Fourier Analysis Guided Cable Actuator Design for Coordinated Walking Assistance

2021 ◽  
Author(s):  
Chong Liu ◽  
Rand Hidayah ◽  
Sunil Agrawal
Keyword(s):  
Fourier Transform ◽  
Curve Fitting ◽  
Degrees Of Freedom ◽  
State Of The Art ◽  
Simplified Model ◽  
Forward Kinematics ◽  
Joint Angles ◽  
Sine Curve ◽  
Design And Manufacture ◽  
Actuator Design

Abstract Cable-driven exoskeletons add minimal inertia and restrictions to the user’s leg while still providing feedback and quantitative measures of the user’s performance. However, cable robots require at least n + 1 cables to control n degrees-of-freedom, i.e., they require more actuators than the leg’s degrees-of-freedom, challenging their widespread adoption as wearable technology. The state-of-the-art in this field aims to reduce the number of actuated motors. In this paper, we design and evaluate a “single motor-driven” leg exoskeleton prototype based on the Cable-driven Active Leg EXoskleton (C-ALEX). The prototype consists of four crank-spring mechanisms and a crankshaft designed using epicycle analysis. The epicycle analysis is performed using discrete Fourier transform (DFT) and sine curve fitting (SCF). While DFT suggests the maximum number of epicycles to imitate the target waveform, a large number of nested epicycles is challenging to design and manufacture for implementation. To validate the epicycle-guided design, we constructed a simple crankshaft model using one epicycle. Our proposed simplified model predicted and produced the joint angles calculated from the inverse and forward kinematics of a cable-driven leg exoskeleton with multiple motors. To our knowledge, this is the first multi-cable driven exoskeleton powered by a single actuator that is designed to provide continuous assistance to the user.

Kinematics Modeling of a Notched Continuum Manipulator

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Zhijiang Du ◽  
Wenlong Yang ◽  
Wei Dong
Keyword(s):  
Curve Fitting ◽  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Kinematic Model ◽  
Inverse Kinematic ◽  
Forward Kinematics ◽  
Kinematics Modeling ◽  
Continuum Manipulators ◽  
Continuum Manipulator ◽  
The Continuum

In this paper, the kinematics modeling of a notched continuum manipulator is presented, which includes the mechanics-based forward kinematics and the curve-fitting-based inverse kinematics. In order to establish the forward kinematics model by using Denavit–Hartenberg (D–H) procedure, the compliant continuum manipulator featuring the hyper-redundant degrees of freedom (DOF) is simplified into finite discrete joints. Based on that hypothesis, the mapping from the discrete joints to the distal position of the continuum manipulator is built up via the mechanics model. On the other hand, to reduce the effect of the hyper-redundancy for the continuum manipulator's inverse kinematic model, the “curve-fitting” approach is utilized to map the end position to the deformation angle of the continuum manipulator. By the proposed strategy, the inverse kinematics of the hyper-redundant continuum manipulator can be solved by using the traditional geometric method. Finally, the proposed methodologies are validated experimentally on a triangular notched continuum manipulator which illustrates the capability and the effectiveness of our proposed kinematics for continuum manipulators and also can be used as a generic method for such notched continuum manipulators.

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..

Novel use of the Monte-Carlo methods to visualize singularity configurations in serial manipulators

2021 ◽  
Vol 15 (2) ◽  
pp. 7948-7963
Author(s):  
Mohamed Aboelnasr ◽  
Hussein M Bahaa ◽  
Ossama Mokhiamar
Keyword(s):  
Monte Carlo ◽  
Numerical Methods ◽  
Curve Fitting ◽  
Jacobian Matrix ◽  
Forward Kinematics ◽  
Graphical Methods ◽  
Kinematic Singularity ◽  
Serial Manipulators ◽  
Serial Robots ◽  
Contour Plots

This paper analyses the problem of the kinematic singularity of 6 DOF serial robots by extending the use of Monte-Carlo numerical methods to visualize singularity configurations. To achieve this goal, first, forward kinematics and D-H parameters have been derived for the manipulator. Second, the derived equations are used to generate and visualize a workspace that gives a good intuition of the motion shape of the manipulator. Third, the Jacobian matrix is computed using graphical methods, aiming to locate positions that cause singularity. Finally, the data obtained are processed in order to visualize the singularity and to design a trajectory free of singularity. MATLAB robotics toolbox, Symbolic toolbox, and curve fitting toolbox are the MATLAB toolboxes used in the calculations. The results of the surface and contour plots of the determinate of the Jacobian matrix behavior lead to design a manipulator’s trajectory free of singularity and show the parameters that affect the manipulator’s singularity and its behavior in the workspace.

