Meyer Nahon

• PhD
• Professor at McGill University

New aircraft architectures are being proposed for unmanned aerial vehicles and air taxis, which include tilt-able motor and propellers. These propulsive units operate with a propeller axis at an angle oblique to the flight direction, and thus it is important to understand and model how thrust is produced by a propeller operating under these conditi...

New aircraft architectures are being proposed for unmanned aerial vehicles and air taxis, which include tilt-able motor and propellers. These propulsive units operate with a propeller axis at an angle oblique to the flight direction, and thus it is important to understand and model how thrust is produced by a propeller operating under these conditi...

An exergy analysis of a solid polymer fuel cell power system for transportation applications is reported. The analysis was completed by implementing the derived fundamental governing second law equations for the system into a fuel cell performance model developed previously. The model analyzes all components of the system including the fuel cell st...

This work presents a comprehensive semi-autonomous control system for agile fixed-wing unmanned aerial vehicles. These versatile platforms are capable of steady flight and thrust-borne hover, but owing to their design are challenging to control for a remote operator with limited visual feedback. The proposed pilot-assist solution uses a unified con...

Agile, fixed-wing, aircraft have been proposed for diverse applications, due to their enhanced flight efficiency, compared to rotorcraft, and their superior maneuverability, relative to conventional, fixed-wing, aircraft. We present a novel, reactive, obstacle-avoidance algorithm that enables autonomous flight through unknown, cluttered environment...

Unmanned Aerial Gliders form a subclass of fixed-wing Unmanned Aerial Vehicles which promise to offer sustained flight for a wide range of applications. Autonomous soaring allows these aircraft to detect and exploit rising air masses (thermals) without user input, which greatly simplifies their operation. While previous research has focused on the...

We consider a vertical cantilevered pipe conveying fluid, located in a container filled with the same fluid; the upper portion of the pipe is surrounded by a rigid cylindrical tube of larger diameter, thus forming an annular fluid-filled region around the pipe. Two flow configurations are investigated: (a) the fluid enters the pipe at its clamped u...

Unmanned aerial vehicles (UAVs) have become popular in a wide range of applications, including many military and civilian uses. State-of-the-art control strategies for these vehicles are typically tailored to a specific platform and are often limited to a portion of the vehicle’s flight envelope. This article presents a single physics-based control...

The system under consideration comprises a flexible pipe and a rigid outer tube; the pipe and tube are concentric and vertically cantilevered from their top ends in a large water-filled cylindrical tank. The space between the pipe and tube forms an annulus around the upper portion of the pipe. The working fluid is water. The fluid enters the annulu...

A linear model is developed for a hanging pipe aspirating fluid with internal flow velocity Ui, flowing up the pipe from its lower end, and also subjected to an external flow of velocity Uo flowing down from the upper end of the annulus formed between the pipe and a relatively shorter rigid outer tube; both the tube and pipe are cantilevered from t...

Moving path frames assigned to spatial curves are commonly used in the development of motion control laws for autonomous vehicles. This work presents the Gravity Normal frame, a novel navigation reference frame developed specifically for autonomous vehicle applications. This moving path frame incorporates the knowledge that many autonomous vehicles...

Quadrotors are highly maneuverable vehicles that can be used to perform extremely aggressive maneuvers. Commanding a quadrotor to perform a maneuver that is beyond the physical capabilities of its actuators leads to actuator saturation. A prolonged state of saturated actuators can cause the vehicle to behave unpredictably. This work investigates th...

Small fixed-wing unmanned aerial vehicles (UAVs) are becoming increasingly capable of flying at low altitudes and in constrained environments. This paper addresses the problem of automating the flight of a fixed-wing UAV through highly constrained environments. The main contribution of this paper is the development of a maneuver space, integrating...

An extensive evaluation of attitude estimation algorithms in simulation and experiments is performed to determine their suitability for a collision recovery pipeline of a quadcopter unmanned aerial vehicle. A multiplicative extended Kalman filter (MEKF), unscented Kalman filter (UKF), complementary filter, [Formula: see text] filter, and novel adap...

We consider a hanging cantilevered pipe conveying water within a water-filled container; the upper portion of the pipe is surrounded by a rigid cylindrical tube of larger diameter, forming an annular fluid-filled region around the pipe. Two flow configurations are investigated : (a) water enters the pipe at its clamped end and flows downwards, disc...

This paper presents a rigid multibody dynamic model to simulate the dynamic response of a spar floating offshore wind turbine (FOWT). The system consists of a spar floating platform, the moorings, the wind turbine tower, nacelle, and the rotor. The spar platform is modeled as a six degrees-of-freedom (6DOFs) rigid body subject to buoyancy, hydrodyn...

