Wireless sensor node powered by aircraft specific thermoelectric energy harvesting

An energy autonomous wireless sensor system consisting of an energy harvesting power source, an energy management unit and a low power wireless sensor node is tested for aircraft applications. The autonomous power source combines aircraft specific outside temperature changes with a thermoelectric generator (TEG) and a heat storage unit. The temperature difference generated with the latter component artificially at the TEG is used to power the sensor node by thermoelectricity. Additionally, a high efficient low input voltage power management circuit is necessary to store the generated energy and to convert it to higher voltage levels needed to operate the sensor. The experimental data are compared with results from numerical simulation models to predict the energy conversion in the heat storage - TEG system. A new TEG prototype is tested and the energy output is improved by 14%. The power management storage capacitors are adapted to the available energy, thereby increasing storage voltage and conversion efficiency. Doing so, the efficiency of the complete system can be increased by around 50%.     

A bioinspired touching sensor for amphibious mobile robots

An amphibious mobile robot relies on effective sensing ability to adapt itself in complicated amphibious environments. In this paper, we present a multifunctional whisker-like touching sensor with low energy consumption, inspired by amphibious animals. The sensor comprises a leverage system and a two-dimensional position tracing system, transforming the moving position of biowhisker to a changing laser spot coordinates. On land, the sensor driven by a motor is able to track the movement of biowhisker directly, telling the change of contact position, to sense nearby objects and explore their surface by touching. In underwater environment, the sensor can obtain in real-time external flow direction and velocity by passive impulsion. Testing results showed that our prototype can sense flow or drag force direction in 360° exactly, and tell flow velocity under 1 m/s, it can also recognize line or arc edges of obstacle correctly by touching.     

Component design and testing for a miniaturised autonomous sensor based on a nanowire materials platform

We present the design considerations of an autonomous wireless sensor and discuss the fabrication and testing of the various components including the energy harvester, the active sensing devices and the power management and sensor interface circuits. A common materials platform, namely, nanowires, enables us to fabricate state-of-the-art components at reduced volume and show chemical sensing within the available energy budget. We demonstrate a photovoltaic mini-module made of silicon nanowire solar cells, each of 0.5 mm² area, which delivers a power of 260 μW and an open circuit voltage of 2 V at one sun illumination. Using nanowire platforms two sensing applications are presented. Combining functionalised suspended Si nanowires with a novel microfluidic fluid delivery system, fully integrated microfluidic–sensor devices are examined as sensors for streptavidin and pH, whereas, using a microchip modified with Pd nanowires provides a power efficient and fast early hydrogen gas detection method. Finally, an ultra-low power, efficient solar energy harvesting and sensing microsystem augmented with a 6 mAh rechargeable battery allows for less than 20 μW power consumption and 425 h sensor operation even without energy harvesting.     

Principles of nonlinear MEMS-resonators regarding magnetic-field detection and the interaction with a capacitive read-out system

This paper presents a magnetic field sensor with capacitive read-out, whose active element is a micromachined mechanical resonator. The MEMS magnetic field sensor exploits the Lorentz force to detect external magnetic flux density through the displacement of the resonant structure, which can be measured with optical and capacitive sensing techniques. The micromachined U-shaped cantilever features a length of 2 mm, a base width of 90 μm and a thickness of 20 μm, and is manufactured in SOI technology. The designed sensor has a measured resonant frequency of 4.359 kHz for the fundamental mode and a calculated mass of the flexible structure of 24.5 ng. A quality factor in the order of 10⁴ at an ambient pressure of 0.3 Pa has been measured where a magnetic field resolution of 15 nT can be achieved. Although these arrangements are well suited to capacitively sense the vibrations caused by the Lorentz force on the current lead on the silicon part, care has to be taken to avoid undesired mutual interferences. A serious interference was observed in case of a DC bias voltage at the readout capacitance and a significant voltage drop caused by the current needed for the generation of the Lorentz force. This work investigates in detail this phenomenon as well as the complete physical transduction chain and improves the understanding of such microelectromechanical systems significantly. An analytical model of the electrostatic system is established including all relevant components and their interactions as well as the motion of the MEMS part. The importance of electrostatic back-action for a feasible detection limit for magnetic fields was recognized for the first time.     

