Guidance, Navigation And Control Research Articles

Physical Modeling and Simulation of Reusable Rockets for GNC Verification and Validation

Reusable rockets must rely on well-designed Guidance, Navigation and Control (GNC) algorithms. Because they are tested and verified in closed-loop, high-fidelity simulators, emphasizing the strategy to achieve such advanced models is of paramount importance. A wide spectrum of complex dynamic behaviors and their cross-couplings must be captured to achieve sufficiently representative simulations, hence a better assessment of the GNC performance and robustness. This paper focuses on of the main aspects related to the physical (acausal) modeling of reusable rockets, and the integration of these models into a suitable simulation framework oriented towards GNC Validation and Verification (V&V). Firstly, the modeling challenges and the need for physical multibody models are explained. Then, the Vertical Landing Vehicles Library (VLVLib), a Modelica-based library for the physical modeling and simulation of reusable rocket dynamics, is introduced. The VLVLib is built on specific principles that enable quick adaptations to vehicle changes and the introduction of new features during the design process, thereby enhancing project efficiency and reducing costs. Throughout the paper, we explain how these features allow for the rapid development of complex vehicle simulation models by adjusting the selected dynamic effects or changing their fidelity levels. Since the GNC algorithms are normally tested in Simulink®, we show how simulation models with a desired fidelity level can be developed, embedded and simulated within the Simulink® environment. Secondly, this work details the modeling aspects of four relevant vehicle dynamics: propellant sloshing, Thrust Vector Control (TVC), landing legs deployment and touchdown. The CALLISTO reusable rocket is taken as study case: representative simulation results are shown and analyzed to highlight the impact of the higher-fidelity models in comparison with a rigid-body model assumption.

A multi-platform Guidance, Navigation and Control system for the autosub family of Autonomous Underwater Vehicles

Over the last decade, there has been a proliferation of marine robots such as Unmanned Surface Vehicles (USVs), Autonomous Underwater Vehicles (AUVs) and underwater gliders. The variety of vehicles’ capabilities and styles has led to numerous strategies to address the Guidance, Navigation and Control (GNC) tasks. In particular, a recent trend in the advancements of GNC systems is to develop modular, multi-platform solutions. This paper illustrates the approach followed in the development of the GNC system for the different types of AUV of the Autosub family. The presented system is decomposed into several interconnected components, each implemented as a standalone software module. Each component is highly-reconfigurable and easily extensible, and the interactions between the modules rely on generic-purpose interfaces. Such a design enables the execution of a broad range of autonomous missions, as well as the integration and deployment of the system on marine platforms with very diverse characteristics, not limited to the vehicles of the Autosub class. Experimental results obtained in real-time during in water campaigns are provided to demonstrate the effectiveness of the proposed system and its versatility on a wide range of platforms and missions.

Rendezvous in cislunar halo orbits: Hardware-in-the-loop simulation with coupled orbit and attitude dynamics

Space missions to Near Rectilinear Halo Orbits (NRHOs) in the Earth–Moon system are upcoming. A rendezvous technique in cislunar space is proposed in this investigation, one that leverages coupled orbit and attitude dynamics in the Circular Restricted Three-body Problem (CR3BP). An autonomous Guidance, Navigation and Control (GNC) technique is demonstrated in which a chaser spacecraft approaches a target spacecraft in a sample southern 9:2 synodic-resonant L2 NRHO, one that currently serves as the baseline for NASA’s Gateway. A two-layer guidance and control approach is contemplated. First, a nonlinear optimal controller identifies an appropriate baseline rendezvous path for guidance, both in position and orientation. As the spacecraft progresses along the pre-computed baseline path, navigation is performed through optical sensors that measure the relative pose of the chaser relative to the target. A Kalman filter processes these observations and offers state estimates. A linear controller compensates for any deviations identified from the predetermined rendezvous path. The efficacy of the GNC technique is tested by considering a complex scenario in which the rendezvous operation is conducted with an uncontrolled tumbling target. Hardware-in-the-loop laboratory experiments are conducted as a proof-of-concept to validate the guidance algorithm, with observations supplemented by optical navigation techniques.

