Buck type DC-DC high-order sliding mode control method and system based on sliding mode observer

Abstract

The invention discloses a Buck type DC-DC high-order sliding mode control method based on a sliding mode observer, and the method is characterized in that the method comprises the following steps: (1) building a Buck converter system model; the Buck converter system model adopts a double closed-loop control structure; (2) establishing a Buck converter state-space equation, and considering comprehensive uncertainty and external interference of the system; (3) designing a high-order sliding mode variable, and carrying out approximation on the comprehensive uncertainty of the system by adopting a self-adaptive sliding mode observer approximation method to obtain an improved control law; and (4) based on the improved control law, comparing the output of the voltage loop as the reference inductive current of the current loop with the real-time feedback current to obtain the error of the current loop, and adjusting the control signal of the Buck converter based on the error. Compared with the prior art, the buffeting problem in traditional sliding mode control can be effectively avoided, meanwhile, high robustness is achieved for system uncertainty and external interference, and it is guaranteed that voltage errors converge to zero within finite time.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and in particular to a Buck-type DC-DC high-order sliding mode control method and system based on a sliding mode observer. Background Art

[0002] Traditional Buck-type DC-DC uses a single closed-loop PI / PID control method or a traditional double closed-loop to control the output of a stable voltage. The characteristics of these methods are only applicable to scenarios with small dynamic disturbances and less drastic load changes. Although their design is simple, their dynamic performance is poor, the regulation speed is slow, and the anti-interference ability is weak. Summary of the Invention

[0003] Object of the Invention: By introducing a high-order sliding mode control method based on a sliding mode observer and using the sliding mode observer approximation method to approximate the comprehensive uncertainty of the system, the chattering problem in traditional sliding mode control can be effectively avoided, thereby achieving higher control accuracy, stronger robustness, and faster dynamic response, meeting the requirements of modern industry for efficient and precise power management.

[0004] Technical Solution: A Buck-type DC-DC high-order sliding mode control method based on a sliding mode observer includes the following steps:

[0005] (1) Establish a Buck converter system model; the Buck converter system model adopts a double closed-loop control structure;

[0006] (2) Establish the state space equation of the Buck converter, and consider the comprehensive uncertainty and external disturbance of the system;

[0007] (3) Design a high-order sliding mode variable, and use the adaptive sliding mode observer approximation method to approximate the comprehensive uncertainty of the system to obtain an improved control law;

[0008] (4) Based on the improved control law, the output of the voltage loop is used as the reference inductor current of the current loop and compared with the real-time feedback current to obtain the error of the current loop, and the control signal of the Buck converter is adjusted based on this error.

[0009] Further, in the Buck converter system model, after the reference voltage is input into the system, it passes through a sliding mode controller to obtain the error of the current loop, and then controls the Buck circuit through a PID controller and a PWM modulator. The current and output voltage of the Buck circuit are sampled and fed back to the sliding mode controller for update and iteration to achieve double closed-loop control.

[0010] Further, the step (2) includes:

[0011] Ideal state space equation of the system:

[0012]

[0013] Among them, V in is the input voltage; V o is the output voltage; L is the energy storage inductor; i L is the inductor current; C is the filter capacitor; R is the load resistor; μ is the switch control function; Considering the comprehensive system uncertainty and external disturbances, the formula is rewritten as follows:

[0014]

[0015] Among them, ΔC, ΔR, ΔL, Δv in , are the capacitor uncertainty, load resistor uncertainty, inductor uncertainty, and input voltage uncertainty respectively; h o , h L are the external disturbances of the output voltage channel and current channel respectively;

[0016] Simplify the above formula into the following form for easy understanding and calculation:

[0017]

[0018] Among them, h 11 , h 12 are the comprehensive system uncertainties. Assume they are bounded, that is, ∣h 11 ∣≤F1, ∣h 12 ∣≤F2; Both F1 and F2 are positive numbers; The expressions of h 11 , h 12 are:

[0019]

[0020] Furthermore, the step (3) includes:

[0021] Assume the system error is defined as x1 = V0 - V r , where V r is the reference voltage, V r is a constant value, V0 represents the actual output voltage, and the derivative of x1 is taken to obtain x2: Take the derivatives of x1 and x2, and after sorting, the formula is obtained:

[0022]

[0023] In the formula:

[0024] Let

[0025] The high-order sliding mode variable s is constructed in the following form: λ > 0 is a design parameter used to adjust the relationship between the error x1 and its derivative; taking the derivative of the above equation gives We get: Combining with the reaching law algorithm, the expression of the control law u is obtained:

[0026]

[0027] sat(s) is the saturation function, and k1 and k2 are positive control gains;

[0028] The adaptive sliding mode observer approximation method is used to approximate the comprehensive uncertainties f1(t) and f2(t) of the system. Through this approximation method, f1(t) and f2(t) are estimated in real time, an improved control law u is designed, and a Lyapunov function V is defined to prove its derivative to ensure the stability of the system.

