Online guidance for hypersonic vehicles in glide-reentry segment

In view of the guidance problem of the hypersonic vehicles in the glide-reentry segment, an online guidance strategy based on improved particle swarm optimization and whale algorithm was proposed. By considering its constraint model and shift conditions, a process constraint and terminal constraint model were established. To shorten the trajectory generation time and reduce the calculation amount of the algorithm, a height-range flight profile that could automatically meet the constraints of terminal height, path angle, and range was designed. Based on the premise that the drag coefficient is a constant value, a numerical solution of velocity that satisfied the range constraint was derived. Based on the above model, a three-parameter optimization model was designed to realize the control of the terminal conditions. To optimize the process constraints, an improved whale algorithm combining the whale algorithm and particle swarm optimization algorithm was proposed to overcome the shortcoming of precocious convergence of the particle swarm optimization algorithm, improve the solution efficiency, and minimize the heat flow rate during the flight. Then, through the method of segmenting the trajectory, an online guidance method based on the mid-point was proposed to update the longitudinal profile online to meet the terminal constraints. The simulation results show that the proposed method can efficiently solve the optimal flight trajectory.