Pub Date : 2024-06-22DOI: 10.1177/09544100241263024
Jia Li, Bo Liu, Wen Zhou, Jian Xie, Xuan Chen
In the fuel system of an aircraft engine, aero-fuel centrifugal pumps are widely utilized as boost pumps. In this research, we propose the integration of an inlet injector with an aero-fuel centrifugal pump to optimize its flow characteristics and enhance performance. The key geometric parameters of the impeller, volute, and injector are meticulously designed. The effectiveness of our approach is validated through a combination of experimental and numerical analysis, which involves comparing simulation results with experimental data. The findings demonstrate that the presence of the injector significantly impacts the flow characteristics and hydraulic performance of the pump. Specifically, it effectively reduces flow losses in the specific channels of the impeller and volute. Furthermore, the injector enhances the regulation of the inlet flow fields by adjusting the inlet pressure and controlling the suction flow direction. Consequently, the pump’s efficiency is enhanced when equipped with the injector compared to its performance without it. Therefore, incorporating an injector in an aero-fuel centrifugal pump has a positive effect on regulating flow characteristics and improving hydraulic efficiency.
{"title":"Effect of injector on flow characteristic and hydraulic performance in aero-fuel centrifugal pump","authors":"Jia Li, Bo Liu, Wen Zhou, Jian Xie, Xuan Chen","doi":"10.1177/09544100241263024","DOIUrl":"https://doi.org/10.1177/09544100241263024","url":null,"abstract":"In the fuel system of an aircraft engine, aero-fuel centrifugal pumps are widely utilized as boost pumps. In this research, we propose the integration of an inlet injector with an aero-fuel centrifugal pump to optimize its flow characteristics and enhance performance. The key geometric parameters of the impeller, volute, and injector are meticulously designed. The effectiveness of our approach is validated through a combination of experimental and numerical analysis, which involves comparing simulation results with experimental data. The findings demonstrate that the presence of the injector significantly impacts the flow characteristics and hydraulic performance of the pump. Specifically, it effectively reduces flow losses in the specific channels of the impeller and volute. Furthermore, the injector enhances the regulation of the inlet flow fields by adjusting the inlet pressure and controlling the suction flow direction. Consequently, the pump’s efficiency is enhanced when equipped with the injector compared to its performance without it. Therefore, incorporating an injector in an aero-fuel centrifugal pump has a positive effect on regulating flow characteristics and improving hydraulic efficiency.","PeriodicalId":54566,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part G-Journal of Aerospace Engineering","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141505850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-21DOI: 10.1177/09544100241262550
Xi Li, Guoyuan Qi, Limin Zhang
For the first-order unstable object with time delay, the PD control parameter tuning method based on the traditional definition lacks consideration of the lower boundary of amplitude margin, resulting in a certain deviation between the result and the reality. In this paper, through analyzing the control loop of quadrotor UAV (QUAV), the integral link is moved from the controlled object to the controller, and the QUAV becomes a first-order unstable object, realizing the conversion of PD to PI in the hovering state. The system stability margin remains unchanged, and the position and attitude control objectives can be realized synchronously. By means of parameter setting method, the upper boundary of stability margin is obtained. Pade approximation is carried out for the time delay link, and then the lower margin of the amplitude margin is deduced according to Routh stability criterion, so as to obtain a more accurate reachable stability margin region. To avoid the high gain feedback of attitude angular velocity of QUAV, a numerical analytical setting formula for PD attitude control is derived to meet the requirements of gain and phase margin. The graph shows that the reachable region obtained by the strict definition of stability margin analysis decreases significantly. The proposed method can not only give the reachable region intuitively, but also give the tuning formula of the control parameters concisely, which has important engineering application value.
