System Anti-interference Ability Research Articles

Simplified model for non-line-of-sight optical camera communication with a simple patterned reflective surface.

Most previous studies on non-line-of-sight optical camera communication (NLOS-OCC) were conducted as practical experiments; few relevant mathematical models have been proposed for simulation. This paper presents a simplified model for NLOS-OCC with a simple patterned reflective surface and proposes to directly decode the raw pixel values to improve the system performance. The model combines the mathematical models of a diffuse reflection channel and rolling shutter to obtain a normalized raw pixel value matrix of the pixel plane corresponding to the camera output image and realize visualization. Based on this model, we analyze the threshold selection and anti-interference ability of the conventional decoding scheme, and propose the sorting pre-decoding scheme: first sorting the pixel values by rows before decoding can effectively reduce the impact of the reflective surface pattern and enhance the system's anti-interference ability.

Research on Aircraft Attitude Control Method Based on Linear Active Disturbance Rejection

In this paper, a dual-loop active disturbance rejection attitude controller design method is proposed for the attitude control of aircraft. Firstly, based on the nonlinear dynamic model of aircraft, the control system model with inner loop as angular velocity and outer loop as attitude angle is established. Secondly, the extended state observer for the inner loop is established to estimate and compensate the state of the system in real time. The controller of the compensated series integral system is designed by using the linear PD control method. Thirdly, the extended state observer and controller for the outer loop are designed by the same method. Finally, the stability proof of the dual-loop attitude control method is given based on the Lyapunov theorem of stability. Simulation results show that compared with the traditional PID attitude control method, the dual-loop ADRC attitude control method has better control quality in tracking speed, tracking error, and system anti-interference ability. The control parameters to be adjusted in this method have distinct physical significance. So this method has a wide range of engineering application prospects.

Chinese remainder theorem‐based construction of optimal no‐hit‐zone frequency sequence set with wide gap

In frequency-hopping (FH) communication systems, frequency-hopping sequences (FHSs) determine systems' performance. For the quasi-synchronous FH communication systems, no-hit-zone (NHZ) frequency sequences are good at preventing multi-path interferences. If the two neighbouring frequency components of an FHS have enough gap, the FH communication system's anti-interference ability will be significantly improved. Here, a Chinese remainder theorem-based construction of optimal NHZ-FHS sets with wide gap is proposed.

Heat transfer mechanism and structure design of phase change materials to improve thermoelectric device performance

In recent years, the use of phase change materials (PCM) to improve the output performance of semiconductor thermoelectric generators (TEG) and maintain the long-term work of TEG has received widespread attention. Because of the lack of a unified understanding of the existing PCM-TEG combination mode and PCM structure design, this paper first established a PCM-TEG coupling mathematical model, the accuracy of which is proved by experimental data. Secondly, for the three most common combinations of PCM and TEG, namely cold-sided, hot-sided and dual-sided PCM-TEG, the effect of PCM on TEG, the effect of finned PCM on system performance, and the system anti-interference ability when the heat source is unstable are respectively studied from the heat transfer mechanism. The results show that 1) PCM's high heat storage characteristics can effectively protect TEG and avoid device failure due to excessive temperature; 2) Designs of metal fins within PCM can effectively maintain advantages of the PCM and significantly enhance the temperature difference between the hot and cold ends of TEG, thereby significantly improving the system performance; 3) The cold-sided PCM-TEG system has the best output but the worst anti-interference ability compared to the hot-sided or dual-sided design. On a comprehensive basis, the dual-sided design is recommended in practice; 4) The cooling capacity of the PCM-TEG system significantly affects the performance. Enhancing the heat transfer coefficient of the cold end of the TEG can significantly improve PCM-TEG systems' performance.

