Rocket sub-stage wing parachute recovery attitude fault-tolerant control method under actuator failure

Abstract

The application provides a rocket sub-stage wing parachute recovery attitude fault-tolerant control method, so as to compensate for the interference torque caused by the actuator failure and unknown disturbance, realize attitude fault-tolerant control, construct a combination body actuator failure model based on a wing parachute-sub-stage combination body kinematics model; a sliding mode disturbance observer is designed to estimate the lumped interference torque caused by the actuator failure and unknown disturbance; a finite time preset performance backstepping sliding mode attitude fault-tolerant controller is designed based on preset performance theory and backstepping sliding mode control. The application estimates the lumped interference torque by using the sliding mode disturbance observer, combines preset performance control and backstepping sliding mode control, designs a finite time attitude fault-tolerant controller, and realizes accurate control of the attitude of the wing parachute-sub-stage combination body under the influence of the actuator failure and uncertain disturbance.

Description

Technical Field

[0001] This invention relates to the field of aircraft fault-tolerant control technology, specifically to a fault-tolerant control method for rocket stage parachute recovery attitude, which is applied to aircraft attitude fault-tolerant control. Background Technology

[0002] The parachute and rocket stage are connected by a flexible connection, and there is a large relative motion between them. During the recovery process, they are in an extremely complex multi-physics coupling environment of thermal, mechanical, electrical and magnetic fields, and are also affected by various uncertain disturbances. This places extremely high demands on the reliability and fault-tolerant control capabilities of the parachute actuator.

[0003] To ensure precise attitude control of the parachute-stage assembly during recovery and achieve safe and accurate recovery, the finite-time preset performance attitude fault-tolerant control method provides an effective solution to this problem.

[0004] Fault-tolerant control has been widely applied in rockets, drones, and other aircraft, but research on fault-tolerant control for rocket stage parachute recovery is scarce. Furthermore, the limited space at the tail of a rocket stage makes it difficult to achieve physical-level fault-tolerant control by installing multiple redundant parachute actuators. Therefore, conducting research on fault-tolerant attitude control for rocket stage parachute recovery under actuator failure conditions has significant theoretical and practical value. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a fault-tolerant attitude control method for rocket stage parachute recovery under actuator failure, in order to compensate for the disturbance torque caused by actuator failure and unknown disturbances, and achieve attitude fault-tolerant control.

[0006] This invention addresses actuator failures and unknown disturbances during the recovery of a rocket's first-stage parachute by designing an attitude-tolerant control method combining a finite-time preset performance backstepping sliding mode controller and a sliding mode disturbance observer. The method includes: Step 1, constructing an actuator failure model based on the kinematic model of the parachute-first-stage assembly; Step 2, designing a sliding mode disturbance observer to estimate the lumped disturbance torque caused by actuator failures and unknown disturbances; Step 3, designing a finite-time preset performance backstepping sliding mode attitude-tolerant controller based on preset performance theory and backstepping sliding mode control. The fault-tolerant control scheme disclosed in this invention can achieve fast and accurate attitude-tolerant control of the parachute-first-stage assembly under the influence of actuator failures and unknown disturbances.

[0007] The technical solution adopted by this invention to solve its technical problem includes the following steps:

[0008] Step 1: Construct an actuator failure model for the parachute-sub-stage assembly; the actuator failure model includes the disturbance torque term to be estimated;

[0009] Step 2: Design a sliding mode disturbance observer to estimate the lumped disturbance torque caused by actuator failure and unknown disturbances;

[0010] Step 3: Based on the finite-time preset performance control theory;

[0011] Based on preset performance control and backstepping sliding mode control, a preset performance backstepping sliding mode controller is designed. Combined with the observer's estimation, an attitude fault-tolerant controller is designed. The specific steps are as follows:

[0012] First, the state error of the combined system is constrained by subtracting the desired state from the actual state through a performance function. Second, the constrained space is mapped to the unconstrained space through a transformation function to achieve error transformation. Finally, based on the transformation error, a non-singular terminal sliding surface is used, and the design method of backstepping sliding control is followed to combine preset performance control with backstepping sliding control to design a finite-time preset performance backstepping sliding attitude fault-tolerant controller that can quickly and accurately track the desired signal, thus constraining the system error within the preset performance boundary.

[0013] The constructed finite-time preset performance backstepping sliding mode attitude fault-tolerant controller can quickly estimate the disturbance torque under the influence of actuator failure and unknown interference, compensate the controller, and achieve accurate tracking of the desired attitude angle signal, thus exhibiting good fault-tolerant performance.

