scholarly journals Skyrmionics in correlated oxides

MRS Bulletin ◽  
2022 ◽  
Author(s):  
Zhi Shiuh Lim ◽  
Hariom Jani ◽  
T. Venkatesan ◽  
A. Ariando
Keyword(s):  
Electric Fields ◽  
Degrees Of Freedom ◽  
Magnetic Multilayers ◽  
Stray Field ◽  
Oxide Systems ◽  
Spin Orbital ◽  
Electric Fields And Currents ◽  
The Stability ◽  
And Control ◽  
Curie Temperatures

AbstractWhile chiral magnets, metal-based magnetic multilayers, or Heusler compounds have been considered as the material workhorses in the field of skyrmionics, oxides are now emerging as promising alternatives, as they host special correlations between the spin–orbital–charge–lattice degrees of freedom and/or coupled ferroic order parameters. These interactions open new possibilities for practically exploiting skyrmionics. In this article, we review the recent advances in the observation and control of topological spin textures in various oxide systems. We start with the discovery of skyrmions and related quasiparticles in bulk and heterostructure ferromagnetic oxides. Next, we emphasize the shortcomings of implementing ferromagnetic textures, which have led to the recent explorations of ferrimagnetic and antiferromagnetic oxide counterparts, with higher Curie temperatures, stray-field immunity, low Gilbert damping, ultrafast magnetic dynamics, and/or absence of skyrmion deflection. Then, we highlight the development of novel pathways to control the stability, motion, and detection of topological textures using electric fields and currents. Finally, we present the outstanding challenges that need to be overcome to achieve all-electrical, nonvolatile, low-power oxide skyrmionic devices. Graphical abstract

Design of Materials and Mechanisms for Responsive Robots

2018 ◽  
Vol 1 (1) ◽  
pp. 359-384 ◽  
Author(s):  
Elliot W. Hawkes ◽  
Mark R. Cutkosky
Keyword(s):  
Genetic Algorithms ◽  
Energy Storage ◽  
Environmental Conditions ◽  
Degrees Of Freedom ◽  
Closed Loop ◽  
Open Loop ◽  
Challenging Problem ◽  
Manufacturing Applications ◽  
The Stability ◽  
And Control

As robots move beyond manufacturing applications to less predictable environments, they can increasingly benefit, as animals do, from integrating sensing and control with the passive properties provided by particular combinations and arrangements of materials and mechanisms. This realization is partly responsible for the recent proliferation of soft and bioinspired robots. Tuned materials and mechanisms can provide several kinds of benefits, including energy storage and recovery, increased physical robustness, and decreased response time to sudden events. In addition, they may offer passive open-loop behaviors and responses to external changes in loading or environmental conditions. Collectively, these properties can also increase the stability of a robot as it interacts with the environment and allow the closed-loop controller to reduce the apparent degrees of freedom subject to control. The design of appropriate materials and mechanisms remains a challenging problem; bioinspiration, genetic algorithms, and numerical shape and materials optimization are all applicable. New multimaterial fabrication processes are also steadily increasing the range and magnitude of passive properties available for intrinsically responsive robots.

Modeling and Control of a Spherical Inverted Pendulum With Actuator Saturation

2019 ◽  
Author(s):  
Geovani Bondo ◽  
Chengzhi Yuan ◽  
Chang Duan
Keyword(s):  
Degrees Of Freedom ◽  
Inverted Pendulum ◽  
Actuator Saturation ◽  
Control Strategies ◽  
Mathematic Model ◽  
Disturbance Attenuation ◽  
Modeling And Control ◽  
Advanced Control ◽  
The Stability ◽  
And Control

