Active motion compensation helicopter platform flexible preset performance control method

Abstract

The invention discloses a flexible preset performance control method for an active motion compensation helicopter platform. The method comprises the following steps: designing a flexible preset performance function; constructing an improved extended state observer; designing an active motion compensation helicopter platform kinematics control law; and designing a flexible preset performance control law of the active motion compensation helicopter platform. According to the method, the flexible preset performance function is designed, so that the pose error of the upper support surface of the helicopter platform under the inertial coordinate system meets the preset performance constraint condition, and the performance function can be directionally relaxed when input saturation occurs, thereby avoiding control singularity. By designing the continuous auxiliary dynamic system, the helicopter platform has the full-time input saturation compensation capability. According to the method, an improved extended state observer is designed, unknown total disturbance formed by equivalent disturbance caused by model uncertainty and ship motion can be estimated in real time, and the estimation capacity of rapid change disturbance is enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of equipment control technology of marine and ocean engineering, and in particular to a flexible preset performance control method for an active motion compensation helicopter platform. BACKGROUND

[0002] When a ship is operating at sea, it is continuously disturbed by complex marine environments such as wind, waves, and currents, and will produce six degrees of freedom motion, including roll, pitch, yaw, sway, surge, and heave. These motions seriously affect the stability of key equipment on the ship, especially posing a serious safety threat to helicopter landing operations. As a high-performance shipborne stabilization platform, the active motion compensation helicopter platform generates active control forces through its actuators to compensate for ship motion, keeping the deck plane dynamically stable in inertial space, thereby providing a safe landing environment for helicopters.

[0003] Chinese patent CN111619816A proposes a shipborne offshore helicopter landing stabilization platform, which adopts a structure combining multiple hydraulic cylinders and ball hinge sleeves to enable the moving platform to realize six-direction motion in space, effectively compensating for the multi-dimensional motion of the ship. This platform has certain innovation in structural design and can ensure stability without modifying the existing platform main structure. However, this scheme mainly focuses on mechanical structure improvement and does not involve in-depth design of control algorithms, lacking targeted solutions for dynamic control problems under complex sea conditions.

[0004] Chinese patent CN109739248A discloses a shipborne three-degree-of-freedom parallel stabilization platform control method based on active disturbance rejection control (ADRC). This method uses an extended state observer to estimate system dynamic uncertainty and external disturbances, achieving stable control independent of accurate mathematical models, with the advantages of simple design and easy engineering implementation. However, the disturbance observer used in this method has certain limitations in estimating rapidly changing disturbances, and lacks tracking ability for high-frequency disturbances, which may affect the stabilization performance of the platform under extreme sea conditions.

[0005] Chinese patent CN105676854A relates to a three-degree-of-freedom helicopter anti-saturation attitude tracking control method, which compensates for control input saturation by designing an auxiliary dynamic system. However, this auxiliary dynamic system has discontinuity and only plays a compensating role when the control input is saturated for the first time, failing to achieve anti-saturation compensation in the full time domain, which limits its control effect under continuous saturation conditions.

[0006] A spacecraft attitude variable performance control method considering input saturation is proposed in Chinese patent CN118457945B, which uses a preset performance function to bound the attitude error. Although this method takes into account the input saturation problem, its preset performance function cannot flexibly adjust the boundary when saturation occurs, which may lead to singular phenomena in the control system, affecting the stability and reliability of the system.

[0007] Chinese patent CN113625546B introduces a shipborne stable platform stabilization control anti-saturation method, which compensates for the influence of control input saturation through an auxiliary dynamic system. However, this method does not impose explicit constraints on the control performance of the system, nor does it fully consider the impact of external disturbances on platform stability, so the control effect is limited when facing compound disturbances and performance constraint requirements. SUMMARY

[0008] To solve the problems of control singularity, discontinuous saturation compensation, and not considering performance constraints and disturbances in the prior art, the present invention proposes a flexible preset performance control method for active motion compensation helicopter platform, aiming to stabilize the helicopter platform support surface at the desired pose, while actively compensating for ship rolling motion, ensuring that the pose error always meets the preset performance constraints, and having full-time input saturation compensation capability. In particular, when input saturation occurs, the designed performance function can be flexibly relaxed, effectively avoiding control singularity.

