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UAV has the characteristics of high mobility and easy deployment, which can improve the performance of edge computing system. In order to solve the problems of UAV trajectory optimization, user power allocation and task offloading strategy, this paper proposed a Two-layer Deep Reinforcement Learning (TDRL) algorithm for task offloading. The upper layer used the multi-agent deep reinforcement learning to optimize the trajectories of UAVs, and dynamically allocated the user transmission power to improve the transmission rate of the network. The lower layer used multiple parallel deep neural networks to generate the optimal offloading decision to minimize network latency and energy consumption. The simulation results show that the proposed algorithm enables UAVs to track user movement, significantly reduces system latency and energy consumption, and provides users with better task offloading services. [ABSTRACT FROM AUTHOR]

Plant protection is moving toward mechanization and intelligence in the process of modern agriculture in recent years. Autonomous operation of unmanned aerial vehicles (UAV) can reduce the quality errors from the visual images or manual experience, particularly for labor cost saving. Among them, trajectory optimization is one of the most important steps during the autonomous operation of plant protection UAVs. A reasonable algorithm of trajectory optimization can be expected for the UAVs to more efficiently and safely realize the tracking operations. The current algorithm of mainstream optimization focuses mainly on trajectory accuracy and algorithm efficiency in the tracing scene. But there is an overshoot of state quantity and serious trajectory deviation in the special scene of agricultural plant protection, due to complex situations, such as line feed and turn. Therefore, it is very necessary to optimize the trajectory suitable for the operation scenarios of plant protection. Simple time allocation cannot fully meet the requirements of trajectory optimization in the traditional minimum-SNAP algorithm, such as the large trajectory deviation error. In this study, an improved minimum-SNAP algorithm was proposed for trajectory optimization in the operation scenarios of plant protection. Firstly, the real-time kinematic (RTK) integrated navigation system carried by the plant protection UAV was used to collect the topographic data of the plant protection plots. Then the data was imported into the robot operating system (ROS) in the central controller. The surface fitting was also utilized to obtain the three-dimensional spatial map. The cattle ploughing method was selected to plan the initial operation path. Secondly, the task path was optimized using an improved minimum-SNAP algorithm. The cost function of time allocation was also constructed using the state parameter variable of the initial operation path. In addition, the change rate of the initial path baseline angle was introduced as a reference factor, in order to obtain the optimal time allocation after optimization. Thirdly, the coefficient optimization cost function of the minimum-SNAP algorithm was reconstructed using the time allocation information. The gradient penalty factor of position offset was then added to the optimization function. The trajectory expression of the piecewise polynomial was then obtained to solve the coefficient of the trajectory polynomial after optimization. Finally, the UAV position control period was substituted into the piecewise trajectory polynomial for the track point, which was taken as the location expectation to control the UAV motion. A simulation test was carried out to preliminarily verify using the Matlab platform. The initial path was taken as the "U" type round-trip operation track in twodimensional space. The average acceleration of the improved algorithm was 0.390 m/s², which was 19.75% lower than the traditional. Furthermore, the average trajectory offset was 0.051 m/s², which was 66.88% lower than the traditional. The physical test site was selected as the mulberry forest on the slope with the complex terrain. The test results show that the improved algorithm reduced the average acceleration and deviation by 7.82%, and 45.56%, respectively, compared with the traditional under the same running time. An outstanding inhibition was achieved in the trajectory deviation with the reduced overshoot during line feed turning. The finding can also provide a technical and theoretical basis for the UAV trajectory optimization in the scenario of plant protection. [ABSTRACT FROM AUTHOR]

In wireless communication system, buildings or active eavesdroppers by illegal devices can block the communication link between the transmitter and receiver. Utilizing the flexible mobility of unmanned aerial vehicle (UAV) and the intelligent controllable characteristic of intelligent reflective surface (IRS) in wireless environment, this paper proposed a safe transmission scheme of physical layer for IRS assisted UAV to maximize the averaged secrecy rate of the legitimate link. The scheme firstly utilized block coordinate descent method to decompose the average secrecy rate maximization problem of the system into three sub-problems: UAV-IRS flight trajectory optimization, IRS phase shift optimization and transmission power optimization. And then, this scheme transformed each subproblem into a convex optimization subproblem by utilizing relaxation variables, phase alignment and successive convex approximation methods, respectively. Furthermore, this paper used the alternating optimization method to obtain the maximum average secrecy rate of the system. Numerical simulation results show that the transmission power of the source node, the flight position and altitude of UAV-IRS and the number of IRS reflective elements are the main factors for improving the averaged secrecy rate of the legitimate link. The proposed scheme can effectively improve the average secrecy rate of the system with good convergence by comparing with the other two benchmark schemes. [ABSTRACT FROM AUTHOR]

