Design of Three New Cam-Based Constant-Force Mechanisms

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Javier López-Martínez ◽  
Daniel García-Vallejo ◽  
Francisco Manuel Arrabal-Campos ◽  
Jose Manuel Garcia-Manrique
Keyword(s):  
Compliant Mechanisms ◽  
Rolling Friction ◽  
Design Guidelines ◽  
Design Parameters ◽  
Constant Force ◽  
Equilibrium Equations ◽  
Constant Input ◽  
Friction Forces ◽  
Input Force ◽  
Cam Profile

Constant-force mechanisms are designed to keep a constant or nearly constant input force along a prescribed stroke of the mechanism. The implementation of this kind of mechanisms has been approached in literature using compliant mechanisms or through a certain combination of springs and nonlinear transmissions. In this work, three new constant-force mechanisms based on the use of springs, rollers, and cams are presented and analyzed. The rolling friction forces between the rollers and the cam are included in the force equilibrium equations and considered in the integration of the cam profile. The influence of the friction force on the input force as well as the design parameters involved is studied based on numerical techniques and simulations. In fact, the results evidence that to obtain a precise constant-force mechanism, rolling friction forces must be considered in the cam profile definition. The main design guidelines for the three constant-force mechanisms proposed are described.

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.

A Constant-Force Compliant Gripper for Handling Objects of Various Sizes

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Jung-Yuan Wang ◽  
Chao-Chieh Lan
Keyword(s):  
Force Feedback ◽  
Constant Force ◽  
The Novel ◽  
Constant Input ◽  
Input Force ◽  
Simulation Results ◽  
Force Mechanism ◽  
Gripping Force ◽  
And Control ◽  
Constant Force Mechanism

This paper presents the design, simulation, and testing of a compliant gripper that can provide a constant gripping force to handle objects of various sizes. Maintaining a proper gripping force is challenging when manipulating delicate objects with uncertain sizes and stiffnesses. To avoid damage and provide a stable grip of an object, force feedback is often required so that the gripping force can be directly or indirectly regulated. Without using additional sensors and control, the proposed gripper passively maintains a constant prespecified contact force between fingertip and object. The gripper is designed to have a constant input force generated by a constant-force mechanism (CFM). Transmitted through a statically balanced (SB) mechanism, a constant gripping force is obtained at the fingertip. After a formulation to find the optimal gripper configuration, the design is verified through comparison with simulation results. Finally, a prototype of the constant-force gripper is demonstrated. The novel gripper is expected to serve as a reliable alternative for object manipulation.

Front steering design guidelines formulation for e-scooters considering the influence of sitting and standing riders on self-stability and safety performance

2021 ◽  
pp. 095440702199217
Author(s):  
Milan Paudel ◽  
Fook Fah Yap
Keyword(s):  
Preventive Measures ◽  
Recent Trend ◽  
Dynamic Performance ◽  
Design Guidelines ◽  
Safety Performance ◽  
Design Parameters ◽  
Single Track ◽  
Standing Posture ◽  
Last Mile ◽  
Current Design

E-scooters are a recent trend and are viewed as a sustainable solution to ease the first and last mile problem in modern transportation. However, an alarming rate of accidents, injuries, and fatalities have caused a significant setback for e-scooters. Many preventive measures and legislation have been put on the e-scooters, but the number of accidents and injuries has not reduced considerably. In this paper, the current design approach of e-scooters has been analyzed, and the most common range of design parameters have been identified. Thereafter, validated mathematical models have been used to quantify the performance of e-scooters and relate them with the safety aspects. Both standing and seated riders on e-scooters have been considered, and their influence on the dynamic performance has been analyzed and compared with the standard 26-in wheel reference safety bicycle. With more than 80% of the accidents and injuries occurring from falling or colliding with obstacles, this paper tries to correlate the dynamics of uncontrolled single-track vehicles with the safety performance of e-scooters. The self-stability, handling, and braking effect have been considered as major performance matrices. The analysis has shown that the current e-scooter designs are not as stable as the reference safety bicycle. Moreover, these e-scooters have been found unstable within the most common range of legislated riding velocity. The results corroborate with the general perception that the current designs of e-scooters are less stable, easy to lose control, twitchy, or wobbly to ride. Furthermore, the standing posture of the rider on the e-scooter has been found dangerous while braking to avoid any disturbances such as potholes or obstacles. Finally, the front steering design guidelines have been proposed to help modify the current design of e-scooters to improve the dynamic performance, hence the safety of the e-scooter riders and the surroundings.