[0029] Furthermore, the improved control law u is designed, and a Lyapunov function V is defined to prove its derivative Specifically:

[0030] First, a sliding mode observer is designed, and its dynamics are set as:

[0031]

[0032] Where: and are the estimates of f1(t) and f2(t); α1 > 0, α2 > 0, are positive parameters for adjusting the convergence speed of the observer; then the uncertainty approximation error is defined as:

[0033]

[0034] Taking the derivative of the approximation error:

[0035]

[0036] Substituting and into the control law u, the improved control law is:

[0037]

[0038] Substituting into the system dynamics to compensate for the uncertainties f1(t) and f2(t);

[0039] The Lyapunov function is defined as:

[0040]

[0041] Taking the time derivative of V and proving its derivative

[0042] Furthermore, sat(s) is a saturation function, and its specific expression is as follows:

[0043]

[0044] where ρ is the boundary layer parameter of the saturation function, ρ > 0, and sign(s) is the sign function.

[0045] Furthermore, the step (4) includes: referring to the inductor current i r

[0046]

[0047] where Based on the improved control law substitution, i can be obtained r , and the reference inductor current i r obtained from the voltage loop is compared with the real-time feedback current i L sampled to obtain the error x3 of the current loop;

[0048] x3 = i r - i L

[0049] where i L is the actual inductor current, and the formula of the PID controller is:

[0050] M = k p x3 + k i ∫x3dt + k d x3

[0051] where k p , k i , k d are the proportional, integral, and differential control coefficients of the PID controller; M is the output control quantity of the final system to control the Buck converter.

[0052] For the Buck-type DC-DC high-order sliding mode control system based on a sliding mode observer, the system includes a Buck circuit, a DSP controller, a power supply module, a drive module, voltage and current sensors, a PWM modulator, a key input module, a display module, and a system protection module; after the reference voltage is input into the system, it passes through the sliding mode controller to obtain the error of the current loop, and then controls the Buck circuit through the PID controller and the PWM modulator. The current and output voltage of the Buck circuit are sampled and fed back to the sliding mode controller for update and iteration to achieve double closed-loop control;

[0053] Establish the state - space equation of the Buck converter in the sliding - mode controller, and consider the comprehensive uncertainty of the system and external disturbances; design a high - order sliding - mode variable, use the adaptive sliding - mode observer approximation method to approximate the comprehensive uncertainty of the system, and obtain an improved control law; based on the improved control law, the output of the voltage loop is used as the reference inductor current of the current loop, which is compared with the real - time feedback current to obtain the error of the current loop, and the control signal of the Buck converter is adjusted based on this error.

[0054] Further, the design of the high - order sliding - mode variable and the use of the adaptive sliding - mode observer approximation method to approximate the comprehensive uncertainty of the system to obtain the improved control law include:

[0055] Let V in be the input voltage; V o be the output voltage; L be the energy - storage inductor; i L be the inductor current; C be the filter capacitor; R be the load resistor; μ be the switch control function; assume that the system error is defined as x1 = V0 - V r , where V r is the reference voltage, V r is a constant value, and the derivative of x1 is taken to obtain x2: Taking the derivatives of x1 and x2 and after rearrangement, the formula is obtained:

[0056]

[0057] Where: Let

[0058] The high - order sliding - mode variable s is constructed in the following form: λ > 0 is a design parameter used to adjust the relationship between the error x1 and its derivative; taking the derivative of the above formula gives The following is obtained: Combining with the reaching - law algorithm, the expression of the control law u is obtained:

[0059]

[0060] sat(s) is the saturation function, and k1 and k2 are positive control gains;

[0061] Using the adaptive sliding - mode observer approximation method to approximate the comprehensive uncertainties f1(t) and f2(t) of the system, through this approximation method, f1(t) and f2(t) are estimated in real - time, an improved control law u is designed, and a Lyapunov function V is defined to prove that its derivative to ensure the stability of the system.

