A power management circuit with 50%efficiency and large load capacity for tribo-electric nanogenerator

Recently, triboelectric nanogenerators （TENGs）, as a collection technology with characteristics of high reliability, high energy density and low cost, has attracted more and more attention. However, the energy coming from TENGs needs to be stored in a storage unit effectively due to its unstable ac output. The traditional energy storage circuit has an extremely low energy storage efficiency for TENGs because of their high internal impedance. This paper presents a new power management circuit used to optimize the energy using efficiency of TENGs, and realize large load capacity. The power management circuit mainly includes rectification storage circuit and DC-DC management circuit. A rotating TENG with maximal energy output of 106 mW at 170 rpm based on PCB is used for the experimental verification. Experimental results show that the power energy transforming to the storage capacitor reach up to 53 mW and the energy using efficiency is calculated as 50%. When different loading resistances range from 0.82 to 34.5 k^2 are connected to the storage capacitor in parallel, the power energy stored in the storage capacitor is all about 52.5 mW. Getting through the circuit, the power energy coming from the TENGs can be used to drive numerous conventional electronics, such as wearable watches.

Large deflections of non-prismatic nonlinearly elastic cantilever beams subjected to non-uniform continuous load and a concentrated load at the free end

This work studies large deflections of slen- der, non-prismatic cantilever beams subjected to a combined loading which consists of a non-uniformly distributed con- tinuous load and a concentrated load at the free end of the beam. The material of the cantilever is assumed to be non- linearly elastic. Different nonlinear relations between stress and strain in tensile and compressive domain are considered. The accuracy of numerical solutions is evaluated by com- paring them with results from previous studies and with a laboratory experiment.

Piezoelectric inertial robot for operating in small pipelines based on stick-slip mechanism:modeling and experiment

Small pipes exist in industrial and biomedical fields,and require microrobots with high operational precision and large load capacity to inspect or perform functional tasks.A piezoelectric inertial pipeline robot using a“stick-slip”mechanism was proposed to address this requirement.In this study,the driving principle of the proposed robot was analyzed,and the strategy of the design scheme was presented.A dynamics model of the stick-slip system was established by combining the dynamics model of the driving foot system and the LuGre friction model,and the simulation analysis of the effect of system parameters on the operating trajectory was performed.An experimental system was established to examine the output characteristics of the proposed robot.Experimental results show that the proposed pipeline robot with inertial stick-slip mechanism has a great load capacity of carrying 4.6 times(70 g)its own mass and high positioning accuracy.The speed of the pipeline robot can reach up to 3.5 mm/s(3 mm/s)in the forward(backward)direction,with a minimum step distance of 4µm.Its potential application for fine operation in the pipe is exhibited by a demonstration of contactless transport.

A 1500 mA,10 MHz on-time controlled buck converter with ripple compensation and efficiency optimization

A 1500 mA,10 MHz self-adaptive on-time （SOT） controlled buck DC-DC converter is presented. Both a low-cost ripple compensation scheme （RCS） and a self-adaptive on-time generator （SAOTG） are proposed to solve the system stability and frequency variation problem. Meanwhile a self-adaptive power transistor sizing （SAPTS） technique is used to optimize the efficiency especially with a heavy load. The circuit is implemented in a 2P4M 0.35μm CMOS process. A small external inductor of 0.47 μH and a capacitor of 4.7 μF are used to lower the cost of the converter and keep the output ripple to less than 10 mV. The measurement results show that the overshoot of the load transient response is 8 mV @ 200 mA step and the dynamic voltage scaling （DVS） performance is a rise of 16/zs/V and a fall of 20 μs/V. With a SAPTS technique and PFM control, the efficiency is maintained at more than 81% for a load range of 20 to 1500 mA and the peak efficiency reaches 88.43%.