Closed-Loop Control of Constrained Flapping Wing Micro Air Vehicles

Micro air vehicles are vehicles with a maximum dimension of 15 cm or less, so they are ideal in confined spaces such as indoors, urban canyons, and caves. Considerable research has been invested in the areas of unsteady and low Reynolds number aerodynamics, as well as techniques to fabricate small scale prototypes. Control of these vehicles has been less studied, and most control techniques proposed have only been implemented within simulations without concern for power requirements, sensors and observers, or actual hardware demonstrations. In this work, power requirements while using a piezo-driven, resonant flapping wing control scheme, Bi-harmonic Amplitude and Bias Modulation, were studied. In addition, the power efficiency versus flapping frequency was studied and shown to be maximized while flapping at the piezo-driven system\u27s resonance. Then prototype hardware of varying designs was used to capture the impact of a specific component of the flapping wing micro air vehicle, the passive rotation joint. Finally, closed-loop control of different constrained configurations was demonstrated using the resonant flapping Bi-harmonic Amplitude and Bias Modulation scheme with the optimized hardware. This work is important in the development and understanding of eventual free-flight capable flapping wing micro air vehicle

Flying Drosophila stabilize their vision-based velocity controller by sensing wind with their antennae

Flies and other insects use vision to regulate their groundspeed in flight, enabling them to fly in varying wind conditions. Compared with mechanosensory modalities, however, vision requires a long processing delay (~100 ms) that might introduce instability if operated at high gain. Flies also sense air motion with their antennae, but how this is used in flight control is unknown. We manipulated the antennal function of fruit flies by ablating their aristae, forcing them to rely on vision alone to regulate groundspeed. Arista-ablated flies in flight exhibited significantly greater groundspeed variability than intact flies. We then subjected them to a series of controlled impulsive wind gusts delivered by an air piston and experimentally manipulated antennae and visual feedback. The results show that an antenna-mediated response alters wing motion to cause flies to accelerate in the same direction as the gust. This response opposes flying into a headwind, but flies regularly fly upwind. To resolve this discrepancy, we obtained a dynamic model of the fly’s velocity regulator by fitting parameters of candidate models to our experimental data. The model suggests that the groundspeed variability of arista-ablated flies is the result of unstable feedback oscillations caused by the delay and high gain of visual feedback. The antenna response drives active damping with a shorter delay (~20 ms) to stabilize this regulator, in exchange for increasing the effect of rapid wind disturbances. This provides insight into flies’ multimodal sensory feedback architecture and constitutes a previously unknown role for the antennae

DESIGN AND CONTROL OF A HUMMINGBIRD-SIZE FLAPPING WING MICRO AERIAL VEHICLE

Flying animals with flapping wings may best exemplify the astonishing ability of natural selection on design optimization. They evince extraordinary prowess to control their flight, while demonstrating rich repertoire of agile maneuvers. They remain surprisingly stable during hover and can make sharp turns in a split second. Characterized by high-frequency flapping wing motion, unsteady aerodynamics, and the ability to hover and perform fast maneuvers, insect-like flapping flight presents an extraordinary aerial locomotion strategy perfected at small size scales. Flapping Wing Micro Aerial Vehicles (FWMAVs) hold great promise in bridging the performance gap between engineered flying vehicles and their natural counterparts. They are perfect candidates for potential applications such as fast response robots in search and rescue, environmental friendly agents in precision agriculture, surveillance and intelligence gathering MAVs, and miniature nodes in sensor networks

