A MEMS galvanometer scanning method and a lidar system

Abstract

The present invention belongs to the technical field of lidar scanning control, and discloses a MEMS galvanometer scanning method and a lidar system. The method first establishes a dynamic model of an electrostatically driven MEMS galvanometer with external disturbances, and constructs an adaptive nonsingular terminal sliding mode controller based on a nonlinear extended state observer to achieve trajectory tracking control of the MEMS galvanometer. The lidar system includes devices such as a laser, a MEMS galvanometer, a drive circuit, a voltage amplifier, a controller based on FPGA, and a position sensor, and realizes precise trajectory tracking control of the laser beam based on the MEMS galvanometer scanning method. The MEMS galvanometer scanning method of the present invention enables the system state to converge to the sliding mode surface within a finite time through the adaptive nonsingular terminal sliding mode controller, and does not cause singular value problems, ensuring the stability and accuracy of the MEMS galvanometer during tracking of the scanning trajectory, which is beneficial to improving the quality of lidar imaging.

Description

Technical Field

[0001] The present invention belongs to the technical field of lidar scanning control, and particularly relates to a MEMS galvanometer scanning method and a lidar system. Background Art

[0002] Lidar is widely used in fields such as target detection and autonomous driving. It emits laser light and receives the signal reflected from the target to accurately obtain the distance and speed information of the target. The MEMS galvanometer is the core scanning device in the lidar system and can deflect and control the laser beam. The electrostatically driven MEMS galvanometer consists of several parts such as a mirror surface, a torsion bar, drive electrodes, and a support structure, and has the advantages of fast response speed and low energy consumption.

[0003] The scanning technology based on the MEMS galvanometer greatly affects various important indicators such as the lidar field of view, scanning speed, and imaging effect. Therefore, the high-precision scanning control method of the MEMS galvanometer is crucial for ensuring the high-quality imaging of the lidar. However, the precise control of the MEMS galvanometer faces many challenges in fast scanning and dynamic environments. Since the lidar system has extremely high requirements for the scanning performance of the MEMS galvanometer during operation, the overshoot of the MEMS galvanometer under conventional open-loop control is large and the adjustment time is long, resulting in the transient performance of the MEMS galvanometer under traditional open-loop control being difficult to meet the requirements of high-precision scanning performance.

[0004] In addition, the electrostatically driven MEMS galvanometer drives the mirror surface to twist through the electrostatic force generated by applying a voltage to the bottom drive electrodes to achieve the deflection of the laser. However, the drive voltage of the MEMS galvanometer and the torsion angle have a non-linear relationship, which causes the reflected laser to be difficult to scan the target along the desired trajectory. Although the PID control, as a traditional closed-loop control method, is easy to implement, it is difficult to handle the non-linear dynamics of the MEMS galvanometer. Especially during high-speed or large-range scanning, problems such as response lag and accuracy degradation are likely to occur, and the robustness to external disturbances is poor, resulting in deviations of the reflected laser beam and affecting the imaging effect. Therefore, it is difficult to meet the performance requirements of high-precision scanning in lidar applications.

[0005] Although the first-order sliding mode control is an effective robust control strategy, its chattering problem will affect the scanning accuracy. In the detection of high-speed and dynamic moving targets, the existing galvanometer scanning control technologies are difficult to meet the requirements of high precision and robustness, which restricts the performance of the lidar system. On the other hand, in practical applications, there are model parameter perturbations and external disturbances, which will have an adverse impact on the control effect. Most traditional control methods rely on accurate system models and have problems such as poor anti-interference ability. Factors such as uncertain model parameters and external disturbances will bring difficulties to the precise control of the MEMS galvanometer.

[0006] Therefore, there is an urgent need for a MEMS galvanometer scanning method to achieve precise tracking and scanning of the MEMS galvanometer along a desired trajectory. Summary of the Invention

[0007] The object of the present invention is to propose a MEMS galvanometer scanning method. This method adopts an adaptive nonsingular terminal sliding mode control strategy based on a nonlinear extended state observer, which can solve the problem of precise scanning control of a MEMS galvanometer under parameter uncertainties and disturbances during high-frequency and large-range scanning.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A MEMS galvanometer scanning method includes the following steps:

[0010] Step 1. Establish a dynamic model of an electrostatically actuated MEMS galvanometer with external disturbances.