Immersive virtual simulation system design for the guidance, navigation and control of unmanned surface vehicles

The simulation of Guidance, Navigation and Control (GNC) is a key issue to provide an economical way to test and improve the various algorithms in the development and research of Unmanned Surface Vehicle (USV). However, most of the existing simulation systems are offline with limited visualization scene, and unable to interact with real sensors mounted on the USV, thus failing to display the immersive and real-time motion of USV for researchers. In this paper, a virtual simulation system is developed, which provides an open and online platform for the immersive and visualized GNC simulation of USVs. Two modes are designed with one to provide a virtual simulation with simulated sensors and USVs, while another to provide a visualization of real GNC tasks driven by the in-situ data. To accomplish these two modes, the lower computer works to interact with simulated or real sensors, and calculate the mathematical model of USVs, while the host computer works to obtain the data from lower computer, and implement the GNC of USVs, which is finally and immersively displayed in the virtual scene. Moreover, an open interface is designed in this system that allows the researchers to test their own algorithms in the GNC of USVs. The sliding mode control (SMC) controller, hybrid navigation algorithm as well as LOS-based formation navigation algorithm are proposed to serve as two case studies in the single-USV and multi-USV scenarios. The results verify the effectiveness of the proposed virtual simulation system in the immersive and visualized simulation of GNC for USVs.

Design, realization and characterization of a free-floating platform for flexible satellite control experiments

Experimental verification of numerical models is a key aspect in all scientific and technological disciplines, yet space systems can be particularly hard to test on ground: in fact, a terrestrial mock-up replicating the orbital dynamics should be in a microgravity environment. One of the most common approaches to (at least partially) realize this condition, consists in free-floating systems, in which the friction between an experimental platform and the working surface is almost completely removed. The vertical axis is still subject to gravity, and only 3° of freedom (two horizontal translations and one rotation about the vertical axis) are available to replicate the orbital behavior.Our research group had been developing since 2012 a free-floating platform named PINOCCHIO (Platform Integrating Navigation and Orbital Control Capabilities Hosting Intelligent Onboard). The need to investigate with higher accuracy the attitude control problem for flexible satellites called for the design, realization and characterization of a new platform with enhanced performance.This paper describes the main components of the system, including the pressure air system, the navigation and communication system, the Guidance, Navigation and Control (GNC) architecture and relevant hardware. The attention is specifically on the characterization of the subsystems' performance. The physical (mass, moment of inertia), control (thrusters’ torque and force) and Inertial Measurement Unit (IMU) characteristics are experimentally measured with the associated uncertainty level. The accuracy of the external metrology system in static and dynamic conditions is also characterized, obtaining a 100 μm-level resolution for external measurement of rigid and elastic displacements; this information is fundamental for performing tests of fine pointing control algorithms for flexible and agile satellites.The proposed characterization methodology and associated results could be of interest for university and industry laboratories intended to develop new free-floating platforms.

Visual based GNC system from prototype to flight software

Juventas is a 6U CubeSat which is part of HERA planetary defense mission and takes advantage of an innovative visual based guidance, navigation and control (GNC) system to perform autonomous navigation in the proximity of the Didymain system. The GNC system is designed to ensure safe navigation in the harsh and unpredictable environment of deep space and finally to take more risks by landing on the surface of Dimorphos. To achieve a qualitative software (SW) product, a dedicated procedure of SW lifecycle is developed by starting with GNC and image processing design, which concludes with the final embedded system that will perform the visual navigation task. A Design, Development, Verification and Validation (DDVV) approach is developed to achieve the flight software: model in the loop (MIL), auto-coding, software in the loop (SIL), processor in the loop (PIL) and finally hardware in the loop (HIL). The DDVV is developed by having as guideline the ECSS standards for SW. The flight software reaches maturity by performing dynamic/static code analysis and code coverage. To ensure an optimal process, a waterfall life-cycle is considered, where dedicated MIL, SIL, PIL and HIL test benches are developed to fully support the activity and to reduce to minimum the development costs.[7]

