POLI-Rotorcraft

POLI-Rotorcraft is a research group of the Dipartimento di Ingegneria Aerospaziale of the Politecnico di Milano (DIA-PoliMI), which specializes in flight mechanics, aero-servo-elasticity and design of rotorcraft vehicles. POLI-Rotorcraft is supported by Italian and foreign industrial and governmental entities, and works on real-life problems in close collaboration with industry and other academic institutions. Numerical simulations which enable the research activities are often conducted with in-house-developed tools built on the specific modeling and simulation capabilities of the group.  POLI-Rotorcraft is currently working on the research projects listed below, and is always interested in receiving applications from motivated students and post-docs.

RESEARCH PROJECTS

Trajectory Optimization of Maneuvering Vehicles. Our group is developing numerical procedures for computing optimal trajectories of rotary-wing vehicles, for example during emergency take-offs and landings, auto-rotation, tail rotor loss, etc. Maneuvers are defined as optimal control problems for a flight-mechanics model of the vehicle. We have developed a general purpose software tool, named TOP, Trajectory Optimization Program, which is currently in use by industry. The code supports different vehicle models, including an interface with FlightLabTM and a generic interface to other flight simulators, and different solutions strategies, including implementations of the direct transcription and direct multiple shooting methods. Currently, TOP is being upgraded to include a number of optimization-based parameter estimation methods (including the constrained least-squares, constrained output-error and constrained filter-error methods). These methods share with the trajectory optimization problems the flight mechanics models, the temporal discretization techniques (direct transcription, direct multiple shooting) and the resulting non-linear programming problem solvers; we are exploiting this fact to develop a single code that supports both the optimization of trajectories and the optimization of model parameters, avoiding code duplication, simplifying code maintenance and debugging, and easying the training of users. Selected references: C.L. Bottasso, F. Luraghi, G. Maisano, `A Unified Approach to Trajectory Optimization and Parameter Estimation in Vehicle Dynamics', Keynote lecture, CMND 2009, International Symposium on Coupled Methods in Numerical Dynamics, Split, Croatia, September 16-19, 2009. [preprint] C.L. Bottasso, G. Maisano, F. Scorcelletti, `Trajectory Optimization Procedures for Rotorcraft Vehicles, their Software Implementation and Applicability to Models of Varying Complexity',  Journal of the American Helicopter Society, under review, 2008. [preprint] C.L. Bottasso, A. Croce, D. Leonello, L. Riviello, `Optimization of Critical Trajectories for Rotorcraft Vehicles', Journal of the American Helicopter Society, 50:165-177, 2005. C.L. Bottasso, A. Croce, D. Leonello, L. Riviello, `Rotorcraft Trajectory Optimization with Realizability Considerations', Journal of Aerospace Engineering, 18:146-155, 2005. C.L. Bottasso, G. Maisano, F. Scorcelletti, `Trajectory Optimization of Rotorcraft Including Pilot Models, with Applications to ADS-33 MTEs, Cat-A Procedures and Engine Off Landings', American Helicopter Society 65th Annual Forum and Technology Display, Gaylord Texan Convention Center, Grapevine, TX, USA, May 27-29, 2009. [preprint] C.L. Bottasso, F. Scorcelletti, G. Maisano, A. Ragazzi, ‘Trajectory Optimization Strategies for the Simulation of ADS-33 Mission Task Elements’, 34th European Rotorcraft Forum, Liverpool, UK, September 16–19, 2008. [paper, presentation] C.L. Bottasso, G. Maisano, F. Scorcelletti, ‘Trajectory Optimization Procedures for Rotorcraft Vehicles, their Software Implementation and Applicability to Models of Varying Complexity’, AHS 64th Annual Forum and Technology Display, Montreal, Canada, April 29 – May 1, 2008. [presentation] C.L. Bottasso, A. Croce, D. Leonello, L. Riviello, `Optimization of Critical Trajectories for Rotorcraft Vehicles', AHS 60th Annual Forum & Technology Display, Baltimore, MD, USA, June 8-10, 2004. [presentation]   The following are applications of our trajectory optimization technology to supercavitating vehicles: C.L. Bottasso, L. Riviello, M. Ruzzene, F. Scorcelletti, `A Direct Multiple Shooting Approach to the Solution of Optimal Control Problems with Time-Delays', Journal of Optimization Theory and Applications, under review, 2008. [preprint] S.S. Ahn, M. Ruzzene, F. Scorcelletti, C.L. Bottasso, `Configuration Optimization of Supercavitating Underwater Vehicles with Maneuvering Constraints', IEEE Journal of Oceanic Engineering, under review, 2007. [preprint] C.L. Bottasso, F. Scorcelletti, M. Ruzzene, S.S. Ahn, `Trajectory Optimization for DDE Models of Supercavitating Underwater Vehicles', ASME Journal of Dynamic Systems, Measurement, and Control, under review, 2007. [preprint] Comprehensive Models of Maneuvering Vehicles. This project is concerned with the development of procedures for simulating maneuvering vehicles using high-fidelity comprehensive models, with an emphasis on rotary-wing vehicles (helicopters and tilt-rotors). Our approach is based on: 1) a planning layer that determines the tracking trajectory solving an optimal control problem for a reduced model of the vehicle, 2) a tracking layer based on a model predictive controller, and 3) a neural-network-based adaptive element that improves the reduced model used during planning and tracking. With these methods, we were able to demonstrate the ability to simulate a variety of extremal maneuvers at the boundaries of the flight envelope using comprehensive multibody vehicle models of several thousand degrees of freedom, including Cathegory A take-offs and landings. Selected references: C.L. Bottasso, ‘Solution Procedures for Maneuvering Multibody Dynamics Problems for Vehicle Models of Varying Complexity’, Multibody Dynamics — Computational Methods and Applications, C.L. Bottasso, Ed., Computational Methods in Applied Sciences, ISBN 978-1-4020-8828-5, Springer-Verlag, Dordrecht, The Netherlands, 2008. [book flyer, link on Springer's web site] C.L. Bottasso, A. Croce, D. Leonello, `Neural-Augmented Planning and Tracking Pilots for Maneuvering Multibody Dynamics', Multibody Dynamics. Computational Methods and Applications, J.C. García Orden, J.M. Goicolea, J. Cuadrado, Eds., Computational Methods in Applied Sciences, ISBN 1-4020-5683-4, Springer-Verlag, Dordrecht, The Netherlands, 2007. C.L. Bottasso, C.