Current Issue : October-December Volume : 2023 Issue Number : 4 Articles : 5 Articles
Against the background of low-frequency vibration control for a helicopter fuselage in flight, active control of structural response (ACSR) has been employed for vibration control design. With the increase in control positions in the fuselage, more actuators and error sensors are needed to meet the vibration reduction requirements, forming a large-scale multichannel system. This leads to a rapid increase in the computation amount, causing the control performance of the conventional centralized algorithm main processor to become poor under overload operation. To this end, a novel distributed active vibration control algorithm based on the diffusion cooperative strategy was proposed and explored in this research. The diffusion cooperative strategy is widely used in complex wireless sensor network (WSN) systems to efficiently reduce the computation amount during data aggregation. This distributed algorithm utilizes the advantages of the diffusion-cooperative strategy to reduce the computation amount and coupling relationship of the secondary path in a large-scale multichannel system. First, a novel control law was established by introducing the network topology of the diffusion cooperation strategy into the classical filtered-x least mean square (FxLMS) algorithm, forming the diffusion FxLMS (DFxLMS) algorithm. Then, a secondary path trade-off quantization standard based on the complex undirected network connectivity condition was developed. It determined whether a secondary path was discarded or not and formed the topology of a large-scale multichannel system control network. To examine the effectiveness and superiority of the proposed DFxLMS algorithm, a comparative simulation with a scale of 1 × 10 × 10 was carried out for a simplified helicopter fuselage. Numerical results in realistic scenarios showed the ability of the DFxLMS algorithms to achieve good control performance when proper values of these parameters are chosen....
There is currently a lack of efficient heat transfer analysis methodologies for spiral channel regenerative cooling that has been increasingly applied in liquid rocket engines. To figure out the heat transfer characteristics of the spiral channel regenerative cooling thrust chamber, a simple 1D method based on the traditional semi-empirical formula after correcting the flow velocity is proposed. The accuracy of this approach is verified by the 3D numerical simulation. The verified method is further used to analyze the distribution of inner wall temperature in the test case and optimize the channel’s parameters. The research shows that the maximum inner wall temperature cooled by the spiral channel is 8.5% lower than that of the straight channel under the same channel size and boundary condition, indicating that the application of the spiral channel significantly improves the cooling effect. In addition, the 1D model combined with the second-order response surface model is employed to optimize the channel width, channel height, pitch, and inner wall thickness aiming for the best cooling effect. The calculated maximum temperature of the inner wall after the structure optimization is 586.6 K, which is 29.8% lower than the initial structure before optimization....
A novel homing guidance law against maneuvering targets based on the deep deterministic policy gradient (DDPG) is proposed. The proposed guidance law directly maps the engagement state information to the acceleration of the interceptor, which is an endto- end guidance policy. Firstly, the kinematic model of the interception process is described as a Markov decision process (MDP) that is applied to the deep reinforcement learning (DRL) algorithm. Then, an environment of training, state, action, and network structure is reasonably designed. Only the measurements of line-of-sight (LOS) angles and LOS rotational rates are used as state inputs, which can greatly simplify the problem of state estimation. Then, considering the LOS rotational rate and zero-effort-miss (ZEM), the Gaussian reward and terminal reward are designed to build a complete training and testing simulation environment. DDPG is used to deal with the RL problem to obtain a guidance law. Finally, the proposed RL guidance law’s performance has been validated using numerical simulation examples. The proposed RL guidance law demonstrated improved performance compared to the classical true proportional navigation (TPN) method and the RL guidance policy using deep-Q-network (DQN)....
The high-pressure gas cylinder is the pressure source for liquid propellant engine valve control. Leakage is a significant cause of pressure loss in gas cylinders, leading to engine control failure and serious flight accidents. In this paper, a model-based approach to estimate the leakage area and remaining useful life (RUL) of gas cylinders is proposed. To estimate the leakage area, a state space representation of the cylinder system is developed based on the nonlinear model derived from momentum, energy, and continuity equations. Leakage is defined as a system state, and an extended Kalman filter (EKF) as a state observer is implemented to estimate the leakage area. Internal pressure measurements of the gas cylinder are required as output parameters in the estimation process. Then, the estimated states are fed into the nonlinear model to iteratively calculate the RUL of the cylinder. To evaluate the effectiveness of the proposed method, scaling leakage test data, computational fluid dynamics (CFD) simulation results, and liquid rocket engine (LREs) hot test data are used. Calibration results have proved the validity and universality of the method, with the mean absolute error (MAE) for the remaining 80% useful life prediction results being less than 0.02, 0.04, and 1.10. This study can provide technical support for fault tolerance control and orbital replanning in case of control gas cylinder leaks....
The aircraft is subjected to high-temperature and high-pressure conditions during flight, which renders it susceptible to the occurrence of creep phenomenon. Several academics have conducted extensive research on this issue. This research paper provides a comprehensive overview of the existing literature on creep phenomena in aircraft engines. First, several classical creep calculation models are enumerated and categorized as creep life calculation, creep-fatigue life calculation, and creep deformation calculation. Studies on creep phenomena are conducted in various components of aircraft engines, such as the engine’s turbine blades, turbine disks, and combustion chambers. The creep behavior of turbine blades in aircraft engines has been extensively researched. Furthermore, the protective measures aimed at mitigating creep are presented. Materials with high creep resistance can be used, and alternative fuels could be implemented. This paper provides an in-depth analysis of the advantages of creep in aircraft, presented in a favorable perspective. Finally, the prospective future research direction is discussed....
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