[0014] The actuator failure model adopts a second-order model of actuator failure in a parachute-sub-stage assembly, with the specific expression as follows:

[0015]

[0016] The model of the parachute-sub-stage combination is as follows:

[0017]

[0018] In the formula, x1=[φ p θ p ψ p ] T The parachute's attitude angle is represented by x2 = [p p q p r p ] T I represents the angular velocity of the parachute attitude. p Let τ be the moment of inertia of the parachute, and τ be the control torque. d Uncertain disturbances include external environmental disturbances, mutual disturbances between the parachute and rocket stages, and model uncertainties; D represents the lumped disturbance torque caused by actuator failures and unknown disturbances; η is the actuator partial failure coefficient, indicating that the actuator produces a multiplicative failure; T′ eIt is the additional control torque exerted by the actuator, indicating that the actuator has an additive fault.

[0019] The sliding mode interference observer is:

[0020]

[0021] in The disturbance torque is the observed value, m>0, n>0, and s is the non-singular fast terminal sliding surface; the sliding mode disturbance observer converges in a finite time, and the finite-time convergence is based on the non-singular fast terminal sliding surface. The sliding surface converges to a steady state in a finite time, the convergence time being... Another sliding surface s1 was chosen in both the sliding mode disturbance observer and controller design, where m,n,α,β,p,q,α1 andβ1 are control coefficients, both of which are constants, and x(0) represents the initial time value.

[0022] In step three, the state error of the assembly is constrained through a performance function. When the system tracking error e(t) is limited within the boundary, the transient and steady-state characteristics of the system meet the preset indicators, namely:

[0023]

[0024] In the formula, -δ i ρ(t) and ρ(t) are the lower and upper bounds of the performance envelope, respectively, where δ i It is a constant that satisfies δ i ∈(0,1], by adjusting δ i To constrain the system overshoot.

[0025] The performance function is ρ(t): R + ∪{0}→R + ρ(t) is a smooth function that is always positive and monotonically decreasing; ρ0 and ρ ∞ All are greater than zero.

[0026] The performance function is:

[0027]

[0028] In the formula t f >0 represents the custom convergence time, and v is a constant parameter. Compared to conventional performance functions, the performance function selected in this invention is a finite-time performance function. The custom convergence time allows the error to converge to the final value within a finite time, achieving the goal of finite-time convergence. The error converges to the final value before this convergence time, and the convergence time is less than or equal to this convergence time, achieving the goal of finite-time convergence.

[0029] The specific steps for the conversion function to map the constrained space homeomorphically to the unconstrained space to achieve error conversion are as follows:

[0030] First, introduce intermediate variables:

[0031]

[0032] Select a smooth and monotonically increasing error conversion function T(·) to convert e′ into error ε, and the error ε is:

[0033] ε = T(e′)

[0034] At this time, the conversion error ε is bounded, and the tracking error of the system is limited within the preset boundary. The selected error conversion function is:

[0035]

[0036] The backstepping sliding mode attitude fault-tolerant controller is:

[0037]

[0038] sat(·) is the saturation function, x2 × is the cross product. In the formula, the control coefficients c, λ, μ, α1, β1 > 0, p and q are positive odd numbers and 1 < p / q < 2, e is the attitude angle tracking error, the conversion error of e is ε, κ, γ are auxiliary variables, S is the nonsingular fast terminal sliding mode surface, is the estimated value of the lumped disturbance torque caused by actuator faults and unknown disturbances by the sliding mode disturbance observer.

[0039] The beneficial effect of the present invention is based on the established wing parachute - combined body actuator fault model. The lumped disturbance torque is estimated by using a sliding mode disturbance observer, and the preset performance control and backstepping sliding mode control are combined to design a finite-time attitude fault-tolerant controller, realizing the precise control of the attitude of the wing parachute - sub-stage combined body under the influence of actuator faults and uncertain disturbances. Description of the Drawings

[0040] Figure 1 The flowchart of the rocket sub-stage wing parachute recovery attitude fault-tolerant control method under actuator faults of the present invention;

[0041] Figure 2 The attitude angle control response and tracking error curves for a sine signal under actuator faults and unknown disturbances in the embodiment of the present invention; Figure 2 In figure (a) is the tracking result of the desired signal; figure (b) is the tracking error of the desired signal; figure (c) is the observed output. Detailed Embodiment