Advanced GNC-oriented modeling and simulation of Vertical Landing vehicles with fuel slosh dynamics

This paper introduces a flexible framework to enable high-fidelity simulations of the fuel slosh dynamics for verification of the Guidance, Navigation and Control (GNC) algorithms. The sloshing phenomenon must be tackled during the control system design phase and the GNC software run and validated within appropriate simulation frameworks. Equivalent mechanical models can well approximate sloshing under specific assumptions, allowing the derivation of the multibody vehicle’s equations of motion; however, while suitable for analysis and control synthesis purposes, this approach presents several limitations for implementation as a simulation model. In this work, the multibody plant embedding slosh dynamics is modeled by means of the DLR’s Vertical Landing Vehicles Library (VLVLib) written using the object-oriented Modelica modeling language. The advantages of using Modelica are explored throughout the paper. Given that control synthesis, analyses and simulation campaigns are usually performed in the Matlab/Simulink environment, a core point of the proposed solution is to achieve a good synergy within the latter and the Modelica plant model with the least readaptation burden for the developer. The strategies to achieve a full integration and verification tool chain are illustrated. The potential of this approach is demonstrated via two different test cases: a lunar landing scenario of the ALINA spacecraft developed by PTS, and CALLISTO reusable rocket demonstrator.

A Review of Various Control Algorithms Used for a Solid Rocket Motor to Achieve Vertical Takeoff and Vertical Landing

The goal of this paper is to provide a critical review of different guidance, navigation and control (GNC) schemes that can achieve vertical take-off/ vertical landing (VTVL), which is where a rocket takes off and lands propulsively, using a model rocket. Reusable launch vehicles (RLVs), many of which use VTVL, could lower costs, decrease waste and allow for more scientific research extraterrestrially. Existing research typically only presents an attitude controller, which is insufficient for VTVL, whilst our main contribution is presenting GNC schemes for VTVL and comparing them to determine the best. The schemes are simulated with varying parameters to test the robustness and to evaluate their performance, with linear control and non-linear navigation and guidance perform the ing best.

Kinetic impactor for a short warning asteroid deflection

In this paper, GMV as a major AOCS (Attitude Orbit Control System)/GNC (Guidance, Navigation and Control) system provider presents its work on the development of a GNC system for a Kinetic Impact mission. Asteroid impacts on Earth are a known source of extinction and played an important role in the evolution of life on Earth. This comes as no surprise given the high number of objects orbiting in Earth’s vicinity—asteroid impacts become a question of “when” rather than “if”.This comes as no surprise given the high number of objects orbiting in Earth’s vicinity—asteroid impacts become a question of “when” rather than “if”. Under this motivation, thousands of potentially hazardous asteroids (PHAs) are monitored around the globe and naturally the question on the next step rose: What can we do when an incoming asteroid is identified as being on collision course with Earth? This is the motivation behind the field of Planetary Defence. Several mitigation strategies are being studied, but most of these have technology readiness levels still far off from the required. The one that comes closest is the kinetic impactor concept, which is the focus of this work. The concept is simple from a theoretical standpoint - a spacecraft (impactor) is sent into a collision course against the hazard NEO transferring enough momentum through kinetic energy to slightly change the NEO’s trajectory and causes it to miss the Earth.The main component of kinetic impactors is the GNC, due to the necessity of a fully autonomous system. The major elements are the camera and the guidance, since they will allow detecting the target and modifying its trajectory to have a successful impact, respectively. This study includes the implementation of the required algorithms as well as an analysis of their performance in the impact scenario.The main variables that control the simulations have been examined in order to determine the design limits. The sensitivity analysis illustrates that the errors introduced in the model were chosen conservatively, inasmuch as the impact could be reached introducing higher uncertainties and errors in the systems considered. In general, even with the not excessively complex algorithms employed, the performance of the GNC is good. This study opens the door for the development of a kinetic impactor mission.

