Aerodynamic Stability of Multipropulsors
Unmanned aerial vehicles, multipropulsors in particular, have in recent years established their position in scientific, industrial, and recreational applications. These robotic vehicles, colloquially referred to as drones, show great potential for scientific development spanning multiple disciplines. Currently, drones are used in lab-based settings for the systematic design and development of autonomous control infrastructure (including swarming and “decision-making” technologies), as these robots provide a flexible implementation platform for complex control algorithms. However, due to a lack of dedicated facilities, the inherent aerodynamic capabilities of these drones has yet to be thoroughly investigated.
To bridge this non-apparent research gap, the Gharib group is targeting two main research areas related to multipropulsor aerodynamics. Approximately 40% of a drone’s battery life is expended during descent and landing behavior. This is due to the fact that, while descending, the airflow around the drone introduces instabilities, which allow only a very moderate descent rate for stable flight. For this purpose, the Gharib Lab has designed a PIV (Particle Image Velocimetry) system specific for drone applications to analyze the flow around a descending quadcopter. Studies in this area are aimed to investigate the formation of these instabilities and the overall stability limits. Additionally, alterations to the quadcopter design will be explored, which may provide aerodynamic improvements.
ATLAS HEAVYLIFT
Caltech’s Center for Autonomous Systems and Technology (CAST) has been developing a novel, patented, compact heavy-lift vertical take-off and landing (VTOL) aircraft geared to service the emergency response and logistics sectors. The Department of Defense (DoD) considers “small” heavy-lift unmanned logistics solutions (ULS) to be vehicles that carry 60 to 150 pounds for 10 or 15 miles. “Medium” ULS are specified as those capable of carrying 300 to 500 pounds for 20 to 125 miles. Few viable drone technologies currently exist in the “small” and “medium” ULS specification. That deficit is only expected to grow given the performance expectations for dynamic flight environments. The issues limiting their development are primarily due to the scaling-up difficulties inherent to current fixed-pitch multirotor designs.
A relevant heavy-lift aerial platform must be robust, cost-effective, and practical amid austere weather environments if wide-scale adoption in the field is expected. Challenges that must be overcome include: the complexities associated with a plurality of rotors, the balancing of footprint with portability, and overall inefficient lift-to-weight ratios that inhibit maneuverability and reduce valuable mission time. CAST’s heavy-lift VTOL aircraft, the ATLAS series, attempts to tackle these challenges through the efficient lift of relevant payloads with a minimum footprint, making it an ideal aerial logistics platform for resupply and delivery with diverse applications such as:
Emergency services and firefighting
Humanitarian aid and disaster relief
Materials and ammunition for the military theater
Commercial package logistics
The ATLAS series heavy-lift drone significantly improves on existing drone industry payload performance through a patent-protected distributed variable pitch rotor design. By combining the hover-efficiency of a helicopter with the controllability of a multirotor, ATLAS 1 has demonstrated flight-capable payloads of higher than 100lbs, all in a compact vehicle footprint designed to fit in the back of a standard utility truck. Unique amongst its peers, ATLAS I can lift more than it weighs (weighing in at 98 lbs, batteries included), making it an ideal candidate for efficient point-to-point load pickup and drop-off.
The near-future objectives of ATLAS 1 include a targeted and representative flight demonstration to showcase its aerial firefighting logistical support. This includes primarily the ferrying of equipment loads in the dynamic and challenging wind-environments expected in a wildfire scenario. Technical challenges are being solved at full-scale to ensure applicability toward these highly relevant real-world scenarios. This video displays ATLAS 1 taking off and flying through a set of core maneuvers.