Feasibility Study of a Fully Compliant Statically Balanced Laparoscopic Grasper

2004 ◽  
Author(s):  
Aa¨ron Stapel ◽  
Just L. Herder
Keyword(s):  
Feasibility Study ◽  
Compliant Mechanisms ◽  
Primary Concern ◽  
Compensation Mechanism ◽  
Force Transmission ◽  
Hand Grip ◽  
Single Piece ◽  
Spring Force ◽  
Laparoscopic Grasper ◽  
Compliant Parts

Compliant mechanisms have many advantages over their rigid-body counterparts. One disadvantage however is the fact that motion of the mechanism is associated with elastic energy storage in the compliant parts. This is a problem especially in cases where accurate force transmission is of primary concern, such as in medical graspers. A solution to this problem is to statically balance the elastic forces by the addition of a spring force compensation mechanism, such that the effect of the compliance is neutralized. The complete resulting mechanisms resulting from this concept are called statically balanced compliant mechanisms (SBCMs). This paper presents a feasibility study into the design of a grasper for medical purposes and demonstrates that the concept is possible and practically viable. It is shown that the compliant gripper of a laparoscopic forceps can be statically balanced with a single-piece compliant compensation mechanism, with a balancing error of only 0.03N while dimensions are such that the compensation part of the mechanism can be stored inside the hand grip of the instrument.

Statically Balanced Compliant Mechanisms (SBCM’S): An Example and Prospects

2000 ◽  
Author(s):  
Just L. Herder ◽  
Fred P. A. van den Berg
Keyword(s):  
Force Feedback ◽  
Compliant Mechanisms ◽  
Compensation Mechanism ◽  
Force Transmission ◽  
Low Friction ◽  
Transmission Process ◽  
Transmission Quality ◽  
Gripping Force ◽  
Elastic Elements

Abstract In some applications of compliant mechanisms, the fact that energy is stored in the elastic members presents a problem. For instance, in manually operated instruments, such as surgical forceps, the operating force should preferably be proportional to the gripping force, while forces introduced by the bending of elastic elements would disturb this force transmission process. To restore the force transmission quality, compliant mechanisms may be statically balanced, resulting in statically balanced compliant mechanisms (SBCM’s). This paper presents an example of a compliant surgical forceps mechanism, which is statically balanced by a low-friction rolling-link compensation mechanism. Force feedback is restored to the extent that the pulse in an artificial artery can be perceived clearly.

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.

scholarly journals Review Article: Inventory of platforms towards the design of a statically balanced six degrees of freedom compliant precision stage

2011 ◽  
Vol 2 (2) ◽  
pp. 157-168 ◽  
Author(s):  
A. G. Dunning ◽  
N. Tolou ◽  
J. L. Herder
Keyword(s):  
Degrees Of Freedom ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Compensation Mechanism ◽  
Precision Engineering ◽  
Six Degrees Of Freedom ◽  
Actuation Force ◽  
Precision Stage ◽  
Compliant Parts ◽  
Great Scope

Abstract. For many applications in precision engineering, a six degrees of freedom (DoF) compliant stage (CS) with zero stiffness is desirable, to deal with problems like backlash, friction, lubrication, and at the same time, reduce the actuation force. To this end, the compliant stage (also known as compliant mechanism) can be statically balanced with a stiffness compensation mechanism, to compensate the energy stored in the compliant parts, resulting in a statically balanced compliant stage (SBCS). Statically balanced compliant stages can be a breakthrough in precision engineering. This paper presents an inventory of platforms suitable for the design of a 6 DoF compliant stage for precision engineering. A literature review on 3–6 DoF compliant stages, static balancing strategies and statically balanced compliant mechanisms (SBCMs) has been performed. A classification from the inventory has been made and followed up by discussion. An obviously superior architecture for a 6 DoF compliant stage was not found. All the 6 DoF stages are either non-statically balanced compliant structures or statically balanced non-compliant structures. The statically balanced non-compliant structures can be transformed into compliant structures using lumped compliance, while all SBCMs had distributed compliance. A 6 DoF SBCS is a great scope for improvements in precision engineering stages.

scholarly journals Effect of laparoscopic grasper force transmission ratio on grasp control

