Qi Naiming

Fractional PID controller design of hypersonic flight vehicle

In the process of re-entry of hypersonic flight vehicle, attitude control model is a complex object of fast time-varying parameters of a wide uncertain range. This paper design fractional order PID controller to increased the complexity of the controller designed using modern control methods. Fractional order PID (FOPID) controller inherits the advantages of the traditional PID controller and has stronger robustness and better control quality. In this paper, Fractional order PID controller is achieved by optimal Oustaloup digital algorithm and based on time-varying nonlinear model of hypersonic flight vehicle. Use D-decomposition to analyze the affect to Mach number and angle of attack stability region caused by the order of Fractional order PID. Simulation results show that Fractional order PID controller not only improves the control quality, but also is not sensitive to the changes of system parameters, the stability of hypersonic flight vehicle can be achieved within a wide range.

The Trajectory of Anti-ship Ballistic Missile Design and Simulation

In this paper, a new trajectory design method for anti-ship ballistic missile is presented. Firstly, the trajectory is decomposed into multiple sub-trajectories according to the number of burn. Then, a genetic algorithm method is proposed to optimize the multi-pulse trajectory. In order to verify the validity of the proposed design method and investigate the influence of the pulse increment, this paper carried out a number of simulation. The results of the simulation show that the ballistic missile can attack the slow moving targets on the sea and can quickly plan a feasible trajectory before launching.

Differential game strategy in three-player evasion and pursuit scenarios

A conflict of three players, including an attacker, a defender, and a target with bounded control is discussed based on the differential game theories in which the target and the defender use an optimal pursuit strategy. The current approach chooses the miss distance as the outcome of the conflict. Different optimal guidance laws are investigated, and feasible conditions are analyzed for the attacker to accomplish an attacking task. For some given conditions, the attacker cannot intercept the target by only using a one-to-one optimal pursuit guidance law; thus, a guidance law for the attacker to reach a critical safe value is investigated. Specifically, the guidance law is divided into two parts. Before the engagement time between the defender and the attacker, the attacker uses this derived guidance law to guarantee that the evasion distance from the defender is safe, and that the zero-effort-miss (ZEM) distance between the attacker and the target is the smallest. After that engagement time, the attacker uses the optimal one-toone guidance law to accomplish the pursuit task. The advantages and limited conditions of these derived guidance laws are also investigated by using nonlinear simulations.

Design and control of a position servo system in the zero gravity simulation of space manipulators

For the zero-gravity simulation of space manipulator, a position servo system is designed in this paper. The position servo system is composed of five servo platforms, which are used to track the joints of space manipulator, to ensure the slings keep vertical when the space manipulator is moving. Each servo platform consists of two CCD cameras, two servo motors, two orthogonal linear motion systems and a control computer. Using CCD cameras, the relative distance between manipulator joint and servo platform can be measured with no contact. Based on the measured distance information, platforms are controlled using PD controller to track the joints of space manipulator. In order to verify the tracking accuracy of servo platform with certain measurement error, numerical simulations are implemented. Simulation results show that the designed servo system can satisfy the zero-gravity simulation requirements of space manipulator.

Experimental study on the multi-dimensional microgravity simulation system for manipulators

Designing a system to simulate multidimensional movement of complex spatial mechanisms under microgravity condition is the focus of experimental research on ground simulation of manipulator in microgravity environment. A “multidimensional intelligent air-bearing” is designed, which consist of a vertical lifting system, a PID controller, a servo motor and an air-bearing. It breaks the limitation that traditional air-bearing can only realize zero-gravity simulation of the planar movement and realizes microgravity simulation of vertical lifting movement. Experiments are carried out, and results show that during the multidimensional movement of spatial mechanisms, the designed system can provide a support to counteract the gravity real timely and realize the simulation of spatial microgravity environment accurately.

Hybrid Genetic Algorithm Gauss Pseudospectral Method for the Electric Sail Trajectory Optimization

The electric sail is an innovative propulsion concept which uses the solar wind dynamic pressure to produce a thrust without the need for reaction mass. The electric sail is consisted by many tethers which are connected to a solar-powered electron gun. The electron gun emits electrons to maintain the tethers at a high positive potential. The electric field generated by the tethers reflects the solar wind ions to generate a thrust. In this paper, a hybrid genetic algorithm Gauss pseudospectral method is proposed to optimize the trajectory of the electric sail. The initial guesses for the state and control histories used in the Gauss pseudospectral method are interpolated from the best solution of a genetic algorithm. The proposed hybrid approach effectively includes global search ability of genetic algorithm and the high convergence rate of sequential quadratic programming. The numerical results show that the hybrid optimization method has the capability to search the feasible and global optimal solution of the electric sail trajectory without any initial value guess.