This paper presents a general and systematic approach to automating a variety of agile maneuvers with a small fixed-wing unmanned aerial vehicle. The methodology begins by numerically solving optimal control problems off-line to generate a small set of reference trajectories and feedforward control inputs for maneuvers. A dynamic time warping-based...

The use of unmanned aerial vehicles (UAVs) has become ubiquitous in a broadening range of applications, including many civilian uses. UAVs are typically categorized into two categories: conventional fixed-wing aircraft, which are associated with efficient flight over long distances, and rotor-craft, which are associated with short flights requiring...

Pipes aspirating fluid have applications in the filling and recovery processes for underground caverns — large subterranean cavities used to store hydrocarbons, such as natural gas and oil. This paper deals with the dynamics of a vertical cantilevered flexible pipe, immersed in fluid. Fluid is aspirated from its bottom free end up to the fixed uppe...

This paper presents a modeling approach for the nonlinear flexible dynamics simulation of a floating offshore wind turbine (FOWT). The system consists of a floating platform, the moorings, the wind turbine tower, nacelle and the rotor. The floating platform is modeled as a six-degrees-of-freedom (6-DOF) rigid body subject to buoyancy, hydrodynamic...

This paper presents a general three-dimensional flexible dynamic model of a tip-loaded rotating cantilever beam. For generality, the beam tip is assumed to be loaded with a rigid body with an arbitrary center of mass position, and subject to external force and moment. The coupled longitudinal (axial), bending–bending, and twist elastic motions are...

This paper investigates an aerobatic manoeuvre performed by an agile fixed-wing unmanned aerial vehicle, with the intent of determining how best the manoeuvre can be automated. The manoeuvre is an aggressive turn-around: a 180 degree reversal of the aircraft’s heading, in which the space required for completing the turn is minimized. A comprehensiv...

This paper presents an exact nonlinear analysis for the stiffness of a mooring system as a function of the displacement and orientation of the floating structure. The analysis allows a derivation of the mooring stiffness matrix while considering slack mooring line resting on the seabed, as well as slack and taut suspended lines. In contrast to othe...

A special class of fixed-wing UAVs called agile UAVs have emerged recently, that are lightweight with control surfaces as big as 50% chord capable of deflecting up to 50 deg., and are characterized by high thrust-to-weight ratios of around 2–3, and a strong propwash. Such configuration allows agile UAVs to perform extreme aerobatic maneuvers that e...

In this paper an adaptive robust control scheme along with its simulation on quadrotor is presented to deal with payload variation and unknown disturbance. Parametric and nonparametric uncertainties in the quadrotor model always make it difficult to design a controller to meet the performance requirement in various conditions during flight time. Ad...

Recent interest in high-angle-of-attack flight, aerobatic maneuvering, vertical/short takeoff and landing, etc., of small unmanned aerial vehicles necessitates more detailed modeling of the complex aerodynamics associated with these flight regimes. This includes modeling the effect of the propeller slipstream, also called prop wash, which is the ma...

Purpose – The purpose of this paper is to develop a physics-based model for UAV propellers that is capable of predicting all aerodynamic forces and moments in any general forward flight condition such as no flow, pure axial flow and pure side flow etc. Design/methodology/approach – The methodology adopted in this paper is the widely used Blade Ele...

Aerial platforms can play a unique and valuable role in the exploration of Mars since they provide a means of bridging the gap between orbital and ground based investigations of Mars. The primary purpose of this paper is to provide a framework for comparing the performance of fixed-wing aircraft, airships, and rotary-wing aircraft in the Martian en...

This paper investigates the ability of a quadrotor to maneuver in a wind field. A dynamic model of a quadrotor is presented to model its motion. The quadrotor model includes a wind effect model to quantify the effect of wind on the dynamics of a quadrotor. A proportional-integral-derivative (PID) controller is shown as a baseline controller typical...

This paper provides a comprehensive theoretical analysis to determine the nonlinear hydrostatic restoring loads and stiffnesses of a floating offshore platform. A new approach is developed to calculate the buoyancy forces and the corresponding moments for general 3D displacements of offshore platforms that utilize cylindrical floaters, such as barg...

Agile UAVs is a special class of fixed-wing aircraft characterized by high thrust-to-weight ratios (around 2 to 3) and big control surfaces (around 40 to 50% chord) with deflections as large as 50 degrees; and hence capable of extreme maneuvers and aerobatics. The intent of this paper is to model the aerodynamics of agile UAVs for real-time applica...

A digital driver that has a switched self-tuning gain in its current regulator is designed for five-phase stepping motors so that their performance could be improved and adjusted more easily, than with an analog driver. The regulator has a fixed gain block in its feedback loop and an adjustable gain in the feedforward path, replacing the integrator...

