NGC Aerospace Ltd.

Sherbrooke, Canada

NGC Aerospace Ltd.

Sherbrooke, Canada
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Hamel J.-F.,NGC Aerospace Ltd. | Neveu D.,NGC Aerospace Ltd. | Mercier G.,NGC Aerospace Ltd. | Alger M.,NGC Aerospace Ltd. | De Lafontaine J.,NGC Aerospace Ltd.
Proceedings of the International Astronautical Congress, IAC | Year: 2016

In order to reduce mission landing risk, many upcoming planetary exploration missions require the use of an autonomous Hazard Detection and Avoidance (HDA) system. HDA provides the capability to identify landing hazards such as roughness, slope and shadowed areas on the surface and to autonomously identify the safest landing site considering Lander manoeuvrability constraints. To achieve these objectives, HDA systems typically rely on a combination of measurements from camera and active Lidar sensors. Amongst the various Lidar technologies, scanning Lidar technologies show many advantages for missions which have tight mass and power constraints. However, a scanning Lidar takes time (typically several seconds) to scan a complete landing area. In order to mitigate the impact of the system on the overall propellant budget, it is not desirable to maintain static hovering conditions with the Lander during terrain assessment. The Lander keeps descending while the scanning and the processing takes place. The measurements provided to the HDA system are thus taken from different surface-relative conditions. The HDA system needs to do "motion compensation" to remove from the measurements the distortion caused by Lander motion to accurately reconstruct surface topography, a process which heavily relies on surface-relative navigation estimates. There is a strong interaction between HDA and navigation which occurs at four levels. Firstly, in order to maintain optimal surface coverage, the Lidar scan pattern is dynamically adapted to the estimated Lander motion. Secondly, the HDA reconstructs from relative motion compensation small-scale features on the surface to assess surface roughness and slope. Thirdly, hazards are referenced on the ground such that information from all sources can be combined and positioned with respect to the Lander trajectory estimate. Finally, the navigation estimates are used by the Lander to track the reference trajectory and reach the HDA-designated safe landing site. In most cases, the HDA is impacted not only by the absolute estimation error value itself, but also by the variation of this error over various timescales. This leads to unconventional performance requirements for the associated navigation system. The paper will thus discuss the interaction between the HDA and the navigation system at the various levels and will discuss the type of requirements this imposes on navigation. High-fidelity closed-loop simulation examples will demonstrate how HDA performance is affected by navigation errors in an autonomous Moon landing reference scenario and recommendations will be provided on how to mitigate or reduce their negative effects.

Hamel J.-F.,NGC Aerospace Ltd. | De Lafontaine J.,NGC Aerospace Ltd. | Lambert C.,Canadian Space Agency | Lambert C.,Control Group | And 2 more authors.
AIAA Guidance, Navigation, and Control Conference | Year: 2010

The paper describes an innovative method for the performance assessment of drag-based formation flying control techniques. The method aims at avoiding time-consuming long-duration closed-loop simulation campaigns with high fidelity simulators. The methodology quickly provides statistical insight into the formation control performance, thus supporting quick design iterations and systems engineering trade-off analyses. The paper reviews the drag-based guidance and control algorithm proposed for the JC2Sat mission, presents the methodology developed to assess performance, discusses the application of this methodology in the context of the JC2Sat mission and shows typical analysis results. Copyright © 2010 by NGC Aerospace Ltd.

Lambert C.,Canadian Space Agency | Kumar B.S.,Com Dev Inc. | Hamel J.-F.,NGC Aerospace Ltd | Ng A.,Canadian Space Agency
Acta Astronautica | Year: 2012

Formation flying using only differential drag forces is possible in low Earth orbit. The effectiveness of this technique is addressed for a practical satellite mission. Formation control algorithms typically rely on knowledge of the mean relative position between spacecrafts but this information is not readily available from sensor data and must be approximated using instantaneous sensor data for position and velocity. Several different approaches of obtaining the mean relative position are presented and compared. Two independent controllers are required to achieve precise formation control, one for secular formation maneuvers and another for periodic motion. The performance of each controller is examined using different methods for obtaining estimates of mean relative positions. © 2011 Elsevier Ltd.

Ulrich S.,Carleton University | Cote J.,NGC Aerospace Ltd.
61st International Astronautical Congress 2010, IAC 2010 | Year: 2010

The impact of unknown attitude perturbations on payload pointing performance of Earth-orbiting satellites is well known. The real-time three-axis estimation of those perturbations in order to improve the pointing accuracy is therefore critical, especially for high accuracy observation missions, such as Sun observation experiments. Current solutions to this problem consist in either increasing the bandwidth of the main attitude filter or to use an optimal estimation algorithm. Whereas the first solution reduces the stability margin of the overall guidance, navigation and control system, the second solution is computationally intense and is therefore not suitable for real-time space operations. In this paper, a novel solution to the in-flight estimation of perturbation torques problem is presented. The novel algorithm, NDO (nonlinear disturbance observer), is computationally efficient and is suitable for any Earth-orbiting spacecraft. The results presented in this paper show that the proposed strategy is a promising perturbation estimation technology even for small satellites equipped only with low-cost attitude sensors and without a gyroscope. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

De Vito D.,Polytechnic of Milan | Kron A.,NGC Aerospace Ltd | De Lafontaine J.,NGC Aerospace Ltd | Lovera M.,Polytechnic of Milan
Proceedings of the IEEE International Symposium on Computer-Aided Control System Design | Year: 2010

When controlling a Linear Parameter Varying (LPV) system, a LPV regulator is advisable, since it ensures better performance than a simple Linear Time Invariant actually does. In fact, real-time scheduling to the variations of the system allows the achievement of stability and performance requirements for a number of operating points. Within this setting, this paper discusses a Matlab toolbox achieving a self- scheduled LPV controller for an LPV model of the plant, robust in an H∞ sense in the face of uncertainties affecting the sys- tem's dynamics, through a Linear Matrix Inequality approach. The resulting algorithm alternatively implements synthesis and analysis steps, until the desired closed-loop performance level has been reached or no improvement between two successive steps arises. © 2010 IEEE.

