADRC, a non-linear combination method of error state feedback (NLESF) is tried, and the result significantly improves the processing efficiency of system information, and the non-linear feedback coefficient has a wider adaptability. Its mathematical expression is:

[0052] en = vn - zn

[0053] u0 = k1 fal(e1, a1, δ) + k2 fal(e2, a2, δ)

[0054] Among them, a and δ are adjustable parameters. Generally, a1 < 0 < a2 < 1, and δ is generally taken as 0.1 according to engineering experience.

[0055] In addition, in the control quantity u0, the system uncertain factor zn + 1 is compensated, and the non-linear system is converted into an integrator series type system, thus making the control problem of complex objects simpler. The mathematical expression of disturbance compensation is:

[0056]

[0057] Sliding mode control mainly includes the selection of sliding mode switching surface s(x) and the design of sliding mode reaching law u(x). The improved sliding mode ADRC control principle is as follows: Figure 5 As shown. For nonlinear systems, the state space is defined as: = f(x),x∈ ; There is a hyperplane in the state space: s(x)=s(x1, x2, …, xn)=0, which divides the state space into two parts: s>0 and s<0. The points on the switching surface are divided into three types: usually point C, starting point B and end point A. When the points on both sides are close to the switching surface, the motion trajectory of the system will move along s(x)=0 to the ideal state. Therefore, the conditional expression satisfied by the system motion in the sliding mode dynamic zone is:

[0058]

[0059] The sliding surface function is determined as:

[0060]

[0061] Construct a suitable sliding mode control law:

[0062]

[0063] In the formula ≠

[0064] From the above, we can see that the realization of sliding mode motion requires the following three basic conditions to be met: (1) the sliding mode exists; (2) the reachability condition is met ; (3) Meet stability requirements.

[0065] According to the sliding mode control theory, the sliding mode surface is first constructed for the LESF system. Considering the suppression of high-frequency noise and the elimination of steady-state errors, the integral quantity is introduced, so the integral sliding mode surface is defined as:

[0066] s= +c∫ dt

[0067] Where c is the sliding surface parameter, and c>0.

[0068] In order to reduce the movement time of the moving point in the sliding mode dynamic area and ensure a smooth transition process, the exponential reaching law is selected as the sliding mode reaching law of the system, and its form is:

[0069]

[0070] Where: >0, k>0 and both are adjustable; sign() is the sign function.

[0071] According to the Lyapunov stability principle, the stability of the sliding mode control system is judged. According to the selected sliding surface, the Lyapunov function is taken as:

[0072]

[0073] By taking the derivative of the above formula and combining it with the sliding mode approach rate, we can get:

[0074]

[0075] because and k are both greater than 0, so <0 is always valid. According to the Lyapunov stability criterion, after the system state motion point reaches the sliding mode dynamic zone, the sliding mode motion tends to be stable. Therefore, the expression of the improved LSEF in ADRC based on sliding film control is:

[0076]

[0077] In summary, the present invention discloses a four-point piezoelectric ceramic driven fast swing mirror control system based on STM32, including an STM32 control module, a PSD position sensitive detector, an AD acquisition module, a DA output module, a piezoelectric drive controller, a piezoelectric actuator, and a piezoelectric driven fast swing mirror, wherein the piezoelectric driven fast swing mirror is a controlled object. This system makes full use of the characteristics of STM32 parallel processing, and completes the large-caliber fast swing mirror control based on the improved ADRC algorithm; the voltage data transmitted back by the PSD position sensitive detector is collected by the AD acquisition circuit, and the expansion and contraction amount of the piezoelectric ceramic actuator is calculated using the improved ADRC algorithm designed in the system model, and finally output to the STM32 control module through the DA output module, thereby controlling the piezoelectric actuator to drive the fast swing mirror and completing the closed-loop control. The present invention realizes the closed-loop debugging of the controller closed-loop control link and the control algorithm, and has important significance for the closed-loop test of the fast swing mirror controller, the piezoelectric ceramic hysteresis nonlinear modeling, the model parameter identification and other research work.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A four-point piezoelectric driven fast swing mirror control system based on STM32, comprising a piezoelectric driven fast swing mirror, a PSD position sensitive detector, an AD acquisition module, a DA output module, a piezoelectric ceramic driver, a piezoelectric ceramic actuator, and an STM32 control module; characterized in that: The PSD position sensitive detector transmits the electrical signal of the object to be tracked back to the STM32 controller through the AD acquisition module, and obtains the driving voltage of each piezoelectric ceramic actuator through the improved ADRC algorithm. Then the STM32 controller sends a control signal through the DA output module, which is driven by the piezoelectric ceramic driver to complete the control of the fast-swing mirror angle.

