HIL(Hardware in the loop) simulation of UAV(Unmanned Aerial Vehicle) plays an important role in flight control sysrtem development and algorithm verification. Taking the open source flight control system Pixhawk as the research object, this paper establishes a HIL system based on NI(National Instrument) hardware platform. The dynamic model and kinematic model are modeled through Simulink, the online management of simulation model is realized through Veristand, and the online display of model parameters and fault injection are realized through Labview. The simulation system can test the functional performance, reliability and safety of flight control system. The simulation results show that the simulation platform works reliably and has good real-time performance. It can effectively and reliably carry out the HIL of flight control system for UAV.
According to the characteristics of unmanned aircraft systems (UASs) with multi-rotors, this paper realizes the reliability evaluation. Referring to the relevant standards and specifications for reliability evaluation of electronic products and communication products, the methods of sampling, test plan, test conditions and index evaluation related to reliability evaluation of Referring to are proposed. Based on the exponential distribution, the reliability index and its calculation method are put forward, and the evaluation method for non-failure data is also studied. The method is applied and the reliability level of UASs with multi-rotors is obtained. This method meets the actual market demand and provides a practical method for UASs reliability evaluation.
In order to solve the problem of low attitude estimation accuracy of low-cost UAV without GNSS (Global Navigation Satellite System) signal, the integrated navigation algorithm was improved. Binocular vision sensor is introduced as the observation sensor, and the position and attitude angle of the image information collected by binocular camera were estimated by the SLAM theory, the position and attitude angle were entered into the EKF algorithm, and the Vision Inertial EKF (VI-EKF) algorithm is established. It realizes the high-precision navigation of low-cost UAV without GNSS signal. The biases of gyroscope and accelerometer are calculated by the relative motion increment between the two key frames of binocular camera and IMU pre-integration data, and these two biases were taken as observations to update IMU bias in the process of EKF algorithm. In this paper, the effectiveness of IMU pre-integration algorithm is verified firstly, and then the VI-EKF navigation algorithm is compared with the pure visual SLAM algorithm through dataset simulation. The simulation results show that the VI-EKF algorithm proposed in this paper has a good performance in the environment without GNSS signal.
We propose a fiber-Bragg-grating (FBG)-based optical code-division multiple access passive optical network (OCDMA-PON) using a dual-baseband modulation scheme. A mathematical model is developed to study the performance of this scheme. According to the analyzed results, this scheme can allow a tolerance of the spectral power distortion (SPD) ratio of 25% with a bit error rate (BER) of 10-9 when the modified pseudorandom noise (PN) code length is 16. Moreover, we set up a simulated system to evaluate the baseband and radio frequency (RF) band transmission characteristics. The simulation results demonstrate that our proposed OCDMA-PON can provide a cost-effective and scalable fiber-to-the-home solution.
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