A Constant Force Generation Mechanism

1985 ◽  
Vol 107 (4) ◽  
pp. 508-512 ◽  
Author(s):  
R. H. Nathan
Keyword(s):  
Force Feedback ◽  
Kinematic Chain ◽  
Geometric Parameters ◽  
Generation Mechanism ◽  
Force Generation ◽  
Constant Force ◽  
Static Balancing ◽  
Full Rotation ◽  
Output Load ◽  
Force Generator

A mechanism is described that generates a constant, unidirectional force at any given point on a hinged lever, for all positions of the lever within a full rotation. It is shown how one of several selected geometric parameters of the mechanism may be preadjusted automatically to equilibrate the system, using force feedback from the output load. The constant force generator is introduced into a parallelogram four-bar mechanism, and it is shown that this system may replace links of a kinematic chain to achieve static balancing of the chain plus any additional masses or vertical forces.

Analytical Modelling of Rolamite Mechanism Made of Shape Memory Alloy for Constant Force Actuators

2015 ◽  
Author(s):  
Andrea Spaggiari ◽  
Eugenio Dragoni
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Metal Strip ◽  
Force Generation ◽  
Constant Force ◽  
Low Friction ◽  
Actuation Force ◽  
Long Stroke ◽  
Force Generator ◽  
Roll Back

This paper analyses the Rolamite architecture exploiting shape memory alloys as power element to obtain a solid state actuator. The Rolamite mechanism was discovered in the late sixties, initially as precision and low friction linear bearing. The most common Rolamite configuration consists of a flexible thin metal strip and two rollers mounted between two fixed parallel guide surfaces. The system can roll back and forth without slipping guided by the plates along its so called sensing axis. The system presents another relevant advantage in addition to low friction coefficient, which is the possibility to provide force generation in a quite simple way. In the original literature works the force was provided thanks to cutouts of various shape in the strip, though this method does not allow the Rolamite to be considered a proper actuator, but only a force generator. In this paper we developed the idea of exploiting the shape memory alloy as Rolamite power element and therefore to use the shape memory effect to change the elastic properties of the strip and to provide the actuation force. The mechanical analyses and the equations where the martensite-austenite transition is modelled in a simplified way, show that this application is feasible, mainly thanks to the initial precurvature of the SMA strip. The discussion of the results highlights some important merits of this architecture such as long stroke, constant force and compactness.

scholarly journals Limitations of Constant-Force-Feedback Experiments

2012 ◽  
Vol 103 (7) ◽  
pp. 1490-1499 ◽  
Author(s):  
Phillip J. Elms ◽  
John D. Chodera ◽  
Carlos J. Bustamante ◽  
Susan Marqusee
Keyword(s):  
Force Feedback ◽  
Constant Force

Force Generation Mechanism of a Wing Model in Drosophila Voluntary Take-Off

2011 ◽  
Author(s):  
Q. Zhang ◽  
R. H. Wen ◽  
H. Liu ◽  
Jiachun Li ◽  
Song Fu
Keyword(s):  
Generation Mechanism ◽  
Force Generation ◽  
Wing Model

Design and performance evaluation of a 3-axis force sensor for MIS palpation

Sensor Review ◽  
2015 ◽  
Vol 35 (2) ◽  
pp. 219-228 ◽  
Author(s):  
Kun Li ◽  
Bo Pan ◽  
Juncheng Zhan ◽  
Wenpeng Gao ◽  
Yili Fu ◽  
...  
Keyword(s):  
Open Surgery ◽  
Force Feedback ◽  
Force Measurement ◽  
Force Sensor ◽  
Optimization Method ◽  
Geometric Parameters ◽  
Characteristic Matrix ◽  
Content Type ◽  
Sensor Structure ◽  
External Loads