2. The four-point piezoelectric driven fast swing mirror control system based on STM32 according to claim 1, characterized in that: The improved ADRC algorithm adopts a linear state error feedback control system based on sliding mode control; the linear state error feedback control system based on sliding mode control in ADRC is expressed as: ； Where e represents the system output error, v represents the reference input generated by the tracking differentiator (TD), and z represents the system state estimated by the extended observer (ESO). represents the target value of the controlled quantity; and k are gain coefficients; c is the sliding surface parameter; is the disturbance compensation, which represents the characteristics of the controlled object and can be derived from the initial acceleration of the step object. The larger it is, the weaker the anti-interference ability is; u is the output that directly acts on the controlled object.

3. The four-point piezoelectric driven fast swing mirror control system based on STM32 according to claim 1, characterized in that: The STM32 control module adopts an improved ADRC algorithm to track the target signal by tracking the differentiator output transition signal, and the differential signal of the differentiator output transition signal is used as the target differential signal. At the same time, the differential signal of the extended state observer ESO output feedback state is introduced as the actual differential signal to achieve effective tracking of the differentiator, avoid jitter problems, and improve the stability and robustness of the system.

4. The four-point piezoelectric driven fast swing mirror control system based on STM32 according to claim 1 is characterized in that: The piezoelectric driven fast swing mirror uses a piezoelectric actuator as a driver, drives the mirror surface through a flexible support micro-displacement amplification mechanism, and the two-dimensional deflection of the mirror surface adopts a four-point parallel drive mode. Four piezoelectric actuators are distributed in a rectangular shape around the center of the mirror surface.

5. The four-point piezoelectric driven fast swing mirror control system based on STM32 according to claim 1, characterized in that: The piezoelectric drive controller is connected to the STM32 control module, and the piezoelectric drive controller includes a power supply module, a DA module, an AD module, a sensor module, a servo module, and a drive module, wherein the drive module includes four independent drive channels for parallel driving of four-point piezoelectric ceramic actuators.

6. The four-point piezoelectric driven fast swing mirror control system based on STM32 according to claim 5, characterized in that: The AD module input is 0~10v, the sampling rate is not less than 20kHZ, and the DA module output is 0~10v.

7. The four-point piezoelectric driven fast swing mirror control system based on STM32 according to claim 1, characterized in that: The piezoelectric drive controller is connected to the DA output module, and a drive circuit is used to amplify the output voltage of the DA output module, and the analog signal of 0-10v is amplified into a high-voltage output of 0-120v, thereby realizing the driving of the piezoelectric drive fast swing mirror.

8. The four-point piezoelectric ceramic driven fast swing mirror control system based on STM32 according to claim 1, characterized in that: The PSD position sensitive detector is connected to the STM32 control module and is used for collecting the centroid of the light spot. It helps the fast-swing mirror point to the correct position by converting the optical signal into an electrical signal.

9. The four-point piezoelectric driven fast swing mirror control system based on STM32 according to claim 1, characterized in that: The piezoelectric actuator is connected to a piezoelectrically driven fast-oscillating mirror, the driving voltage is 0-150V, and piezoelectric ceramics are used as basic components to output displacement and force.

10. The four-point piezoelectric driven fast swing mirror control system based on STM32 according to claim 1, characterized in that: The piezoelectric driven fast swing mirror is controlled by four piezoelectric ceramic actuators. When the mirror needs to rotate along the Y axis, one group of piezoelectric actuators on the same side is maintained, and the other group of piezoelectric actuators on the same side is actuated; when the mirror needs to rotate along the X axis, one group of diagonal piezoelectric actuators is maintained, and the other group of diagonal piezoelectric actuators is actuated.

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