A Load-Adjustable Constant-Force Mechanism

2018 ◽  
Author(s):  
Steven Hasara ◽  
Craig Lusk
Keyword(s):  
Reaction Force ◽  
Longitudinal Axis ◽  
Degree Of Freedom ◽  
Constant Force ◽  
Force Output ◽  
Constant Output ◽  
Force Mechanism ◽  
Constant Force Mechanism ◽  
Novel Design ◽  
Second Degree

This paper outlines the design of a compliant crank slider with adjustable constant-force output. Constant-force mechanisms (CFM) are used to maintain a constant output reaction force throughout a large range of compressive motion. This novel design improves on existing CFM by introducing a second degree of freedom that adjusts the mechanism’s output without changing its kinematic structure. This second degree of freedom is the rotation of a compliant beam about its longitudinal axis as it is constrained to the initial plane of bending. The resulting change in the beam’s stiffness allows for adjustment to a specifiable range of constant-force outputs.

The Design and Analysis of a Compliant Constant-Force Mechanism

2016 ◽  
Author(s):  
Zhongtian Xie ◽  
Lifang Qiu
Keyword(s):  
Compliant Mechanism ◽  
Reaction Force ◽  
Constant Force ◽  
Element Analysis ◽  
Fea Model ◽  
Electrical Connector ◽  
Force Mechanism ◽  
Input Motion ◽  
Operational Range ◽  
Constant Force Mechanism

Compliant constant-force mechanisms (CFM) are a type of compliant mechanism which produce a reaction force at the output port that does not change for a large range of input motion. This paper describes a new compliant CFM, introduces its design and configuration-improvement process. A finite element analysis (FEA) model of the compliant CFM was created to evaluate its constant force behavior. The FEA result shows that when the displacement is Δ = 4 mm, the compliant CFM maintains a nearly constant force in the operational displacement range of 1.31 mm to 4 mm with an error of 5.05%. The operational range accounts for 67% of the total motion. This compliant CFM can be used to regulate the contact force of a robot end-effector or as an electrical connector.

An Adjustable Constant-Force Mechanism for Adaptive End-Effector Operations

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Yi-Ho Chen ◽  
Chao-Chieh Lan
Keyword(s):  
Compliant Mechanism ◽  
Displacement Curve ◽  
Constant Force ◽  
Force Output ◽  
Control Effort ◽  
End Effector ◽  
Linear Spring ◽  
End Effectors ◽  
Force Mechanism ◽  
Constant Force Mechanism

Force regulation is a challenging problem for robot end-effectors when interacting with an unknown environment. It often requires sophisticated sensors with computerized control. This paper presents an adjustable constant-force mechanism (ACFM) to passively regulate the contact force of a robot end-effector. The proposed ACFM combines the negative stiffness of a bistable mechanism and positive stiffness of a linear spring to generate a constant-force output. Through prestressing the linear spring, the constant-force magnitude can be adjusted to adapt to different working environments. The ACFM is a monolithic compliant mechanism that has no frictional wear and is capable of miniaturization. We propose a design formulation to find optimal mechanism configurations that produce the most constant-force. A resulting force to displacement curve and maximal stress curve can be easily manipulated to fit a different application requirement. Illustrated experiments show that an end-effector equipped with the ACFM can adapt to a surface of variable height, without additional motion programming. Since sensors and control effort are minimized, we expect this mechanism can provide a reliable alternative for robot end-effectors to interact friendly with an environment.

scholarly journals Design, Analysis and Testing of a New Compliant Compound Constant-Force Mechanism

Actuators ◽  
2018 ◽  
Vol 7 (4) ◽  
pp. 65 ◽  
Author(s):  
Xiaozhi Zhang ◽  
Guangwei Wang ◽  
Qingsong Xu
Keyword(s):  
Maximum Stress ◽  
Contact Process ◽  
Constant Force ◽  
Force Output ◽  
Element Analysis ◽  
Input Force ◽  
Force Structure ◽  
Force Mechanism ◽  
Design And Testing ◽  
Constant Force Mechanism

This paper presents the design and testing of a novel flexure-based compliant compound constant-force mechanism (CCFM). One uniqueness of the proposed mechanism lies in that it achieves both constant-force input and constant-force output, which is enabled by integrating two types of sub-mechanisms termed active and passive constant-force structures, respectively. Unlike conventional structures, the active constant-force structure allows the reduction on input force requirement and thus the enlargement of motion stroke provided that the maximum stress of the material is within allowable value. While the passive one offers a safe environmental interaction during the contact process. Analytical model of the proposed CCFM is derived which is verified by simulation study with finite element analysis (FEA). A prototype mechanism is fabricated by a 3D printer to demonstrate the performance of the proposed CCFM design. Experimental results reveal the effectiveness of the reported CCFM.