-S. Chang, A. Croce, D. Leonello, L. Riviello, `Adaptive Planning and Tracking of Trajectories for the Simulation of Maneuvers with Multibody Models', Computer Methods in Applied Mechanics and Engineering, invited paper, Special Issue on Computational Multibody Dynamics, 195:7052-7072, 2006. C.L. Bottasso, A. Croce, D. Leonello, L. Riviello, `Procedures for Enabling the Simulation of Maneuvers with Comprehensive Codes', 31st European Rotorcraft Forum, Firenze, Italy, September 13-15, 2005. [presentation] Trimming of Comprehensive Vehicle Models. The aeromechanical analysis of rotorcraft using comprehensive vehicle models is crucially dependent on the ability to accurately compute the model trim settings. Among the various techniques proposed in the literature, the auto-pilot approach, being independent of the complexity of the model, has the potential to solve trim problems efficiently even for the highly detailed aero-servo-elastic vehicle models that are developed using modern comprehensive finite-element-based analysis codes. We are studying model-based auto-pilots for trimming comprehensive rotorcraft models, which use adaptive predictive control techniques to improve on the robustness and efficiency of present methods. Selected references: C.L. Bottasso, L. Riviello, `Trim of Rotorcraft Multibody Models by a Neural-Augmented Model-Predictive Auto-Pilot', Multibody Systems Dynamics, 10th Anniversary Issue, 18:299-321, 2007. C.L. Bottasso, L. Riviello, `Rotorcraft Trim by a Neural Model-Predictive Auto-Pilot', 31st European Rotorcraft Forum, Firenze, Italy, September 13-15, 2005. Winner of the Cheeseman Best Paper Award. [presentation] STAR, Scientific Testbed for Autonomous Rotorcraft. STAR is a project devoted to the development and testing of technological solutions for robotic rotorcraft vehicles, including navigation and control strategies, vision, flight envelope protection, etc. We use off-the-shelf hobby helicopters as flying platforms, but all the rest is fully in-house developed, following a strict bottom-up approach. The on-board control hardware is based on the PC-104 standard, which supports the Inertial Navigation System and the Guidance and Control algorithms running a Linux-based real-time OS. The STAR system is supported by a complete suite of flight, sub-system and vision simulation tools that allow for the testing of the algorithms in a synthetic environment. Selected references: C.L. Bottasso, D. Leonello, ‘Vision-Aided Inertial Navigation by Sensor Fusion for an Autonomous Rotorcraft Vehicle’, AHS International Specialists’ Meeting on Unmanned Rotorcraft, Scottsdale, AZ, USA, January 20–22, 2009. [paper, presentation] C.L. Bottasso, D. Leonello, A. Maffezzoli, F. Riccardi, `A Procedure for the Identification of the Inertial Properties of Small-Size UAVs', XX AIDAA National Conference, Milano, Italy, June 29-July 3, 2009. [paper] C.L. Bottasso, A. Croce, R. Nicastro, L. Riviello, B. Savini, `Adaptive Reference-Augmented Predictive Control, with Application to the Reflexive Control of Unmanned Rotorcraft Vehicles', Automatic Control in Aerospace, under review, 2008. [preprint] C.L. Bottasso, D. Leonello, B. Savini, `Path Planning for Autonomous Vehicles by Trajectory Smoothing using Motion Primitives', IEEE Transactions on Control Systems Technology, accepted, to appear. [preprint] C.L. Bottasso, A. Croce, R. Nicastro, L. Riviello, B. Savini, `Adaptive Augmented Control of Unmanned Rotorcraft Vehicles', AHS International Specialists' Meeting on Unmanned Rotorcraft, Phoenix, AZ, USA, January 23-25, 2007. [presentation] C.L. Bottasso, D. Leonello, B. Savini, `Trajectory Planning for UAVs by Smoothing with Motion Primitives', AHS International Specialists' Meeting on Unmanned Rotorcraft, Phoenix, AZ, USA, January 23-25, 2007. [presentation] SimPLe, the Simulator of the Politecnico in Lecco. SimPLe is a new project which is devoted to the design and implementation of a rotorcraft flight simulator in the new Campus of the Politecnico in Lecco, within the CampusPoint project. The simulator is being designed based on a modular architecture, so that software and hardware sub-systems can be easily upgraded or modified, and on off-the-shelf components to limit costs. Once the simulator will be operational, SimPLe will support research in real-time vehicle modeling, cueing systems, flight-envelope protection, carefree maneuvering, all-weather operations, pilot modeling, emergency take-off and landings, model identification. System Identification Techniques for Comprehensive Rotorcraft Models. This research studies the identification from experimental flight data of rotorcraft vehicle models. The emphasis of our efforts is in methods which are applicable to sophisticated comprehensive non-linear vehicle models, for which methods and best practices for system identification from experimental data are still lacking. In fact, present hardware has enough computing power to enable the use of sophisticated multibody vehicle models not only for design but even for real-time flight simulation. Methods and tools for readily tuning these non-linear and possibly large models to flight data are crucial for providing the best possible fidelity of the models to reality. To this end, we are developing software procedures in the time domain and we are working with industry to test and demonstrate the tools on real rotorcraft applications. The software is being implemented within the TOP code described above, a general purpose constrained optimizer for rotorcraft flight mechanics applications, capable of supporting the estimation of optimal model parameters and the computation of optimal trajectories for vehicle models of varying complexity, from simple rigid body with stability derivatives to sophisticated compherensive first-principle models.   