Roll, Pitch and Yaw Torque Control for a Robotic Bee

In the last decade, the robotics community has pushed to develop increasingly small, autonomous flapping-wing robotic vehicles for a variety of civilian and military applications. The miniaturization of these vehicles has pushed the boundaries of technology in many areas, including electronics, artificial intelligence, and mechanics; as well as our understanding of biology. In particular, at the insect scale, fabrication, actuation, and flight control of a flapping-wing robot become especially challenging. This thesis addresses these challenges in the context of the “RoboBee” project, which has the goal of creating an autonomous swarm of at-scale robotic bees. A 100mg robot with a 3cm wingspan capable of generating roll, pitch and yaw torques in the range of $\pm 1\mu Nm$ by using a large, central power actuator to flap the wings and smaller control actuators to steer is presented. A dynamic model is used to predict torque generation capabilities, and custom instrumentation is developed to measure and characterize the vehicle’s control torques. Finally, controlled flight experiments are presented, and the vehicle is capable of maintaining a stable pitch and roll attitude during ascending vertical flight. This is the first successful controlled flight of a truly insect-scale flapping-wing robot.Engineering and Applied Science

Mechanical design and manufacturing of an insect-scale flapping-wing robot

Despite the prevalence of insect flight as a form of locomotion in nature, manmade aerial systems have yet to match the aerial prowess of flying insects. Within a tiny body volume, flying insects embody the capabilities to flap seemingly insubstantial wings at very high frequencies and sustain beyond their own body weight in flight. A precise authority over their wing motions enables them to respond to obstacles and threats in flight with unrivaled speed and grace. Motivated by a desire for comparably agile flying machines, research efforts in the last decade have generated crucial developments for realizing an artificial instantiation of insect flight. The need for tiny, high-efficiency mechanical components has produced unconventional solutions for propulsion, actuation, and manufacturing. Early vehicle designs proved to be flightworthy but were critically limited by the inability to produce control torques in flight. In this thesis, we synthesize all existing technologies for insect-scale manufacturing and actuation, and we introduce a new vehicle design, the "dual actuator bee," to address the need for flight control. Our work culminates in the first demonstration of controlled, hovering flight of an insect-scale, flapping-wing robot. As the ultimate goal for this research effort is the creation of fully autonomous flying robots, these vehicles must sustain their own power sources and intelligence. To that end, we explore the challenges of scaling flapping-wing flight to attain greater lift forces. Using a scaling heuristic to determine key vehicle specifications, we develop and successfully demonstrate a hover-capable vehicle design that possesses the requisite payload capacity for the full suite of components required for control autonomy. With this operational vehicle as a point of reference, we introduce an iterative sizing procedure for specifying a vehicle design with payload capacity capable of supporting power autonomy. In the development of these vehicles, the reliability of their construction has been a substantial challenge. We present strategies for systematically addressing issues of vehicle construction. Together, this suite of results demonstrates the feasibility of achieving artificial, insect-like flight.Engineering and Applied Sciences - Engineering Science

Optimizing the structure and movement of a robotic bat with biological kinematic synergies

In this article, we present methods to optimize the design and flight characteristics of a biologically inspired bat-like robot. In previous, work we have designed the topological structure for the wing kinematics of this robot; here we present methods to optimize the geometry of this structure, and to compute actuator trajectories such that its wingbeat pattern closely matches biological counterparts. Our approach is motivated by recent studies on biological bat flight that have shown that the salient aspects of wing motion can be accurately represented in a low-dimensional space. Although bats have over 40 degrees of freedom (DoFs), our robot possesses several biologically meaningful morphing specializations. We use principal component analysis (PCA) to characterize the two most dominant modes of biological bat flight kinematics, and we optimize our robot’s parametric kinematics to mimic these. The method yields a robot that is reduced from five degrees of actuation (DoAs) to just three, and that actively folds its wings within a wingbeat period. As a result of mimicking synergies, the robot produces an average net lift improvesment of 89% over the same robot when its wings cannot fold

Proceedings of the International Micro Air Vehicles Conference and Flight Competition 2017 (IMAV 2017)

The IMAV 2017 conference has been held at ISAE-SUPAERO, Toulouse, France from Sept. 18 to Sept. 21, 2017. More than 250 participants coming from 30 different countries worldwide have presented their latest research activities in the field of drones. 38 papers have been presented during the conference including various topics such as Aerodynamics, Aeroacoustics, Propulsion, Autopilots, Sensors, Communication systems, Mission planning techniques, Artificial Intelligence, Human-machine cooperation as applied to drones

Microrobots for wafer scale microfactory: design fabrication integration and control.

