Machines

4053 KiB

Open AccessArticle

One-Dimensional Haptic Rendering Using Audio Speaker with Displacement Determined by Inductance

by Avin Khera, Randy Lee, Avi Marcovici, Zhixuan Yu, Roberta Klatzky, Mel Siegel, Sanjeev G. Shroff and George Stetten

Machines 2016, 4(1), 9; https://doi.org/10.3390/machines4010009 - 21 Mar 2016

Cited by 1 | Viewed by 5704

Abstract

We report overall design considerations and preliminary results for a new haptic rendering device based on an audio loudspeaker. Our application models tissue properties during microsurgery. For example, the device could respond to the tip of a tool by simulating a particular tissue, [...] Read more.

We report overall design considerations and preliminary results for a new haptic rendering device based on an audio loudspeaker. Our application models tissue properties during microsurgery. For example, the device could respond to the tip of a tool by simulating a particular tissue, displaying a desired compressibility and viscosity, giving way as the tissue is disrupted, or exhibiting independent motion, such as that caused by pulsations in blood pressure. Although limited to one degree of freedom and with a relatively small range of displacement compared to other available haptic rendering devices, our design exhibits high bandwidth, low friction, low hysteresis, and low mass. These features are consistent with modeling interactions with delicate tissues during microsurgery. In addition, our haptic rendering device is designed to be simple and inexpensive to manufacture, in part through an innovative method of measuring displacement by existing variations in the speaker’s inductance as the voice coil moves over the permanent magnet. Low latency and jitter are achieved by running the real-time simulation models on a dedicated microprocessor, while maintaining bidirectional communication with a standard laptop computer for user controls and data logging. Full article

(This article belongs to the Special Issue Mechanisms and Machinery for Haptic Interaction and Rendering)

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5374 KiB

Open AccessArticle

Design and Analysis of a Haptic Device Design for Large and Fast Movements

by Alastair Barrow and William Harwin

Machines 2016, 4(1), 8; https://doi.org/10.3390/machines4010008 - 10 Mar 2016

Cited by 7 | Viewed by 5204

Abstract

Haptic devices tend to be kept small as it is easier to achieve a large change of stiffness with a low associated apparent mass. If large movements are required there is a usually a reduction in the quality of the haptic sensations which [...] Read more.

Haptic devices tend to be kept small as it is easier to achieve a large change of stiffness with a low associated apparent mass. If large movements are required there is a usually a reduction in the quality of the haptic sensations which can be displayed. The typical measure of haptic device performance is impedance-width (z-width) but this does not account for actuator saturation, usable workspace or the ability to do rapid movements. This paper presents the analysis and evaluation of a haptic device design, utilizing a variant of redundant kinematics, sometimes referred to as a macro-micro configuration, intended to allow large and fast movements without loss of impedance-width. A brief mathematical analysis of the design constraints is given and a prototype system is described where the effects of different elements of the control scheme can be examined to better understand the potential benefits and trade-offs in the design. Finally, the performance of the system is evaluated using a Fitts’ Law test and found to compare favourably with similar evaluations of smaller workspace devices. Full article

(This article belongs to the Special Issue Mechanisms and Machinery for Haptic Interaction and Rendering)

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1244 KiB

Open AccessArticle

Algorithms for Optimal Model Distributions in Adaptive Switching Control Schemes

by Debarghya Ghosh and Simone Baldi

Machines 2016, 4(1), 7; https://doi.org/10.3390/machines4010007 - 04 Mar 2016

Cited by 3 | Viewed by 3671

Abstract

Several multiple model adaptive control architectures have been proposed in the literature. Despite many advances in theory, the crucial question of how to synthesize the pairs model/controller in a structurally optimal way is to a large extent not addressed. In particular, it is [...] Read more.

Several multiple model adaptive control architectures have been proposed in the literature. Despite many advances in theory, the crucial question of how to synthesize the pairs model/controller in a structurally optimal way is to a large extent not addressed. In particular, it is not clear how to place the pairs model/controller is such a way that the properties of the switching algorithm (e.g., number of switches, learning transient, final performance) are optimal with respect to some criteria. In this work, we focus on the so-called multi-model unfalsified adaptive supervisory switching control (MUASSC) scheme; we define a suitable structural optimality criterion and develop algorithms for synthesizing the pairs model/controller in such a way that they are optimal with respect to the structural optimality criterion we defined. The peculiarity of the proposed optimality criterion and algorithms is that the optimization is carried out so as to optimize the entire behavior of the adaptive algorithm, i.e., both the learning transient and the steady-state response. A comparison is made with respect to the model distribution of the robust multiple model adaptive control (RMMAC), where the optimization considers only the steady-state ideal response and neglects any learning transient. Full article

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1988 KiB

Open AccessArticle

Bidirectional Haptic Communication: Application to the Teaching and Improvement of Handwriting Capabilities

by Nicolò Pedemonte, Thierry Laliberté and Clément Gosselin

Machines 2016, 4(1), 6; https://doi.org/10.3390/machines4010006 - 15 Feb 2016

Cited by 9 | Viewed by 4212

Abstract

The objective of this work is to study the relevance of haptic feedback in remote communication between people. The application is handwriting. A haptic device designed to help people to improve their writing skills is presented. Two experimental sessions are then proposed to [...] Read more.

