88 results about "Space tether" patented technology

The invention relates to a method of taking over and controlling attitude after a space tethered robot captures a flexible target satellite. Taking regard of nondeterminacy of inertia, the coupling effect, external interference and other factors, the method of taking over and controlling attitude after space tethered robot captures flexible target satellite establishes a complex attitude and orbit coupling kinetic equation, designs inner and outer ring terminal sliding mode controllers, and gives consideration on the saturation characteristics of a thruster and a tether so as to stably control the attitude and angular velocity of the complex. The method of taking over and controlling attitude after a space tethered robot captures a flexible target satellite includes the following steps: establishing an attitude kinetic equation of a complex after a space tethered robot captures a target satellite; designing inner and outer ring terminal sliding mode controllers and the corresponding adaptive law; taking the inner ring control law and the outer ring control law as the input of a control system to take over and control the attitude after the flexible target satellite is captured; and proving Lyapunov stability. The method of taking over and controlling attitude after a space tethered robot captures a flexible target satellite can solve the problem that the flexible complex parameters are not determined and the self-supplied thruster of the space tethered robot is saturated.

The invention discloses a method for stably controlling the posture of a complex after a target is caught by a space tethered system mechanical arm. First, a posture controller for the complex formed after the target is caught by the space tethered system mechanical arm is designed, the expected posture control moment of the complex is worked out, and then the expected posture moment is achieved through a thruster of the space tethered system mechanical arm, the structure of the mechanical arm and the tension of a tether. According to the method, the changes of the form of the space tethered system mechanical arm are considered for use, the posture of a space tethered system robot can be stably controlled through the tension of the space tether and the thruster of the space tethered system robot, the application range of the tension of the tether is broadened substantially due to the changes of the form of the mechanical arm, and thus stable control over the posture of the complex formed after the target is caught by the space tethered system robot can be effectively achieved.

The invention discloses a space tethered capturing system based non-cooperative target quality identification method. After a space tethered robot system captures a space non-cooperative target, a target kinetic parameter is identified in the later capture stage and a recovery stage and then self-adaptive recovery control is completed based on the identification result. The space tethered capturing system based non-cooperative target quality identification method includes firstly, providing a parameter identification method to identify quality of the space non-cooperative target primarily in the later capture stage; secondly, providing an optimal control algorithm according to influences of different recovery control algorithms to parameter identification; and thirdly, completing self-adaptive control in space non-cooperative target recovery process on the basis of the primary parameter identification result in the later capture stage.

The invention discloses a space tether robot target capture stable control method which comprises the following steps: 1) establishing a space tether robot target capture kinetic equation; 2) calculating correction amount e of expected pose of a space tether robot; 3) estimating uncertainty of a system model of the space tether robot; and 4) calculating stable control force and control moment Q of the space tether robot. The impedance control method is adopted in the invention, so that influence due to impact force in the capture process can be reduced. The uncertainty of the space tether robot model is estimated through a neural network, so that compensation control can be carried out on influence due to uncertainty effectively; overshoot is small in the control process; convergence time is shorter; and control precision is higher.

The invention provides a three-axis active posture control method for a space tether-robot. The method includes the steps that according to the orbit dynamics characteristic of the space tether-robot, the nominal tension required by a space tether of the space tether-robot in the equilibrium state is calculated; according to posture kinematics and dynamical equations of the space tether-robot, a control moment variable is determined, a state equation and an output equation of posture kinematics of the space tether-robot are established, and posture control moments in three directions are calculated according to a feedback linearization control law; according to the relation among the control moments, the space tether connecting point positions and the rotating speed of a reaction wheel, the corresponding space tether connecting point positions and the rotating angular speed of the reaction wheel are obtained. By the adoption of the method, according to the posture of a target and with the use of the space tether and the reaction wheel, three-axis posture coordinated control is conducted on the posture of the space tether-robot, and the method is suitable for three-axis posture control of the space tether-robot when the space tether-robot is located on a connecting line of a space platform and the geocenter.

The invention relates to a stereoscopic vision fast image stitching method suitable for a space tether-robot. Based on ORB feature detection and an image stitching algorithm of a description algorithm, by comparing the method with a traditional stitching algorithm, it can be seen that the method is high in stitching precision and robustness and good in final image stitching effect, has the highest speed when compared with the traditional stitching algorithm, and has a wide application range and good application prospects. Compared with the prior art, the method has the advantages that time consumption of the method is small, the stitching speed is significantly improved, the infusion effect of stitching portions of an image is good, and noise immunity is strong.

