scholarly journals Stability Criterion for Dynamic Gaits of Quadruped Robot

2018 ◽  
Vol 8 (12) ◽  
pp. 2381 ◽  
Author(s):  
Yan Jia ◽  
Xiao Luo ◽  
Baoling Han ◽  
Guanhao Liang ◽  
Jiaheng Zhao ◽  
...  
Keyword(s):  
Dynamic Stability ◽  
Stability Criterion ◽  
Quadruped Robot ◽  
Stability Criteria ◽  
Irregular Terrain ◽  
Quadruped Robots ◽  
Simulation Results ◽  
Zero Moment ◽  
The Stability ◽  
Dynamic Gait

Dynamic-stability criteria are crucial for robot’s motion planning and balance recovery. Nevertheless, few studies focus on the motion stability of quadruped robots with dynamic gait, none of which have accurately evaluated the robots’ stability. To fill the gaps in this field, this paper presents a new stability criterion for the motion of quadruped robots with dynamic gaits running over irregular terrain. The traditional zero-moment point (ZMP) is improved to analyze the motion on irregular terrain precisely for dynamic gaits. A dynamic-stability criterion and measurement are proposed to determine the stability state of the robot and to evaluate its stability. The simulation results show the limitations of the existing stability criteria for dynamic gaits and indicate that the criterion proposed in this paper can accurately and efficiently evaluate the stability of a quadruped robot using such gaits.

Intrinsic Thermal Stability of Anisotropic Thin-Film Superconductors

1990 ◽  
Vol 112 (1) ◽  
pp. 10-15 ◽  
Author(s):  
M. I. Flik ◽  
C. L. Tien
Keyword(s):  
Thin Film ◽  
Thermal Stability ◽  
Stability Criterion ◽  
High Temperature Superconductors ◽  
Stability Criteria ◽  
Anisotropic Thermal Conductivity ◽  
Operating Current ◽  
Released Energy ◽  
The Stability ◽  
Thermal Stability Of

Intrinsic thermal stability denotes a situation where a superconductor can carry the operating current without resistance at all times after the occurrence of a localized release of thermal energy. This novel stability criterion is different from the cryogenic stability criteria for magnets and has particular relevance to thin-film superconductors. Crystals of ceramic high-temperature superconductors are likely to exhibit anisotropic thermal conductivity. The resultant anisotropy of highly oriented films of superconductors greatly influences their thermal stability. This work presents an analysis for the maximum operating current density that ensures intrinsic stability. The stability criterion depends on the amount of released energy, the Biot number, the aspect ratio, and the ratio of the thermal conductivities in the plane of the film and normal to it.

scholarly journals Gait Tracking Control of Quadruped Robot Using Differential Evolution Based Structure Specified Mixed SensitivityH∞Robust Control

2016 ◽  
Vol 2016 ◽  
pp. 1-18 ◽  
Author(s):  
Petrus Sutyasadi ◽  
Manukid Parnichkun
Keyword(s):  
Tracking Control ◽  
Control Algorithm ◽  
Joint Angle ◽  
Gait Pattern ◽  
Quadruped Robot ◽  
Robust Controller ◽  
Quadruped Robots ◽  
Parameter Variations ◽  
Real Hardware ◽  
Dynamic Gait

This paper proposed a control algorithm that guarantees gait tracking performance for quadruped robots. During dynamic gait motion, such as trotting, the quadruped robot is unstable. In addition to uncertainties of parameters and unmodeled dynamics, the quadruped robot always faces some disturbances. The uncertainties and disturbances contribute significant perturbation to the dynamic gait motion control of the quadruped robot. Failing to track the gait pattern properly propagates instability to the whole system and can cause the robot to fall. To overcome the uncertainties and disturbances, structured specified mixed sensitivityH∞robust controller was proposed to control the quadruped robot legs’ joint angle positions. Before application to the real hardware, the proposed controller was tested on the quadruped robot’s leg planar dynamic model using MATLAB. The proposed controller can control the robot’s legs efficiently even under uncertainties from a set of model parameter variations. The robot was also able to maintain its stability even when it was tested under several terrain disturbances.