[0011] Step 2. For the dynamic model of the electrostatically actuated MEMS galvanometer established in Step 1, construct an adaptive nonsingular terminal sliding mode controller based on a nonlinear extended state observer. The construction process includes the design of a nonlinear extended state observer, the design of a nonsingular terminal sliding mode based on the reaching law technique, and the design of adaptive control.

[0012] Step 3. Use the adaptive nonsingular terminal sliding mode controller to achieve trajectory tracking control of the MEMS galvanometer.

[0013] In addition, based on the above MEMS galvanometer scanning method, the present invention also proposes a lidar system.

[0014] The lidar system includes a laser, a MEMS galvanometer, an FPGA-based controller, a position sensor, and a drive circuit.

[0015] A reflecting mirror for adjusting the laser light path is provided between the light source of the laser and the MEMS galvanometer.

[0016] The FPGA-based controller stores a readable storage medium, and when the readable storage medium is executed, it is used to implement the steps of the above-mentioned MEMS galvanometer scanning method.

[0017] The position sensor inputs the detected galvanometer torsion position signal and the desired reference position signal into the FPGA card of the FPGA-based controller in real time. After calculation according to the MEMS galvanometer scanning control method, the FPGA card outputs a voltage control signal, which is amplified by the voltage amplifier of the drive circuit and then input into the bottom and side drive electrodes to drive the MEMS galvanometer to track the desired trajectory for scanning.

[0018] When the light beam reflected by the target is received and recorded by the APD detector, the distance from each light point to the transmitter is measured according to the time-of-flight ranging method of the lidar.

[0019] In addition, based on the above MEMS galvanometer scanning method, the present invention also proposes a computer-readable storage medium with a program stored thereon; when the program is executed by a processor, it is used to implement the steps of the above MEMS galvanometer scanning method.

[0020] The present invention has the following advantages:

[0021] As described above, the present invention relates to a MEMS galvanometer scanning method. Compared with the control strategies under traditional fixed control gains such as PID, the method of the present invention introduces an adaptive technique, which can automatically adjust the control gain according to the disturbance change to improve the scanning and tracking accuracy. In addition, the method of the present invention also adopts a non-singular terminal sliding mode design scheme, which effectively avoids the singularity problem of the conventional terminal sliding mode control in some states, ensuring that the galvanometer scanning process will not cause the problem of unstable control of the galvanometer due to the singularity problem. Furthermore, the method of the present invention also introduces a switching control law, so that the system state has a faster approaching speed when it is far from the sliding surface, and the control law will gradually decrease and suppress the chattering phenomenon when it is close to the system sliding surface. The designed non-linear extended state observer of the present invention can accurately estimate the disturbance existing in the system, and further suppress the chattering phenomenon by compensating and effectively reducing the gain of the switching control law. The MEMS galvanometer scanning method of the present invention adopts the robust non-linear strategy of sliding mode control. Through the adaptive non-singular terminal sliding mode controller, the system state can converge to the sliding surface within a finite time, which is more suitable for the precise scanning control of the MEMS galvanometer in lidar applications, and does not depend on the accurate model parameters of the system. It can keep high precision and stability in large-angle and fast scanning of the MEMS galvanometer under the condition of the existence of disturbance, which is beneficial to improving the quality of lidar imaging. Description of the Drawings

[0022] Figure 1 It is a flowchart of the MEMS galvanometer scanning method in the embodiment of the present invention.

[0023] Figure 2 It is , a schematic diagram of the scanning effect of the MEMS galvanometer controlled by the PID control algorithm when

[0024] Figure 3 It is , a schematic diagram of the scanning effect of the MEMS galvanometer controlled by the MEMS galvanometer scanning method of the present invention when

[0025] Figure 4 It is , Schematic diagram of the disturbance estimation effect when the method of the present invention is adopted.

