Research Interests:
Research Interests:
This article focuses on a spacecraft trajectory planning algorithm that allows observation of multiple site locations on the asteroid surface, while avoiding any collision with debris objects trapped in the asteroid’s gravity field.... more
This article focuses on a spacecraft trajectory planning algorithm that allows observation of multiple site locations on the asteroid surface, while avoiding any collision with debris objects trapped in the asteroid’s gravity field. Asteroids provide a challenging target for satellite based visual coverage missions, since they are partially illuminated, rotating, irregular shaped celestial bodies with a low but also irregular gravity field. For addressing this problem, an optimization approach for visual coverage is proposed with an objective to determine the sequence of the imaging site locations and the associated safe and fuel efficient trajectories, while considering rotational dynamics of the asteroid, changing illumination condition for each site, irregular gravity constraints of the asteroid and the safe separation distance from the moving debris object. Numerical simulations are performed to demonstrate the ability of the trajectory planner to ensure successful optimal coverage of all the desired asteroid site locations. letterpaper, 10 pt.
Research Interests:
Research Interests:
Research Interests:
In this article, an optimization based spacecraft trajectory planner for asteroid proximity missions is presented. In asteroid missions, it is of a specific interest to determine the surface and material properties of the target asteroid... more
In this article, an optimization based spacecraft trajectory planner for asteroid proximity missions is presented. In asteroid missions, it is of a specific interest to determine the surface and material properties of the target asteroid by obtaining high-resolution measurements from multiple sites over the asteroid surface. During this mission, an important problem to solve is the trajectory planning for the spacecraft, that results into a visual coverage problem for the asteroid surface. However, asteroids provide a challenging target for such missions since they are partially illuminated, rotating, irregular shaped bodies with a low (micro) but irregular gravity field. For addressing this challenging problem, this article will propose a novel optimization approach for the visual coverage of an asteroid. Thus, the proposed trajectory planner's objective is to determine the sequence of the areas to cover and the associated trajectories to achieve this coverage, while considering the motion of the spacecraft, the rotation dynamics of the asteroid, the illumination to each asteroid site and the irregular gravity constraints of the asteroid. The efficacy of the proposed optimal trajectory planner is evaluated through multiple simulation results, where it demonstrates successful optimal coverage of all the desired asteroid areas.
Research Interests:
Research Interests:
This article proposes a novel two-staged trajectory planning algorithm toward the cooperative visual coverage of multiple asteroid sites with the utilization of multiple spacecraft. The objective of the novel established planning scheme... more
This article proposes a novel two-staged trajectory planning algorithm toward the cooperative visual coverage of multiple asteroid sites with the utilization of multiple spacecraft. The objective of the novel established planning scheme is to determine an observation tour for each spacecraft and the associated fuel optimal trajectories, such that each site of interest is observed only once during the entire mission. The completion of the observation task of an asteroid site is limited to the observation time window, referred as the period for which a site is illuminated by the Sun. The proposed planning algorithm divides the overall multi-site coverage problem into a nonlinear and integer optimization problem as: (i) a single target optimization and (ii) a multi-target multiple spacecraft optimal sequencing problem. The first part aims to generate fuel optimal trajectories, for all the initial-final imaging site location pairs. In the second part, the problem of distributing the observation task, among the fleet of spacecraft, is addressed by designing a feasible tour to observe a subset of the desired asteroid sites, for each spacecraft, while considering their individual fuel capacity. The efficacy of the proposed algorithm is evaluated in multiple simulation scenarios and while considering different asteroids. GRAPHICAL ABSTRACT
Research Interests:
Research Interests:
In this letter, a floating robotic emulation platform is presented with an autonomous maneuverability for a virtual demonstration of a satellite motion. Such a robotic platform design is characterized by its friction-less, levitating, yet... more
In this letter, a floating robotic emulation platform is presented with an autonomous maneuverability for a virtual demonstration of a satellite motion. Such a robotic platform design is characterized by its friction-less, levitating, yet planar motion over a hyper-smooth surface. The design of the robotic platform, integrated with the sensor and actuator units, is briefly described, including the related component specification along with the mathematical model, describing its dynamic motion. Additionally, the article establishes a nonlinear optimal control architecture consisting of a unified model predictive approach for the overall manoeuvre tracking. The efficacy of the proposed modeling and control scheme is demonstrated in multiple experimental studies, where it is depicted that the proposed controller has the potential to address a precise point-to-point manoeuvre with terminal objectives, as well as an excellent path following capability. The proposed design is validated with extensive experimental studies, and it is supported with related results.
