Enhancing disturbance rejection capability and body jerk performance of a twin-rotor helicopter model using intelligent active force control

This paper presents a study on the effectiveness of utilizing an innovative control approach based on an intelligent active force control (IAFC) strategy to stabilize a twin-rotor helicopter model and improve its ability to effectively reject external disturbances via a simulation work. A detailed mathematical model of a two-degree-of-freedom (DOF) helicopter was derived using the Euler-Lagrange method taking into account the effects of coupling and disturbances. In this developed model, a Proportional–Integral–Derivative (PID) controller was designed and combined with the proposed IAFC strategy to yield an intelligent hybrid control architecture known as a PID-IAFC scheme that can improve system performance and reject various types of applied disturbances. The intelligent algorithms used in the schemes are based on iterative learning (IL) and fuzzy logic (FL). In this work, different types of external disturbances in the form of sinusoidal waves, pulsating, and random noise disturbances were applied to the helicopter system to verify the sensitivity and durability of the proposed control schemes and consequently, a comparative study was performed to analyze the system characteristics. Notably, the efficacy of the IAFC based control unit was investigated to improve the body jerk performance in the presence of external disturbances. The acquired results reveal the effectiveness and robustness of the IAFC based controller in stabilizing the dual-rotor helicopter, rejecting the applied disturbances, and improving the body jerk performance by at least 54% for pitching and 19% for yawing motions in the presence of the pulsating disturbance, and 60% and 54%, respectively, for the random noise disturbance

Hybrid active force control for fixed based rotorcraft

Disturbances are considered major challenges faced in the deployment of rotorcraft unmanned aerial vehicle (UAV) systems. Among different types of rotorcraft systems, the twin-rotor helicopter and quadrotor models are considered the most versatile flying machines nowadays due to their range of applications in the civilian and military sectors. However, these systems are multivariate and highly non-linear, making them difficult to be accurately controlled. Their performance could be further compromised when they are operated in the presence of disturbances or uncertainties. This dissertation presents an innovative hybrid control scheme for rotorcraft systems to improve disturbance rejection capability while maintaining system stability, based on a technique called active force control (AFC) via simulation and experimental works. A detailed dynamic model of each aerial system was derived based on the Euler–Lagrange and Newton-Euler methods, taking into account various assumptions and conditions. As a result of the derived models, a proportional-integral-derivative (PID) controller was designed to achieve the required altitude and attitude motions. Due to the PID's inability to reject applied disturbances, the AFC strategy was incorporated with the designed PID controller, to be known as the PID-AFC scheme. To estimate control parameters automatically, a number of artificial intelligence algorithms were employed in this study, namely the iterative learning algorithm and fuzzy logic. Intelligent rules of these AI algorithms were designed and embedded into the AFC loop, identified as intelligent active force control (IAFC)-based methods. This involved, PID-iterative learning active force control (PID-ILAFC) and PID-fuzzy logic active force control (PID-FLAFC) schemes. To test the performance and robustness of these proposed hybrid control systems, several disturbance models were introduced, namely the sinusoidal wave, pulsating, and Dryden wind gust model disturbances. Integral square error was selected as the index performance to compare between the proposed control schemes. In this study, the effectiveness of the PID-ILAFC strategy in connection with the body jerk performance was investigated in the presence of applied disturbance. In terms of experimental work, hardware-in-the-loop (HIL) experimental tests were conducted for a fixed-base rotorcraft UAV system to investigate how effective are the proposed hybrid PID-ILAFC schemes in disturbance rejection. Simulated results, in time domains, reveal the efficacy of the proposed hybrid IAFC-based control methods in the cancellation of different applied disturbances, while preserving the stability of the rotorcraft system, as compared to the conventional PID controller. In most of the cases, the simulated results show a reduction of more than 55% in settling time. In terms of body jerk performance, it was improved by around 65%, for twin-rotor helicopter system, and by a 45%, for quadrotor system. To achieve the best possible performance, results recommend using the full output signal produced by the AFC strategy according to the sensitivity analysis. The HIL experimental tests results demonstrate that the PID-ILAFC method can improve the disturbance rejection capability when compared to other control systems and show good agreement with the simulated counterpart. However, the selection of the appropriate learning parameters and initial conditions is viewed as a crucial step toward this improved performance