A Simplified Stability Criterion for Nonconservative Systems

1979 ◽  
Vol 46 (2) ◽  
pp. 423-426 ◽  
Author(s):  
I. Fawzy
Keyword(s):  
Dynamic Stability ◽  
Stability Criterion ◽  
Degrees Of Freedom ◽  
Necessary Condition ◽  
Matrix Methods ◽  
Nonconservative System ◽  
Nonconservative Systems ◽  
The Stability ◽  
Lyapunov’S Theorem ◽  
Sufficient And Necessary Condition

Dynamic stability of a general nonconservative system of n degrees of freedom is investigated. A sufficient and necessary condition for the stability of such a system is developed. It represents a simplified criterion based on the famous Lyapunov’s theorem which is proved afresh using λ-matrix methods only. When this criterion is adopted, it reduces the number of equations in Lyapunov’s method to less than half. A systematic procedure is then suggested for the stability investigation and its use is illustrated through a numerical example at the end of the paper.

Stability Margin of a Metamorphic Quadruped Robot With a Twisting Trunk

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Chunsong Zhang ◽  
Chi Zhang ◽  
Jian S. Dai ◽  
Peng Qi
Keyword(s):  
Closed Loop ◽  
Stability Margin ◽  
Rigid Bodies ◽  
Quadruped Robot ◽  
Quadruped Robots ◽  
Kinematic Performance ◽  
The Stability ◽  
Twisting Angle

Abstract To date, most quadruped robots are either equipped with trunks that are rigid bodies or consist of blocks connected by passive joints. The kinematic performance of these quadruped robots is only determined by their legs. To release the mobility of trunks and enhance the performance of quadruped robots, this paper proposes a metamorphic quadruped robot with a moveable trunk (a planar six-bar closed-loop linkage), called MetaRobot I, which can implement active trunk motions. The robot can twist its trunk like natural quadrupeds. Through trunk twisting, the stability margin of the quadruped robot can be increased compared with that of a quadruped robot with a rigid trunk. The inner relationship between the stability margin and the twisting angle is analyzed in this paper. Finally, simulations are carried out to show the benefits facilitated by the twisting trunk to the quadruped robot.

New stability criteria for a class of systems arising in neural network control and fuzzy systems

2000 ◽  
Vol 214 (1) ◽  
pp. 1-8
Author(s):  
Y Fang ◽  
T G Kincaid ◽  
S Li
Keyword(s):  
Neural Network ◽  
Stability Criterion ◽  
Fuzzy Systems ◽  
Neural Control ◽  
Network Control ◽  
Neural Network Control ◽  
Stability Criteria ◽  
Simple Derivation ◽  
The Stability

In this paper, the stability of a class of systems arising from neural control and fuzzy systems is studied. A new unifying stability criterion is presented using a very simple derivation. This result generalizes some previous results; some easily testable conditions are obtained.

Normalized Energy Stability Margin Based Analysis of Omni-Directional Static Walking of a Quadruped Robot on Rough Terrain

2011 ◽  
Vol 383-390 ◽  
pp. 7401-7405
Author(s):  
Lei Zhang ◽  
Shan Gao
Keyword(s):  
Stability Criterion ◽  
Simulation Experiment ◽  
Stability Margin ◽  
Quadruped Robot ◽  
Center Of Gravity ◽  
Energy Stability ◽  
Rough Terrain ◽  
The Stability

With Normalized Energy Stability Margin(Sne ) as stability criterion, this paper studies the tumbles of omni-directional static walking of a quadruped robot around the line connecting two adjacent supporting legs on rough terrain, proposes the method to improve the stability of quadruped robot by increasing the (Sne ) value, which is realized by lowering the height of center of gravity(COG), and finally substantiates the feasibility of the method through a simulation experiment.

scholarly journals Self-Stabilising Quadrupedal Running by Mechanical Design

2009 ◽  
Vol 6 (1) ◽  
pp. 73-85 ◽  
Author(s):  
Panagiotis Chatzakos ◽  
Evangelos Papadopoulos
Keyword(s):  
Mechanical System ◽  
Mechanical Design ◽  
Quadruped Robot ◽  
The Self ◽  
Rough Terrain ◽  
Stable Regime ◽  
Quadruped Robots ◽  
The Stability ◽  
Running Robots ◽  
Body Inertia