2008 ◽  
Vol 23 (4) ◽  
pp. 818-824 ◽  
Author(s):  
Eleonora P. Westebring-van der Putten ◽  
John J. van den Dobbelsteen ◽  
Richard H. M. Goossens ◽  
Jack J. Jakimowicz ◽  
Jenny Dankelman
Keyword(s):  
Transmission Ratio ◽  
Force Transmission ◽  
Laparoscopic Grasper

Design and Fabrication of a Hybrid Body-Powered Prosthetic Hand With Voluntary Opening and Voluntary Closing Capabilities

2011 ◽  
Author(s):  
Timothy Sullivan ◽  
Kwok Siong Teh
Keyword(s):  
The United States ◽  
Human Hand ◽  
Prosthetic Hand ◽  
Force Transmission ◽  
Switching Mechanism ◽  
Future Design ◽  
Single Function ◽  
Hybrid Mechanism ◽  
Wide Range ◽  
Spring Force

There are currently over 500,000 people with upper extremity amputations living in the United States. Among this population—despite the introduction of advanced myoelectric technology—body-powered hand prosthetics remain the hand prosthetic of choice because they are inexpensive, durable, and are easier and cheaper to maintain than myoelectric prosthetics. Yet, body-powered prosthetics tend to have less functionality than myoelectric prosthetics because their output is often limited to a single function—voluntary opening (VO) or voluntary closing (VC). Although these functions serve the same purpose—to grasp an object—they are executed in opposite ways, catering to different body movements, hand actions, and rest positions. In reality, a human hand is more adequately modeled by a VO/VC hybrid mechanism than a standalone VO or VC mechanism. There is therefore a critical need to develop prosthetics with combined VO and VC functions in order to augment their capabilities and to more closely mimic the human hand. This paper presents the design, fabrication, and analysis of a combined, hybrid VO and VC prosthetic hand that is simplistic and electronics-free. To realize a hybrid VO and VC prosthetic hand, we designed and fabricated an easy push-pull switching mechanism for changing between VO and VC and investigated the efficacy of this switching mechanism in response to the wide range of force transmission necessitated by the VC and VO functions. The mechanical switching mechanism is activated with a force of 1 to 1.5N. The mechanism itself is constructed using a system of gears that allow for the direction of force to be changed, effectively providing the foundation for which VO and VC functions can exist in a single prosthetic. This switching mechanism could potentially be used in combination with a number of different prehensor types, catering to a wide range of users. We used a 3.5″ TRS-style prehensor for our prototype and designed the switch to apply a 21 N force while in VO mode and up to 100 N while in VC mode. In our design, VO and VC modes offer characteristics that are identical to existing VO and VC designs, with a few exceptions. These exceptions include an increase in weight, as low as 12% energy loss in VC mode and 9% loss in VO mode due to gears, more complex mechanics, larger required space, and a higher spring force in VC mode. Future design improvements will be discussed in this paper.

Compliant Wireform Mechanisms

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
Tyler M. Pendleton ◽  
Brian D. Jensen
Keyword(s):  
Rigid Body ◽  
Compliant Mechanisms ◽  
Finite Element Models ◽  
Simplified Models ◽  
New Class ◽  
Body Model ◽  
Single Piece ◽  
Rigid Body Model ◽  
Torsion Springs ◽  
Torsion Bar

This paper presents an alternative to fabrication methods commonly used in compliant mechanisms research, resulting in a new class of compliant mechanisms called wireform mechanisms. This technique integrates torsional springs made of formed wire into compliant mechanisms. In this way the desired force, stiffness, and motion can be achieved from a single piece of formed wire. Two techniques of integrating torsion springs are fabricated and modeled: helical coil torsion springs and torsion bars. Because the mechanisms are more complex than ordinary springs, simplified models, which aid in design, are presented, which represent the wireform mechanisms as rigid-body mechanisms using the pseudo-rigid-body model. The method is demonstrated through the design of a mechanically tristable mechanism. The validity of the simplified models is discussed by comparison to finite element models and, in the case of the torsion-bar mechanism, to experimental measurements.

