Vibration energy harvesting is a promising solution for powering battery-free IoT systems; however, the instability of ambient vibrations presents significant challenges, such as limited harvested energy, intermittent power supply, and poor adaptability to various applications. To address these challenges, this paper proposes ViPSN2.0, a modular and reconfigurable IoT platform that supports multiple vibration energy harvesters (piezoelectric, electromagnetic, and triboelectric) and accommodates sensing tasks with varying application requirements through standardized hot-swappable interfaces. ViPSN 2.0 incorporates an energyindication power management framework tailored to various application demands, including light-duty discrete sampling, heavyduty high-power sensing, and complex-duty streaming tasks, thereby effectively managing fluctuating energy availability. The platform’s versatility and robustness are validated through three representative applications: ViPSN-Beacon, using an ultra-lowcost structural PZT (ϕ35 mm, <0.002 $) to enable a BLE advertisement from a single transient fingertip press with 100 m line of sight; ViPSN-LoRa, supporting wireless communication powered by wave vibrations in actual marine environments (Bohai Bay) with per-uplink task energy compatible with kilometer-scale field links; and ViPSN-Cam, enabling intermittent image capture and wireless transfer, delivering one frame approximately every 15 s under typical conditions. Experimental results demonstrate that ViPSN 2.0 can reliably meet a wide range of requirements in practical battery-free IoT deployments under energy-constrained conditions.

Extracting geometric features from 3D point clouds is widely applied in many tasks, including registration and recognition. We propose a simple yet effective method, termed height-azimuth image based transformation-invariant net (HA-TiNet), to learn a distinctive, general and rotation-invariant 3D local descriptor. HA-TiNet is composed of a height-azimuth image generator and a feature extraction net. Based on a local reference axis (LRA), the height-azimuth image generator first partitions local region along the plane-radial direction, and then implements a statistic of height and azimuth information in each divided space to generate a set of height-azimuth images. The generated height-azimuth images are invariant in the rotation around x- and y-axes and have high accuracy due to the high repeatability of an LRA. Besides, they can be easily embedded in 2D convolutional neural networks (CNNs). Our feature extraction net learns the information on the height-azimuth images using a ResNet-based backbone and a rotation-invariant layer. The ResNet-based backbone is lightweight while very effective. The rotation-invariant layer removes the rotation-variance around z-axis, making our descriptor have full rotation-invariance. Extensive experiments on indoor and outdoor datasets show that our method presents superior overall performance, and exhibits strong descriptiveness and generalization ability compared to the state-of-the-art descriptors.

The literature on piezoelectric energy harvesting (PEH) systems underscores the role of circuit advancements in enhancing energy harvesting capability in resonance. Recent studies using phase-variable (PV) synchronized switch technologies have also shown potential in broadband PEH, thereby improving off-resonance energy harvesting. However, the electrically induced dynamics by existing interface circuits lack a comprehensive definition and demonstration, hampering the performance comparisons across different circuits. Regarding these gaps, this paper presents an impedance-based analysis and comparison of electromechanical joint dynamics in PEH systems employing various interface circuits. The focus is on their contributions to enhancing harvesting bandwidth. By introducing resonance tunability into the conventional ideal PEH model, this paper proposes a more generic impedance model. It reveals that the achievable dynamic ranges of practical interface circuits are subsets of the ideal arbitrarily tunable scenario. A detailed quantitative study on the attainable ranges of the PV synchronized switch circuit solutions is provided after the introduction of the ideal target. Simulation and experimental data from different interface circuits align well with theoretical findings. The paper concludes that resonance tunability hinges on the extent of the achievable reactive (imaginary) part of the equivalent impedance. Electromechanical coupling conditions and dielectric loss may further impact resonance tunability. The general ideal model and quantitative impedance analysis provided in this paper help guide the future design effort toward high-capability and broadband PEH systems.

The emerging energy harvesting technology facilitates the development of ubiquitous and everlasting battery-free motion detectors. This article introduces a robust design of the transient-motion-powered motion detector, which is called ViPSN-pluck. “ViPSN” is the acronym for the vibration-powered sensing node while “pluck” stands for the plucking-motion energy harvester. By using a piezo-magneto-elastic structure, ViPSN-pluck can efficiently harvest energy from a transient motion. By properly making good use of this tiny harvested energy, ViPSN-pluck can effectively carry out motion detection and Bluetooth low-energy (BLE) wireless communication. Given the concurrency of mechanical potential energy precharging and motion detection, the transient-motion plucking energy harvester used in ViPSN-pluck has the merit of high energy reliability. This unique feature is unprecedented in the solar and radio-frequency (RF) energy harvesting cases, which might suffer from energy outages under fluctuating irradiance or RF signal strength, respectively. The working principle of ViPSN-pluck, in particular, the dynamic characteristics of the plucking energy harvester and the energy matching between generation and utilization, are discussed in detail to demonstrate the robustness in operation. The cyber-electromechanical synergy among the mechanical dynamics, power conditioning circuit, and low-power embedded system is highlighted. The design methodology of ViPSN-pluck provides a valuable reference for the developments of future motion-powered Internet of Things devices.

This paper introduces a new phase-variable switch control for the parallel synchronized triple bias-flip (P-S3BF) interface circuit, towards the broadband and high-capability piezoelectric energy harvesting (PEH) systems. By using the phase-variable P-S3BF (PV-P-S3BF), both the electrically induced damping and electrically induced mass/stiffness can be tuned to a certain extent in operation, such that to simultaneously make the dual tasks of broadband and high-capability in PEH. The joint dynamics and harvested power of the PEH systems using the PV-P-S3BF circuits are thoroughly discussed based on the harmonic analysis and impedance modeling. The available range of PV-P-S3BF is rationally shown in the complex impedance plane. The experimental results obtained with a PCB-level prototyped circuit show agreement with the analytical results. The new PV-P-S3BF circuit opens a promising future towards the electrically in-situ tunable broadband and high-capability PEH systems.

This paper addresses the issue of placing a simple polygon (upon translation and rotation) on an isometric triangular grid such that the polygon contains the maximum number of triangles in its closure. This solves the problem left open in two recent papers titled “On the problem of the automated design of large-scale robot skin” and “An improved algorithm for the automated design of large scale robot skin” published in the IEEE Transactions on Automation Science and Engineering . Based on the properties of the grid, an improved algorithm is also presented. We also present some experimental results describing the use of this algorithm.