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] This invention provides a fault-tolerant attitude control method for rocket stage parachute recovery under actuator failure. Based on preset performance theory and backstepping sliding mode control, combined with a sliding mode disturbance observer, attitude fault-tolerant control is achieved. First, the attitude fault-tolerant control method provided by this invention establishes a parachute-stage actuator failure model based on the parachute-stage motion model. Then, a sliding mode disturbance observer is designed. Finally, based on preset performance theory and backstepping sliding mode control, combined with the designed sliding mode disturbance observer, a finite-time preset performance backstepping sliding mode attitude fault-tolerant controller is designed, thereby achieving precise attitude control of the assembly under the influence of actuator failure and unknown disturbances.

[0044] The fault-tolerant control method for rocket stage parachute recovery attitude under actuator failure provided in this embodiment of the invention includes the following steps:

[0045] Step 1: Based on the motion model of the parachute-sub-stage, establish the parachute-sub-stage actuator fault model;

[0046] To facilitate controller design, a fault model for the wing-parallel stage actuator is constructed based on the motion model of the wing-parallel stage, as shown below:

[0047]

[0048] In the formula, x1=[φ p θ p ψ p ] T The parachute's attitude angle is represented by x2 = [p p q p r p ] T I represents the angular velocity of the parachute attitude. p Let τ be the moment of inertia of the parachute, and τ be the control torque. d Uncertain disturbances include external environmental disturbances, mutual disturbances between the parachute and rocket stages, and model uncertainties. D represents the lumped disturbance torque caused by actuator failures and unknown disturbances, η is the actuator partial failure coefficient, indicating multiplicative failures in the actuator, and T′... e It is the additional control torque exerted by the actuator, indicating that the actuator has an additive fault.

[0049] Step 2: Design the sliding mode disturbance observer. Before designing the attitude fault-tolerant controller, the observer must first estimate the lumped disturbance torque D caused by actuator failures and unknown disturbances to compensate for the impact of the disturbance torque on attitude control. The sliding mode disturbance observer can derive the estimated values ​​of the state variables based on the system's input and output variables, thereby estimating the disturbance torque. The expression for the disturbance observer is as follows:

[0050]

[0051] Where s1 is the exponential reaching law, as follows:

[0052]

[0053] Where is the observed value of the disturbance torque, m>0, n>0, and s is the non-singular fast terminal sliding mode surface.

[0054] Step 3: Based on the preset performance theory and backstepping sliding mode control, combined with the sliding mode disturbance observer designed in Step 2, design a finite-time preset performance backstepping sliding mode attitude fault-tolerant controller to achieve precise control of the combined body attitude under the influence of actuator faults and unknown disturbances;

[0055] First, define the attitude angle tracking error e=(e1, e2, e3) T , and the expression is

[0056] e = x1 - x 1d

[0057] Where x 1d represents the desired attitude angle, and e1, e2, and e3 are the attitude angle tracking errors in the roll, pitch, and yaw directions, respectively;

[0058] To achieve the preset performance control of the combined body attitude, select the preset performance function as:

[0059]

[0060] Where 0 < ρ0 < ρ ∞ , t f >0 is the self-defined convergence time, and 0 < v < 1 is a constant parameter.

[0061] According to the preset performance control theory, define the transformation error of e as ε=(ε1, ε2, ε3) T . Design the attitude controller according to the transformation error. When the system satisfies the asymptotic stability condition, the system error e can be maintained within the preset performance boundary.

[0062] When designing the preset performance attitude controller, the derivative of the transformation error is required, and the expression is

[0063]

[0064] For the convenience of derivation, define auxiliary quantities κ and γ, where:

[0065]

[0066] Definition

[0067] Define the non-singular fast terminal sliding mode surface as follows:

[0068] S = α1ε + ε′ + β1sig p / q (ε)

[0069] where α1 and β1 are greater than zero, p and q are positive odd numbers and 1 < p / q < 2;

[0070] Select the reaching law, and the expression is as follows:

[0071]

[0072] where λ and μ are greater than zero;

[0073] The expression of the preset performance attitude controller is as follows:

[0074]

[0075] where c, λ, μ, α1, β1 > 0, p and q are positive odd numbers and 1 < p / q < 2, e is the attitude angle tracking error, the conversion error of e is ε, κ and γ are auxiliary variables, S is the non-singular fast terminal sliding mode surface, is the estimated value of the lumped disturbance torque caused by the actuator fault and unknown disturbance by the sliding mode disturbance observer.