The present invention relates to a Lagrange dynamic model of a space tether system and a controller. Aiming at the modeling problem of the space tether system, six parameters consisting of three attitude angles, a tether surface internal angle, a tether surface external angle, the tether length and the like are considered, the Lagrangian method is employed to detailedly deduce the generalized force model of the tether, and a generalized state stability controller is designed. The Lagrange dynamic model of space tether system and the controller can solve the tether system target attitude modeling problem when a platform is equivalent to the target quality; and the designed controller can realize the control of the tether system generalization state variables after target capture.

The invention discloses a space debris recovery control method based on a tethered technology. The space debris recovery control method is characterized by comprising the following steps that 1, the tether elasticity is considered, a space tethered debris system is researched by adopting an elastic rod module, and a system dynamics differential equation is built according to a class II Lagrange equation; 2, the system dynamics equation in the step 1 is rewrote into a non-dimensional system dynamics equation; 3, the in-surface outer pivot angle vibration abatement problem of nonlinear time-varying system dynamics equation in the recovery process is researched, and the tether length change analysis control law and the in-surface pitch angle value range in the expectation equilibrium position in the debris recovery process are inferred; and 4, the stability of the system and the value range, keeping stable asymptotically, of a pitch angle in an expectation surface are further analyzed through the Floquet theory. Through the space debris recovery control method, the effect that debris is stably recovered nearby an on-orbit spacecraft can be ensured, and meanwhile the safety in the recovery process especially the safety in the end time can be ensured.

The invention relates to a tethered swing suppression method using towing aircraft maneuvering in towing orbital transfer. Orbit control force of a towing aircraft is used and the orbit of the towing aircraft is also controlled and tethered swing is suppressed so that the problem of quick releasing of the tether can be avoided without using tethered control force, the conflict with the requirement of target satellite attitude stable control can be avoided, and the practicality is great. Compared with the similar technologies at home and abroad, the method has the following positive effects that additional arrangement of a thruster at the end of the target satellite can be avoided, tethered swing is suppressed by using the thruster and the complexity of the system can be reduced; the requirement of quick retreating and releasing of the tether can be avoided, the requirement for a tether retreating and releasing device can be reduced and the problem of quick releasing of the space tether can be avoided; and the tether tension conflict with the situation of using tether tension to stabilize the target satellite attitude can be avoided, and the design difficulty of the controller can be reduced.

The invention relates to a real-time space target feature point tracking method suitable for a space tethered robot. The method is mainly formed by a feature point extraction algorithm, a feature point matching algorithm, discrete point elimination, accurate positioning and a self-adaptive strategy. Feature points extracted through an improved SURF algorithm are strong in robustness and stability. The method enables the feature point matching accuracy and target positioning accuracy to be high, and is suitable for stable tracking of targets which have rapid changes in positions and gestures and are simple in structure in a multi-scale image sequence. The method has robustness in various types challenging situations, and the tracking process has short-term anti-occlusion capacity. The method can be used for achieving the real-time detection and tracking of a plurality of types of targets, is suitable for real-time robustness tracking for the space targets which have rapid changes in positions and gestures and are simple in structure in the multi-scale image sequence.

The invention relates to a space tether capturing system keeping stage tether in-plane and out-plane angle stable control method. Firstly, a space tether capturing system keeping stage kinetic model is built; according to a sliding mode variable equation, a space tether capturing system keeping stage kinetic equation is sorted; a space tether capturing system keeping stage Super-Twisting control law is designed; and the magnitude of the space tether capturing system keeping stage tether in-plane and out-plane angle stable control torque is calculated. The method of the invention has the beneficial effects that the designed control law can quickly eliminate swing of in-plane and out-plane angles in an interference condition, and the tether in-plane and out-plane angles can be controlled to be expected values; and in comparison with the traditional sliding mode method, the designed control law can realize continuous control input and eliminate chattering.

The invention provides an under-actuated release control method based on a nonlinear space tether system. The method comprises the following steps: 1, a dumbbell model is adopted, system dynamics differential equations are built according to a second kind Lagrange equation, and a dimensionless form is introduced in the differential equations; 2, based on a normal form expression for the above dynamics differential equations, expected values for a system in-plane pitching angle and an out-plane rolling angle are set, and the balance position of the system in the release process is obtained; 3, starting from the balance position of the system, a tether length change control law for realizing tether release is deduced and obtained; and 4, the range for the expected in-plane pitching angle is determined to ensure the tether release process to be asymptotically stable under effects of the control law. Numerical simulations show that the space tether can be released asymptotically stably under effects of the release control method provided by the invention, and an attractor capable of covering the balance point and an attraction domain with enough thickness can be found out.