[0009] To achieve the above-mentioned purpose, the technical solution of the present invention is as follows: a flexible preset performance control method for active motion compensation helicopter platform, the dynamics equation of the active motion compensation helicopter platform is shown in formula (1):

[0010]

[0011] In the formula, q = [x, y, z, φ, θ, ψ] T is the pose vector of the support surface on the active motion compensation helicopter platform in the inertial coordinate system, composed of longitudinal displacement x, lateral displacement y, vertical displacement z, inclination angle φ, pitch angle θ, and yaw angle ψ, and are the first and second derivatives of q, respectively; M(q) ∈ R 6×6 is the inertia matrix, is the Coriolis-centrifugal matrix, G(q) ∈ R 6 is the gravity vector, τ = [τ1, τ2, τ3, τ4, τ5, τ6] TThe control input vector of the helicopter platform is composed of longitudinal control force τ1, lateral control force τ2, vertical control force τ3, tilting control moment τ4, pitching control moment τ5 and yawing control moment τ6; d(t) represents an equivalent disturbance force and moment vector caused by ship motion, active motion compensation helicopter platform control input saturation is described as:

[0012]

[0013] In the formula, τ i,max > 0 and τ i,min < 0 are respectively the upper limit and the lower limit of the saturation of the active motion compensation helicopter platform control input, τ c,i represents the command control input of the active motion compensation helicopter platform. Denote τ c = [τ c,1 , τ c,2 , …, τ c,6 ] T represents the command control input vector, and the deviation between the actual control input vector and the command control input vector is denoted as Δτ = τ c = [Δτ1, Δτ2, …, Δτ6] T .

[0014] The inertia matrix M(q), the Coriolis-centrifugal matrix and the gravity vector G are uncertain but bounded. Denote M(q) = M o (q) + ΔM(q), and G = G o + ΔG, where (·) o is the nominal part and Δ(·) is the uncertain part. Then equation (1) is rewritten as:

[0015]

[0016] In the formula,

[0017] The flexible pre-performance control method of the active motion compensation helicopter platform comprises the following steps:

[0018] A. Design a flexible pre-performance function

[0019] Let q d = [x d , y d , z d , φ d , θ d , ψ d ] T be the constant expected pose vector of the support surface on the active motion compensation helicopter platform in the inertial coordinate system, and x d, desired lateral displacement y d , desired vertical displacement z d , desired tilt angle φ d , desired pitch angle θ d , and desired yaw angle ψ d comprise. Define the pose error vector of the support surface on the helicopter platform in the inertial coordinate system as e = q - q d = [e1, e2,..., e6] T . In order to achieve flexible pre-set performance control, the error e i must satisfy the following performance constraint conditions:

[0020] ρ l,i < e i < ρ u,i , i = 1, 2,..., 6 (4)

[0021] In the formula, ρ l,i (t) is the lower limit flexible pre-set performance function, ρ u,i (t) is the upper limit flexible pre-set performance function, and is designed as follows:

[0022]

[0023] In the formula, exp(·) represents the natural exponential function, -ρ l,0,i and ρ u,0,i are the initial values of ρ l,i (t) and ρ u,i (t) respectively, -ρ l,∞,i and ρ u,∞,i are the steady-state values of ρ l,i (t) and ρ u,i (t) respectively, μ l,i > 0 and μ u,i > 0 respectively represent the convergence rates of ρ l,i (t) and ρ u,i (t); is the pre-set performance function directional relaxation signal, which is generated by the following second-order filter:

[0024]

[0025] In the formula, ι i = α i , β i , ω i and are positive design constants, α i and β i are direction perception coefficients, and their definitions are as follows:

[0026]

[0027] where sign( ) denotes the sign function.

[0028] In the forward saturation regime, i.e., when τ c,i -τ i > 0, the direction-aware coefficient α i = 0 and β i = 1, then according to equation (6), we have According to equation (5), we have the lower bound soft-guarantee performance function ρ l,i (t) is relaxed, and the upper bound soft-guarantee performance function ρ u,i (t) is not relaxed; in the backward saturation regime, i.e., when τ c,i -τ i < 0, the direction-aware coefficient α i = 1 and β i = 0, then according to equation (6), we have According to equation (5), we have the upper bound soft-guarantee performance function ρ u,i (t) is relaxed, and the lower bound soft-guarantee performance function ρ l,i (t) is not relaxed.