[0062] Further, based on the improved control law, the output of the voltage loop is used as the reference inductor current of the current loop, which is compared with the real-time feedback current to obtain the error of the current loop. Adjusting the control signal of the Buck converter based on this error includes: the reference inductor current i r

[0063]

[0064] where Substituting the improved control law can obtain i r , the reference inductor current i r obtained from the voltage loop is compared with the real-time feedback current i L sampled to obtain the error x3 of the current loop;

[0065] x3 = i r - i L

[0066] where i L is the actual inductor current, and the PID controller formula is:

[0067] M = k p x3 + k i ∫x3dt + k d x3

[0068] where k p , k i , k d are the proportional, integral, and differential control coefficients of the PID controller; M is the final output control quantity of the system to control the Buck converter.

[0069] Beneficial effects: By detecting the voltage and current signal changes of the circuit through the double closed-loop feedback loop, the voltage loop inputs the difference between the desired output voltage and the feedback voltage into the set sliding mode controller, and the current loop inputs the difference between the reference inductor current and the feedback current into the PID controller. Then, the PWM regulator receives the PWM signal sent by the control circuit to control the on-off time of the MOSFET. Compared with the traditional sliding mode control, this paper uses a high-order sliding mode variable, which can better handle the uncertainties and disturbances in the system. Even in the case of large parameter uncertainties or complex external disturbances, the system can still stably track the sliding mode surface. In addition, the method of approximating the adaptive sliding mode observer used in this paper has strong robustness and does not require a complex training algorithm, making it suitable for real-time applications. Description of the Drawings

[0070] Figure 1 is the Buck circuit topology;

[0071] Figure 2 is the Buck circuit topology when the switch is on;

[0072] Figure 3 It is the Buck circuit topology when the switch is off;

[0073] Figure 4 It is the double closed-loop control structure of the Buck circuit based on the adaptive sliding mode observer;

[0074] Figure 5 It is the output voltage of the Buck simulation model circuit built by the simulation software;

[0075] Figure 6 It is the traditional PID control system built by Simulink;

[0076] Figure 7 It is the double closed-loop control system of the Buck circuit based on the adaptive sliding mode observer;

[0077] Figure 8 It is the simulation model built by the Subsystem subsystem for the double closed-loop control system of this application. Specific implementation mode

[0078] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0079] Example 1

[0080] The Buck-type DC-DC high-order sliding mode control method based on a sliding mode observer includes the following steps:

[0081] (1) Establish a Buck converter system model; the Buck converter system model adopts a double closed-loop control structure;

[0082] (2) Establish the state space equation of the Buck converter, and consider the comprehensive uncertainty and external interference of the system;

[0083] (3) Design a high-order sliding mode variable, and use the adaptive sliding mode observer approximation method to approximate the comprehensive uncertainty of the system to obtain an improved control law;

[0084] (4) Based on the improved control law, the output of the voltage loop is used as the reference inductor current of the current loop to be compared with the real-time feedback current, and the error of the current loop is obtained. Based on this error, the control signal of the Buck converter is adjusted.

[0085] The Buck converter is a step-down DC-DC converter that regulates the output voltage by controlling the on and off states of the switching transistor. The key to its working principle is to store and release energy through an inductor to step down the input DC voltage to the required output voltage while maintaining high efficiency. The Buck control system described in this invention includes a Buck circuit, a DSP controller, a power supply module, a drive module, voltage and current sensors, a PWM modulator, a key input module, a display module, and a system protection module. As Figure 1 shown is the topological structure of the Buck step-down circuit, where V in is the input voltage; V o is the output (capacitor) voltage; L is the energy storage inductor; i L is the inductor current; VT is the MOSFET transistor; VD is the freewheeling diode; C is the filter capacitor; R is the load resistor. This invention analyzes starting from when the switching transistor VT is on and off. When VT is on, the current flows through the inductor L to the capacitor C and the load R, and the inductor is charged at this time. When VT is off, the inductor discharges and continues to supply power to the output resistor, and the diode VD conducts. The increase and decrease amounts of the current on the inductor are equal in the steady state of the circuit, Δi L+ = Δi L- .