Future assembly technologies will involve higher automation levels, in order to satisfy increased micro scale or nano scale precision requirements. Traditionally, assembly using a top-down robotic approach has been well-studied and applied to micro-electronics and MEMS industries, but less so in nanotechnology. With the bloom of nanotechnology ever since the 1990s, newly designed products with new materials, coatings and nanoparticles are gradually entering everyone’s life, while the industry has grown into a billion-dollar volume worldwide. Traditionally, nanotechnology products are assembled using bottom-up methods, such as self-assembly, rather than with top-down robotic assembly. This is due to considerations of volume handling of large quantities of components, and the high cost associated to top-down manipulation with the required precision. However, the bottom-up manufacturing methods have certain limitations, such as components need to have pre-define shapes and surface coatings, and the number of assembly components is limited to very few. For example, in the case of self-assembly of nano-cubes with origami design, post-assembly manipulation of cubes in large quantities and cost-efficiency is still challenging. In this thesis, we envision a new paradigm for nano scale assembly, realized with the help of a wafer-scale microfactory containing large numbers of MEMS microrobots. These robots will work together to enhance the throughput of the factory, while their cost will be reduced when compared to conventional nano positioners. To fulfill the microfactory vision, numerous challenges related to design, power, control and nanoscale task completion by these microrobots must be overcome. In this work, we study three types of microrobots for the microfactory: a world’s first laser-driven micrometer-size locomotor called ChevBot，a stationary millimeter-size robotic arm, called Solid Articulated Four Axes Microrobot (sAFAM), and a light-powered centimeter-size crawler microrobot called SolarPede. The ChevBot can perform autonomous navigation and positioning on a dry surface with the guidance of a laser beam. The sAFAM has been designed to perform nano positioning in four degrees of freedom, and nanoscale tasks such as indentation, and manipulation. And the SolarPede serves as a mobile workspace or transporter in the microfactory environment

Optimizing the structure and movement of a robotic bat with biological kinematic synergies

In this article, we present methods to optimize the design and flight characteristics of a biologically inspired bat-like robot. In previous, work we have designed the topological structure for the wing kinematics of this robot; here we present methods to optimize the geometry of this structure, and to compute actuator trajectories such that its wingbeat pattern closely matches biological counterparts. Our approach is motivated by recent studies on biological bat flight that have shown that the salient aspects of wing motion can be accurately represented in a low-dimensional space. Although bats have over 40 degrees of freedom (DoFs), our robot possesses several biologically meaningful morphing specializations. We use principal component analysis (PCA) to characterize the two most dominant modes of biological bat flight kinematics, and we optimize our robot’s parametric kinematics to mimic these. The method yields a robot that is reduced from five degrees of actuation (DoAs) to just three, and that actively folds its wings within a wingbeat period. As a result of mimicking synergies, the robot produces an average net lift improvesment of 89% over the same robot when its wings cannot fold

Mechanical Intelligence in Millimeter-Scale Machines

Advances in millimeter-scale fabrication processes have enabled rapid progress towards the development of flapping wing micro air vehicles with wing spans of several centimeters and a system mass on the order of 100mg. Concerning flight stability and control mechanisms for these mass and power limited devices, this dissertation explores the use of underactuated “mechanically intelligent” systems to passively regulate forces and torques encountered during flight. Several experiments demonstrate passive torque regulation in physical flapping wing systems. Finally, this dissertation concludes with a detailed description of the Printed Circuit MEMS manufacturing process, developed to address the practical problem of building complex insect-scale machines.Engineering and Applied Science