[0029] B. Constructing the improved extended state observer

[0030] First, define the state vector z1= q, and z3= M o -1 (q)τ d . According to the active motion compensation helicopter platform dynamics equation (3), its extended first-order state space expression is as follows:

[0031]

[0032] where B = M o -1 (q) is a gain matrix, is a function vector, f = z3, represents the unknown total disturbance vector composed of the matrix and vector uncertainties in the helicopter platform dynamics equation (3) and the equivalent disturbance caused by ship motion, denotes the first derivative of f.

[0033] The improved extended state observer is constructed as follows:

[0034]

[0035] where and are the estimates of z2 and z3, respectively, υ is an auxiliary vector, K o,1 , K o,2 , and K o,3 are all positive definite design matrices.

[0036] C. Designing active motion compensation helicopter platform kinematic control law

[0037] C1. Designing error conversion function

[0038] Design the error conversion function f as follows i (e i ,ρ l,i (t),ρ u,i (t)):

[0039]

[0040] where s 1,i denotes the conversion variable, and ln(·) denotes the sign function. The error conversion function f i (e i ,ρ l,i (t),ρ u,i (t)) converts the pose error e i into the boundedness problem of the conversion variable s 1,i satisfying the performance constraint condition (4). To facilitate subsequent control design, take the time derivative of s 1,i :

[0041]

[0042]

[0043] where

[0044]

[0045] C2. Designing kinematic control law

[0046] Define the vector s1 = [s 1,1 ,s 1,2 ,…,s 1,6 ] T , take the time derivative of it, and according to equation (17) and e = q - q d , we have

[0047]

[0048] where P = diag(P1, P2, …, P6) and Q = [Q1, Q2, …, Q6] T .

[0049] Regarding s as the virtual control input of equation (17), the kinematic control law is designed as follows:

[0050] χ = -K1P-1 s1+Q (19)

[0051] wherein, is a positive definite design matrix.

[0052] D, designing a flexible pre-performance control law of active motion compensation of a helicopter platform

[0053] D1, defining a new error vector s2=z2-x, taking the derivative of s2 with respect to time, and according to formula (11) and Δτ=τ-τ c , obtain:

[0054]

[0055] D2, designing the following continuous auxiliary dynamic system:

[0056]

[0057] wherein, is a saturation compensation signal; is a positive definite design matrix, κ a and κ b are arbitrary small design constants, 0<κ a <κ b .

[0058] D3, designing a pre-performance control law

[0059] The flexible pre-performance control law of active motion compensation of the helicopter platform includes a nonlinear feedback control law, a disturbance rejection control law and a saturation rejection control law, and is expressed as follows:

[0060]

[0061] wherein, and are positive definite design matrices.

[0062] The feedback control law is used to make the pose error of the support surface on the helicopter platform in the inertial coordinate system converge; the disturbance rejection control law is used to compensate for the total disturbance composed of helicopter platform model uncertainty and equivalent disturbance caused by ship motion; and the saturation rejection control law is used to compensate for the helicopter platform control input saturation.

[0063] Compared with the prior art, the present application has the following beneficial effects:

[0064] 1. By using the designed flexible pre-performance function, the pose error of the support surface on the helicopter platform in the inertial coordinate system satisfies the pre-designed performance constraint condition, and the performance function can be relaxed in a directional manner when input saturation occurs, so that control singularity is avoided.

[0065] 2. This invention enables the helicopter platform to have full-time input saturation compensation capability by designing a continuous auxiliary dynamic system.

[0066] 3. This invention designs an improved extended state observer, which can estimate the unknown total disturbance consisting of model uncertainty and equivalent disturbance caused by ship motion in real time. Furthermore, by introducing a differential term of the estimation error, it enhances the estimation capability for rapidly changing disturbances. Attached Figure Description

[0067] Figure 1 Schematic diagram of the principle of the flexible preset performance control method for active motion compensation helicopter platform. Detailed Implementation

[0068] The present invention will now be further described with reference to the accompanying drawings.

