scholarly journals Formation-Keeping Strategies At The Earth-Moon L4 Triangular Libration Point

2021 ◽  
Author(s):  
Frank Y. W. Wong
Keyword(s):  
Degrees Of Freedom ◽  
Sliding Mode ◽  
Libration Point ◽  
Control Technique ◽  
Solar Sails ◽  
Hybrid Propulsion ◽  
Triangular Libration Point ◽  
Spacecraft Formation ◽  
The Earth ◽  
Formation Keeping

This thesis examines the use of thrusters and solar sails for spacecraft formation keeping control at the Earth-Moon L4 point. Particular emphasis was placed on the study of underactuated control, in which fewer control inputs than the system's degrees of freedom are available. A linear LQR control scheme, an integral augmented sliding mode controller and a bang-bang controller were applied to the dynamic spacecraft system. The nonlinear controllers produced errors falling with tighter tolerances than the linear controllers in the perturbed environment. Performing similarly well as the underactuated thrusters system was the solar-sails-controlled spacecraft formation using a bang-bang controller. This shows that solar sails could be a viable propellantless technique for relative control. A linear control technique was able to bound errors to within a couple of hundred metres, using a hybrid propulsion system. Of the cases studied, only the fully-actuated thrusters-based system was able to explicitly track a circular trajectory, but had [Delta]V requirement of more than 100 times greater than that needed for tracking the natural, elliptical trajectory.

scholarly journals Formation-Keeping Strategies At The Earth-Moon L4 Triangular Libration Point

2021 ◽  
Author(s):  
Frank Y. W. Wong
Keyword(s):  
Degrees Of Freedom ◽  
Sliding Mode ◽  
Libration Point ◽  
Control Technique ◽  
Solar Sails ◽  
Hybrid Propulsion ◽  
Triangular Libration Point ◽  
Spacecraft Formation ◽  
The Earth ◽  
Formation Keeping

This thesis examines the use of thrusters and solar sails for spacecraft formation keeping control at the Earth-Moon L4 point. Particular emphasis was placed on the study of underactuated control, in which fewer control inputs than the system's degrees of freedom are available. A linear LQR control scheme, an integral augmented sliding mode controller and a bang-bang controller were applied to the dynamic spacecraft system. The nonlinear controllers produced errors falling with tighter tolerances than the linear controllers in the perturbed environment. Performing similarly well as the underactuated thrusters system was the solar-sails-controlled spacecraft formation using a bang-bang controller. This shows that solar sails could be a viable propellantless technique for relative control. A linear control technique was able to bound errors to within a couple of hundred metres, using a hybrid propulsion system. Of the cases studied, only the fully-actuated thrusters-based system was able to explicitly track a circular trajectory, but had [Delta]V requirement of more than 100 times greater than that needed for tracking the natural, elliptical trajectory.

scholarly journals Flatness-Based Control of a Two Degrees-of-Freedom Platform With Pneumatic Artificial Muscles

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
David Bou Saba ◽  
Paolo Massioni ◽  
Eric Bideaux ◽  
Xavier Brun
Keyword(s):  
Degrees Of Freedom ◽  
Control Method ◽  
Sliding Mode ◽  
Feedforward Control ◽  
Volume Ratio ◽  
Open Loop ◽  
Control Technique ◽  
Artificial Muscles ◽  
Two Degrees Of Freedom ◽  
Pneumatic Artificial Muscles

Pneumatic artificial muscles (PAMs) are an interesting type of actuators as they provide high power-to-weight and power-to-volume ratio. However, their efficient use requires very accurate control methods taking into account their complex and nonlinear dynamics. This paper considers a two degrees-of-freedom platform whose attitude is determined by three pneumatic muscles controlled by servovalves. An overactuation is present as three muscles are controlled for only two degrees-of-freedom. The contribution of this work is twofold. First, whereas most of the literature approaches the control of systems of similar nature with sliding mode control, we show that the platform can be controlled with the flatness-based approach. This method is a nonlinear open-loop controller. In addition, this approach is model-based, and it can be applied thanks to the accurate models of the muscles, the platform and the servovalves, experimentally developed. In addition to the flatness-based controller, which is mainly a feedforward control, a proportional-integral (PI) controller is added in order to overcome the modeling errors and to improve the control robustness. Second, we solve the overactuation of the platform by an adequate choice for the range of the efforts applied by the muscles. In this paper, we recall the basics of this control technique and then show how it is applied to the proposed experimental platform. At the end of the paper, the proposed approach is compared to the most commonly used control method, and its effectiveness is shown by means of experimental results.

