Dewei Zhang

This paper investigates a control scheme for the visual servoing of a legged mobile robot equipped with a fixed monocular camera. The kinematics of the legged mobile robot and trifocal tensor-based visual servoing are employed to allow the robot to achieve the desired location. By investigating the trifocal tensor between the initial, current and desired location, the approach has no need for transcendental knowledge of the three-dimensional geometry of the observation target. The feature points are directly extracted from the images to evaluate the trifocal tensor. Furthermore, a controller is designed for visual servoing task, and a Lyapunov-based approach is used to analyze the stability of the control system. With the aid of MATLAB software, a simulation is implemented to verify the effectiveness of the proposed method.

Since the missile dynamical system in the pitch plane is nonlinear, uncertain and non-matched, its integrated guidance and control is nontrivial. In order to cope with this problem, an adaptive back-stepping based sliding mode control algorithm is proposed in this paper. Firstly, the sliding surface of the virtual control variable is defined thanks to the strong robustness of sliding mode control. Secondly, it is highlighted that the calculation scales with the number of the virtual variables in back-stepping control. To deal with this problem, an adaptive sliding mode control is used to estimate the upper bound of the uncertainties and to simplify the control system design. The closed-loop stability has been proven based on Lyapunov theory. Finally, the simulation results have been reported to witness the validity of the algorithm, which show that the proposed approach can reject the target uncertainty and have a satisfactory control performance.

According to the characteristics of complex spatial mode of long booster clustered launch vehicle, it is not suitable to derive the dynamic equations based on the simplified model of single beam considering only core rocket. In this paper, the long booster clustered launch-vehicle is simplified to a multi-beam model considering core and boosters. Then, due to the high proportion of the liquid propellant in the total mass of the launch vehicle, on the basis of the multi-beam model, a dynamic equation considering the elastic deformation and the liquid sloshing is established. The dynamic characteristics of the launch-vehicle and the interaction between liquid sloshing and aeroelasticity are studied by simulation. Based on the multi-beam model, the connection types between the core and the booster rocket are simplified to an elastic connection. The influence of the connection on the dynamic characteristics of the launch-vehicle is discussed. The results demonstrate that the multi-beam model can more fully reflect the dynamic characteristics of the long booster clustered launch-vehicle, and the connection form between the core and the boosters also has an important effect on the liquid sloshing and the elastic deformation.

A reliable nonlinear dynamic model of the quadrotor is presented. The nonlinear dynamic model includes actuator dynamic and aerodynamic effect. Since the rotors run near a constant hovering speed, the dynamic model is simplified at hovering operating point. Based on the simplified nonlinear dynamic model, the PID controllers with feedback linearization and feedforward control are proposed using the backstepping method. These controllers are used to control both the attitude and position of the quadrotor. A fully custom quadrotor is developed to verify the correctness of the dynamic model and control algorithms. The attitude of the quadrotor is measured by inertia measurement unit (IMU). The position of the quadrotor in a GPS‐denied environment, especially indoor environment, is estimated from the downward camera and ultrasonic sensor measurements. The validity and effectiveness of the proposed dynamic model and control algorithms are demonstrated by experimental results. It is shown that the vehicle achieves robust vision‐based hovering and moving target tracking control.