Purpose – This paper aims to develop a novel miniature 3-axis force sensor which can detect the interaction forces during tissue palpation in MIS (minimally invasive surgery). MIS offers many significant merits compared with traditional open surgery, the wound to the patients and the postoperative pains are alleviated and reduced dramatically. However, the inherent drawback due to lack of force feedback still exists while conducting some operation procedures. For example, tissue palpation performed easily during open surgery could not be realized in an MIS manner. Design/methodology/approach – The force sensor is based on the resistive-based sensing method that utilizes strain gauges to measure the strain when the external loads are acting on the tip of the sensor. A novel flexible tripod structure with bending and compression deformations is designed to discriminate the magnitudes and directions of the three orthogonal force components. A linear characteristic matrix is derived to disclose the relationship between the sensitivity and the geometric parameters of the structure, and a straightforward geometric parameterized optimization method considering the sensitivity isotropy is proposed to provide the sensor structure with high sensitivity and adequate stiffness. Findings – The sensor prototype can perform force measurement with sensing ranges of ± 3.0 N in axial direction and ± 1.5 N in radial direction, and the resolutions are 5 per cent and 1 per cent, respectively. It is concluded that this force sensor is compatible with MIS instruments and the ex-vivo experiment shows that the sensor can be used to perform tissue palpation during MIS procedures. Originality/value – This paper is intended to address the significant role of force sensing and force feedback during MIS operations, and presents a new application of the resistive-based sensing method in MIS. A tripod structure is designed and a straightforward optimization method considering the sensitivity isotropy of the sensor is proposed to determine geometric parameters suited for the given external loads.

Analytical modelling of Rolamite mechanism made of shape-memory alloy for constant force actuators

2016 ◽  
Vol 28 (16) ◽  
pp. 2208-2221 ◽  
Author(s):  
Andrea Spaggiari ◽  
Eugenio Dragoni
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Mechanical Analysis ◽  
Metal Strip ◽  
Constant Force ◽  
Low Friction ◽  
Actuation Force ◽  
Long Stroke ◽  
Force Generator ◽  
Roll Back

This article analyses the Rolamite architecture exploiting shape-memory alloys as power element to obtain a solid-state actuator. The Rolamite mechanism was discovered in the late 1960s, initially as precision and low friction linear bearing. The most common Rolamite configuration consists of a flexible thin metal strip and two rollers mounted between two fixed parallel guide surfaces. The system can roll back and forth without slipping guided by the plates along its so-called sensing axis. The system presents another relevant advantage in addition to low friction coefficient, which is the possibility to provide force generation in a quite simple way. In the original literature works, the force was provided, thanks to cut-outs of various shapes in the strip, although this method does not allow the Rolamite to be considered a proper actuator, but only a force generator. In this article, we developed the idea of exploiting the shape-memory alloy as Rolamite power element, and therefore, to use the shape-memory effect to change the elastic properties of the strip and to provide the actuation force. The mechanical analysis, where the martensite–austenite transition is modelled in a simplified way, shows that this application is feasible, mainly thanks to the initial precurvature of the shape-memory alloy strip. The discussion of the results highlights some important merits of this architecture such as long stroke, constant force and compactness.

scholarly journals Static Balancing of Robot Mechanisms and Manipulation Devices

2018 ◽  
Vol 68 (2) ◽  
pp. 77-90
Author(s):  
Stefan Segla
Keyword(s):  
Objective Function ◽  
Multibody Dynamics ◽  
Optimization Problem ◽  
Energy Savings ◽  
Driving Forces ◽  
Optimal Designs ◽  
Constant Force ◽  
Static Balancing ◽  
Design Variables ◽  
Gravity Load

AbstractThe paper deals with static balancing of various kinds of mechanisms and manipulation devices using spring balancing mechanisms. In case of parallelogram robots and manipulation mechanisms a spring balancing mechanism exerting a constant force is used. Problems of static balancing of variable payloads are also presented and investigated in the paper. Static balancing is formulated as an optimization problem with the objective function expressing minimization of the forces acting in the driving joints. As design variables geometrical variables and spring stiffnesses and their unloaded lengths are used. Optimization Toolbox for Use with Matlab and GOOD (Generator Of Optimal Designs) are used to solve the static balancing problems. The optimized mechanisms are evaluated by using multibody dynamics programs taking into account friction effects in mechanism joints. The results of static balancing optimization show essential reduction of the gravity load in drive joints and consequently driving forces with important energy savings.

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