Towards the Design of a Statically Balanced Compliant Laparoscopic Grasper Using Topology Optimization

2008 ◽  
Author(s):  
Ditske J. B. A. de Lange ◽  
Matthijs Langelaar ◽  
Just L. Herder
Keyword(s):  
Topology Optimization ◽  
Force Feedback ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Negative Stiffness ◽  
Compensation Mechanism ◽  
Laparoscopic Grasper ◽  
The Difference ◽  
Force Displacement ◽  
Compliant Mechanism Design

This paper presents the design of a grasping instrument for minimally invasive surgery. Due to its small dimensions a compliant mechanism seems promising. To obtain force feedback, the positive stiffness of the compliant grasper must be statically balanced by a negative-stiffness compensation mechanism. For the design of compliant mechanisms, topology optimization can be used. The goal of this paper is to investigate the applicability of topology optimization to the design of a compliant laparoscopic grasper and particularly a compliant negative-stiffness compensation mechanism. In this study, the problem is subdivided in the grasper part and the compensation part. In the grasper part the deflection at the tip of the grasper is optimized. This results in a design that has a virtually linear force-displacement characteristic that forms the input for the compensation part. In the compensation part the difference between the force-displacement characteristic of the grasper part and the characteristic of the compensation part is minimized. An optimization problem is formulated enabling a pre-stress to be incorporated, which is required to obtain the negative stiffness in the compensation part. We can conclude that topology optimization is a promising approach in the field of statically balanced compliant mechanism design, even though there is great scope improvement of the method.

Piezoelectric Actuator Performance Metrics and Relation to Compliant Mechanism Design

2001 ◽  
Author(s):  
Hima Maddisetty ◽  
Mary Frecker
Keyword(s):  
Topology Optimization ◽  
Performance Metrics ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Mechanical Efficiency ◽  
High Energy ◽  
High Energy Density ◽  
High Bandwidth ◽  
Compliant Mechanism Design ◽  
Actuator Performance

Abstract Piezoceramic actuators have gained widespread use due to their desirable qualities of high force, high bandwidth, and high energy density. Compliant mechanisms can be designed for maximum stroke amplification of piezoceramic actuators using topology optimization. In this paper, the mechanical efficiency and other performance metrics of such compliant mechanism/actuator systems are studied. Various definitions of efficiency and other performance metrics of actuators with amplification mechanisms from the literature are reviewed. These metrics are then applied to two compliant mechanism example problems and the effect of the stiffness of the external load is investigated.

Hybrid Compliant Mechanism Design Using a Mixed Mesh of Flexure Hinge Elements and Beam Elements Through Topology Optimization

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Lin Cao ◽  
Allan T. Dolovich ◽  
Wenjun (Chris) Zhang
Keyword(s):  
Topology Optimization ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Optimization Technique ◽  
Flexure Hinge ◽  
Beam Elements ◽  
Flexure Hinges ◽  
New Type ◽  
Meshing Scheme ◽  
Compliant Mechanism Design

This paper proposes a topology optimization framework to design compliant mechanisms with a mixed mesh of both beams and flexure hinges for the design domain. Further, a new type of finite element, i.e., super flexure hinge element, was developed to model flexure hinges. Then, an investigation into the effects of the location and size of a flexure hinge in a compliant lever explains why the point-flexure problem often occurs in the resulting design via topology optimization. Two design examples were presented to verify the proposed technique. The effects of link widths and hinge radii were also investigated. The results demonstrated that the proposed meshing scheme and topology optimization technique facilitate the rational decision on the locations and sizes of beams and flexure hinges in compliant mechanisms.

Negative Stiffness Building Blocks for Statically Balanced Compliant Mechanisms: Design and Testing

2010 ◽  
Vol 2 (4) ◽  
Author(s):  
Karin Hoetmer ◽  
Geoffrey Woo ◽  
Charles Kim ◽  
Just Herder
Keyword(s):  
Force Feedback ◽  
High Efficiency ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Building Blocks ◽  
Negative Stiffness ◽  
High Fidelity ◽  
Proof Of Concept ◽  
Design Considerations ◽  
Design And Testing

In some applications, nonconstant energy storage in the flexible segments of compliant mechanisms is undesired, particularly when high efficiency or high-fidelity force feedback is required. In these cases, the principle of static balancing can be applied, where a balancing segment with a negative stiffness is added to cancel the positive stiffness of the compliant mechanism. This paper presents a strategy for the design of statically balanced compliant mechanisms and validates it through the fabrication and testing of proof-of-concept prototypes. Three compliant mechanisms are statically balanced by the use of compressed plate springs. All three balanced mechanisms have approximately zero stiffness but suffer from a noticeable hysteresis loop and finite offset from zero force. Design considerations are given for the design and fabrication of statically balanced compliant mechanisms.

Concept and Modeling of a Statically Balanced Compliant Laparoscopic Grasper

2009 ◽  
Author(s):  
Nima Tolou ◽  
Just L. Herder
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Force Feedback ◽  
Negative Stiffness ◽  
Optimized Design ◽  
Compensation Mechanism ◽  
Linear Elastic Material ◽  
Element Modeling ◽  
Linear Elastic ◽  
Laparoscopic Grasper

The objective of this investigation is to present a concept as well as mathematical modeling and finite element modeling of a statically balanced compliant laparoscopic grasper. To obtain force feedback, the positive stiffness of the compliant grasper was statically balanced by a negative-stiffness compensation mechanism. The negative stiffness has been produced by pairs of pre-stressed initially-curved pinned-pinned beams out of linear elastic material, arranged perpendicular to the link driving the grasper. First, the conceptual design is explained. Subsequently, its behavior is mathematically formulated and then finite element modeling is implemented using a commercially available finite element modeling package. Finally, a stress-optimized design of a negative-stiffness compensation mechanism and the effect of parameter changes on the accuracy are obtained. The results illustrate the efficiency of the applied analysis methods for the case of statically balancing the laparoscopic grasper. It also demonstrates the efficiency of the balancer concept. The proposed procedure is found to be convenient for this set of problems, and can probably be applied to other similar practical problems.

