In order to explore the safe operation of UAVs in non-segregated airspace,a collision risk model for cylindrical UAVs based on conflict areas was constructed and the risk of conflict between manned and unmanned aerial...In order to explore the safe operation of UAVs in non-segregated airspace,a collision risk model for cylindrical UAVs based on conflict areas was constructed and the risk of conflict between manned and unmanned aerial vehicles was researched.According to the results of risk analysis,a strategy for solving the conflict of aircraft is proposed,and the risk assessment experiment of unmanned aerial vehicle(UAV)in non-isolated airspace conflict is carried out.The results show that under the experimental conditions,large unmanned aerial vehicles equipped with ADS-B,TCAS and other airborne sensing systems will indeed interfere with other aircraft in airspace when they enter non-isolated airspace.Especially when the number of aircraft in airspace is large,the automatic avoidance system of UAV will increase the avoidance time and trigger the safety alarm,but the safety level is still acceptable.This indicates that it is relatively safe for UAVs to enter non-isolated airspace under limited conditions.The results can be used as a reference for the safe operation of unmanned aerial vehicle(UAV)in non-isolated airspace.展开更多
Abstract The flow control of hydraulic transformers is a great challenge. To meet this challenge, a new kind of hydraulic transformer, variable hydraulic transformer （VHT）, is proposed in this work. This paper focus...Abstract The flow control of hydraulic transformers is a great challenge. To meet this challenge, a new kind of hydraulic transformer, variable hydraulic transformer （VHT）, is proposed in this work. This paper focuses on the power characteristics of the newly proposed VHT, including instanta neous power, average power, power pulsation, and efficiency. In the analyses, the concepts of efficiency, input power, output power, starting angle, and ceasing angle are defined or redefined. To investigate the power characteristics, their models are derived by considering the governing fac tors such as the control angle of the swash plate and the structure of the port plate. This work high lights that the load flow can be adjusted by adjusting the control angle of the swash plate, and the power characteristics at the Bport produce a remarkable change. In addition, the VHT has a starting angle and a ceasing angle, and these two angles can be adjusted by the influencing factors. The results reveal that the power pulsation and the jump points of the instantaneous power are the primary causes of a less smooth work. Then, it is shown that the control angle of the port plate, the control angle of the swash plate, and the pressures at the ports are the three key elements for a stable operation. The results also reveal that the adjustment of the influencing factors can improve the efficiency.展开更多
基金The authors would like to thank National Nature Science Foundation of China under Grant(71701202)The special funding project of Civil Aviation University of China for the basic scientific research services of the Central University(3122013Z006).
文摘In order to explore the safe operation of UAVs in non-segregated airspace,a collision risk model for cylindrical UAVs based on conflict areas was constructed and the risk of conflict between manned and unmanned aerial vehicles was researched.According to the results of risk analysis,a strategy for solving the conflict of aircraft is proposed,and the risk assessment experiment of unmanned aerial vehicle(UAV)in non-isolated airspace conflict is carried out.The results show that under the experimental conditions,large unmanned aerial vehicles equipped with ADS-B,TCAS and other airborne sensing systems will indeed interfere with other aircraft in airspace when they enter non-isolated airspace.Especially when the number of aircraft in airspace is large,the automatic avoidance system of UAV will increase the avoidance time and trigger the safety alarm,but the safety level is still acceptable.This indicates that it is relatively safe for UAVs to enter non-isolated airspace under limited conditions.The results can be used as a reference for the safe operation of unmanned aerial vehicle(UAV)in non-isolated airspace.
基金co-supported by the Open Foundation of State Key Laboratory of Fluid Transmission and Control of China(No.GZKF-2008003)the National Natural Science Foundation of China(Nos.50875054 and 51275123)
文摘Abstract The flow control of hydraulic transformers is a great challenge. To meet this challenge, a new kind of hydraulic transformer, variable hydraulic transformer （VHT）, is proposed in this work. This paper focuses on the power characteristics of the newly proposed VHT, including instanta neous power, average power, power pulsation, and efficiency. In the analyses, the concepts of efficiency, input power, output power, starting angle, and ceasing angle are defined or redefined. To investigate the power characteristics, their models are derived by considering the governing fac tors such as the control angle of the swash plate and the structure of the port plate. This work high lights that the load flow can be adjusted by adjusting the control angle of the swash plate, and the power characteristics at the Bport produce a remarkable change. In addition, the VHT has a starting angle and a ceasing angle, and these two angles can be adjusted by the influencing factors. The results reveal that the power pulsation and the jump points of the instantaneous power are the primary causes of a less smooth work. Then, it is shown that the control angle of the port plate, the control angle of the swash plate, and the pressures at the ports are the three key elements for a stable operation. The results also reveal that the adjustment of the influencing factors can improve the efficiency.