[0086] The step (2) studies the Buck converter in the continuous conduction mode (CCM). First, analyze the topological structure of the Buck circuit when the switch is on, as Figure 2 shown. The system state space in the case of the switch being on can be expressed as:

[0087]

[0088] The topological structure of the Buck circuit when the switch is off, as Figure 3 shown. The system state space in the case of it being off can be expressed as:

[0089]

[0090] Combining Equation (1) and Equation (2), the average state space model of the system in an ideal state within one switching period is:

[0091]

[0092] where D is the duty cycle of driving the switching transistor, and the switching control function μ is introduced to drive the signal.

[0093] Assume μ = D, μ ∈ [0, 1], and its expression is:

[0094]

[0095] Thus, according to equations (3) and (4), the average state-space equation of the ideal state of the system can be obtained:

[0096]

[0097] Since there will be certain uncertainties and disturbances in the system, in order to more accurately describe the system, equation (5) can be rewritten in the following form:

[0098]

[0099] where ΔC, ΔR, ΔL, Δv in , are the capacitance uncertainty, load resistance uncertainty, inductance uncertainty, and input voltage uncertainty of the system respectively; h o , h L are the external disturbances of the output voltage channel and the current channel respectively.

[0100] Simplify equation (6) into the following form for easy understanding and calculation:

[0101]

[0102] where h 11 , h 12 are the comprehensive uncertainties of the system. Assume they are bounded, that is, ∣h 11 ∣≤F1, ∣h 12 ∣≤F2. F1 and F2 are both positive numbers. The expressions of h 11 , h 12 are:

[0103]

[0104] The design of the high-order sliding mode variable in step (3):

[0105] Assume that the system error is defined as x1 = V0 - V r , where V r is the reference voltage, V r is a constant value, and V0 represents the actual output voltage. Differentiate x1 to get x2: Differentiate x1 and x2, and after arrangement, the arithmetic formula is obtained:

[0106]

[0107] In the formula: Let

[0108] The f1(t) and f2(t) in this formula can be obtained from h 11 , h 12From the boundedness of, we know that ∣f1(t)∣≤F1 and ∣f2(t)∣≤F2. The high-order sliding mode variable s is constructed in the following form:

[0109]

[0110] where λ>0 is a design parameter used to adjust the relationship between the error x1 and its derivative. Differentiating equation (12) gives:

[0111]

[0112] Substituting equation (10) into (13) gives:

[0113] The Super-Twisting algorithm is a classic method of high-order sliding mode control. By introducing the derivative control of the sliding mode variable, it can effectively reduce chattering and improve control accuracy. The form is:

[0114]

[0115] where: k1 and k2 are positive control gains; is the square root function, which is used to increase the approaching speed and reduce chattering; the integral term ∫sign(s)dt enhances the smoothness of the sliding mode surface. Advantages: The Super-Twisting algorithm is applicable to occasions with high requirements for control accuracy, and can significantly reduce chattering and improve dynamic response.

[0116] By combining equations (14) and (15), the expression of the control law u can be derived:

[0117]

[0118] Due to the existence of system uncertainties and external disturbances, the switching gain required by the controller may become large. In order to provide a continuous transition near the sliding mode surface, effectively reduce the chattering problem of sliding mode control, and improve the dynamic response performance of the system, the saturation function sat(s) is used instead of the sign function sign(s) in the controller design. The specific expression of the saturation function is as follows:

[0119]

[0120] where ρ is the boundary layer parameter of the saturation function, and ρ>0. Thus, the expression of the control law u can be changed to:

[0121]

[0122] Using the adaptive sliding mode observer to approximate f1(t) and f2(t) specifically as:

[0123] Since the control law $u$ in formula (18) contains the unmeasurable system comprehensive uncertainties $f_1(t)$ and $f_2(t)$, the control law cannot be implemented. Therefore, the adaptive sliding mode observer approximation method is used to approximate the system comprehensive uncertainties $f_1(t)$ and $f_2(t)$. This method has strong robustness, does not require a complex training algorithm, and is suitable for real-time applications. The observer actively compensates for uncertainties through the sliding mode mechanism, without the need to precisely know the boundary sizes of $f_1(t)$ and $f_2(t)$, only assuming that they are bounded.

[0124] Through this approximation method, the real-time estimation of $f_1(t)$ and $f_2(t)$ is carried out, an improved control law $u$ is designed, and a Lyapunov function $V$ is defined to prove its derivative to ensure the stability of the system. First, a sliding mode observer is designed, and its dynamics are set as:

[0125]

[0126] where: and are the estimations of $f_1(t)$ and $f_2(t)$; $\alpha_1\gt0$, $\alpha_2\gt0$, are positive parameters for adjusting the convergence speed of the observer.