A Fourier Transform Infrared Study of Mineral Matter in Coal: The Application of a Least Squares Curve-Fitting Program

1981 ◽  
Vol 35 (1) ◽  
pp. 102-106 ◽  
Author(s):  
Paul C. Painter ◽  
Susan M. Rimmer ◽  
Randy W. Snyder ◽  
Alan Davis
Keyword(s):  
Fourier Transform ◽  
Least Squares ◽  
Curve Fitting ◽  
Fourier Transform Infrared ◽  
Mineral Matter ◽  
Infrared Study ◽  
Least Squares Curve Fitting ◽  
Mineral Mixtures ◽  
Good Agreement

The application of Fourier transform infrared spectroscopy to the quantitative determination of mineral matter in coal is discussed. The use of a least squares curve-fitting program allows a choice between standards to be made. The results of an analysis of mineral mixtures and a coal low temperature ash are presented. The results are in good agreement with known concentrations and those obtained by other methods of analysis.

scholarly journals High-Dimensional Pixel Entanglement: Efficient Generation and Certification

Quantum ◽  
2020 ◽  
Vol 4 ◽  
pp. 376
Author(s):  
Natalia Herrera Valencia ◽  
Vatshal Srivastav ◽  
Matej Pivoluska ◽  
Marcus Huber ◽  
Nicolai Friis ◽  
...  
Keyword(s):  
Carrying Capacity ◽  
Communication Systems ◽  
Degrees Of Freedom ◽  
State Of The Art ◽  
Quality Measurement ◽  
High Dimensional ◽  
Single Photons ◽  
Spatial Mode ◽  
Classical Communication ◽  
Entanglement Of Formation

Photons offer the potential to carry large amounts of information in their spectral, spatial, and polarisation degrees of freedom. While state-of-the-art classical communication systems routinely aim to maximize this information-carrying capacity via wavelength and spatial-mode division multiplexing, quantum systems based on multi-mode entanglement usually suffer from low state quality, long measurement times, and limited encoding capacity. At the same time, entanglement certification methods often rely on assumptions that compromise security. Here we show the certification of photonic high-dimensional entanglement in the transverse position-momentum degree-of-freedom with a record quality, measurement speed, and entanglement dimensionality, without making any assumptions about the state or channels. Using a tailored macro-pixel basis, precise spatial-mode measurements, and a modified entanglement witness, we demonstrate state fidelities of up to 94.4% in a 19-dimensional state-space, entanglement in up to 55 local dimensions, and an entanglement-of-formation of up to 4 ebits. Furthermore, our measurement times show an improvement of more than two orders of magnitude over previous state-of-the-art demonstrations. Our results pave the way for noise-robust quantum networks that saturate the information-carrying capacity of single photons.

State-of-the-art imaging Fourier-transform spectrometer with CCD camera

2007 ◽  
Author(s):  
Jérôme E. Genest ◽  
Simon A. Roy ◽  
Patrick Dubois ◽  
Simon Potvin
Keyword(s):  
Fourier Transform ◽  
State Of The Art ◽  
Ccd Camera ◽  
Fourier Transform Spectrometer

scholarly journals A Workspace Visualization Method for a Multijoint Industrial Robot Based on the 3D-Printing Layering Concept

2020 ◽  
Vol 10 (15) ◽  
pp. 5241
Author(s):  
Guoqiang Fu ◽  
Chun Tao ◽  
Tengda Gu ◽  
Caijiang Lu ◽  
Hongli Gao ◽  
...  
Keyword(s):  
3D Printing ◽  
Joint Angle ◽  
Industrial Robot ◽  
Selection Method ◽  
Forward Kinematics ◽  
Visualization Method ◽  
Joint Angles ◽  
Boundary Extraction ◽  
Simulation And Experiment ◽  
Constraint Information