Two Stage Design of Compliant Mechanisms With Superelastic Compliant Joints

2017 ◽  
Author(s):  
Jovana Jovanova ◽  
Mary Frecker
Keyword(s):  
Analytical Model ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Functionally Graded ◽  
Two Stage ◽  
Stage Design ◽  
Rigid Link ◽  
Starting Point ◽  
Single Piece ◽  
Two Stage Design

The design of compliant mechanisms made of Nickel Titanium (NiTi) Shape Memory Alloys (SMAs) is considered to exploit the superelastic behavior of the material to achieve tailored high flexibility on demand. This paper focuses on two-stage design optimization of compliant mechanisms, as a systematic method for design of the composition of the functionally graded NiTi material within the compliant mechanism devices. The location, as well as geometric and mechanical properties, of zones of high and low flexibility will be selected to maximize mechanical performance. The proposed two-stage optimization procedure combines the optimization of an analytical model of a single-piece functionally graded unit, with a detailed FEA of a continuous compliant mechanism. In the first stage, a rigid-link model is developed to initially approximate the behavior of the compliant mechanism. In the second stage the solution of the rigid-link problem serves as the starting point for a continuous analytical model where the mechanism consists of zones with different material properties and geometry, followed by a detailed FEA of a compliant mechanism with integrated zones of superelasticity. The two-stage optimization is a systematic approach for compliant mechanism design with functional grading of the material to exploit superelastic response in controlled manner. Direct energy deposition, as an additive manufacturing technology, is foreseen to fabricate assemblies with multiple single piece functional graded components. This method could be applied to bio-inspired structures, flapping wings, flexible adaptive structures and origami inspired compliant mechanisms.

scholarly journals Topology Synthesis of Compliant Systems With Embedded Actuators and Sensors

2008 ◽  
Author(s):  
Brian Trease ◽  
Sridhar Kota
Keyword(s):  
Adaptive Systems ◽  
Compliant Mechanisms ◽  
Single Point ◽  
Sensor Placement ◽  
System Response ◽  
Structural Topology ◽  
Force Transmission ◽  
Basic Premise ◽  
Starting Point ◽  
Compliant Systems

The basic premise of a compliant system is the integration of motion/force transmission via elastic deformation with embedded actuation and sensing. Current electromechanical systems are generally fashioned in the rigid-and-discrete paradigm where one first designs a rigid structure with mechanical joints and then adds actuators and sensors, with the design of controls only following as an afterthought. The objective of this research is a systems approach to synthesis of mechanism, structure, actuation, and sensing, thereby advancing from traditional mechanical design to automated compliant system design. In previous studies of compliant mechanisms and their synthesis, single-actuator mechanisms have primarily been considered, with the determination of the actuator’s type, orientation, size, and location occurring outside of the automated design synthesis, at the designer’s option. A new algorithmic framework is presented, in which structural topology and actuator/sensor placement are simultaneously synthesized for adaptive performance. Significantly, this is not a traditional ad hoc method; sensor and actuator placement affect structural topology and vice versa. This is a continuation of our previously reported actuation-placement work [1–2], updated here to include the sensor placement co-synthesis and new tasks in addition to shape change. The methods used include genetic algorithms, graph searches for connectivity, and multiple load cases implemented with linear finite element analysis. Fundamental metrics for the inclusion of embedded components in a multifunctional compliant system are developed and investigated. The essential framework for the integration of controls with compliant mechanisms is established. Specifically, the concepts of controllability and observability, as redefined for compliant systems, are proven as a successful starting point for the design of multifunctional, adaptive systems. These concepts refer to the unique system response for each component (actuator or sensor) it contains. Results are presented for several problems, focusing on the application of shape-morphing aircraft structures. Through examples and design studies, the metrics and the methodology demonstrate that multiple, optimally-placed components indeed offer performance benefits for mechanical systems, in terms of multifunctional execution. Finally, the extension of controllability to address the problem of single-point multidegree-of-freedom manipulation is performed to show the generalized use of the new methodology in benefitting the design of compliant systems.

scholarly journals Mind-body training – a single-arm feasibility study of community-delivered Baduanjin training for frail older adults

