title: Stability analysis of the lambda-model during fast elbow movements.
abstract: In control, stability insures the reproducibility of motions and the robustness to external and internal perturbations. In this short paper, the stability of the lambda-model during fast elbow movements is analyzed, and the operation regions of the unmeasurably descending commands are calculated to guarantee the stabilizing ability of the motor control system. In this system, the elbow is modeled as a pair of antagonist muscles around the hinge joint in the horizontal plane. Both extensor and flexor muscles are described by a Hill-type muscle model. The muscle activation is produced by the physiological lambda version of the equilibrium point hypothesis (EPH). Conditions for global stability are calculated analytically by the Lyapunov theory and contraction theory. The results suggest that to guarantee the stability, the descending commands R, C and mu from central nervous system (CNS) must be tuned to the muscle properties, the muscle geometry and the geometric properties of the linkage system.
authors.affiliation: School of Electrical and Electronic Engineering, Nanyang Technological University, 639798 Singapore. lanli@pmail.ntu.edu.sg
authors.forename: Lan
authors.initials: L
authors.lastname: Li
authors.forename: Zhu
authors.initials: Z
authors.lastname: Kuanyi
mesh_terms: D000328:Adult; D003198:Computer Simulation; D004551:Elbow Joint / Q000502:physiology*; D006801:Humans; D008297:Male; D008954:Models, Biological; D009046:Motor Neurons / Q000502:physiology*; D009048:Motor Skills / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D013647:Task Performance and Analysis