[0026] Figure 5 is , Schematic diagram of the scanning effect of the MEMS galvanometer controlled by the PID control algorithm when

[0027] Figure 6 is , Schematic diagram of the scanning effect of the MEMS galvanometer controlled by the MEMS galvanometer scanning method of the present invention when

[0028] Figure 7 is , Schematic diagram of the disturbance estimation effect when the method of the present invention is adopted.

[0029] Figure 8 Schematic diagram of the lidar system based on the closed-loop control of the electrostatically actuated MEMS galvanometer in the embodiment of the present invention. Detailed implementation manner

[0030] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners:

[0031] Embodiment 1

[0032] In view of the requirements in MEMS lidar applications that not only require precise trajectory tracking performance but also anti-interference performance, etc., in this embodiment, an adaptive nonsingular terminal sliding mode control MEMS galvanometer scanning method based on a nonlinear extended state observer is proposed to solve the difficult problems faced by traditional control methods. It adopts robust control that does not rely on an accurate system model, and designs a nonlinear extended state observer to estimate the unknown disturbances in the system. By introducing an adaptive technique to estimate the upper bound information of the disturbances, the chattering problem of the sliding mode control is suppressed. At the same time, the reaching law technique is adopted to improve the reaching speed of the system state and suppress the chattering problem. The MEMS galvanometer scanning method of the present invention can make the closed-loop system state converge within a finite time in the presence of external disturbances, improve the response speed and tracking accuracy during the scanning control of the MEMS galvanometer, and thus improve the scanning performance in lidar applications.

[0033] As Figure 1 shown, the MEMS galvanometer scanning method in this embodiment specifically includes the following steps:

[0034] Step 1. Establish a dynamic model of an electrostatically actuated MEMS galvanometer with external disturbances.

[0035] The electrostatically actuated MEMS galvanometer mirror includes a mirror surface, two pairs of torsion bars, a support frame, a frame, and drive electrodes. By applying appropriate voltages to the drive electrodes, the galvanometer mirror can be twisted around the X-axis and Y-axis. The mathematical model of the MEMS galvanometer mirror is expressed as:

[0036] .

[0037] Wherein, and respectively represent the torsion angles of the galvanometer mirror along the axis direction and the axis direction. and are the moments of inertia, and are the damping coefficients, and are the spring coefficients of the torsion bars, and are the electrostatic torsion torques.

[0038] and are respectively expressed as:

[0039] .

[0040] .

[0041] Wherein, represents the silicon density, represents the mirror thickness, represents the width and length of the mirror surface, represents the outer width of the frame, represents the outer length of the frame, represents the inner width of the frame, represents the inner length of the frame.

[0042] and are respectively expressed as:

[0043] .

[0044] .

[0045] Wherein, , and represent the electrostatic torque generated by the bottom drive electrode attracting the mirror surface, , and represent the electrostatic torque caused by the side drive electrode attracting the mirror surface; represents the electrostatic torque generated by the bottom drive electrode attracting the frame.​ and has the following form:

[0046] .

[0047] .

[0048] where represents the air permittivity, and respectively represent the integration regions of the bottom driving electrode and the side driving electrode, , represents the distance between the bottom driving electrode and the mirror surface. is the control voltage applied to the driving electrode, and the driving method is as follows:

[0049] .

[0050] where is the bias voltage, and respectively represent the control voltages of the electrostatically actuated MEMS mirror in the X-axis and Y-axis directions.

[0051] Define , , , , , the dynamic model of the electrostatically actuated MEMS mirror is transformed into:

[0052] .

[0053] where , , , , are system model parameters. In this embodiment , , , , . , respectively represent the driving voltages for controlling the mirror to twist along , angles.

[0054] Considering external disturbances, the dynamic model of the electrostatically actuated MEMS mirror with external disturbances is expressed as:

[0055] .

[0056] where is the state variable of the MEMS galvanometer system, is the control input of the system, is the system output, is the bounded disturbance, satisfying , represents the upper bound of the unknown external disturbance. , , , are the system matrices, respectively expressed as:

[0057] , , , .

