Double-Helix Linear Actuators

2021 ◽  
pp. 1-40
Author(s):  
Andrew P. Sabelhaus ◽  
Kyle Zampaglione ◽  
Ellande Tang ◽  
Lee-Huang Chen ◽  
Adrian Agogino ◽  
...  
Keyword(s):  
Double Helix ◽  
Kinematic Model ◽  
Helix Angle ◽  
Robotic Systems ◽  
Force Transmission ◽  
Force Load ◽  
Transmission Properties ◽  
Tension And Compression ◽  
Linear Actuators ◽  
Fixed End

Abstract Many robotic systems require linear actuation with high forces, large displacements, and compact profiles. This article presents a series of mechanisms, termed double-helix linear actuators (DHLAs), designed for this purpose. By rotating the fixed end of a double-helix linear actuator, its helix angle changes, displacing at the free end. This article proposes two concepts for DHLA designs, differing in their supporting structure, and derives kinematic and geometric models for both. Prototypes of each concept are presented, and for the more promising “continuous-rails” design, hardware tests are conducted that validate the actuator's kinematic model and characterize its force transmission properties. The final prototypes can exert both tension and compression forces, can displace up to 75% of their total length, and show consistent trends for torque vs. force load. These designs have the potential to overcome the force and displacement limitations of other linear actuators while simultaneously reducing size and weight.

A multi-configuration kinematic model for active drive/steer four-wheel robot structures

Robotica ◽  
2015 ◽  
Vol 34 (10) ◽  
pp. 2309-2329 ◽  
Author(s):  
Edgar A. Martínez-García ◽  
Erik Lerín-García ◽  
Rafael Torres-Córdoba
Keyword(s):  
Degrees Of Freedom ◽  
Rotation Axis ◽  
Contact Point ◽  
Linear Equations ◽  
Kinematic Model ◽  
Robotic Systems ◽  
Control Law ◽  
Special Design ◽  
Wheel Drive ◽  
Four Wheel Drive

SUMMARYIn this study, a general kinematic control law for automatic multi-configuration of four-wheel active drive/steer robots is proposed. This work presents models of four-wheel drive and steer (4WD4S) robotic systems with all-wheel active drive and steer simultaneously. This kinematic model comprises 12 degrees of freedom (DOFs) in a special design of a mechanical structure for each wheel. The control variables are wheel yaw, wheel roll, and suspension pitch by active/passive damper systems. The pitch angle implies that a wheel's contact point translates its position over time collinear with the robot's lateral sides. The formulation proposed involves the inference of the virtual z-turn axis (robot's body rotation axis) to be used in the control of the robot's posture by at least two acceleration measurements local to the robot's body. The z-turn axis is deduced through a set of linear equations in which the number of equations is equal to the number of acceleration measurements. This research provides two main models for stability conditions. Finally, the results are sustained by different numerical simulations that validate the system with different locomotion configurations.

scholarly journals Numerical analysis and mechanic theoretical derivations for optimizing the V-thread profiles in dental implant system

2021 ◽  
Author(s):  
Yongqing Cai
Keyword(s):  
Dental Implant ◽  
Simulation Analysis ◽  
Tensile Force ◽  
Helix Angle ◽  
Apex Angle ◽  
Force Transmission ◽  
Bone Implant ◽  
Thread Pitch ◽  
Thread Profile ◽  
Implant System

Abstract Background The thread design of the dental implant is an important feature to be considered in the optimization of the dental implant structure. The present study aimed to investigate the effects of V-thread profile design dimensions, including depth, width, pitch, thread helix angle and triangle thread apex angle on the mechanical characteristics of the bone-implant interface. A total of 588 V-thread implant system models were constructed to investigate the effects of the dimension parameters on the stress distribution generated around the bone-implant interface under vertical occlusal force. Furthermore, the force transfer at the bone-implant interface was analyzed theoretically to analyze the force transmission mechanism at bone-implant for an optimized V-thread profile in the implants. Results The optimum thread pitch ranged from 1.0 mm to 1.2 mm, when the triangle thread depth and width was 0.1 mm. The theoretically derived results showed that, with the same implant diameter, when the thread depth was 0.1 mm and the thread pitch was 0.9 mm, the optimal thread width was found to be 0.1026 mm. This derived result was consistent with the simulation analysis results. Conclusions To design the optimal V-shape threads, the implant and thread dimensions, such as the implant diameter, thread pitch, thread width, thread helix angle and triangle thread apex angle should be comprehensively considered. The optimal designed thread in this study can dissipate the chewing load, as a result of the appropriate ratio of tensile force and shear force on bone-implant interface. The optimum designed thread profile can take full advantage of the carrying capacity of the tensile and shear of the bone, thereby bearing a high chewing load.

