Control system of liquid electric energy feedback suspension system based on expansion observation and sliding mode control

Abstract

The invention discloses a control system of a hydraulic-electric energy feedback suspension system based on expansion observation and sliding-mode control, which is characterized in that an expansion state observer estimates disturbance and transmits the disturbance to a sliding-mode controller, and the controller output and input of the sliding-mode controller are input to the hydraulic-electric energy feedback suspension system; the liquid electric energy feedback suspension system feeds back the state vector to the expansion state observer and the sliding mode controller; the extended state observer is responsible for sensing and quantizing disturbance in real time and providing feed-forward compensation; the sliding mode control provides robust feedback through the design of a sliding mode surface; through collaborative design of disturbance estimation and compensation and robustness enhancement, nonlinearity, uncertainty and external interference in a complex system are coped with together, buffeting is reduced, precision is improved, and adaptability to complex disturbance is enhanced. The real-time observation of the signal is realized by using the extended state observer, and the control rate is continuous, so that the chattering phenomenon can be effectively eliminated, and the robust performance for the uncertainty and interference of the system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of control systems for a liquid-electric energy-feeding suspension system, in particular to a control system for a liquid-electric energy-feeding suspension system based on expansion observation and sliding mode control. Background Art

[0002] As a key component of a vehicle's propulsion system, the performance of the suspension directly impacts ride comfort, handling stability, and driving safety. Consequently, the demands placed on suspension systems are becoming increasingly stringent. Currently, active or semi-active control methods are widely recognized for improving suspension performance. Compared to passive suspension, semi-active suspension boasts a simpler structure, faster response, greater robustness, and improved controllability, and is widely used in suspension control research.

[0003] Sliding mode control is essentially a nonlinear control method that is extremely robust to parameter uncertainty and external disturbances, and its implementation is simple and rapid. However, this control method has certain drawbacks. Specifically, once the state trajectory reaches the sliding mode surface, it is difficult to strictly follow the sliding mode surface to the equilibrium point, which can lead to chattering. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a control system for a hydraulic-electric energy-feeding suspension system based on expansion observation and sliding mode control, so as to avoid the buffeting phenomenon of the hydraulic-electric energy-feeding suspension system.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a control system for a hydraulic-electric energy-feeding suspension system based on extended observation and sliding mode control, wherein an extended state observer estimates disturbances and transmits them to a sliding mode controller, a controller output u of the sliding mode controller is input to the hydraulic-electric energy-feeding suspension system, and the hydraulic-electric energy-feeding suspension system feeds back a state vector to the extended state observer and the sliding mode controller;

[0006] The state space expression of the hydraulic-electric energy-feeding suspension system is:

[0007]

[0008] State vector

[0009] Among them, m s is the sprung mass, z s is the sprung mass displacement, z us is the unsprung mass displacement, k is the spring stiffness, |d z |≤d0 is the disturbance estimated by the extended state observer; d0 is the disturbance of the hydraulic-electric energy-feedback suspension system.

[0010] The extended state observer is designed as follows:

[0011]

[0012] Where: and is the observer state, the observation error ε>0, α1, α2 and α3 are positive real numbers; y is the output of the hydraulic-electric energy-feeding suspension system.

[0013] In the sliding mode controller, the tracking error e1(t) is: e1(t)=x1-x d (t);

[0014] Where: x d (t) is the preset trajectory signal;

[0015] The designed sliding surface s is:

[0016]

[0017] In the formula: t1>0, t2>0 are constants, and q<p is a positive odd number.

[0018] Preferably,

[0019] In the extended state observer, the observation error state equation is:

[0020]

[0021] Preferably, in the extended state observer, the Lyapunov function V of the extended state observer is defined as:

[0022] V=εη T Pη; where: P is a symmetric positive definite matrix.

[0023] Preferably, in the sliding mode controller, the Lyapunov function V1 of the sliding mode observer is defined as:

[0024]

[0025] Preferably, in the sliding mode controller, the controller output u is:

[0026]

[0027] and λ are constants greater than zero.