[0058] Step 2. For the electrostatically actuated MEMS galvanometer dynamics model established in Step 1, construct an adaptive nonsingular terminal sliding mode controller based on a nonlinear extended state observer. The construction process includes the design of a nonlinear extended state observer, the design of a nonsingular terminal sliding mode based on the reaching law technique, and the design of adaptive control.

[0059] Step 2.1. Design a nonlinear extended state observer to estimate the unknown disturbance in the MEMS galvanometer system.

[0060] Let be the extended state variable, , define , and assume that there exists a positive scalar such that ; define , and then rewrite the electrostatically actuated MEMS galvanometer dynamics model with external disturbance as:

[0061] .

[0062] where, , , , are the system matrices, respectively expressed as:

[0063] , , , .

[0064] According to the electrostatically actuated MEMS galvanometer dynamics model with external disturbance, design the nonlinear extended state observer as:

[0065] .

[0066] where, is the observer state, , , , are respectively the state estimated values of , , . is the observer gain, , , , are respectively the observer parameters of , , . , is a constant; is a non - linear function, defined as:

[0067] .

[0068] Among them, is a constant, satisfying . When the system estimated value is close to the system state, the non - linear function can improve the observation performance of the state non - linear extended state observer.

[0069] Design the observer gain such that is Hurwitz, that is, there exists a positive definite matrix which is the solution of the Lyapunov equation , where represents the identity matrix. At this time, there exists a symmetric positive definite matrix such that:

[0070] .

[0071] Among them, is a suitable symmetric positive definite matrix.

[0072] Define the estimation error of the non - linear extended state observer as:

[0073] .

[0074] Among them, , , , , are respectively the state estimation errors of , , . The estimation error of the non - linear extended state observer is expressed as:

[0075] 。

[0076] Among them:

[0077] 。

[0078] In this embodiment, a Lyapunov function is also introduced to prove the effectiveness of the designed non - linear extended state observer.

[0079] 。

[0080] Derive to obtain:

[0081] 。

[0082] Among them, 。 and are the maximum eigenvalue and the minimum eigenvalue of the matrix respectively. When the estimation error satisfies:

[0083] 。

[0084] Obtain , and the estimation error will converge to a compact set with a radius of .

[0085] Step 2.2. Design a terminal sliding - mode controller according to the disturbance estimation value, so that the system state output can accurately track the reference signal within a finite time.

[0086] Define the error as: , where represents the desired signal. Design a fast non - singular terminal sliding - mode surface as:

[0087] 。

[0088] Among them, the parameters 、 and are positive values, is a constant, satisfying , is the sign function. Define the Lyapunov function as:

[0089] 。

[0090] Once the system state reaches the sliding - mode surface, that is, , obtain .

[0091] For taking the first-order differential gives:

[0092] .

[0093] Among them, , obtain that when , the error can converge to zero in finite time along the non-singular terminal sliding mode surface from any initial position. Taking the first-order differential of the sliding mode surface gives:

[0094] .

[0095] Without considering the perturbation , let , obtain:

[0096] .

[0097] From obtain:

[0098] .

[0099] Substitute into the above formula, obtain:

[0100] .

[0101] Therefore, design the sliding mode equivalent control law as:

[0102] .

[0103] Among them, represents the perturbation estimation value.

[0104] Introduce the adaptive parameter and the perturbation estimation value , the switching control law is designed as:

[0105] .

[0106] Among them, , , , are constants, satisfying , , , .

[0107] The terminal sliding mode controller is designed as follows:

[0108] .

[0109] When the system state is far from the sliding surface, i.e., , through and together to improve the approaching speed of the system state. When the system state is close to the sliding surface, i.e., , the approaching speed of the system state will gradually decrease to suppress the chattering phenomenon.

[0110] Step 2.3. Introduce the adaptive control technology to estimate the upper bound information of the disturbance. Through the adaptive control technology, the control can suppress the disturbance in the system without overestimating the gain, and then an adaptive nonsingular terminal sliding mode controller based on the nonlinear extended state observer is obtained.

[0111] The adaptive parameter is designed as follows:

[0112] .

[0113] Among them, is the adaptive gain, is the adjustable parameter. Such a design can estimate the disturbance through the adaptive parameter and weaken the chattering phenomenon in the sliding mode control.

