Shen Lin-cheng

A new feedback linearization LQR control for attitude of quadrotor

This paper presents a new robust and stable controller for attitude of quadrotor. We proposed a combination of feedback linearization and LQR (linear quadratic regulator) control strategy. To our best acknowledge, this method is firstly employed to stabilize the attitude of the quadrotor with disturbance. Numerical simulations demonstrate the stabilizations and robustness of the control system under nominal conditions. Furthermore, a bounded disturbance was added to the system in flight test, and the results also illustrate the successful behavior of the controller proposed.

Camera Calibration of Thermal-Infrared Stereo Vision System

Accurate and efficient thermal-infrared camera calibration is important for advancing computer vision research within the thermal modality. This paper proposes a specially designed calibration pattern for stereo vision systems. Small circular thermostatic heaters are used as sources of thermal radiations so that the pattern can present obvious thermal contrast. The circular features can be easily and accurately extracted. Additionally, the paper proposes a calibration algorithm to exploit the centers of circles as feature points with high precision. Experiments were carried out in outdoor environment of large field of view. From the experiments we have obtained the mean re-projection error of calibration in 0.786 pixels at a distance of 10 meters. The proposed method is simple and efficient.

A new method for mitigation of end effect in empirical mode decomposition

Empirical mode decomposition(EMD) is a time-frequency analysis method for non-stationary and nonlinear signal. In the iteration process of EMD, at least one data point outside each end is required to build the spline. However, the extending data points which are not chosen properly will cause vibration and distortion phenomenon in EMD. In order to mitigate that end effect, a novel extrema points extending method is proposed: End mirror extending is used in high frequency, while least square polynomial extending is used in low frequency. Numerical result proves that the proposed method can mitigate the end effect in EMD effectively with minor decomposition error.

Terrain aided navigation using PDAF

Terrain aided navigation (TAN) is the concept of using terrain height variations below the aircraft to render a position estimate that is used to bound the error in the INS. A new TAN approach using PDAF (probabilistic data association filter) has been proposed to overcome irresolvable ambiguities in the correlation function. The basic idea of this approach is convert correlation function value to the probability of position estimate being actual position of the aircraft. The data association problem between positions estimated and actual position is solved by PDAF technique. Its shown via a set of simulations that the method can improve the performance of TAN compare to TERCOM.

Research on swimming by undulatory long dorsal fin propulsion

The kinematics of steady forward swimming of Gymnarchus niloticus is described. The geometric features of the body and locomotive characteristic and parameters of the flexible dorsal fin are discussed. On the basis of observation and experimental data, a simplified kinematic model on locomotion of the undulatory long dorsal fin propulsion is promoted. The hydromechanical performances of the undulatory long dorsal fin propeller of G. niloticus are estimated with the large-amplitude elongated-body theory. The hydromechanical efficiency of the undulatory long dorsal fin system ranged from 81.664% to 86.420% over a speed range of 0.728–0.985 length · s−1. It is suggested that the undulatory long dorsal fin propulsion is an adaptation to swimming with high hydromechanical efficiency.

A new calibration method for vision system using differential GPS

The Pan-Tilt Unit (PTTJ) and camera composed a vision system, which can be used in vision measurement. In this paper, a new calibration method for this vision system using differential GPS (global positioning system) is described. The calibration method is an efficient solution for large field of view. The proposed method has advantages in speed, convenience and pertinence. The experimental results show the accuracy is acceptable for the outdoor environment.

Notice of Retraction Semi-parametric regression model prediction method based on empirical mode decomposition

Semi-parametric regression model prediction method based on empirical mode decomposition was studied in this paper. Firstly, basic idea of the empirical mode decomposition was introduced, and the improved algorithm was proposed to mitigate the end effect in the iterative shift process. Secondly, least squares method was employed to estimate the parameter β based on the trend component of empirical mode decomposition, and the non-parametric g(·) was estimated through building the AR models of the intrinsic mode functions. The vector matrix was computed by Yule-Walker method. Finally, time series prediction of two nonlinear systems was analyzed based on the semi-parametric regression model. The results show that the proposed model predictive method is fit for nonlinear and non-stationary time series estimate.

A probability-based terrain-aided navigation approach and its relative terrain navigability analysis

Based on the probability distribution differences of terrain height samples, this paper presents a new terrain-aided navigation technique called probability-based terrain-aided navigation approach. The entropy-based navigability criterion is introduced to analyze the terrain navigation quality associated with this approach.

UAVs flocking and reconfiguration control based on artificial physics

This paper investigates the flocking and reconfiguration control problem of multiple unmanned aerial vehicles (UAVs) system by using a modified artificial physics (AP) method. Firstly, in order to dirve the multi-UAV system with double-intergrator dynamics to form the uniform distribued standard formation, we redefine the attractive and repulsive forces in the traditional artificial physics method, and analyze the stability of the flocking control method using the LaSalle invariance principle accordingly. Immediately, we develop an improved strategy regards to the local optimal solution of the flocking problem in the serial number independent case. Then, we explore the reversible and exclusive bijective transformation between the standard formation and an arbitrary formation. Using the bijective transformation, we propose a flocking control method to form the arbitrary formation, and futher extend to the flocking reconfiguration problem, such as flocking contraction and expansion, formation switching and flocking with obstacle avoidence. In order to verify the effectiveness of the proposed flocking and reconfiguration control method, we construct a multiple quadrotors coodination simulation platform based on the robot operating system (ROS) and Gazebo simulator. The simulation results demonstrate the effectiveness of the flocking and reconfiguration control method. Finally, we expand our artificial physics based flocking control method to the multiple fixed-wing UAVs system, and the effectiveness is verified in a semi-physical simulation environment for multi-UAV coodination by using X-Plane flight simulaor and the UAV autopilot.

ECNP-based method of distributed dynamic task allocation for multiple observation satellite planning

A extended contract net protocol(ECNP) is introduced to solve the dynamic task allocation for multiple satellites collaborative planning system(MSCPS) in which the environment and capabilities of each Agent can dynamically change with time. Acquaintances trusts based announcing bidding, adaptive bidding with swarm intelligence and multi-attribute decision based fuzzy evaluation bidding method are proposed in ECNP; Experiment results show ECNP can decrease communication cost and balance energy cost, hence solve task allocation effectively.