[0076] The embodiment of the present invention provides a method for attitude fault-tolerant control of the rocket sub-stage parafoil recovery under actuator faults. This method is based on the preset performance theory and backstepping sliding mode control, combined with a sliding mode disturbance observer to achieve attitude fault-tolerant control; First, the method for attitude fault-tolerant control of the rocket sub-stage parafoil recovery provided by the embodiment of the present invention establishes an actuator fault model of the parafoil-sub-stage based on the motion model of the parafoil-sub-stage; Then design a sliding mode disturbance observer to estimate the lumped disturbance torque caused by actuator faults and unknown disturbances; Finally, based on the preset performance theory and backstepping sliding mode control, combined with the designed sliding mode disturbance observer, a finite-time preset performance backstepping sliding mode attitude fault-tolerant controller is designed, so as to achieve the precise attitude control of the combined body under the influence of actuator faults and unknown disturbances. By using the attitude fault-tolerant control method provided by the embodiment of the present invention, precise attitude control can be achieved, the influence of actuator faults and unknown disturbances can be suppressed, and the system error can be limited within the preset boundary. Compared with the traditional fault-tolerant control method, the fault-tolerant control scheme proposed by the embodiment of the present invention can limit the system error within the preset boundary in a finite time, achieve fast and accurate tracking of the desired attitude angle, and has good fault-tolerant performance.

[0077] Furthermore, to demonstrate the effectiveness of the fault-tolerant control method for rocket stage parachute recovery proposed in this embodiment of the invention, simulation experiments were conducted on the fault-tolerant control method provided in this embodiment of the invention. The tracking results of the controller on the desired signal under the influence of actuator failure and unknown disturbances were verified.

[0078] In the simulation, white noise is used to simulate unknown interference, and the following actuator fault signal is set:

[0079]

[0080] An additive fault occurs at 0.3 seconds, and a multiplicative fault occurs at 1 second.

[0081] The desired attitude angle is set to a sine signal. Figure 2 The effectiveness of the finite-time preset performance backstepping sliding mode attitude fault-tolerant controller provided in this embodiment of the invention in tracking the desired signal during simulation experiments under the influence of actuator failure and unknown disturbances is presented. Figure 2 (a) and Figure 2 As shown in (b), under the influence of actuator failure and unknown disturbances, regardless of whether a sliding mode observer is introduced, the designed finite-time preset performance backstepping sliding mode controller can quickly track the desired signal. However, under the influence of actuator failure and unknown disturbances, the tracking error of the controller exceeds the preset boundary after 1.5 seconds without the observer. Conversely, after introducing the observer, the controller can track the desired signal better, effectively compensating for the influence of actuator failure and unknown disturbances. Figure 2 As can be seen in (c), the sliding mode disturbance observer can effectively observe the lumped disturbance torque caused by actuator faults and unknown disturbances. Therefore, after disturbance compensation by the disturbance observer, the tracking performance of the controller can be significantly improved. The fault-tolerant control method that combines the sliding mode disturbance observer with the finite-time preset performance backstepping sliding mode controller has good fault-tolerant performance.

[0082] Simulation results show that the attitude fault-tolerant control scheme proposed in this invention can achieve attitude fault-tolerant control of the rocket-stage assembly under the influence of actuator failure and unknown disturbances, and has good fault-tolerant performance.

Claims

1. A fault-tolerant control method for the attitude recovery of a rocket stage parachute under actuator failure, characterized in that... Includes the following steps: Step 1: Construct an actuator failure model for the parachute-sub-stage assembly; the actuator failure model includes the disturbance torque term to be estimated; Step 2: Design a sliding mode disturbance observer to estimate the lumped disturbance torque caused by actuator failure and unknown disturbances; Step 3: Based on the finite-time preset performance control theory; Based on preset performance control and backstepping sliding mode control, a preset performance backstepping sliding mode controller is designed, and an attitude fault-tolerant controller is designed in conjunction with the observer's estimation.