Design and Evaluation of Compliant Constant-Force Mechanisms

1996 ◽  
Author(s):  
Alisa J. Millar ◽  
Larry L. Howell ◽  
James N. Leonard
Keyword(s):  
Strain Energy ◽  
Experimental Validation ◽  
Large Range ◽  
Constant Force ◽  
Dimensional Synthesis ◽  
Output Force ◽  
Simplified Method ◽  
Constant Output ◽  
Force Mechanism ◽  
Constant Force Mechanism

Abstract Compliant constant-force mechanisms combine the effects of mechanical advantage and stored strain energy of flexible members to obtain constant output forces for a large range of input displacements. This paper extends and compliments previous work by accomplishing the following: i) dimensional synthesis is performed for a number of compliant constant-force mechanism configurations, ii) a simplified method of determining the magnitude of the constant output force is presented, and iii) experimental validation of the theory is addressed by reporting the results of testing three constant-force configurations. The results of i) and ii) are presented in a manner to be easily used by engineers designing such mechanisms. The results of iii) show that the mechanisms do follow a nearly constant force for a large input displacement, as predicted.

Simplified modelling and development of a bi-directionally adjustable constant-force compliant gripper

2016 ◽  
Vol 231 (11) ◽  
pp. 2110-2123 ◽  
Author(s):  
Guangbo Hao ◽  
John Mullins ◽  
Kevin Cronin
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Negative Stiffness ◽  
Displacement Curve ◽  
Constant Force ◽  
Force Output ◽  
Element Analysis ◽  
Force Mechanism ◽  
Bistable Mechanism ◽  
Constant Force Mechanism

This paper proposes the design of a wholly mechanical constant-force gripper that can accommodate the imprecise manipulation of brittle/delicate objects by the actuation. This was achieved by designing a constant-force mechanism as the jaw that allowed a constant force to be applied to the grasping objects regardless of the displacement of the mechanism. The constant-force mechanism is attached to the end effector of the gripper via a parallelogram mechanism which ensures that the jaws remain in parallel. The constant-force mechanism combines the negative stiffness of a bistable mechanism and the positive stiffness of a linear spring to generate a constant force output. By preloading the positive stiffness mechanism, the magnitude of the constant force can be adjusted to be as low as zero. The constant-force mechanism has been fully modelled and simulated using finite element analysis. A normalised force-displacement curve has been developed that allows to obtain the simplified analytical negative stiffness of the bistable mechanism. The design formulation to find the optimal configuration that produces the most constant force has been developed. Illustrated experiments prove the concept of the design although the discrepancies between finite element analysis results and testing results exist due to bistable beam manufacturing error.

Dimensional Synthesis of Compliant Constant-Force Slider Mechanisms

1994 ◽  
Author(s):  
Larry L. Howell ◽  
Ashok Midha ◽  
Morgan D. Murphy
Keyword(s):  
Compliant Mechanisms ◽  
Design Procedure ◽  
Constant Force ◽  
Dimensional Synthesis ◽  
Model Concept ◽  
Output Force ◽  
Rigid Body Model ◽  
Constant Output ◽  
Force Mechanism ◽  
Constant Force Mechanism

Abstract Constant-force mechanisms produce a constant output force for a range of input displacements. Such mechanisms are important in applications with a varying displacement but a constant resultant force required. Constant-force mechanism designs have been limited to rigid-link mechanisms, but the design of compliant, or flexible link, constant force mechanisms could increase the number of applications by taking advantage of the unique characteristics of compliant mechanisms. Murphy (1993) developed type-synthesis theories for compliant mechanisms and applied them to generate possible configurations for compliant constant-force slider mechanisms. This paper concentrates on the dimensional synthesis of several of the resulting topologies. Optimization and the pseudo-rigid-body-model concept are employed in the design procedure. An example application as an electrical connection for use in electronic chip carriers is also illustrated.

Synthesis of Single-Input and Multiple-Output Port Mechanisms with Springs for Specified Energy Absorption

1994 ◽  
Vol 116 (3) ◽  
pp. 937-943 ◽  
Author(s):  
J. G. Jenuwine ◽  
A. Midha
Keyword(s):  
Energy Absorption ◽  
Output Port ◽  
Constant Force ◽  
Plane Symmetry ◽  
Multiple Precision ◽  
Linear Spring ◽  
Single Input ◽  
Force Mechanism ◽  
Closure Method ◽  
Constant Force Mechanism

A means of synthesis of single-input and multiple-output port mechanisms for specified energy absorption is formulated for multiple precision points. The synthesis presented makes use of an extension of the loop closure method which includes expressions for energy absorption by linear spring elements. The configuration considered locates spring elements at two output ports of a multi-loop, planar mechanism. Economies realized for the symmetric mechanism are discussed for both one- and two-plane symmetry. Synthesis examples are included for both the general and symmetric mechanism. Special applications presented include synthesis of a constant force mechanism and synthesis of a mechanism suited to the energy absorption requirements of an automotive crashworthiness system.

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