A novel pump-valve coordinated controlled hydraulic system for the lower extremity exoskeleton

2020 ◽  
Vol 42 (15) ◽  
pp. 2872-2884
Author(s):  
Jinlin Jiang ◽  
Yu Wang ◽  
Heng Cao ◽  
Jun Zhu ◽  
Xinbin Zhang
Keyword(s):  
Lower Extremity ◽  
Hydraulic System ◽  
Hydraulic Cylinder ◽  
Energy Conversion Efficiency ◽  
High Energy ◽  
Functional Requirements ◽  
Hydraulic Cylinders ◽  
Pump Valve ◽  
High Energy Conversion Efficiency ◽  
The Moment

In order to reduce the weight and improve the energy efficiency of the lower extremity exoskeleton, a novel pump-valve coordinated controlled (PVCC) hydraulic system is presented. This hydraulic system only uses one electro-hydrostatic unit (EHU) and two valves to drive two hydraulic cylinders at the hip and knee of the lower extremity exoskeleton. The PVCC hydraulic system has the advantage of high energy conversion efficiency of the electro-hydrostatic actuator (EHA), which consists of one EHU and one hydraulic cylinder. To meet the requirements of the moment and speed of each joint of the exoskeleton, the proportional valve and on-off valve are added to adjust the flow into two hydraulic cylinders. The performance of EHU is tested by some hydraulic experiments, and the performance of the PVCC hydraulic system is analyzed by AMESim. The results show that the novel hydraulic system can only use one EHU to drive two hydraulic cylinders simultaneously under the premise of meeting the functional requirements of the exoskeleton.

Current progress and performance improvement of Pt/C catalysts for fuel cells

2020 ◽  
Vol 8 (46) ◽  
pp. 24284-24306
Author(s):  
Xuefeng Ren ◽  
Yiran Wang ◽  
Anmin Liu ◽  
Zhihong Zhang ◽  
Qianyuan Lv ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Energy Conversion ◽  
Performance Improvement ◽  
Electric Energy ◽  
Energy Conversion Efficiency ◽  
High Energy ◽  
Carnot Cycle ◽  
High Energy Conversion Efficiency ◽  
And Performance

Fuel cell is an electrochemical device, which can directly convert the chemical energy of fuel into electric energy, without heat process, not limited by Carnot cycle, high energy conversion efficiency, no noise and pollution.

The Lower Extremity Exoskeleton Coordinated Control Method Based on Human Electromechanical Coupling

2012 ◽  
Vol 220-223 ◽  
pp. 1012-1017
Author(s):  
Qing Guo ◽  
Dan Jiang
Keyword(s):  
Lower Extremity ◽  
Electromechanical Coupling ◽  
Position Control ◽  
Control Method ◽  
Angular Displacement ◽  
Stability Margin ◽  
Hydraulic Cylinder ◽  
Load Force ◽  
Hydraulic Cylinders ◽  
Coupling Characteristics

This paper has introduced electromechanical coupling characteristics in the lower extremity exoskeleton systems, considered model ,according to legs supporting gait when people walking, established the load torque compensation model , and a mathematical model of knee position control system which is made of the servo valve, hydraulic cylinders and other hydraulic components, designed hydraulic cylinder position control loop in case of existing load force interference compensation, and used the method of combining the PID and lead correction network for frequency domain design ,ensured system to meet a certain stability margin. The simulation results show that this position control method can servo on the knee angular displacement of normal human walking, reached a certain exoskeleton boost effect, at the same time, met the needs of human-machine coordinated motion.

Direct-Write Piezoelectric Polymeric Nanogenerator with High Energy Conversion Efficiency

Nano Letters ◽  
2010 ◽  
Vol 10 (2) ◽  
pp. 726-731 ◽  
Author(s):  
Chieh Chang ◽  
Van H. Tran ◽  
Junbo Wang ◽  
Yiin-Kuen Fuh ◽  
Liwei Lin
Keyword(s):  
Energy Conversion ◽  
Conversion Efficiency ◽  
Energy Conversion Efficiency ◽  
High Energy ◽  
Direct Write ◽  
High Energy Conversion Efficiency

A Grid Connected Flyback Inverter with a DC Active Filter for Photovoltaic Cells

2015 ◽  
Vol 781 ◽  
pp. 406-409
Author(s):  
Dome Sulong ◽  
Chuttchaval Jeraputra
Keyword(s):  
Current Mode ◽  
Energy Conversion Efficiency ◽  
High Energy ◽  
Active Filter ◽  
Full Wave ◽  
Pv Module ◽  
High Energy Conversion Efficiency ◽  
Sinusoidal Current ◽  
Dc Current ◽  
And Control

This paper presents the design and control of a grid-connected flyback inverter with a DC active filter for photovoltaic (PV) cells. The proposed topology consists of a flyback DC-AC inverter and a DC active filter that can operate independently. The flyback inverter, controlled in digital peak current mode, regulates the full-wave rectified sinusoidal current later, which is alternately inverted and injected into the grid. The DC active filter regulates the smooth current/power drawn from a PV module by using cascaded proportional-integral (PI) controllers. Analysis, design and control of the proposed topology are presented. A 100W/220V/50Hz prototype is developed and tested. The experimental results show that the proposed flyback inverter with a DC active filter is capable of regulating a sinusoidal current fed into the grid, actively filtering the DC current/power and achieving reasonably high energy conversion efficiency.

Flexoelectric Energy Harvesting Using Circular Thin Membranes

2020 ◽  
Vol 87 (9) ◽  
Author(s):  
Zhaoqi Li ◽  
Qian Deng ◽  
Shengping Shen
Keyword(s):  
Energy Harvesting ◽  
Energy Harvester ◽  
Energy Conversion Efficiency ◽  
High Energy ◽  
Circular Membrane ◽  
Governing Equations ◽  
Energy Harvesters ◽  
Thin Membranes ◽  
High Energy Conversion Efficiency ◽  
Working Frequency

Abstract In this work, we propose a circular membrane-based flexoelectric energy harvester. Different from previously reported nanobeams based flexoelectric energy harvesters, for the flexoelectric membrane, the polarization direction around its center is opposite in sign to that far away from the center. To avoid the cancelation of the electric output, electrodes coated to upper and lower surfaces of the flexoelectric membrane are respectively divided into two parts according to the sign of bending curvatures. Based on Hamilton’s principle and Ohm’s law, we obtain governing equations for the circular membrane-based flexoelectric energy harvester. A generalized assumed-modes method is employed for solving the system, so that the performance of the flexoelectric energy harvester can be studied in detail. We analyze the effects of the thickness h, radius r0, and their ratio on the energy harvesting performance. Specifically, we show that, by selecting appropriate h and r0, it is possible to design an energy harvester with both high energy conversion efficiency and low working frequency. At last, through numerical simulations, we further study the optimization ratio for which the electrodes should be divided.

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