skip to main content

Search for: All records

Creators/Authors contains: "Papachristos, Christos"

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. This works deals with the problem of long-term autonomy in the context of multi-day field deployments of Micro Aerial Vehicle (MAV) systems. To truly depart from the necessity for human intervention for the crucial task of providing battery recharging, and to liberate from the need to operate in a confined range around specially installed infrastructure such as recharging pods, the MAV robot is required to harvest power on its own, but equally importantly also sustain prolonged periods of ambient power scarcity. This implies being able to sustain the battery charge overnight when using solar recharging, or even during multiple days of illumination inadequacy (e.g., due to degraded atmospheric lucidity and heavy overcast). We address this by presenting a Self-Sustainable Autonomous System architecture for MAVs centered around a specially tailored Power Management Stack, which is capable of achieving deep system hibernation, a feature that facilitates the aforementioned functionalities. We present a) continuous, b) multi-day successive, and c) externally-powered recharging that uses a legged robot-mounted Mobile Recharging Station. We conclude by demonstrating a challenging zero-intervention multi-day field deployment mission in the N.Nevada region. 
    more » « less
  2. Vertical Take-Off and Landing (VTOL) Unmanned Aerial Vehicles (UAVs) provide a versatile platform well-suited to applications requiring the efficiency of fixed-wing flight with the maneuverability of a multicopter. Prior work has introduced the concept of using solar energy harvesting using photovoltaic cells embedded in the wings of the vehicle to perform self-recharge in the field when landed and at rest. This work demonstrates a further extension of this concept by optimizing the VTOL aircraft for maximum input-to-output power ratio, such that continuous flight is possible for the majority of a typical day with good sunlight. By also adding amphibious design elements, a transoceanic flight cycle is proposed. The candidate aircraft design is shown with estimated and actual behavioral and performance data for hovering and forward flight. Artwork for design elements such as the tiltrotor nacelle design and interchangeable avionics pod are shown. 
    more » « less
  3. In this work we address the System-of-Systems reassembling operation of a marsupial team comprising a hybrid Unmanned Aerial Vehicle and a Legged Locomotion robot, relying solely on vision-based systems and assisted by Deep Learning. The target application domain is that of large-scale field surveying operations under the presence of wireless communication disruptions. While most real-world field deployments of multi-robot systems assume some degree of wireless communication to coordinate key tasks such as multi-agent rendezvous, a desirable feature against unrecoverable communication failures or radio degradation due to jamming cyber-attacks is the ability for autonomous systems to robustly execute their mission with onboard perception. This is especially true for marsupial air / ground teams, wherein landing onboard the ground robot is required. We propose a pipeline that relies on Deep Neural Network-based Vehicle-to-Vehicle detection based on aerial views acquired by flying at typical altitudes for Micro Aerial Vehicle-based real-world surveying operations, such as near the border of the 400ft Above Ground Level window. We present the minimal computing and sensing suite that supports its execution onboard a fully autonomous micro-Tiltrotor aircraft which detects, approaches, and lands onboard a Boston Dynamics Spot legged robot. We present extensive experimental studies that validate this marsupial aerial / ground robot’s capacity to safely reassemble while in the airborne scouting phase without the need for wireless communication. 
    more » « less
  4. In this work we address the flexible physical docking-and-release as well as recharging needs for a marsupial system comprising an autonomous tiltrotor hybrid Micro Aerial Vehicle and a high-end legged locomotion robot. Within persistent monitoring and emergency response situations, such aerial / ground robot teams can offer rapid situational awareness by taking off from the mobile ground robot and scouting a wide area from the sky. For this type of operational profile to retain its long-term effectiveness, regrouping via landing and docking of the aerial robot onboard the ground one is a key requirement. Moreover, onboard recharging is a necessity in order to perform systematic missions. We present a framework comprising: a novel landing mechanism with recharging capabilities embedded into its design, an external battery-based recharging extension for our previously developed power-harvesting Micro Aerial Vehicle module, as well as a strategy for the reliable landing and the docking-and-release between the two robots. We specifically address the need for this system to be ferried by a quadruped ground system while remaining reliable during aggressive legged locomotion when traversing harsh terrain. We present conclusive experimental validation studies by deploying our solution on a marsupial system comprising the MiniHawk micro tiltrotor and the Boston Dynamics Spot legged robot. 
    more » « less