The modeling of the neuro-musculo-skeletal control system of a cat hindlimb

A dynamical model of the neuro-musculo-skeletal mechanics of a cat hindlimb is being developed for the purpose of investigating the involuntary regulation of locomotion. The model is simplified to three joints of the cat hindlimb in the sagittal plane driven by ten muscle groups, each having response dynamics dependent on activation kinetics, length, and velocity. For sensory feedback, physiological receptors are assumed for muscle force (Golgi tendon organs), muscle fiber length and velocity (spindle primary endings), joint angle and velocity (joint receptors), and motoneuron activity (Renshaw cells). The quadratic regulator structure is proposed for the involuntary feedback controller of small perturbations of muscle dynamics and limb movement. The corresponding feedback gain matrices were computed for posture control, and their responses to perturbation were simulated. Some feedback connection patterns appear to reflect the kinematic coupling among the limb segments. It is suggested that this research can provide insight into the operation of a well-designed, intelligent control system, the mammalian spinal cord