Hinge-Free Compliant Mechanism Design Via the Topological Level-Set

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Anirudh Krishnakumar ◽  
Krishnan Suresh
Keyword(s):  
Topology Optimization ◽  
Numerical Experiments ◽  
Control Parameter ◽  
Compliant Mechanisms ◽  
Volume Fraction ◽  
Compliant Mechanism ◽  
Target Volume ◽  
Stiffness Matrices ◽  
2D And 3D ◽  
Compliant Mechanism Design

The objective of this paper is to introduce and demonstrate a new method for the topology optimization of compliant mechanisms. The proposed method relies on exploiting the topological derivative, and exhibits numerous desirable properties including: (1) the mechanisms are hinge-free; (2) mechanisms with different geometric and mechanical advantages (GA and MA) can be generated by varying a single control parameter; (3) a target volume fraction need not be specified, instead numerous designs, of decreasing volume fractions, are generated in a single optimization run; and (4) the underlying finite element stiffness matrices are well-conditioned. The proposed method and implementation are illustrated through numerical experiments in 2D and 3D.

A Building Block Approach for the Design of Statically Balanced Compliant Mechanisms

2009 ◽  
Author(s):  
Karin Hoetmer ◽  
Just L. Herder ◽  
Charles J. Kim
Keyword(s):  
Building Block ◽  
Force Feedback ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Building Blocks ◽  
Negative Stiffness ◽  
High Fidelity ◽  
Input Output ◽  
Input And Output ◽  
Block Approach

Particularly when high-fidelity force feedback is required, such as in surgical forceps, the energy loss between input and output in compliant mechanisms is undesired. To restore the force feedback, the principle of static balancing can be applied, where a balancing segment with a negative stiffness is added to a compliant mechanism. Currently there are no mature methods for the design of statically balanced compliant mechanisms (SBCM). The goal of this paper is to investigate the possibility of extending the Building Block Approach for the design of statically balanced compliant mechanisms. To this end, the Building Block Approach is extended with negative stiffness balancing building blocks that can be added to a designed compliant mechanism. To demonstrate the feasibility of the method, a statically balanced compliant gripper was designed by this Extended Building Block Approach. The maximum operating force of the unbalanced gripper of 3.5 N was reduced to −1 N for the balanced gripper. Thus, the gripper is slightly overbalanced. The gripper example demonstrates the functionality of the proposed method; the input-output stiffness of a compliant mechanism can be severely reduced by a balancing segment.

Topology Optimization of Compliant Mechanisms Using Hybrid Discretization Model

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Hong Zhou
Keyword(s):  
Topology Optimization ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Optimization Procedure ◽  
Optimization Method ◽  
Diagonal Element ◽  
Initial Guess ◽  
Stress Constraint ◽  
Design Variables ◽  
Hybrid Discretization

The hybrid discretization model for topology optimization of compliant mechanisms is introduced in this paper. The design domain is discretized into quadrilateral design cells. Each design cell is further subdivided into triangular analysis cells. This hybrid discretization model allows any two contiguous design cells to be connected by four triangular analysis cells whether they are in the horizontal, vertical, or diagonal direction. Topological anomalies such as checkerboard patterns, diagonal element chains, and de facto hinges are completely eliminated. In the proposed topology optimization method, design variables are all binary, and every analysis cell is either solid or void to prevent the gray cell problem that is usually caused by intermediate material states. Stress constraint is directly imposed on each analysis cell to make the synthesized compliant mechanism safe. Genetic algorithm is used to search the optimum and to avoid the need to choose the initial guess solution and conduct sensitivity analysis. The obtained topology solutions have no point connection, unsmooth boundary, and zigzag member. No post-processing is needed for topology uncertainty caused by point connection or a gray cell. The introduced hybrid discretization model and the proposed topology optimization procedure are illustrated by two classical synthesis examples of compliant mechanisms.

A Well-Behaved Revolute Flexure Joint for Compliant Mechanism Design

1999 ◽  
Vol 121 (3) ◽  
pp. 424-429 ◽  
Author(s):  
M. Goldfarb ◽  
J. E. Speich
Keyword(s):  
Mechanism Design ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Bending Properties ◽  
Thin Beam ◽  
Primary Mechanism ◽  
Joint Characteristics ◽  
Flexure Joints ◽  
Compliant Mechanism Design ◽  
Torsional Properties

This paper describes the design of a unique revolute flexure joint, called a split-tube flexure, that enables (lumped compliance) compliant mechanism design with a considerably larger range-of-motion than a conventional thin beam flexure, and additionally provides significantly better multi-axis revolute joint characteristics. Conventional flexure joints utilize bending as the primary mechanism of deformation. In contrast, the split-tube flexure joint incorporates torsion as the primary mode of deformation, and contrasts the torsional properties of a thin-walled open-section member with the bending properties of that member to obtain desirable joint behavior. The development of this joint enables the development of compliant mechanisms that are quite compliant along kinematic axes, extremely stiff along structural axes, and are capable of kinematically well-behaved large motions.

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