New UAV technology could revolutionize search and rescue

In a world where science fiction becomes reality, Dr. Fu Zhang, Assistant Professor of the Department of Mechanical Engineering at the Faculty of Engineering, the University of Hong Kong (HKU), has pioneered groundbreaking research that brings awe-inspiring scenes from movies like Prometheus to life. His innovation, the Powered-flying Ultra-underactuated LiDAR-Sensing Aerial Robot (PULSAR), is set to redefine the world of unpiloted aerial vehicles (UAVs).

UAVs already play a vital role in search and rescue operations, cave surveying, and architectural mapping. PULSAR takes UAV technology to new heights, drawing inspiration from the self-rotation and scanning pattern of astronomical pulsars. With its micro-computer and LiDAR sensor, PULSAR boasts onboard perception, mapping, planning, and control capabilities, all without the need for external instruments.

The key to PULSAR’s remarkable functionality lies in its single actuator, which powers the swashplateless mechanism, providing both thrust and moment. Through a series of experiments, Dr. Zhang’s team showcased PULSAR’s real-time detection of static and dynamic obstacles, ability to track complex trajectories, and autonomous navigation even in complete darkness.

PULSAR’s resilience extends to withstanding external wind disturbances, ensuring safer and more stable flights in unpredictable conditions. It can maintain its hover position within a small area at a maximum wind speed of 4.5 m/s, making it suitable for operation in challenging environments.

In addition to its existing capabilities, PULSAR’s sensor can extend its field of view (FoV) through self-rotation, enhancing the UAV’s perception and task efficiency. Currently, there are two main approaches to extending the sensor’s FoV, both of which consume significant power.

The first approach involves using sensors with large FoVs, such as fisheye cameras, catadioptric cameras, or 360° LiDAR, but these often result in distortions. While 360° LiDAR has a narrow and low-resolution FoV in the vertical direction. The second approach is to employ multiple sensors, like a multi-camera or multi-LiDAR system, but this incurs higher costs and longer data processing times.

PULSAR’s invention offers energy savings of 26.7% compared to a quadrotor UAV with the same propeller disk area and payload, while maintaining excellent agility. The single actuator propulsion system minimizes energy conversion loss, resulting in a high flight efficiency of 6.65g/W.

Despite its small size, with a diameter of only 37.6 cm and a battery capacity of 41 Wh, PULSAR, weighing 1234 grams, achieves a hover time of over 12 minutes. By removing the LiDAR sensor and replacing it with a larger propeller and battery, PULSAR’s hover time can be extended to more than 40 minutes.

The research findings have been published in Science Robotics.

Dr. Zhang believes that the research platform established by his team will facilitate further exploration of self-rotating UAVs. It holds great potential for advancing UAV control methods under high-speed rotation and simultaneous localization and mapping (SLAM) techniques during aggressive motion.

Source: The University of Hong Kong

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