Effect of external and internal cues on core muscle activation during the Sahrmann five-level core stability test

BACKGROUND Pain in the back or pelvis or fear of back pain may affect the timing or cocontraction of the core muscles.In both static and dynamic movements,the Sahrmann core stability test provides an assessment of core muscle activation and a person's ability to stabilize the lumbopelvic complex.Preparatory cues and images can be used to increase the activation of these muscles.To attain optimal movement patterns,it will be necessary to determine what cueing will give the most effective results for core stability.AIM To investigate the effects of external and internal cues on core muscle activation during the Sahrmann five-level core stability test.METHODS Total 68 participants(21.83±3.47 years)were randomly allocated to an external(n=35)or internal cue group(n=33).Participants performed the Sahrmann fivelevel core stability test without a cue as baseline and the five-level stability exercises with an internal or external cue.External cue group received a pressure biofeedback unit(PBU),and the internal cue group received an audio cue.A Delsys Trigno^(TM)surface electromyography unit was used for muscle activation from the rectus abdominis,external oblique,and transverse abdominis/internal oblique muscles.RESULTS Linear mixed effects model analysis showed that cueing had a significant effect on core muscle activation(P=0.001);however,there was no significant difference between cue types(internal or external)(P=0.130).CONCLUSION Both external and internal cueing have significant effects on core muscle activation during the Sahrmann five-level core stability test and the PBU does not create higher muscle activation than internal cueing.

New criterion for delay-dependent absolute stability of Lurie system with interval time-varying delay

The delay-dependent absolute stability for a class of Lurie systems with interval time-varying delay is studied. By employing an augmented Lyapunov functional and combining a free-weighting matrix approach and the reciprocal convex technique, an improved stability condition is derived in terms of linear matrix inequalities （LMIs）. By retaining some useful terms that are usually ignored in the derivative of the Lyapunov function, the proposed sufficient condition depends not only on the lower and upper bounds of both the delay and its derivative, but it also depends on their differences, which has wider application fields than those of present results. Moreover, a new type of equality expression is developed to handle the sector bounds of the nonlinear function, which achieves fewer LMIs in the derived condition, compared with those based on the convex representation. Therefore, the proposed method is less conservative than the existing ones. Simulation examples are given to demonstrate the validity of the approach.

Absolute Exponential Stability of Generalized Dynamical Neural Networks

This paper investigates the absolute exponential stability of generalized neural networks with a general class of partially Lipschitz continuous and monotone increasing activation functions. The main obtained result is that if the interconnection matrix T of the neural system satisfies that - T is an H matrix with nonnegative diagonal elements, then the neural system is absolutely exponentially stable(AEST). The Hopfield network, Cellular neural network and Bidirectional associative memory network are special cases of the network model considered in this paper. So this work gives some improvements to the previous ones.

NECESSARY AND SUFFICIENT CONDITIONS FOR THE ABSOLUTE STABILITY OF DISCRETE TYPE LURIE CONTROL SYSTEM

In this paper. it is discussed that the absohue stability for zero solution of thediscrete type Lurie control systmin which the nonlinear function f(σ) satisfying conditions as followsIt gives the necessary and sufficent conditions for the absolute stability forystem (I) under conditions (2).We also obtain the sufficient criteria for absolutesiability of the simplified system of (I) under conditions (3) .

NECESSARY AND SUFFICIENT CONDITIONS FOR THE ABSOLUTE STABILITY OF DISCRETE TYPE LURIE CONTROL SYSTEM

In this paper. it is discussed that the absolute for zero solution of the discrete type Lurie control systemin which the nonlinear function f(σ)satisfying conditions followsIt gives the necessary and sufficient conditions for the absolute stability for system (1) under conditions (2).We also obtain the sufficient for absolute stability of the simplified system of (1) under conditions (3) .

LMI approach for absolute stability of general neutral type Lurie indirect control systems

This paper deals with the problem of the absolute stability for general neutral type Lurie indirect control systems by Lyapunov method and linear matrix inequality （LMI） technique. Delay-dependent sufficient conditions for the absolute stability are derived and expressed as the feasibility problem of LMI, which can be easily solved by Matlab Toolbox. Finally, some examples are provide to demonstrate the effectiveness of proposed method.

Analysis of Absolute Stability for Time-delay Teleoperation Systems

In this paper, a new bilateral control algorithm based on absolute stability theory is put forward, which aims at the time-delay teleoperation system with force feedback from the slave directly. In the new control algorithm, the delay-dependent stability, instead of delay-independent stability, is taken as the aim of control design. It improves the transparency of the system at the price of unnecessary stability. With this algorithm, the time-delay teleoperation systems have good transparency and stability. A simulation system is established to verify the effect of this algorithm.

Absolute Stability of Nonlinear Systems with Two Additive Time-varying Delay Components

In this paper, we present a new sufficient condition for absolute stability of Lure system with two additive time-varying delay components. This criterion is expressed as a set of linear matrix inequalities （LMIs）, which can be readily tested by using standard numerical software. We use this new criterion to stabilize a class of nonlinear time-delay systems. Some numerical examples are given to illustrate the applicability of the results using standard numerical software.