The invention provides a fuel optimal pose coordination method suitable for a space tether robot in the target approaching process. The method includes the steps that first, a system kinetic model is established; second, the system kinetic model is dispersed; third, an optimal trajectory control signal is planned; fourth, after a real state signal x of a coordination optimal controller passing through the space tether robot system and an ideal condition signal x* calculated in the third step are subtracted, an error signal is acquired, the error signal is multiplied by a time varying gain coordinate coefficient matrix KN to acquire a deviation control signal , the deviation control signal is added to the ideal condition signal x* calculated in the third step to acquire a control signal, and accordingly coordination control can be carried out.

The invention provides a method for establishing a universal mechanical model of a tethered space robot. The method can meet requirements in modeling tethered space robots of different tasks and different structures, simplify the modeling operation, and improve the modeling and resolving efficiencies. The method comprises the following steps: 1, confirming the topologic structure and structural parameters of the tethered space robot, wherein the topologic structure of the tethered space robot comprises a space tether as well as a space platform and an operation robot which are connected through the space tether and both adopt multi-rigid body structures; 2, establishing a mechanical model of the space tether; 3, establishing a mechanical model of the tethered space robot of an earth core inertial system based on the Hamilton principle and in combination with the mechanical model of the space tether; 4, converting the mechanical model of the tethered space robot of the earth core inertial system into a track inertial system; 5, discretizing the system model by using a finite element method, and establishing the universal mechanical model of the tethered space robot.

The invention provides a spinning unfolding and folding optimum control method of a dual-body star space tethered formation system. The method includes the steps that first, constraint conditions are determined, wherein the constraint conditions comprise a controlled quantity constraint, a state constraint, a terminal constraint and a dynamics constraint; secondly, performance indexes are selected according to task requirements; afterwards, the optimum control quantity M and the optimum ideal condition are acquired through an hp-self-adaptation pseudo-spectral method; at last, a state error measuring controller and an executing mechanism error controller are designed to control errors of the ideal condition and the optimum control and errors of the virtual condition and practical control respectively. According to the spinning unfolding and folding optimum control method of the dual-body star space tethered formation system, a spinning kinetic model is established based on spinning motion, the dual-body star space tethered formation system can be controlled to complete a spinning unfolding and folding task smoothly under the certain performance indexes and the constraint conditions, and certain theoretical reference is provided for spinning unfolding and folding control of a general dual-body star space tethered formation system.

The invention belongs to the technical field of spacecraft flight, and particularly relates to a modeling method of a space three-body flexible tethered satellite formation system under a non-inertialreference coordinate system. The modeling method comprises the following steps that firstly, a satellite formation system model and a non-inertial reference system fixed to the system centroid are established; secondly, a flexible tether connecting a satellite is discrete into a plurality of tether units, and the satellite and tether unit particles are numbered; and finally, dynamic equations ofdiscrete element particles under the non-inertial reference system are established, and then the dynamic equations of the satellite formation system are derived. According to the modeling method of the space three-body flexible tethered satellite formation system under the non-inertial reference coordinate system, modeling is carried out under the non-inertial reference system, redundant steps such as selecting generalized coordinates and coordinate transformation are not required, and simultaneously flexibility of the space tether is considered, so that the method is faster and more accuratein describing various space dynamic behaviors of a formation system and revealing spin stability and instability states of the system. In addition, the modeling method of the space three-body flexibletethered satellite formation system under the non-inertial reference coordinate system can further be extended to modeling of a four-body or multi-body space tethered formation system and has great practical value.

Mechanism for passively deploying expendable space tethers on orbit, by means of an initial separation impulse only, provided by a simple spring system that is part of the mechanism itself. The passive deployment of the space tether and a tethered end-mass is provided by the particular mechanism devised, having very low deployment friction and resistance. Tether deployment brake towards the final part of deployment is produced by a daisy-like brake, stored within the winding of the fixed tether spool so that it is automatically deployed (opened) and starts its deployment braking or resistance function from a planned point of the tether deployment in space.

A space transport system for transporting payloads between points on the ground, in the air, and in outer space, includes a tether wheels able to accept payload from the ground or a low, slow position and transport it at high velocity to either another low, slow location on the same planet, or to a high speed space trajectory.