RETALT: review of technologies and overview of design changes

RETALT (RETro propulsion Assisted Landing Technologies) is a project funded in the frame of the European Union Horizon 2020 program, that is studying critical key technologies for the vertical landing of launcher configurations with the aid of retro propulsion. In particular Aerodynamics, Aerothermodynamics, Flight Dynamics and Guidance Navigation and Control (GNC), Structures, Mechanisms, Thrust Vector Control and Thermal Protection Systems are investigated in detail in the project. This paper provides an overview of the technological achievements in these different technological areas, with emphasis on the interaction between them. Design changes made to the RETALT1 configuration are laid out in detail. The novel approach of using interstage segments as aerodynamic control surfaces proved to be challenging from the aerodynamics, flight dynamics, mechanical and structural points of view. For this reason, planar fins were introduced as aerodynamic control surfaces in the new base line configuration for RETALT1. The paper concludes with a summary of future steps to be made in the RETALT project to reach the targeted Technology Readiness Level (TRL) of the different key technologies.

A Parallel Mapping and Planning Strategy for Micro Aerial Vehicle

Autonomous flight is a fundamental problem for various applications of micro aerial vehicles (MAVs). Thanks to the development of Guidance, Navigation and Control (GNC) technologies, the research on this problem is also becoming mature. However, safe flight in unknown, cluttered environments remains an open question, especially with real-time requirement on onboard computer. This paper proposes a framework including parallelly mapping and planning and implements it on Graphics Processing Unit (GPU). First, a spherical coordinate projection is used in the occupancy grid map to avoid memory conflicts. After that, in the planning phase, a method based on lattice state space sampling is applied to obtain multiple trajectories parallelly. Then, we design a series of soft constraints to ensure that the MAV is in a safe known space with optimal dynamics. By solving the cost for each trajectory and comparison, the optimal trajectory can be generated. The effectiveness of the proposed strategy is demonstrated through simulation tests.

Towards semi-autonomous operation of an over-actuated river ferry

Abstract The automation of ships will in the long run enable new mobility concepts and profitable business models both for offshore and inland vessels. However, automation in shipping can already today offer significant benefits for the environment as well as for the safety of people, infrastructure and the vessel itself. To gain these advantages, sophisticated sensors, reliable propulsion systems and intelligent algorithms are required. In this context, the project AKOON is investigating the potential of the automation of a river ferry. The ferry under investigation operates on the Rhine near Mainz in Germany and is being converted to a fully automated vessel as part of the research project. This article gives an overview of the guidance, navigation and control (GNC) modules of the automation with focus on the trajectory planning and trajectory tracking modules. The trajectory planning uses hybrid-state A* to find safe and fuel-efficient routes. The subsequent trajectory tracking is achieved by a two-level approach that uses a state-space controller and an optimization-based thrust allocation to efficiently operate the over-actuated propulsion system consisting of four cycloidal propellers. Results from a high-fidelity vessel simulator based on state-of-the-art hydrodynamic simulations show that the presented approach allows the generation of collision-free reference trajectories, that can be tracked safely even in cases of model mismatches and disturbances.

Computational fluid dynamics investigations of aerodynamic control surfaces of a vertical landing configuration

The European project RETALT (Retro Propulsion Assisted Landing Technologies), funded by the Horizon 2020 framework program (Grant agreement No 821890), has as main objective to investigate critical technologies for the assisted descent and landing of re-usable first stages. Among these technologies, one can find aerodynamics, aerothermodynamics, flight dynamics, guidance navigation and control (GNC), Structures, mechanisms, thrust vector control (TVC) and thermal protection systems (TPS). The present paper focuses in particularly on the aerodynamics technology applied to a vertical landing launcher configuration, called RETALT1, including retro-propulsion. During the landing phase of the first stage of the launcher, the main devices for control and trim of the vehicle (besides the retro-propulsion) are the aerodynamic control surfaces (ACS). Three types of aerodynamic control surfaces are investigated by means of numerical computations, using the NSMB (Navier Stokes Multi Block) CFD code. The control surfaces considered are the deployable interstage segments (also named petals), grid fins and planar fins. Aerodynamic coefficients as well as forces acting on the control surfaces are extracted from the CFD computations to assess the efficiency of each type of devices and to populate the Aerodynamic Database (AEDB) for flight dynamic analysis.