THE SEQUENCE-DEPENDENT TRANSMISSION PROPERTIES THROUGH DOUBLE HELIX DNA MOLECULES

2008 ◽  
Vol 22 (18) ◽  
pp. 1767-1776
Author(s):  
RUI-XIN DONG ◽  
XUN-LING YAN ◽  
BING YANG
Keyword(s):  
Charge Transport ◽  
Double Helix ◽  
Transmission Spectra ◽  
Dna Molecules ◽  
Transmission Characteristics ◽  
Periodic Sequences ◽  
Transmission Properties ◽  
Dna Molecule ◽  
Sequence Dependent

In this paper, a double helix model of charge transport in a DNA molecule is presented, and the transmission spectra and I–V curves of four kinds of periodic sequences DNA are obtained. The results show that the transmission characteristics of DNA are not only related to the longitudinal transport but also to the transverse transport of the molecule. The more the composition of bases, the bigger the percent of θ-direction, and the conductive ability reduces. For a different sequence with same composition, the less the number of consecutive appearance of the same base is, the lower the conductive ability.

Cavatappi artificial muscles from drawing, twisting, and coiling polymer tubes

2021 ◽  
Vol 6 (53) ◽  
pp. eabd5383
Author(s):  
Diego R. Higueras-Ruiz ◽  
Michael W. Shafer ◽  
Heidi P. Feigenbaum
Keyword(s):  
Robotic Systems ◽  
Practical Implementation ◽  
Artificial Muscles ◽  
Specific Work ◽  
Bandwidth Efficiency ◽  
Initial Length ◽  
Thermally Activated ◽  
Linear Actuators ◽  
Twisted Tubes ◽  
Polymer Tubes

Compliant, biomimetic actuation technologies that are both efficient and powerful are necessary for robotic systems that may one day interact, augment, and potentially integrate with humans. To this end, we introduce a fluid-driven muscle-like actuator fabricated from inexpensive polymer tubes. The actuation results from a specific processing of the tubes. First, the tubes are drawn, which enhances the anisotropy in their microstructure. Then, the tubes are twisted, and these twisted tubes can be used as a torsional actuator. Last, the twisted tubes are helically coiled into linear actuators. We call these linear actuators cavatappi artificial muscles based on their resemblance to the Italian pasta. After drawing and twisting, hydraulic or pneumatic pressure applied inside the tube results in localized untwisting of the helical microstructure. This untwisting manifests as a contraction of the helical pitch for the coiled configuration. Given the hydraulic or pneumatic activation source, these devices have the potential to substantially outperform similar thermally activated actuation technologies regarding actuation bandwidth, efficiency, modeling and controllability, and practical implementation. In this work, we show that cavatappi contracts more than 50% of its initial length and exhibits mechanical contractile efficiencies near 45%. We also demonstrate that cavatappi artificial muscles can exhibit a maximum specific work and power of 0.38 kilojoules per kilogram and 1.42 kilowatts per kilogram, respectively. Continued development of this technology will likely lead to even higher performance in the future.

Compliant Transmissions: Design Methods and Applications

2000 ◽  
Author(s):  
Sridhar Kota
Keyword(s):  
Elastic Deformation ◽  
Transmission Function ◽  
Design Methods ◽  
Systematic Design ◽  
Force Transmission ◽  
Design Procedures ◽  
Thermal Actuators ◽  
Single Piece ◽  
Linear Actuators ◽  
Flexural Hinges

Abstract The paper provides an overview of systematic design procedures and applications of compliant transmissions, which rely on elastic deformation to achieve, intended motion/force transmission function. The mechanisms described in this paper have compliance distributed throughout the structure without employing flexural hinges. Stroke-amplification mechanisms integrated with electrostatic linear actuators and thermal actuators in MEMS domain, and piezoceramic actuators ate illustrated as some of the applications of single-piece compliant transmissions. Additionally the concept of distributed compliance is illustrated with applications to shape-changing structures such as adaptive airfoils.