The invention provides a two-body star space tethered formation system configuration retention coordination control method. Firstly, the two-body star space tethered formation system configuration retention coordination control method is built; tethered pull force of two rotary arms and spinning torque of a main spacecraft serve as control output quantity, and a configuration retention controller is designed; an error threshold value coefficient initial value is set, and the configuration retention controller is adopted to control rotary arm errors and spinning speed errors produced in a spinning process of a two-body star space tethered formation system. In actual application, different control effects can be obtained by regulating error threshold value coefficients, so that requirements for fuel consumption and control time are met. The two-body star space tethered formation system configuration retention coordination control method provides theoretical support for research of configuration retention control.

The invention provides a simulation method applicable to a space tethered system of a stratospheric satellite system. The method comprises the steps of averagely dividing a tether to be a plurality of sections with the same length, building a mathematic model for the stratospheric satellite system, deriving a node constraint equation and solving a second derivative according to the position relationship between a node and each section of the tether, and performing integral solution on the equation by using a fourth-order Runge-Kutta method, so as to finish a simulation task for the tethered system of the stratospheric satellite system. According to the simulation method provided by the invention, with a view to the gravity and softness of the space tethered system, the accuracy and effectiveness for transferring the magnitude and direction of the control force by the space tethered system can guaranteed.

The invention discloses an obstacle detection method for a space tether robot in a capturing area. The obstacle detection method comprises the following steps: the module value and direction of an image gradient are firstly worked out in the capturing area; an obtained communication pixel area is used as a straight line segment candidate area according to a gradient module value pseudo sequencing result; a bounding rectangle is used for describing the candidate area, and the long axis which meet criteria is the required straight line segment outline of an obstacle; finally the three-dimensional coordinate of the outline and the closest distance are obtained according to points of the outline. According to the invention, the detecting part of the straight line segment adopts a straight line segment detecting method based on image gradient information; the straight line segment can be detected rapidly and accurately in various complex scenes; obstacles surrounding capturing points are detected by adopting the obstacle detection method, the detected points at the edges of the straight line segment are conducted with three-dimensional reconstruction, the three-dimensional distance from the capturing points is calculated, points at nearest distance are found, and the three-dimensional coordinate of the straight line segment and the nearest distance are obtained.

Mechanism for passively deploying expendable space tethers on orbit, by means of an initial separation impulse only, provided by a simple spring system that is part of the mechanism itself. The passive deployment of the space tether and a tethered end-mass is provided by the particular mechanism devised, having very low deployment friction and resistance. Tether deployment brake towards the final part of deployment is produced by a daisy-like brake, stored within the winding of the fixed tether spool so that it is automatically deployed (opened) and starts its deployment braking or resistance function from a planned point of the tether deployment in space.

The invention discloses an impact-proof buffer release control method and experiment apparatus for a space tether system combination body. The impact-proof buffer release control experiment apparatus comprises a master control computer, a visual sense detection device, an optics identifier, an object emulator, an elastic tether, a tether folding and unfolding apparatus, a task platform emulator and a basic platform. An impact-proof buffer release ground experiment platform capable of simulating a space microgravity environment is designed, and a foundation is laid for verifying effectiveness of proposed control strategies on the ground. The impact-proof buffer control method for the tether system combination body is simple, effective and capable of realizing impact-proof buffer control over the combination body via tension force control over tethers so as to prevent system impact and collision The method is advantaged by simple control, rapid control responses, strong robustness, convenience of engineering implementation and the like. The method is suitable for controlling the space tether system combination body on general occasions. The impact-proof buffer release control method and experiment apparatus can be used for simulating the ground experiment platform in a weightless environment in space, and the platform can be widely applicable and can be used for conducting other relevant space simulation experiments.

The invention discloses a space tethered unfoldable covered surface system which mainly solves the problems of difficult unfolded formation and poor stability in the prior art. The space tethered unfoldable covered surface system comprises soft traction cables (1), a traction cable control mechanism (3), folded rings (4) and connection joints (5). Soft screen meshes (8) are bonded on rigid structures formed by the folded ring and the connection joints to form covered surfaces (2), and the soft traction cables (1) are connected with the covered surfaces (2) and the traction cable control mechanism (3) which controls the soft traction cables (1) to stretch out and draw back. Tension springs (6) and traction cables (7) are arranged in the folded rings (4), the tension springs (6) are stretched out when the folded rings (4) are folded, and when the folded rings (4) are unfolded, the tension springs (6) draw back, and the traction cables (7) are shortened. Under the effect of the tension of the traction cables, the connection joints (5) are unfolded to enable the covered surfaces to be unfolded into a horizontal working state from a vertical folded state, and the folded rings are locked through positioning devices on the connection joints (5). The space tethered unfoldable covered surface system has the advantages of being low in surface density, high in configuration actuary, large in storage rate and stable in posture, and can serve as an unfoldable screening device in the space.

