CN105353790A - Tethered space robot complex stable control method after target capture - Google Patents

Abstract

The invention discloses a tethered space robot complex stable control method after target capture. The method comprises the following steps that 1) a tethered space robot complex kinetic equation after target capture is established; 2) virtual control input xi2c is calculated; 3) expected system state quantity xi2d is obtained through calculation; 4) complex model uncertainty lambda<^><L> after capture is estimated; and 5) complex stable control force and control moment Q after capture are calculated. A controller is designed by utilizing an instruction filtering method under the condition of considering the tethering and releasing speed limitation so that stability of the controller is guaranteed. The self-adaption law is designed, complex uncertainty is estimated and compensation is performed in the controller so that control precision is enhanced. Control input is limited via a filter so that stability of the controller is enhanced.

Description

Method for stably controlling complex after target capture of space tethered robot

[ technical field ] A method for producing a semiconductor device

The invention belongs to the field of spacecraft control technology research, and particularly relates to a method for stably controlling a complex after target capture of a space tethered robot.

[ background of the invention ]

The space tether robot has wide functions in space in-orbit service due to the characteristics of flexibility, safety, low fuel consumption and the like, and can perform operations such as invalid satellite rescue, space garbage cleaning, auxiliary orbit transfer and the like.

According to the task flow of the space tether robot, the method can be divided into five stages of releasing, approaching a target, capturing the target, stabilizing the captured target and operating the captured target, wherein the stabilization control of a complex after capturing the target is one of the main researches of the space tether robot.

After the space tether robot catches the target, due to collision and target spinning, the posture of the caught complex is unstable, unfavorable conditions such as tether winding and the like can occur when control is not applied, and the tension of the tether generates great interference on the platform, so that the posture of the caught complex needs to be controlled. Because the control torque of the space robot is limited, when the captured complex is stably controlled, the condition that the input saturation of the thruster is limited occurs, and the control performance of the complex is greatly influenced. In addition, due to the limitation of the rope releasing mechanism and the consideration of safety factors, the releasing and releasing speed of the tied rope is limited, so that a proper control strategy needs to be designed to ensure the stability of the posture control of the complex under the condition that the releasing and releasing speed of the tied rope is limited.

The stability of the complex after target capture is one of important tasks of the space rope robot, and the stability control of the complex after target capture directly influences the smooth proceeding of subsequent dragging track change or recovery operation tasks, so that the stability control method becomes a research focus in the field of space rope robots.

The application numbers are: 201310018221.7, the Chinese patent proposes a method for controlling a complex after the space tether robot catches, which realizes the stable control of the complex by using a thruster and a tether; the application numbers are: 201410341562.2 discloses that the posture of the composite body is stabilized by using the pulling force of the tether and the configuration change of the spatial tether mechanical arm to generate the required control moment. The above patents only consider the stable control of the posture of the complex, and the stable control of the complex also needs the stable control of the position, thus limiting the use of the two control methods to some extent.

[ summary of the invention ]

The invention aims to solve the problems and provides a method for stably controlling a complex after target capture of a space tethered robot, which can realize stable control of the pose of the complex after target capture.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

a method for stably controlling a complex after target capture of a space tethered robot comprises the following steps:

1) establishing a complex kinetic equation after the space tethered robot target is captured;

2) computing virtual control inputs ξ_2c；

3) The desired system state quantity ξ is calculated_2d；

4) Estimating post-capture complex model uncertainty

5) And calculating the stable control force and the stable control moment Q of the captured complex.