Research Interests:
Research Interests: Mathematics and Elsevier
This article will outline the relative orbit control, including guidance and control tasks developed for the PRISMA technology in-orbit formation flying testbed mission. The focus is on real-time i ...
Research Interests:
An open source simulator for a global navigation satellite system (GNSS) based onboard navigation of satellites is presented. The structure and building blocks of the simulator, as well as the data ...
Research Interests:
The Prisma mission is divided into four phases; the nominal mission, the extended mission, the external parties’ mission and the final mission. The milestones switching from one phase to the next are unique occasions that have brought the... more
The Prisma mission is divided into four phases; the nominal mission, the extended mission, the external parties’ mission and the final mission. The milestones switching from one phase to the next are unique occasions that have brought the mission forward, whereof some were planned before the launch of the satellites and some were adaptations along with the development of the mission timeline. In particular, the current execution of the final phase contains Mango alone operation, which means Mango has abandoned Tango and has started a journey on its own for transfer to and rendezvous with a still to be decided space debris object. The rendezvous will be performed based upon TLE and angular measurements from the on-board camera and after the rendezvous a visual inspection and characterization of the object will be performed, utilizing the on board high resolution PR camera. This paper explains these milestones and the turn of events leading up to the events that were not planned. It a...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
this paper, a different method for frequency response estimation is suggested. The method utilizes recently proposed wavelet based denoising schemes combined with traditional smoothing techniques. The wavelet transform is applied in the... more
this paper, a different method for frequency response estimation is suggested. The method utilizes recently proposed wavelet based denoising schemes combined with traditional smoothing techniques. The wavelet transform is applied in the frequency domain in order to provide a suitable frequency window. Tested through simulations, this approach provides an alternative when traditional methods fail.
Research Interests:
The PRISMA in-orbit testbed was launched on June 15, 2010 to demonstrate strategies and technologies for formation flying and rendezvous. OHB Sweden (OHB-SE) is the prime contractor for the project which is funded by the Swedish National... more
The PRISMA in-orbit testbed was launched on June 15, 2010 to demonstrate strategies and technologies for formation flying and rendezvous. OHB Sweden (OHB-SE) is the prime contractor for the project which is funded by the Swedish National Space Board with additional support from the German Aerospace Center (DLR), the French National Space Center (CNES), and the Technical University of Denmark (DTU). In August 2011, PRISMA completed its nominal mission and during the fall of 2011, several additional activities have been performed under a mission extension program. The mission qualifies a series of sensor and actuator systems including navigation using GPS, Vision Based and RF technology as well as a propulsion system based on environmentally friendly propellant technology. The mission also includes a series of GNC experiments using this equipment in closed loop. Separate experiments are implemented by OHB-SE, DLR, and CNES and the paper provides an overview and conclusions from the no...
Abstract The PRISMA in-orbit test-bed was launched on June 15, 2010. The mission will demonstrate strategies and technologies for formation flying and rendezvous. The Swedish Space Corporation (SSC) is the prime contractor for the project... more
Abstract The PRISMA in-orbit test-bed was launched on June 15, 2010. The mission will demonstrate strategies and technologies for formation flying and rendezvous. The Swedish Space Corporation (SSC) is the prime contractor for the project which is funded by the ...
