scholarly journals No Need for a Body Model: Positive Velocity Feedback for the Control of an 18-DOF Robot Walker

2008 ◽  
Vol 5 (3) ◽  
pp. 135-147 ◽  
Author(s):  
Josef Schmitz ◽  
Axel Schneider ◽  
Malte Schilling ◽  
Holk Cruse
Keyword(s):  
Kinematic Chain ◽  
The Body ◽  
Dynamics Simulation ◽  
Explicit Calculation ◽  
Time Step ◽  
Joint Power ◽  
Velocity Feedback ◽  
Body Model ◽  
Multilegged Walking Robot ◽  
Joint Velocity

In a multilegged walking robot several legs usually have ground contact and thereby form a closed kinematic chain. The control of such a system is generally assumed to require the explicit calculation of the body kinematics. Such a computation requires knowledge concerning all relevant joint angles as well as the segment lengths. Here, we propose a biologically inspired solution that does not need such a body model. This is done by using implicit communication through the body mechanics (embodiment) and a local positive velocity feedback strategy (LPVF) on the single joint level. In this control scheme the locally measured joint velocity of an elastic joint is fed into the same joint during the next time step to maintain the movement. At the same time, an additional part of this joint controller observes the mechanical joint power to confine the positive feedback. This solution does not depend on changes of the geometry, e.g. length of individual segments, and allows for a simple solution of negotiation of curves. The principle is tested in a dynamics simulation on a six-legged walker and, for the first time, also on a real robot.

Design of the Assistive Leg and the Simulation Research

2013 ◽  
Vol 339 ◽  
pp. 147-152
Author(s):  
Zhen Ze Liu ◽  
Lei Zhang ◽  
Yan Tao Tian
Keyword(s):  
Lower Extremity ◽  
The Body ◽  
Dynamics Simulation ◽  
Human Body Model ◽  
Compact Structure ◽  
Simulation Research ◽  
Existing Problems ◽  
Body Model ◽  
Simulation Results ◽  
Exoskeleton Device

The wearable assistive leg is a kind of traditional exoskeleton device, which not only can help healthy people with walking, but also can assist those who have walking troubles to rehabilitate. Based on the bionics principle and the research on the body mechanism, a wearable assistive leg for rehabilitation training and power augmentation is designed. This device satisfies the requirement of the compact structure, portability and safety. Then the dynamic model of the assistive leg is constructed based on the Lagrange theory. The mechanical structure is devised by Solidworks2011 software in which a standard human body model and this assistive leg are assembled. Thus the assembly is introduced into Adams2007 R3. The dynamics simulation is carried in this software. The results and the existing problems are analyzed. The simulation results show that this kind of assistive leg can provide helping force for human lower extremity movements.

Design and operation of a tripod walking robot via dynamics simulation

Robotica ◽  
2010 ◽  
Vol 29 (5) ◽  
pp. 733-743 ◽  
Author(s):  
Conghui Liang ◽  
Hao Gu ◽  
Marco Ceccarelli ◽  
Giuseppe Carbone
Keyword(s):  
Mechanical Design ◽  
Low Cost ◽  
Three Dimensional ◽  
The Body ◽  
Dynamics Simulation ◽  
Walking Ability ◽  
Walking Robot ◽  
Three Dimensional Model ◽  
Software Environment ◽  
Leg Mechanisms

SUMMARYA mechanical design and dynamics walking simulation of a novel tripod walking robot are presented in this paper. The tripod walking robot consists of three 1-degree-of-freedom (DOF) Chebyshev–Pantograph leg mechanisms with linkage architecture. A balancing mechanism is mounted on the body of the tripod walking robot to adjust its center of gravity (COG) during walking for balancing purpose. A statically stable tripod walking gait is performed by synchronizing the motions of the three leg mechanisms and the balancing mechanism. A three-dimensional model has been elaborated in SolidWorks® engineering software environment for a characterization of a feasible mechanical design. Dynamics simulation has been carried out in the MSC.ADAMS® environment with the aim to characterize and to evaluate the dynamic walking performances of the proposed design with low-cost easy-operation features. Simulation results show that the proposed tripod walking robot with proper input torques, gives limited reaction forces at the linkage joints, and a practical feasible walking ability on a flatten ground.

