scholarly journals An Energy Approach to the Design of Single Degree of Freedom Gravity Balancers With Compliant Joints

2011 ◽  
Author(s):  
Boaz L. Rijff ◽  
Just L. Herder ◽  
Giuseppe Radaelli
Keyword(s):  
Energy Efficient ◽  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Compliant Joints ◽  
Constant Potential ◽  
Rigid Joints ◽  
Body Joints ◽  
First Time ◽  
Proof Of Principle

A gravity balancer is a mechanism that compensates the weight of a mass over a range of motion. When no friction is present, this gives an energy efficient mechanism and little effort is required to move an object. Conventional mechanisms have drawbacks due to the use of conventional rigid joints. Compliant joints do not have these disadvantages, can be made from fewer parts and can increase performance compared to rigid body joints. The goal of this paper is to develop a new method for the design of single degree of freedom gravity balancers where all the rigid joints are replaced with compliant joints. The method is based on connecting rigid links with compliant joints. With a constant potential energy as an objective, the method allows new gravity balancers to be designed. The second goal is to construct a demonstrator as proof of principle. It can be concluded that for the first time a gravity balancer has been constructed where all the rigid joints are replaced with compliant joints. The gravity balancer had a peak moment reduction of 93%. The presented method is extensible and allows others to understand and further develop gravity balancers with compliant joints for other applications.

Locomotion of One Degree of Freedom Worm Robots

2011 ◽  
Author(s):  
David Zarrouk ◽  
Moshe Shoham
Keyword(s):  
Energy Efficient ◽  
Power Efficiency ◽  
High Reliability ◽  
Degree Of Freedom ◽  
External Control ◽  
Medical Procedures ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Cyclic Function ◽  
Multiple Actuators

Worm-like robots have been widely designed for applications including maintenance of small pipes and medical procedures in biological vessels such as the lungs, intestines, urethra and blood vessels. The robots must be small, reliable, energy efficient and capable of carrying cargos such as cameras, biosensors, and drugs. Earthworm and inchworm robots have been traditionally designed with three or more cells and clamps and a corresponding number of actuators. The use of multiple actuators complicates the design, makes the system more cumbersome, reduces power efficiency and requires more control for coordination. In the present study, we analyze the worm locomotion, in terms of the distance between the cells and clamping modes, and model it as a cyclic function of the time. That is, the worm locomotion can be represented by a single degree of freedom. Consequently, multi-cells worm-like robots actuated by a single motor were designed. The robots employ a rotating screw-like shaft that mechanically coordinates the sequencing of the cell displacement as well as the clamping modes with no external control for each separate cell. This design allows for significant miniaturization and reduces complexity and cost of the system. Two prototypes of earthworm and inchworm robots for locomotion within 20mm and 70mm wide tubes were manufactured. The robots demonstrated high reliability and strong grip. They can crawl vertically while carrying a payload at a rate of few cm/s for the larger robots and roughly 1cm/s for the smaller ones. Furthermore, the low power consumption enables the robots to crawl wirelessly for hundreds of meters using standard off the shelf batteries.

Equivalent Linkages and Dead Center Positions of Planar Single-Degree-of-Freedom Complex Linkages

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Jun Wang ◽  
Kwun-Lon Ting ◽  
Daxing Zhao
Keyword(s):  
General Concept ◽  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
First Order ◽  
Single Degree ◽  
Kinematic Loops ◽  
The Dead ◽  
Planar Linkages ◽  
Four Bar Linkage ◽  
First Time

This paper proposes a simple and general approach for the identification of the dead center positions of single-degree-of-freedom (DOF) complex planar linkages. This approach is implemented through the first order equivalent four-bar linkages. The first order kinematic properties of a complex planar linkage can be represented by their instant centers. The condition for the occurrence of a dead center position of a single-DOF planar linkage can be designated as when the three passive instantaneous joints of any equivalent four-bar linkage become collinear. By this way, the condition for the complex linkage at the dead center positions can be easily obtained. The proposed method is a general concept and can be systematically applied to analyze the dead center positions for more complex single-DOF planar linkages regardless of the number of kinematic loops or the type of the kinematic pairs involved. The velocity method for the dead center analysis is also used to verify the results. The proposed method extends the application of equivalent linkage and is presented for the first time. It paves a novel and straightforward way to analyze the dead center positions for single-DOF complex planar linkages. Examples of some complex planar linkages are employed to illustrate this method in this paper.

Analysis and Design of a Two Degree of Freedom Hoeckens-Pantograph Leg Mechanism

2015 ◽  
Author(s):  
Dmitri Fedorov ◽  
Lionel Birglen
Keyword(s):  
Screw Theory ◽  
Degree Of Freedom ◽  
Performance Indices ◽  
Single Degree Of Freedom ◽  
Analysis And Design ◽  
Single Degree ◽  
Compliant Joints ◽  
Two Degree Of Freedom ◽  
Novel Design ◽  
Limited Motion

Hoeckens and Chebychev linkages have been widely discussed in the literature as design solutions to build single degree of freedom (DOF) leg mechanisms. Compared to fully actuated legs, often bio-inspired, they offer an unmatched simplicity. However, due to their limited motion capability, they can only be used when the traversed terrain is of limited difficulty. In order to alleviate this drawback, a novel design with a second DOF is proposed in this paper. The introduced mechanism is composed of a Hoeckens linkage augmented by a Pantograph for which the position of the pivot can be changed through an additional rotating link. Screw theory is used to determine the kinematic equations of the mechanism, its singular configurations, and its attainable workspace. Subsequently, an optimization of the geometric parameters is performed to maximize performance indices pertaining to the size of the mechanism’s workspace. Finally, possible use of compliant joints is discussed.

Kinematic comparison of single degree-of-freedom robotic gait trainers

2021 ◽  
Vol 159 ◽  
pp. 104258
Author(s):  
Jeonghwan Lee ◽  
Lailu Li ◽  
Sung Yul Shin ◽  
Ashish D. Deshpande ◽  
James Sulzer
Keyword(s):  
Degree Of Freedom ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Robotic Gait
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