The invention further improves the following steps:

in the step 1), the space tethered robot target capture kinetic equation is as follows:

$M\left(\mathrm{\&xi;}\right)\stackrel{\&CenterDot;\&CenterDot;}{\mathrm{\&xi;}}+N(\mathrm{\&xi;},\stackrel{\&CenterDot;}{\mathrm{\&xi;}})\stackrel{\&CenterDot;}{\mathrm{\&xi;}}+G\left(\mathrm{\&xi;}\right)=Q$

wherein:l is the length of the spatial tether, α is the inner angle of the spatial tether face, β is the outer angle of the spatial tether face;theta and psi are complex attitude angles; m is a system inertia matrix; n non-linear velocity-related terms; g a gravity related term; q is the control force and the control moment of the space tethered robot.

In said step 2), according toComputing virtual control inputs ξ_2cIn which K is₁For positive definite matrix of design ξ_1e＝ξ₁-ξ_1dWherein ξ₁＝ξ，ξ_1dIs ξ₁The expected value of (c) is,is ξ_1eDerivative with respect to time.

In the step 3), the expected system state quantity ξ is calculated_2dThe method comprises the following steps: by first order filtering $\mathrm{\&epsiv;}{\stackrel{\&CenterDot;}{\mathrm{\&xi;}}}_{2d}+{\mathrm{\&xi;}}_{2d}={\mathrm{\&xi;}}_{2c},{\mathrm{\&xi;}}_{2d}\left(0\right)={\mathrm{\&xi;}}_{2c}\left(0\right)$ Implementation, where > 0.

The step 4)In, complex model uncertaintyObtained by the following method:wherein, a and_λis positive, η · η ═ η₁η₁η₂η₂η₃η₃)^TProjection operator, Proj (·), η ═ ξ_2e- χ, χ pass filterObtaining; k₂And P is a positive definite matrix.

In the step 5), calculating the stable control force and the stable control torque Q of the captured complex: $Q_0=M_0{\stackrel{\&CenterDot;}{\mathrm{\&xi;}}}_{2d}+N_0{\mathrm{\&xi;}}_{2d}+G_0+(N_0-K_2)\mathrm{\&chi;}-{\mathrm{P\&xi;}}_{1e}-\frac{{\widehat{\mathrm{\&lambda;}}}_L\&CenterDot;\mathrm{\&eta;}}{\left|\mathrm{\&eta;}\right|+{\mathrm{\&epsiv;}}_{\mathrm{\&lambda;}}},$ wherein Q is Q₀Obtained through a saturation step, M₀Is a system nominal inertia matrix; n is a radical of₀A nominal non-linear velocity dependent term; g₀A nominal gravity related term.

Compared with the prior art, the invention has the following beneficial effects:

the method for stably controlling the complex after the space tethered robot captures the target utilizes an instruction filtering method to design the controller under the condition of taking the limitation of the rope releasing speed of the tethered robot into consideration as a whole, and ensures the stability of the controller. The invention designs a self-adaptive law, estimates the uncertainty of the complex, compensates in the controller and improves the control precision. The invention limits the control input through the filter, thereby improving the stability of the controller.

[ description of the drawings ]

Fig. 1 is a schematic diagram of space tethered robot target capture.

In the figure: 1. capturing a target; 2. a spatial tether robot; 3. a spatial tether; 4. a space platform; 5. the earth; 6. capturing the complex.

[ detailed description ] embodiments

The present invention is described in detail below with reference to the attached drawings. It should be noted that the described embodiments are only intended to facilitate the understanding of the present invention, and do not have any limiting effect thereon.

Referring to fig. 1, the method for controlling the stability of the complex after the target of the space tethered robot is caught comprises the following steps:

1) establishing a complex kinetic equation after space tethered robot target capture

$M\left(\mathrm{\&xi;}\right)\stackrel{\&CenterDot;\&CenterDot;}{\mathrm{\&xi;}}+N(\mathrm{\&xi;},\stackrel{\&CenterDot;}{\mathrm{\&xi;}})\stackrel{\&CenterDot;}{\mathrm{\&xi;}}+G\left(\mathrm{\&xi;}\right)=Q$

Wherein the system stateWherein l, α and β are respectively the length of the space tether, the inner angle of the space tether face and the outer angle of the space tether face,theta and psi are attitude angles of the captured complex;is a generalized control force.