[0069] like Figure 1 As shown, the principle of this invention is as follows: the pose q of the support surface on the active motion compensation helicopter platform in the inertial coordinate system is fed back to the reference input end of the active motion compensation helicopter platform, and compared with the desired pose q of the support surface on the active motion compensation helicopter platform in the inertial coordinate system. d By comparison, the pose error e of the support surface on the helicopter platform in the inertial coordinate system is formed through active motion compensation; error e i Through the error transformation function f i (e i ,ρ l,i (t),ρ u,i (t)), output transformation variable s 1,i , where ρ l,i (t) and ρ u,i (t) represents the lower bound flexible preset performance function (5) and the upper bound flexible preset performance function (6), respectively. The directional relaxation can be adjusted according to the deviation Δτ between the actual control input vector and the command control input vector of the helicopter platform. The directional relaxation signal... Generated by a second-order filter (7); based on this, the kinematic control law χ(19) of the helicopter platform is designed, and compared with the first-order guide of the pose of the support surface on the helicopter platform in the inertial coordinate system. Comparison, generating error vector s2; constructing an improved extended state observer (13)-(15), the input of the extended state observer being the pose q of the support surface on the helicopter platform in the inertial coordinate system, the first-order derivative of the pose... Given the actual control input vector τ of the helicopter platform, the output of the extended state observer is an estimate of the total unknown disturbance, consisting of model uncertainties and equivalent disturbances caused by ship motion. A continuous auxiliary dynamic system (21) is designed, the input of the auxiliary dynamic system is an error vector s2 and a deviation Δτ between an actual control input vector and an instructed control input vector of the helicopter platform, and the output of the auxiliary dynamic system is a saturation compensation signal κ; a conversion variable s is formed according to the output of the observer 1,i , a kinematic control law χ, an error vector s2, a position q and a first-order derivative of the position of the supporting surface on the helicopter platform in an inertial coordinate system A nonlinear feedback control law is formed; an anti-disturbance control law is formed according to the output of the observer An anti-saturation control law is formed according to the output κ of the auxiliary dynamic system; and a final helicopter platform flexible preset performance control law τ is formed based on the above c The supporting surface of the helicopter platform can be stabilized at a desired horizontal position q d The ship rolling motion is actively compensated.

[0070] The present application is not limited to the embodiments, and any equivalent concept or change within the technical scope disclosed in the present application is included in the protection scope of the present application.

