ABSTRACT The severe radial distortion of ultra‐wide field of view (FOV) fisheye camera results in poor model fitting and challenges in calibration board detection. In this paper, a novel calibration method for ultra‐wide FOV fisheye cameras is proposed based on improved camera model and SE(3) image pre‐correction. Initially, a method to extend the maximum fitting FOV of the camera model to over 180 degrees is proposed. Subsequently, a calibration board detection approach is proposed using SE(3) image pre‐correction. Specifically, image pre‐correction is incorporated into the camera calibration process, utilizing SE(3) to define the pre‐correction plane. Calibration boards are detected within the pre‐corrected images, enhancing the reliability, accuracy and speed of board detection in distorted images, consequently increasing the control point's maximum FOV. Lastly, the improved camera model and SE(3) image pre‐correction are integrated into a feedback‐based camera calibration system for ultra‐wide FOV fisheye cameras. Operating with real‐time or offline video streams as input, this system autonomously selects calibration key frames, optimizes camera parameters and calibration board poses in real‐time. Simulation and real‐world experiments verify the effectiveness of the proposed method, leading to a 62% increase in the achievable maximum FOV.

In this paper, we propose a novel mapping-planning framework for autonomous quadrotor navigation. First, a polyhedron-based mapping algorithm is presented to fully exploit the information of the onboard sensor data. Polyhedra are generated to approximate the segmented clusters of occupied voxels. Then, customized data structures are designed to extract information for motion planning in real time. With complete knowledge of the shape, position, and number of the observed obstacles, we can conveniently generate smooth trajectories with sufficient obstacle clearance along the most desired direction. Before searching for the initial path, a local topological graph is constructed to keep the path expanding in the most favorable topology class. The following path search is segmented based on the graph vertices, which allows fast convergence. The refined trajectory is obtained after smoothing, and large deviations are penalized in the formulated optimization problem to preserve the original clearance. Finally, we analyze and validate the proposed framework through extensive simulations and real-world quadrotor flights.

In this paper, we revisit the inconsistency problem of EKF-based cooperative localization (CL) from the perspective of system decomposition. By transforming the linearized system used by the standard EKF into its Kalman observable canonical form, the observable and unobservable components of the system are separated. Consequently, the factors causing the dimension reduction of the unobservable subspace are explicitly isolated in the state propagation and measurement Jacobians of the Kalman observable canonical form. Motivated by these insights, we propose a new CL algorithm called KD-EKF which aims to enhance consistency. The key idea behind the KD-EKF algorithm involves perform state estimation in the transformed coordinates so as to eliminate the influencing factors of observability in the Kalman observable canonical form. As a result, the KD-EKF algorithm ensures correct observability properties and consistency. We extensively verify the effectiveness of the KD-EKF algorithm through both Monte Carlo simulations and real-world experiments. The results demonstrate that the KD-EKF outperforms state-of-the-art algorithms in terms of accuracy and consistency.

The 6-DOF simulation system has many error factors. To reduce error magnitude and raise simulation precision, the error model is established. By analyzing the basic rules of systems with error, the composing method of characteristic matrix can be put forward. Based on characteristic matrix and multi-body kinematics, synthesis error model including static and dynamic errors are obtained. The dynamic response and vibration of the beam, which is subjected to a moving table, is chiefly analyzed. Based on Timoshenko's beam theory and Euler-Lagrange equation, the equations of motion for the beam system, which are composed of translation errors and rotation errors of the beam, are obtained. This method can offer academic reference to error synthesis model and compensation for 6-DOF simulation system

In this paper, we study H/sub /spl infin// control for multirate sampled-data system with time-delay. In allusion to the problems of time-delay and multirate sampling, we describe the system with a time-varying jump system characterization. Then basing on the technique of continuous lifting, the hybrid, linear, time-varying, jump system is isometrically mapped to a discrete-time, linear, time-varying system with infinite-dimensional input-output spaces. Finally by making use of the definition of the system function for a discrete-time, time-varying system and the property of symplectic pair, the infinite-dimensional system is transformed to an equivalent discrete-time system with finite-dimensional input-output spaces which can be disposed with well developed H/sub /spl infin// control theory. As a result, the proposed design method can solve H/sub /spl infin// control problem for multirate sampled-data system with time-delay.