Abstract This paper studies the modeling and control of a spherical inverted pendulum (SIP). The SIP is deemed to be a reasonable model for rocket-propelled body and is often used to test advanced control strategies. The mathematic model is derived based on a Quanser two degrees-of-freedom inverted pendulum commercial product. The pendulum is mounted on a five-bar mechanism that is actuated by two rotary servo base units. Unlike conventional assumption that the two motors are allowed to rotate simultaneously, we assume a more challenging scenario that at one time only one motor is working. The system is hence modeled as a switched system as two motors have to be switched in order to balance the pendulum at its unstable equilibrium. Switched controllers, together with a switching strategy are developed to ensure the stability of the system and satisfy a disturbance attenuation performance index. Simulation results are presented to show the effectiveness of the proposed method.

scholarly journals Performance Analysis on Depth and Straight Motion Control based on Control Surface Combinations for Supercavitating Underwater Vehicle

2021 ◽  
Vol 24 (4) ◽  
pp. 435-448
Author(s):  
Beomyeol Yu ◽  
Hyemin Mo ◽  
Seungkeun Kim ◽  
Jong-Hyon Hwang ◽  
Jeong-Hoon Park ◽  
...  
Keyword(s):  
Motion Control ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Underwater Vehicle ◽  
Control Surface ◽  
Control Performance ◽  
Friction Resistance ◽  
Control Loops ◽  
The Stability ◽  
And Control

This study describes the depth and straight motion control performance depending on control surface combinations of a supercavitating underwater vehicle. When an underwater vehicle experiences supercavitation, friction resistance can be minimized, thus achieving the effect of super-high-speed driving. Six degrees of freedom modeling of the underwater vehicle are performed and the guidance and control loops are designed with not only a cavitator and an elevator, but also a rudder and a differential elevator to improve the stability of the roll and yaw axis. The control performance based on the combination of control surfaces is analyzed by the root-mean-square error for keeping depth and straight motion.

Modeling and control of an underactuated tractor–trailer wheeled mobile robot

Robotica ◽  
2017 ◽  
Vol 35 (12) ◽  
pp. 2297-2318 ◽  
Author(s):  
Asghar Khanpoor ◽  
Ali Keymasi Khalaji ◽  
S. Ali A. Moosavian
Keyword(s):  
Mobile Robot ◽  
Control Algorithm ◽  
Degrees Of Freedom ◽  
Wheeled Mobile Robot ◽  
Robot Kinematics ◽  
Wheeled Mobile Robots ◽  
Modeling And Control ◽  
Pure Rolling ◽  
The Stability ◽  
And Control

SUMMARYTrajectory tracking is one of the main control problems in the context of Wheeled Mobile Robots (WMRs). Control of underactuated systems has been focused by many researchers during past few years. In this paper, tracking control of a Tractor–Trailer Wheeled Mobile Robot (TTWMR) has been discussed. TTWMR includes a differential drive WMR towing a passive spherical wheeled trailer. Spherical wheels in contrast with standard wheels make the robot highly underactuated with severe non-linearities. Underactuation is due to the use of spherical wheeled trailer to increase robots' maneuverability and degrees of freedom. In fact, standard wheels are subjected to non-holonomic constraints due to pure rolling and non-slip conditions, which reduce robot maneuverability. In this paper, after introducing the robot, kinematics and kinetics models are obtained. Then, based on a physical intuition, a novel control algorithm is developed for the robot, i.e. Lyapunov-PID control algorithm. Subsequently, singularity avoidance of the proposed algorithm is discussed and the stability of the algorithm is analyzed. Finally, simulation and experimental results are presented which reveal the effectiveness of the proposed algorithm.

Biped walking robots created at Waseda University: WL and WABIAN family

2006 ◽  
Vol 365 (1850) ◽  
pp. 49-64 ◽  
Author(s):  
Hun-ok Lim ◽  
Atsuo Takanishi
Keyword(s):  
Degrees Of Freedom ◽  
Vision System ◽  
Humanoid Robots ◽  
Recognition System ◽  
Lower Limbs ◽  
Walking Robots ◽  
Compensatory Motion ◽  
Zero Moment ◽  
The Stability ◽  
And Control