[0028] The beneficial effects of the present invention are as follows: In the present invention, the extended state observer is responsible for real-time perception and quantification of disturbances, providing feedforward compensation; the sliding mode control provides robust feedback through the design of the sliding surface; the two, through the collaborative design of disturbance estimation and compensation and robustness enhancement, jointly address nonlinearity, uncertainty, and external interference in complex systems, reducing chattering, improving accuracy, and enhancing adaptability to complex disturbances. The extended state observer is used to achieve real-time signal observation and construct a global fast terminal sliding mode. Its control rate is continuous and does not include switching terms, which can effectively eliminate chattering, improve robustness to system uncertainty and interference, and avoid chattering. The extended observer can reconstruct and estimate the state of unknown nonlinear systems, requiring minimal known system information. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the input and output schematic diagram of the extended state observer, sliding mode controller, and suspension system;

[0030] Figure 2 It is a two-degree-of-freedom 1 / 4 vehicle hydraulic-electric energy-feedback suspension system model;

[0031] Figure 3 It is a B and C grade road surface incentive;

[0032] Figure 4 It is the time domain response diagram of vertical vehicle acceleration under Class B road surface;

[0033] Figure 5 This is the time domain response diagram of suspension dynamic deflection under Class B road surface;

[0034] Figure 6 This is the time domain response diagram of tire dynamic load under Class B road surface;

[0035] Figure 7 This is the time domain response diagram of vertical vehicle acceleration under Class C road surface;

[0036] Figure 8 This is the time domain response diagram of suspension dynamic deflection under Class C road surface;

[0037] Figure 9 This is the time domain response diagram of tire dynamic load under Class C road surface. DETAILED DESCRIPTION

[0038] The present invention will now be described in further detail with reference to the accompanying drawings and preferred embodiments. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0039] like Figure 1Figure 1 shows a control system for a hydraulic-electrically powered suspension system based on extended observation and sliding mode control. The extended state observer estimates disturbances and transmits them to the sliding mode controller. The sliding mode controller's controller output, u, is input to the hydraulic-electrically powered suspension system, which then feeds back its state vector to the extended state observer and sliding mode controller. The hydraulic-electrically powered suspension system feeds back state signals, such as displacement, pressure, and current, to the extended state observer and sliding mode controller. The extended state observer uses the suspension system's state output to control input variables, estimating the system state, the extended disturbance state, and the total disturbance, and then transmits the estimated disturbance value to the sliding mode controller. The sliding mode controller generates control signals u for the hydraulic actuator and the power supply circuit based on the desired suspension displacement Zs, the estimated system state, and the disturbance signal, thereby driving the hydraulic-electrically powered suspension system.

[0040] The method for designing a control system of a hydraulic-electric energy-feeding suspension system based on extended observation and sliding mode control includes the following steps:

[0041] Step 1, such as Figure 2 As shown in the figure, a two-degree-of-freedom 1 / 4 vehicle hydraulic-electric energy-feeding suspension model is established, and the dynamic equation of the hydraulic-electric energy-feeding suspension system is constructed.

[0042] According to Newton's second law, the dynamic equation of the hydraulic-electric energy-feedback suspension system is established:

[0043]

[0044] Where: m s is the sprung mass, m us is the unsprung mass, z s is the sprung mass displacement, z us is the unsprung mass displacement, z t is the road excitation displacement, k is the spring stiffness, k t is the tire stiffness, c t is the damping coefficient, and u is the control force of the suspension system.

[0045] State vector X s for:

[0046]

[0047] Changes in passengers and cargo will cause changes in sprung mass and moment of inertia. Aging and deformation of the shock absorber will also cause parameter inaccuracies. Considering that the control target is mainly the movement of the sprung mass and taking into account the uncertainty of the main parameters, Equation (1) can be decoupled as follows:

[0048]

[0049] Where: m s r =ms +Δm s , k1 r =k1+Δk1, sprung mass m s and stiffness k1 are known constant parameters, g z (·) is the nonlinear part, |d z |≤d0 is the disturbance estimated by the extended state observer; d0 is the disturbance of the hydraulic-electric energy-feedback suspension system.

[0050] The state space expression of the hydraulic-electric energy-feeding suspension system is:

[0051]

[0052] To simplify the state space expression of the hydraulic-electric energy-feeding suspension system, A and f(x) are defined as:

[0053]

[0054] The final state space expression of the hydraulic-electric energy-feeding suspension system is:

[0055]

[0056] Step two involves designing an extended state observer (ESO). This observer implements real-time signal observation and constructs fast terminal sliding modes, improving robustness to system uncertainties and disturbances while avoiding chattering. The extended observer can reconstruct and estimate the state of an unknown nonlinear system, requiring minimal known system information.

[0057] To design the extended state observer, formula (6) can be written as:

[0058]

[0059] Where,

[0060]

[0061] The extended state observer can be designed as:

[0062]

[0063] Where: and is the observer state, ε>0, α1, α2 and α3 are positive real numbers, and y is the output of the hydraulic-electric energy-feeding suspension system.

[0064] The observation error state equation can be written as:

[0065]

[0066] Where:

[0067] η is the observation error, represents the observation error gain, represents the rate of change of disturbance.

[0068] In the extended state observer, the Lyapunov function V of the extended state observer is defined as:

[0069] V=εη T Pη (12);

[0070] Where: P is a symmetric positive definite matrix.