Analysis of parasitic feed-through capacitance effect in closed-loop drive circuit design for capacitive micro-gyroscope

The drive axis of a capacitive micro-gyroscope sensor forms an ‘electrical-mechanical’ resonator with closed-loop drive circuits when the gyro is in full operation. The parasitic feed-through capacitance, which exists between the driving and sensing electrodes of the sensor, induces two main negative effects: preventing the expected ‘electrical-mechanical’ oscillation and introducing an undesired high frequency ‘electrical’ oscillation. In this paper, mathematical expression of the critical parasitic feed-through capacitance allowing the occurrence of ‘electrical-mechanical’ oscillation is derived for the first time. Based on the derived expression, a conclusion that increasing the polarization voltage on the sensor mass be the only electrical way to increase the critical value of parasitic feed-through capacitance is revealed. Then with an implemented silicon chip for the drive circuit, the reason of occurring electrical oscillation is analyzed, and an effective solution to avoid the electrical oscillation referred as increasing the polarization voltage is proposed. Experiments on a capacitive micro-gyroscope prototype show that when the polarization voltage is increased from 10 to 18 V, the closed-loop drive circuit eliminates possibility of the electrical oscillation effectively. As a result, the proposed electrical oscillation solution has been verified.     

A miniature pressure system with a capacitive sensor and a passivetelemetry link for use in implantable applications

A miniature telemetric pressure-measuring system is presented in this paper. The system uses passive telemetry to transfer power to the transponder and pressure data to the remote base unit. Such telemetric systems are becoming ever more important in the biomedical field as the interest for in-vivo measurements of different biological parameters both of humans and animals is increasing. A novel capacitive-type pressure sensor based on an SiGeB diaphragm is used as a sensing element. The merits of combining a capacitive pressure sensor and passive telemetry lies in the inherent low-power consumption of the sensor and the continuous availability of power through induction. The pressure sensor is connected to an integrated interface circuit, which includes a capacitance to frequency converter and an internal voltage regulator to suppress supply voltage fluctuations on the transponder side. In addition, the sensor and accompanying interface circuit take up very little space so as to be suitable for implantation     

Differential C<Superscript>4</Superscript>D sensor for conductive and non-conductive fluidic channel

This paper presents a novel design of a differential C⁴D (DC⁴D) sensor based on three electrodes for both conductive and non-conductive fluidic channel. This structure consists of two single C⁴D with an applied carrier sinusoidal signal to the center electrode as the excitation electrode. The electrodes are directly bonded on the PCB with built-in differential amplifier and signal processing circuit in order to reduce the parasitic component and common noise. In the non-conductive fluidic channel, the output voltage and capacitance changes 214.39 mV and 14 fF, respectively when a 3.83 μl tin particle crosses an oil channel. In conductive fluidic channel, the output voltage and admittance change up to 300 mV and 0.07 μS for the movement of a 4.88 μl plastic particle through channel. Moreover, the voltage change of this sensor is linear relation with the volume of investigated particle. This sensor also allows measuring velocity of particle inside fluidic channel and resistivity of the conductive fluidic.     

A phase-locked loop frequency tracking system for portable microelectromechanical piezoresistive cantilever mass sensors