{"title":"Control stability analysis of dynamic model with time delay for quadrotor UAV","authors":"Xi Li, Guoyuan Qi, Limin Zhang","doi":"10.1177/09544100241262550","DOIUrl":"https://doi.org/10.1177/09544100241262550","url":null,"abstract":"For the first-order unstable object with time delay, the PD control parameter tuning method based on the traditional definition lacks consideration of the lower boundary of amplitude margin, resulting in a certain deviation between the result and the reality. In this paper, through analyzing the control loop of quadrotor UAV (QUAV), the integral link is moved from the controlled object to the controller, and the QUAV becomes a first-order unstable object, realizing the conversion of PD to PI in the hovering state. The system stability margin remains unchanged, and the position and attitude control objectives can be realized synchronously. By means of parameter setting method, the upper boundary of stability margin is obtained. Pade approximation is carried out for the time delay link, and then the lower margin of the amplitude margin is deduced according to Routh stability criterion, so as to obtain a more accurate reachable stability margin region. To avoid the high gain feedback of attitude angular velocity of QUAV, a numerical analytical setting formula for PD attitude control is derived to meet the requirements of gain and phase margin. The graph shows that the reachable region obtained by the strict definition of stability margin analysis decreases significantly. The proposed method can not only give the reachable region intuitively, but also give the tuning formula of the control parameters concisely, which has important engineering application value.","PeriodicalId":54566,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part G-Journal of Aerospace Engineering","volume":"217 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141513869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-21DOI: 10.1177/09544100241262559
Shengying Zhu, Chuncheng Zhao
Future exploration tasks of small bodies will need to sample or visit multiple points on the target to obtain more scientific returns, requiring rovers to have the ability to hop on a small body surface. This paper proposes an approach to generate a desensitized optimal trajectory for hopping rovers, aiming at reducing the sensitivity of hopping trajectory in the presence of uncertainties. Firstly, considering parameter uncertainties and initial state errors, analytical expressions of optimal initial states are derived on a planar scene, based on ballistic dynamics. Then, similar methods are developed in both uphill and downhill cases of inclined scenes. Subsequently, the desensitization performance of long-distance hopping trajectory is analyzed under single-hop, identical, and non-identical N-hop strategies. To facilitate the application of the proposed analytical solution to the simulated surface environment of small bodies, a prediction-correction procedure is presented. Finally, Monte Carlo simulations are carried out to verify the effectiveness of the proposed methods. The results indicate that the sensitivity of the hopping trajectory to uncertainties can be effectively diminished by employing the desensitized optimal trajectory and multiple hopping strategy.
未来的小型天体探测任务需要对目标上的多个点进行采样或访问，以获得更多的科学回报，这就要求漫游车具有在小型天体表面跳跃的能力。本文提出了一种为跳跃式漫游车生成脱敏最优轨迹的方法，旨在降低跳跃轨迹在不确定性情况下的敏感性。首先，考虑到参数不确定性和初始状态误差，基于弹道动力学推导出平面场景下最优初始状态的分析表达式。然后，在倾斜场景的上坡和下坡情况下开发了类似的方法。随后，分析了单跳、相同和非相同 N 跳策略下长距离跳跃轨迹的脱敏性能。为了便于将所提出的分析方案应用于小型物体的模拟表面环境，提出了一个预测修正程序。最后，还进行了蒙特卡罗模拟，以验证所提方法的有效性。结果表明，通过采用脱敏最优轨迹和多重跳跃策略，可以有效降低跳跃轨迹对不确定性的敏感性。
{"title":"Desensitized optimal trajectory for hopping rovers on small bodies","authors":"Shengying Zhu, Chuncheng Zhao","doi":"10.1177/09544100241262559","DOIUrl":"https://doi.org/10.1177/09544100241262559","url":null,"abstract":"Future exploration tasks of small bodies will need to sample or visit multiple points on the target to obtain more scientific returns, requiring rovers to have the ability to hop on a small body surface. This paper proposes an approach to generate a desensitized optimal trajectory for hopping rovers, aiming at reducing the sensitivity of hopping trajectory in the presence of uncertainties. Firstly, considering parameter uncertainties and initial state errors, analytical expressions of optimal initial states are derived on a planar scene, based on ballistic dynamics. Then, similar methods are developed in both uphill and downhill cases of inclined scenes. Subsequently, the desensitization performance of long-distance hopping trajectory is analyzed under single-hop, identical, and non-identical N-hop strategies. To facilitate the application of the proposed analytical solution to the simulated surface environment of small bodies, a prediction-correction procedure is presented. Finally, Monte Carlo simulations are carried out to verify the effectiveness of the proposed methods. The results indicate that the sensitivity of the hopping trajectory to uncertainties can be effectively diminished by employing the desensitized optimal trajectory and multiple hopping strategy.","PeriodicalId":54566,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part G-Journal of Aerospace Engineering","volume":"195 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141513870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-30DOI: 10.1177/09544100241254156
Luyi Yang, Haiyang Li, Jin Zhang
There are always uncertainties in practical engineering, and the design of the optimal Earth-Moon trajectory under uncertainties significantly reduces flight risk for the manned lunar exploration mission (MLEM). This paper proposes an interval programming method to optimize the trans-lunar trajectory under interval uncertainties. Firstly, the influence of the trans-lunar injection uncertainties (TLI) is investigated, finding that the reached orbit at the perilune is very sensitive to the impulse errors at TLI. Then, the design methods of the Earth-Moon trajectory and the trajectory correction maneuver (TCM) are presented. Based on the mathematical tool of the interval possibility degree, the interval programming model is built to transform the uncertain optimization problem into a deterministic one, and then a multi-layer optimization scheme is proposed to solve it. The uncertain objectives and constraints’ interval bounds are calculated in the inner loop, and the design variables are searched and optimized in the outer loop. The proposed method is used to design the Earth-Moon trajectories of both manned and unmanned spacecraft. The designed trajectories are insensitive to the uncertainties and are validated by the Monte Carlo simulations.