NUMERICAL SOLUTIONS OF 2D AND 3D SLAMMING PROBLEMS

2021 ◽  
Vol 153 (A2) ◽  
Author(s):  
Q Yang ◽  
W Qiu
Keyword(s):  
Free Surface ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Type Equation ◽  
The Body ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Highly Nonlinear ◽  
2D And 3D

Slamming forces on 2D and 3D bodies have been computed based on a CIP method. The highly nonlinear water entry problem governed by the Navier-Stokes equations was solved by a CIP based finite difference method on a fixed Cartesian grid. In the computation, a compact upwind scheme was employed for the advection calculations and a pressure-based algorithm was applied to treat the multiple phases. The free surface and the body boundaries were captured using density functions. For the pressure calculation, a Poisson-type equation was solved at each time step by the conjugate gradient iterative method. Validation studies were carried out for 2D wedges with various deadrise angles ranging from 0 to 60 degrees at constant vertical velocity. In the cases of wedges with small deadrise angles, the compressibility of air between the bottom of the wedge and the free surface was modelled. Studies were also extended to 3D bodies, such as a sphere, a cylinder and a catamaran, entering calm water. Computed pressures, free surface elevations and hydrodynamic forces were compared with experimental data and the numerical solutions by other methods.

A New Method to Concentrate Electromagnetic Field Within ROI Using a High Dielectric Material in 3T Body MRI

2013 ◽  
Author(s):  
Bu S. Park ◽  
Sunder S. Rajan ◽  
Leonardo M. Angelone
Keyword(s):  
Numerical Simulation ◽  
Electromagnetic Field ◽  
Human Body ◽  
Region Of Interest ◽  
Dielectric Materials ◽  
The Body ◽  
Human Body Model ◽  
Body Model ◽  
Simulation Results ◽  
High Dielectric

We present numerical simulation results showing that high dielectric materials (HDMs) when placed between the human body model and the body coil significantly alter the electromagnetic field inside the body. The numerical simulation results show that the electromagnetic field (E, B, and SAR) within a region of interest (ROI) is concentrated (increased). In addition, the average electromagnetic fields decreased significantly outside the region of interest. The calculation results using a human body model and HDM of Barium Strontium Titanate (BST) show that the mean local SAR was decreased by about 56% (i.e., 18.7 vs. 8.2 W/kg) within the body model.

scholarly journals Sport experience and the symbolism of the body. Story of a student´s initial training | Experiencia deportiva e imaginario corporal. Relato de una alumna en formación inicial

2020 ◽  
Vol 13 (27) ◽  
pp. 121
Author(s):  
María Esther Prados Megías ◽  
Bella Aurelia Maldonado Mora
Keyword(s):  
Physical Activity ◽  
Physical Education ◽  
Narrative Research ◽  
The Body ◽  
Initial Training ◽  
Body Model ◽  
Rhythmic Gymnastics ◽  
The World ◽  
Sports Sciences ◽  
Educational Careers

ResumenLas experiencias que tienen jóvenes deportistas a lo largo de su trayectoria deportiva y educativa van dando sentido y significado al modo en cómo éstos, como futuros profesionales del campo de las ciencias de la actividad física y el deporte, van construyendo diferentes concepciones de la motricidad humana. Desde el enfoque de la investigación biográfica narrativa profundizamos en el relato de Glissade, alumna en formación inicial que ha desarrollado su trayectoria deportiva en el mundo de la Gimnasia Rítmica. El objetivo de este trabajo es indagar en algunas de las representaciones del modelo corporal y los aspectos emocionales-relacionales que constituyen la identidad deportiva de esta mujer y cómo ello está presente en su formación inicial. El relato de Glissade nos acerca a dos cuestiones: las tensiones entre su cuerpo de mujer y las exigencias del deporte que practica, ambos sujetos a cánones tradicionales sobre lo bello/estético y los aprendizajes emocionales que están presentes en su práctica deportiva. Este trabajo evidencia la importancia de visibilizar y conocer la experiencia de las personas desde su propia voz, ya que ello permite reflexionar sobre creencias, pensamientos y modelos que persisten en los procesos de formación inicial de futuros profesionales de la educación física y el deporte.AbstractThe experiences that young sportsmen and women have throughout their sporting and educational careers are giving meaning and significance to the way in how they, as future professionals in the field of physical activity and sports sciences, are building different conceptions of human motricity. From the focus of biographical narrative research, we delved into the story of Glissade, a student in initial training who has developed her sports career in the world of Rhythmic Gymnastics. The aim of this work is to investigate the representations of the body model and the emotional-relational aspects that constitute the sports identity of this woman and how this is present in her initial training. Glissade´s story brings us closer to two questions: the tensions between her body as a woman and the demands of a sport she plays, both are subject to traditional canons of beauty/aesthetics and the emotional learnings that are present in their sports practice. This work shows the importance of making visible and knowing the experience of people from their own voice, since this allows reflection on beliefs, thoughts and models that persist in the processes of initial training of future professionals in physical education and sport.

