Passively Driven Redundant Spherical Joint With Very Large Range of Motion

2017 ◽  
Vol 9 (3) ◽  
Author(s):  
Louis-Thomas Schreiber ◽  
Clément Gosselin
Keyword(s):  
Range Of Motion ◽  
Tilt Angle ◽  
Active Component ◽  
Large Range ◽  
Kinematic Model ◽  
Static Model ◽  
Spherical Joint ◽  
Torsional Spring

This paper presents a novel passive redundant spherical joint with a very large range of motion. A kinematic model is first developed in order to provide a framework for the analysis. The principle of the redundant joint is then introduced. The proposed joint does not require any active component since the redundancy is passively handled using springs. A static model of the joint is developed in order to clearly demonstrate how all singularities or jamming configurations can be avoided. Two possible arrangements are presented, one using linear springs and one using a torsional spring. Finally, experimental prototypes are demonstrated that can attain a range of tilt angle of ±150 deg.

scholarly journals Design, control, and testing of a thumb exoskeleton with series elastic actuation

2017 ◽  
Vol 36 (3) ◽  
pp. 355-375 ◽  
Author(s):  
Priyanshu Agarwal ◽  
Youngmok Yun ◽  
Jonas Fox ◽  
Kaci Madden ◽  
Ashish D Deshpande
Keyword(s):  
Range Of Motion ◽  
Degrees Of Freedom ◽  
Large Range ◽  
Kinematic Model ◽  
Torque Control ◽  
Thumb Motion ◽  
Performance Results ◽  
High Degree ◽  
Kinematic Mechanism ◽  
Series Elastic

We present an exoskeleton capable of assisting the human thumb through a large range of motion. Our novel thumb exoskeleton has the following unique features: (i) an underlying kinematic mechanism that is optimized to achieve a large range of motion, (ii) a design that actuates four degrees of freedom of the thumb, and (iii) a series elastic actuation based on a Bowden cable, allowing for bidirectional torque control of each thumb joint individually. We present a kinematic model of the coupled thumb exoskeleton system and use it to maximize the range of motion of the thumb. Finally, we carry out tests with the designed device on four subjects to evaluate its workspace and kinematic transparency using a motion capture system and torque control performance. Results show that the device allows for a large workspace with the thumb, is kinematically transparent to natural thumb motion to a high degree, and is capable of accurate torque control.

ON AN ORIENTATION TRANSITION IN NEMATIC LIQUID CRYSTALS INDUCED BY THE THICKNESS OF THE SAMPLE

1993 ◽  
Vol 07 (18) ◽  
pp. 1215-1222
Author(s):  
A. L. ALEXE-IONESCU
Keyword(s):  
Experimental Data ◽  
Phase Transitions ◽  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Tilt Angle ◽  
Critical Thickness ◽  
Large Range ◽  
Square Root ◽  
Chiral Molecules ◽  
Homeotropic Orientation

An orientation transition observed in nematic liquid crystal samples, induced by the thickness, is interpreted in a new way. By supposing that the nematic liquid crystal contains chiral impurities, it is shown that the homeotropic orientation is stable only for thicknesses smaller than a critical one, and is dependent on the concentration of the chiral molecules. At the critical thickness, the transition from the homeotropic orientation to the distorted one is characterized by a tilt angle proportional to the square root of the actual thickness minus the critical one. This trend is typical of second order phase transitions. The agreement between the theory and the experimental data is fairly good over a large range of thickness of the sample.

A Model of the Human Spine: Forward and Inverse Kinematics

1992 ◽  
Author(s):  
Sunil Kumar Agrawal ◽  
Siyan Li ◽  
Glen Desmier
Keyword(s):  
Range Of Motion ◽  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Kinematic Model ◽  
Joint Angles ◽  
Human Spine ◽  
Forward And Inverse Kinematics ◽  
Position And Orientation ◽  
Three Degrees Of Freedom ◽  
Adjacent Vertebra

Abstract The human spine is a sophisticated mechanism consisting of 24 vertebrae which are arranged in a series-chain between the pelvis and the skull. By careful articulation of these vertebrae, a human being achieves fine motion of the skull. The spine can be modeled as a series-chain with 24 rigid links, the vertebrae, where each vertebra has three degrees-of-freedom relative to an adjacent vertebra. From the studies in the literature, the vertebral geometry and the range of motion between adjacent vertebrae are well-known. The objectives of this paper are to present a kinematic model of the spine using the available data in the literature and an algorithm to compute the inter vertebral joint angles given the position and orientation of the skull. This algorithm is based on the observation that the backbone can be described analytically by a space curve which is used to find the joint solutions..

scholarly journals Effects of Anthropometric Variables and Seat Height on Automobile Drivers’ Preferred Posture With the Presence of the Clutch

2017 ◽  
Vol 60 (2) ◽  
pp. 172-190 ◽  
Author(s):  
Junfeng Peng ◽  
Xuguang Wang ◽  
Lisa Denninger
Keyword(s):  
Interior Design ◽  
Large Range ◽  
Kinematic Model ◽  
Vehicle Interior ◽  
Seat Height ◽  
Sitting Height ◽  
Test Conditions ◽  
Driving Posture ◽  
Trunk Orientation

