Zhang Daibing

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.

Autonomous control of running takeoff and landing for a fixed-wing unmanned aerial vehicle

This paper concerns about automatic flight control strategies for the running takeoff and landing of fixed-wing unmanned aerial vehicles (UAVs). Firstly, a dynamic model of fixed-wing UAVs is developed. Then the takeoff and landing control strategies are designed. The flight control strategies are designed to be segmented. A fixed-wing UAV named “Petrel” is used as an experimental platform. Finally, the flight experimental results are proposed to validate the automatic running takeoff and landing controller.

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.

An approach to ground target localization for UAVs based on multi-sensor fusion

In this paper, an approach based on multiple airborne sensors fusion to ground target localization for UAVs is proposed, which is the basis of UAVs applications, such as obstacle avoidance, target confirmation, etc. Challenges from accuracy improvement and system disturbance are considered. Sensor information is obtained by a visual sensor, GPS, and IMU modules. Traditional methods are mainly aimed at an upright position for visual sensors. First of all, an online multi-sensor calibration method using GPS is designed, calibrating the orientation of the visual sensor to the UAVs location. Then the target can be detected using Adaboost algorithm based on acquisition information of different visual sensors. And information obtained by real-time GPS, IMU, altimeter, and visual image based on Kalman filter is fused for target localization. Finally a D-S method for estimating the confidence level of target location is designed for perception disturbance. Experiments are implemented on rotor aircrafts and fixed-wing UAVs and the results show that the method, as feasible as it is, can effectively percept disturbance and improve location accuracy of a certain target.

A method of visual sensor employment planning for UAV target detection

Aiming at the wide variety of airborne visual sensor, this paper presents a method of visual sensor employment planning for UAV target detection. Firstly, according to the adaptive range of the image recognition algorithm and the probability of target recognition, the reasonable position of airborne visual sensor is studied. Then, the influence of external environment contrast and visibility for target detection or recognition is analyzed. Finally the model of a UAV sensor is proposed based on the characteristics of Bayesian probability model. The effectiveness and feasibility of this method are indicated by simulation and practice experimental results.

Vision-based Pan-tilt unit error measurement

As a ground-based visual guidance system for autonomous UAV landing. In this paper, the cameras mounted on PTUs are used to dynamically measure the movement parameters of the UAV during the approaching phase. Owning to the limitation of manufacturing precision, there will be kinematic errors of PTU. In order to ensure the accuracy of UAVs attitude obtained, the exact error of PTU should be obtained and compensated. In this paper, we only adopt the camera of system to measure the error of PTU with no other sensors. Prior to the measurement, the camera should be calibrated. Then the calibrated camera mounted on PTU captures the chessboard of fixed position to obtain the extrinsic matrix of the PTU. By comparison between the real changes of PTUs attitude and ideal changes, we could obtain the exact error of PTU. According to the distribution of the error, we adopt the spline curve modeling and compensate the errors. The results shows, the errors are reduced significantly.

Research on New Neural Oscillator in CPG Model Used in Robotic Fish

CPG control method is a modern control way in robotic control area. The problem is how to design a CPG model which can control the robot well. Neural oscillator is an important part in CPG model, in this paper, a new kind neural oscillator has been designed for CPG model. With this new neural oscillator, detailed analysis work has been done. The most achievement thing is the meanings of the parameters in CPG model are clear. With these parameters, the amplitude and the period of the CPG model’s output can be set to fit the robotic control. In this paper, we make a three-joint robotic fish as prototype, the simulation results show the new neural oscillator in CPG model can well used in robotic fish control.

State-of-the-art and Key Technologies of Fish-like Propulsor

Fish-like propulsor is a new underwater propulsion mode which combined with bionics and underwater propulsion technology. It was classified in to three different types referenced with swimming form, and current research status was presented. Then key technologies such as bionics mechanism, actuator, control system was analyzed. Finally, the future development was forecasted.