DESIGN AND ANALYSIS OF A NEW SYMMETRICAL LINEAR ACTUATOR FOR HYDRAULIC AND PNEUMATIC SYSTEMS

1999 ◽  
Vol 23 (3-4) ◽  
pp. 377-396 ◽  
Author(s):  
S. Habibi ◽  
A.A. Goldenberg
Keyword(s):  
Flow Characteristics ◽  
Dynamic Effect ◽  
Input Force ◽  
Symmetrical Design ◽  
Command Input ◽  
Linear Actuators ◽  
Fixed End ◽  
Actuation Systems ◽  
Force Relationship ◽  
Better Than

In this paper, the performance of hydraulic actuation systems is analyzed and, it is observed that the performance of symmetrical (rotary) actuators is significantly better than their linear asymmetrical counterpart. The deficiency of linear actuators, resulting from their asymmetry, manifests itself as an undesirable dynamic effect related to the pressure characteristics of the actuator chambers. Subsequently, a new symmetrical design for linear actuators is proposed. In this design, the active areas of the two pressure chambers are made equal without the need for a dead-space on the fixed end of the piston as required by commercial double rod pistons. The paper discusses the benefits of this new design and demonstrates the advantages of its flow characteristics and its command input/force relationship. The theoretical observations are supported by experiments conducted on a large hydraulic robot. The Workmaster, formerly manufactured by Thorn EMI Robotics.

scholarly journals Force transmission analysis of surface coating materials for multi-fingered robotic grippers

2021 ◽  
Vol 7 ◽  
pp. e401
Author(s):  
Gökhan Erdemir
Keyword(s):  
Essential Element ◽  
Cost Effective ◽  
Industrial Applications ◽  
Robotic Systems ◽  
Chemical Compositions ◽  
Force Transmission ◽  
Coating Materials ◽  
Robot Gripper ◽  
Under Construction ◽  
Environmental Savings

Robotic systems are generally used for grasping, carrying, holding, and many similar operations, typically in industrial applications. One of the most important components of robotic systems is robot grippers for the aforementioned operations, which are not only mission-critical but also represent a significant operational cost due to the time and expense associated with replacement. Grasping operations require sensitive and dexterous manipulation ability. As a consequence, tactile materials and sensors are an essential element in effective robot grippers; however, to date, little effort has been invested in the optimization of these systems. This study has set out to develop inexpensive, easily replaced pads, testing two different chemical compositions that are used to produce a tactile material for robot grippers, with the objective of generating cost, time, and environmental savings. Each tactile material produced has its specific individual dimension and weight. First, each of the materials under construction was tested under different constant pressures, and its characteristics were analyzed. Second, each tactile material was mounted on a two-fingered robot gripper and its characteristics. Material characteristics were tested and analyzed as regards their ability to grasp different sizes and types of objects using the two-fingered robot gripper. Based on the analysis of the results the most sensitive and cost-effective material for industrial type multi-fingered grippers was identified.

scholarly journals Synthesis of the Inverse Kinematic Model of Non-Redundant Open-Chain Robotic Systems Using Groebner Basis Theory

2020 ◽  
Vol 10 (8) ◽  
pp. 2781
Author(s):  
José Guzmán-Giménez ◽  
Ángel Valera Fernández ◽  
Vicente Mata Amela ◽  
Miguel Ángel Díaz-Rodríguez
Keyword(s):  
Control System ◽  
Kinematic Model ◽  
Lexicographic Order ◽  
Inverse Kinematic ◽  
Robotic Systems ◽  
Walking Robots ◽  
Groebner Basis ◽  
Open Chain ◽  
Monomial Order ◽  
Kinematic Models

