scholarly journals A dynamic electrically driven soft valve for control of soft hydraulic actuators

2021 ◽  
Vol 118 (34) ◽  
pp. e2103198118
Author(s):  
Siyi Xu ◽  
Yufeng Chen ◽  
Nak-seung P. Hyun ◽  
Kaitlyn P. Becker ◽  
Robert J. Wood
Keyword(s):  
Power Density ◽  
Flow Rate ◽  
Dielectric Elastomer ◽  
External Pressure ◽  
Operating Conditions ◽  
Effective Control ◽  
Hydraulic Actuators ◽  
Dielectric Elastomer Actuators ◽  
Multiple Actuators ◽  
Density Dynamic

Regulation systems for fluid-driven soft robots predominantly consist of inflexible and bulky components. These rigid structures considerably limit the adaptability and mobility of these robots. Soft valves in various forms for fluidic actuators have been developed, primarily fluidically or electrically driven. However, fluidic soft valves require external pressure sources that limit robot locomotion. State-of-the-art electrostatic valves are unable to modulate pressure beyond 3.5 kPa with a sufficient flow rate (>6 mL⋅min−1). In this work, we present an electrically powered soft valve for hydraulic actuators with mesoscale channels based on a different class of ultrahigh-power density dynamic dielectric elastomer actuators. The dynamic dielectric elastomer actuators (DEAs) are actuated at 500 Hz or above. These DEAs generate 300% higher blocked force compared with the dynamic DEAs in previous works and their loaded power density reaches 290 W⋅kg−1 at operating conditions. The soft valves are developed with compact (7 mm tall) and lightweight (0.35 g) dynamic DEAs, and they allow effective control of up to 51 kPa of pressure and a 40 mL⋅min−1 flow rate with a response time less than 0.1 s. The valves can also tune flow rates based on their driving voltages. Using the DEA soft valves, we demonstrate control of hydraulic actuators of different volumes and achieve independent control of multiple actuators powered by a single pressure source. This compact and lightweight DEA valve is capable of unprecedented electrical control of hydraulic actuators, showing the potential for future onboard motion control of soft fluid-driven robots.

A Nonlinear Model for Dielectric Elastomer Membranes

2005 ◽  
Vol 72 (6) ◽  
pp. 899-906 ◽  
Author(s):  
Nakhiah Goulbourne ◽  
Eric Mockensturm ◽  
Mary Frecker
Keyword(s):  
Large Deformations ◽  
Mathematical Formulation ◽  
Dielectric Elastomer ◽  
External Pressure ◽  
Membrane Area ◽  
System Parameters ◽  
Geometrical Nonlinearities ◽  
Dielectric Elastomer Actuators ◽  
Materials Used ◽  
Dielectric Elastomer Membrane

The material and geometrical nonlinearities of novel dielectric elastomer actuators make them more difficult to model than linear materials used in traditional actuators. To accurately model dielectric elastomers, a comprehensive mathematical formulation that incorporates large deformations, material nonlinearity, and electrical effects is derived using Maxwell-Faraday electrostatics and nonlinear elasticity. The analytical model is used to numerically solve for the resultant behavior of an inflatable dielectric elastomer membrane, subject to changes in various system parameters such as prestrain, external pressure, applied voltage, and the percentage electroded membrane area. The model can be used to predict acceptable ranges of motion for prescribed system specifications. The predicted trends are qualitatively supported by experimental work on fluid pumps [A. Tews, K. Pope, and A. Snyder, Proceedings SPIE, 2003)]. For a potential cardiac pump application, it is envisioned that the active dielectric elastomer membrane will function as the motive element of the device.

Physical Parameters Affecting on the Electrode Performance for Proton Exchange Membrane Fuel Cells (PEMFCs)

2015 ◽  
Vol 1105 ◽  
pp. 320-324
Author(s):  
Chebbi Rachid ◽  
Wan Ramli Wan Daud ◽  
Beicha Abdellah ◽  
Mohd Ambar Yarmo
Keyword(s):  
Power Density ◽  
Flow Rate ◽  
Current Density ◽  
Pressure Ratio ◽  
Air Flow ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Physical Parameters ◽  
Electrode Performance ◽  
Hydrogen Flow

Physical parameters effects are considered as sticking point to increase and decrease the electrode performance for PEMFCs, which is related to the electrode structural degradation under diverse operating conditions, such as various air and hydrogen pressures, humidifier temperatures, and air and hydrogen flow rates. The operating for electrode prepared with 20 wt% Pt loaded 0.3 mgPt/cm2 in single cell (25 cm2) showed that diverse parameters as pressures, humidifier temperatures, flow rate of air /hydrogen have an effects on the electrode performance. Results show better power density for high pressure, high air flow rate, and for low humidifier temperature, low H2 flow rate. The increase in pressure ratio results increases in the current density and power density from 91.96 to 99.96 mA/cm2 and from 32.56{mW/cm2} to 35.48 {mW/cm2} for an air/H2 ratio of 1/0.5 bar and 3/2 bar, respectively. The hydrogen and air flow with the stoichiometry coefficient ratio 2/1 is the best value to achieve better performance by a flow rate of 0.3 L/min for H2 and 0.6 L/min for air, which correspond to a current density and power density of 103.96{mA/cm2} and 31.56{mW/cm2}.

scholarly journals Performance Analysis of a PEM Fuel Cell Stack Having 150 cm2 Active Layer by Using Design of Experiments (DOE)