Lower Limb Human Muscle Enhancer

2001 ◽  
Author(s):  
Joseph J. Misuraca ◽  
Constantinos Mavroidis
Keyword(s):  
Lower Limb ◽  
Weight Bearing ◽  
Kinematic Chain ◽  
Human Muscle ◽  
The Body ◽  
Knee Joints ◽  
Lower Body ◽  
Loop Control ◽  
Test Fixture ◽  
Leg Muscles

Abstract This paper describes the design, control, and testing of a Human Muscle Enhancer (HME) system that will augment the muscle capabilities of subjects requiring partial lower-limb weight-bearing gait support. The HME described in this paper is a pneumatically actuated quick connecting exoskeleton system that attaches to the foot and hip area of the body, thus “closing” the lower body kinematic chain. Control of the system is achieved by using encoders at the knee joints and Myo-Pneumatic (MP) Sensors implanted into the shoes and outer garments of the human. To test this design concept, a lower body exoskeleton test fixture has been fabricated. The test fixture mimics the human leg with the top cylinder providing the body weight on the leg. Another cylinder acts as leg muscles to provide the adjustable human reaction of the leg. Preliminary open and closed loop control tests have been performed that demonstate the capability of controlling the HME using the MP sensors.

A Nonlinear Optimal Control Approach for the Vertical Take-off and Landing Aircraft

2021 ◽  
pp. 2150012
Author(s):  
G. Rigatos
Keyword(s):  
Optimal Control ◽  
Control Method ◽  
Nonlinear Optimal Control ◽  
The Body ◽  
Algebraic Riccati Equation ◽  
Control Input ◽  
Time Step ◽  
Control Approach ◽  
Vtol Aircraft ◽  
Optimal Control Approach

The paper proposes a nonlinear optimal control approach for the model of the vertical take-off and landing (VTOL) aircraft. This aerial drone receives as control input a directed thrust, as well as forces acting on its wing tips. The latter forces are not perpendicular to the body axis of the drone but are tilted by a small angle. The dynamic model of the VTOL undergoes approximate linearization with the use of Taylor series expansion around a temporary operating point which is recomputed at each iteration of the control method. For the approximately linearized model, an H-infinity feedback controller is designed. The linearization procedure relies on the computation of the Jacobian matrices of the state-space model of the VTOL aircraft. The proposed control method stands for the solution of the optimal control problem for the nonlinear and multivariable dynamics of the aerial drone, under model uncertainties and external perturbations. For the computation of the controller’s feedback gains, an algebraic Riccati equation is solved at each time-step of the control method. The new nonlinear optimal control approach achieves fast and accurate tracking for all state variables of the VTOL aircraft, under moderate variations of the control inputs. The stability properties of the control scheme are proven through Lyapunov analysis.

scholarly journals Computational models for contact current dosimetry at frequencies below 1 MHz

2020 ◽  
Author(s):  
Pia Schneeweiss ◽  
Dorin Panescu ◽  
Dominik Stunder ◽  
Mark W. Kroll ◽  
Christopher J. Andrews ◽  
...  
Keyword(s):  
Computational Models ◽  
Scientific Basis ◽  
The Body ◽  
In Vivo Studies ◽  
International Electrotechnical Commission ◽  
Safety Standards ◽  
Body Model ◽  
Current Path ◽  
Cadaver Studies

AbstractElectric contact currents (CC) can cause muscle contractions, burns, or ventricular fibrillation which may result in life-threatening situations. In vivo studies with CC are rare due to potentially hazardous effects for participants. Cadaver studies are limited to the range of tissue’s electrical properties and the utilized probes’ size, relative position, and sensitivity. Thus, the general safety standards for protection against CC depend on a limited scientific basis. The aim of this study was therefore to develop an extendable and adaptable validated numerical body model for computational CC dosimetry for frequencies between DC and 1 MHz. Applying the developed model for calculations of the IEC heart current factors (HCF) revealed that in the case of transversal CCs, HCFs are frequency dependent, while for longitudinal CCs, the HCFs seem to be unaffected by frequency. HCFs for current paths from chest or back to hand appear to be underestimated by the International Electrotechnical Commission (IEC 60479-1). Unlike the HCFs provided in IEC 60479-1 for longitudinal current paths, our work predicts the HCFs equal 1.0, possibly due to a previously unappreciated current flow through the blood vessels. However, our results must be investigated by further research in order to make a definitive statement. Contact currents of frequencies from DC up to 100 kHz were conducted through the numerical body model Duke by seven contact electrodes on longitudinal and transversal paths. The resulting induced electric field and current enable the evaluation of the body impedance and the heart current factors for each frequency and current path.

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