This paper proposes the mechanism and control of the biped humanoid robots WABIAN-RIV and WL-16. WABIAN-RIV has 43 mechanical degrees of freedom (d.f.): 6 d.f. in each leg, 7 d.f. in each arm, 3 d.f. in each hand, 2 d.f. in each eye, 4 d.f. in the neck and 3 d.f. in the waist. Its height is about 1.89 m and its total weight is 127 kg. It has a vision system and a voice recognition system to mimic some of the capabilities of the human senses. WL-16 consists of a pelvis and two legs having six 1 d.f. active linear actuators. An aluminium chair is mounted on two sets of its telescopic poles. To reduce the large support forces during the support phase, a support torque reduction mechanism is developed, which is composed of two compression gas springs with different stiffness. For the stability of the robots, a compensatory motion control algorithm is developed. This control compensates for moments generated by the motion of the lower limbs, using the motion of the trunk and the waist that is obtained by the zero moment point concept and fast Fourier transform. WABIAN-RIV is able to walk forwards, backwards and sideways, dance, carry heavy goods and express emotion, etc. WL-16 can move forwards, backwards and sideways while carrying an adult weighing up to 60 kg.

Towards a unified understanding of basic notions and terms in humanoid robotics

Robotica ◽  
2006 ◽  
Vol 25 (1) ◽  
pp. 87-101 ◽  
Author(s):  
M. Vukobratović ◽  
B. Borovac ◽  
V. Potkonjak
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Balance ◽  
Humanoid Robots ◽  
External Disturbances ◽  
Humanoid Robotics ◽  
Gait Stability ◽  
High Dynamic ◽  
The Difference ◽  
The Stability ◽  
And Control

The intention of this paper is to contribute towards a unified understanding of the basic notions and terms in the domain of humanoid robotics, having in mind that the same notions are sometimes interpreted in different ways (some interpretations are contradictory, and some even erroneous). Hence, the first part of the paper is devoted to defining some basic notions, walk and gait being among the first. Then, the paper deals with the notion of dynamic balance and stability, particularly the difference between them, since these essentially different notions are often confused and, rarely, regarded as identical. As dynamic balance is directly related to the notion of zero-moment point (ZMP), it was necessary to touch upon some misunderstandings concerning the ZMP. Gait stability is an especially delicate category, as humanoid locomotion systems have certain specific features that are not possessed by other systems. Namely, because of external disturbances, there may appear unpowered (passive) degrees of freedom that cause loss of dynamic balance. Hence, these unpowered degrees of freedom cannot be overlooked in the stability analysis. As the stability of motion of humanoid robots is inseparably linked with control, it was also necessary to pay due attention to this notion. Finally, the paper ends with a discussion of posture and postural stability with all their specificities. The authors hope that this paper will contribute to a clearer understanding of the basic notions of humanoid robotics, especially concerning robots with high dynamic and control performances.

Control of Metal Alloy Oxidation with Electric Fields

1973 ◽  
Vol 31 ◽  
pp. 164-165
Author(s):  
R. R. Dils ◽  
P. S. Follansbee
Keyword(s):  
Electric Fields ◽  
Oxidation Process ◽  
Base Alloy ◽  
Oxide Surface ◽  
Platinum Electrodes ◽  
Insulating Layer ◽  
Iron Base Alloy ◽  
Alloy Oxidation ◽  
Aluminum Oxide Layer ◽  
And Control

Electric fields have been applied across oxides growing on a high temperature alloy and control of the oxidation of the material has been demonstrated. At present, three-fold increases in the oxidation rate have been measured in accelerating fields and the oxidation process has been completely stopped in a retarding field.The experiments have been conducted with an iron-base alloy, Pe 25Cr 5A1 0.1Y, although, in principle, any alloy capable of forming an adherent aluminum oxide layer during oxidation can be used. A specimen is polished and oxidized to produce a thin, uniform insulating layer on one surface. Three platinum electrodes are sputtered on the oxide surface and the specimen is reoxidized.