[0071] The time derivative of V is:

[0072]

[0073] Where: Q is a symmetric positive definite matrix, λ min (Q) is the minimum eigenvalue of Q.

[0074] Step 3: Design a sliding mode controller. In the sliding mode controller, the tracking error e1(t) is:

[0075] e1(t)=x1-x d (t)(14), that is, e1=x1-x d ;

[0076] Where: x d (t) is the preset trajectory signal.

[0077] The time derivative of e1(t) is:

[0078] Right now The designed sliding surface s is:

[0079]

[0080] In the formula: t1>0, t2>0 are constants, and q<p is a positive odd number.

[0081] The Lyapunov function V1 in the sliding mode controller can be selected as:

[0082]

[0083] The controller output u of the designed sliding mode controller is:

[0084]

[0085] and λ are constants greater than zero.

[0086] The time derivative of V1 is:

[0087]

[0088] Step 4: Conduct road surface evaluation. Figure 3 As shown, road surfaces of grade B and C were selected, the vehicle speed was set to 20 m / s, and the established quarter-vehicle suspension model was run in MATLAB. Vertical body acceleration, suspension dynamic deflection, and tire dynamic load were selected as evaluation indicators. Road roughness was classified into eight levels using the road surface power spectral density, as shown in Table 1.

[0089] Table 1 Road surface roughness classification standards

[0090]

[0091] like Figure 4-Figure 9 As shown in the figure, a comparison analysis of the electrohydraulic energy-feeding suspension system (ESO-FTSMC, red line) controlled by the control system of the present invention is performed with a passive suspension (blue line) and a traditional sliding mode control (green line). Under excitation from Class B and Class C road surfaces, the electrohydraulic energy-feeding suspension system controlled by the control system of the present invention significantly improves vertical vehicle acceleration, suspension dynamic deflection, and tire dynamic load compared to passive suspension control and traditional sliding mode control. The simulation results verify the effectiveness of the control system and achieve the intended design objectives, as shown in Tables 2 and 3.

[0092] Table 2 Time domain RMS values for vehicle speed 20 m / s and Class B road surface

[0093] Evaluation indicators Passive suspension Sliding mode control ESO-FTSMC Improvement rate Vehicle acceleration 0.5790 0.4799 0.4231 26.93％ Suspension dynamic deflection 0.0188 0.0157 0.0125 33.51％ Tire dynamic load 1117.6593 1009.2014 791.6044 26.17％

[0094] Table 3 Time domain RMS values for vehicle speed 20 m / s and Class C road surface

[0095] Evaluation indicators Passive suspension Sliding mode control ESO-FTSMC Improvement rate Vehicle acceleration 1.1966 1.0338 0.9299 22.29％ Suspension dynamic deflection 0.0391 0.0340 0.0278 28.90％ Tire dynamic load 2047.0010 1926.9454 1569.9929 23.30％

[0096] like Figure 4 and Figure 7 As shown in the figure, under the excitation of Class B and Class C road surfaces, the passive suspension has a large range of vertical body acceleration variations, indicating that its ability to suppress body vibration is limited and it is difficult to effectively cope with the impact caused by road excitation, resulting in more obvious body vibration.

[0097] Traditional sliding mode control: Compared with passive suspension, it can reduce the amplitude of vehicle acceleration to a certain extent, has a better suppressive effect on vehicle vibration, and improves the vehicle vibration situation, but there are still certain fluctuations.

[0098] ESO-FTSMC (present invention): The vertical vehicle body acceleration waveform under this method is the most stable and the amplitude is relatively small, indicating that it is most effective in suppressing vehicle body vibration, can more effectively respond to road excitation, and provide better ride smoothness for the vehicle.

[0099] like Figure 5 and Figure 8 As shown in the figure, under the excitation of Class B and Class C road surfaces, the passive suspension: the suspension dynamic deflection varies widely and fluctuates frequently, indicating that it is difficult to effectively control the deformation of the suspension when responding to road unevenness, resulting in a more intense dynamic response of the suspension during vehicle driving.

[0100] Traditional sliding mode control: Compared with passive suspension, it can reduce the amplitude of suspension dynamic deflection, reduce the amount of suspension deformation, improve the dynamic performance of the suspension to a certain extent, and enhance the buffering effect of road excitation.

[0101] ESO-FTSMC (present invention): The suspension dynamic deflection waveform amplitude under this method is the smallest and the smoothest, indicating that it has the best control effect on the suspension dynamic deflection, can more effectively adapt to road excitation, reduce the dynamic deformation of the suspension, and improve the stability and comfort of vehicle driving.

