Papers by Woei-Leong Chan
AIAA Journal, 2020
Micro air vehicles with flapping wings have the potential to be both more efficient and manoeuvra... more Micro air vehicles with flapping wings have the potential to be both more efficient and manoeuvrable than similar-sized fixed or rotary-wing aircraft. Reducing the perceived noise produced by flapping wings without compromising or possibly enhancing their aerodynamic performance would be crucial in surveillance and military applications. To this aim we have
International Journal of Modern Physics B, 2020
Green urbanism has stimulated more research on the aerodynamics of tree in recent years. The insi... more Green urbanism has stimulated more research on the aerodynamics of tree in recent years. The insight gained in studying wind load on trees would mitigate risk of tree falling and enable sustainable landscape planning. However, deciphering the effect of wind on trees is a daunting task because trees come in various species, shapes and sizes. In this study, we aim at conducting wind tunnel tests on various species of trees, including measuring the respective drag coefficient and turbulent flow field using a force balance and particle image velocimetry system. The wind tunnel experiment is conducted using scaled down fractal tree model at 10 and 15 m/s. The 3D-printed tree model is grown based on the data collected on the species-specific tree parameters, such as the height, trunk diameters, crown box dimensions, etc. In this paper, the wind tunnel result of Yellow Flame (Peltophorum pterocarpum) is presented. Results show that the drag coefficient for this inflexible tree model is not...
International Conference on Unmanned System
Nature in Singapore, 2021
Bulletin of the American Physical Society, 2018
The authors gratefully acknowledge the financial support of the research grant under Virtual Sing... more The authors gratefully acknowledge the financial support of the research grant under Virtual Singapore Programme (NRF2017VSG-AT3DCM001-029) from the National Research Foundation of Singapore.
In this paper, an ornithopter prototype that mimics the flapping motion of bird flight is develop... more In this paper, an ornithopter prototype that mimics the flapping motion of bird flight is developed, and the lift and thrust generation characteristics of different wing designs are evaluated. This project focused on the spar arrangement and material used for the wings that could achieves improved performance. Various lift and thrust measurement techniques are explored and evaluated. Various wings of insects and birds were evaluated to understand how these natural flyers with flapping wings are able to produce sufficient lift to fly. The differences in the flapping aerodynamics were also detailed. Experiments on different wing designs and materials were conducted and a paramount wing was built for test flight. The final prototype has a length of 46.5 cm, wing span of 88 cm, and weighs 161 g. A mechanism which produced flapping motion was fabricated and designed to create flapping flight. The flapping flight was produced by using a single motor and a flexible and light wing structure...
Journal of Alloys and Compounds, 2018
Electrodeposition of a thin ferromagnetic film with excellent magnetic dynamic properties at giga... more Electrodeposition of a thin ferromagnetic film with excellent magnetic dynamic properties at gigahertz range is challenging due to the easy oxidation of the active metals. Hence developing a feasible method to decrease the oxidation upon understanding the oxidation mechanism during the electrodeposition is critical. Here we report a simple methodology to successfully electrodeposit thin magnetic soft FeCo films with large complex permeability and high resonant frequency by means of inert gas-purging in the plating solution. The study of mechanism on the electrodeposition of active FeCo films depicts that the purging of inert N2 largely reduces the oxygen content in the plating solution, which subsequently suppresses the oxidation of iron ions, increases the Fe-atom ratio, and also perturbs the crystal growth of the as-deposited FeCo film. This in turn leads to the thin film with significantly reduced oxygen content, smaller grain size, and lower crystallinity, hence increased magnet...
This paper explores the feasibility of using the predictive control strategy to design the latera... more This paper explores the feasibility of using the predictive control strategy to design the lateral flight controller for a fixed-wing unmanned aerial vehicle (UAV). One of the primary features of predictive control is the control theory’s ability to consider the future implication of current control actions by explicitly computing the predicted system response over a finite horizon, i.e. the receding horizon control strategy. The optimal control input is then determined by optimizing some measure of predicted performance. Another important advantage that comes with the receding horizon strategy is the ability to respect constraints imposed upon the control inputs, state and output variables. The systematic handling of constraint violations is achieved by solving a constrained optimization problem, e.g. the quadratic programming (QP) problem at each sampling instant. The capability makes the predictive control highly appealing in the design of flight controllers for aircraft. The con...
