Customer requirements for unmanned aerial vehicles (UAVs) with long flight times are increasing exponentially in the personal, commercial, and military use areas. Due to their limited payload, large numbers of on-board battery packs cannot be used and this is the main reason behind the need for battery management software (BMS) packages with state of charge (SOC) estimation functions to increase the flight time. At the same time, as the UAV application range has extended widely, the size of UAVs has increased and heavy-duty UAVs are slowly appearing. As a result, the system operating power of the UAVs has been increased tremendously and their safe system power operation has become an issue. This is the main reason for the need of BMS having state of power (SOP) estimation functions. In this work a 6 S Li-Po battery pack is simulated with two ladder equivalent circuit models (ECMs) considering an impedance effect whose parameters are found using hybrid pulse power characterization (HPPC) current patterns with parameter determination using the table-based linear interpolation (TBLI) method. Two state estimation methods, including the current integration method and the extended Kalman filter (EKF) method are developed and the estimation accuracies of SOC and SOP are compared. Results show that the most accurate SOC estimation turns out to be 0.1477% (indoor test with HPPC), 0.1324% (outdoor test with 0 kg payload), and 0.2021% (outdoor test with 10 kg payload). Also, the most accurate SOP estimation error turns out to be 1.2% (indoor test with HPPC), 3.6% (outdoor test with 0 kg payload), and 4.2% (outdoor test with 10 kg payload).

This article proposes a wireless power transfer (WPT) system for variant receiver (Rx) configuration, power distribution ratio, load, and distance with multiple relays, each of which is connected to a resistive load. Each Rx relay transfers power to an adjacent Rx and acts as a relay while its local load consumes power. We develop a methodology for the design of WPT resonators that achieve optimum efficiency for multiple receivers with power distribution ratios, loads, and distances. The WPT configuration is extended to a general m×n, two-dimensional grid for a large area coverage. A mathematical model of the proposed WPT system is provided, and a multiple-Rx wireless power network using a power inverter serves as a proof-of-concept. Following the design guidelines provided in this article, experimental examples with variable parameters while delivering a total power of 100 W are discussed. To illustrate the practical applicability of this approach, a demonstration on a consumer display and speaker device is performed.

To achieve the continuous surveillance capable multirotor type solar-powered unmanned aerial vehicle (UAV), we develop the photovoltaic power management system (PPMS) which manages power from photovoltaic (PV) modules and a battery pack to support the power of the UAV. To estimate the possible flight time of the UAV, we use the concept of state of charge (SOC) estimation based on the extended Kalman filter (EKF) and complementary filter (CF) and then calculate the possible flight time by using the slope of the SOC graph during hovering flight mode. According to the results, estimated flight time increases up to 54.14 min at 11:00 a.m. and decreases down to 6.70 min at 18:00 p.m.

In this study, we formulate and implement 14 widely used battery-equivalent circuit models (ECMs) in a MATLAB/Simulink environment and extract the parameters using the hybrid pulse power characterization (HPPC) test results based on the parameter estimator app working on the curve-fitting method. Using the extracted parameter values, which are either state of charge-dependent sixth-degree polynomials or constants, we perform an error fluctuation deviation analysis on two different real flight test results by loading 0 kg and 10 kg payloads on a hexacopter unmanned aerial vehicle for the ECM characteristic evaluation. According to the error characteristic analysis, the Liu ECM resulted in the lowest root mean square (RMS) (0.0376 V), standard deviation (0.0343 V), and maximum errors (0.6159 V) for the HPPC test, the Rint ECM resulted in the lowest RMS (0.0702 V) and maximum errors (0.6844 V) for the real flight test carrying a 0 kg payload, and the Shepherd ECM resulted in the lowest RMS (0.0875 V) and standard deviation errors (0.0872 V) for the real flight test carrying a 10 kg payload. In conclusion, we recommend the Shepherd ECM with constant parameters owing to its fast parameter optimization convergence time and flexibility to the dynamic discharging load with a smaller error.

For a continuous surveillance mission using a swarm of multiple tethered low-altitude long-endurance (LALE) multirotor-type unmanned aerial vehicles (UAVs), we developed a 500 W class photovoltaic power management system (PPMS) which monitors voltage and current flows of photovoltaic (PV) panels, battery pack, and UAV and controls power flows to support UAV flight operation. In contract to a fixed-wing UAV, a tethered multirotor UAV can generate continuously varying closed-circuit television (CCTV) like ground map images by stitching incoming images though the operation range is limited. With an indoor flight experiment, we demonstrated the usefulness of the PPMS and proved operation integrity. According to the results, a total of six multirotor UAVs were required to continuously perform a surveillance mission for 5 h 46 min from 11:04 to 16:50.