A closed-loop circuit is developed in this work for tracking the resonant frequency of silicon microcantilever mass sensors. The proposed closed-loop system is mainly based on a phase-locked loop (PLL) circuit. To lock onto the resonant frequency of the resonator, an actuation signal generated from a voltage-controlled oscillator is fed back to the input reference signal of the cantilever sensor. In addition to the PLL circuit, an instrumentation amplifier and an active low-pass filter are connected to the system for gaining the cantilever output signal and transforming a rectangular PLL output signal into a sinusoidal signal used for sensor actuation, respectively. To demonstrate the functionality of the system, a self-sensing silicon cantilever resonator with a built-in piezoresistive Wheatstone bridge is fabricated and integrated with the circuit. A piezoactuator is employed to actuate the cantilever into resonance. From the measurement results, the integrated closed-loop system is successfully employed to characterize a 9.4 kHz cantilever sensor under ambient temperature cross-sensitivity yielding a sensor temperature coefficient of ?32.8 ppm/°C. In addition to it, the sensor was also exposed to exhaled human breath condensates and e-cigarette aerosols to test the sensor sensitivity obtained from mass-loading effects. With a high frequency stability (i.e., a frequency deviation as low as 0.02 Hz), this developed system is intended to support the miniaturization of the instrumentation modules for cantilever-based nanoparticle detectors (CANTORs).     

A novel high sensitive MEMS intraocular capacitive pressure sensor

This paper presents a novel high sensitive MEMS capacitive pressure sensor that can be used as a part of LC tank implant circuit for biomedical applications. The pressure sensor has been designed to measure pressures in the range of 0–60 mmHg that is in the range of intraocular pressure sensors. Intraocular pressure sensors are important in detection and treatment of an incurable disease called glaucoma. In this paper two methods are presented to improve the sensitivity of the capacitive pressure sensor. First low stress doped polysilicon material is used as a biocompatible material instead of p++silicon in previous work (Gu in Microfabrication of an intraocular pressure sensor, M.Sc Thesis, Michigan State University, Department of Electrical and Computer Engineering, 2005) and then some slots are added to the poly Si diaphragm. The novelty of this research relies on adding some slots on the sensor diaphragm to reduce the effect of residual stress and stiffness of diaphragm. The slotted diaphragm makes capacitive pressure sensor more sensitive that is more suitable for measuring intraocular pressure. The results yield a sensor sensitivity of 1.811 × 10^?5 for p++silicon clamped, 2.464 × 10^?5 1/Pa for polysilicon clamped and 1.13 × 10^?4 1/Pa for polysilicon slotted diaphragm. It can be seen that the sensitivity of the sensor with slotted poly Si diaphragm increased 6.2 times compared with previous work (clamped p++silicon diaphragm).     

压阻式高温压力传感器温度补偿与信号调理设计与测试

设计制作了一种集成信号调理电路的高温压阻式压力传感器,包含倒装式的压敏敏片、无源电阻温度补偿电路和信号调理电路组成;压敏芯片的制作采用SOI材料和MEMS标准工艺,温度补偿和信号调理电路采用高温电子元件;试验表明,无源电阻温度补偿具有显著的效果;此外,采用了高温信号调理电路来提高传感器的输出灵敏度,通过温度补偿来降低输出灵敏度;与传统的经验算法相比,所提出的无源电阻温度补偿技术具有更小的温度漂移,在220℃条件下传感器输出灵敏度为4.93 mV/100 kPa,传感器灵敏度为总体测量精度为±2%FS;此外,由于柔性传感器的输出电压可调,因此不需要使用一般的电压转换器随动压力变送器,这大大降低了测试系统的成本,有望在恶劣环境下的压力测量中得到高度应用。     

无线传感器网络中一种改进的能效数据收集协议

基于连通支配集的虚拟骨干是减少支配节点数量和限制路由搜索空间的关键技术,对于优化无线传感器网络生命起到重要作用。ViTAMin协议不但能通过关闭一些非必要节点产生虚拟骨干,而且能将采集的数据沿着距离基站能耗最低的路径进行发送,以节省能量。针对ViTAMin可能会产生非连通网络且支配节点能耗不均衡的问题,提出了一种基于虚拟骨干的能效数据收集协议EEVB。理论分析证明,EEVB能够以O(n)的时间与信息复杂度构造连通支配集,仿真实验进一步证实EEVB能够以较小的能耗开销构建规模较小的连通支配集,并有效延长网络的生命时间。     

