Online condition monitoring of power transmission belts is essential to keep industrial belt-driven equipment functioning smoothly and reliably. This paper presents a smart electrostatic sensor that monitors belt motion through detection of static charge on the belt. A theoretical model is established using the method of moments for calculation of induced charge on strip-shaped electrodes placed in the vicinity of a belt moving both axially and transversely. The sensor unit converts the induced charge into proportional voltage signals using charge amplifiers and measures belt speed and vibration through cross correlation and spectral analysis, respectively. The performance of the smart electrostatic sensor is validated against a photoelectric rotary encoder and a laser displacement sensor. Comparative experimental results show that the belt speed can be measured with a relative error within ±2% over the range 1.7-15.5 m/s. The electrostatic sensor is capable of measuring the frequencies of transverse vibration accurately. Although absolute displacement cannot be measured due to the uncertain level of charge on the belt, the measurement results of relative vibration magnitudes for different modes and at different belt speeds are reasonably accurate.

The spatial sensitivity of an electrostatic sensor is recognized as an important factor that affects the accuracy of solids flow measurement in a pneumatic conveying pipe. However, the distribution of the spatial sensitivity is generally inhomogeneous due to the physical structure of the electrostatic sensor and the inherent electrostatic sensing mechanism. This paper proposes a sensitivity homogenization method based on differential measurement, i.e., using the differential outputs from two electrodes with different axial widths. The validity of the sensitivity homogenization method for a square-shaped electrostatic sensing head, which consists of strip-shaped electrode arrays with different widths, is validated through mathematical analysis. Furthermore, the response of the electrostatic sensing head incorporating the sensitivity homogenization method to roping flow regimes was evaluated on a gravity-fed solids flow test rig. Results from both modeling and experimental tests indicate that the homogeneity of the spatial sensitivity is improved significantly. The mean non-uniformity of the outputs from the sensing head is 11.7% as a result of the homogenization method.

We present a complete low-power Wi-Fi backscatter communication solution which based on a single microcontroller, and for the first time we demonstrate the battery-free Wi-Fi device prototype which is built using commercial-off-the-shelf components on a printed circuit board. It can operate on power that is harvested from ambient light, and its power consumption is 2-3 orders of magnitude lower than that of traditional active Wi-Fi chipset. The instantaneous communication current is only 900uA, the standby current is 1.25uA, and the communication distance is 50 feet. The solution we proposed not only has the advantages of system simplification, low cost, and no need for battery, but also enables the rapid development of Wi-Fi IoT products with existing commercial microcontrollers.

A novel stability analysis for the interval time-delay systems is proposed by employing a new series of integral inequalities for single and double integrals. Different from the recently introduced Wirtinger-based inequalities, refined Jensen inequalities and auxiliary function-based inequalities, the proposed ones can provide more accurate bounds for the cross terms in derivatives of the Lyapunov–Krasovskii functional (LKF) without involving additional slack variables. Based on the augmented LKF with triple-integral terms, their applications to stability analysis for interval time-delay systems are provided. By virtue of the newly derived inequalities, the resulting criteria are less conservative than some existing literature. Finally, numerical examples are provided to verify the effectiveness and improvement of the proposed approaches.

Long-Range (LoRa) scatter communication has wide coverage, long communication distance, low power consumption, low cost, and a wide application prospect in the field of Internet of things. The key to realizing LoRa scattering communication is to generate a square or sine wave with continuously changing frequency with time as the baseband signal. The existing technical solution is to control the voltage-controlled oscillator (VCO) using an analog-to-digital converter to generate a sine wave with continuously varying frequency. On the one hand, the aforementioned solution is sensitive to environmental changes, such as temperature. On the other hand, the power consumption is relatively large, and meeting the power requirements of passive communication is difficult. Based on the idea of direct digital frequency synthesis, this study proposes a method for generating square wave signals with continuous frequency variation with time using a microcontroller with high frequency stability and low system power consumption. Test results show that the device can realize LoRa scattering communication at any position between the base station and the receiving terminal, which are 210 meters apart, and is compatible with the existing commercial LoRa radio chipset. The standby current at the scattering end is 0.39 μA, and the continuous current during transmission is 140 μA, which reduces the power consumption of the existing active LoRa by three orders of magnitude.