{"title":"An interval programming method of earth-moon trajectory for manned lunar exploration mission under interval uncertainty","authors":"Luyi Yang, Haiyang Li, Jin Zhang","doi":"10.1177/09544100241254156","DOIUrl":"https://doi.org/10.1177/09544100241254156","url":null,"abstract":"There are always uncertainties in practical engineering, and the design of the optimal Earth-Moon trajectory under uncertainties significantly reduces flight risk for the manned lunar exploration mission (MLEM). This paper proposes an interval programming method to optimize the trans-lunar trajectory under interval uncertainties. Firstly, the influence of the trans-lunar injection uncertainties (TLI) is investigated, finding that the reached orbit at the perilune is very sensitive to the impulse errors at TLI. Then, the design methods of the Earth-Moon trajectory and the trajectory correction maneuver (TCM) are presented. Based on the mathematical tool of the interval possibility degree, the interval programming model is built to transform the uncertain optimization problem into a deterministic one, and then a multi-layer optimization scheme is proposed to solve it. The uncertain objectives and constraints’ interval bounds are calculated in the inner loop, and the design variables are searched and optimized in the outer loop. The proposed method is used to design the Earth-Moon trajectories of both manned and unmanned spacecraft. The designed trajectories are insensitive to the uncertainties and are validated by the Monte Carlo simulations.","PeriodicalId":54566,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part G-Journal of Aerospace Engineering","volume":"39 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141197964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-13DOI: 10.1177/09544100241249350
Lixin Wang, Rong Zhao, Yi Zhang, Ting Yue
Conventional angular acceleration estimation methods generate non-negligible errors when the control surface rapidly deflects; hence, the estimated angular acceleration cannot be used for aerodynamic parameter identification directly. This paper proposes an angular acceleration estimation method based on angular velocity equivalent model. The angular acceleration of the angular velocity equivalent model, whose angular velocity response is consistent with the flight test data, is used as the estimated angular acceleration. Firstly, the equivalent angular velocity model is established by combining the generic aerodynamic model with the rotational dynamic equations of aircraft. Secondly, the angular velocity data and the control surface deflection data are synchronized. Finally, the angular velocity response of the equivalent model is used as the predictor, and the estimated angular acceleration is obtained by extended Kalman filter. The aerodynamic parameter identification and validation are carried out using the estimated angular acceleration of a large civil aircraft flight test data. The results show that the angular acceleration obtained through the proposed angular acceleration estimation method meets the accuracy requirement of aerodynamic parameter identification.
