Synthesis of Constant Torque Compliant Mechanisms

2015 ◽  
Author(s):  
Hong Zhou ◽  
Hari Nair Prakashah
Keyword(s):  
Compliant Mechanisms ◽  
Large Range ◽  
Compliant Mechanism ◽  
Design Domain ◽  
Control Parameters ◽  
Constant Torque ◽  
Fixed Ring ◽  
Output Torque ◽  
Spline Curves ◽  
Medical And Healthcare

Constant torque compliant mechanisms produce an output torque that does not change in a large range of input rotation. They have wide applications in aerospace, automobile, timing, gardening, medical and healthcare devices. Unlike constant force compliant mechanisms, the synthesis of constant torque compliant mechanisms has not been extensively investigated yet. In this paper, a method is presented for synthesizing constant torque compliant mechanisms that have coaxial input rotation and output torque. The same shaft is employed for both input rotation and output torque. A synthesized constant torque compliant mechanism is modeled as a set of variable width spline curves within an annular design domain formed between a rotation shaft and a fixed ring. Interpolation circles are used to define variable width spline curves. The synthesis of constant torque compliant mechanisms is systematized as optimizing the control parameters of the interpolation circles of the variable width spline curves. The presented method is demonstrated by the synthesis of constant torque compliant mechanisms that have different number of variable width spline curves in the paper.

Synthesis of Constant Torque Compliant Mechanisms

2016 ◽  
Vol 8 (6) ◽  
Author(s):  
Hari Nair Prakashah ◽  
Hong Zhou
Keyword(s):  
Compliant Mechanisms ◽  
Large Range ◽  
Compliant Mechanism ◽  
Design Domain ◽  
Control Parameters ◽  
Constant Torque ◽  
Fixed Ring ◽  
Output Torque ◽  
Spline Curves ◽  
Medical And Healthcare

Constant torque compliant mechanisms produce an output torque that does not change in a large range of input rotation. They have wide applications in aerospace, automobile, timing, gardening, medical, and healthcare devices. Unlike constant force compliant mechanisms, the synthesis of constant torque compliant mechanisms has not been extensively investigated yet. In this paper, a method is presented for synthesizing constant torque compliant mechanisms that have coaxial input rotation and output torque. The same shaft is employed for both input rotation and output torque. A synthesized constant torque compliant mechanism is modeled as a set of variable width spline curves within an annular design domain formed between a rotation shaft and a fixed ring. Interpolation circles are used to define variable width spline curves. The synthesis of constant torque compliant mechanisms is systematized as optimizing the control parameters of the interpolation circles of the variable width spline curves. The presented method is demonstrated by the synthesis of constant torque compliant mechanisms that have different number of variable width spline curves in this paper.

Synthesizing Bidirectional Constant Torque Compliant Mechanisms

2017 ◽  
Author(s):  
Bhavanam Praveen Reddy ◽  
Hong Zhou
Keyword(s):  
Unique Feature ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Synthesis Method ◽  
Control Parameters ◽  
Curved Beams ◽  
Rotation Direction ◽  
Constant Torque ◽  
Output Torque ◽  
Spline Curves

The output or resisting torque from a constant torque compliant mechanism keeps invariant in a large range of input rotation. Unlike regular constant torque compliant mechanisms that have only one input rotation direction, the input rotation of a bidirectional constant torque compliant mechanism can be either clockwise or counter-clockwise. Its resisting or output torque reverses its direction with the change of the input rotation direction. The unique feature of bidirectional constant torque compliant mechanisms makes their synthesis challenging. In this paper, a synthesis method is introduced to surmount the synthesis challenges. The constant resisting torque is generated through a set of curved beams that are mounted within an annular design domain. Because of the bidirectional requirement, the two ends of each curved beam are aligned along radial direction before deformation to avoid rotational bias. Spline curves are employed to describe curved beams and defined by their control parameters. The synthesis of a bidirectional constant torque compliant mechanism is systematized as optimizing the control parameters of its curved beams. The presented method is demonstrated by the synthesis of bidirectional constant torque compliant mechanisms that have different arrangements of curved beams in the paper.