Fixed Power Allocation Algorithm Based on Time-Shift Pilot in Massive MIMO System

Massive Multiple-Input-Multiple-Output (MIMO) technology can greatly improve the spectrum utilization rate and system anti-interference ability as the key of technologies in modern wireless communication. However, pilot pollution has restricted the further development of large-scale MIMO technology. In this paper, a fixed allocation algorithm based on time-shift pilot to control pilot pollution in massive MIMO systems is proposed. Firstly, signal-to-interference-plus-noise-ratio (SINR) expression of the edge terminal based on time-shift pilot is derived, and then we calculate the proportional power allocation factor through the number of terminals. Finally, the uplink data power is reallocated by combining the proposed algorithm and time-shift pilot strategy. The simulation results show that the proposed algorithm can improve the communication ability of the edge terminal effectively.

An Improved Interference Suppression Algorithm Based on Regular WPT in the DSSS Satellite Communication System

Direct Sequence Spread Spectrum (DSSS), which is a typical spread spectrum technology with the characteristic of anti-jam, is widely used in satellite communication systems. Nevertheless, its processing gain is always limited because there are some restrictions on bandwidth and techniques in a practical system. When the interference is over threshold, it will lead to performance degradation Transform domain processing technology does improve the system's antiinterference ability. Fourier transform possesses a certain analyzing ability in the time and frequency domain, and wavelet packet transform has a better one. Both of their results of signal processing are not satisfied due to the limited capability of the interference detection and suppression. Through comparing and summarizing the traditional algorithm, a novel interference suppression algorithm which combines wavelet packet transform with Fourier transform is put forward in this paper. Simulation results reveal that the proposed interference suppression algorithm significantly improves the anti-jamming capability the DSSS satellite communication system

分布反馈量子级联激光器脉冲驱动电源的研制

In considering the exciting ability of driving Distributed-feedback quantum cascade laser in infrared carbon monoxide detection,a novel generator under experimental validation was carried out accordingly.Firstly,low ripple power supply and perfect protective module were developed,which improved the quality of drive pulse significantly and ensured the reliability of the power supply work.Secondly,corresponding function circuits were designed by the concept of"Multiple Isolation".So the system anti-interference ability was enhanced greatly.Lastly,deep voltage feedback method and proportional-integral-differential control theory were used to improve the stability of drive current efficiently.Utilizing illustrated driver,driving test was conducted on one Distributed-feedback quantum cascade laser with center wavelength at 4.76μm,which was fabricated by institute of semiconductor,CAS.Experimental results demonstrate during a long-term operation(200h),stability of drive current is 2.5×10-5,linearity of the drive power system is 0.04%,which meet the requirements of driving Distributed-feedback quantum cascade lasers and provide a strong guarantee for infrared carbon monoxide detection.

Design of LQR Controller for the Inverted Pendulum

For the instability of the inverted pendulum, a LQR controller is designed based on optimal control algorithm in this paper, which can control the pendulum angle and the cart position at the same time. The basic principle of LQR optimal control is analyzed and the LQR controller is designed and simulated in this paper. The simulation results show that the designed controller is effective. It has a good effect of equilibrium and stability control, and the system's anti-interference ability is improved.

Research on an Improved Method for Permanent Magnet Synchronous Motor

In permanent magnet synchronous motor (PMSM) traditional vector control system, PI regulator is used in the speed loop, but it has some defects. An improved method of PMSM vector control is proposed in the paper. The active-disturbance rejection control (ADRC) speed regulator is designed with the input signals of given speed and real speed and the output of given stator currentqcoordinate component. Then, in order to optimize ADRC controller, the least squares support vector machines (LSSVM) optimal regression model is derived and successfully embedded in the ADRC controller. ADRC observation precision and dynamic response of the system are improved. The load disturbance effect on the system is reduced to a large extent. The system anti-interference ability is further improved. Finally, the current sensor CSNE151-100 is selected to sample PMSM stator currents. The voltage sensor JLBV1 is used to sample the stator voltage. The rotor speed of PMSM is measured by mechanical speed sensor, the type of which is BENTLY 330500. Experimental platform is constructed to verify the effectiveness of the proposed method.