2) Computing virtual control inputs ξ_2c

ξ₁＝ξ，Get ξ_1dIs ξ₁The tracking error can then be expressed as:

ξ_1e＝ξ₁-ξ_1d

pair ξ_1eThe two-sided derivation can be found:

${\stackrel{\&CenterDot;}{\mathrm{\&xi;}}}_{1e}={\stackrel{\&CenterDot;}{\mathrm{\&xi;}}}_1-{\stackrel{\&CenterDot;}{\mathrm{\&xi;}}}_{1d}={\mathrm{\&xi;}}_2-{\stackrel{\&CenterDot;}{\mathrm{\&xi;}}}_{1d}$

let ξ_2cIs ξ₂The virtual input of (2) is designed as:

${\mathrm{\&xi;}}_{2c}=-K_1{\mathrm{\&xi;}}_{1e}+{\stackrel{\&CenterDot;}{\mathrm{\&xi;}}}_{1d}$

wherein, K₁Is a positive definite matrix.

3) The desired system state quantity ξ is calculated_2d

Considering that the rope releasing speed of the rope is limited, the system state ξ is filtered by the instruction₂The specific method for limiting is as follows:

$\mathrm{\&epsiv;}{\stackrel{\&CenterDot;}{\mathrm{\&xi;}}}_{2d}+{\mathrm{\&xi;}}_{2d}={\mathrm{\&xi;}}_{2c},{\mathrm{\&xi;}}_{2d}\left(0\right)={\mathrm{\&xi;}}_{2c}\left(0\right)$

wherein > 0.

4) Estimating post-capture complex model uncertainty

ξ_2eThe error kinetics equation can be expressed as:

$M_0{\stackrel{\&CenterDot;}{\mathrm{\&xi;}}}_{2e}=Q-N_0{\mathrm{\&xi;}}_{2e}-N_0{\mathrm{\&xi;}}_{2d}-G_0-\mathrm{\&rho;}-M_0{\stackrel{\&CenterDot;}{\mathrm{\&xi;}}}_{2d}$

wherein,it is a system uncertainty that is mainly caused by errors in parameters such as composite mass, moment of inertia, and tether attachment point location. Assuming that the system uncertainty is limited, there is an upper bound λ_LI.e. | | ρ (Δ M)₀,ΔN₀,ΔG)||≤||λ_LDesign adaptation law pair lambda_LEstimating to obtain the estimated value

${\stackrel{\&CenterDot;}{\widehat{\mathrm{\&lambda;}}}}_L=\mathrm{Pr}oj\left(\frac{a\mathrm{\&eta;}\&CenterDot;\mathrm{\&eta;}}{\left|\mathrm{\&eta;}\right|+{\mathrm{\&epsiv;}}_{\mathrm{\&lambda;}}}\right)$

Wherein, a and_λis positive number, η & η ═ η₁η₁η₂η₂η₃η₃)^TThe projection operator of Proj (DEG), η is used for correcting tracking error and satisfies η - ξ_2e- χ, wherein χ is obtained by a first order filter:

$M_0\stackrel{\&CenterDot;}{\mathrm{\&chi;}}=-K_2\mathrm{\&chi;}+Q-Q_0$

wherein, K₂Is a positive definite matrix.