Low-thrust transfer to the Earth-Moon triangular libration point via horseshoe orbit

2020 ◽  
Vol 177 ◽  
pp. 111-121
Author(s):  
Xingji He ◽  
Yuying Liang ◽  
Ming Xu ◽  
Yaru Zheng
Keyword(s):  
Libration Point ◽  
Low Thrust ◽  
Triangular Libration Point ◽  
The Earth ◽  
Horseshoe Orbit

Dynamics and control of underactuated spacecraft formation reconfiguration in elliptic orbits

2017 ◽  
Vol 232 (12) ◽  
pp. 2214-2230 ◽  
Author(s):  
Xu Huang ◽  
Ye Yan ◽  
Yang Zhou
Keyword(s):  
Closed Loop ◽  
Sliding Mode ◽  
Linear Time ◽  
Control Technique ◽  
Spacecraft Formation ◽  
Formation Reconfiguration ◽  
Elliptic Orbits ◽  
Dynamics And Control ◽  
System States ◽  
The Stability

Feasibility of underactuated formation reconfiguration in elliptic orbits without radial or in-track thrust is investigated in this paper. For either underactuated case, by using a linear time-varying dynamical model of spacecraft formation, controllability and feasibility analyses are conducted, based on which the preconditions on reconfigurable formations are then derived. With the inherent coupling of system dynamics, the reduced-order sliding mode control technique is employed to design a closed-loop underactuated controller for either case. To ensure the stability of the closed-loop system, the conditions imposed on the controller parameters are derived, and the parameter adaptation laws are then solved analytically. Meanwhile, the explicit relationships between the steady accuracies of system states and the controller parameters are obtained via a Lyapunov-based approach. Numerical examples are simulated in a J2-perturbed environment to validate the theoretical analyses. The results indicate that by using the proposed control schemes, underactuated reconfiguration in elliptic orbits is still feasible even in the absence of radial or in-track thrust and in the presence of unmatched disturbances.

Position and Attitude Control of Deep-Space Spacecraft Formation Flying Via Virtual Structure and θ-D Technique

2007 ◽  
Vol 129 (5) ◽  
pp. 689-698 ◽  
Author(s):  
Ming Xin ◽  
S. N. Balakrishnan ◽  
H. J. Pernicka
Keyword(s):  
Attitude Control ◽  
Formation Flying ◽  
Libration Point ◽  
Suboptimal Control ◽  
Control Technique ◽  
Deep Space ◽  
Control Approach ◽  
Spacecraft Formation ◽  
Spacecraft Formation Flying ◽  
Highly Nonlinear

Control of deep-space spacecraft formation flying is investigated in this paper using the virtual structure approach and the θ-D suboptimal control technique. The circular restricted three-body problem with the Sun and the Earth as the two primaries is utilized as a framework for study and a two-satellite formation flying scheme is considered. The virtual structure is stationkept in a nominal orbit around the L2 libration point. A maneuver mode of formation flying is then considered. Each spacecraft is required to maneuver to a new position and the formation line of sight is required to rotate to a desired orientation to acquire new science targets. During the rotation, the formation needs to be maintained and each spacecraft’s attitude must align with the rotating formation orientation. The basic strategy is based on a “virtual structure” topology. A nonlinear model is developed that describes the relative formation dynamics. This highly nonlinear position and attitude control problem is solved by employing a recently developed nonlinear control approach, called the θ-D technique. This method is based on an approximate solution to the Hamilton-Jacobi-Bellman equation and yields a closed-form suboptimal feedback solution. The controller is designed such that the relative position error of the formation is maintained within 1cm accuracy.