[0114] Combining the sliding mode equivalent control law and the switching control law, the adaptive nonsingular terminal sliding mode controller constructed by the method of the present invention has the following form:

[0115] .

[0116] Define , , define the error as: , and it is obtained from the stability proof in Step 2.1 that the disturbance estimation error is bounded, .

[0117] After completing the design of the adaptive nonsingular terminal sliding mode controller in Step 2, this embodiment also conducts a stability analysis on the MEMS galvanometer controlled by the adaptive nonsingular terminal sliding mode controller. The specific process is as follows:

[0118] Construct the Lyapunov function as:

[0119] .

[0120] Among them, is a constant, satisfying ; For Taking the first-order differential gives:

[0121] .

[0122] Wherein, .

[0123] Therefore, it is obtained that the system tracking error can reach the terminal sliding mode surface within a finite time, maintain its motion state on the sliding mode surface, and then converge to zero along the sliding mode surface within a finite time.

[0124] Step 3. Use an adaptive non-singular terminal sliding mode controller to achieve trajectory tracking control of the MEMS galvanometer.

[0125] The MEMS galvanometer scanning method of the present invention is for lidar applications. Aiming at the system model of the MEMS galvanometer, the control objective is to design a non-linear extended state observer to estimate the disturbance in the system under the condition of the existence of disturbance. Subsequently, an adaptive non-singular terminal sliding mode control law is designed based on the disturbance estimation value to make the system state quickly and accurately track the desired sinusoidal scanning trajectory, while suppressing the chattering problem, and through the adaptive law, the trajectory tracking error of the MEMS galvanometer can converge to zero within a finite time. By switching the control law, the system state can quickly reach and stay on the sliding mode surface, and at the same time, the influence of the disturbance on the system can be suppressed. When the system state reaches the sliding mode surface, the sliding mode equivalent control law plays a major role and can maintain the sliding mode motion of the system, so as to achieve the tracking control of the laser beam scanning trajectory in the MEMS galvanometer.

[0126] In the lidar application scenario of MEMS galvanometer scanning control, the relationship between the driving voltage and the deflection angle of the galvanometer is non-linear. Conventional control algorithms usually rely on an accurate system model, and factors such as model parameter uncertainty and external disturbance bring difficulties to the precise control of the galvanometer. The present invention adopts the sliding mode control, a robust non-linear strategy, which is more suitable for the precise scanning control of the MEMS galvanometer in lidar applications. The adaptive non-singular terminal sliding mode controller designed by the present invention can make the system state converge to the sliding mode surface within a finite time, and will not bring singular value problems, and by introducing an adaptive technique to estimate the upper bound information of the disturbance, the scanning tracking accuracy is improved, and the stability and accuracy of the tracking scanning trajectory of the MEMS galvanometer are guaranteed, which is beneficial to improving the lidar imaging quality. In addition, the present invention also designs a non-linear extended state observer to estimate the system disturbance and compensates for the system disturbance in the equivalent control law, thereby correspondingly reducing the gain of the switching control law and suppressing the chattering phenomenon. In addition, in order to further suppress the chattering, the method of the present invention introduces a new switching control law, so that when the system state is far from the sliding mode surface, the convergence speed of the system state is increased, and when the system state is close to the sliding mode surface, the switching control law will gradually decrease to suppress the chattering phenomenon.

[0127] In addition, to verify the effectiveness of the method proposed in the present invention, the following specific experiments are also given.

[0128] Figure 2 and Figure 3 are respectively schematic diagrams of the scanning effects of the MEMS galvanometer controlled by the PID control algorithm and the method of the present invention at , . It can be seen that the method of the present invention has a more accurate scanning effect compared with the PID control algorithm and does not produce serious chattering problems. Figure 4 is a schematic diagram of the disturbance estimation effect obtained by using the method of the present invention at , . The observer designed in the present invention can achieve fast and accurate estimation of unknown disturbances. To further verify the control effect, Figure 5 and Figure 6 are respectively schematic diagrams of the scanning effects of the MEMS galvanometer controlled by the PID control algorithm and the method of the present invention at , . It can be seen that at , , the method of the present invention still has accurate scanning effects and anti-disturbance performance. Figure 7 is a schematic diagram of the disturbance estimation effect of the method of the present invention at , . It can be seen that at , , the observer designed in the present invention can still quickly and accurately estimate unknown disturbances.

