Transactions of Nanjing University of Aeronautics & Astronautics
Volume 0,Issue 5,2022 Table of Contents
2022(5):507-520.
DOI: 10.16356/j.1005-1120.2022.05.001
Abstract:
In order to improve the frequency response and anti-interference characteristics of the smart electromechanical actuator（EMA） system， and aiming at the force fighting problem when multiple actuators work synchronously， a multi input multi output （MIMO） position difference cross coupling control coordinated strategy based on double-closed-loop load feedforward control is proposed and designed. In this strategy， the singular value method of return difference matrix is used to design the parameter range that meets the requirements of system stability margin， and the sensitivity function and the H∞ norm theory are used to design and determine the optimal solution in the obtained parameter stability region， so that the multi actuator system has excellent synchronization， stability and anti-interference. At the same time， the mathematical model of the integrated smart EMA system is established. According to the requirements of point-to-point control， the controller of double-loop control and load feedforward compensation is determined and designed to improve the frequency response and anti-interference ability of single actuator. Finally， the 270 V high-voltage smart EMA system experimental platform is built， and the frequency response， load feedforward compensation and coordinated control experiments are carried out to verify the correctness of the position difference cross coupling control strategy and the rationality of the parameter design， so that the system can reach the servo control indexes of bandwidth 6 Hz， the maximum output force 20 000 N and the synchronization error ≤0.1 mm， which effectively solves the problem of force fighting.
In order to improve the frequency response and anti-interference characteristics of the smart electromechanical actuator（EMA） system， and aiming at the force fighting problem when multiple actuators work synchronously， a multi input multi output （MIMO） position difference cross coupling control coordinated strategy based on double-closed-loop load feedforward control is proposed and designed. In this strategy， the singular value method of return difference matrix is used to design the parameter range that meets the requirements of system stability margin， and the sensitivity function and the H∞ norm theory are used to design and determine the optimal solution in the obtained parameter stability region， so that the multi actuator system has excellent synchronization， stability and anti-interference. At the same time， the mathematical model of the integrated smart EMA system is established. According to the requirements of point-to-point control， the controller of double-loop control and load feedforward compensation is determined and designed to improve the frequency response and anti-interference ability of single actuator. Finally， the 270 V high-voltage smart EMA system experimental platform is built， and the frequency response， load feedforward compensation and coordinated control experiments are carried out to verify the correctness of the position difference cross coupling control strategy and the rationality of the parameter design， so that the system can reach the servo control indexes of bandwidth 6 Hz， the maximum output force 20 000 N and the synchronization error ≤0.1 mm， which effectively solves the problem of force fighting.
2022(5):521-529.
DOI: 10.16356/j.1005-1120.2022.05.002
Abstract:
For high-voltage and high-power Gallium Nitride （GaN） power amplifiers， a drain modulation circuit with rapid rise and fall time is proposed in this paper. To decrease the rise and fall time， the high-side bootstrap drive circuit with an auxiliary discharge switch is proposed. The effect of the parasitics is analyzed based on calculation and the parallel bonding is proposed. The storage capacitance of power supply is calculated quantitatively to provide large pulse current. To ensure safe operation of the power amplifier， the circuit topology with the dead-time control and sequential control is proposed. Finally， a prototype is built to verify the drain modulation circuit design. The experiments prove that the rise time and fall time of the output pulse signal are both less than 100 ns.
For high-voltage and high-power Gallium Nitride （GaN） power amplifiers， a drain modulation circuit with rapid rise and fall time is proposed in this paper. To decrease the rise and fall time， the high-side bootstrap drive circuit with an auxiliary discharge switch is proposed. The effect of the parasitics is analyzed based on calculation and the parallel bonding is proposed. The storage capacitance of power supply is calculated quantitatively to provide large pulse current. To ensure safe operation of the power amplifier， the circuit topology with the dead-time control and sequential control is proposed. Finally， a prototype is built to verify the drain modulation circuit design. The experiments prove that the rise time and fall time of the output pulse signal are both less than 100 ns.
2022(5):530-540.
