Bistable Configurations of Compliant Mechanisms Modeled Using Four Links and Translational Joints

2004 ◽  
Vol 126 (4) ◽  
pp. 657-666 ◽  
Author(s):  
Brian D. Jensen ◽  
Larry L. Howell
Keyword(s):  
Energy Storage ◽  
Prior Knowledge ◽  
Compliant Mechanisms ◽  
Power Input ◽  
Local Minima ◽  
Stored Energy ◽  
Bistable Behavior ◽  
Micro Electro Mechanical Systems ◽  
Bistable Mechanism ◽  
Mechanical Devices

Bistable mechanical devices remain stable in two distinct positions without power input. They find application in valves, switches, closures, and clasps. Mechanically bistable behavior results from the storage and release of energy, typically in springs, with stable positions occurring at local minima of stored energy. Compliant mechanisms offer an elegant way to achieve this behavior by incorporating both motion and energy storage into the same flexible element. Interest in compliant bistable mechanisms has also recently increased because of the advantages of bistable behavior in many micro-electro-mechanical systems (MEMS). Design of compliant or rigid-body bistable mechanisms typically requires simultaneous consideration of both energy storage and motion requirements. This paper simplifies this process by developing theory that provides prior knowledge of mechanism configurations that guarantee bistable behavior. Configurations which include one or more translational, or slider, joints are studied in this work. Several different mechanism types are analyzed to determine compliant segment placement that will ensure bistable mechanism operation. Examples demonstrate the power of the theory in design.

Bistable Compliant Four-Bar Mechanisms With a Single Torsional Spring

2006 ◽  
Author(s):  
Adarsh Mavanthoor ◽  
Ashok Midha
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Mechanism Design ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Stored Energy ◽  
Element Analysis ◽  
Bistable Behavior ◽  
Torsional Spring ◽  
Bistable Mechanism

Significant reduction in cost and time of bistable mechanism design can be achieved by understanding their bistable behavior. This paper presents bistable compliant mechanisms whose pseudo-rigid-body models (PRBM) are four-bar mechanisms with a torsional spring. Stable and unstable equilibrium positions are calculated for such four-bar mechanisms, defining their bistable behavior for all possible permutations of torsional spring locations. Finite Element Analysis (FEA) and simulation is used to illustrate the bistable behavior of a compliant mechanism with a straight compliant member, using stored energy plots. These results, along with the four-bar and the compliant mechanism information, can then be used to design a bistable compliant mechanism to meet specified requirements.

Identification of Compliant Pseudo-Rigid-Body Four-Link Mechanism Configurations Resulting in Bistable Behavior

2003 ◽  
Vol 125 (4) ◽  
pp. 701-708 ◽  
Author(s):  
Brian D. Jensen ◽  
Larry L. Howell
Keyword(s):  
Energy Storage ◽  
Rigid Body ◽  
Mechanism Design ◽  
Bistable Behavior ◽  
Strongly Coupled ◽  
Present Design ◽  
Stable Equilibria ◽  
Motion Characteristics ◽  
Bistable Mechanism ◽  
Design Challenges

Bistable mechanisms, which have two stable equilibria within their range of motion, are important parts of a wide variety of systems, such as closures, valves, switches, and clasps. Compliant bistable mechanisms present design challenges because the mechanism’s energy storage and motion characteristics are strongly coupled and must be considered simultaneously. This paper studies compliant bistable mechanisms which may be modeled as four-link mechanisms with a torsional spring at one joint. Theory is developed to predict compliant and rigid-body mechanism configurations which guarantee bistable behavior. With this knowledge, designers can largely uncouple the motion and energy storage requirements of a bistable mechanism design problem. Examples demonstrate the power of the theory in bistable mechanism design.

An Investigation Into Compliant Bistable Mechanisms

1998 ◽  
Author(s):  
Patrick G. Opdahl ◽  
Brian D. Jensen ◽  
Larry L. Howell
Keyword(s):  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Paper Briefly ◽  
Bistable Behavior ◽  
New Class ◽  
Force And Motion ◽  
Predicted Values ◽  
Motion Characteristics ◽  
Bistable Mechanism ◽  
Mechanism Theory

Abstract This paper proposes a new class of bistable mechanisms: compliant bistable mechanisms. These mechanisms gain their bistable behavior from the energy stored in the flexible segments which deflect to allow mechanism motion. This approach integrates desired mechanism motion and energy storage to create bistable mechanisms with dramatically reduced part count compared to traditional mechanisms incorporating rigid links, joints, and springs. This paper briefly reviews bistable mechanism theory, introduces some additional bistable mechanism characteristics, and integrates this theory with compliant mechanism theory. The resulting theory of bistable compliant mechanisms is validated by measuring the force and motion characteristics of several test mechanisms and comparing them to predicted values.