Objective The effects of seat height and anthropometric dimensions on drivers’ preferred postures were investigated using a multiadjustable vehicle mock-up with a large number of adjustments and extended ranges. Background Many studies have been conducted on preferred driving posture under different test conditions showing mixed and even contradictory findings. No studies thus far have considered the clutch and compared Chinese and European drivers. Method Four seat height conditions were tested: free and three imposed heights (250, 300, and 350 mm). Sixty-one subjects (40 French-born and 21 Chinese-born) participated in the experiment, covering a large range of stature and sitting height–to–stature ratio. The RAMSIS kinematic model was used to reconstruct postures, and main intersegmental angles were extracted for characterizing posture. Results Under the free seat height condition, no significant differences in preferred intersegmental angles were observed between different participant groups. Seat height mainly affected trunk–thigh angle, whereas it had almost no effect on trunk orientation and other intersegmental angles. Chinese participants sat more forward in the seat, leading to a more opened trunk–thigh angle and a more reclined trunk. Conclusions Results suggest that intersegmental angles of preferred posture are not dependent on anthropometric dimensions, although shorter drivers prefer a slightly less reclined trunk. Self-selected driving posture results from a compromise between maintaining the intersegmental angles in one’s preferred range and a preferred trunk orientation in space. Applications The findings contribute to a better understanding of preferred driving postures and would be helpful for improving vehicle interior design.

Leg kinematic analysis and prototype experiments of walking-operating multifunctional hexapod robot

2013 ◽  
Vol 228 (12) ◽  
pp. 2217-2232 ◽  
Author(s):  
Pan Yang ◽  
Feng Gao
Keyword(s):  
Kinematic Analysis ◽  
Kinematic Model ◽  
Form Solution ◽  
Spherical Joint ◽  
Universal Joint ◽  
Step Size ◽  
Work Space ◽  
Prismatic Joint ◽  
Forward Kinematic ◽  
Close Form

This paper presents kinematic analysis of a 3-degree of freedom parallel mechanism for hexapod walking-operating multifuctional robot. Each leg of the robot consists of three limbs: universal joint – prismatic joint chain (1-UP) and universal joint – prismatic joint – spherical joint chain (2-UPS) and at the end of the leg there is passive spherical joint to adjust to the uneven ground. In this paper, first the forward kinematic model is built and it shows that the model has close-form solution. Then the work space is discussed in which the robot feet trajectories can be projected. It can be shown that the current trajectories of the feet only take very small work space. After that force analysis is performed and the results show that the payload capability of the mechanism is very high. Experiments of the prototype show that the robot can walk easily with more than 150 kg loads while the step size is more than 0.5 m.

A 3-DOF Translational Compliant Parallel Manipulator Based on Flexure Motion

2009 ◽  
Author(s):  
Guangbo Hao ◽  
Xianwen Kong
Keyword(s):  
Range Of Motion ◽  
Parallel Manipulator ◽  
Large Range ◽  
Parallel Manipulators ◽  
Mathematic Modeling ◽  
Ultra Precision ◽  
Cross Axis ◽  
Force Displacement

This paper presents a novel class of 3-DOF translational compliant parallel manipulators (CPMs) based on flexure motion. The analytic mathematic modeling of CPMs is first developed. The analysis of CPMs is then implemented. It is shown that the proposed CPMs have many characteristics such as large range of motion, negligible cross-axis coupling, actuator complete isolation, and no loss motion and no rotational yaw. The inverse relationships of force-displacement of the 3-DOF CPM are further derived to calculate the input forces required for generating a specified path. In addition, the 3-DOF CPM can also be turned into a 2-DOF CPM. This work lays the foundation for the development of new spatial CPMs based on flexure motions for applications such as ultra precision manipulation.

scholarly journals Narrative review of injuries in powerlifting with special reference to their association to the squat, bench press and deadlift

2018 ◽  
Vol 4 (1) ◽  
pp. e000382 ◽  
Author(s):  
Victor Bengtsson ◽  
Lars Berglund ◽  
Ulrika Aasa
Keyword(s):  
Special Reference ◽  
Range Of Motion ◽  
Bench Press ◽  
Large Range ◽  
Elite Athletes ◽  
Narrative Review ◽  
Previous Article ◽  
Physical Demands ◽  
Lifting Technique ◽  
Heavy Loads

Pain and injuries are considered a common problem among elite athletes and recreational lifters performing the squat, bench press and deadlift. Since all three lifts engage multiple joints and expose the lifters’ bodies to high physical demands often several times a week, it has been suggested that their injuries might be related to the excessively heavy loads, the large range of motion during the exercises, insufficient resting times between training sessions and/or faulty lifting technique. However, no previous article has summarised what is known about specific injuries and the injury aetiology associated with the three lifts. Thus, the aim of this narrative review was to summarise what is known about the relationships between the powerlifting exercises and the specific injuries or movement impairments that are common among lifters and recreationally active individuals.

scholarly journals Processing and Analysis of Long-Range Scans with an Atomic Force Microscope (AFM) in Combination with Nanopositioning and Nanomeasuring Technology for Defect Detection and Quality Control

Sensors ◽  
2021 ◽  
Vol 21 (17) ◽  
pp. 5862
Author(s):  
Ingo Ortlepp ◽  
Jaqueline Stauffenberg ◽  
Eberhard Manske
Keyword(s):  
Quality Control ◽  
High Resolution ◽  
Atomic Force Microscope ◽  
Range Of Motion ◽  
Defect Detection ◽  
Large Range ◽  
The Other ◽  
Atomic Force ◽  
Measuring Machine ◽  
The One

This paper deals with a planar nanopositioning and -measuring machine, the so-called nanofabrication machine (NFM-100), in combination with a mounted atomic force microscope (AFM). This planar machine has a circular moving range of 100 mm. Due to the possibility of detecting structures in the nanometre range with an atomic force microscope and the large range of motion of the NFM-100, structures can be analysed with high resolution and precision over large areas by combining the two systems, which was not possible before. On the basis of a grating sample, line scans over lengths in the millimetre range are demonstrated on the one hand; on the other hand, the accuracy as well as various evaluation methods are discussed and analysed.

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