Simard Bilodeau V.,Université de Sherbrooke | Clerc S.,Thales Alenia | Drai R.,European Space Agency | De Lafontaine J.,NGC Aerospace Ltd.
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2014

Major space agencies have an increasing interest in highly accurate (200 m) autonomous landing on the Moon. Inertial-only navigation is not compatible with this challenging requirement. The techniques currently investigated rely on vision-based navigation. A first approach consists in tracking features between sequences of images in order to measure the angular rate as well as the direction of the velocity vector of the spacecraft. A second approach aims at identifying image features using a georeferenced on-board database to determine the attitude and the position of the spacecraft. However, existing algorithms are computationally prohibitive and have a limited robustness to varying illumination conditions and surface characteristics. This paper presents the development of an innovative autonomous vision-based navigation system addressing these problems. Numerical simulations have shown that this system is capable of estimating the position and velocity of the vehicle with an accuracy better than 100 m and 0.1 m/s respectively. This work is the result of a successful collaboration between the Université de Sherbrooke, NGC Aerospace Ltd., Thales Alenia Space and the European Space Agency. The proposed system has been selected as the main navigation algorithm in three major research and development projects sponsored by European Space Agency and the Canadian Space Agency. © IFAC.

Sampaio U.P.,Visiona Tecnologia Espacial S.A. | St-Amour A.,NGC Aerospace Ltd. | de Lafontaine J.,NGC Aerospace Ltd.
IFAC-PapersOnLine | Year: 2016

Reaction wheels (RW) are common actuators for attitude control of three-axis stabilized satellites. By exchanging momentum with the spacecraft's body, a set of three non-planar RW is able to ensure the off-nadir fine pointing capabilities of agile high-resolution imaging satellites. Nonetheless, due to stiction, RW can cause considerable attitude jitter when their angular velocity is close to zero. This paper proposes a method to analyze the maximum off-nadir pointing angles that are allowable without causing zero-speed crossing for a spacecraft using only three active RW. In sequence, by applying this method for a sun-synchronous mission, it is shown that angular momentum management can be used to give the satellite an adequate roll slewing margin by placing the reaction wheel momentum set point in an appropriate position. This method can be applied to any mission that relies on three active RW and requires high pointing stability. © 2016

Cote J.,NGC Aerospace Ltd. | Kron A.,NGC Aerospace Ltd. | De Lafontaine J.,NGC Aerospace Ltd. | Naudet J.,QinetiQ | Santandrea S.,European Space Agency
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2011

The PRoject for On-Board Autonomy (PROBA) is an ESA technology- demonstration program aimed at the in-orbit validation of autonomy-enabling space technologies. Following the success of PROBA-1, the PROBA-2 spacecraft was launched on 2 November 2009 and continues the in-flight demonstration of on-board autonomy by performing a Sun observation mission as well as numerous flight experiments. This paper completes previously published articles by presenting the in-flight results of two innovative autonomous GNC functions: (1) Star Tracker Earth Exclusion Angle Prediction for Earth avoidance and (2) Large-Angle Rotation around Fixed Axis. Finally, flight results of the Attitude and Orbit Control System (AOCS) nominal operation using these innovative GNC functions will be presented. © 2011 IFAC.

Kron A.,NGC Aerospace Ltd. | St-Amour A.,NGC Aerospace Ltd. | De Lafontaine J.,NGC Aerospace Ltd.
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2014

Reaction Wheels (RW) are common actuators for three-axis stabilized satellites. This paper deals with the management of a RW assembly where four or more skewed RW are used simultaneously. Four-wheel control is commonly used on spacecraft. This paper contributes to this field by providing an efficient algorithm for attitude control torque distribution with RW angular rate constraint management and by providing the rationales that guide the tuning of this algorithm. Moreover, it defines an algorithm for the angular momentum management of this reaction wheels assembly. Eventually, as proof of concept, it applies these algorithms to a realistic scenario of the PROBA-3 mission using a high fidelity simulator. Results demonstrate that the suggested algorithms are operational and efficient. They can be used and adapted to several types of missions. © IFAC.

Bilodeau V.S.,NGC Aerospace Ltd. | Hamel J.-F.,NGC Aerospace Ltd. | Iles P.,Neptec Design Group
Proceedings of the International Astronautical Congress, IAC | Year: 2013

Accurate relative localisation is a critical aspect for future rover planetary exploration missions. In previous work, NGC Aerospace and Neptec Design Group have developed, implemented and tested a generic and robust vision-based pose estimation system for the lunar exploration rover prototype "Artemis". This activity took place in the context of a lunar rover design study sponsored by the Canadian Space Agency. This rover prototype, initially designed for Earth-bound demonstration, is now being considered as the vehicle to carry and operate the NASA RESOLVE payload for an In-Situ Resource Utilisation (ISRU) experiment mission at the South Pole of the Moon. This paper describes how the Artemis relative localisation system design can be adapted to the baseline RESOLVE mission, taking into account the constraints of a Moon South Pole exploration mission, and what level of performance is expected. © 2013 NGC Aerospace Ltd. All rights reserved.

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