A numerical model of dust particle impacts during a cometary encounter with application to ESA’s Comet Interceptor mission

The attitude perturbations caused by large dust particle impacts on a three-axis stabilized spacecraft during a high velocity encounter with a comet are studied. Specifically, a numerical model is used to make order of magnitude estimations in relation to the European Space Agency’s Comet Interceptor mission and help constrain requirements for guidance, navigation and control (GNC). Our model is able to reproduce the measurements acquired by the spin-stabilized Giotto spacecraft during its encounter with comet 1P/Halley in 1986. For realistic scenarios the total change in angular velocity that needs to be corrected can reach 1–10 °/s. At closest approach the median shift of the target object on the Comet Camera (CoCa) detector is typically larger then 10 pixels for the modelled scenarios. Our model shows that the encounter velocity, the spacecraft radius and the attitude control rate are the most critical factors. For the free parameters scaling laws are derived.

Modular Model-Based Design for Aerial Manipulation with Simulink and ROS

Model-based design utilizing Simulink is state of the art in mechatronic system development. A key advantage is that developed control algorithms are deployed onto the target execution platform by automated code generation. For many robotic applications, the Robotic Operating System (ROS) is an attractive target execution platform with growing interest in UAV development such as aerial manipulation. The presented model-based design approach includes modular Guidance, Navigation and Control (GNC) development in Simulink and code generation of encapsulated ROS nodes for each of the GNC modules. To reduce control cycle latency, an automated code modification is proposed, for which design guidelines are given to define an efficient ROS node execution order. The modular approach is compared to a monolithic approach where just a single ROS node is generated for the complete GNC functionality. The design approach is demonstrated by flight experiments for an aerial screwing process where lateral contact forces at the manipulator tip are generated. Force estimation results compared to ground truth measurements show good agreement in flight experiment and simulation. For this case study, the modular design approach results in more than 73% time saving for code generation.

Collision avoidance guidance and control scheme for vector propulsion unmanned surface vehicle with disturbance

In this paper, a collision avoidance guidance and control (CAGC) scheme for fully autonomous unmanned surface vehicle (USV) according to the guidance, navigation and control (GNC) architecture is studied. The CAGC scheme is divided into guidance layer and control layer. To avoid the possibility of collision in tracking guidance, the proposed guidance layer needs remove the tracking guidance and realize the direct guidance to the control layer, which is designed according to the theory of finite control set model predictive control (FCS-MPC) with control ability. Next, to balance the contradiction between calculation and guidance accuracy, the methods of delay compensation and control set normal distribution are designed. In addition, in the control layer, the vector propulsion USV as the control object is non-minimum phase system because of its small size and significant sway thrust, so the virtual control point is used to solve this system, and the relationship between virtual control point and vessel speed is determined by zero-dynamics stability analysis. And the control layer adopts adaptive sliding mode control theory to resist the influence of strong disturbances. Finally, simulation results are provided to illustrate the efficacy of the CAGC scheme.

A Safety Prediction System for Lunar Orbit Rendezvous and Docking Mission

In view of the characteristics of the guidance, navigation and control (GNC) system of the lunar orbit rendezvous and docking (RVD), we design an auxiliary safety prediction system based on the human–machine collaboration framework. The system contains two parts, including the construction of the rendezvous and docking safety rule knowledge base by the use of machine learning methods, and the prediction of safety by the use of the base. First, in the ground semi-physical simulation test environment, feature extraction and matching are performed on the images taken by the navigation surveillance camera. Then, the matched features and the rendezvous and docking deviation are used to form training sample pairs, which are further used to construct the safety rule knowledge base by using the decision tree method. Finally, the safety rule knowledge base is used to predict the safety of the subsequent process of the rendezvous and docking based on the current images taken by the surveillance camera, and the probability of success is obtained. Semi-physical experiments on the ground show that the system can improve the level of intelligence in the flight control process and effectively assist ground flight controllers in data monitoring and mission decision-making.