DOI: 10.16356/j.1005-1120.2022.05.003
Abstract:
Chang’e-5 mission is China’s first lunar sample return mission. It contains several new flight phases compared with the previous lunar missions， such as the lunar take-off and orbit insertion phase， the rendezvous and docking phase， etc. Chang’e-5 mission is extremely complicated and full of new challenges. This paper sorts out the characteristics and the difficulties in telemetry， tracking， and command （TT&C） of Chang’e-5 mission. The main technical contribution is a reliable general design of the TT&C system， including the application of X-band TT&C in launch and early orbit phase （LEOP）， multiple targets simultaneous TT&C in X-band， lunar surface benchmark calibration， high-precision and rapid orbit trajectory determination for the lunar surface take-off， remote guidance rendezvous and docking， the determination of the initial navigational value for the separation point of the Chang’e-5 orbiter and returner， and the design of the reentry measurement chain. Based on this scheme， a global deep space TT&C network and interplanetary reentry measurement chain have been established for China， and near-continuous TT&C support for China’s first extraterrestrial object sampling and return mission has been realized， ensuring reliable tracking， accurate measurement and accurate control. The global deep space network can provide TT&C support comparable to that of National Aeronautics and Space Administration（NASA） and European Space Agency（ESA） for subsequent lunar and deep space exploration missions. The techniques of rapid trajectory determination of lunar take-off and orbit entry， as well as high precision and remote guidance of lunar orbit rendezvous and docking can lay a technological foundation for the future manned lunar exploration missions and planetary sampling and return missions.
Chang’e-5 mission is China’s first lunar sample return mission. It contains several new flight phases compared with the previous lunar missions， such as the lunar take-off and orbit insertion phase， the rendezvous and docking phase， etc. Chang’e-5 mission is extremely complicated and full of new challenges. This paper sorts out the characteristics and the difficulties in telemetry， tracking， and command （TT&C） of Chang’e-5 mission. The main technical contribution is a reliable general design of the TT&C system， including the application of X-band TT&C in launch and early orbit phase （LEOP）， multiple targets simultaneous TT&C in X-band， lunar surface benchmark calibration， high-precision and rapid orbit trajectory determination for the lunar surface take-off， remote guidance rendezvous and docking， the determination of the initial navigational value for the separation point of the Chang’e-5 orbiter and returner， and the design of the reentry measurement chain. Based on this scheme， a global deep space TT&C network and interplanetary reentry measurement chain have been established for China， and near-continuous TT&C support for China’s first extraterrestrial object sampling and return mission has been realized， ensuring reliable tracking， accurate measurement and accurate control. The global deep space network can provide TT&C support comparable to that of National Aeronautics and Space Administration（NASA） and European Space Agency（ESA） for subsequent lunar and deep space exploration missions. The techniques of rapid trajectory determination of lunar take-off and orbit entry， as well as high precision and remote guidance of lunar orbit rendezvous and docking can lay a technological foundation for the future manned lunar exploration missions and planetary sampling and return missions.
2022(5):541-560.
DOI: 10.16356/j.1005-1120.2022.05.004
Abstract:
Icing on the surface of aircraft will not only aggravate its quality and affect flight control， but even cause safety accidents， which is one of the important factors restricting all-weather flight. Bio-inspired anti-icing surfaces have gained great attention recently due to their low-hysteresis， non-stick properties， slow nucleation rate and low ice adhesion strength. These bio-inspired anti-icing surfaces， such as superhydrophobic surfaces， slippery liquid-infused porous surfaces and quasi-liquid film surfaces， have realized excellent anti-icing performance at various stages of icing. However， for harsh environment， there are still many problems and challenges. From the perspective of bio-inspiration， the mechanism of icing nucleation， liquid bounce and ice adhesion has been reviewed together with the application progress and bottleneck issues about anti-icing in view of the process of icing. Subsequently， the reliability and development prospect of active， passive and active-passive integrated anti-icing technology are discussed， respectively.
Icing on the surface of aircraft will not only aggravate its quality and affect flight control， but even cause safety accidents， which is one of the important factors restricting all-weather flight. Bio-inspired anti-icing surfaces have gained great attention recently due to their low-hysteresis， non-stick properties， slow nucleation rate and low ice adhesion strength. These bio-inspired anti-icing surfaces， such as superhydrophobic surfaces， slippery liquid-infused porous surfaces and quasi-liquid film surfaces， have realized excellent anti-icing performance at various stages of icing. However， for harsh environment， there are still many problems and challenges. From the perspective of bio-inspiration， the mechanism of icing nucleation， liquid bounce and ice adhesion has been reviewed together with the application progress and bottleneck issues about anti-icing in view of the process of icing. Subsequently， the reliability and development prospect of active， passive and active-passive integrated anti-icing technology are discussed， respectively.
2022(5):561-568.