2020 ◽  
Author(s):  
Xiao Liu ◽  
Jean Wei Ting Seah ◽  
Benedict Wei Jun Pang ◽  
Mary Ann Tsao ◽  
Falong Gu ◽  
...  
Keyword(s):  
Older Adults ◽  
Adverse Events ◽  
Training Program ◽  
Grip Strength ◽  
Feasibility Study ◽  
Fall Risk ◽  
Knee Extension ◽  
Frail Older Adults ◽  
Hand Grip ◽  
Frailty Score

Abstract Background Frailty is a common geriatric syndrome, characterized by reduced physiologic reserve and increased vulnerability to stressors, due to cumulative decline in multiple physiological systems. Our study examined the feasibility and effects of a community-delivered BDJ training program among pre-frail/frail community-dwelling older people in preparation for a randomised control implementation study.Methods Our study was a single arm feasibility study in community setting. Eleven participants (aged 77 ± 6 years; 2 frail, 9 prefrail at baseline) completed the program. Sixteen week group BDJ training co-designed and implemented by community-based providers in Singapore. Recruitment, attendance and adverse events were recorded throughout the training. A participants’ survey was also administered after the training program. Effects of the intervention on physical and functional outcomes (hand grip strength, knee extension strength, Time Up and Go (TUG), Physiological Profile Assessment (PPA), 30-second Sit-to-Stand test, 6-meter fast gait speed test), frailty outcomes (frailty score and status), and other outcomes (Maastricht Questionnaire (MQ), Fall Efficacy Scale (FES), Montreal Cognitive Assessment (MoCA), Geriatric Depression Scale (GDS), and EQ-5D-5L) were examined before and after the program.Results Of 31 older adults screened to be frail, 15 met inclusion criteria and 3 refused participation resulting in 12 older adults enrolled in the program. One participant was hospitalized (unrelated to BDJ training) and the other 11 completed the program with average overall attendance of 89%. Most (89%) of the 44 training sessions had attendance > 80%. The program received positive feedback with no training-related adverse events. Participants either reversed (n = 2) or maintained (n = 9) their frailty statuses. There were significant within-group post-training improvements in hand grip strength (p = 0.013), knee extension strength (p = 0.048), TUG (p = 0.018), MQ (p = 0.001), FES (p = 0.022), MoCA (p = 0.014), GDS (p = 0.028), EQ-5D-5L index score (p = 0.029). The reduction of frailty score and PPA fall risk score showed moderate-to-large effect size.Conclusions Community-delivered BDJ training program was safe and feasible for prefrail/frail older adults with the potential to improve physical and cognitive function, reduce fall risk, improve psychological well-being, and reverse frailty status.

Material Properties of Carbon-Infiltrated Carbon Nanotube-Templated Structures for Microfabrication of Compliant Mechanisms

2011 ◽  
Author(s):  
Walter C. Fazio ◽  
Jason M. Lund ◽  
Taylor S. Wood ◽  
Brian D. Jensen ◽  
Robert C. Davis ◽  
...  
Keyword(s):  
Layer Thickness ◽  
Polycrystalline Silicon ◽  
Fracture Strain ◽  
Compliant Mechanisms ◽  
Chemical Vapor ◽  
Iron Layer ◽  
Test Device ◽  
Fea Model ◽  
Single Piece ◽  
Fabrication Parameters

Carbon nanotubes can be grown vertically from a substrate to form dense forests hundreds of microns tall. The space between the nanotubes can then be filled with carbon using chemical vapor deposition to create solid structures. These infiltrated structures can be detached from the substrate and operated as single-piece MEMS. To facilitate the design of compliant microdevices using this process, we explored the influence of two fabrication parameters—iron layer thickness and infiltration time—on the material’s mechanical properties, using the fracture strain to judge suitability for compliance. We prepared samples of a simple meso-scale cantilever beam pattern at various levels of these parameters, applied vertical loads to the tips of the beams, and recorded the forces and deflections at brittle failure. These data were then used in conjunction with a nonlinear FEA model of the beams to determine Young’s modulus and fracture stress for each experimental setting. From these data the fracture strains were obtained. The highest fracture strain observed was 2.48%, which is approximately 3.5 times that of polycrystalline silicon. This was obtained using an iron layer thickness of 10 nm and an infiltration time of 30 minutes. We used a test device—a compliant gripper mechanism for holding mammalian egg cells—to demonstrate the use of this material in compliant MEMS design.

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