A CMOS integrated interface circuit for metal-oxide gas sensors

This paper presents an integrated gas-sensor interface circuit that includes a high-efficiency temperature control loop, with a switching power stage and a digital set-point, as well as a wide-dynamic range read-out circuit. The temperature control loop adjusts the temperature of the sensor over a range of 250 °C with an accuracy better than 1.5 °C and with a maximum peak-to-peak ripple of 1.0 °C. The read-out circuit achieves, without calibration, a precision in sensor resistance measurement of 2.65%, over a range of 5.3 decades, leading to an equivalent dynamic range of 138 dB. The overall system is flexible and can be interfaced to sensors with different fabrication parameters. The interface circuit chip, realized with a 0.35 m CMOS technology, includes on the same 10-mm² die the high-accuracy read-out circuit and the switching power stage. In spite of the interferences produced by the power stage, the read-out circuit maintains always a dynamic range performance above 130 dB. The proposed interface circuit, together with a micromachined metal-oxide gas sensor, can detect 3 ppm of CO in air.     

路桥隧道承压报警传感节点的设计与实现

传统方法存在报警效率较低,能量消耗大等问题,提出了路桥隧道承压报警传感节点的设计。根据传感节点整体架构图,设计传感节点硬件,并对承压报警传感、无线单片机和传感单元及接口电路模块展开分析;利用嵌入式底层驱动进行信息交互,构建通信协议,通过无线传感方式采集数据,并对传感节点部署。通过实验验证结果可知,该设计方法充分考虑数据获取情况,具有报警效率高、能量消耗小的优势,可实现路桥隧道安全运营。     

Closed loop driving and detect circuit of piezoelectric solid-state micro gyroscope

Piezoelectric solid-state micro gyroscope is a novel kind of rotating rate sensor, which is based on the special thickness-shear vibrating mode of a piezoelectric body. Compared with the general vibratory micro gyroscope, it has no evident mass-spring component in its structure, so it has larger stiffness and robust resistance to shake and strike. Therefore, piezoelectric solid-state micro gyroscope can be used in the high-g environment. In this paper, piezoelectric solid-state micro gyroscope working principle is described. The closed loop driving and detect circuit of piezoelectric solid-state micro gyroscope is proposed in order to track the resonance frequency drift, stabilize the driving voltage value and detect the gyroscope output. The closed loop driving circuit (CLDC) mainly contains phase lock loop circuit, automatic gain circuit. Detect circuit mainly contains de-modulator, difference amplifier, Phase shift circuit and low pass filter. Experimental results show that the frequency of CLDC fluctuates within ±15 Hz with the resonance frequency of 357.9 kHz when get its stable status and the fluctuation of reference voltage is within ±7 mv, while the fluctuation of reference voltage in open loop driving circuit is ±23 mv. In the experiment, the sensitivity of the gyroscope with 740 mv/rad/s is observed. The work in the paper provides the theoretical and experimental foundation for realizing for this kind of gyroscope.     

An electromagnetic, vibration-powered generator for intelligent sensor systems

This paper describes the design of miniature generators capable of converting ambient vibration energy into electrical energy for use in powering intelligent sensor systems. Such a device acts as the power supply of a microsystem which can be used in inaccessible areas where wires can not be practically attached to provide power or transmit sensor data. Two prototypes of miniature generator are described and experimental results presented. Prototype A is based around two magnets coupled to a coil attached to a cantilever; prototype B is based around four magnets.

For prototype A, experimental results are given for its resonant frequency and its open circuit and loaded output as a function of vibration amplitude. For prototype B, experimental results are given for the generator’s Q factor in air and vacuum, its output voltage as a function of vibration amplitude as well as its magnetic field strength. This generator has been tested on a car engine and shown to produce a peak power of 3.9 mW with an average power of 157 μW.     

