Dynamically controlled flight altitudes in robo-pigeons via locus coeruleus neurostimulation

Background

Robo-pigeon / Cyborg pigeon is a new type of hybrid intelligent robotic system developed by combining micro-implantable brain-computer interface (BCI) and micro-electro-mechanical system (MEMS) technologies. By integrating the perception, motion and autonomous intelligence of real pigeons with the high precision, repeatability and controllability of MEMS, a flexible and efficient "biological flight platform" is formed, which has a broad application prospect in key fields such as disaster rescue, national defense security and environmental monitoring.

However, the precise and reliable control of the flight behavior of pigeon robots in the outdoor environment is still a difficult challenge, especially the control of flight altitude. The flight altitude not only directly affects the navigation ability of pigeon robots in complex three-dimensional space, but also is closely related to their adaptability, stability, and success rate of mission execution in dynamic environments. Therefore, realizing the precise control of the flight altitude of pigeon robots is the core of animal robots to go out of the laboratory and work in outdoor environments.

Research Progress

In order to solve the difficult problem of pigeon robots in outdoor flight altitude control, Prof. Zhendong Dai's team at the School of Electromechanics, Nanjing University of Aeronautics and Astronautics (NUAA), has started an in-depth cooperation with the Brain-Computer Interface and Fusion Intelligence team at the Institute of Automation, Chinese Academy of Sciences (CASIA). For the first time, the research team has expanded the research on flight control of pigeon robots from indoor to outdoor real flight environments, and proposed a quantitative neural stimulation method based on the Locus Coeruleus (LoC) of pigeon midbrain; the research team systematically explored the effects of three key parameters, namely stimulation frequency (SF), stimulation interval (ISI), and stimulation cycle (SC) on the flight altitude control of pigeon robots. (Fig. 1)

Results indicated that stimulation frequency (SF) functions as a critical "switch" determining the pigeon's flight mode (ascending or descending). At 60 Hz SF, pigeons exhibited an average ascent of 12.241 meters with an effectiveness rate of 87.72%, whereas at 80 Hz SF, they displayed an average descent of 15.655 meters with an effectiveness rate of 90.52% (Fig. 2). In contrast, frequencies below 40 Hz had minimal impact on altitude, while frequencies above 100 Hz tended to destabilize flight. Furthermore, the study revealed that increasing the number of stimulation cycles (SC) directly amplified altitude adjustments, allowing for quantifiable and controlled altitude changes. Although the inter-stimulus interval (ISI) had a less direct impact on altitude, it significantly affected flight velocity and neural fatigue levels (Fig. 3). Properly extending the ISI effectively reduced neural fatigue, optimizing the balance between response sensitivity and flight stability. Notably, stimulation of the LoC nucleus did not significantly alter flight direction, enabling pigeons to maintain their original heading during altitude changes, thus offering a viable method for independently controlling altitude without disrupting horizontal navigation.

This study is the first to clearly demonstrate the potential of targeted electrical stimulation of the LoC nucleus for precise altitude control in cyborg pigeons, establishing foundational theories and technical approaches for controlled animal flight operations.

Future Prospects

In the foreseeable future, cyborg pigeon technology holds promising opportunities across diverse fields. Equipped with cameras and sensors, these pigeons could perform search and rescue operations by exploiting their agility and autonomous obstacle-avoidance capabilities in hazardous terrains or disaster sites. For environmental monitoring and urban inspections, they can undertake prolonged flights and collect multi-dimensional data in real-time, thus enhancing environmental information networks. In defense and security applications, their inconspicuous appearance and adaptive flying capabilities are advantageous for front-line reconnaissance and communication relay missions in high-risk environments.

Most importantly, the brain-computer interface and closed-loop control methods developed through cyborg pigeons offer significant inspiration for designing semi-biological drones or advanced bio-inspired flying machines. By deepening our understanding of neural control mechanisms in flying animals, we can refine flight control algorithms and simultaneously gain deeper insights into avian physiology and neuroscience. With continuous technological advancements, cyborg pigeons are poised to expand their practical roles, becoming innovative platforms that integrate biological and engineering systems.

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