Due to the complexity of the working scene of the forest fruit ball harvesting manipulator, the accuracy of the manipulator control is increasingly required. Considering the influence of the dynamic model of the manipulator on its control accuracy, in order to improve the control accuracy of the manipulator, a three-iterative global parameter identification method based on the least square method and GMM under the optimized excitation trajectory is proposed. This method takes the 6 - DOF manipulator configuration as an example, and obtains the minimum parameter set by establishing the dynamic model and QR decomposition. The optimization parameters of the incentive trajectory are obtained through the trajectory optimization algorithm, and then the optimized incentive trajectory is obtained. After the trajectory is obtained, the joint torque is identified by iterative weighted least square method, and the nonlinear friction force of the manipulator is fitted by constructing a nonlinear model that distinguishes high and low speed. The GMM algorithm is used to compensate the uncertain torque component that cannot be accurately modeled. Experimental tests are carried out on the COMAN R5 manipulator. Results show that the proposed trajectory parameter optimization method reduces the number of conditions from 329 to 193, and the average root mean square of torque residuals from 9.53 to 6.14, which proves the feasibility and effectiveness of the excitation trajectory and identification scheme. [ABSTRACT FROM AUTHOR]

Helicopters have been playing an increasingly important role in military and civilian activities. The review of helicopter noise reduction is needed to be updated, because new technologies are constantly emerging. Firstly, the mechanism and propagation properties of the rotor (tail rotor) noise are described, and the co‑axial rigid rotor high‑speed helicopter and the tilting rotor are introduced. There are complicated aerodynamic or acoustic interaction in two new configuration helicopters. Secondly, the progress of helicopter flight noise measurement, as the verification approach for low noise design technologies, is demonstrated. Then, the design technologies for silent helicopters are summarized. The passive noise reduction strategies have been intensively implemented, and reduced helicopter radiated noise level greatly. The strategies of variable rotor speed and low noise trajectory are gradually maturing. However, the active control technologies are in the laboratory stage, and need further research on driving devices and control parameters et al. The final part summarizes the state of art for low noise control strategies in helicopters, and outlooks the development trend. [ABSTRACT FROM AUTHOR]

This paper considers the physical-layer security of information transmission in an unmanned aerial vehicle (UAV) multi-user communication system, where a UAV communicates with multiple users on the ground, with the presence of an eavesdropper on the ground trying to intercept the confidential information sent from the UAV to the users. The channels between the UAV and all ground nodes are modeled as more accurate probabilistic LoS (line-of-sight) channels. This paper studies maximizing the minimum average secrecy rate of all users by jointly designing the three-dimensional (3D) trajectory of the UAV and the user scheduling, under the constraints of UAV fight conditions and the discrete user scheduling parameters. To solve the optimization design problem for the UAV secure communication system under the probabilistic LoS channel model, it first decoupled it into three sub-problem, then solved the three sub-problems one by one, by using the integer relaxation and successive convex approximation methods, and finally obtained the 3D flight trajectory of UAV by using the block coordinate descent method. Based on the instantaneous channel state information obtained during the UAV’s flight, it further proposed a real-time optimization algorithm for UAV speed and user scheduling. This algorithm formulated the optimization problem into a linear programming problem and solved it by using the interior point method. Simulation results show that compared to the existing benchmark algorithms, the trajectory optimization of UAV based on the probabilistic LoS channel model can significantly improve the secrecy rate of the system, and the proposed real-time optimization algorithm for speed and user scheduling can further improve the secrecy rate performance. [ABSTRACT FROM AUTHOR]

In order to solve the problems of unstable and low efficiency in the work space, a particle swarm optimization (PSO) algorithm with dynamic changes of inertia weight and learning factors was used to optimize the trajectory of 3-5-3 piecewise polynomial interpolation. Through the kinematic analysis of the forest work vehicle, four passing points in the working space were obtained, and the 3-5-3 piecewise polynomial interpolation was used for trajectory planning. Finally, the improved particle swarm optimization algorithm was used to optimize the trajectory running time under the kinematic constraints, and the optimization performance of the standard particle swarm optimization algorithm was compared. The results showed that the 3-5-3 piecewise polynomial interpolation curve using the improved particle swarm optimization algorithm had faster convergence speed, smaller fitness after convergence, and about 13% shorter running time, which effectively improved the working efficiency of the forest work vehicle. [ABSTRACT FROM AUTHOR]