The objective of this work is to study the relevance of haptic feedback in remote communication between people. The application is handwriting. A haptic device designed to help people to improve their writing skills is presented. Two experimental sessions are then proposed to a group of people. In the first test, two subjects communicate through a bilateral system by means of a haptic feedback to accomplish the task. Secondly, a blank test is performed. The results of the two tests are compared and analyzed in order to evaluate the importance of the haptic feedback in the context of collaboration between two people. Full article

(This article belongs to the Special Issue Mechanisms and Machinery for Haptic Interaction and Rendering)

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3646 KiB

Open AccessArticle

Joint Mechanism That Mimics Elastic Characteristics in Human Running

by Takuya Otani, Kenji Hashimoto, Takaya Isomichi, Masanori Sakaguchi, Yasuo Kawakami, Hun-Ok Lim and Atsuo Takanishi

Machines 2016, 4(1), 5; https://doi.org/10.3390/machines4010005 - 25 Jan 2016

Cited by 13 | Viewed by 8053

Abstract

Analysis of human running has revealed that the motion of the human leg can be modeled by a compression spring because the joints of the leg behave like a torsion spring in the stance phase. In this paper, we describe the development of [...] Read more.

Analysis of human running has revealed that the motion of the human leg can be modeled by a compression spring because the joints of the leg behave like a torsion spring in the stance phase. In this paper, we describe the development of a joint mechanism that mimics the elastic characteristics of the joints of the stance leg. The knee was equipped with a mechanism comprising two laminated leaf springs made of carbon fiber-reinforced plastic for adjusting the joint stiffness and a worm gear in order to achieve active movement. Using this mechanism, we were able to achieve joint stiffness mimicking that of a human knee joint that can be adjusted by varying the effective length of one of the laminated leaf springs. The equation proposed for calculating the joint stiffness considers the difference between the position of the fixed point of the leaf spring and the position of the rotational center of the joint. We evaluated the performance of the laminated leaf spring and the effectiveness of the proposed equation for joint stiffness. We were able to make a bipedal robot run with one leg using pelvic oscillation for storing energy produced by the resonance related to leg elasticity. Full article

(This article belongs to the Special Issue Mechanical Designs for Humanoids Robots: Problems and Solutions)

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2936 KiB

Open AccessArticle

Dynamic Contact between a Wire Rope and a Pulley Using Absolute Nodal Coordinate Formulation

by Shoichiro Takehara, Masaya Kawarada and Kazunori Hase

Machines 2016, 4(1), 4; https://doi.org/10.3390/machines4010004 - 21 Jan 2016

Cited by 12 | Viewed by 6496

Abstract

Wire rope and pulley devices are used in various machines. To use these machines more safely, it is necessary to analyze the behavior of the contact between them. In this study, we represent a wire rope by a numerical model of a flexible [...] Read more.

Wire rope and pulley devices are used in various machines. To use these machines more safely, it is necessary to analyze the behavior of the contact between them. In this study, we represent a wire rope by a numerical model of a flexible body. This flexible body is expressed in the absolute nodal coordinate formulation (ANCF), and the model includes the normal contact force and the frictional force between the wire rope and the pulley. The normal contact force is expressed by spring-damper elements, and the frictional force is expressed by the Quinn method. The advantage of the Quinn method is that it reduces the numerical problems associated with the discontinuities in Coulomb friction at zero velocity. By using the numerical model, simulations are performed, and the validity of this model is shown by comparing its results with those of an experiment. Through numerical simulations, we confirm the proposed model for the contact between the wire rope and the pulley. We confirmed that the behavior of the wire rope changes when both the bending elastic modulus of the wire rope and the mass added to each end of the wire rope are changed. Full article

(This article belongs to the Special Issue Advance in Multibody System Dynamics)

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5008 KiB

Open AccessArticle

High-Efficiency Solar-Powered 3-D Printers for Sustainable Development

by Jephias Gwamuri, Dhiogo Franco, Khalid Y. Khan, Lucia Gauchia and Joshua M. Pearce

Machines 2016, 4(1), 3; https://doi.org/10.3390/machines4010003 - 15 Jan 2016

Cited by 29 | Viewed by 12973

Abstract

The release of the open source 3-D printer known as the RepRap (a self-Replicating Rapid prototyper) resulted in the potential for distributed manufacturing of products for significantly lower costs than conventional manufacturing. This development, coupled with open source-appropriate technology (OSAT), [...] Read more.