[0129] It should be noted that the adaptive non-singular terminal sliding mode control in the method of the present invention can also be replaced by high-order sliding mode control. High-order sliding mode control acts on the high-order derivative of the sliding mode with discontinuous control input, retaining the advantages of strong robustness of traditional sliding mode control and weakening the chattering phenomenon of the system. In addition, the electrostatic drive mode of the MEMS micromirror can also be replaced by electromagnetic, piezoelectric and other drive modes. The response speed and power consumption of different drive modes have their own advantages and disadvantages. For example, the displacement is usually small under the piezoelectric drive mechanism, and it is difficult to achieve large-angle scanning. The process design is relatively complex under the electromagnetic drive mechanism.

[0130] Embodiment 2

[0131] This Embodiment 2 proposes a lidar system for adaptive non-singular terminal sliding mode control of a MEMS galvanometer based on a non-linear extended state observer. This system is based on the same inventive concept as the MEMS galvanometer scanning method in Embodiment 1. Based on closed-loop control, through the improvement of the MEMS galvanometer scanning method, precise trajectory tracking scanning of the laser beam is achieved.

[0132] The lidar system includes devices such as a laser, a MEMS galvanometer, a drive circuit, a voltage amplifier, a controller based on a field-programmable gate array (FPGA), and a position sensor. As Figure 8 shown, the lidar system further includes a receiver.

[0133] The drive circuit is the Figure 8 MEMS torsion mirror drive circuit in , which includes a digital-to-analog converter (DAC), a low-pass filter, and an amplifier circuit. The laser preferably uses a He-Ne laser, i.e., a helium-neon laser.

[0134] In this embodiment, a voltage amplifier is used to amplify four groups of drive voltages and then input them into the corresponding four groups of bottom and side drive electrodes for driving the MEMS galvanometer, so that the MEMS galvanometer twists along , the angle.

[0135] Two sets of reflecting mirrors are arranged between the light source of the laser and the MEMS galvanometer for laser optical path adjustment.

[0136] After the FPGA-based controller is programmed using the adaptive nonsingular terminal sliding mode control method in the LABVIEW environment, it is pre-written into the FPGA card, that is, executable code is stored in the FPGA-based controller.

[0137] When the FPGA-based controller runs the executable code, it can implement the steps of the above MEMS galvanometer scanning method.

[0138] The galvanometer torsion position signal detected by the position sensor PSD and the desired reference position signal are input into the FPGA-based controller in real time. After calculation by the control algorithm, the FPGA card will output a corresponding voltage control signal to drive the torsion of the MEMS galvanometer and make the MEMS galvanometer track the desired trajectory for scanning.

[0139] The receiver selects an APD detector. The beam reflected by the target is received and recorded by the APD detector. According to the time-of-flight ranging method of the lidar, the distance of each light point from the laser is measured.

[0140] Embodiment 3

[0141] This Embodiment 3 describes a computer-readable storage medium with a program stored thereon. When the program is executed by a processor, it is used to implement the steps of the MEMS galvanometer scanning method in the above Embodiment 1.

[0142] The computer-readable storage medium may be an internal storage unit of any device or apparatus with data processing capabilities, such as a hard disk or memory, or may be an external storage device of any device with data processing capabilities, such as a plug-in hard disk, a Smart Media Card (SMC), an SD card, a Flash Card, etc. equipped on the device.

[0143] Of course, the above description is only a preferred embodiment of the present invention. The present invention is not limited to listing the above embodiments. It should be noted that all equivalent substitutions and obvious deformation forms made by any person skilled in the art under the teaching of this specification fall within the substantial scope of this specification and should be protected by the present invention.