Hybrid propulsion spacecraft formation control around the planetary displaced orbit

2021 ◽  
Vol 13 (10) ◽  
pp. 168781402110514
Author(s):  
Lei Zhao ◽  
Changqing Yuan ◽  
Qingbo Hao ◽  
Jingjiu He
Keyword(s):  
Formation Control ◽  
Dynamical Equation ◽  
Control Method ◽  
Sliding Mode ◽  
Solar Radiation Pressure ◽  
Coulomb Force ◽  
Sliding Mode Controller ◽  
Hybrid Propulsion ◽  
Spacecraft Formation ◽  
Displaced Orbit

This paper aims to investigate the feasibility of using the combination of solar radiation pressure and Coulomb force as a propellantless control method for spacecraft formation around the planetary displaced orbit. Firstly, the dynamical equation of spacecraft formation is derived and linearized. Based on the linearized dynamic model, an integral sliding mode controller (ISMC) is designed. Aimed to stabilize the spacecraft formation, the control method is proposed to adjust the product of the charge and the attitude angles of two spacecrafts. Finally, numerical simulations are conducted and the results show that the controller can make the formation achieve the desired configuration with favorable control performances.

scholarly journals Designing a Robust Nonlinear Dynamic Inversion Controller for Spacecraft Formation Flying

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Inseok Yang ◽  
Dongik Lee ◽  
Dong Seog Han
Keyword(s):  
Nonlinear Dynamic ◽  
High Speed ◽  
Formation Flying ◽  
Control Method ◽  
Sliding Mode ◽  
Control Technique ◽  
Dynamic Inversion ◽  
Spacecraft Formation ◽  
Spacecraft Formation Flying ◽  
Nonlinear Dynamic Inversion

The robust nonlinear dynamic inversion (RNDI) control technique is proposed to keep the relative position of spacecrafts while formation flying. The proposed RNDI control method is based on nonlinear dynamic inversion (NDI). NDI is nonlinear control method that replaces the original dynamics into the user-selected desired dynamics. Because NDI removes nonlinearities in the model by inverting the original dynamics directly, it also eliminates the need of designing suitable controllers for each equilibrium point; that is, NDI works as self-scheduled controller. Removing the original model also provides advantages of ease to satisfy the specific requirements by simply handling desired dynamics. Therefore, NDI is simple and has many similarities to classical control. In real applications, however, it is difficult to achieve perfect cancellation of the original dynamics due to uncertainties that lead to performance degradation and even make the system unstable. This paper proposes robustness assurance method for NDI. The proposed RNDI is designed by combining NDI and sliding mode control (SMC). SMC is inherently robust using high-speed switching inputs. This paper verifies similarities of NDI and SMC, firstly. And then RNDI control method is proposed. The performance of the proposed method is evaluated by simulations applied to spacecraft formation flying problem.

scholarly journals DESIGN AND CONSTRUCTION OF A NEW GENERATION OF ROBOTS

2019 ◽  
Vol 8 (2) ◽  
Author(s):  
Azam Salari Bajegani ◽  
Zahra Moeidi
Keyword(s):  
Physical Environment ◽  
Degrees Of Freedom ◽  
Sliding Mode ◽  
Dynamic Balance ◽  
Spherical Robot ◽  
Nonlinear Controller ◽  
Special Operations ◽  
The Earth ◽  
Non Linear System ◽  
New Generation

Each robot that is part of the physical environment, should be able to interact with humans. The dynamic balance on the robots such as the spherical robot cause demonstration Various interactive behaviors. Spherical robot is a stable and dynamic moving robot. It only features a spherical wheel that enables it to move in all directions, so there is not a problem to overturn the standing robots because its motion is in the form of rolling. The robot is able to easily move between the glades, sand and snow without clinging and can be used to build special operations teams in war zones or even carry explosives to the enemy's base. This research, is about the kinematics of the optimal motion of a spherical robot in a direct path with a simple mechanism and check spherical robot's control by the computer, and how wireless communication is communicated through the module. This robot is more capable than other robots made with different movement mechanisms, so that it can be easily moved and smooth in smooth, fluid, slippery, and angular surfaces, without the need for an attachment to move, It just moves easily with the gravity of the earth. The propulsion mechanism of this robot is a pendulum of two degrees of freedom propelled by two engines. This robot is a non-holonomic and non-linear system, so it needs a nonlinear controller like Sliding Mode Control (SMC).

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