This paper aims to solve the problems in the trajectory optimization during the cruise phase that the edge weights are closely related to the selection of the preceding path，and the calculation cost of the evaluation function is too heavy under different objectives like the least fuel consumption，the shortest flight time，and the lowest cost. First，a process is built，involving the GRIB2-format grid meteorological data interpolation and calculation of aircraft performance parameters. Second，the efficiency is augmented by the improvement of the A* algorithm evaluation function coefficient and the step size of performance calculation. Results for typical flight tasks under different optimization objectives are compared and the effects of factors such as cost index，mass of aircraft and flight level are discussed. The A* algorithm that incorporates the flight performance calculation into the edge weights，requires more calculation time than the traditional shortest path algorithm. However，compared with the Dijkstra’s algorithm，it can find the optimal trajectory more quickly under the same performance-based optimization objective. [ABSTRACT FROM AUTHOR]

An improved non-dominated sorting genetic algorithm Ⅱ（NSGA-Ⅱ）for solving the large-scale optimization problem of trajectory planning in the strategic stage is designed. Under the framework of the classic NSGA-Ⅱ，an adaptive crossover operator and an adaptive mutation operator are used to accelerate the convergence speed of the algorithm and improve the quality of the solution，and an evaluation index to measure the pros and cons of the Pareto solution set is given. Considering the introduction of large-scale fourdimensional trajectories inevitably increases the complexity of the problem，this paper proposes an effective strategic conflict resolution model，which aims to minimize the number of potential conflicts and the cost of conflict resolution. Using 1 472 flights during peak hours of China’s air-route network for example verification，the proposed algorithm is compared with the classic NSGA-Ⅱ algorithm and MOEA/D. The experimental results show that the improved NSGA-Ⅱ algorithm has a better optimization effect，can effectively resolve the conflicts between aircraft and produce less trajectory amendment costs. [ABSTRACT FROM AUTHOR]

Meta-heuristic algorithm-SVM is a typical framework of multi-classification evaluation model, which has important theoretical and practical significance in multi-classification comprehensive decision-making. Therefore, this paper proposed a multi-classification evaluation algorithm of an improved whale optimization algorithm using Lévy flight and elite opposition-based learning SVM（LFEO-BWOA-SVM）. It used Lévy flight strategy instead of spiral trajectory strategy to update position information effectively, and could overcome the deficiency of whale optimization algorithm which was easy to fall into local optimization. It introduced the elite opposition-based learning mechanism to increase population diversity and improved the global optimization ability of whale optimization algorithm. The simulation results show that the classification accuracy of LFEO-BWOA-SVM algorithm is 17.84% and 4.51% higher than that of traditional SVM and BP neural network, the accuracy is 98.73%, and the training time is 9.34% and 84.94% shorter than that of standard WOA-SVM and PSO-SVM, respectively. The experimental results show that the optimization ability and convergence speed of LFEO-BWOA-SVM algorithm are obviously improved, and the accuracy and rapidity are good. [ABSTRACT FROM AUTHOR]

In the port environment, due to the motion characteristics of unmanned aerial vehicle (UAV) the flight trajectory always deviates from the linear path between the detection points. In order to solve this problem, firstly, this paper used con structing isosceles triangle method to preprocess the given path, and then on the basis of minimum-snap method, added corridor constraint to the optimization objective function as inequality constraint, and established the deviation evaluation function to evaluate the deviation distance. It carried an experiment out in a simulation environment with a simplified quay crane model. The experimental data shows that the proposed method not only optimizes the time and length of the generated trajectory, but al so reduces the average deviation distance by 88.7%. At the same time, the UAV can track the generated trajectory well. Thus, in the simulation environment, the proposed method can generate a higher quality trajectory in trajectery optimization. [ABSTRACT FROM AUTHOR]

To improve the control accuracy and safety of autonomous landing of unmanned aerial vehicles （UAVs），we take a high-speed UAV as the research object，and adopt the total energy control system （TECS） in the steep descending section to track the descending trajectory with simultaneous changes of altitude and velocity. The velocity control is added to the pull-up section，and on the basis of the exponential pull-up，Gaussian pseudo-spectral trajectory optimization method is used to design the speed trajectory with monotonically reduced throttle. Meanwhile，the lifting velocity control law is designed based on active disturbance rejection control（ADRC）method to realize the accurate control of touchdown speed. In the end， an object model is built under the MATLAB/Simulink platform to simulate the UAV autonomous landing closed-loop control system，and the Monte Carlo method is used to verify the robust performance of the control system under the condition of uncertain parameters. Simulation results show that the proposed trajectory design method and control structure can meet the requirements of landing performance，and the control system has strong robustness. [ABSTRACT FROM AUTHOR]