The workspace of a robot provides the necessary constraint information for path planning and reliable control of the robot. In this paper, a workspace visualization method for a multijoint industrial robot is proposed to obtain a detailed workspace by introducing the 3D-printing layering concept. Firstly, all possible joint-angle groups of one pose in the joints’ ranges are calculated in detail according to the POE (product of exponential) theory-based forward-kinematics expressions of the multijoint industrial robot. Secondly, a multisolution selection method based on the key degree of the joint is proposed to select the appropriate joint-angle groups. The key degrees of all joints and their key order are obtained according to the sensitivity expressions of all joint angles, calculated from the Jacobian matrix of the robot. One principle based on the smallest differences of the nominal angle is established to select the possible solutions for one joint from the possible solutions for the joint with the smaller key order. The possible solutions for the joint with the highest key order are the appropriate joint-angle group. Thirdly, a workspace visualization method based on the layering concept of 3D printing is presented to obtain a detailed workspace for a multijoint industrial robot. The boundary formula of each layer is derived by forward kinematics, which is expressed as a circle or a ring. The maximum and minimum values of the radius are obtained according to the travel range of the joint angles. The height limitations of all layers are obtained with forward kinematics. A workspace boundary-extraction method is presented to obtain the array of path points of the boundary at each layer. The proposed postprocessing method is used to generate the joint-angle code of each layer for direct 3D printing. Finally, the effectiveness of the multisolution selection method and the workspace visualization method were verified by simulation and experiment.

scholarly journals A Finger Grip Force Sensor with an Open-Pad Structure for Glove-Type Assistive Devices

Sensors ◽  
2019 ◽  
Vol 20 (1) ◽  
pp. 4 ◽  
Author(s):  
Junghoon Park ◽  
Pilwon Heo ◽  
Jung Kim ◽  
Youngjin Na
Keyword(s):  
Degrees Of Freedom ◽  
Grip Force ◽  
Force Sensor ◽  
Assistive Devices ◽  
Finger Joint ◽  
Assistive Device ◽  
Force Estimation ◽  
Joint Angles ◽  
Fingertip Force ◽  
Grasping Force

This paper presents a fingertip grip force sensor based on custom capacitive sensors for glove-type assistive devices with an open-pad structure. The design of the sensor allows using human tactile sensations during grasping and manipulating an object. The proposed sensor can be attached on both sides of the fingertip and measure the force caused by the expansion of the fingertip tissue when a grasping force is applied to the fingertip. The number of measurable degrees of freedom (DoFs) are the two DoFs (flexion and adduction) for the thumb and one DoF (flexion) for the index and middle fingers. The proposed sensor allows the combination with a glove-type assistive device to measure the fingertip force. Calibration was performed for each finger joint angle because the variations in the expansion of the fingertip tissue depend on the joint angles. The root mean square error (RMSE) for fingertip force estimation ranged from 3.75% to 9.71% after calibration, regardless of the finger joint angles or finger posture.

Application of Fractional Calculus for Dynamic Problems of Solid Mechanics: Novel Trends and Recent Results

2009 ◽  
Vol 63 (1) ◽  
Author(s):  
Yuriy A. Rossikhin ◽  
Marina V. Shitikova
Keyword(s):  
Fractional Calculus ◽  
Degrees Of Freedom ◽  
Solid Mechanics ◽  
State Of The Art ◽  
Dynamic Problems ◽  
Engineering Problems ◽  
Multilayered Systems ◽  
Linear And Nonlinear ◽  
Linear And Nonlinear Systems

The present state-of-the-art article is devoted to the analysis of new trends and recent results carried out during the last 10years in the field of fractional calculus application to dynamic problems of solid mechanics. This review involves the papers dealing with study of dynamic behavior of linear and nonlinear 1DOF systems, systems with two and more DOFs, as well as linear and nonlinear systems with an infinite number of degrees of freedom: vibrations of rods, beams, plates, shells, suspension combined systems, and multilayered systems. Impact response of viscoelastic rods and plates is considered as well. The results obtained in the field are critically estimated in the light of the present view of the place and role of the fractional calculus in engineering problems and practice. This articles reviews 337 papers and involves 27 figures.

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