DOI: 10.16356/j.1005-1120.2022.05.005
Abstract:
Accumulation of ice on airfoils and engines seriously endangers the safety of the fight. The accurate measurement of adhesion strength at the ice-substrate interface plays a vital role in the design of anti/de-icing systems. In this pursuit， the present study envisages the evaluation of the stress at the icesubstrate interface to guide the design of experimental set-ups and improve the measurement accuracy of shear strength using the finite element analysis （FEA） method. By considering such factors as the peeling stress， maximum von-mises stress and uniformity of stress， the height and radius of ice and the loading height are investigated. Based on the simulation results， appropriate parameters are selected for the experimental validation. Simulation results show that the peeling stress is decreased by reducing the loading height and increasing the height of ice. Higher ice， increasing loading height and smaller ice radius are found to be beneficial for the uniformity of stress. To avoid cracks or ice-breaking， it is imperative that the ice should be of a small radius and greater height. Parameters including the ice height of 25 mm， radius of 20 mm， and loading height of 9 mm are adopted in the experiment. The results of FEA and the experimental validation can significantly enhance the measurement accuracy of shear strength.
Accumulation of ice on airfoils and engines seriously endangers the safety of the fight. The accurate measurement of adhesion strength at the ice-substrate interface plays a vital role in the design of anti/de-icing systems. In this pursuit， the present study envisages the evaluation of the stress at the icesubstrate interface to guide the design of experimental set-ups and improve the measurement accuracy of shear strength using the finite element analysis （FEA） method. By considering such factors as the peeling stress， maximum von-mises stress and uniformity of stress， the height and radius of ice and the loading height are investigated. Based on the simulation results， appropriate parameters are selected for the experimental validation. Simulation results show that the peeling stress is decreased by reducing the loading height and increasing the height of ice. Higher ice， increasing loading height and smaller ice radius are found to be beneficial for the uniformity of stress. To avoid cracks or ice-breaking， it is imperative that the ice should be of a small radius and greater height. Parameters including the ice height of 25 mm， radius of 20 mm， and loading height of 9 mm are adopted in the experiment. The results of FEA and the experimental validation can significantly enhance the measurement accuracy of shear strength.
2022(5):569-583.
DOI: 10.16356/j.1005-1120.2022.05.006
Abstract:
A new fluid bag buffer mechanism， which can provide large axial stiffness under the small displacement， is designed. The dynamic change laws of the mechanism stiffness and the internal pressure of the fluid bag are studied when it is subjected to impact load. According to the protection performance for the flexible joint and the pressure change in the fluid bag during the impact process， the sensitivity of the geometric parameters of the fluid bag to the axial stiffness is analyzed by using the orthogonal experimental method， and the optimal parameter combination of the geometric parameters of the fluid bag under impact is obtained， leading to the displacement of the inner shell reduce by 41.4%. The results show that the internal pressure of the fluid bag is a rising process of oscillation and fluctuation. The sensitivity of the geometric parameters of the fluid bag to the displacement of the inner shell from high to low is as follows： Height H， radius r， wall thickness t， chamfer A. The correlation between the geometric parameters of the fluid bag and its internal pressure is： H is negatively correlated with the internal pressure， while the r， t， and A are positively correlated with the internal pressure.
A new fluid bag buffer mechanism， which can provide large axial stiffness under the small displacement， is designed. The dynamic change laws of the mechanism stiffness and the internal pressure of the fluid bag are studied when it is subjected to impact load. According to the protection performance for the flexible joint and the pressure change in the fluid bag during the impact process， the sensitivity of the geometric parameters of the fluid bag to the axial stiffness is analyzed by using the orthogonal experimental method， and the optimal parameter combination of the geometric parameters of the fluid bag under impact is obtained， leading to the displacement of the inner shell reduce by 41.4%. The results show that the internal pressure of the fluid bag is a rising process of oscillation and fluctuation. The sensitivity of the geometric parameters of the fluid bag to the displacement of the inner shell from high to low is as follows： Height H， radius r， wall thickness t， chamfer A. The correlation between the geometric parameters of the fluid bag and its internal pressure is： H is negatively correlated with the internal pressure， while the r， t， and A are positively correlated with the internal pressure.
2022(5):584-592.