Unmanned Aerial Vehicles (UAVs) have been commonly used for the plant protection in modern agriculture. Autonomous operation is a heated issue of UAVs development, while obstacle avoidance is one of essential abilities. If obstacles are not effectively avoided during automatic operation, the security of UAVs will be inevitably at risk. This study proposed a novel method of collision-free trajectory planning for multi-rotor UAVs, which used modified dynamic optimisation, thereby to deal with autonomous obstacle detection and avoidance. A quad-rotor UAV, Carto F4, equipped with the workload of 5 kg, was selected as the flight platform. A LIDAR, Rplidar S1, and a PIXHAWK flight controller were used on the UAV. Meanwhile, a high-speed computing module, NVIDIA TX2, was used for complex computation. The specific method of trajectory planning consisted of three procedures during optimisation. First, a probability grid map was established to serve as the environment map, using the binary Bayesian probability. Then, an optimal bi-directional Rapidly-exploring Random Trees (RRT) was developed to search a complete and low-cost path for the UAV. Specifically, a systematic optimisation included the application of both centroid bias sampling and online-rolling optimization. The centroid bias sampling was used for the mutual guidance in node growing, while the online-rolling optimization was used for the avoidance of repeated growing of nodes. A more efficient path was established according to the two steps. Third, a dynamic optimisation of full trajectories was applied, where the dynamic optimization of minimizing the fourth derivative of displacement was utilised to make the path to be a trajectory that was more in line with dynamic performance, thereby to achieve stable avoidance of obstacles. A minimum snap was employed during optimisation, where three types of constraints were added, containing planning constraints, continuity constraints, and dynamic constraints. Meanwhile, a probability grid map with high and low expansions was developed to ensure that the full trajectory did not interfere with obstacle areas. In-depth simulation test results illustrated that the re-planning duration of obstacle avoidance could be reduced by up to 23.69%, compared with the non-improvements, indicating that the dynamic optimisation made the trajectory more feasible and smoother. Moreover, the duration of planning of effective trajectories for obstacle avoidance was less than 0.33s, and the average speed of trajectory tracking of obstacle avoidance was not lower than 1.16 m/s. In addition, the extension rate of trajectories for obstacle avoidance was up to 20.82%, indicating that the efficiency and effectiveness of trajectory planning were improved. The proposed method of obstacle-free trajectory planning for multi-rotor UAVs can provide a sound of theoretical scheme and technical reference for the autonomous operation and obstacle avoidance of multi-rotor UAVs. [ABSTRACT FROM AUTHOR]

The redundantly driven parallel robots were considered. The Udwadia-Kalaba ( U-K) method was used to formulate the physical connections of the parallel mechanism as system constraints, and the closed-chain motion equations for the planar 2-DOF redundantly driven parallel robot were established. Firstly, the 2-DOF robot was divided into 3 unconstrained open-chain subsystems. The dynamic equations for the subsystems were obtained with the Lagrangian method. Then, the kinematic constraints were used to describe the physical connections between each subsystem and the end effector, and between each subsystem and the base. The constraint was differentiated and transformed into a 2nd-order Pfaffian standard differential form. With the U-K equations, the analytical solution satisfying the physical constraints was given. According to the U-K theory, the constraints can be added to the unconstrained open-chain system equations to establish the dynamics model for the planar redundantly driven parallel robot. In the trajectory tracking controller design, the desired position or velocity trajectory was formulated as a virtual constraint, and the constraint condition was transformed into a standard Pfaffian differential form. Then the U-K equations were used to solve the output torque required for each driving joint to satisfy a given trajectory constraint. This method does not require auxiliary variables such as Lagrangian multipliers or pseudo-generalized speeds, and can handle both holonomic and non-holonomic constraints. The numerical simulation and analysis results show that, the modeling and controlling method can effectively, systematically and quickly establish the dynamic analytical decoupling model for the planar 2-DOF redundantly driven parallel robot, and realize the high-precision tracking control along a given trajectory. [ABSTRACT FROM AUTHOR]

The foot end trajectory of the bionic quadruped robot plays an important role in its movement. MATLAB Robotics Toolbox has been used for modeling, solving the forward and reverse solutions and trajectory planning. For a structure such as a quadruped robot with only 3 DOF at the end, there are certain defects in the solution and simulation by this tool. In this study, by exploring the underlying function of the toolbox, the reason for the problem is that the “ikine” function was not applicable. The toolbox is targeted for secondary development by replacing the "ikine" function with the inverse solution formula. At the same time, the problem of increasing the multi-solution of the inverse kinematics of the optimization algorithm is optimized according to the principle of minimum angle change. The real-time dynamic simulation results of the set trajectory shows that the walking process is naturally smooth, and the joint rotation characteristic curve is within a reasonable range, which verifies the effectiveness and rationality of the optimization algorithm. [ABSTRACT FROM AUTHOR]

