Performance of different Formation control methods between Multiple Spacecraft with local part communications

With the development of network and distributed computing, many applications of multi vehicle system have become possible, and motion transformation can be realized. In multi vehicle coordination, the interaction between information exchange topology and control plays an important role. Different formation control methods have different performance. Thus, in order to figure out which method is suitable for multiple spacecraft, the author simulated the signal unstable environment in space to test the robustness and consensus speed of the following three methods. The author use Bearing-only Formation Control, A leader–follower Formation Control and Affine Formation Control to test their performance with local part communications. The author use matlab and simulink to analog communication process of multiple spacecraft. Finally, the author find Affine Formation Control’s performance is the best. It has the best robustness and the fast consensus speed but more energy and signal paths to communicate.

On-Orbit Geometric Calibration from the Relative Motion of Stars for Geostationary Cameras

Affected by the vibrations and thermal shocks during launch and the orbit penetration process, the geometric positioning model of the remote sensing cameras measured on the ground will generate a displacement, affecting the geometric accuracy of imagery and requiring recalibration. Conventional methods adopt the ground control points (GCPs) or stars as references for on-orbit geometric calibration. However, inescapable cloud coverage and discontented extraction algorithms make it extremely difficult to collect sufficient high-precision GCPs for modifying the misalignment of the camera, especially for geostationary satellites. Additionally, the number of the observed stars is very likely to be inadequate for calibrating the relative installations of the camera. In terms of the problems above, we propose a novel on-orbit geometric calibration method using the relative motion of stars for geostationary cameras. First, a geometric calibration model is constructed based on the optical system structure. Then, we analyze the relative motion transformation of the observed stars. The stellar trajectory and the auxiliary ephemeris are used to obtain the corresponding object vector for correcting the associated calibration parameters iteratively. Experimental results evaluated on the data of a geostationary experiment satellite demonstrate that the positioning errors corrected by this proposed method can be within ±2.35 pixels. This approach is able to effectively calibrate the camera and improve the positioning accuracy, which avoids the influence of cloud cover and overcomes the great dependence on the number of the observed stars.

Magnetized Black Holes: Ionized Keplerian Disks and Acceleration of Ultra-High Energy Particles

Properties of charged particle motion in the field of magnetized black holes (BHs) imply four possible regimes of behavior of ionized Keplerian disks: survival in regular epicyclic motion, transformation into chaotic toroidal state, destruction due to fall into the BHs, destruction due to escape along magnetic field lines (escape to infinity for disks orbiting Kerr BHs). The regime of the epicyclic motion influenced by very weak magnetic fields can be related to the observed high-frequency quasiperiodic oscillations. In the case of very strong magnetic fields particles escaping to infinity could form UHECR due to extremely efficient magnetic Penrose process – protons with energy E > 10 21 eV can be accelerated by supermassive black holes with M ∼ 10 10 M ⊙ immersed in magnetic field with B ∼ 10 4 Gs.

Deployment Kinematic Analysis and Control of a New Hoop Truss Deployable Antenna

Firstly, based on the structural characteristics of a new type of hoop truss deployable antenna, this paper derives the motion transformation relation between two hoop modules by using the method of coordinate transformation, and establishes the general model for deployment kinematic analysis, which can be applied to analyze the position, velocity and acceleration of any point on the structure. Secondly, according to the relation between the driving cable and the hoop module, the motion planning of the hoop module is transformed into the motion control of the driving cable, which can realize the deploying position control of the antenna. Finally, numerical simulations show the control method can make the antenna smoothly deploy following the specified deployable motion.

Comprehensive theory of differential kinematics and dynamics towards extensive motion optimization framework

This paper presents a novel unified theoretical framework for differential kinematics and dynamics for the optimization of complex robot motion. By introducing an 18×18 comprehensive motion transformation matrix, the forward differential kinematics and dynamics, including velocity and acceleration, can be written in a simple chain product similar to an ordinary rotational matrix. This formulation enables the analytical computation of derivatives of various physical quantities (e.g. link velocities, link accelerations, or joint torques) with respect to joint coordinates, velocities and accelerations for a robot trajectory in an efficient manner ([Formula: see text], where [Formula: see text] is the number of the robot’s degree of freedom), which is useful for motion optimization. Practical implementation of gradient computation is demonstrated together with simulation results of robot motion optimization to validate the effectiveness of the proposed framework.