5) Calculating the stable control force and control moment Q of the captured complex

According to $Q_0=M_0{\stackrel{\&CenterDot;}{\mathrm{\&xi;}}}_{2d}+N_0{\mathrm{\&xi;}}_{2d}+G_0+(N_0-K_2)\mathrm{\&chi;}-{\mathrm{P\&xi;}}_{1e}-\frac{{\widehat{\mathrm{\&lambda;}}}_L\&CenterDot;\mathrm{\&eta;}}{\left|\mathrm{\&eta;}\right|+{\mathrm{\&epsiv;}}_{\mathrm{\&lambda;}}}$ To obtain Q₀Then Q is added₀Obtaining Q in an input saturation link, wherein Q is an actual input control force and a control moment; m₀Is a system nominal inertia matrix; n is a radical of₀A nominal non-linear velocity dependent term; g₀A nominal gravity related term.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims (6)

1. A method for stably controlling a complex after space tethered robot target capture is characterized by comprising the following steps:

1) establishing a complex kinetic equation after the space tethered robot target is captured;

2) computing virtual control inputs ξ_2c；

3) The desired system state quantity ξ is calculated_2d；

4) Estimating post-capture complex model uncertainty

5) And calculating the stable control force and the stable control moment Q of the captured complex.

2. The method for controlling stability of the complex after target capture of the spatial tether robot according to claim 1, wherein in the step 1), the target capture kinetic equation of the spatial tether robot is as follows:

$M\left(\mathrm{\&xi;}\right)\stackrel{\&CenterDot;\&CenterDot;}{\mathrm{\&xi;}}+N(\mathrm{\&xi;},\stackrel{\&CenterDot;}{\mathrm{\&xi;}})\stackrel{\&CenterDot;}{\mathrm{\&xi;}}+G\left(\mathrm{\&xi;}\right)=Q$

wherein:l is the length of the spatial tether, α is the inner angle of the spatial tether face, β is the outer angle of the spatial tether face;theta and psi are complex attitude angles; m is a system inertia matrix; n non-linear velocity-related terms; g a gravity related term; q is the control force and the control moment of the space tethered robot.

3. The method for controlling the stability of the complex after the target capture of the space tether robot as claimed in claim 1, wherein the step 2) is based onComputing virtual control inputs ξ_2cIn which K is₁For positive definite matrix of design ξ_1e＝ξ₁-ξ_1dWherein ξ₁＝ξ，ξ_1dIs ξ₁The expected value of (c) is,is ξ_1eDerivative with respect to time.

4. The method for controlling stability of a complex after target capture of a space tethered robot as claimed in claim 1 wherein step 3) calculates the expected system state quantity ξ_2dThe method comprises the following steps: by first order filtering $\mathrm{\&epsiv;}{\stackrel{\&CenterDot;}{\mathrm{\&xi;}}}_{2d}+{\mathrm{\&xi;}}_{2d}={\mathrm{\&xi;}}_{2c},{\mathrm{\&xi;}}_{2d}\left(0\right)={\mathrm{\&xi;}}_{2c}\left(0\right)$ Implementation, where > 0.

5. The method for controlling stability of the complex after target capture of the space tethered robot as claimed in claim 1, wherein in step 4), the uncertainty of the complex model is determinedObtained by the following method:wherein, a and_λis positive, η · η ═ η₁η₁η₂η₂η₃η₃)^TProjection operator, Proj (·), η ═ ξ_2e- χ, χ pass filterObtaining; k₂And P is a positive definite matrix.

6. The method for controlling the stability of the complex after the target of the space tethered robot is captured according to claim 1, wherein in the step 5), the stability control force and the control moment Q of the complex after the target is captured are calculated: $Q_0=M_0{\stackrel{\&CenterDot;}{\mathrm{\&xi;}}}_{2d}+N_0{\mathrm{\&xi;}}_{2d}+G_0+(N_0-K_2)\mathrm{\&chi;}-{\mathrm{P\&xi;}}_{1e}-\frac{{\widehat{\mathrm{\&lambda;}}}_L\&CenterDot;\mathrm{\&eta;}}{\left|\mathrm{\&eta;}\right|+{\mathrm{\&epsiv;}}_{\mathrm{\&lambda;}}},$ wherein Q is Q₀Obtained through a saturation step, M₀Is a system nominal inertia matrix; n is a radical of₀A nominal non-linear velocity dependent term; g₀A nominal gravity related term.