The parafoil homing trajectory should be processed and optimized in segments in order to realize the accurate airdrop and easy drop-down control during homing. A high precision 9-degree-offreedom dynamic model of parafoil system is established. A five-segment homing trajectory optimization model is established,in which the minimum energy consumption is taken as the objective function and the time consumption and turning radius are taken as the input variables. The optimal reference path of homing is given by using the five-segment homing trajectory as the initial condition and using the pseudospectral method to optimize the trajectory,and the energy losses in the five-segment homing and direct homing processes are compared and analyzed. The simulated results show that the five-segment homing trajectory optimization strategy proposed in this paper has the advantage of simple control function form and easy application. [ABSTRACT FROM AUTHOR]

An object loading robot used in limited space inside a vehicle is proposed to improve the loading efficiency, and the motion trajectory of its joint is optimized. An overall design scheme of loading robot is presented, in which the requirements for conveying of cylindrical materials and in-vehicle limited workspace are considered. A flow chart of joint movement is also worked out. Then a kinematic model of robot is established. Based on the kinematic model, the robot’s workspace is calculated. Higher order polynomial function is adopted to mimic the motion trajectory of robot joint. The particle swarm algorithm is utilized to optimize the parameters of higher order polynomial function, and the optimization progress is simplified by replacing the coefficient variations with interpolation time variables. Research results show that the robot’s workspace could cover the whole space inside vehicle, and satisfy the requirements for in-vehicle limited space. After optimizing the motion trajectory of joints, the robot can load materials smoothly, quickly and steadily. [ABSTRACT FROM AUTHOR]

It is difficult to study the influencing mechanism of explosive charges stability during the penetration into targets in a complex impact environment. The microscale hot-spot generation models which include crack friction and pore collapse are used to simulate the dynamic response,damage evolution and hot-spot generation of explosive charges during the penetration into the single-and multi-layer targets.The different generating mechanisms of hot-spot are analyzed through simulation and compared with the experimental results. The simulated results show that it is easy to generate the hot-spot in the explosive charges during the penetration into multi-layer target compared with single-layer target,and the explosive charges can easily be damaged more seriously under repeatedly loading and trajectory deflection in the penetration into multi-layer target,which also generates the hot-spot due to crack friction and pore collapse. The areas of head and tail of the explosive charges should be especially protected,where the hotspots are easily generated. The influence factors,such as penetration velocity,fracture toughness and initial porosity of explosive charges,are analyzed. The stability of explosive charges can be improved by reducing the stress amplitude,decreasing the oscillation times of explosive charges in a shell,increasing the strength of explosive material and reducing the initial defect of charge. [ABSTRACT FROM AUTHOR]

For the problem of high communication overhead and greater algorithm complexity, this paper proposed a trajectory tracking method based on CSI signal in the tracking process of the indoor environment. Firstly, it extracted AOA spectrum which represented the CSI target position (angle) probability and obtained the Doppler shift by MUSIC algorithm and AOA spectrum to determine the moving speed and position of the person. Finally, it used the improved trilateral positioning centroid algorithm to locate personnel, simulated moving track to achieve accurate indoor tracking and locating personnel. By comparison with other algorithms and different speeds of movement of persons, simulation results show that the proposed method can greatly improve the accuracy and stability of positioning. [ABSTRACT FROM AUTHOR]

The effects of the pilot response characteristics on tilt-rotor aircraft trajectory optimization after one engine failure is studied. An augmented flight dynamic model for trajectory optimization after one engine failure is developed with algebra equations describing the pilot controls in cockpit and differential equations describing the pilot response characteristics. A direct transcription method is employed to transcribe the optimal control problem into a nonlinear programming problem. XV-15 tilt-rotor aircraft is taken as the sample, the comparisons show that when the pilot response characteristics are considered in the trajectory optimization, the time histories of flight states, power required, thrust coefficient, longitudinal flapping angle and pilot controls become more relatively gentle with longer final distance and flight time. Besides, the longer pilot perception delay time, the longer time required for landing procedure, and the bigger touchdown speed, but the tendency of the pilot controls are basically the same. Therefore, the tilt-rotor trajectory optimization after one engine failure considering pilot response characteristics can provide pilots more useful references to perform the landing procedure after one engine failure. [ABSTRACT FROM AUTHOR]

In order to ensure the smooth construction of a large directional drilling pipe through Qin River, the construction unit carefully studied technical difficulties, made rational selection and kept rigid control of the maximum mud pressure, the speed of reaming, the viscosity and the gravity of mud and other key technical parameters, formulated the construction measures against the oozing slurry and took pre-reinforcing in the weak ground of the traversing route. It strictly controlled the guide hole construction trajectory, accuracy of entry angle and unearthed angle. In the course of drilling, mud pressure, drilling speed and other control parameters were corrected at any time when the mud pressure, drilling trajectory and mud circulation reflected the difference between the actual geological conditions and the design, achieved the goal of smooth drilling, no oozing slurry in the whole process and precise pipe location, as well as creating a number of domestic construction records by using directional drilling with double pipes across channel projects, such as the diameter of the pipeline diameter 1, 016 mm, the crossing length of 1,750 m and the maximum buried depth of more than 33 m. [ABSTRACT FROM AUTHOR]