One of the most important elements of a robot’s control system is its Inverse Kinematic Model (IKM), which calculates the position and velocity references required by the robot’s actuators to follow a trajectory. The methods that are commonly used to synthesize the IKM of open-chain robotic systems strongly depend on the geometry of the analyzed robot. Those methods are not systematic procedures that could be applied equally in all possible cases. This project presents the development of a systematic procedure to synthesize the IKM of non-redundant open-chain robotic systems using Groebner Basis theory, which does not depend on the geometry of the robot’s structure. The inputs to the developed procedure are the robot’s Denavit–Hartenberg parameters, while the output is the IKM, ready to be used in the robot’s control system or in a simulation of its behavior. The Groebner Basis calculation is done in a two-step process, first computing a basis with Faugère’s F4 algorithm and a grevlex monomial order, and later changing the basis with the FGLM algorithm to the desired lexicographic order. This procedure’s performance was proved calculating the IKM of a PUMA manipulator and a walking hexapod robot. The errors in the computed references of both IKMs were absolutely negligible in their corresponding workspaces, and their computation times were comparable to those required by the kinematic models calculated by traditional methods. The developed procedure can be applied to all Cartesian robotic systems, SCARA robots, all the non-redundant robotic manipulators that satisfy the in-line wrist condition, and any non-redundant open-chain robot whose IKM should only solve the positioning problem, such as multi-legged walking robots.

GENERALIZED RECONFIGURABLE 6 - JOINT ROBOT MODELING

2006 ◽  
Vol 30 (4) ◽  
pp. 533-565 ◽  
Author(s):  
A. M. Djuric ◽  
W. H. ElMaraghy
Keyword(s):  
Manufacturing Systems ◽  
Kinematic Model ◽  
Geometric Approach ◽  
Inverse Kinematic ◽  
Robotic Systems ◽  
Reconfigurable Manufacturing ◽  
Unified Approach ◽  
Inverse Kinematic Problem ◽  
Computer Controlled ◽  
Robot Modeling

Automated model generation and solution for motion planning and re-planning of robotic systems will play an important role in the future reconfigurable manufacturing systems. Solving the inverse kinematic problem has always been the key issue for computer-controlled robots. Considering the large amount of similarities that exist among the industrial 6R robotic systems, this work classifies them into two main types (Puma-type and Fanuc-type) and then provides a unified geometric solution based on a unified kinematic structure called Generic Puma-Fanuc (GPF) model. A widespread study of different kinematic groups originating from eleven robot manufacturers made it possible to develop the GPF model that can be reconfigured according to the D-H rules (Denavit, and Hartenberg1). A graphical interface by which the robot kinematic model is represented and the D-H parameters are auto-generated for use in solving the inverse kinematic problem. A generic solution module called Unified Kinematic Modeler and Solver (UKMS) implements the geometric approach for solving the inverse kinematic problem. The outcomes are then employed for robot control. Numerical examples are presented for exploring the solution capabilities of our unified approach.

The Relation Between Helical Spring Compliances With Free and Fixed End Rotations

2011 ◽  
Vol 78 (6) ◽  
Author(s):  
S. J. Burns
Keyword(s):  
Poisson’S Ratio ◽  
Substantial Reduction ◽  
Beam Theory ◽  
Helix Angle ◽  
Poisson's Ratio ◽  
Helical Spring ◽  
Free Rotation ◽  
Spring Wire ◽  
Dimensionless Ratio ◽  
Fixed End

A helical spring that is constrained to no rotation has a compliance that is typically more than 95% of the compliance of springs constrained to free rotation when restricted to symmetric wires made from materials with Poisson’s ratio between 0 and 1/2. It is shown that the shape of the spring wire can be designed so the spring will not twist when it is extended nor extend when it is twisted. The constrained spring versus a freely rotating spring with the helix angle equal to π/4 has the largest reduction in compliance in the limits of beam theory. Spring compliances for torsion and extension with quite complex helical spring geometries are found to be related by a dimensionless ratio of compliances in a very simple equation that only depends on Poisson’s ratio and the helical, spring angle, ψ. Springs made from materials with negative Poisson’s ratio, however, can have a very substantial reduction in compliance; the no rotation compliance is zero when Poisson’s ratio is −1. There are large changes in spring compliances for springs with geometric coils that are elongated rectangles or flattened ellipses.

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