2. The rocket stage parachute recovery attitude fault-tolerant control method under actuator failure as described in claim 1, characterized in that: The specific steps for designing an attitude fault-tolerant controller are as follows: First, the state error of the combined system is constrained by subtracting the desired state from the actual state through a performance function. Second, the constrained space is mapped to the unconstrained space through a transformation function to achieve error transformation. Finally, based on the transformation error, a non-singular terminal sliding surface is used, and the design method of backstepping sliding control is followed to combine preset performance control with backstepping sliding control to design a finite-time preset performance backstepping sliding attitude fault-tolerant controller that can quickly and accurately track the desired signal, thus constraining the system error within the preset performance boundary. The constructed finite-time preset performance backstepping sliding mode attitude fault-tolerant controller can quickly estimate the disturbance torque under the influence of actuator failure and unknown interference, compensate the controller, and achieve accurate tracking of the desired attitude angle signal, with good fault tolerance performance. The actuator failure model adopts a second-order model of actuator failure in a parachute-sub-stage assembly, with the specific expression as follows: The model of the parachute-sub-stage combination is as follows: In the formula, x1=[φ p θ p ψ p ] T The parachute's attitude angle is represented by x2 = [p p q p r p ] T I represents the angular velocity of the parachute attitude. p Let τ be the moment of inertia of the parachute, and τ be the control torque. d Uncertain disturbances include external environmental disturbances, mutual disturbances between the parachute and rocket stages, and model uncertainties; D represents the lumped disturbance torque caused by actuator failures and unknown disturbances, η is the actuator partial failure coefficient, indicating that the actuator produces a multiplicative failure, and T... e ′ represents the additional control torque exerted by the actuator, indicating an additive fault in the actuator.

3. The rocket stage parachute recovery attitude fault-tolerant control method under actuator failure as described in claim 1, characterized in that: In step three, the state error of the assembly is constrained through a performance function. When the system tracking error e(t) is limited within the boundary, the transient and steady-state characteristics of the system meet the preset indicators, namely: In the formula, -δ i ρ(t) and ρ(t) are the lower and upper bounds of the performance envelope, respectively, where δ i It is a constant that satisfies δ i ∈(0,1], by adjusting δ i To constrain the system overshoot.

4. The rocket stage parachute recovery attitude fault-tolerant control method under actuator failure as described in claim 3, characterized in that: The performance function is ρ(t): R + ∪{0}→R + ρ(t) is a smooth function that is always positive and monotonically decreasing; ρ0 and ρ ∞ All are greater than zero.

5. The rocket stage parachute recovery attitude fault-tolerant control method under actuator failure as described in claim 4, characterized in that: The performance function is: In the formula t f >0 represents the custom convergence time, and v is a constant parameter. Compared to conventional performance functions, the performance function selected in this invention is a finite-time performance function. The custom convergence time allows the error to converge to the final value within a finite time, achieving the goal of finite-time convergence. The error converges to the final value before this convergence time, and the convergence time is less than or equal to this convergence time, achieving the goal of finite-time convergence.

6. The rocket stage parachute recovery attitude fault-tolerant control method under actuator failure as described in claim 2, characterized in that: The specific steps of the transformation function to map the constrained space homeomorphism to the unconstrained space to achieve error transformation are as follows: First, we introduce intermediate variables: Choose a smooth, monotonically increasing error transformation function T(·) to convert e′ into error ε, where error ε is: ε=T(e′) At this point, the conversion error ε is bounded, and the system's tracking error is limited to a preset boundary. The error conversion function is selected as follows:

7. The rocket stage parachute recovery attitude fault-tolerant control method under actuator failure as described in claim 1, characterized in that: The backstepping sliding mode attitude fault-tolerant controller is: sat(·) is a saturation function, x2 × is the cross product. In the formula, the control coefficients c, λ, μ, α1, β1 > 0, p and q are positive odd numbers and 1 < p / q < 2, e is the attitude angle tracking error, the conversion error of e is ε, κ, γ are auxiliary variables, S is a nonsingular fast terminal sliding mode surface, is the estimated value of the lumped disturbance torque caused by the actuator fault and unknown disturbance by the sliding mode disturbance observer.

8. The rocket stage parachute recovery attitude fault-tolerant control method under actuator failure according to claim 1, characterized in that: The sliding mode interference observer is: in The disturbance torque is the observed value, m>0, n>0, and s is the non-singular fast terminal sliding surface; the sliding mode disturbance observer converges in a finite time, and the finite-time convergence is based on the non-singular fast terminal sliding surface. The sliding surface converges to a steady state in a finite time, the convergence time being... Another sliding surface s1 was chosen in both the sliding mode disturbance observer and controller design, where m,n,α,β,p,q,α1 andβ1 are control coefficients, both of which are constants, and x(0) represents the initial time value.

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