Research Interests:
Research Interests:
PRISMA is an ongoing satellite project comprising two satellites. The project constitutes an in-orbit test bed for Guidance, Navigation and Control (GNC) algorithms and sensors for advanced closed-loop formation flying and rendezvous. The... more
PRISMA is an ongoing satellite project comprising two satellites. The project constitutes an in-orbit test bed for Guidance, Navigation and Control (GNC) algorithms and sensors for advanced closed-loop formation flying and rendezvous. The satellites will be launched in a low earth orbit and carry out a series of maneuvering experiments and sensor experiments during a mission time of 8-10 months. Autonomous formation flying in decimeter precision will be demonstrated using relative GPS and Formation Flying RF metrology instruments. Vision based methods using a modified star camera will demonstrate autonomous homing and rendezvous from hundreds of kilometers down to close proximity. Proximity operations based on GPS or optical information shall be demonstrated all the way down to almost physical contact. A new environmentally friendly, non-toxic chemical propulsion system as well as a new MEMS microthruster system will be flight demonstrated.
Research Interests:
Research Interests:
The frequency function of a linear dynamical system can be estimated using spectral estimation techniques. Traditionally, this is done by smoothing in the frequency domain or windowing in the lag domain. These methods are successful in... more
The frequency function of a linear dynamical system can be estimated using spectral estimation techniques. Traditionally, this is done by smoothing in the frequency domain or windowing in the lag domain. These methods are successful in most cases but sometimes they yield estimates that suffer from poor resolution. Typically, this happens when fine details are estimated. In this paper an alternative method is proposed. The method combines traditional windowing with results in adaptive time-frequency analysis. In simulations concerning systems which are difficult for the traditional approach, this method gives better better estimates of the frequency function
Research Interests:
ABSTRACT This paper deals with the problem of structure determination for generalized orthonormal basis models used in system identification. The model structure is parametrized by a pre-specified set of poles. Given this structure and... more
ABSTRACT This paper deals with the problem of structure determination for generalized orthonormal basis models used in system identification. The model structure is parametrized by a pre-specified set of poles. Given this structure and experimental data a model can be estimated using linear regression techniques. Since the variance of the estimated model increases with the number of estimated parameters, the objective is to find structures that are as compact/parsimonious as possible. A natural approach would be to estimate the poles, but this leads to nonlinear optimization with possible local minima. In this paper, a best basis algorithm is derived for the generalized orthonormal rational bases. Combined with linear regression and thresholding this leads to compact transfer function representations
Research Interests: Mechanical Engineering, Applied Mathematics, System Identification, Control Engineering, Statistical Analysis, and 14 moreAutomatic Control, Convergence, Parameter estimation, State Space, Thresholding, Transfer Function, Local minima, Context Modeling, Linear Regression, Experimental Data, Structure Determination, Transfer Functions, Electrical And Electronic Engineering, and Nonlinear Optimization
SMART-1 was launched in September 2003 and impacted the Moon 3 years later. It was the first of ESA's Small Missions for Advanced Research in Technology, with the main goal of testing electric propulsion.... more
SMART-1 was launched in September 2003 and impacted the Moon 3 years later. It was the first of ESA's Small Missions for Advanced Research in Technology, with the main goal of testing electric propulsion. Following a spectacular navigation strategy, the craft reached the Moon, where its orbit was optimised for scientific observations. The instruments provided data throughout the mission, interrupted
Research Interests:
. This contribution deals with the problem of structure determination for generalizedorthonormal basis models used in system identification. The model structure is parameterized by apre-specified set of poles. Given this structure and... more
. This contribution deals with the problem of structure determination for generalizedorthonormal basis models used in system identification. The model structure is parameterized by apre-specified set of poles. Given this structure and experimental data a model can be estimated usinglinear regression techniques. Since the variance of the estimated model increases with the numberof estimated parameters, the objective is to find
Research Interests:
This paper deals with the problem of enhancement of speech signals in slowly varying background noise. The method suggested uses the wavelet packet transform together with a simple statistical model of the noise. As in spectral... more
This paper deals with the problem of enhancement of speech signals in slowly varying background noise. The method suggested uses the wavelet packet transform together with a simple statistical model of the noise. As in spectral subtraction, information about the background is collected during non-speech intervals. The signal estimate is obtained with spectral subtraction in the time-frequency domain and a rule for choosing the most favorable time-frequency decomposition is suggested. The method is demonstrated with a real-data example
Research Interests:
... 9b. Furthermore it holds that contact is achieved again when|#;,| a. An exact solution of the trajectory of 9b is now given Page 28. 6 Mattias Nordin, Per Bodin and Per-Olof Gutman by solving for 9b as a one state model. Usinq ...