2020 ◽  
Vol 162 ◽  
pp. 01004
Author(s):  
Elif Eker Kahveci ◽  
Imdat Taymaz
Keyword(s):  
Fuel Cell ◽  
Power Density ◽  
Active Layer ◽  
Flow Rate ◽  
Polymer Electrolyte Membrane ◽  
Operating Conditions ◽  
Cell Temperature ◽  
Fuel Cell Stack ◽  
Electrolyte Membrane ◽  
Optimization Study

In this study, the effects of operating parameters on power density of a 3-cell PEMFC (Polymer Electrolyte Membrane Fuel Cell) stack with serpentine flow channels having 150 cm2 total active layer have been examined experimentally. Desing Expert, which is the experimental design program (trial version) was used, and the data obtained as a result of the experiments were analyzed by entering this program. A total of 25 experiments were carried out according to the design created with the data entered into the program within the specified operating conditions range. The independent variables were entered which are cell temperature, humidification temperature, H2 flow rate and O2 flow rate, and the response is the power density. In this study, the hydrophobic cell stack which has the highest cell performance of which was previous studies results was used. In the optimization study, keeping the power density and maximum H2 flow to a minimum, the most suitable values are cell temperature 57.826°C, humidification temperature 56.151°C, O2 flow 1.587 L/min. Finally 432.398 mW/cm2 power density value was obtained under these operating conditions.

An autonomous untethered fast soft robotic insect driven by low-voltage dielectric elastomer actuators

2019 ◽  
Vol 4 (37) ◽  
pp. eaaz6451 ◽  
Author(s):  
Xiaobin Ji ◽  
Xinchang Liu ◽  
Vito Cacucciolo ◽  
Matthias Imboden ◽  
Yoan Civet ◽  
...  
Keyword(s):  
Power Density ◽  
Optical Sensors ◽  
Autonomous Navigation ◽  
Printed Circuit Board ◽  
Low Voltage ◽  
Dielectric Elastomer ◽  
Circuit Board ◽  
Operating Voltage ◽  
Dielectric Elastomer Actuators ◽  
Flexible Printed Circuit

Insects are a constant source of inspiration for roboticists. Their compliant bodies allow them to squeeze through small openings and be highly resilient to impacts. However, making subgram autonomous soft robots untethered and capable of responding intelligently to the environment is a long-standing challenge. One obstacle is the low power density of soft actuators, leading to small robots unable to carry their sense and control electronics and a power supply. Dielectric elastomer actuators (DEAs), a class of electrostatic electroactive polymers, allow for kilohertz operation with high power density but require typically several kilovolts to reach full strain. The mass of kilovolt supplies has limited DEA robot speed and performance. In this work, we report low-voltage stacked DEAs (LVSDEAs) with an operating voltage below 450 volts and used them to propel an insect-sized (40 millimeters long) soft untethered and autonomous legged robot. The DEAnsect body, with three LVSDEAs to drive its three legs, weighs 190 milligrams and can carry a 950-milligram payload (five times its body weight). The unloaded DEAnsect moves at 30 millimeters/second and is very robust by virtue of its compliance. The sub–500-volt operation voltage enabled us to develop 780-milligram drive electronics, including optical sensors, a microcontroller, and a battery, for two channels to output 450 volts with frequencies up to 1 kilohertz. By integrating this flexible printed circuit board with the DEAnsect, we developed a subgram robot capable of autonomous navigation, independently following printed paths. This work paves the way for new generations of resilient soft and fast untethered robots.

Stabilization of the Speed of the Hydraulic Motor Through Throttle Compensation for Volume Losses

2020 ◽  
Vol 26 (3) ◽  
pp. 126-130
Author(s):  
Krasimir Kalev
Keyword(s):  
Flow Rate ◽  
Hydraulic Drive ◽  
Pressure Change ◽  
Operating Conditions ◽  
Drive System ◽  
Inlet Pressure ◽  
Schematic Diagram ◽  
Hydraulic Characteristics ◽  
Hydraulic Motor ◽  
Flow Through

AbstractA schematic diagram of a hydraulic drive system is provided to stabilize the speed of the working body by compensating for volumetric losses in the hydraulic motor. The diagram shows the inclusion of an originally developed self-adjusting choke whose flow rate in the inlet pressure change range tends to reverse - with increasing pressure the flow through it decreases. Dependent on the hydraulic characteristics of the hydraulic motor and the specific operating conditions.

scholarly journals Chemical–Electrochemical Process Concept for Lead Recovery from Waste Cathode Ray Tube Glass

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1546
Author(s):  
Árpád Imre-Lucaci ◽  
Melinda Fogarasi ◽  
Florica Imre-Lucaci ◽  
Szabolcs Fogarasi
Keyword(s):  
Flow Rate ◽  
Current Density ◽  
Complete Recovery ◽  
Electrochemical Process ◽  
Operating Conditions ◽  
General Effect ◽  
Optimal Operating ◽  
Recirculation Flow ◽  
Lead Recovery ◽  
Cathode Ray Tube

This paper presents a novel approach for the recovery of lead from waste cathode-ray tube (CRT) glass by applying a combined chemical-electrochemical process which allows the simultaneous recovery of Pb from waste CRT glass and electrochemical regeneration of the leaching agent. The optimal operating conditions were identified based on the influence of leaching agent concentration, recirculation flow rate and current density on the main technical performance indicators. The experimental results demonstrate that the process is the most efficient at 0.6 M acetic acid concentration, flow rate of 45 mL/min and current density of 4 mA/cm2. The mass balance data corresponding to the recycling of 10 kg/h waste CRT glass in the identified optimal operating conditions was used for the environmental assessment of the process. The General Effect Indices (GEIs), obtained through the Biwer Heinzle method for the input and output streams of the process, indicate that the developed recovery process not only achieve a complete recovery of lead but it is eco-friendly as well.

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