Staging energy sources to extend flight time of a multirotor UAV

Abstract

Energy sources such as batteries do not decrease in mass after consumption, unlike combustion-based fuels. We present the concept of staging energy sources, i.e. consuming energy in stages and ejecting used stages, to progressively reduce the mass of aerial vehicles in-flight which reduces power consumption, and consequently increases flight time. A flight time vs. energy storage mass analysis is presented to show the endurance benefit for multirotors on staging. We consider two specific problems in discrete staging -optimal order of staging given a certain number of energy sources, and optimal partitioning of a given energy storage mass budget into a given number of stages. We then derive results for two continuously staged cases -an internal combustion engine driving propellers, and a rocket engine. A fundamental flight time limit is seen for the internal combustion engine case, but not for the rocket engine, suggesting that rocket engines could be a better choice in certain scenarios. Lastly, we conduct flight experiments a on a custom two-stage battery-powered quadcopter. This quadcopter can eject a battery stage after consumption in-flight using a custom-designed mechanism, and continue hovering using the next stage. The experimental flight times are compared with those predicted from the analysis for our vehicle. The values match well which validates the presented staging analysis.

Tethered Power Supply for Quadcopters: Architecture, Analysis and Experiments

“…3. (5) When the quadcopter is at hover vertically above x 0 , the total thrust equals the amount of force required to lift m Q and tether mass λl, f = (m Q + λl) g = mg, (6) Using the power analysis based on actuator disk model presented in [11], we claim that the electrical power consumption of the powertrain is,…”

“…Note that the left hand side of ( 11) is the power input to the quadcopter P Q at the end of the tether. We can substitute (7), ( 9) and ( 10) in (11) to get,…”

“…[10] are shown to extend the flight times more than 4 times. Other methods such as using the batteries in multiple stages [11] have also demonstrated increased flight times. However, these systems can run out of power if not replaced in time and would require the quadcopters to land.…”

“…The length of the portion of the tether in flight (not in contact with the ground) is l. At hover, we have the total thrust produced by the quadcopter in (1) as, f = m Q ge 3 − T . (5) When the quadcopter is at hover vertically above x 0 , the total thrust equals the amount of force required to lift m Q and tether mass λl, f = (m Q + λl) g = mg, (6) Using the power analysis based on actuator disk model presented in[11], we claim that the electrical power consumption of the powertrain is,P Q = c p m…”

Discharge Estimation with the Use of Unmanned Aerial Vehicles (UAVs) and Hydraulic Methods in Shallow Rivers

“…Weather conditions such as strong winds [55], rain [56] and air temperature [57] are major constraints that can alter the quality of surveys. In addition, the flight time of a UAV and consequently the temporal resolution of a mission are fundamentally limited by battery capacity and their quick depletion, an issue addressed by many researchers [58][59][60]. A set of other shortcomings is related to the fact that general market digital cameras are used for photogrammetry and remote sensing, resulting in illumination issues, image classification and relief displacement problems [61].…”