Guidance, navigation and control for 6DOF rendezvous in Cislunar multi-body environment

Recent studies highlighted the benefits of a support infrastructure located in Cislunar environment, which would ease the design of forthcoming space missions with a favorable access from and to the lunar surface, the Earth and many interplanetary destinations. Multi-body orbits rose a peculiar interest and were selected to stage a human-robotic exploration outpost; the family of Near Rectilinear Halo Orbits (NRHO), in particular, appears specifically suitable in these regards. Among the different capabilities that such outpost will tend to, the docking with other crewed or autonomous vehicles is a key feature that shall be present. Although low Earth orbit (LEO) rendezvous and docking is well assessed, no mission has performed such task in a multi-body gravitational environment. The paper presents a guidance, navigation and control (GNC) framework for 6 degrees of freedom (6DOF) coupled Cislunar rendezvous and docking. A feasible operational rendezvous scenario is detailed and exploited to define open-loop and closed-loop GNC functions for far-range and close-range. Then, the final approach is analyzed, proposing a closed-loop GNC that encompasses coupled translational-rotational dynamics. Vision-based only relative navigation techniques are applied to Cislunar multi-body dynamics to guarantee a coupled state estimation with a simple suite of sensors and a broad applicability range, ranging from passively cooperative to non-cooperative or unknown target spacecraft.

Path Following Control for UAV Using Deep Reinforcement Learning Approach

Unmanned aerial vehicles (UAVs) have been extensively used in civil and industrial applications due to the rapid development of the guidance, navigation and control (GNC) technologies. Especially, using deep reinforcement learning methods for motion control acquires a major progress recently, since deep [Formula: see text]-learning algorithm has been successfully applied to the continuous action domain problem. This paper proposes an improved deep deterministic policy gradient (DDPG) algorithm for path following control problem of UAV. A specific reward function is designed for minimizing the cross-track error of the path following problem. In the training phase, a double experience replay buffer (DERB) is used to increase the learning efficiency and accelerate the convergence speed. First, the model of UAV path following problem has been established. After that, the framework of DDPG algorithm is constructed. Then the state space, action space and reward function of the UAV path following algorithm are designed. DERB is proposed to accelerate the training phase. Finally, simulation results are carried out to show the effectiveness of the proposed DERB–DDPG method.

Sensor hybridization using neural networks for rocket terminal guidance

The Guidance, Navigation and Control (GNC) of air and space vehicles, including artillery rockets, has been one of the spearheads of research in the aerospace field in recent times. Increasing the accuracy of these ballistic projectiles is the major goal. Using Global Navigation Satellite Systems (GNSS) and inertial navigation systems, accuracy may be detached from range. However, during the terminal stage of flight, when movement is governed by highly changing nonlinear forces and moments, GNC strategies based on these systems cause enormous errors in determining attitude and position. These effects can be diminished using additional sensors, independent of jamming and cumulative errors, such as the quadrant photo-detector semi-active laser. This paper proposes a novel non-linear hybridization algorithm, which is based on neural networks, to feed GNC systems while complexity and costs are reduced. It fuses the information from multi-sensor signals, such as GNSS, inertial navigation systems, and semi-active lasers, to predict the line of sight vector, which joins the target and the projectile and drives the flight. As compared to traditional approaches, the use of a neural network presents the advantage that once the network is trained, it is no longer necessary to know the physical-mathematical foundations that govern the dynamics of flight. Instead, it is the network that learns the dynamics. Six-degree-of-freedom non-linear simulations, which are based on real flight dynamics, are used to train the neural networks in the hybridization process. Once training is finished, the approach is tested and simulated together with modified proportional navigation techniques and control methods. Monte Carlo analysis is conducted to determine the suitability of the closed-loop performance across a full spectrum of uncertainty conditions regarding launch, sensor performance, atmospheric, and thrust.