Control of processing at multi-tool two-support setup

2020 ◽  
pp. 67-73
Author(s):  
N.D. YUsubov ◽  
G.M. Abbasova
Keyword(s):  
Degrees Of Freedom ◽  
Factor Model ◽  
Angular Displacement ◽  
Factor Models ◽  
Technological System ◽  
Displacement Control ◽  
Model Accuracy ◽  
Six Degrees Of Freedom ◽  
Angular Displacements ◽  
And Control

The accuracy of two-tool machining on automatic lathes is analyzed. Full-factor models of distortions and scattering fields of the performed dimensions, taking into account the flexibility of the technological system on six degrees of freedom, i. e. angular displacements in the technological system, were used in the research. Possibilities of design and control of two-tool adjustment are considered. Keywords turning processing, cutting mode, two-tool setup, full-factor model, accuracy, angular displacement, control, calculation [email protected]

scholarly journals Data-Driven Stability Assessment of Multilayer Long Short-Term Memory Networks

2021 ◽  
Vol 11 (4) ◽  
pp. 1829
Author(s):  
Davide Grande ◽  
Catherine A. Harris ◽  
Giles Thomas ◽  
Enrico Anderlini
Keyword(s):  
Neural Network ◽  
Network Architecture ◽  
Short Term Memory ◽  
Moving Average ◽  
Machine Learning Algorithms ◽  
Physical Models ◽  
Data Driven ◽  
The Stability ◽  
And Control ◽  
Nonlinear Autoregressive

Recurrent Neural Networks (RNNs) are increasingly being used for model identification, forecasting and control. When identifying physical models with unknown mathematical knowledge of the system, Nonlinear AutoRegressive models with eXogenous inputs (NARX) or Nonlinear AutoRegressive Moving-Average models with eXogenous inputs (NARMAX) methods are typically used. In the context of data-driven control, machine learning algorithms are proven to have comparable performances to advanced control techniques, but lack the properties of the traditional stability theory. This paper illustrates a method to prove a posteriori the stability of a generic neural network, showing its application to the state-of-the-art RNN architecture. The presented method relies on identifying the poles associated with the network designed starting from the input/output data. Providing a framework to guarantee the stability of any neural network architecture combined with the generalisability properties and applicability to different fields can significantly broaden their use in dynamic systems modelling and control.

scholarly journals Velocity and acceleration level inverse kinematic calculation alternatives for redundant manipulators

Meccanica ◽  
2021 ◽  
Author(s):  
Dóra Patkó ◽  
Ambrus Zelei
Keyword(s):  
Degrees Of Freedom ◽  
Direct Method ◽  
Tracking Error ◽  
Inverse Kinematic ◽  
Linear Feedback ◽  
Joint Position ◽  
Stability Properties ◽  
Acceleration Level ◽  
Error Elimination ◽  
The Stability

AbstractFor both non-redundant and redundant systems, the inverse kinematics (IK) calculation is a fundamental step in the control algorithm of fully actuated serial manipulators. The tool-center-point (TCP) position is given and the joint coordinates are determined by the IK. Depending on the task, robotic manipulators can be kinematically redundant. That is when the desired task possesses lower dimensions than the degrees-of-freedom of a redundant manipulator. The IK calculation can be implemented numerically in several alternative ways not only in case of the redundant but also in the non-redundant case. We study the stability properties and the feasibility of a tracking error feedback and a direct tracking error elimination approach of the numerical implementation of IK calculation both on velocity and acceleration levels. The feedback approach expresses the joint position increment stepwise based on the local velocity or acceleration of the desired TCP trajectory and linear feedback terms. In the direct error elimination concept, the increment of the joint position is directly given by the approximate error between the desired and the realized TCP position, by assuming constant TCP velocity or acceleration. We investigate the possibility of the implementation of the direct method on acceleration level. The investigated IK methods are unified in a framework that utilizes the idea of the auxiliary input. Our closed form results and numerical case study examples show the stability properties, benefits and disadvantages of the assessed IK implementations.

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