Distributed duty cycle control for delay improvement in wireless sensor networks

Dynamically adjusting the time duration of a node to stay active in one data collection period, i.e., duty cycle, is an efficient strategy to save energy and prolong the lifetime of network. In this paper, we propose a novel Adaptation Duty Cycle Control (ADCC) scheme based on feedback signals for wireless sensor networks (WSNs) which can reduce to-sink data transmission delay while lifetime is also improved. In ADCC, every node adaptively adjusts its duty cycle by comparing its own energy consumption with the largest energy consumption of the entire packet delivery flow, which is stored in a feedback ACK packet generated by sink node. Since in WSNs, a huge number of sensor nodes in the area far from the sink node have much remaining energy when network dies, even up to 90 %, these nodes have much larger duty cycles in ADCC compared with previous schemes, therefore the data transmission delay can be reduced to a great extent. Additionally, ADCC provides a largest-energy notification mechanism in order to determine the appropriate duty cycle of nodes in each data collection flow according to the application-dependent requirements. Comparing with the Wake on Idle, Dual-QCon and the Same Duty Cycle (SDC) schemes, ADCC can reduce the delay by more than 59.5 % under the same network lifetime, or increase the lifetime by 32.8 %–63.4 % under the same delay requirements, while also increase energy efficiency as much as 43.1 %.     

无线传感器网络节点太阳能供电系统设计

ZigBee无线传感器网络节点太阳能供电系统由太阳能电池板、充电控制电路和锂电池组成,采集光能并将其转换为电能存储在锂电池中。通过锂电池充电管理芯片CN3063组成充电控制电路对锂电池进行充电管理。利用超低功耗锂电池电压检测芯片CN301组成放电保护电路,最大限度地延长锂电池的寿命。由于电源能量来自太阳能,因此非常适合野外布置的ZigBee无线传感器网络数据采集节点使用。     

CMOS integrated elliptic diaphragm capacitive pressure sensor in SiGe MEMS

A novel CMOS integrated Micro-Electro-Mechanical capacitive pressure sensor in SiGe MEMS (Silicon Germanium Micro-Electro-Mechanical System) process is designed and analyzed. Excellent mechanical stress–strain behavior of Polycrystalline Silicon Germanium (Poly-SiGe) is utilized effectively in this MEMS design to characterize the structure of the pressure sensor diaphragm element. The edge clamped elliptic structured diaphragm uses semi-major axis clamp springs to yield high sensitivity, wide dynamic range and good linearity. Integrated on-chip signal conditioning circuit in 0.18 μm TSMC CMOS process (forming the host substrate base for the SiGe MEMS) is also implemented to achieve a high overall gain of 102 dB for the MEMS sensor. A high sensitivity of 0.17 mV/hPa (@1.4 V supply), with a non linearity of around 1 % is achieved for the full scale range of applied pressure load. The diaphragm with a wide dynamic range of 100–1,000 hPa stacked on top of the CMOS circuitry, effectively reduces the combined sensor and conditioning implementation area of the intelligent sensor chip.     

A Genetic Algorithm-Based,Dynamic Clustering Method Towards Improved WSN Longevity

The dynamic nature of wireless sensor networks (WSNs) and numerous possible cluster configurations make searching for an optimal network structure on-the-fly an open challenge. To address this problem, we propose a genetic algorithm-based, self-organizing network clustering (GASONeC) method that provides a framework to dynamically optimize wireless sensor node clusters. In GASONeC, the residual energy, the expected energy expenditure, the distance to the base station, and the number of nodes in the vicinity are employed in search for an optimal, dynamic network structure. Balancing these factors is the key of organizing nodes into appropriate clusters and designating a surrogate node as cluster head. Compared to the state-of-the-art methods, GASONeC greatly extends the network life and the improvement up to 43.44 %. The node density greatly affects the network longevity. Due to the increased distance between nodes, the network life is usually shortened. In addition, when the base station is placed far from the sensor field, it is preferred that more clusters are formed to conserve energy. The overall average time of GASONeC is 0.58 s with a standard deviation of 0.05.     

压电传感器与前置放大器的配接

从提高传感器和测量电路的灵敏度出发,根据压电传感器压电元件串联和并联2种连接方式,电压放大器和电荷放大器2种前置电路的特点,对压电传感器与前置电路如何配接进行研究。提出了压电元件串联应配接电压放大器,压电元件并联应配接电荷放大器。当压电传感器与测量电路之间的距离较远时,宜采用后一种方式。此方法具有实际的指导意义。