Design and experimental validation of a cam-based constant-force compression mechanism with friction considered

2018 ◽  
Vol 233 (11) ◽  
pp. 3873-3887 ◽  
Author(s):  
Ming Li ◽  
Wei Cheng ◽  
Ruili Xie
Keyword(s):  
Design Theory ◽  
High Efficiency ◽  
Rolling Friction ◽  
Constant Force ◽  
Identification Method ◽  
Compression Mechanism ◽  
Engineering Significance ◽  
Nonlinear Vibration Control ◽  
Preparatory Work ◽  
Differential Relationship

Due to the quasi-zero-stiffness and overload protection characteristics, constant-force mechanisms can be widely used in nonlinear vibration control, high-efficiency shock isolation, and other engineering fields. As a preparatory work for the further applications, this paper presents a cam-based constant-force compression mechanism and validates the quasi-static characteristics experimentally. By employing the friction considered profile identification method to design the cam and through the interaction between the cam and spring-sliders, the constant-force compression mechanism can passively output the desired constant force over a sufficiently large displacement. The design theory is firstly introduced in detail. Through establishing and solving the differential relationship between the lateral elastic force and vertical constant force, the constant-force compression mechanism under various frictional conditions can be designed. Then, constant-force compression mechanism prototypes corresponding to sliding and rolling friction are designed, fabricated and tested respectively. The results show that both the prototypes have the satisfactory characteristics as with the design requirements. Moreover, the relative generality and stronger engineering applicability of the proposed friction considered profile identification method are proved since it can not only cover the frictionless (micro-friction) cases, but keep the constant-force behavior of the constant-force compression mechanism under the nonignorable friction conditions. Therefore, compared with the existing cam-roller constant-force mechanisms that must ensure the ignoring micro-friction demand, the presented constant-force compression mechanism taking friction into consideration has important engineering significance since it can reduce this machining requirement.

Theoretical and Experimental Study on the Ultimate Strength of Corrugated Bulkheads

1997 ◽  
Vol 41 (04) ◽  
pp. 301-317
Author(s):  
Jeom K. Paik ◽  
Anil K. Thayamballi ◽  
Min S. Chun
Keyword(s):  
Ultimate Strength ◽  
Lateral Pressure ◽  
Limit State ◽  
Plate Thickness ◽  
Experimental Information ◽  
Design Guidelines ◽  
Design Parameters ◽  
Collapse Mechanism ◽  
Ultimate Limit State ◽  
Analytical Formulation

The objectives of the present study are to obtain experimental data on collapse strength of steel corrugated bulkhead models and also to develop a simple analytical formulation for ultimate strength useful in the design of corrugated bulkheads under static lateral pressure. Collapse tests on nine mild steel corrugated bulkhead models having five bays of corrugations are carried out, varying the corrugation angle, the plate thickness and the type of loading (axial compression and/or lateral pressure). Using the test data, the characteristics of the collapse mechanism for corrugated bulkheads are investigated. For purposes of rapid first cut estimates of strength, a new and simple analytical formulation for predicting the ultimate strength of corrugated bulkheads under hydrostatic pressure is derived based on an assumed stress distribution over the corrugation cross section at the ultimate limit state. The modeling error associated with the new formulation is established by comparing its predictions with the experimental results. The development of ultimate strength based design guidelines and the effect of design parameters such as the corrugation angle on ultimate strength of a corrugated bulkhead are then discussed. All experimental information and strength data are tabulated, which is a benefit in itself.

scholarly journals Analytical substantiation of constructive parameters of rotating field board of plow’s body

2019 ◽  
Vol 126 ◽  
pp. 00038
Author(s):  
Vladimir Konovalov ◽  
Sergey Konovalov ◽  
Victoria Igumnova
Keyword(s):  
Sliding Friction ◽  
Rolling Friction ◽  
High Energy ◽  
Cultivated Plants ◽  
Friction Forces ◽  
Technical Parameters ◽  
Cutting Resistance ◽  
Different Depths ◽  
Analytical Relations ◽  
Rotating Field

The article shows importance of use of dump plowing for formation and maintenance of soil structure and pest control and diseases of cultivated plants. A significant drawback of plowing process is indicated, which is its high energy intensity. To reduce energy consumption, it is proposed to use rotating field boards, which allow replacing sliding friction forces with rolling friction forces. The article presents a description of design of plow’s body with rotating field board and notes that without a preliminary analytical study and justification of initial parameters, their use may not be effective. Analytical relations connecting value of radius of rotating field of board, rate of collapse of soil, allowable value of indentation of field board into soil and specific force of cutting resistance of soil that ability to use it for baseline technical parameters. To analyze obtained dependence, the article presents its graphical solution. The authors obtained an expression for determining the value of arm’s force of reference reaction from soil to balance a plow’s body, in addition, this indicator can be used to adjust a body when working on soils with different physical and mechanical parameters and at different depths.