{"title":"Angular acceleration estimation and aerodynamic parameter identification based on angular velocity equivalent model","authors":"Lixin Wang, Rong Zhao, Yi Zhang, Ting Yue","doi":"10.1177/09544100241249350","DOIUrl":"https://doi.org/10.1177/09544100241249350","url":null,"abstract":"Conventional angular acceleration estimation methods generate non-negligible errors when the control surface rapidly deflects; hence, the estimated angular acceleration cannot be used for aerodynamic parameter identification directly. This paper proposes an angular acceleration estimation method based on angular velocity equivalent model. The angular acceleration of the angular velocity equivalent model, whose angular velocity response is consistent with the flight test data, is used as the estimated angular acceleration. Firstly, the equivalent angular velocity model is established by combining the generic aerodynamic model with the rotational dynamic equations of aircraft. Secondly, the angular velocity data and the control surface deflection data are synchronized. Finally, the angular velocity response of the equivalent model is used as the predictor, and the estimated angular acceleration is obtained by extended Kalman filter. The aerodynamic parameter identification and validation are carried out using the estimated angular acceleration of a large civil aircraft flight test data. The results show that the angular acceleration obtained through the proposed angular acceleration estimation method meets the accuracy requirement of aerodynamic parameter identification.","PeriodicalId":54566,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part G-Journal of Aerospace Engineering","volume":"5 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140936246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper addresses the problem of surveillance of dynamic crowds in a bounded arena using multiple drones. The strategy proposes a prediction-based path planning approach for drones, where the target’s future position is predicted and used to generate a traverse path. The procedure for grouping numerous human beings in order to deal with a dense crowd scenario is also described. An algorithm to dynamically divide and allocate the arena to drones is also proposed to ensure equal workload distribution among all drones in the framework. The paper also discusses relevant concepts like detecting anomalous crowd activity and searching for any missing target in the arena. The proposed algorithms are validated on MATLAB environment numerically and ROS/Gazebo physics engine as a part of simulation-in-the-loop (SITL).
{"title":"Drone path planning and dynamic arena-target allocation for crowd surveillance","authors":"Onkar Chopra, Samiksha Rajkumar Nagrare, Shuvrangshu Jana, Debasish Ghose","doi":"10.1177/09544100241253646","DOIUrl":"https://doi.org/10.1177/09544100241253646","url":null,"abstract":"The paper addresses the problem of surveillance of dynamic crowds in a bounded arena using multiple drones. The strategy proposes a prediction-based path planning approach for drones, where the target’s future position is predicted and used to generate a traverse path. The procedure for grouping numerous human beings in order to deal with a dense crowd scenario is also described. An algorithm to dynamically divide and allocate the arena to drones is also proposed to ensure equal workload distribution among all drones in the framework. The paper also discusses relevant concepts like detecting anomalous crowd activity and searching for any missing target in the arena. The proposed algorithms are validated on MATLAB environment numerically and ROS/Gazebo physics engine as a part of simulation-in-the-loop (SITL).","PeriodicalId":54566,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part G-Journal of Aerospace Engineering","volume":"17 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140936433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-10DOI: 10.1177/09544100241252041
Maliheh Najafi, António J. M. Ferreira, Flávio D. Marques
Sandwich structures with lattice cores are novel, lightweight composite structures and are widely used in the aerospace industry. Besides, the aeroelastic behavior of sandwich panels in a supersonic flow regime still needs to be thoroughly studied. This work investigates the supersonic flutter of a sandwich panel whose core is topology-optimized. A finite element model of a sandwich panel based on the layerwise theory, coupled with the first-order piston theory, is presented. The sandwich panel core is assessed using a topology optimization approach with flutter loading constraints. The subsequent analytical homogenization scheme is developed to provide the equivalent mechanical properties of the topology-optimized panel. The modeling approach is fully validated, and the results demonstrate that the sandwich panel is capable of enlarging the flutter-free operational flight range when compared with other conventional panel designs. A parametric analysis of the topology-optimized sandwich panel regarding the critical flutter conditions is performed.
{"title":"Aeroelastic analysis of a lightweight topology-optimized sandwich panel","authors":"Maliheh Najafi, António J. M. Ferreira, Flávio D. Marques","doi":"10.1177/09544100241252041","DOIUrl":"https://doi.org/10.1177/09544100241252041","url":null,"abstract":"Sandwich structures with lattice cores are novel, lightweight composite structures and are widely used in the aerospace industry. Besides, the aeroelastic behavior of sandwich panels in a supersonic flow regime still needs to be thoroughly studied. This work investigates the supersonic flutter of a sandwich panel whose core is topology-optimized. A finite element model of a sandwich panel based on the layerwise theory, coupled with the first-order piston theory, is presented. The sandwich panel core is assessed using a topology optimization approach with flutter loading constraints. The subsequent analytical homogenization scheme is developed to provide the equivalent mechanical properties of the topology-optimized panel. The modeling approach is fully validated, and the results demonstrate that the sandwich panel is capable of enlarging the flutter-free operational flight range when compared with other conventional panel designs. A parametric analysis of the topology-optimized sandwich panel regarding the critical flutter conditions is performed.","PeriodicalId":54566,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part G-Journal of Aerospace Engineering","volume":"2015 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140936251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-09DOI: 10.1177/09544100241252864
Cheol-Goo Jung, Pengyu Wang, Chang-Hun Lee
This paper presents an optimal guidance law for missile to achieve desired impact angles on a stationary target while accommodating the barrier constraint. The proposed guidance law consists of two parts: a baseline guidance command for intercepting the target with desired impact angles, and a bias command to prevent collision with the barrier. Specifically, the baseline guidance command is derived by solving a linearized optimal control problem, and its explicit trajectory solution is also obtained for collision estimation. The bias command is designed using a novel guidance error that is defined based on the geometrical relationship between the barrier and the proposed explicit trajectory solution. The new guidance law can be easily implemented to a variety of practical engagement geometries, resulting in successful collision avoidance and minimal control efforts. Its effectiveness and robustness are demonstrated via extensive numerical simulations.