Identification of Compliant Pseudo-Rigid-Body Mechanism Configurations Resulting in Bistable Behavior

2000 ◽  
Author(s):  
Brian D. Jensen ◽  
Larry L. Howell
Keyword(s):  
Energy Storage ◽  
Rigid Body ◽  
Mechanism Design ◽  
Bistable Behavior ◽  
Strongly Coupled ◽  
Present Design ◽  
Stable Equilibria ◽  
Motion Characteristics ◽  
Bistable Mechanism ◽  
Design Challenges

Abstract Bistable mechanisms, which have two stable equilibria within their range of motion, are important parts of a wide variety of systems, such as closures, valves, switches, and clasps. Compliant bistable mechanisms present design challenges because the mechanism’s energy storage and motion characteristics are strongly coupled and must be considered simultaneously. This paper studies compliant bistable mechanisms which may be modeled as four-link mechanisms with a torsional spring at one joint. Theory is developed to predict compliant and rigid-body mechanism configurations which guarantee bistable behavior. With this knowledge, designers can largely uncouple the motion and energy storage requirements of a bistable mechanism design problem. Examples demonstrate the power of the theory in bistable mechanism design.

Design of Two-Link, In-Plane, Bistable Compliant Micro-Mechanisms

1999 ◽  
Vol 121 (3) ◽  
pp. 416-423 ◽  
Author(s):  
B. D. Jensen ◽  
L. L. Howell ◽  
L. G. Salmon
Keyword(s):  
Energy Efficiency ◽  
Power Input ◽  
Stable States ◽  
External Disturbances ◽  
Bistable Behavior ◽  
Positioning Accuracy ◽  
Body Model ◽  
Rigid Body Model ◽  
Bistable Mechanism ◽  
Storage Characteristics

A bistable mechanism has two stable states within its range of motion. Its advantages include the ability to stay in two positions without power input and despite small external disturbances. Therefore, bistable micro-mechanisms could allow the creation of MEMS with improved energy efficiency and positioning accuracy. This paper presents bistable micro-mechanisms which function within the plane of fabrication. These bistable mechanisms, called “Young” bistable mechanisms, obtain their energy storage characteristics from the deflection of two compliant members. They have two pin joints connected to the substrate, and can be constructed of two layers of polysilicon. The pseudo-rigid-body model is used to analyze and design these mechanisms. This approach allows greater freedom and flexibility in the design process. The mechanisms were fabricated and tested to demonstrate their bistable behavior and to determine the repeatability of their stable positions.

Introduction of Two-Link, In-Plane, Bistable Compliant MEMS

1998 ◽  
Author(s):  
Brian D. Jensen ◽  
Larry L. Howell ◽  
Linton G. Salmon
Keyword(s):  
Power Input ◽  
Stable States ◽  
External Disturbances ◽  
Bistable Behavior ◽  
Analysis And Design ◽  
Body Model ◽  
Process Testing ◽  
Rigid Body Model ◽  
Bistable Mechanism ◽  
Storage Characteristics

Abstract A bistable mechanism has two stable states within its range of motion. Its advantages include the ability to stay in two positions without power input and despite small external disturbances. Therefore, bistable micro-mechanisms could allow the creation of MEMS with improved energy efficiency and positioning accuracy. This paper presents the first bistable MEMS which function within the plane of fabrication. These bistable mechanisms, known as “Young” bistable mechanisms, obtain their energy storage characteristics from the deflection of two compliant members, have two pin joints connected to the substrate, and can be constructed of two layers of polysilicon. The pseudo-rigid-body model overcomes problems with nonlinearities in the analysis and design of these mechanisms. This approach allows greater freedom and flexibility in the design process. Testing of the mechanisms demonstrated their bistable behavior and the repeatability of the stable positions.

Achieving Multistability Through Use of a Single Bistable Compliant Mechanism

2010 ◽  
Author(s):  
Guimin Chen ◽  
Yanjie Gou ◽  
Aimei Zhang
Keyword(s):  
Stable Equilibrium ◽  
Compliant Mechanism ◽  
Power Input ◽  
Successful Operation ◽  
New Approaches ◽  
Reconfigurable Robots ◽  
Bistable Mechanism

A compliant multistable mechanism is capable of steadily staying at multiple distinct positions without power input. Many applications including switches, valves, relays, positioners, and reconfigurable robots may benefit from multistability. In this paper, two new approaches for synthesizing compliant multistable mechanisms are proposed, which enable designers to achieve multistability through the use of a single bistable mechanism. The synthesis approaches are described and illustrated by several design examples. Compound use of both approaches is also discussed. The design potential of the synthesis approaches is demonstrated by the successful operation of several instantiations of designs that exhibit three, four, five, and nine stable equilibrium positions, respectively. The synthesis approaches enable us to design a compliant mechanism with a desired number of stable positions.

