Fig. 2
Block diagram of the model used in the simulation study. The feedback model included the neural controller with transmission delays (τ1, transmission time delay and τ2, feedback time delay) and the neuromusculoskeletal (NMS) torque-generation process, as well as mechanical stiffness (K) and passive damping (B) to control the inverted pendulum. The inverted pendulum was used to describe the mechanics of the quiet sitting. m is the moving mass, h is the height of center of mass (COM), and I is the moment of inertia of the inverted pendulum. K P and K D , are proportional and derivative gains of the proportional-derivative (PD) controller, respectively, used to emulate the neural controller. An inverted pendulum model of quiet sitting is represented, where y COP is the center of pressure (COP) position, θ is the sway angle, and g is the acceleration of gravity. Gaussian random noise was inserted into the system to drive the simulations