Yu Tan

Systematic Development of a Wireless Sensor Network for Piezo-Based Sensing

A low-power wireless sensor/actuator network was specially developed and optimized for piezoceramic transducer-based active sensing applications. Wireless sensor network promises increased system flexibility, lower system cost, and increased robustness through decentralization. Piezoceramic signal conditioning circuit, actuating circuit, power management, and wireless microcontroller were integrated in the hardware design. IEEE 802.15.4 wireless stack protocol was implemented on the hardware, and user input/output management together with a shell provided easier debugging and configuring interface. The designed system provides a low-power wireless solution towards many applications such as wireless structural health monitoring and wireless structural vibration control.

The computational fluid dynamic modeling of downwash flow field for a six-rotor UAV

The downwash flow field of the multi-rotor unmanned aerial vehicle (UAV), formed by propellers during operation, has a significant influence on the deposition, drift and distribution of droplets as well as the spray width of the UAV for plant protection. To study the general characteristics of the distribution of the downwash airflow and simulate the static wind field of multi-rotor UAVs in hovering state, a 3D full-size physical model of JF01-10 six-rotor plant protection UAV was constructed using SolidWorks. The entire flow field surrounding the UAV and the rotation flow fields around the six rotors were established in UG software. The physical model and flow fields were meshed using unstructured tetrahedral elements in ANSYS software. Finally, the downwash flow field of UAV was simulated. With an increased hovering height, the ground effect was reduced and the minimum current velocity increased initially and then decreased. In addition, the spatial proportion of the turbulence occupied decreased. Furthermore, the appropriate operational hovering height for the JF01-10 is considered to be 3 m. These results can be applied to six-rotor plant protection UAVs employed in pesticide spraying and spray width detection.

Fractional calculus guidance algorithm for aircraft pursuit-evasion

Aiming at intercepting hypersonic target in a pursuit-evasion game, this paper presents a fractional calculus guidance algorithm based on a Nonlinear Proportional and Differential Guidance law (NPDG). According to relative motions between the interceptor and target, quantitative values were proposed for the parameters of the fractional calculus guidance law and system stability condition was given. Numerical experiment results demonstrated that the proposed guidance algorithm effectively reduced the miss distance against target maneuver. A stronger robustness compared to the NPDG was also shown under noisy condition.

Feedback Control for Structural Health Monitoring in a Smart Aggregate Based Sensor Network

The concept of smart aggregates, a distributed intelligent multi-purpose sensor network for civil structures, has been implemented to address three important issues including early-age concrete strength monitoring, impact detection and evaluation, and structural health monitoring. This paper presents mainly the employment of smart aggregates’ active sensing property to form feedback in a sensor network to reduce damage-location detection time for lower power cost. Firstly, the concept of smart aggregates and the principle of a smart-aggregate-based sensor network are outlined. Next, the data pretreatment methods, including the sensor observation estimation model and the wavelet-packet-based signal processing algorithm, are proposed. A crucial concept using the damage index is also introduced. Moreover, the concept of the geometry structure matching method with the knowledge of an expert system is presented to determine which sensor is the optimal actuator. Finally, the data pretreatment algorithm and the geometry structure matching method are evaluated for a two-story concrete frame instrumented with smart aggregates as a testing object by means of actual experiments. The testing results demonstrate that the proposed algorithms are feasible and perform well in selecting optimal actuators of the sensor network for detecting damage locations.