Dynamic stability allows running animals to maintain preferred speed during locomotion over rough terrain. It appears that rapid disturbance rejection is an emergent property of the mechanical system. In running robots, simple motor control seems to be effective in the negotiation of rough terrain when used in concert with a mechanical system that stabilises passively. Spring-like legs are a means for providing self-stabilising characteristics against external perturbations. In this paper, we show that a quadruped robot could be able to perform self-stable running behaviour in significantly broader ranges of forward speed and pitch rate with a suitable mechanical design, which is not limited to choosing legs spring stiffness only. The results presented here are derived by studying the stability of the passive dynamics of a quadruped robot running in the sagittal plane in a dimensionless context and might explain the success of simple, open loop running controllers on existing experimental quadruped robots. These can be summarised in (a) the self-stabilised behaviour of a quadruped robot for a particular gait is greatly related to the magnitude of its dimensionless body inertia, (b) the values of hip separation, normalised to rest leg length, and leg relative stiffness of a quadruped robot affect the stability of its motion and should be in inverse proportion to its dimensionless body inertia, and (c) the self-stable regime of quadruped running robots is enlarged at relatively high forward speeds. We anticipate the proposed guidelines to assist in the design of new, and modifications of existing, quadruped robots. As an example, specific design changes for the Scout II quadruped robot that might improve its performance are proposed.

Analysis of the Instability for Two Nano-Scale Liquid Threads Coexisting in a Periodic Fundamental Cell

2011 ◽  
Author(s):  
Chun-Lang Yeh
Keyword(s):  
Stability Criterion ◽  
Md Simulation ◽  
Density Field ◽  
Stability Criteria ◽  
Stable Domain ◽  
Nano Scale ◽  
Critical Wavelength ◽  
Molecular Scale ◽  
Vaporization Process ◽  
Simulation Results

This paper investigates the vaporization process of two nano-scale liquid threads coexisting in a periodic fundamental cell by molecular dynamics (MD) simulation. The influences of liquid thread radius, fundamental cell length, and relative position of the two threads are discussed. Snapshots of molecules, the number of liquid particles formed, and density field are analyzed. Two linear stability criteria, namely, Rayleigh’s stability criterion and Kim’s stability criterion, are accessed for their validity in molecular scale. It is found that more liquid particles are formed when the separation of the two threads is larger. Moreover, vaporization is slower when the two liquid threads are close to each other. It is also found that the trends of Rayleigh’s stability criterion and Kim’s stability criterion agree with MD simulation results. However, when the two threads coalesce into a single thread and remain intact, the critical wavelength of perturbation may be increased and the stable domain is broadened. Under such a situation, Rayleigh’s stability criterion and Kim’s stability criterion underpredict the stable domain.

Dynamic Stability of a Rotor Filled or Partially Filled With Liquid

1996 ◽  
Vol 63 (1) ◽  
pp. 101-105 ◽  
Author(s):  
Wen Zhang ◽  
Jiong Tang ◽  
Mingde Tao
Keyword(s):  
Dynamic Stability ◽  
Dynamic Pressure ◽  
Flow Analysis ◽  
Previous Literature ◽  
Stability Criteria ◽  
Stability Boundaries ◽  
Planar Flow ◽  
Harmonic Motion ◽  
Analytical Stability ◽  
The Stability

The dynamic stability of a high-spinning liquid-filled rotor with both internal and external damping effects involved in is investigated in this paper. First, in the case of the rotor subjected to a transverse harmonic motion, the dynamic pressure of the liquid acting on the rotor is extracted through a planar flow analysis. Then the equation of perturbed motion for the liquid-filled rotor is derived. The analytical stability criteria as well as the stability boundaries are given. The results are extensions of those given by previous literature.

Bifurcation Control of in Morris-Lecar Neuron Model via Washout Filter with a Linear Term Based on Filter-Aided Dynamic Feedback

2012 ◽  
Vol 485 ◽  
pp. 600-603 ◽  
Author(s):  
Hai Long Duan ◽  
Cheng Kun Cui ◽  
Chun Xiao Han ◽  
Yan Qiu Che
Keyword(s):  
Electrical Stimulation ◽  
Stability Criterion ◽  
Neuron Model ◽  
Linear Control ◽  
Control Parameters ◽  
Dynamic Feedback ◽  
Hurwitz Stability ◽  
Washout Filter ◽  
Simulation Results ◽  
The Stability

In this paper, based on Routh-Hurwitz stability criterion, the linear control term of washout filter-aided dynamic feedback controller is added to the Morris-Lecar (ML) system to stabilize the bifurcation. We deduce the linear control parameters according to the stability criterion, and the simulation results indicate that the controller is effective to stabilize ML model. In addition, electrical stimulation is selected as an output of the controller, thus it may provide theoretical guidance for clinical diagnosis and therapy of dynamical diseases.

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