Human Standing Balance System Modeling And Research Of Evaluation Methods For Balance Ability

Quantitative evaluation of standing balance ability is the important scientific basis of assessment, diagnosis and treatment for standing disorders. This paper focuses on the quantitative evaluation strategy of standing disorders’ balance ability. For the defects of existing in balance evaluation method such as insufficient sensitivity, high rate of misdiagnosis, and less clinically applicable population, this paper proposes a new body standing balance quantitative evaluation strategy. This research applies a continuous sinusoidal acceleration motion excitation on the planta, to interfere equilibrium standing state of the subjects. The direction, amplitude and frequency of motion excitation is controllability, and it will be beneficial to the standards development and quantitative analysis of the evaluation method. The main works of the paper are as follows:Firstly, for the issue that there is a larger noise in the signal of body motion obtained in static experiment, this study constructs a human dynamic standing balance evaluation system, which includes six degrees of freedom motion platform, platform motion acceleration sensor, force platform and joint angle sensors and other devices. This research applies the continuous sinusoidal excitation motion on the plantar to increase motion range of the statically standing body, and it solves the problem of low signal to noise ratio. Meanwhile, this method overcomes the psychological negative impact with using a pulsed stimulation motion on the body’s planta, which is conducive to get an accurate motion information analysis of the human standing balance ability. The paper introduces the performance parameters of the equipments, and it shows that the human body standing balance ability evaluation test system can provide reliable experimental environment for evaluation of the body standing balance ability through analyzing experimental data.Secondly, for the complex biological control issue of the human standing balance, the biological functions of central nervous system, vestibular organs and skeletal motor system are deeply analyzed in the paper, establishing the analytical models of relevant organs, and compositing the analytical mathematical models of the human standing balance. By simulation results to estimate the body movement data, the paper analyzes the difference of the regulating balance approaches when the body stands statically and under external excitation, and the affections of the posture characteristics in the process of the balance adjustment by the human physical parameters. The result lays the theoretical foundation for the methods, which is as the quantitative evaluation of standing balance ability by quantifying the characteristics of human motion.Then, for the issue that it is difficult to determine incentives amplitude of sinusoidal motion of movement platform. This study proposes the approach, which is to establish the identification model for the body maintaining balance system, to estimate the sway data when the body under external disturbance. And then the security range of body to withstand external disturbances can be obtained. Based on the T-S fuzzy model identification principle, an identification model for the standing maintaining system is established. For the problem that the initial value of clustering during the model training have major influences on fuzzy C-means clustering method, the artificial bee colony optimization algorithm is used to improve the distribution of clustering initial value. The training efficiency of fuzzy model is improved. Based on the model, the standing balance adjustment data of different subjects are obtained and the safe amplitude ranges of the motion platform can be calculated, which is as the guidance parameters in practical application.Finally, for the defects of existing balance evaluation method such as insufficient sensitivity, and less clinically applicable population, the joint angle sensors are used to obtain the body standing balance adjustment data of the ankle, knee and hip. The nonlinear characteristic variables including largest Lyapunov exponent, correlation dimension and approximate entropy are used as the quantitative parameters of human standing balance ability. The corresponding static standing balance characteristic values of the youth, the olds and patients with post-stroke are calculated. From the perspective of balance standing performance under the excitation of platform, the young people are divided into stable and unstable groups, and the corresponding characteristic values of the two groups are calculated. By the power spectral density, the mean and one-way analysis of variance, the evaluation effect of nonlinear characteristic quantities is analyzed. Sinusoidal stimulation applied to the plantar makes the values of body balance adjustment feature quantity increase, and the body’s balance adjustment movement features more obvious. Through the largest Lyapunov exponent and correlation dimension, the people’s differences of standing balance ability can be expressed.