Claims

1. A method for active motion compensation helicopter platform flexible pre-assignment performance control, characterized by: The dynamic equation of the active motion compensation helicopter platform is shown as formula (1) : where q = [x, y, z, φ, θ, ψ] T is the position and orientation vector of the support surface of the active motion compensation helicopter platform in the inertial coordinate system, which consists of longitudinal displacement x, lateral displacement y, vertical displacement z, tilt angle φ, pitch angle θ and yaw angle ψ, and are the first and second derivatives of q, respectively; M(q) ∈ R 6×6 is the inertia matrix, is the Coriolis-Centrifugal matrix, G(q) ∈ R 6 is the gravity vector, τ = [τ1, τ2, τ3, τ4, τ5, τ6] T is the control input vector of the helicopter platform, which consists of longitudinal control force τ1, lateral control force τ2, vertical control force τ3, tilt control moment τ4, pitch control moment τ5 and yaw control moment τ6; d(t) represents the equivalent disturbance force and moment vector caused by ship motion, and the active motion compensation helicopter platform control input saturation is described as: where τ i,max > 0 and τ i,min < 0 are the upper and lower saturation bounds for the active motion compensation helicopter platform control input, respectively, and τ c,i denotes the active motion compensation helicopter platform's commanded control input; let τ c = [τ c,1 , τ c,2 ,..., τ c,6 ] T denote the commanded control input vector, and let the deviation between the actual control input vector and the commanded control input vector be denoted by Δτ = τ - τ c = [Δτ1, Δτ2,..., Δτ6] T ; The inertia matrix M(q), the Coriolis-centripetal matrix and the gravity vector G are uncertain but bounded; let M(q) = M o (q) + ΔM(q), and G = G o + ΔG, where (·) o is the nominal part and Δ(·) is the uncertainty part; then equation (1) is rewritten as: In the formulae, The flexible pre-specified performance control method of the active motion compensation helicopter platform comprises the following steps: A, design a flexible pre-specified performance function Let q d = [x d , y d , z d , φ d , θ d , ψ d ] T be the constant desired pose vector of the support surface on the helicopter platform in the inertial frame, consisting of the desired longitudinal displacement x d , the desired lateral displacement y d , the desired vertical displacement z d , the desired tilt angle φ d , the desired pitch angle θ d and the desired yaw angle ψ d ; define the pose error vector of the support surface on the helicopter platform in the inertial frame as e = q - q d = [e1, e2, …, e6] T ; in order to achieve flexible preset performance control, the error e i must satisfy the following performance constraint conditions: p l,i <e i <ρ u,i i = 1, 2,..., 6 (4) where p l,i (t) is a lower bound flexible pre-specified performance function, p u,i (t) is an upper bound flexible pre-specified performance function, designed as follows: where exp(•) denotes the natural exponential function, -p l,0,i and p u,0,i are initial values of p l,i (t) and p u,i (t), respectively, -p l,∞,i and p u,∞,i are steady-state values of p l,i (t) and p u,i (t), respectively, μ l,i > 0 and μ u,i > 0 denote convergence rates of p l,i (t) and p u,i (t), respectively; is a predetermined performance function directed relaxation signal, generated by the following second-order filter: wherein, i i = α i , β i , ω i and are positive design constants, α i and β i are direction perception coefficients defined as: In the formula, sign(·) represents a sign function; in the positive saturation regime, i.e. when τ c,i -τ i > 0, the directional perception coefficients α i = 0 and β i = 1, then from equation (6) it follows that From equation (5) it further follows that the lower flexible reference performance function ρ l,i (t) is relaxed, while the upper flexible reference performance function ρ u,i (t) is not relaxed; in the negative saturation regime, i.e. when τ c,i -τ i < 0, the directional perception coefficients α i = 1 and β i = 0, then from equation (6) it follows that From equation (5) it further follows that the upper flexible reference performance function ρ u,i (t) is relaxed, while the lower flexible reference performance function ρ l,i (t) is not relaxed; B, construct an improved extended state observer First, define the state vector z1 = q, and z3 = M o -1 (q)τ d The extended first-order state-space representation of the helicopter platform dynamics equation (3) is given by the active motion compensation as follows: where B = M o -1 (q) is a gain matrix, is a function vector, f = z3, representing the unknown total disturbance vector consisting of the matrix and vector uncertainties in the helicopter platform dynamics equation (3) and the equivalent disturbance caused by ship motion, denotes the first derivative of f; The improved extended state observer is constructed as follows: wherein and are estimates of z2and z3, respectively, υ is an auxiliary vector, K o,1 , K o,2 , and K o,3 are positive definite design matrices; C, design a kinematic control law of the active motion compensation helicopter platform C1, design an error conversion function The error conversion function f is designed as follows i (e i ,ρ l,i (t),ρ u,i (t)) : where s 1,i denotes the conversion variable, and ln(·) denotes the natural logarithm function; the error conversion function f i (e i , p l,i (t), p u,i (t)) converts the pose error e i into the conversion variable s 1,i satisfying the performance constraint condition (4); for the convenience of subsequent control design, the derivative of s 1,i with respect to time is taken: In the formulae, C2, design a kinematic control law Let the vector s1= [s 1,1 ,s 1,2 ,…,s 1,6 ] T be defined, and take the derivative with respect to time, and according to equation (17) and e = q - q d , we have: where P = diag(P1, P2,..., P6), Q = [Q1, Q2,..., Q6] T ; Consider the virtual control input of the form (17) The kinematic control law is designed as as follows: χ = -K1P -1 s1+ Q (19) In the formula, is a positive definite design matrix; D, design a flexible pre-specified performance control law of the active motion compensation helicopter platform D1, define a new error vector s2 = z2 - x, take the derivative of s2 with respect to time, and according to equation (11) and Δτ = τ - τ c , we get: D2, design a continuous auxiliary dynamic system as follows: wherein is a saturated compensation signal; is a positive definite design matrix, κ a and κ b are arbitrary small design constants, 0 < κ a < κ b ; D3, design a pre-specified performance control law The flexible pre-specified performance control law of the active motion compensation helicopter platform comprises a nonlinear feedback control law, a disturbance rejection control law and an anti-windup control law, and is represented as follows: wherein and is a positive definite design matrix; The feedback control law is used for converging the pose error of the support surface on the helicopter platform in an inertial coordinate system; the disturbance rejection control law is used for compensating total disturbances composed of helicopter platform model uncertainties and equivalent disturbances caused by ship motion; and the anti-windup control law is used for compensating helicopter platform control input saturation.

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