[0127] Then the uncertainty approximation error is defined as:

[0128]

[0129] Take the derivative of the approximation error:

[0130]

[0131] Substitute and into the control law $u$, and the designed improved control law is:

[0132]

[0133] Substitute it into the system dynamics to compensate for the uncertainties $f_1(t)$ and $f_2(t)$.

[0134] Define the Lyapunov function as:

[0135]

[0136] Take the time derivative of $V$:

[0137]

[0138] Since the system error is small enough, that is, $\Delta f_1(t)$ is small enough so that its influence on the system can be ignored. So the approximation error of $\Delta f_1(t)$ is almost zero.

[0139] After rearrangement, we can get:

[0140] Since k1 > 0 and k2 > 0, and s is the sliding mode surface variable, the first and second terms on the right side of the equation are: -k2s∫sat(s)dt ≤ 0. Additionally, among the third and fourth terms is bounded, that is As long as appropriate α1 and α2 are selected, the influence of these two terms can be ignored, and ultimately the system still tends to be stable. Therefore:

[0141]

[0142] Therefore, the system is asymptotically stable under closed-loop, and the sliding mode surface variable s = x2 + λx1 converges to zero, thus achieving the effective compensation and control objectives for f1(t) and f2(t).

[0143] In step (4), since the system adopts a double closed-loop control structure, the output of the voltage loop serves as the reference inductor current of the current loop. According to equation (5), we have:

[0144]

[0145] where μ can be obtained according to the equation can be calculated. So Substituting into equation (26), i r can be obtained. The reference inductor current i r obtained from the voltage loop is compared with the real-time feedback current i L sampled to obtain the error x3 of the current loop.

[0146]

[0147] In the formula, i L is the actual inductor current. The PID controller formula is:

[0148] M = k p x3 + k i ∫x3dt + k d x3 (28)

[0149] where k p 、k i 、k d are the proportional, integral, and derivative control coefficients of the PID controller; M is the final output control quantity of the system to control the Buck converter.

[0150] The parameters of the Boost converter used in the present invention are shown in the following table:

[0151]

[0152]

[0153] As Figure 5 Shown is the Buck simulation model circuit built with Matlab-Simulink simulation software. The red line Vo1 is the output voltage of the control system described in this article, and the blue line Vo2 is the output voltage of the traditional PID control. Through simulation, it can be proved that the control method described in this article can achieve a faster response speed, and when adjusting the target value, it can reach the steady state more quickly. Compared with PID control, sliding mode control can reduce the overshoot phenomenon of the system and reduce oscillations when approaching the target value. In addition, the method described in this article has strong robustness and can effectively cope with external interference or parameter uncertainty in the system, and stably output to the target voltage of 20V in a short time, while the PID control method will show large fluctuations near the target voltage. Figure 6 Is the traditional PID control system built by Simulink; Figure 7 Is the Buck circuit double closed-loop control system based on an adaptive sliding mode observer; Figure 8 Is the simulation model built by the Subsystem subsystem for the double closed-loop control system of this application.

[0154] Embodiment 2:

[0155] A Buck-type DC-DC high-order sliding mode control system based on a sliding mode observer. The system includes a Buck circuit, a DSP controller, a power supply module, a drive module, voltage and current sensors, a PWM modulator, a key input module, a display module, and a system protection module; after the reference voltage is input into the system, it passes through the sliding mode controller to obtain the error of the current loop, and then controls the Buck circuit through the PID controller and the PWM modulator. The current and output voltage of the Buck circuit are sampled and fed back to the sliding mode controller for update and iteration to achieve double closed-loop control;

[0156] In the sliding mode controller, establish the state space equation of the Buck converter, and consider the comprehensive uncertainty and external interference of the system; design a high-order sliding mode variable, and use the adaptive sliding mode observer approximation method to approximate the comprehensive uncertainty of the system to obtain an improved control law; based on the improved control law, the output of the voltage loop is used as the reference inductor current of the current loop to compare with the real-time feedback current to obtain the error of the current loop, and the control signal of the Buck converter is adjusted based on this error.