{"title":"Optimal impact angle guidance law with barrier constraint","authors":"Cheol-Goo Jung, Pengyu Wang, Chang-Hun Lee","doi":"10.1177/09544100241252864","DOIUrl":"https://doi.org/10.1177/09544100241252864","url":null,"abstract":"This paper presents an optimal guidance law for missile to achieve desired impact angles on a stationary target while accommodating the barrier constraint. The proposed guidance law consists of two parts: a baseline guidance command for intercepting the target with desired impact angles, and a bias command to prevent collision with the barrier. Specifically, the baseline guidance command is derived by solving a linearized optimal control problem, and its explicit trajectory solution is also obtained for collision estimation. The bias command is designed using a novel guidance error that is defined based on the geometrical relationship between the barrier and the proposed explicit trajectory solution. The new guidance law can be easily implemented to a variety of practical engagement geometries, resulting in successful collision avoidance and minimal control efforts. Its effectiveness and robustness are demonstrated via extensive numerical simulations.","PeriodicalId":54566,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part G-Journal of Aerospace Engineering","volume":"175 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140941897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-07DOI: 10.1177/09544100241252233
Lijia Cao, Lin Wang, Yang Liu, Weihong Xu, Chuang Geng
In order to improve the ability of avoiding dynamic threats during the flight of unmanned aerial vehicles (UAVs), a deep reinforcement learning-based reactive trajectory planning method is proposed in this paper. Firstly, a constrained Rapidly-exploring Random Tree-Connect algorithm (C-RRT-Connect) is proposed as the basic algorithm of reactive trajectory planning to globally plan for avoiding static obstacles in the environment. The C-RRT-Connect algorithm introduces the idea of target attraction to constrain the optimal growth point in the RRT-Connect algorithm. Then, based on the global trajectory, the local optimization is carried out according to the dynamic threats detected by the UAV during the flight. According to the real-time relative state between the UAV and the detected dynamic threat, the reaction sampling points and directional coefficients for avoiding the corresponding dynamic threat are generated online via the action network trained with the depth deterministic policy gradient algorithm (DDPG). And then the local trajectory is adjusted to modify the flight trajectory of the UAV to achieve reactive obstacle avoidance. The simulation experiment firstly compares the global trajectory planning performance of C-RRT-Connect and RRT-Connect in static environment, and secondly compares the local trajectory planning performance of DDPG algorithm and the artificial potential field method in dynamic environment. The experimental results show that in static environment, C-RRT-Connect algorithm has faster searching speed, less invalid samples and higher searching trajectory quality than RRT-Connect algorithm; In a dynamic environment, DDPG algorithm reduces the average running time by about 26% compared with the artificial potential field method, and has a stronger ability to evade dynamic threats in real time.