DOI: 10.16356/j.1005-1120.2022.05.007
Abstract:
In order to reduce the accident rate of consumer-grade unmanned aerial vehicles （UAVs） in daily use scenarios， the accident causes are analyzed based on the accident cases of consumer-grade UAVs. By extracting accident causing factors based on the Grounded theory， the relationship between these factors is analyzed. The Bayesian network for consumer-grade UAV accidents is constructed. With the Grounded theory-Bayesian network， the probability of four types of accidents is inferred： fall， air collision， disappearance， and personal injury. With the posterior probability of each factor being reversely reasoned， the causal chain with the maximum probability of each accident is obtained. After the sensitivity of each factor is analyzed， the key nodes in the network accordingly are inferred. Then the causing factors of consumer-grade UAV accidents are analyzed. The results show that the probability of fall accident is the highest， the fall accident is associated with the probabilistic maximum causal chain of personal injury， and the sensitivity analysis results of each type of accident as the result node are inconsistent.
In order to reduce the accident rate of consumer-grade unmanned aerial vehicles （UAVs） in daily use scenarios， the accident causes are analyzed based on the accident cases of consumer-grade UAVs. By extracting accident causing factors based on the Grounded theory， the relationship between these factors is analyzed. The Bayesian network for consumer-grade UAV accidents is constructed. With the Grounded theory-Bayesian network， the probability of four types of accidents is inferred： fall， air collision， disappearance， and personal injury. With the posterior probability of each factor being reversely reasoned， the causal chain with the maximum probability of each accident is obtained. After the sensitivity of each factor is analyzed， the key nodes in the network accordingly are inferred. Then the causing factors of consumer-grade UAV accidents are analyzed. The results show that the probability of fall accident is the highest， the fall accident is associated with the probabilistic maximum causal chain of personal injury， and the sensitivity analysis results of each type of accident as the result node are inconsistent.
2022(5):593-605.
DOI: 10.16356/j.1005-1120.2022.05.008
Abstract:
In the passive turning state， the helicopter turns through the tail rotor force and the friction of the ground to the tire. In practice， it is found that the helicopter will turn difficultly under low aircraft ground speed or static state. This paper takes a certain type of helicopter as the research object， and establishes the dynamic model of helicopter ground turning motion based on the basic theory of dynamics. This model takes into account the six-degree-of-freedom motion model of the helicopter body， the motion model of the landing gear buffer， the tire mechanics model and the friction characteristics of the strut friction disc. The dynamic simulation of the helicopter right angle turn and static turn is carried out， and the influence of parameters such as tail rotor pull， taxi speed， tail wheel stability distance on the dynamic response of the turn is studied. The results show that under the same ground taxing speed， the tail wheel angle increases with the increase of tail rotor force. When the tail rotor force is the same， the tail wheel angle increases with the increase of ground taxing speed. When the helicopter is completely static， it is the most difficult to turn， which requires much bigger force of the tail rotor to turn. In addition， the change of the stability distance of the tail wheel has an obvious influence on the turning. When the stability distance is doubled， the tail rotor force will be reduced by 30% to the same angle of the tail wheel.
In the passive turning state， the helicopter turns through the tail rotor force and the friction of the ground to the tire. In practice， it is found that the helicopter will turn difficultly under low aircraft ground speed or static state. This paper takes a certain type of helicopter as the research object， and establishes the dynamic model of helicopter ground turning motion based on the basic theory of dynamics. This model takes into account the six-degree-of-freedom motion model of the helicopter body， the motion model of the landing gear buffer， the tire mechanics model and the friction characteristics of the strut friction disc. The dynamic simulation of the helicopter right angle turn and static turn is carried out， and the influence of parameters such as tail rotor pull， taxi speed， tail wheel stability distance on the dynamic response of the turn is studied. The results show that under the same ground taxing speed， the tail wheel angle increases with the increase of tail rotor force. When the tail rotor force is the same， the tail wheel angle increases with the increase of ground taxing speed. When the helicopter is completely static， it is the most difficult to turn， which requires much bigger force of the tail rotor to turn. In addition， the change of the stability distance of the tail wheel has an obvious influence on the turning. When the stability distance is doubled， the tail rotor force will be reduced by 30% to the same angle of the tail wheel.
9 Mechanism Design and Motion Analysis of Heavy-Load Transfer Robot with Parallel Four-Bar Mechanism
2022(5):606-618.