Selected references: C.L. Bottasso, F. Luraghi, G. Maisano, ‘Time-Domain Parameter Estimation for First-Principle Rotorcraft Models using Recursive and Batch Procedures: Formulation and Preliminary Results’, Scientific Report DIA-SR 09-05, Dipartimento di Ingegneria Aerospaziale, Politecnico di Milano, April 2009. [report] C.L. Bottasso, F. Luraghi, G. Maisano, `A Unified Approach to Trajectory Optimization and Parameter Estimation in Vehicle Dynamics', Keynote lecture, CMND 2009, International Symposium on Coupled Methods in Numerical Dynamics, Split, Croatia, September 16-19, 2009. [preprint] Adaptive Hydraulic Dampers. We are working with industry on the development of an adaptive hydraulic damper for helicopter rotors. Damping modulation is achieved by means of a by-pass valve which connects the two hydraulic chambers. We have developed a detailed model of the hydraulic damper, which has been validaded by comparison with experimental data, together with an aero-elastic model of the A-109E helicopter. Using these modeling tools, we are conducting studies on control laws and damping scheduling strategies with the final goal of enhancing the life of the damper and of its interfaces with the rotor system. Selected references: C.L. Bottasso, S. Cacciola, A. Croce, L. Dozio, `Load Reduction in Lead-Lag Dampers by Speed-Scheduled Aperture and Modulated Control of a By-Pass Valve', American Helicopter Society 66th Annual Forum and Technology Display, Phoenix Convention Center, Phoenix, AZ, USA, May 11-13, 2010. [paper, pptx presentation, pdf presentation] Methods and Tools for Comprehensive Vehicle Modeling. Since several years, the group has been actively working on finite-element-based multibody procedures for modeling complex aeroelastic systems, with particular emphasis on rotorcraft vehicles. Specific attention has been devoted to time integration schemes for DAE index-3 formulations, leading to contributions in the area of non-linearly stable energy preserving/decaying schemes and scaling techniques. Selected references: C.L. Bottasso, `Computational Dynamics', Encyclopedia of Aerospace Engineering, R. Blockley, W. Shyy, Eds., John Wiley & Sons, Ltd, to appear, 2010. [preprint] C.L. Bottasso, `Numerical Simulation of Aero-Servo-Elastic Problems, with Application to Wind Turbines and Rotary Wing Vehicles', invited keynote lecture, COMPDYN 2007, Computational Methods in Structural Dynamics and Earthquake Engineering, Rethymno, Crete, Greece, June 13-15, 2007. [presentation] O.A. Bauchau, A. Epple, C.L. Bottasso, `Scaling of Constraints and Augmented Lagrangian Formulations in Multibody Dynamics Simulations', ASME Journal of Computational and Nonlinear Dynamics, under review, 2007. [preprint] C.L. Bottasso, D. Dopico, L. Trainelli, `On the Optimal Scaling of Index Three DAEs in Multibody Dynamics', Multibody Systems Dynamics, accepted, to appear. C.L. Bottasso, O.A. Bauchau, A. Cardona, `Time-Step-Size-Independent Conditioning and Sensitivity to Perturbations in the Numerical Solution of Index Three Differential Algebraic Equations', SIAM Journal on Scientific Computing, 29:397-414, 2007. C.L. Bottasso, D. Dopico, L. Trainelli, `Optimal Preconditioners for the Solution of Constrained Mechanical Systems in Index-3 Form', ACMD06, 3rd Asian Conference on Multibody Dynamics, Komaba, Tokyo, Japan, August 1-4, 2006. [presentation] C.L. Bottasso, L. Trainelli, `An Attempt at the Classification of Energy Decaying Schemes for Structural and Multibody Dynamics', Multibody Systems Dynamics, 12:173-185, 2004. M. Borri, C.L. Bottasso, L. Trainelli, `An Invariant-Preserving Approach to Robust Finite-Element Multibody Simulation', ZAMM, Zeitschrift für Angewandte Mathematik und Mechanik, 83:663-676, 2003. O.A. Bauchau, C.L. Bottasso, L. Trainelli, `Robust Integration Schemes for Flexible Multibody Systems', Computer Methods in Applied Mechanics and Engineering, 192:395-420, 2003. C.L. Bottasso, M. Borri, L. Trainelli, `Geometric Invariance', Computational Mechanics, 29:163-169, 2002. Rotorcraft Design. - We are working on a new vehicle concept based on two variable-speed fixed-pitch counter-rotating rotors, which uses a patented configuration of split control vanes for the control of the vehicle on the three axes. Vehicles designed around this new rotor concept are extremely compact and safe, since the vehicle has no tail rotor; furthermore, the rotor head is of light weight and of an extremely simple configuration, the blades being non-articulated and of fixed pitch. The preliminary design has been completed, together with the detailed design of a wind tunnel model for testing. Structural and aerodynamic testing are being conducted at the POLI-Rotorcraft lab. - We have conducted preliminary studies on the applicability of helicopters to support fire-fighting efforts in high-rise buildings, as detailed in the following paper : E. Zanenga, D. Leonello, C.L. Bottasso, ‘Feasibility Study of Rotorcraft Fire Fighting for High-Rise Buildings’, Journal of Aerospace Engineering, accepted, to appear, 2010. [preprint]