Preliminary Design and Performance Assessment of an Underwater CAES System (UW-CAES) for Wind Power Balancing

2019 ◽  
Author(s):  
Marco Astolfi ◽  
Giulio Guandalini ◽  
Marco Belloli ◽  
Adriano Hirn ◽  
Paolo Silva ◽  
...  
Keyword(s):  
Energy Storage ◽  
Performance Assessment ◽  
Power Input ◽  
Compressed Air ◽  
Preliminary Design ◽  
Round Trip ◽  
Peak Shaving ◽  
Renewable Power ◽  
And Performance

Abstract A key approach to large renewable power management is based on implementing storage technologies, including batteries, power-to-gas and compressed air energy storage (CAES). This work presents the preliminary design and performance assessment of an innovative type of CAES, based on underwater storage volumes (UW-CAES) and intended for installation in the proximity of deep water seas or lakes. The UW-CAES works with constant hydrostatic pressure storage and variable volumes. The proposed system is adiabatic, not using any fuel to increase the air temperature before expansion; a sufficient TIT is instead obtained through a thermal energy storage system which recovers the compression heat. The system includes (i) a set of turbomachines (modular multi-stage compressor, with partial intercooling; expansion turbine); (ii) a thermal energy storage (TES) system with different temperature levels designed to recover a large fraction of the compression heat, allowing the subsequent heating of air prior to the expansion phase; (iii) an underwater modular compressed air storage, conceived as a network of rigid but open tanks lying on the seabed and allowing a variable-volume and constant pressure operation. The compressor operates at variable loads, following an oscillating renewable power input, according to strategies oriented to improve the overall system dispatchability; the expander can be designed to work either at full load, thanks to the stability of the air flow rate and of the TIT guaranteed by the thermal storage, or at variable load. The paper first discusses in detail the sizing and off-design characterization of the overall system; it is then simulated a case study where the UW-CAES is coupled to a wind farm for peak shaving and dispatchability enhancement, evaluating the impact of a realistic power input on performances and plant flexibility. Although the assessment shall be considered preliminary, it is shown that round trip efficiency in the range of 75%–80% can be obtained depending on the compressor section configuration; making the UW-CAES a promising technology compared to electrochemical and pumped-hydro storage systems. The technology is also applied to perform peak-shaving of the electricity production from a wind park; annual simulations considering part load operation result in global round trip efficiency around 75% with a 10 to 15% reduction in the average unplanned energy injection in the electric grid. The investigated case study provides an example of the potential of this system in providing power output peak shaving when coupled with an intermittent and non-predictable energy source.

scholarly journals Si3N4 nanofelts/paraffin composites as novel thermal energy storage architecture

2020 ◽  
Vol 56 (2) ◽  
pp. 1537-1550
Author(s):  
Francesco Valentini ◽  
Andrea Dorigato ◽  
Alessandro Pegoretti ◽  
Michele Tomasi ◽  
Gian D. Sorarù ◽  
...  
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Composite Structures ◽  
Liquid Paraffin ◽  
Stored Energy ◽  
Storage Efficiency ◽  
Novel Material ◽  
Energy Storage Efficiency ◽  
Change Material

Abstract The environmental problems associated with global warming are urging the development of novel systems to manage and reduce the energy consumption. An attractive route to improve the energy efficiency of civil buildings is to store the thermal energy thanks, during heating, to the phase transition of a phase-change material (as paraffin) from the solid to the liquid state and vice versa. The stored energy can be then released under cooling. Herein, we developed a novel material (nanofelt) constituted by Si3N4 nanobelts able to absorb huge amounts of liquid paraffin in the molten state and to act as an efficient shape stabilizer. The nanofelt manufacturing technology is very simple and easy to be scaled-up. The effect of the Si3N4 nanofelts density and microstructure on the paraffin sorption and leakage and on the thermal properties of the resulting composite structures is investigated. It is shown that the produced Si3N4/paraffin composites are able to retain enormous fractions of paraffin (up to 70 wt%) after 44 day of desorption test on absorbent paper towel. The thermal energy storage efficiency measured through calorimetric tests is as high as 77.4% in heating and 80.1% in cooling.

An Energy Formulation for Parametric Size and Shape Optimization of Compliant Mechanisms

1999 ◽  
Vol 121 (2) ◽  
pp. 229-234 ◽  
Author(s):  
J. A. Hetrick ◽  
S. Kota
Keyword(s):  
Shape Optimization ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Optimization Procedure ◽  
Stress Constraints ◽  
Optimization Techniques ◽  
Mechanical Transmission ◽  
Dimensional Synthesis ◽  
Size And Shape ◽  
Mechanical Devices

Compliant mechanisms are jointless mechanical devices that take advantage of elastic deformation to achieve a force or motion transformation. An important step toward automated design of compliant mechanisms has been the development of topology optimization techniques. The next logical step is to incorporate size and shape optimization to perform dimensional synthesis of the mechanism while simultaneously considering practical design specifications such as kinematic and stress constraints. An improved objective formulation based on maximizing the energy throughput of a linear static compliant mechanism is developed considering specific force and displacement operational requirements. Parametric finite element beam models are used to perform the size and shape optimization. This technique allows stress constraints to limit the maximum stress in the mechanism. In addition, constraints which restrict the kinematics of the mechanism are successfully applied to the optimization problem. Resulting optimized mechanisms exhibit efficient mechanical transmission and meet kinematic and stress requirements. Several examples are given to demonstrate the effectiveness of the optimization procedure.

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