Synthesizing Constant Torque Compliant Mechanisms Using Precompressed Beams

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Ishit Gandhi ◽  
Hong Zhou
Keyword(s):  
Compliant Mechanisms ◽  
Large Range ◽  
Compliant Mechanism ◽  
Synthesis Method ◽  
Building Blocks ◽  
Constant Torque ◽  
A Value ◽  
Output Torque ◽  
Aerospace Medical ◽  
Medical Healthcare

A constant torque compliant mechanism (CM) generates an output torque that keeps invariant in a large range of input rotation. Because of the constant torque feature and the merits of CMs, they are used in automobile, aerospace, medical, healthcare, timing, gardening, and other devices. A common problem in the current constant torque CMs is their preloading range that is a certain starting range of the input rotation. In the preloading range, the output torque of a constant torque CM does not have the desired constant torque. It increases from zero to a value. The preloading range usually accounts for one-third of the entire input rotation range, which severally weakens the performance of constant torque CMs. In this paper, the preloading problem is eradicated by using precompressed beams as building blocks for constant torque CMs. It is challenging to synthesize constant torque CMs composed of precompressed beams because of the integrated force, torque, and deflection characteristics. The synthesis of constant torque CMs is systemized as parameter optimization of the composed precompressed beams. The presented synthesis method is demonstrated by synthesizing constant torque CMs with different numbers of precompressed beams and validated by experimental results.

Constant Force Compliant Mechanisms Without Preloading

2021 ◽  
Author(s):  
Premkumar Pujali ◽  
Hong Zhou
Keyword(s):  
Compliant Mechanisms ◽  
Large Range ◽  
Compliant Mechanism ◽  
Experimental Results ◽  
Design Parameters ◽  
Constant Force ◽  
Spline Curves ◽  
Output Force

Abstract A constant force compliant mechanism generates an output force that keeps invariant in a large range of input displacement. Because of the constant force feature and the merits of compliant mechanisms, they are utilized in many applications. A problem in the current constant force compliant mechanisms is their preloading range that is a certain starting range of the input displacement. In the preloading displacement, the output force of a constant force compliant mechanism does not have the desired value. It goes up from zero value. The preloading displacement often occupies one quarter or more of the entire input displacement range, which weakens the performance of constant force compliant mechanisms. The preloading issue is eradicated in this research by using prebuckled beams as components for constructing constant force compliant mechanisms. It is difficult to synthesize constant force compliant mechanisms that are composed of prebuckled beams because of the intertwined force, buckling and deflection characteristics. In this research, the undeformed beams are represented by spline curves and controlled by its interpolation points. The synthesis of constant force compliant mechanisms is systemized as optimizing the design parameters of the composed prebuckled beams. Fully compliant constant force compliant mechanisms are synthesized without preloading. The synthesis solutions are validated by experimental results.

Synthesizing Bidirectional Constant Torque Compliant Mechanisms Using Precompressed Beams

2018 ◽  
Author(s):  
Monik Thanaki ◽  
Hong Zhou
Keyword(s):  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Building Blocks ◽  
Design Parameters ◽  
Input Shaft ◽  
Rotation Direction ◽  
Constant Torque ◽  
A Value ◽  
Output Torque ◽  
Large Scope

A constant torque compliant mechanism has its output torque invariant in a large scope of input rotation. Different from conventional constant torque compliant mechanisms in which the input shaft can only rotate in one direction, the input shaft of a bidirectional constant torque compliant mechanism can rotate either clockwise or counter-clockwise. The direction of the output or resisting torque changes with the input rotation direction. A common problem in the current bidirectional constant torque compliant mechanisms is that they require a preloading range that is a certain starting range of the input rotation. Within the preloading range, the output torque does not have the desired torque, and it increases from zero to a value. The preloading range weakens the performance of bidirectional constant torque compliant mechanisms. In this paper, precompressed beams are used as building blocks for bidirectional constant torque compliant mechanisms to surmount the preloading problem. Bidirectional constant torque compliant mechanisms are synthesized through optimizing the design parameters of the composed precompressed beams. The introduced synthesis approach is demonstrated by synthesizing bidirectional constant torque compliant mechanisms that have different numbers of precompressed beams.