The invention relates to an adaptive control method for target recycling of a space tethered robot after close-range capture. The adaptive control method comprises the steps of firstly deriving a compound body formed by the tethered robot and a captured target satellite, building a dynamic equation of the system in the recycling process, then designing the control force / moment in the recycling process according to a Lyapunov theorem, and designing a dynamic parameter identification law for the compound body, thereby achieving stable recycling of the compound body. According to the adaptive control method, the dynamic parameter identification law is put forwards for the first time, the whole recycling process can be enabled to be more accurate in calculation for control variables, and thus the recycling is more stable. The adaptive control method enables the compound body formed by the space tethered robot after capturing a non-cooperative target to be recycled stably and quickly through tether tension. The adaptive control method can overcome the natural instability in a problem of tether recycling on the basis of dynamic parameters of the compound body, and the compound body is recycled stably.

The invention relates to an extremely near visual servo control method for a space tethered robot. When the space tethered robot get close to a target in an extremely near mode, a sailboard support fills the integral camera field, capture points are difficult to measure, and a straight line which is formed by edges of the sailboard support is easy to be detected. The extremely near visual servo control method for the space tethered robot with the detected sailboard support edge line serving as input is served as a new visual servo method and effectively controls the space tethered robot to get close to the target to achieve the space operation task.

The invention provides a stability control method for unfolding of a three-dimensional space tether system operating in a low earth elliptical orbit in an initial stage. A tether is released to a desired length and the swing of the tether is restrained only by adjusting the limited tether tension without relying on other thrusters. The method comprises the following steps that S1, a two-body spacetether system dynamic model considering tether mass is established; S2, under the conditions such as disturbance, uncertainty, underactuation, restricted tether swing angle and tether tension, basedon a nonlinear model predictive control (NMPC) algorithm, a pseudo-spectral algorithm is used for discretizing an original nonlinear model, and an open loop optimal problem in predictive control is transformed into a nonlinear programming problem for solving; and S3, according to the solution of the nonlinear programming problem, the control quantity of the next control period is determined to form the closed-loop control. Finally, the three-dimensional space tether system operating in the low earth elliptical orbit is stably released and unfolded in the initial stage.

A system includes a gravity gradient stabilized space tether. The gravity gradient stabilized space tether includes a tether body having an upper end and a lower end. The gravity gradient stabilized space tether also includes an upper base station located at the upper end of the tether body and a lower base station located at the lower end of the tether body. The gravity gradient stabilized space tether further includes a device coupled to the lower base station. The device can be lowered to a distance below the lower base station to a rendezvous point that is proximate to an orbital path of a sub-orbital vehicle.

The invention provides a middle-distance and long-distance approximate position estimation method of a space tethered robot. According to the middle-distance and long-distance approximate position estimation method, a camera is used for measuring a target azimuth angle to obtain an azimuth angle of a target relative space tethered robot; a space tethering and rope releasing mechanism of the space tethered robot is combined to obtain tethering length information of the space tethered robot; a lossless Kalman filtering method is used for realizing position estimation of the space tethered robot. According to the middle-distance and long-distance approximate position estimation method of the space tethered robot provided by the invention, the tethering length information of the space tethered robot is sufficiently utilized and field angle information of a monocular camera is combined, so as to realize real-time estimation of the position of the space tethered robot.

The invention relates to a method for simulating a space tether system based on an integral interpolation method. The longitudinal movement of a tether is described by using a strain epsilon of a tether upper point, the transverse movement of the tether is described by using a tangent vector tau of the tether upper point, and separation solving of epsilon and tau is realized in the model discretization process, so that the defect of morbidity of the system is overcome, and the solving efficiency of the system is improved. The method has the advantages that: description of the tether release and pull-back process is implemented by increasing and decreasing the length of a first section of tether, and the first section of tether is processed according to the characteristic of a flexible rope, so that errors caused by regarding the tether as a rigid rod are avoided; meanwhile, during insertion of a new node, the state of the new node is computed by using an interpolation method, so that simulation noise caused by subjectively setting the state of the new node is avoided.