Biomechanics Meets Aviation: A Nature-Inspired Leap in UAV Development
The Royal Melbourne Institute of Technology (RMIT) Uncrewed Aircraft Systems Research Team (RUASRT) set out to tackle a tough challenge: studying how kestrels master wind-hovering in turbulent conditions. Traditional tracking methods couldn’t provide the precise, high-speed kinematic data needed for Uncrewed Aerial Vehicle (UAV) stability research.
By implementing Qualisys’ motion capture system, they achieved remarkable results, tracking kestrels with just a 1.2 mm head deviation, even in high turbulence. These insights are advancing UAV design, improving their ability to handle turbulent environments.
The RMIT UAS Research Team, located in Melbourne, Australia, focuses on leveraging biomechanics to improve UAV stability under dynamic, turbulent conditions. Their pursuit of biologically inspired designs has turned to an unexpected but ingenious source of inspiration—kestrels. These remarkable birds perform wind-hovering maneuvers in turbulent environments, offering valuable insights that could enhance UAV performance.
Tracking the detailed subtleties of kestrel movement required a solution capable of extreme precision and the capacity to process large datasets in real time. To meet these demands, the team turned to Qualisys’ advanced motion capture system.
The wind tunnel features a test section measuring 9 meters long, 3 meters wide, and 2 meters high. Cameras were mounted to the walls and ceiling of the test section using ball joints on sliding rails, aimed at the center of the section where the birds fly. To create optimal tracking conditions, the interior surfaces of the wind tunnel—walls, floor, and ceiling—are painted matte black, and safety nets are installed to prevent the birds from reaching the fan.
The Challenge of Mimicking Nature's Precision
Wind-hovering is a hunting behavior observed in several bird species, including kestrels. During this behavior, birds fly into the wind at a speed that matches the wind velocity, allowing their heads to remain nearly stationary relative to the ground. This enables them to keep their vision steady while scanning for prey. Remarkably, kestrels in the wind tunnel maintained a head position with a standard deviation of just 1.2 mm under high turbulence conditions (12% turbulence intensity)—a level of precision far beyond that of current fixed-wing UAVs.
To better understand this stability, the team trained kestrels to wind-hover inside the tunnel and recorded their wing and tail movements using the Qualisys system.
Data were captured under smooth airflow, gusts, and high turbulence. Initial results, published in the links below, reveal key degrees of freedom and motion ranges used by kestrels for stabilization, along with evidence of control coupling and asymmetry.
Breaking Barriers with Biomechanical Innovation
To address their complex requirements, Qualisys offered a tailored motion capture solution combining unparalleled precision, adaptability to high turbulence, and ease of use. Key implementation aspects included:
Qualisys Motion Capture System
The mocap system, comprising 12 7+ cameras and 3 Miqus M5 cameras, was installed within RMIT’s 9-meter-long, turbulence-equipped wind tunnel.
Lightweight Reflective Markers
Kestrels were fitted with ultra-light, 1.5 mm reflective markers, ensuring over 50 data points per bird without affecting their natural movements.
High-Resolution & High Frame Rate
The Qualisys system delivered high-resolution and high frame rates – essential for tracking minute wing movements. It provided and reliable data with unmatched accuracy.
Seamless Workflow
The system’s user-friendly interface and synchronization with tools like MATLAB allowed intuitive data analysis and streamlined trajectory corrections.
The Path to Revolutionary Discoveries
By partnering with Qualisys, the RMIT UAS Research Team transformed their research capabilities, overcoming significant challenges in high-precision kinematic tracking and turbulence analysis. The insights enabled by this collaboration are not only advancing the field of biomechanics but also paving the way for revolutionary UAV designs inspired by nature.
The Qualisys system allowed us to quickly and easily capture high-resolution kinematics of wind-hovering kestrels. The system is streamlined and user-friendly, with helpful features that sped up our data capture and processing.
Dr. Abdulghani MohamedLead Researcher
With continued exploration and potential system upgrades, the team is poised to produce even more impactful discoveries.