The Uncertainty Elimination in Discrete Topology Optimization of Compliant Mechanisms

2013 ◽  
Author(s):  
Hong Zhou ◽  
Satya Raviteja Kandala
Keyword(s):  
Topology Optimization ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Optimization Process ◽  
Design Domain ◽  
Discrete Topology ◽  
Optimization Strategy ◽  
Hybrid Discretization ◽  
Ambiguous Point

Topology uncertainty leads to different topology solutions and makes topology optimization ambiguous. Point connection and grey cell might cause topology uncertainty. They are both eradicated when hybrid discretization model is used for discrete topology optimization. A common topology uncertainty in the current discrete topology optimization stems from mesh dependence. The topology solution of an optimized compliant mechanism might be uncertain when its design domain is discretized differently. To eliminate topology uncertainty from mesh dependence, the genus based topology optimization strategy is introduced in this paper. The topology of a compliant mechanism is defined by its genus which is the number of holes in the compliant mechanism. With this strategy, the genus of an optimized compliant mechanism is actively controlled during its topology optimization process. There is no topology uncertainty when this strategy is incorporated into discrete topology optimization. The introduced topology optimization strategy is demonstrated by examples with different degrees of genus.

Wide Curve Based Geometric Optimization of Compliant Mechanisms

2005 ◽  
Author(s):  
Hong Zhou ◽  
Kwun-Lon Ting
Keyword(s):  
Optimization Problem ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Optimization Procedure ◽  
Optimization Method ◽  
Geometric Optimization ◽  
Programming Algorithm ◽  
Free Form ◽  
Control Parameters ◽  
Practical Constraints

A wide curve is a curve with width or cross-section. This paper presents a geometric optimization method of compliant mechanisms based on the free form wide curve theory. With the proposed method, geometric optimization can be performed to further improve the performance of a compliant mechanism after its topology is selected. Every connection in the topology is represented as a parametric wide curve in which variable shape and size are fully described and conveniently controlled by the limited number of parameters. The geometric optimization is formulated on the control parameters of the wide curves corresponding to all connections in the topology. Problem-dependent objectives are optimized and practical constraints are imposed during the optimization process. The optimization problem is solved by the constrained nonlinear programming algorithm in Matlab Optimization Toolbox. An example is presented to verify the effectiveness of the proposed optimization procedure.

Design and Modeling of a Large Amplitude Compliant Revolute Joint: The Helical Shape Compliant Joint

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Arnaud Bruyas ◽  
Francois Geiskopf ◽  
Pierre Renaud
Keyword(s):  
Numerical Simulation ◽  
Large Amplitude ◽  
Compliant Mechanisms ◽  
Large Range ◽  
Compliant Mechanism ◽  
Rotational Stiffness ◽  
Revolute Joint ◽  
Stiffness Model ◽  
Compliant Joint ◽  
Compliant Mechanism Design

In this paper, the design and modeling of a large amplitude compliant revolute joint are introduced. Based on the implementation of multimaterial additive manufacturing (MM-AM), the joint is of interest for robotic contexts where the design of compact and accurate compliant mechanisms is required. The joint design is first experimentally proven to offer a large range of motion and satisfying kinetostatic properties. A parametric study is then conducted using numerical simulation to define the most interesting geometries. An experimental study is in a third step presented to estimate the rotational stiffness, including the manufacturing impact. A stiffness model is provided for relevant geometries, and their use is finally discussed in the context of compliant mechanism design.

Synthesis of Path Generation Compliant Mechanisms Using Variable Width Spline Curves

2014 ◽  
Author(s):  
Hong Zhou ◽  
Nisar Ahmed
Keyword(s):  
Compliant Mechanisms ◽  
Path Generation ◽  
Shape Description ◽  
Control Parameters ◽  
Spline Curve ◽  
Spline Curves ◽  
Curved Paths ◽  
Generation Mechanisms ◽  
Synthesis Approach ◽  
Interpolation Nodes

Path generation is to guide a point tracing a prescribed path. Compliant mechanisms (CMs) have been synthesized for path generation mechanisms. In this paper, each connection in a synthesized CM is represented as a variable width spline curve and the entire synthesized CM is modeled as a set of variable width spline curves. The synthesis of a path generation CM is systemized as the optimization of control parameters of a set of variable width spline curves. A variable width spline curve is a center spline curve with variable perpendicular width. The center spline curve is for the shape description of its represented connection while variable width is for the size of the connection. The shape and size of a variable width spline curve is defined by its interpolation circles. The locations of interpolation circles are utilized as interpolation nodes of the center spline curve for connection shape and the diameters of interpolations circles are interpolated for connection size. The centers of all interpolation circles in a synthesized CM form a network of nodes. The network of nodes decides the topology of the synthesized CM and can be classified based on degree of genus (DOG). The presented synthesis approach is demonstrated by synthesizing CMs with different DOGs to generate curved paths.

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.

Sign in / Sign up

Export Citation Format

Share Document