Analysis of mechanical errors in disc cam mechanisms

2005 ◽  
Vol 219 (2) ◽  
pp. 209-224 ◽  
Author(s):  
L-I Wu ◽  
W-T Chang
Keyword(s):  
Exact Solution ◽  
Analytical Method ◽  
Sudden Change ◽  
Design Parameters ◽  
Combined Effects ◽  
Worst Case ◽  
Cam Mechanism ◽  
Radial Dimension ◽  
Cam Profile ◽  
Shift Angle

This paper presents an analytical method for analysing the mechanical errors of disc cam mechanisms. With the aid of parametric expressions of the cam profile and by employing the concept of equivalent linkage, the error of the follower motion that is due to the variation in each design parameter can be determined analytically. The resulting error equations do not really involve the location of the curvature centre of the cam profile, and thus locating the curvature centre of the cam profile is not essential. The method is validated through analysing a cam mechanism that has an invariant equivalent linkage, and thus an exact solution is available. Compared with the exact solutions, the predicted results have at least four-figure accuracy. For the roller follower cases, the pressure angle has most effect on the resulting error. Owing to the counteraction of the shift angle, the resulting error due to the radial dimension error of the cam profile has relatively smaller variation. In the worst case, owing to the combined effects of various design parameters, the accuracy of the follower motion may degrade considerably. The acceleration error functions have a sudden change at the ends of the motion.

3D Finite Element Modeling of GFRP-Reinforced Concrete Deep Beams without Shear Reinforcement

2017 ◽  
Vol 15 (02) ◽  
pp. 1850001 ◽  
Author(s):  
George Markou ◽  
Mohammad AlHamaydeh
Keyword(s):  
Reinforced Concrete ◽  
Mechanical Behavior ◽  
Numerical Investigation ◽  
Numerical Models ◽  
Design Guidelines ◽  
Design Parameters ◽  
Shear Reinforcement ◽  
Deep Beams ◽  
Modes Of Failure ◽  
Hexahedral Elements

This paper presents the numerical investigation of nine Glass Fiber-Reinforced Polymer (GFRP) concrete deep beams through the use of numerically-efficient 20-noded hexahedral elements. Cracking is taken into account by means of the smeared crack approach and the bars are simulated as embedded rod elements. The developed numerical models are validated against published experimental results. The validation beams spanned a practical range of varying design parameters; namely, shear span-to-depth ratio, concrete specified compressive strength and flexural reinforcement ratio. The motivation for this research is to accurately yet efficiently capture the mechanical behavior of the GFRP-reinforced concrete deep beams. The presented numerical investigation demonstrated close correlations of the force–deformation relationships that are numerically predicted and their experimental counterparts. Moreover, the numerically predicted modes of failure are also found to be conformal to those observed experimentally. The proposed modeling approach that overcame previous computational limitations has further demonstrated its capability to accurately model larger and deeper beams in a computationally efficient manner. The validated modeling technique can then be efficiently used to perform extensive parametric investigations related to behavior of this type of structural members. The modeling method presented in this work paves the way for further parametric investigations of the mechanical behavior of GFRP-reinforced deep beams without shear reinforcement that will serve as the base for proposing new design guidelines. As a deeper understanding of the behavior and the effect of the design parameters is attained, more economical and safer designs will emerge.

A Two-Dimensional Adjustable Constant-Force Mechanism

2019 ◽  
Vol 142 (6) ◽  
Author(s):  
Yu-Ling Kuo ◽  
Chao-Chieh Lan
Keyword(s):  
Limited Range ◽  
Two Dimensions ◽  
Working Environment ◽  
Design Parameters ◽  
Constant Force ◽  
Two Dimensional ◽  
Output Force ◽  
Constant Output ◽  
Force Variation ◽  
Force Mechanism

Abstract Constant-force mechanisms (CFMs) can produce an almost invariant output force over a limited range of input displacement. Without using additional sensor and force controller, adjustable CFMs can passively produce an adjustable constant output force to interact with the working environment. In the literature, one-dimensional CFMs have been developed for various applications. This paper presents the design of a novel CFM that can produce adjustable constant force in two dimensions. Because an adjustable constant force can be produced in each radial direction, the proposed adjustable CFM can be used in applications that require two-dimensional force regulation. In this paper, the design formulation and simulation results are presented and discussed. Equations to minimize the output force variation are given to choose the design parameters optimally. A prototype of the two-dimensional CFM is tested to demonstrate the effectiveness and accuracy of adjustable force regulation. This novel CFM is expected to be used in machines or robots to interact friendly with the environment.

Synthesis of Compliant Mechanisms With Specified Equilibrium Positions

2005 ◽  
Author(s):  
Hai-Jun Su ◽  
J. Michael McCarthy
Keyword(s):  
Compliant Mechanisms ◽  
Equilibrium Constraints ◽  
Equilibrium Equations ◽  
Equilibrium Configurations ◽  
Form Design ◽  
Design Requirements ◽  
Synthesis Procedure ◽  
Position Synthesis ◽  
Four Bar Linkage ◽  
Sine And Cosine Functions

This paper presents a synthesis procedure for a compliant four-bar linkage with three specified equilibrium configurations. The finite position synthesis equations are combined with equilibrium constraints at the flexure pivots to form design equations. These equations are simplified by modeling the joint angle variables in the equilibrium equations using sine and cosine functions. Solutions to these design equations were computed using a polynomial homotopy solver. In order to provide a design specification, we first compute the six equilibrium configurations of a known compliant four-bar mechanism. We use these results as design requirements to synthesize a compliant four-bar. The solver obtained eight real solutions which we refined using a Newton-Raphson technique. A numerical example is provided to verify the design methodology.

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