This paper investigates the restoring stiffness of the main platform concepts proposed for offshore floating wind turbine (FWT) systems; namely, barge, spar, tension leg platform (TLP). The overall system stiffness is partly due to the hydrostatics, and partly due to mooring. The hydrostatic stiffness matrix is formulated using the linear hydrostat...

Aqua is an underwater biomimetic vehicle designed and built at McGill University that uses six paddles to produce control and propulsion forces. It has the particularity of having time-periodic thrust due to its oscillating paddles. Using an existing model of the vehicle, two types of controller were developed: a PD controller and a Floquet control...

A discretization method is proposed for continuous-time, non-autonomous, and nonlinear systems. The concept of continualization is used to derive a sufficient condition for a given discrete-time system to be an exact discretization of a continuous-time system. The proposed discretization method is based on an approximate solution to this condition,...

Ground effect on rotary aircraft has been studied for many decades. Although a large body of research results is now available for conventional helicopters, this topic is just beginning to receive attention in the unmanned aerial vehicles community, particularly for small size UAVs. The objective of this paper is to assess the applicability of a wi...

Airflow from the propeller, called the propeller slipstream or propwash, plays an important role in the aerodynamics of small unmanned aerial vehicles (UAVs). In fact, flights at low forward speeds or extreme angle of attack (AoA) maneuvers of small fixed-wing UAVs are possible only because the propeller slipstream provides the airflow necessary to...

The research discussed here proposes a control system with compensation to maintain consistent performance for quadrotors under system variations, specifically due to battery drainage and mass changes. This compensation control system is comprised of three subsystems. The first subsystem is a baseline PID controller, which generates a desired rpm f...

The constraint performance analysis in the limited kinetostatic subspace of parallel manipulators is a significant but ignored issue. The motion/force constrainability analysis, with focus on lower-mobility parallel manipulators, is the subject of this study. Via the theory of screws, three generalized frame-invariant constraint indices are propose...

Aqua is an underwater biomimetic vehicle designed and built at McGill University that uses six oscillating paddles to produce control and propulsion forces. These oscillating paddles provide a time-periodic thrust. Using an existing dynamics model of the vehicle and a numerical simulation, an adaptive controller was developed to provide trajectory...

Small unmanned aerial vehicles (UAVs) come in many types, the most common being fixed-wing and rotorcraft. Most of these are powered by brushless dc motors driving fixed-pitch propellers. Since the thrusters are typically quite powerful, relative to the weight of the aircraft, the motion of these UAVs is usually dominated by the thruster dynamics....

Propeller slipstream, or propwash, can significantly affect the aerodynamic characteristics of propeller driven aircraft by providing additional airflow over their aerodynamic and control surfaces. It is therefore essential to have a good knowledge of the induced velocity within the propeller slipstream to determine the aerodynamic forces and momen...

This paper presents performance metrics that can be used to evaluate the response sensitivity of a tension leg platform (TLP) to its tendons. An uncoupled TLP model ignores the intrinsic dynamics and environmental loads on the cables by treating each tendon as an ideal massless spring. A coupled TLP system, in contrast, considers the effects of dis...

In this paper, a simple but complete approach is presented for modeling the dynamics of a fixed-wing UAV capable of extreme maneuvering, and thus have a very large flight envelope. Due to their small size and light weight, these agile UAVs are strongly affected by their relatively powerful thruster(s). The key issues, essential for any thruster-dom...

Unmanned airships offer attractive benefits over other aircraft types for long endurance monitoring missions, including wildlife surveys, traffic monitoring and atmospheric measurements. Existing research on unmanned airships focuses on classical airship designs that have tailfins with deflectable control surfaces for attitude control. The present...

AQUA is an underwater hexapod robot that uses paddles to propel and orient itself. The system is typically operated remotely by a pilot, with feedback from cameras and on-board sensors. In this work, a stability augmentation system was developed and evaluated on the robot. In order to study the stability of the system, its model was linearized abou...

This paper discusses the design of a combined backstepping/Lyapunov controller for the attitude, velocity and height control of an unmanned, unstable, fin-less airship. As the airship actuation has more degrees of freedom than the motion controlled, the controller includes a quadratic optimization algorithm to find the optimal thruster commands. Th...

Hyper-redundant mechanisms (HRMs), also known as snake-like robots, are highly adaptable during locomotion on land. Researchers are currently working to extend their capabilities to aquatic environments through biomimetic undulatory propulsion. In addition to increasing the versatility of the system, truly biomimetic swimming could also provide exc...