Aiming at coalbed methane( CBM) well drilling problems of high dip angle and complex stress in the southern margin of the Junggar Basin, the influence of the coal seam dip angle, in-situ stress and building-up (dropping) on wellbore stability were studied based on weak plane theory,and a multi-objective constraint drilling trajectory optimization model was established. The results show that ① the dip angle of coal seam in Changji area is 10°-25° ,and partly reaches 2 5 ° -4 0 ° , which belongs to high steep coal seam. It has the characteristics of strong permeability anisotropy, strong stress anisotropy and strong rock mechanics anisotropy. ② When drilling horizontal well, according to the influence of coal seam dip angle on wellbore stability, it can be divided into working zone, transition zone and inversion zone. It is working zone when dip angle is between 5°and 25°. Drilling along dip direction and strike direction are the safest and most dangerous orientation,respectively. When dip angle reaches 6 5 ° ,it enters inversion zone, drilling along the dip direction and strike direction both become the safest orientation. The greater stress anisotropy, the greater collapse pressure and the smaller orientation range of safety drilling. ③ When drilling along coal seam, drilling along updip direction is proposed if the dip angle is less than 35°; drilling along down-dip direction is proposed if the dip angle is more than 65°; the wellbore safety is the lowest in the range of 3 5 ° -6 5 ° , then drilling along trend direction is proposed. It is the most dangerous building up (drop) section when the inclination angle is between 45° and 65°,building- up ( dropping) in coal seam should be avoided. ④ In order to reduce the collapse pressure from the landing point to the first target, S-type and J-type drilling trajectory types are proposed,the comparison results show that the trajectory designed in new method is shorter, less friction and torque than the trajectory' designed in conventional method. [ABSTRACT FROM AUTHOR]

A parametric missile aerodynamic coefficient modeling method is discussed for separation from aircraft. In this method, the total aerodynamic coefficients of the missile during the separation process are treated as the superposition of the free flow part and the disturbance part due to the non-uniform flow field influenced by the aircraft. Variable coefficient polynomial model is established to describe the disturbance part at different distances from the aircraft. For a given distance, the unknown parameters in the polynomial model are computed by using a multivariate orthogonal function-lease square method; then a hybrid optimization algorithm is adopted to establish the relation between these parameters and the distances. By comparing the data resulting from the presented method with the computational fluid dynamics (CFD) simulation data and the captive trajectory simulation (CTS) wind tunnel data, it is shown that the presented aerodynamic modeling method is efficient and accurate. To improve the safety level of the separation, a separation trajectory optimization problem in the longitudinal plane is established based on the above-obtained parametric aerodynamic model. The trajectory optimization problem is transformed into a nonlinear programming problem by using Gauss pseudospectral method and then solved by using sequential quadratic programming (SQP) algorithm. The results show that the optimized separation trajectory is able to ensure a safe and smooth separation process. [ABSTRACT FROM AUTHOR]

Aimging at the problems that the electro-hydraulic servo manipulator poor in motion precision and stability and the control model is nonlinear,the advantages of strong load capacity and large energy density was considered,and the manipulator motion control system was designed. Firstly, the position vector of TCP was showed by the method of closed chain vector; Secondly, five order B-spline interpolation method and improved particle swarm optimization algorithm were introduced to realize the optimal trajectory planning of TCP position; Finally, adopting grading control management solution, with conventional control strategy of PID, IL - PID, NDI , was used to realize the manipulator motion control of each joint. With simolation and experimental done in 5DOF manipulator, the results indicate that the motion control system can realize accurately control of designated movement in requirement of high load and high precision. [ABSTRACT FROM AUTHOR]

A dimension reduction optimization strategy based on trajectory shaping is presented to improve the accuracy of trajectory optimization. The proposed method is able to improve the performance of the direct trajectory optimization method in solving non-smooth trajectory optimization problem. According to the boundary conditions, the unknown trajectory is shaped using the Bezier curves with a few shape variables. The concepts of inverse dynamic and parametric transform are introduced to reduce the original problem to a lower dimensional optimal control problem. The result shows that lower dimensional problem tends to have a better conditioning number when it is solved by direct optimization method, and the accuracy of solutions is improved dramatically. The validation of the proposed method over conventional direct optimization method is demonstrated by the simulation results. [ABSTRACT FROM AUTHOR]