[0157] The present invention discloses a Buck-type DC-DC high-order sliding mode control method based on a sliding mode observer. First, an ideal state space equation is constructed for the Buck converter. Considering the uncertainties and external disturbances existing in the system, a combination of a high-order sliding mode variable and the Super-Twisting algorithm is adopted, and then a saturation function is used to replace the sign function in the algorithm. Compared with the prior art, it can effectively avoid the chattering problem in traditional sliding mode control, and at the same time has strong robustness to system uncertainties and external disturbances, ensuring that the voltage error converges to zero within a finite time. The present invention uses an adaptive sliding mode observer approximation method to approximate the comprehensive uncertainties of the system. The characteristics of this method are that it has strong robustness to the uncertainties and disturbances of the system. Compared with complex neural networks or other adaptive approximation methods, it does not have complex training algorithms and is suitable for real-time application scenarios. Most importantly, the observer actively compensates for uncertainties through the sliding mode mechanism.

Claims

1. A Buck-type DC-DC high-order sliding mode control method based on a sliding mode observer, characterized in that Including the following steps: (1) Establish a Buck converter system model; the Buck converter system model adopts a double closed-loop control structure; (2) Establish the state-space equation of the Buck converter, and consider the comprehensive system uncertainty and external disturbances; (3) Design a high-order sliding mode variable, and use the adaptive sliding mode observer approximation method to approximate the comprehensive system uncertainty to obtain an improved control law; (4) Based on the improved control law, the output of the voltage loop is used as the reference inductor current of the current loop and compared with the real-time feedback current to obtain the error of the current loop, and the control signal of the Buck converter is adjusted based on this error.

2. The Buck-type DC-DC high-order sliding mode control method based on a sliding mode observer according to claim 1, wherein, In the Buck converter system model, after the reference voltage is input into the system, it passes through a sliding mode controller to obtain the error of the current loop, and then controls the Buck circuit through a PID controller and a PWM modulator. The current and output voltage of the Buck circuit are sampled and fed back to the sliding mode controller for update and iteration to achieve double closed-loop control.

3. The Buck-type DC-DC high-order sliding mode control method based on a sliding mode observer according to claim 1, characterized in that The step (2) includes: Ideal state-space equation of the system: Among them, V in is the input voltage; V o is the output voltage; L is the energy storage inductor; i L is the inductor current; C is the filter capacitor; R is the load resistor; μ is the switch control function; Considering the comprehensive uncertainty of the system and external disturbances, the formula is rewritten as follows: where ΔC, ΔR, ΔL, Δv in , are capacitance uncertainty, load resistance uncertainty, inductance uncertainty, and input voltage uncertainty, respectively; h o , h L are external interferences of the output voltage channel and the current channel, respectively; The above equation is simplified into the following form for easy understanding and calculation: where h 11 and h 12 are the system comprehensive uncertainties. Assuming they are bounded, i.e., ∣h 11 ∣≤F1, ∣h 12 ∣≤F2; both F1 and F2 are positive numbers; the expressions of h 11 and h 12 are as follows:

4. The Buck-type DC-DC high-order sliding mode control method based on a sliding mode observer according to claim 3, characterized in that, The step (3) includes: Suppose the systematic error is defined as x1 = V0 - V r , where V r is the reference voltage, V r is a constant value, V0 represents the actual output voltage, and taking the derivative of x1 gives x2: Taking the derivative of x1 and x2 and after rearrangement, the formula is obtained: In the formula: Let The high-order sliding-mode variable s is constructed in the following form: λ > 0 is a design parameter used to adjust the relationship between the error x1 and its derivative. Differentiating the above equation gives We obtain: Combining with the reaching law algorithm, the expression of the control law u is obtained: sat(s) is a saturation function, and k1 and k2 are positive control gains; An adaptive sliding mode observer approximation method is used to approximate the overall system uncertainties \(f_1(t)\) and \(f_2(t)\). Through this approximation method, \(f_1(t)\) and \(f_2(t)\) are estimated in real time. An improved control law \(u\) is designed, and a Lyapunov function \(V\) is defined to prove its derivative to ensure the stability of the system.