The release of the open source 3-D printer known as the RepRap (a self-Replicating Rapid prototyper) resulted in the potential for distributed manufacturing of products for significantly lower costs than conventional manufacturing. This development, coupled with open source-appropriate technology (OSAT), has enabled the opportunity for 3-D printers to be used for sustainable development. In this context, OSAT provides the opportunity to modify and improve the physical designs of their printers and desired digitally-shared objects. However, these 3-D printers require electricity while more than a billion people still lack electricity. To enable the utilization of RepRaps in off-grid communities, solar photovoltaic (PV)-powered mobile systems have been developed, but recent improvements in novel delta-style 3-D printer designs allows for reduced costs and improved performance. This study builds on these innovations to develop and experimentally validate a mobile solar-PV-powered delta 3-D printer system. It is designed to run the RepRap 3-D printer regardless of solar flux. The electrical system design is tested outdoors for operating conditions: (1) PV charging battery and running 3-D printer; (2) printing under low insolation; (3) battery powering the 3-D printer alone; (4) PV charging the battery only; and (5) battery fully charged with PV-powered 3-D printing. The results show the system performed as required under all conditions providing feasibility for adoption in off-grid rural communities. 3-D printers powered by affordable mobile PV solar systems have a great potential to reduce poverty through employment creation, as well as ensuring a constant supply of scarce products for isolated communities. Full article

(This article belongs to the Special Issue Feature Papers)

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6243 KiB

Open AccessFeature PaperArticle

Concentrated Windings in Compact Permanent Magnet Synchronous Generators: Managing Efficiency

by Olivier Barré and Bellemain Napame

Machines 2016, 4(1), 2; https://doi.org/10.3390/machines4010002 - 05 Jan 2016

Cited by 9 | Viewed by 22744

Abstract

In electric power generation, customers want generators with high efficiency. Nowadays, modern turbo-generators have efficiencies greater than 98%. Although this amount should not be obtained for all kind of machines, efficiency will remain one of the main parameters for customer choice. Efficiency is [...] Read more.

In electric power generation, customers want generators with high efficiency. Nowadays, modern turbo-generators have efficiencies greater than 98%. Although this amount should not be obtained for all kind of machines, efficiency will remain one of the main parameters for customer choice. Efficiency is also linked to the life of the machine: the higher the efficiency is, the longer the machine’s lifetime. During the past decade, new forms of energy production have appeared and generators have been developed to fit well into this market. For example, wind generators evolved towards permanent magnet generators having high polarity and running at low speed. Nevertheless, their structure is not fixed. An industrial company has built a prototype of such a generator which uses fractional-slot concentrated-windings (FSCW). This kind of winding is not the structure used by default in such electrical machines. Another field of interest is in autonomous generators which can be used on boats. Even if everyone has in mind large merchant ships, we must not forget smaller ships, such as fishing boats and short-range cruise ships, which spend the most of their time near the coast. This kind of ship does nothave large areas for installing the electric generation or the electric propulsion. It is the reason why, in this article, we focus on the efficiency of machines using fractional-slot concentrated-windings. In many publications which compare performances between distributed and concentrated windings, the result is almost the same. The efficiency of FSCW is not as high as the efficiency associated to the machines which are using distributed windings. Design methods have to be redrawn to integrate, as soon as possible, the loss mitigation in order to provide the best efficiency in power conversion. The following discussion, step by step, introduces the loss mitigation in every part of a machine using FSCW. To close the discussion, a design is produced and it appears that efficiency can be enhanced with suitable design methods. Full article

(This article belongs to the Special Issue Feature Papers)

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4457 KiB

Open AccessArticle

A Novel Design for Adjustable Stiffness Artificial Tendon for the Ankle Joint of a Bipedal Robot: Modeling & Simulation

by Aiman Omer, Reza Ghorbani, Kenji Hashimoto, Hun-ok Lim and Atsuo Takanishi

Machines 2016, 4(1), 1; https://doi.org/10.3390/machines4010001 - 26 Dec 2015

Cited by 8 | Viewed by 7151

Abstract

Bipedal humanoid robots are expected to play a major role in the future. Performing bipedal locomotion requires high energy due to the high torque that needs to be provided by its legs’ joints. Taking the WABIAN-2R as an example, it uses harmonic gears [...] Read more.

Bipedal humanoid robots are expected to play a major role in the future. Performing bipedal locomotion requires high energy due to the high torque that needs to be provided by its legs’ joints. Taking the WABIAN-2R as an example, it uses harmonic gears in its joint to increase the torque. However, using such a mechanism increases the weight of the legs and therefore increases energy consumption. Therefore, the idea of developing a mechanism with adjustable stiffness to be connected to the leg joint is introduced here. The proposed mechanism would have the ability to provide passive and active motion. The mechanism would be attached to the ankle pitch joint as an artificial tendon. Using computer simulations, the dynamical performance of the mechanism is analytically evaluated. Full article

(This article belongs to the Special Issue Mechanical Designs for Humanoids Robots: Problems and Solutions)

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Machines, Volume 4, Issue 1 (March 2016) – 9 articles

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