We describe our novel hybrid design between flapping wing and fixed wing that is capable of susta... more We describe our novel hybrid design between flapping wing and fixed wing that is capable of sustained and controlled flight. The design of flapping wing micro air vehicle (FWMAV) combines two flapping wings and two fixed wings to take advantage of clap-and-fling effects at the end of each half flapping stroke for high thrust production as well as dynamic flight stability of the FW-MAV. Equipped with an onboard radio control system, which consists of a radio receiver, an electronic speed control (ESC), two servos for attitude flight control, and a single cell 3.7V/70mAh lithium polymer (LiPo) battery, the FW-MAV (14.6 grams, 22 cm tip-to-tip wing span) can demonstrate hovering flight, and sustained and controlled flight of about three minutes. Force measurement indicated that the FW-MAV produces thrust of 14.76 grams for liftoff at 10 Hz, and flaps at maximal frequency of 12.4 Hz with cycleaverage vertical thrust of about 23.52 grams. The effect of wing claps at dorsal and ventral si...
Study was conducted on the effect of wing root angle deflection to pave the way for the implement... more Study was conducted on the effect of wing root angle deflection to pave the way for the implementation of tailless flight control on a hovering flapping wing platform. Hypotheses of how the wing root deflection in the sagittal direction could help generate pitching and yawing moments are presented and investigated. The investigation was completed using a four bar linkage crank-rocker flapping mechanism. The flapping frequencies are from 13Hz to 18Hz, and the sagittal deflection angle ranged between -6.7o to 7o. Study shows that tailless pitch and yaw control is feasible but the nonlinearities could lead to huge challenge on implementation. The deflection angle also compromises lift.
AIAA Scitech 2020 Forum, 2020
Science Robotics, 2020
An ornithopter hovers, darts, turns rapidly, and pulls up from a dive by blending paraglider, air... more An ornithopter hovers, darts, turns rapidly, and pulls up from a dive by blending paraglider, airplane, and helicopter characteristics.
Journal of Bionic Engineering, 2019
The purpose of this research is to understand the aerodynamics of Flapping wing Micro Aerial Vehi... more The purpose of this research is to understand the aerodynamics of Flapping wing Micro Aerial Vehicles (FMAVs) flying in V-formation and how V-formation can improve the endurance of FMAVs. We tested FMAVs with two types of flapping kinematics: (1) idealized sinusoidal flapping/pitching motion, (2) actual FMAV wing deformation capture. Using the design of experiment methodology, together with an immersed boundary method numerical solver, we investigate the effects of phase angle and x, y, z separation between the wings on the FMAVs’ performance. Results show that it is possible to obtain an overall thrust and lift improvement of up to 25% and 14% respectively, or a reduction of both 19%, compared to the single wing configuration. Lastly, for certain cases, we extend another row, leading to a total of five wings. Results show that in general, the additional thrust or lift experienced by the second row of wings is also experienced by the third row of wings. Hence, this may apply to subsequent rows too.
The Journal of Instrumentation, Automation and Systems, 2016
A preliminary study on the stability of a bi-flap flapping wing hovering platform is presented in... more A preliminary study on the stability of a bi-flap flapping wing hovering platform is presented in this paper. The work includes the derivation of cycle-average linear longitudinal and lateral models, the experiment to determine the stability derivatives, and analysis on the identified system matrices. Also discussed in the paper is the validity of using a cycle-averaged model to represent the dynamics of the flapping wing platform, and the validity of using small perturbation theory to linearize the nonlinear model. Results show that the platform is unstable longitudinally and laterally about the hovering equilibrium. Longitudinally, the natural modes are short period unstable oscillatory mode, fast subsidence mode, and slow divergent mode. Laterally, the natural modes are neutral mode, fast subsidence mode, and long period unstable oscillatory mode.
Journal of Mechanisms and Robotics, 2018
Elastic storage has been reported to help flying insects save inertial power when flapping their ... more Elastic storage has been reported to help flying insects save inertial power when flapping their wings. This motivates recent research and development of elastic storage for flapping-wing micro air vehicles (fwMAVs) and their ground (tethered) flight tests. The previous designs of spring-loaded transmissions are relatively heavy or bulky; they have not yet been adopted by freely hovering prototypes of fwMAVs, especially those with four flapping wings. It is not clear if partial elastic storage can still help save power for flapping flight while not overloading the motorized transmission. Here, we developed ultralight and compact film hinges as elastic storage for four flapping wings. This spring-assisted transmission was motor driven such that the wing beat frequency was higher than the natural frequency of elastically hinged wings. Our experiments show that spring recoil helps accelerate wing closing thus generating more thrust. When powered by a 3.18 g brushless motor, this 13.4 g...