5. The Buck-type DC-DC high-order sliding mode control method based on a sliding mode observer according to claim 4, characterized in that The design improves the control law \(u\), and defines a Lyapunov function \(V\) to prove its derivative Specifically: First, design a sliding mode observer, whose dynamics are set as: Wherein: and are the estimates of f1(t) and f2(t); α1 > 0, α2 > 0, are positive parameters for adjusting the convergence rate of the observer; then the uncertainty approximation error is defined as: Derive the approximation error: Bring and into the control law u, and the improved control law is designed as: Substitute it into the system dynamics to compensate for the uncertainties f1(t) and f2(t); Define the Lyapunov function as: Take the time derivative of V and prove its derivative 6. The Buck-type DC-DC high-order sliding mode control method based on a sliding mode observer according to claim 4, characterized in that, sat(s) is a saturation function, and its specific expression is as follows: Where ρ is the boundary layer parameter of the saturation function, ρ > 0, and sign(s) is the sign function.

7. The Buck-type DC-DC high-order sliding mode control method based on a sliding mode observer according to claim 5, characterized in that, The said step (4) includes: referring to the inductor current i r Among them Based on the improved control law substitution, \(i\) can be obtained r , the reference inductor current \(i\) obtained from the voltage loop r is compared with the real-time feedback current \(i\) obtained by sampling L to obtain the error \(x3\) of the current loop; x3 = i r -i L where i L is the actual inductor current, and the PID controller formula is: M = k p x3 + k i ∫x3dt + k d x3 where k p , k i , k d are the proportional, integral, and derivative control coefficients of the PID controller; M is the output control quantity of the final system to control the Buck converter.

8. Buck-type DC-DC high-order sliding mode control system based on a sliding mode observer, characterized in that, The system includes a Buck circuit, a DSP controller, a power supply module, a drive module, voltage and current sensors, a PWM modulator, a key input module, a display module, and a system protection module; after the reference voltage is input into the system, it passes through a sliding mode controller to obtain the error of the current loop, and then controls the Buck circuit through a PID controller and a PWM modulator. The current and output voltage of the Buck circuit are sampled and fed back to the sliding mode controller for update and iteration to achieve double closed-loop control; In the sliding mode controller, establish the state-space equation of the Buck converter, and consider the comprehensive system uncertainty and external disturbances; design a high-order sliding mode variable, and use the adaptive sliding mode observer approximation method to approximate the comprehensive system uncertainty to obtain an improved control law; Based on the improved control law, the output of the voltage loop is used as the reference inductor current of the current loop and compared with the real-time feedback current to obtain the error of the current loop, and the control signal of the Buck converter is adjusted based on this error.

9. The Buck-type DC-DC high-order sliding mode control system based on a sliding mode observer according to claim 8, characterized in that, The design of the high-order sliding mode variable and the use of the adaptive sliding mode observer approximation method to approximate the comprehensive system uncertainty to obtain an improved control law include: Let V in be the input voltage; Z o be the output voltage; L be the energy storage inductor; i L be the inductor current; C be the filter capacitor; R be the load resistor; μ be the switch control function; assume the system error is defined as x1 = V0 - V r , where V r is the reference voltage, V r is a constant value, and the derivative of x1 is taken to obtain x2: The derivatives of x1 and x2 are taken and the equation is sorted out to obtain the formula: Wherein: Let The high-order sliding mode variable s is constructed in the following form: λ > 0 is a design parameter used to adjust the relationship between the error x1 and its derivative; differentiating the above equation gives We get: Combining with the reaching law algorithm, the expression of the control law u is obtained: sat(s) is a saturation function, and k1 and k2 are positive control gains; An adaptive sliding mode observer approximation method is used to approximate the comprehensive uncertainties \(f_1(t)\) and \(f_2(t)\) of the system. Through this approximation method, \(f_1(t)\) and \(f_2(t)\) are estimated in real time, an improved control law \(u\) is designed, and a Lyapunov function \(V\) is defined to prove its derivative to ensure the stability of the system.

10. The Buck-type DC-DC high-order sliding mode control system based on a sliding mode observer according to claim 9, characterized in that, Based on the improved control law, the output of the voltage loop is used as the reference inductor current of the current loop, which is compared with the real-time feedback current to obtain the error of the current loop. Adjusting the control signal of the Buck converter based on this error includes: the reference inductor current i r Among them Based on the substitution of the improved control law, \(i\) can be obtained r , the reference inductor current \(i\) obtained from the voltage loop r is compared with the real-time feedback current \(i\) obtained by sampling L to obtain the error \(x3\) of the current loop; x3 = i r -i L where i L is the actual inductor current, and the PID controller formula is: M = k p x3 + k i ∫x3dt + k d x3 where k p , k i , k d are the proportional, integral, and derivative control coefficients of the PID controller; M is the output control quantity of the final system to control the Buck converter.

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