Re-entry trajectory optimization with complex constraints for hypersonic vehicles is a strong nonlinear optimal control problem with multiple phases and constraints. A trajectory optimization framework which adds the constraints successively based on Gauss pseudo-spectral method is proposed. The framework is used to build more accurate models of typical regular no-fly zone to provide multiple choices for mission plan, and then a successive approximation solving method is proposed to simplify the complexity of constraint model. In each iteration, the previous solutions to simpler problems are used as initial guesses to approach the solution of the original problem. Numerical examples for minimizing time of trajectory with multiple constraints including heat flux of stagnation point, overload, dynamic pressure and no-fly zone constraints are simulated to demonstrate the proposed method. The simulation results show that the phased adding constraints trajectory optimization framework has better robustness. [ABSTRACT FROM AUTHOR]

This study proposes a modified A* algorithm to solve the problem of real-time unmanned air vehicle(UAV) path planning in a large 3D battlefield environment. Since the UAV has to meet the requirements of high survival rate and low fuel consumption in low-altitude penetration, the algorithm took the flight altitude, detected probability and flight length into consideration to search the optimal flight path between two waypoints. Meanwhile, to satisfy the UAV performance constraints, such as safety altitude, rate of climb, and radius of turn, the author suggested a series of optimization algorithms to get the final flyable path. Experimental results show that these algorithms have good convergence and high efficiency and provided a optimal trajectory for decision-makers. [ABSTRACT FROM AUTHOR]

A rapid reentry trajectory planning method based on nonlinear model prediction theory is studied for the new lifting reentry vehicle with many constraints. Since the lifting reentry characters and mission requires need to satisfy strong terminal constraints, the nonlinear predictive model and the receding optimization scheme are used to convert the nonlinear optimization into the linear optimization objection, and a quadratic programming is used to solve it. The simulation results show that the proposed method can generate a high precision reentry trajectory with strong terminal constraints. [ABSTRACT FROM AUTHOR]

When a homing missile tracks a target, it may fail to lock the target because of complicated background. For example, when a missile attacks a target in look-down mode, the missile' capability of intercepting or acquiring a target is weakened by complicated surface background and clutter. A new modeling method which regards the ideal line-of-sight as the control objective is put forward. And an optimal guidance law is designed based on restraining the terminal direction of relative motion between missile and target and the trajectory overload. The guidance law is used to control the motion of missile in a direction vertical to ideal line-of-sight. The simulation result shows that this method can meet the requirement of terminal trajectory shaping better, distribute the overload more reasonably and decrease the influence of ground background and clutter on target tracking effectively. [ABSTRACT FROM AUTHOR]

The 6-degrees of freedom trajectory equations for rocket projectiles are established, and a new real-time impact point prediction (IPP) approach is proposed based on perturbation theory. Assuming that the rocket projectile flies along the nominal trajectory without disturbance, the detailed calculation process of the dispersion in impact point is presented. The prediction coefficient is calculated using a fire control computer on the ground, and IPP is carried out using the rocket-borne computer during flight. As a result, the IPP process is simplified. Finally, the simulation and flight tests of 122 mm rockets is accomplished. The results show that its prediction precision is higher under any condition. At the same time, the results demonstrate that the time consumed to predict the impact point is about 167 ns, which is much less than the control cycle time of 2 ms. [ABSTRACT FROM AUTHOR]

The problem of optimizing the maximum range of a glide guided bomb is studied based on the principle of solving optimal control problems using the Radau pseudo-spectral method. The dynamic model of the guided bomb is nondimensionalized. Combining with the Pontryagin minimum principle, the analytic solution of the optimal control and the first-order necessary condition are derived. The trajectory optimization problem is translated to a nonlinear programming via the Radau pseudo-spectral method. Based on covector mapping principle, an optimality verification method is presented for the numerical solution. Simulation results show that the Radau pseudo-spectral method can provide a highly valuable optimal solution for engineering application. Compared with the conventional maximum lift-to-drag ratio gliding trajectory, the trajectory after optimization can be extended by more than 10%. [ABSTRACT FROM AUTHOR]

To study the effects of curved earth's surface on the ranges of projectiles and rockets, a modified rigid body trajectory model is built based on Kane method in which the curved earth's surface and the changes in both the size and direction of the gravity acceleration are considered. The concept of geodesic line is introduced to the range calculation of projectiles or rockets. Four calculation methods for the range under the condition of curved earth's surface are discussed, such as inverse solution of geodetic problem and so on. The range errors calculated with the modified rigid body trajectory model and the ordinary rigid body trajectory model are compared. The result shows that the spheroidal distance algorithm has a high calculation precision in the range of 300 km, and can be used to calculate the range on the curves earth's surface. The modified rigid body trajectory model is more accurate than the ordinary rigid body trajectory model in the consideration of the curved earth's surface. [ABSTRACT FROM AUTHOR]