Small UAVs can be used for many applications, but are mainly focused on surveillance tasks. They exist in a wide variety of architectures, broadly categorized as fixed-wing (conventional) aircraft and rotary wing aircraft (helicopters/quadrotors). Fixed wing aircraft are superior to rotary-wing aircraft in long distance cruise tasks, while rotary-w...

This paper describes the design and experimental validation of a controller suite allowing an unmanned, finless airship to track a series of waypoints autonomously. The control architecture consists of a low-level controller providing attitude and velocity control as well as a high-level controller performing the autonomous trajectory tracking task...

This paper focuses on a method to solve the static configuration for a lumped mass cable system. The method demonstrated here is intended to be used prior to performing a dynamics simulation of the cable. Conventional static analysis approaches resort to dynamics relaxation methods or root-finding algorithms (such as the Newton-Raphson method) to f...

New applications of streamlined Autonomous Underwater Vehicles require an AUV capable of completing missions with both high-speed straight-line runs and slow maneuvers or station keeping tasks. At low, or zero, forward speeds, the AUV's control surfaces become ineffective. To improve an AUV's low speed maneuverability, while maintaining a low drag...

Simulations are often used to evaluate space manipulator tasks that involve contact with the environment, due to the difficulty of performing realistic earth-based experiments. An important aspect of these simulations is the contact model used to determine the interbody forces between two objects in contact. In this paper, we present two compliant...

The resurgence of airships has created a need for dynamics models and simulation capabilities adapted to these lighter-than-air vehicles. However, the modeling techniques for airship dynamics have lagged behind and are less systematic than those for fixed-wing aircraft. A state-of-the-art literature review is presented on airship dynamics modeling,...

In this paper, we advance a methodology for obtaining the statics solution of lumped mass cable system. The method presented here is general enough for most cable configurations (slack or taut), and works well for a broad range of cable elasticity. The forces considered acting on the cable are due to elasticity, weight, buoyancy and aero/hydrodynam...

The large adaptive reflector is a Canadian design concept for a new type of large-scale radio telescope. This new telescope would be composed of a reflector made of individually actuated panels and a multitethered feed platform held aloft by an aerostat. This paper focuses on the position and orientation control of the feed platform. Models of both...

This paper describes work done in the modeling and control of a low speed underwater vehicle that uses paddles instead of thrusters to move in the water. A review of previously modeled vehicles and of controller designs for underwater applications is presented. Then, a method to accurately predict the thrust produced by an oscillating flexible padd...

This paper focuses on an investigation of the dynamic characteristics of a spherical aerostat on a single tether. A test facility was constructed to gather experimental data required to characterize the system. Our experiments were all in the supercritical range at Reynolds numbers greater than 3.7×105. The balloon's drag coefficient was extracted...

The research described in this paper relates to a platform under development at Quanser Inc. that embodies a novel small airship: the highly-maneuverable almost-lighter-than-air vehicle (ALTAV). Its marginal stability and redundant actuation make the problem of controller design particularly important and challenging. A high-fidelity mathematical m...

A new dynamics modeling approach is proposed for flexible airships, which integrates the flight dynamics, structural dynamics, aerostatics, and aerodynamics. In particular, a comprehensive aerodynamic computation is presented, including the potential-flow aerodynamics, the viscous effects, the forces on the fins, the forces on the hull due to the f...

AQUA is an underwater hexapod robot that uses its paddles to propel itself and control its orientation. To aid in the vehicle development, a simulation was needed to predict the motion of the robot based on its paddle oscillations. The most difficult aspect of this simulation was the characterization of the forces generated by the paddles oscillati...

Underwater operations present unique challenges and opportunities for robotic applications. These can be attributed in part to limited sensing capabilities, and to locomotion behaviours requiring control schemes adapted to specific tasks or changes in the environment. From enhancing teleoperation procedures, to providing high-level instruction, all...

In this paper the dynamic analysis of a macro–micro parallel manipulator is studied in detail. The manipulator architecture is a simplified planar version adopted from the structure of the Large Adaptive Reflector (LAR), the Canadian design of next-generation giant radio telescopes. In this structure it is proposed to use two parallel redundant man...

The capabilities of a tri-tethered aerostat positioning system are investigated using simulations of a comprehensively validated dynamics model. The physical system studied consists of a payload supported by a helium filled aerostat and attached to three anchored ground tethers actuated using winches. Closed-loop control is achieved by feeding back...

In this paper the kinematic and Jacobian analysis of a macro–micro parallel manipulator is studied in detail. The manipulator architecture is a simplified planar version adopted from the structure of the Large Adaptive Reflector (LAR), the Canadian design of the next generation of giant radio telescopes. This structure is composed of two parallel a...