RESEARCH GROUP

- Carlo L. Bottasso, Professor, phone +39-02-2399-8315, email carlo.bottasso@polimi.it, web page - Alessandro Croce (comprehensive models), Assistant Professor, phone +39-02-2399-8322, email croce@aero.polimi.it, web page - Ehsan Asadi (rotorcraft UAV) Ph.D. Candidate, phone +39-02-2399-8299, email: asadi@aero.polimi.it, web page - Mehmet Suat Kay (rotorcraft UAV) Ph.D. Candidate, phone +39-02-2399-8299, email: kay@aero.polimi.it, web page - Kuray Kucuk (rotorcraft UAV) Ph.D. Candidate, phone +39-02-2399-8299, email: kucuk@aero.polimi.it, web page - Domenico Leonello (rotorcraft UAV, vision), AWPARC Research Engineer, phone +39-02-2399-8299, email: leonello@aero.polimi.it, web page - Giorgio Maisano (trajectory optimization), AWPARC Research Engineer, phone +39-02-2399-8299, email: maisano@aero.polimi.it, web page - Andrea Monterisi (SimPLe, flight simulation) Ph.D candidate, phone +39-02-2399-8299, email: monterisi@aero.polimi.it, web page - Alberto Rolando (SimPLe) Post-Doc, phone +39-02-2399-8299, email: rolando@aero.polimi.it, web page - A varying number of M.S. students Former members: - Giovanni Giardini, Post-Doc - Fabio Luraghi, Ph.D. - Roberto Nicastro, research engineer - Fabio Riccardi, research engineer - Luca Riviello, Ph.D. - Barbara Savini, Ph.D., then Post-Doc - Francesco Scorcelletti, Ph.D.

AVAILABLE THESIS TOPICS

We have several thesis projects available in the area of rotorcraft UAV hardware and software, aero-servo-elasticity, flight control laws, etc. Please contact Dr. Bottasso for further specific information.