Modeling and Attitude Control of Satellites in Elliptical Orbits

The attitude determination and control system (ADCS) for spacecraft is responsible for determining its orientation using sensor measurements and then applying actuation forces to change the orientation. This chapter details the different components required for a complete attitude determination and control system for satellites moving in elliptical orbits. Specifically, the chapter details the orbital mechanics; perturbations; controller design; actuation methods such as thrusters, reaction wheels, and magnetic torquers; actuation modulation methods such as bang-bang, pulse-width modulation, and pulse-width pulse-frequency; as well as attitude determination using vector measurements combined with mathematical models. In sum, the work describes in a tutorial manner how to put everything together to enable the design of a complete satellite simulator

Preliminary Results on Waypoint Tracking for Spacecraft with Actuator Constraints

This paper presents preliminary results on how to perform waypoint tracking with spacecraft with actuator constraints. It considers a simplified spacecraft model and can be considered a deep space model, and shows how to perform waypoint tracking with only one main thruster together with full attitude control. As the spacecraft reaches close to the waypoint during a deceleration phase that makes the speed go towards zero, reaction control thrusters are used to make the remaining velocity error go to zero achieving the control objective

Condition Monitoring Technologies for Synthetic Fiber Ropes - a Review

This paper presents a review of different condition monitoring technologies for fiber ropes. Specifically, it presents an overview of the articles and patents on the subject, ranging from the early 70’s up until today with the state of the art. Experimental results are also included and discussed in a conditionmonitoring context,where failuremechanisms and changes in physical parameters give improved insight into the degradation process of fiber ropes. From this review, it is found that automatic width measurement has received surprisingly little attention, and might be a future direction for the development of a continuous condition monitoring system for synthetic fiber ropes

Condition Monitoring Technologies for Steel Wire Ropes – A Review

In this research, we review condition-monitoring technologies for offshore steel wire ropes (SWR). Such ropes are used within several offshore applications including cranes for load handling such as subsea construction at depths up to 3-4000 meters, drilling lines, marine riser tensioner lines and anchor lines. For mooring, there is a clear tendency for using fiber ropes. Especially for heavy-lift cranes and subsea deployment, winches with strong ropes of up to 180 mm in diameter may be required, which has a considerable cost per rope, especially for large water depths. Today’s practice is to discard the rope after a predetermined number of uses due to fatigue from bending over sheaves with a large safety factor, especially for systems regulated by active heave compensation (AHC). Other sources of degradation are abrasion, fretting, corrosion and extreme forces, and are typically accelerated due to undersized or poorly maintained sheaves, groove type, lack of lubrication and excessive load. Non-destructive testing techniques for SWR have been developed over a period of 100 years. Most notably are the magnetic leakage techniques (electromagnetic methods), which are widely used within several industries such as mining and construction. The content reviewed in this research is primarily the developments the last five years within the topics of electromagnetic method, acoustic emissions (AE), ultrasound, X- and γ-rays, fiber optics, optical and thermal vision and current signature analysis. Each technique is thoroughly presented and discussed for the application of subsea construction. Assessments include ability to detect localized flaws (i.e. broken wire) both internally and externally, estimated loss of metallic cross sectional area, robustness with respect to the rough offshore environment, ability to evaluate both rope and end fittings, and ability to work during operation

Attitude Determination and Control System for Satellites in Elliptical Orbits - a Complete Solution

This paper presents a complete solution to the problem of attitude determination and control for satellites in elliptical orbits. Specifically, it shows how to create the orbital mechanics, account for perturbing gravity torques, create a nonlinear PD+ attitude controller, map the control signal to desired thrust firings, implement magnetic field and Sun vector models, and how to implement a Madgwick filter for attitude determination based on vector measurement

Autonomous Inspection of the International Space Station

This paper presents a solution to autonomous inspection of the international space station using a rigid spacecraft. Specifically, the paper presents the orbital mechanics, formation dynamics as well as rotational dynamics required to control the spacecraft relative to the space station, and then presents two PD+ controllers enabling a spacecraft to track a series of waypoints while pointing a sensor towards the structure of the space station. Simulations validate the results

Nonlinear Control of Fixed-Wing Unmanned Aerial Vehicles

PhD i teknisk kybernetikkPhD in Engineering Cybernetic