[0102] like Figure 6 and Figure 9 As shown in the figure, under the excitation of Class B and Class C road surfaces, the passive suspension: the wheel dynamic load fluctuates greatly and frequently, indicating that the load between the wheel and the road surface changes dramatically during driving, which may affect the vehicle's handling stability and the service life of the tire.

[0103] Traditional sliding mode control: Compared with passive suspension, it can effectively reduce the fluctuation amplitude and frequency of wheel load, making the wheel load changes more stable, which helps to improve the stability of the vehicle during driving.

[0104] ESO-FTSMC (present invention): This method produces the most stable waveform of the wheel load and the smallest amplitude, indicating that it can better control the changes in the wheel load, reduce the impact between the wheel and the road surface, help improve the vehicle's handling performance and tire durability, and enhance driving safety.

[0105] The specific performance impact of the extended state observer (ESO) on the sliding mode controller (SMC) is reflected in: reducing the sliding mode switching gain and suppressing chattering; enhancing the robustness to mismatched disturbances; reducing the dependence on accurate models; improving the dynamic response speed; improving the performance in state-constrained scenarios; and ensuring parameter adaptation and stability.

[0106] In this invention, the extended state observer (ESO) senses and quantifies disturbances in real time, providing feedforward compensation. Sliding mode control provides robust feedback through the design of sliding surface. Through collaborative design of disturbance estimation, compensation, and robustness enhancement, these two systems jointly address nonlinearities, uncertainties, and external disturbances in complex systems, reducing chattering, improving accuracy, and enhancing adaptability to complex disturbances. The extended state observer (ESO) enables real-time signal observation and constructs a global fast terminal sliding mode. Its control rate is continuous and does not include switching terms, effectively eliminating chattering, improving robustness to system uncertainties and disturbances, and avoiding chattering. The extended observer can reconstruct and estimate the state of unknown nonlinear systems, requiring minimal known system information.

[0107] In this paper, an extended state observer is used to achieve real-time signal observation and construct a global fast terminal sliding mode. Its control rate is continuous and does not include switching terms, effectively eliminating chattering and providing enhanced robustness to system uncertainties and disturbances. A 1 / 4 vehicle semi-active suspension model was run in MATLAB, and time-domain performance simulations of the suspension under random road excitation were performed to verify the effectiveness of the constructed dynamic model and control strategy.

[0108] The above description only describes specific embodiments of the present invention. Various examples do not limit the essential content of the present invention. After reading the description, ordinary technicians in the relevant technical field can modify or deform the specific embodiments described above without departing from the essence and scope of the invention.

Claims

1. A control system for a hydraulic-electric energy-feeding suspension system based on expansion observation and sliding mode control, characterized by: The extended state observer estimates the disturbance and transmits it to the sliding mode controller. The controller output u of the sliding mode controller is input to the hydraulic-electric energy-feeding suspension system. The hydraulic-electric energy-feeding suspension system feeds back the state vector to the extended state observer and the sliding mode controller. The state space expression of the hydraulic-electric energy-feeding suspension system is: State vector Among them, m s is the sprung mass, z s is the sprung mass displacement, z us is the unsprung mass displacement, k is the spring stiffness, |d z |≤d0 is the disturbance estimated by the extended state observer; d0 is the disturbance of the hydraulic-electric energy-feedback suspension system. The extended state observer is designed as follows: Where: and is the observer state, the observation error ε>0, α1, α2 and α3 are positive real numbers; y is the output of the hydraulic-electric energy-feeding suspension system. In the sliding mode controller, the tracking error e1(t) is: e1(t)=x1-x d (t); Where: x d (t) is the preset trajectory signal; The designed sliding surface s is: In the formula: t1>0, t2>0 are constants, and q<p is a positive odd number.

2. The control system of the hydraulic-electric energy-feeding suspension system based on expansion observation and sliding mode control according to claim 1 is characterized in that: In the extended state observer, the observation error state equation is: η is the observation error, represents the observation error gain, represents the rate of change of disturbance.

3. The control system of the hydraulic-electric energy-feeding suspension system based on expansion observation and sliding mode control according to claim 1 is characterized in that: In the extended state observer, the Lyapunov function V of the extended state observer is defined as: V=εη T Pη; where: P is a symmetric positive definite matrix.

4. The control system of the hydraulic-electric energy-feeding suspension system based on expansion observation and sliding mode control according to claim 1 is characterized in that: In the sliding mode controller, the Lyapunov function V1 of the sliding mode observer is defined as:

5. The control system of the hydraulic-electric energy-feeding suspension system based on expansion observation and sliding mode control according to claim 1 is characterized in that: In the sliding mode controller, the controller output u is: and λ are constants greater than zero.

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