Bioinspiration & Biomimetics, 2018
The tailless flapping-wing micro air vehicle (FW-MAV) is one of the most challenging problems in ... more The tailless flapping-wing micro air vehicle (FW-MAV) is one of the most challenging problems in flapping-wing design due to its lack of tail for inherent flight stability. It must be designed in such a way that it can produce proper augmented control moments modulated by a closed-loop attitude controller for active stabilization. We propose a tailless FW-MAV with a wing stroke plane modulation mechanism, namely NUS-Roboticbird, which maneuvers by only using its flapping wings for both propulsion and attitude control. The flying vehicle has four wings comprised by two pairs, and each pair of wings and its stroke plane are driven by a motor and a servo, respectively. Attitude control moments of roll, pitch and yaw are generated by vectoring a pair of thrusts, which result from changing the flapping frequency (or motor speed) and wing stroke plane of the two pairs of wings. Free-flight tests show that the vehicle can climb and descend vertically (throttle control), fly sideways left and right (roll control), fly forwards and backwards (pitch control), rotate clockwise and counter-clockwise (yaw control), hover in mid-air (active self-stabilization), and maneuver in the figure-of-8 and fast forward/backward flight. These abilities are especially important for surveillance and autonomous flight in terms of obstacle avoidance in an indoor environment. Flight test data show that an effective mechanical control mechanism and control gains for attitude-controlled flights for roll, pitch and yaw are achieved, in particular, yaw control. Currently, the vehicle weighing 31 g and having a wingspan of 22 cm can perform fast forward flight at a speed of about 5 m s-1 (18 km h-1) and endure 3.5 min in flight with a useful payload of a 4.5 g onboard camera for surveillance.
AIAA Journal, 2018
This work investigates the acoustic and thrust performance of different wing designs for a two-wi... more This work investigates the acoustic and thrust performance of different wing designs for a two-winged flapping-wing micro air vehicle (FW-MAV). The reference wings, made of a Mylar film membrane supported by carbon-fiber rods, produce a perceived overall noise of about 68.8 dBA when operating at the flapping frequency of 10 Hz typically required for
Journal of Bionic Engineering, 2016
Hovering ability is one of the most desired features in Flapping-Wing Micro Air Vehicles (FW-MAVs... more Hovering ability is one of the most desired features in Flapping-Wing Micro Air Vehicles (FW-MAVs). This paper presents a hybrid design of flapping wing and fixed wing, which combines two flapping wings and two fixed wings to take advantage of the double wing clap-and-fling effect for high thrust production, and utilizes the fixed wings as the stabilizing surfaces for inherently stable hovering flight. Force measurement shows that the effect of wing clap-and-fling significantly enhances the cycle-averaged vertical thrust up to 44.82% at 12.4 Hz. The effect of ventral wing clap-and-fling due to presence of fixed wings produces about 11% increase of thrust-to-power ratio, and the insect-inspired FW-MAV can produce enough cycle-averaged vertical thrust of 14.76 g for lift-off at 10 Hz, and 24 g at maximum frequency of 12.4 Hz. Power measurement indicates that the power consumed for aerodynamic forces and wing inertia, and power loss due to gearbox friction and mechanism inertia was about 80% and 20% of the total input power, respectively. The proposed insect-inspired FW-MAV could endure three-minute flight, and demonstrate a good flight performance in terms of vertical takeoff , hovering, and control with an onboard 3.7 V-70 mAh LiPo battery and control system.
Aerospace, 2015
In this paper, an ornithopter prototype that mimics the flapping motion of bird flight is develop... more In this paper, an ornithopter prototype that mimics the flapping motion of bird flight is developed, and the lift and thrust generation characteristics of different wing designs are evaluated. This project focused on the spar arrangement and material used for the wings that could achieves improved performance. Various lift and thrust measurement techniques are explored and evaluated. Various wings of insects and birds were evaluated to understand how these natural flyers with flapping wings are able to produce sufficient lift to fly. The differences in the flapping aerodynamics were also detailed. Experiments on different wing designs and materials were conducted and a paramount wing was built for a test flight. The first prototype has a length of 46.5 cm, wing span of 88 cm, and weighs 161 g. A mechanism which produced a flapping motion was fabricated and designed to create flapping flight. The flapping flight was produced by using a single motor and a flexible and light wing structure. A force balance made of load cell was then designed to measure the thrust and lift force of the ornithopter. Three sets of wings varying flexibility were fabricated, therefore lift and thrust measurements were acquired from each different set of wings. The lift will be measured in ten cycles computing the average lift and frequency in three different speeds or frequencies (slow, medium and fast). The thrust measurement was measure likewise but in two cycles only. Several observations were made regarding the behavior of flexible flapping wings that should aid in the design of future flexible flapping wing vehicles. The wings angle or phase characteristic were analyze too and studied.
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Papers by Woei-Leong Chan