Research Interests:
PRISMA is an ongoing satellite project comprising two satellites. The project constitutes an in-orbit test bed for Guidance, Navigation and Control (GNC) algorithms and sensors for advanced closed-loop formation flying and rendezvous. The... more
PRISMA is an ongoing satellite project comprising two satellites. The project constitutes an in-orbit test bed for Guidance, Navigation and Control (GNC) algorithms and sensors for advanced closed-loop formation flying and rendezvous. The satellites will be launched in a low earth orbit and carry out a series of maneuvering experiments and sensor experiments during a mission time of 8-10 months. Autonomous formation flying in decimeter precision will be demonstrated using relative GPS and Formation Flying RF metrology instruments. Vision based methods using a modified star camera will demonstrate autonomous homing and rendezvous from hundreds of kilometers down to close proximity. Proximity operations based on GPS or optical information shall be demonstrated all the way down to almost physical contact. A new environmentally friendly, non-toxic chemical propulsion system as well as a new MEMS microthruster system will be flight demonstrated.
Research Interests:
This paper presents flight results and lessons learned from the Autonomous Formation Flying (AFF) experimental and routine phase conducted by SSC. The paper will cover the design, flight results, operational aspects as well as lessons... more
This paper presents flight results and lessons learned from the Autonomous Formation Flying (AFF) experimental and routine phase conducted by SSC. The paper will cover the design, flight results, operational aspects as well as lessons learned. Within PRISMA there is a number of different experimental guidance and control modules, AFF is one of them. However, AFF is the only module that after the experimental phase has been used on routine basis for an extended period of time. AFF has, as of the deadline for this article, accumulated over 4 months of closed loop cooperative satellite formation flying time. There were about 20 days for dedicated AFF experiments, while the rest has been operational routine formation flying, where AFF has been used in closed loop to support other open loop guidance and navigation experiments, maintaining and reconfiguring the formation between other experiments as well as over weekends and holidays. For this, over 110 different formation reconfiguration...
SMART-1 was launched in September 2003 and impacted the Moon 3 years later. It was the first of ESA's Small Missions for Advanced Research in Technology, with the main goal of testing electric propulsion. Following a spectacular... more
SMART-1 was launched in September 2003 and impacted the Moon 3 years later. It was the first of ESA's Small Missions for Advanced Research in Technology, with the main goal of testing electric propulsion. Following a spectacular navigation strategy, the craft reached the Moon, where its orbit was optimised for scientific observations. The instruments provided data throughout the mission, interrupted
Research Interests:
... by SSC in PRISMA is a Spacecraft Local Orbital (SLO) frame and is defined in (Yamanaka,Ankersen 2002). ... Functions Attitude Guidance Functions Attitude Control Functions Orbit Navigation Functions Orbit Guidance Functions Orbit... more
... by SSC in PRISMA is a Spacecraft Local Orbital (SLO) frame and is defined in (Yamanaka,Ankersen 2002). ... Functions Attitude Guidance Functions Attitude Control Functions Orbit Navigation Functions Orbit Guidance Functions Orbit Control Functions Solar Magnetic Attftude ...
Research Interests:
ABSTRACT This contribution deals with the problem of structure determination for generalized orthonormal basis models used in system identification. The model structure is parameterized by a pre-specified set of poles. Given this... more
ABSTRACT This contribution deals with the problem of structure determination for generalized orthonormal basis models used in system identification. The model structure is parameterized by a pre-specified set of poles. Given this structure and experimental data a model can be estimated using linear regression techniques. Since the variance of the estimated model increases with the number of estimated parameters, the objective is to find structures that are as compact/parsimonious as possible. A natural approach would be to estimate the poles, but this leads to nonlinear optimization with possible local minima. In this paper, a best basis algorithm is derived for the generalized orthonormal rational bases. Combined with linear regression and thresholding this leads to compact transfer function representations. 1 Introduction Modeling and identification with orthogonal basis functions has recently received considerable attention, see e.g. [1, 2, 3, 4, 5, 6]. The main idea is to use transfer fun...