{"title":"Deep reinforcement learning-based reactive trajectory planning method for UAVs","authors":"Lijia Cao, Lin Wang, Yang Liu, Weihong Xu, Chuang Geng","doi":"10.1177/09544100241252233","DOIUrl":"https://doi.org/10.1177/09544100241252233","url":null,"abstract":"In order to improve the ability of avoiding dynamic threats during the flight of unmanned aerial vehicles (UAVs), a deep reinforcement learning-based reactive trajectory planning method is proposed in this paper. Firstly, a constrained Rapidly-exploring Random Tree-Connect algorithm (C-RRT-Connect) is proposed as the basic algorithm of reactive trajectory planning to globally plan for avoiding static obstacles in the environment. The C-RRT-Connect algorithm introduces the idea of target attraction to constrain the optimal growth point in the RRT-Connect algorithm. Then, based on the global trajectory, the local optimization is carried out according to the dynamic threats detected by the UAV during the flight. According to the real-time relative state between the UAV and the detected dynamic threat, the reaction sampling points and directional coefficients for avoiding the corresponding dynamic threat are generated online via the action network trained with the depth deterministic policy gradient algorithm (DDPG). And then the local trajectory is adjusted to modify the flight trajectory of the UAV to achieve reactive obstacle avoidance. The simulation experiment firstly compares the global trajectory planning performance of C-RRT-Connect and RRT-Connect in static environment, and secondly compares the local trajectory planning performance of DDPG algorithm and the artificial potential field method in dynamic environment. The experimental results show that in static environment, C-RRT-Connect algorithm has faster searching speed, less invalid samples and higher searching trajectory quality than RRT-Connect algorithm; In a dynamic environment, DDPG algorithm reduces the average running time by about 26% compared with the artificial potential field method, and has a stronger ability to evade dynamic threats in real time.","PeriodicalId":54566,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part G-Journal of Aerospace Engineering","volume":"43 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140936438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents the results of an experimental investigation into the cooling performance of a rotor-stator cavity with liquid nitrogen spraying. The experiments were conducted under varying rotational Reynolds numbers ranging from 1.70 × 106 to 5.12 × 106. The effects of rotational speed on temperature drop rate are studied and compared in detail, as well as the heat transfer coefficient distribution. Sufficient data, such as heat flux, injection rate, and injection pressure, were collected to provide a basis for further study in explaining the spray and evaporation over the cavity. It was found that the cooling performance of the rotating disc is strongly affected by the rotational speed. The short-term period exhibits a peak cooling rate of 14°C/s, in contrast to the sustained cooling rate during the spray process at rotational speeds of 500r/min, which amounts to 0.9°C/s. The occurrence of cavitation and evaporation within the nozzle results in a reduction of flow coefficient and fluctuation of the injection differential pressure. The transient cooling performance is well-explained by the temperature changes and cooling-down time under different rotational speeds. The analysis of the heat transfer coefficient is further enhanced through an evaluation of the convective and conductive heat transfer rates using a one-dimensional theoretical approach. The average temperature of the disc is expected to decrease by 100°C within a time frame no longer than 120 s. Additionally, after a duration of 120 s, the average heat transfer rate on the cold side is anticipated to surpass 8000 W/(m·K).
{"title":"Effects of rotational speed on transient cooling performance of nozzle spray with liquid nitrogen in a rotor-stator cavity","authors":"Xuesen Yang, Wei Zhao, Binglong Zhang, Sanqun Ren, Xiaorong Xiang, Qingjun Zhao","doi":"10.1177/09544100241251504","DOIUrl":"https://doi.org/10.1177/09544100241251504","url":null,"abstract":"This paper presents the results of an experimental investigation into the cooling performance of a rotor-stator cavity with liquid nitrogen spraying. The experiments were conducted under varying rotational Reynolds numbers ranging from 1.70 × 10<jats:sup>6</jats:sup> to 5.12 × 10<jats:sup>6</jats:sup>. The effects of rotational speed on temperature drop rate are studied and compared in detail, as well as the heat transfer coefficient distribution. Sufficient data, such as heat flux, injection rate, and injection pressure, were collected to provide a basis for further study in explaining the spray and evaporation over the cavity. It was found that the cooling performance of the rotating disc is strongly affected by the rotational speed. The short-term period exhibits a peak cooling rate of 14°C/s, in contrast to the sustained cooling rate during the spray process at rotational speeds of 500r/min, which amounts to 0.9°C/s. The occurrence of cavitation and evaporation within the nozzle results in a reduction of flow coefficient and fluctuation of the injection differential pressure. The transient cooling performance is well-explained by the temperature changes and cooling-down time under different rotational speeds. The analysis of the heat transfer coefficient is further enhanced through an evaluation of the convective and conductive heat transfer rates using a one-dimensional theoretical approach. The average temperature of the disc is expected to decrease by 100°C within a time frame no longer than 120 s. Additionally, after a duration of 120 s, the average heat transfer rate on the cold side is anticipated to surpass 8000 W/(m·K).","PeriodicalId":54566,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers Part G-Journal of Aerospace Engineering","volume":"24 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140936245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：