In order to increase the impact dispersion accuracy of submunitions, a method of self-adaptive cabin opening is put forward. A trajectory model of submunition is built based on the research on the flight dynamics of spin-stabilized shrapnel. The impact dispersion of subminution is simulated by using this model. According to the errors got from the theoretical and practical trajectory results of a certain ejection point of the shrapnel, the effects of the errors on the impact dispersion of submunition are analyzed through simulation comprehensively. With the help of the simulation results, a shrapnel self-adaptive cabin opening method with modified ejection point is proposed to improve the impact dispersion accuracy of submunition. A modified formula for the best cabin opening point of spin-stabilized shrapnel is deduced. The results show that the method used in this paper can be used to increase the impact dispersion of submunitions by 26.3% in horizontal and 53.8% in vertical. [ABSTRACT FROM AUTHOR]

In real world driving drivers have to determine a desired trajectory within the pavement width they can use before following it. Therefore, the model for desired trajectory decision is an indispensable part of the driver model. In this context, we provide a full method used to deicide desired trajectory for complex mountainous highways. The strategy for deciding desired trajectory is uselecting the trajectory point on the pre-view cross section". Then the four objective functions corresponding to minimum trajectory length, minimum trajectory curvature, minimum trajectory curvature changing and lane keeping were presented according to the typical driving pattern on real roads. After that the four constraint conditions of driving within the pavement, obstacle avoiding, lateral driving stability and bend passing ability were presented. The next, the receding horizon algorithm used to determine the desired trajectory for complex highways was designed according to the decision process of a real driver. Examples of trajectory determination on two mountainous roads and a racing track were given in the end of the paper, the results show that the simulated trajectories coincide with the ones we wanted and the ones we observed on real roads, so the reliability of presented models was validated. [ABSTRACT FROM AUTHOR]

For the search problem of mobile targets in an uncertain region after long-range penetration, a long-range penetration and cooperative search path decision-making method of multiple UAVs is proposed. The basic planar diffusion model is improved, and an uncertainty region diffusion model is built by considering the target motion and the circumstance constraints. The strategy of the penetration decision and trajectory optimization search decision-making is researched for mobile target based on the algorithms of potential field and receding horizon control. The proceed function of the cooperative search is proposed in consideration that the uncertainty reduce proceeds, average uncertainty and integration cross, which is the trajectory optimization rule of the cooperative penetration and search decision-making. The simulation was carried out. The simulation results show that the algorithm is useful in dealing with the emergent threat and the uncertainty area diffusion, and can complete the long-range penetration and the cooperative search mission of multiple UAVs. [ABSTRACT FROM AUTHOR]

For the penetration probability of air-to-ship missile adopting traditional flight trajectory is poor when it is intercepted by long-range ship-to-air missile, a scheme of modifying the descending phase trajectory to spiral maneuver dive trajectory is proposed. The design process of variable structure guidance law with terminal angular constraint is analyzed. On this basis, a kind of spiral maneuver variable structure guidance law is proposed. It can be used to guide the air-to-ship missile to realize the spiral maneuver dive trajectory, and ensure that the air-to-ship missile turns into the low altitude cruise phase in the end of the descending phase. The simulation results show that the proposed spiral maneuver variable structure guidance law improves remarkably the penetration probability of air-to-ship missile against the long-range ship-to-air missile. [ABSTRACT FROM AUTHOR]

In the paper, a hierarchical theory based cooperation module with 3 layers, named cooperative sensing-, situation comprehending-, and global replanning-layer, is introduced to address the problem of multiple unmanned air vehicles (MUAVs) dynamic cooperation under uncertain environment. Specifically, a layer cooperative operator (LCO) is proposed for the purpose of target sensing and recognition, and window optimized potential field (WOPF) strategy is adopted for obstacle avoidance and environment adaption consideration, while layer sense engine operator (LSEO) is suggested to enhance the module's ability of global replanning and MUAVs trajectory optimization. Simulation results indicate the promising potential of our proposed module in the area of MUAVs autonomous cooperation under uncertain environment. [ABSTRACT FROM AUTHOR]

A new method to deal with the constrained optimal control problems is developed by introducing additional variables. With the additional variables, the process constrains are transformed to terminal constrains. The method is used to design a Herbst maneuver trajectory based on the three-degree-of-freedom flight dynamic model in the same initial condition and two different final conditions. The optimal control variables are the angle-of-attack, the roll angle about the velocity vector and the throttle of the engine. The results show that the method is rapid and effective in processing multivariate optimal control problems, and it can be recommended as a tool to design combat aircraft maneuver trajectory for a trajectory data base. [ABSTRACT FROM AUTHOR]