Claims

1. A MEMS galvanometer scanning method, characterized in that: The steps include: Step 1. Establish a dynamic model of an electrostatically driven MEMS galvanometer with external disturbances; Step 2. For the electrostatically driven MEMS galvanometer dynamics model established in step 1, an adaptive non-singular terminal sliding mode controller based on a nonlinear extended state observer is constructed, and the construction process includes the design of a nonlinear extended state observer, a non-singular terminal sliding mode design based on reaching law technology, and an adaptive control design; Step 3. Using an adaptive non-singular terminal sliding mode controller to realize trajectory tracking control of the MEMS galvanometer; The step 1 is specifically as follows: The dynamic model of electrostatically driven MEMS galvanometer is expressed as: Among them, α and β represent the torsion angle of the galvanometer along the X-axis and Y-axis respectively, J1 and J2 are the moments of inertia, D1 and D2 are the damping coefficients, K1 and K2 are the spring coefficients of the torsion bar, and T α With T β is the electrostatic torsional torque; J1 and J2 are expressed as: Where ρ represents the silicon density, t m Indicates the mirror thickness, L m Indicates the width and length of the mirror, L gw Indicates the outer width of the frame, L gl Indicates the external length of the frame, L gsx Indicates the internal width of the frame, L gsy Indicates the internal length of the frame; T α With T β Respectively expressed as: Where i = 1, 2, 3, 4, and represents the electrostatic torque generated by the bottom driving electrode attracting the mirror, j = 2,3, and represents the electrostatic torque caused by the side driving electrode attracting the mirror; represents the electrostatic torque generated by the bottom driving electrode attracting the frame; and Has the following form: Among them, ∈0 represents the dielectric constant of air, Se i1 and Se i2 Respectively represent the integration area of ​​the bottom driving electrode and the side driving electrode, φ=cos -1 (cosα·cosβ), g represents the distance between the bottom driving electrode and the mirror; V i The control voltage applied to the driving electrode is as follows: Among them, V bias is the bias voltage, V x and V y They represent the control voltages of the electrostatically driven MEMS galvanometer in the X-axis and Y-axis directions respectively; definition x1=α, x3=β, The dynamic model of electrostatically driven MEMS galvanometer is transformed into: Among them, T1, T2, δ, Z α , Z β is the system model parameter, U α , U β Respectively represent the driving voltages for controlling the galvanometer to twist along angles α and β; Considering external disturbances, the dynamic model of the electrostatically driven MEMS galvanometer with external disturbances is expressed as: Where x = [x1, x2] T is the state variable of the MEMS galvanometer system, u is the control input of the system, y is the system output, d is the bounded disturbance, and |d|≤d max , d max represents the upper bound of the unknown external disturbance; A, B, C, E are system matrices, respectively expressed as: C＝[1 0]， 2. The MEMS galvanometer scanning method according to claim 1, characterized in that: The step 2 is specifically as follows: Step 2.

1. Design a nonlinear extended state observer to estimate the unknown disturbance in the MEMS galvanometer system; Step 2.

2. Design a terminal sliding mode controller based on the disturbance estimate; Step 2.

3. Introduce adaptive control technology to estimate the upper bound information of the disturbance, and then obtain an adaptive non-singular terminal sliding mode controller based on a nonlinear extended state observer.

3. The MEMS galvanometer scanning method according to claim 2, characterized in that: The step 2.1 is specifically as follows: Let x t is the extended state variable, x t =d, definition And suppose there is a positive scalar Make definition Then the dynamic model of the electrostatically driven MEMS galvanometer with external disturbance is rewritten as: Among them, A p , B p , C p 、E p is the system matrix, which can be expressed as: C p ＝[1 0 0]， According to the dynamic model of electrostatically driven MEMS galvanometer with external disturbance, the nonlinear extended state observer is designed as follows: in, is the observer state, are x1, x2, x t The state estimate of the observer is L = [l1, l2, l3] T , l1, l2, and l3 are x1, x2, and x t Observer parameters; Z = [0,0,l3 / ε] T , ε is a constant; sigmoid(·) is a nonlinear function, defined as: Where c is a constant, satisfying c>0; Design the observer gain L so that there exists a positive definite matrix P such that P(A p -LC p )+(A p -LC p ) T P = -I solution, where I represents the identity matrix, then there exists a symmetric positive definite matrix Q such that: (A p -LC p ) T Q+Q(A p -LC p )=-H Q ; Among them, H Q is a symmetric positive definite matrix; Defining the estimation error of the nonlinear extended state observer for: in, are x1, x2, x t The state estimation error of The estimation error of the nonlinear extended state observer is expressed as: in:

4. The MEMS galvanometer scanning method according to claim 3, characterized in that: In step 2.1, after completing the design of the nonlinear extended state observer, the Lyapunov function V0 is introduced to perform stability analysis on the nonlinear extended state observer. The specific process is as follows: Taking the derivative of V0, we get: Where ξ0=E p T QE p h 2 +Z T QZ;λ max (·) and λ min (·) are the maximum and minimum eigenvalues ​​of the matrix respectively; when the estimation error satisfy: get Estimation Error Converges to a radius of c α within the tight set.

5. The MEMS galvanometer scanning method according to claim 3, characterized in that: The step 2.2 is specifically as follows: Define the error e as e=yr, where r represents the desired signal; The fast non-singular terminal sliding surface σ is designed based on the reaching law technology: Among them, parameters k1, k2 and k3 are positive values; ω is a constant, satisfying ω>1; sign(·) is a sign function; Define the Lyapunov function V1 as: When the system state reaches the sliding surface, that is, σ=0, we get Taking the first-order differential of V1, we get: in, When σ = 0, the error e can converge to zero from any initial position along the non-singular terminal sliding surface in a finite time; taking the first-order differential of the sliding surface σ, we get: Without considering the disturbance d, let get: From e=yr we get: Substitution get: The sliding mode equivalent control law u0 is designed as: in, represents the disturbance estimate; Introducing adaptive parameters and the disturbance estimate The switching control law u1 is designed as: Among them, M, N, q1, q2 are constants, satisfying M>0, N>0, 0 <q1<1,0<q2<1; The terminal sliding mode controller design is obtained as:

6. The MEMS galvanometer scanning method according to claim 5, characterized in that: The step 2.3 is specifically as follows: Adaptive parameters Designed for: Among them, μ is the adaptive gain, ξ is the adjustable parameter; Combining the sliding mode equivalent control law with the switching control law, an adaptive non-singular terminal sliding mode controller is constructed as follows: definition Define the disturbance estimation error for: The perturbation estimation error is bounded.

7. The MEMS galvanometer scanning method according to claim 6, characterized in that: In step 2, after the design of the adaptive non-singular terminal sliding mode controller is completed, the stability analysis of the MEMS galvanometer system controlled by the adaptive non-singular terminal sliding mode controller is also performed. The specific process is as follows: Construct the Lyapunov function V: Where θ is a constant, satisfying θ>0; taking the first-order differential of V, we get: in, The system tracking error can reach the terminal sliding surface within a finite time, maintain its motion state on the sliding surface, and then converge to zero along the sliding surface within a finite time.

8. A laser radar system, comprising a laser, a MEMS galvanometer, a controller based on FPGA, a position sensor, a drive circuit and a receiver; characterized in that: A reflective mirror surface for adjusting the laser light path is arranged between the laser light source and the MEMS galvanometer; A readable storage medium is stored in the FPGA-based controller, and when the readable storage medium is executed, it is used to implement the steps of the MEMS galvanometer scanning method according to any one of claims 1 to 7; The position sensor inputs the detected galvanometer torsion position signal and the desired reference position signal into the FPGA-based controller in real time. The FPGA-based controller outputs a voltage control signal after calculation according to the MEMS galvanometer scanning method. The driving voltage is amplified by the voltage amplifier of the driving circuit and then input into the bottom and side driving electrodes to drive the MEMS galvanometer to track the desired trajectory for scanning. The receiver uses an APD detector. The light beam reflected by the target is received by the APD detector and the time is recorded, which is used to measure the distance of each light spot from the laser according to the lidar time-of-flight ranging method.

9. A computer-readable storage medium having a program stored thereon; characterized in that: When the program is executed by a processor, it is used to implement the steps of the MEMS galvanometer scanning method described in any one of claims 1 to 7.

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