Research On Vision-Based Guidance And Landing Of Unmanned Helicopter

Novel unmanned helicopter (NUH) owns special airframe structure and aerodynamic configuration that are different from conventional helicopter's and will play an important role in many application situations. As soon as NUH can automatically approach and land to the landing pad using computer vision, the manpower and material resource consumptions can be significantly reduced. This method's merits include high precision, low power dissipation, safety and reliability. Vision-based guidance and landing technology is a new flight control and navigation technology of unmanned helicopter, the research on it has great application value. According to this target, a vision-based guidance and landing control scheme was proposed, in which the NUH automatic approaching and landing was divided into the guidance stage and the landing stage. Main research contents included some key technologies such as NUH mathematics modeling, landing control, design and verification of principle of vision algorithm at each stage.To meet the necessity of NUH vision-based guidance and landing control, a NUH nonlinear model was built using aerodynamic principle modeling method. NUH flight dynamics characteristics were analyzed. The NUH trim calculation in hover condition was completed. A NUH linear model was deduced using linearizing method under the assumption of small perturbation. A comparison analysis about control responses of nonlinear and linear model was conducted. It was demonstrated by simulation that the linear model can be applied to NUH vision-based guidance and landing control design.NUH has open-loop instability and special control response coupling. NUH hover stability augment system was designed using EA method. The effects on NUH close-loop stability and maneuverability with different eigen-structure configurations were discussed. NUH hover/landing control system was designed using EA method combined with inner-outer-loop control architecture. The inner control loops in which the stabilizing and control of angular rates and vertical velocity were implemented were built using EA method. The attitude angular control loops were constructed by extending the inner loops: the outputs of the inner loops were integrated first; then as feedback signals, the integrated outputs were compared with the setting attitude angular signals; eventually the attitude angular error signals were amplified with proportional controllers and sent to the inner control loops as input commands. The control loops of linear velocity and position were implemented similarly using above method. It was demonstrated by NUH hover/landing simulation that the designed inner control loops can realize well decoupled and quickly angular rate commands tracking, and that the outer control loops have good hover position hold and landing trajectory following abilities.A vision-based guidance principle scheme for the NUH approaching stage was proposed. A corresponding VGA was designed. The central point position and the size of the guidance target were decided and calculated using image processing. These were treated as vision measured data. The inertial data and the vision data were fused using EKF formulation in which the estimated result from inertial data was revised by vision measurement. Then more precise estimated NUH positions were calculated. Using the estimated position as feedback, the position control loops carried out NUH to approach the landing pad. Feasibility of vision-based guidance scheme was demonstrated with vision-in-loop guidance simulation.A vision-based landing principle scheme for the NUH landing stage was proposed. A corresponding VLA was designed. The image position and velocity of corner points of the landing target in different images were calculated using image processing. The motion parameters of camera were estimated using the correspondences of corner points in different images. The estimated angular rates, attitude angles, velocities and the relative position to landing target of NUH were get. Treating the estimated motion parameters of NUH as state feedbacks for inner control loop and as attitude, velocity and displacement feedbacks for outer control loop, hover/landing control was implemented. Feasibility of vision-based landing scheme was demonstrated by vision-in-loop landing simulation.To verify the vision-based guidance, landing and control algorithm, a scheme of special moving platform experiment was proposed. The design and implement of components of the platform, such as the platform frame, the orienting and locating devices, the moving control system and the embedded vision system, were described. By the ground experiment, it was demonstrated that the designed embedded vision system can effectively execute the image acquisition and processing during NUH vision-based guidance and landing.