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This work introduces a Central Pattern Generator (CPG)-based control formulation for a dual-winged nature-inspired Unmanned Aerial Vehicle (UAV). Unlike majority of the current popular configurations of UAVs such as multirotors and fixed-wing aircraft, this particular nature-inspired UAV generates lift by spinning its entire body about a central axis. This inherent oscillatory nature makes this particular type of UAV suitable for the implementation of a CPG-based controller, which also possess oscillatory characteristics. The CPG handles the low-level actuator commands given a simple higher-level input. Policy Gradients with Parameter-based Exploration (PGPE) was used to optimize the CPG parameters to obtain the desired UAV motion from the CPG inputs. A Tip Path Plane (TPP) angle controller was added on top of the CPG to form a TPP-CPG controller, in which closed-loop position control was implemented above this. Hovering and trajectory tracking tests were successfully conducted and the performance of the control strategy was verified.

In this work, reinforcement learning is used to develop a position controller for an underactuated natureinspired Unmanned Aerial Vehicle (UAV). This particular configuration of UAVs achieves lift by spinning its entire body contrary to standard multi-rotors or fixed-wing aircraft. Deep Deterministic Policy Gradients (DDPG) with Ape-X Distributed Prioritized Experience Replay was used to train neural network function approximators that were implemented as the final control policy. The reinforcement learning agent was trained in simulations and directly ported over to real-life hardware. Position control tests were performed on the learned control policy and compared to a baseline PID controller. The learned controller was found to exhibit better control over the inherent oscillations that arise from the non-linear dynamics of the platform.

First presented in 2017, the Transformable HOvering Rotorcraft (THOR) is a structurally efficient hybrid Unmanned Aerial Vehicle (UAV) design that uses a dual servo, dual motor configuration to hover as a nature-inspired monocopter and cruise as a delta shaped fixed-wing. Such a design has potential applications in disaster relief, agriculture and surveillance; scenarios where it is desirable for the UAV to be able to both travel long distances fast and hover for long periods of time. To improve on the 2017 design, we propose the replacement of the existing dual servo system with a high torque, high precision central servo system and a controllable flap on each wing. Through simulation and experimental data, we argue that these would improve the system's flight characteristics while also giving it the ability to fly in a third mode, as a dual motor, dual flap tailsitter UAV.

Hybrid aerial vehicles which combine two or more flight configurations have gained popularity due to their increased flight envelope and versatility. With the inclusion of two or more flight modes, the transition phases between these modes are equally as crucial. While many have worked on the transition phases of more popular hybrid aerial vehicle configurations, this paper builds upon a novel aerial platform that combines the maneuverability and hover capability of a rotor-wing with the speed and endurance of a fixed-wing aircraft, previously established as the Transformable HOvering Rotorcraft (THOR). THOR uses a structurally efficient combination of a single-axis rotor (monocopter) type with a tailless fixed wing configuration, utilizing all flight surfaces in both modes. The hover-to-cruise transition of THOR is explored in the form of a trajectory optimization problem. The formulation of the cost function, vehicle model, and constraints are discussed in this paper. The open-loop control inputs that minimize the objective function were determined, simulated and flight tested experimentally.

This paper describes the Transformable HOvering Rotorcraft (THOR), a prototype Unmanned Aerial Vehicle (UAV) that explores a novel approach in combining the range and speed of a horizontal flying platform with the hovering and maneuverability of a rotor-wing. This is achieved by integrating a tailless flying wing configuration with a single-axis rotor, or monocopter. By maintaining full utilization of all aerodynamic surfaces and propulsion sources in both flight modes, this method represents the most structurally efficient approach to achieving a cruising mode and a hovering mode on the same frame. Using a dual servo and motor configuration, we propose an under-actuated system that is able to achieve controllability in 4 degrees of freedom while in its horizontal cruising mode and in 5 degrees of freedom while in its hovering mode. In both indoor and outdoor experiments, the UAV is able to transition between either flight modes seamlessly and repeatedly without the need for any additional mechanisms and actuators.