ABSOLUTE STABILITY OF CONTROL SYSTEM WITH MULTI-NONLINEAR FEEDBACK TERMS

In this paper, the absolute stability of control systems with multi nonlinear feedback terms are studied. The sufficient and necessary conditions of absolute stability are obtained. Some applied sufficient conditions of absolute stability are given.

ABSOLUTE STABILITY OF TIME-VARYING NONLINEAR CONTROL SYSTEM

In this paper the authors study two classes of time-varying nonlinear control systems. A few sufficient conditions of absolute stability of these systems were obtained by means of classical analysis and the analogue of the variation of constants formula of nonlinear systems. Moreover, they gave some sufficient conditions of absolute stability in Hurwitz angle for these systems.

Absolute stability of the solidification interface in a laser resolidified Zn-2wt.%Cu hypoperitectic alloy

This paper reports on laser surface remelting experiments performed on a Zn-2wt.%Cu hypoperitectic alloy by employing a 5kW CW CO2 laser at scanning velocities between 6 and 1207mm/s. The growth velocities of the mi- crostructures in the laser molten pool were accurately measured. The planar interface structure caused by the high velocity absolute stability was achieved at a growth velocity of 210 mm/s. An implicit expression of the critical solidification velocity for the cellular-planar transition was carried out by nonlinear stability analyses of the planar interface. The results showed a better agreement with the measured critical velocity than that predicted by M-S theory. Cell-free structures were observed throughout the whole molten pool at a scanning velocity of 652 mm/s and the calculated minimum temperature gradient in this molten pool was very close to the critical temperature gradient for high gradient absolute stability （HGAS） of the η phase. This indicates that HGAS was successfully achieved in the present experiments.

ABSOLUTE STABILITY OF GENERAL LURIE CONTROL SYSTEMS

In this paper, we investigate the absolute stability of the general Lurie control systems. The necessary and sufficient conditions for absolute stability are obtained. These conditions can be readily checked and are convenient in application.

NASCS FOR THE ABSOLUTE STABILITY OF LURE DIRECT CONTROL SYSTEMS

In this paper, we transform n-th order Lure direct control systems into nonlinear systems with separating variables, and induce a concept for absolute stability of part arguments. The necessary and sufficient conditions (NASC) for the absolute stability of Lure direct control systems are given and some sufficient conditions are obtained

New Delay-dependent Absolute Stability Criteria for Lurie Control Systems

这笔记为时间延期 Lurie 控制系统涉及绝对稳定性分析，非线性在一个无限的扇区和有限扇区定位了。由使用新 Lyapunov-Krasovskii 功能那把整个延期间隔切成二个子区间并且在每个子区间和介绍一些上定义不同精力功能免费重量的矩阵，某新延期依赖者要用体力地绝对的稳定性标准以严格的线性矩阵不平等(LMI ) 被介绍。获得的延期依赖者标准不比以前的保守，作为被数字例子说明。

ON THE ABSOLUTE STABILITY OF A CLASS OF INDIRECT CONTROL SYSTEMS

The absolute stability of a class of indirect control systems was studied by applying the theory of Hermitian quadratic form and Jordan normal form. The algebraic formal criteria for the absolute stability are established, and these results are new and useful.

On absolute stability of Lur'e control systems with multiple non-linearities using linear matrix inequalities

Necessary and suffcient conditions for the existence of a Lyapunov function in the Lur ’ e form to guarantee the absolute stability of Lur’ e control systems with multiple non-linearities are discussed in this paper. It simplifies the existence problem to one of solving a set of linear matrix inequalities (LMIs). If those LMIs are feasible, free parameters in the Lyapunov function, such as the positive definite matrix and the coefficients of the integral terms, are given by the solution of the LMIs. Otherwise, this Lyapunov function does not exist. Some sufficient conditions are also obtained for the robust absolute stability of uncertain systems. A numerical example is provided to demonstrate the effectiveness of the proposed method.

The Sufficient Conditions for Robust Absolute Stability of Lurie Control Systems

In this paper, the problem of absolute stability of continuous time with parametric nonlinear system uncertainty of a linear part and sector uncertainty of its nonlinear part is considered, the and sufficient conditions for absolute stability of direct and indirect control systems are presented. The corresponding results for robust absolute stability are improved.

The Absolute Stability of Several Classes of Nonlinear Control Systems

Absolute stability problem has theoretical and engineering importance for control engineering and control theory. In this paper, based on the dimension reducing method, sufficient conditions for the absolute stability of several classes of Lurie control systems are given.

Absolute Stability for Lurie Control System with Unbound Time Delays

Time delay existes widely in various real engineering systems and can result in unsatisfactory performance or even an instability of control systems. Therefore, to investigate the stability for time delay systems is of vitul importance in control theory and its applications. Many researchers have studied the stability criteria of systems with constant delay or bound varying time delay, but few of them studied large time delay or unbound time delay. Large time delay existes commonly in various engineering applications. In this paper, the absolute stability of Lurie type direct control systems and indirect control systems with several time delays are discussed. Based on Lyapunov theory, the new delay dependent absolute stability criteria are derived. In our theorem, time delays can be unbound functions, which shows that the results are less conservative than that of existed criteria.