DOI: 10.16356/j.1005-1120.2022.05.009
Abstract:
Heavy-load transfer robots are widely used in automobile production and machinery manufacturing to improve production efficiency. In order to meet the needs of large billet transfer， a 4-DOF transfer robot is designed in this paper， which consists of parallel four-bar mechanisms. The Jacobian matrix referring to the mapping matrix from the joint velocity to the operating space velocity of the transfer robot can be solved by the differential-vector method. The mean value of the Jacobian matrix condition number in the workspace is used as the global performance index of the robot velocity and the optimization goal. The constraint condition is established based on the actual working condition. Then the linkage length optimization is carried out to decrease the length of the linkage and to increase the global performance index of velocity. The total length of robot rods is reduced by 6.12%. The global performance index of velocity is improved by 45.15%. Taking the optimized rod length as the mechanism parameter， the distribution of the motion space of the transfer robot is obtained. Finally， the results show that the proposed method for establishing the Jacobian matrix of the lower-mobility robot and for the optimization of the rods based on the velocity global performance index is accurate and effective. The workspace distribution of the robot meets the design requirements.
Heavy-load transfer robots are widely used in automobile production and machinery manufacturing to improve production efficiency. In order to meet the needs of large billet transfer， a 4-DOF transfer robot is designed in this paper， which consists of parallel four-bar mechanisms. The Jacobian matrix referring to the mapping matrix from the joint velocity to the operating space velocity of the transfer robot can be solved by the differential-vector method. The mean value of the Jacobian matrix condition number in the workspace is used as the global performance index of the robot velocity and the optimization goal. The constraint condition is established based on the actual working condition. Then the linkage length optimization is carried out to decrease the length of the linkage and to increase the global performance index of velocity. The total length of robot rods is reduced by 6.12%. The global performance index of velocity is improved by 45.15%. Taking the optimized rod length as the mechanism parameter， the distribution of the motion space of the transfer robot is obtained. Finally， the results show that the proposed method for establishing the Jacobian matrix of the lower-mobility robot and for the optimization of the rods based on the velocity global performance index is accurate and effective. The workspace distribution of the robot meets the design requirements.
2022(5):619-636.
DOI: 10.16356/j.1005-1120.2022.05.010
Abstract:
In order to investigate the effect of the radial gradation of the lobed nozzles on the flow field organization， a cold water model experimental platform for a combustion chamber with radial-staged 13-point lobed nozzles is built. Compared with a series of combustion OH* luminescence experiments tested by the University of Cincinnati， the four corresponding working conditions of no load， partial load， cruise and take off are selected. The vortex structure， vorticity value， multi-combustion materiel field and combustion characteristics of the flow field in the radial staged combustion chamber of the lobed nozzles under the equivalence ratio， the fuel injection method， the fuel injection ratio and other factors are numerically studied. The results show that under different influencing factors， the varation trend of the hydroxyl flame field of the lobe combustion chamber is basically the same as that of the hydroxyl light emission experiment of the swirl combustion chamber， but the flame field shape is quite different. The local equivalent ratio has a greater influence on the relevant combustion performance of the combustion chamber. Under the conditions of lower equivalence ratio， three-stage air and fuel injection mode， and gradually transferring the fuel flow of the pilot circuit to the external circuit， the temperature field and flame field of the combustion chamber are more evenly distributed， the outlet temperature field quality is better， the combustion efficiency is higher， and the NOX emission is relatively low. These are basically consistent with the cold test results. The cold experimental results illustrate the importance of the influence of the flow field organization on the combustion organization and verify the reliability of the calculation results.
In order to investigate the effect of the radial gradation of the lobed nozzles on the flow field organization， a cold water model experimental platform for a combustion chamber with radial-staged 13-point lobed nozzles is built. Compared with a series of combustion OH* luminescence experiments tested by the University of Cincinnati， the four corresponding working conditions of no load， partial load， cruise and take off are selected. The vortex structure， vorticity value， multi-combustion materiel field and combustion characteristics of the flow field in the radial staged combustion chamber of the lobed nozzles under the equivalence ratio， the fuel injection method， the fuel injection ratio and other factors are numerically studied. The results show that under different influencing factors， the varation trend of the hydroxyl flame field of the lobe combustion chamber is basically the same as that of the hydroxyl light emission experiment of the swirl combustion chamber， but the flame field shape is quite different. The local equivalent ratio has a greater influence on the relevant combustion performance of the combustion chamber. Under the conditions of lower equivalence ratio， three-stage air and fuel injection mode， and gradually transferring the fuel flow of the pilot circuit to the external circuit， the temperature field and flame field of the combustion chamber are more evenly distributed， the outlet temperature field quality is better， the combustion efficiency is higher， and the NOX emission is relatively low. These are basically consistent with the cold test results. The cold experimental results illustrate the importance of the influence of the flow field organization on the combustion organization and verify the reliability of the calculation results.
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