Fig. 1.

Schematic representation of the hierarchical control architecture. High-level conceptional planning in the control space of the task passes the postural plan to a mid-level Joint controller. The output of the joint controller is transformed to the control space of muscle variables and serves as input for the low-level structural muscle controller, which provides stimulation signals for the muscles (red lines). Proprioceptive sensors provide feedback signals, which are collected within the periphery and are passed to the hierarchically higher located control structures (blue lines). The process of planning and controlling hereby is easier in the control space of the task due to a smaller set of control variables. The dimensionality of the signals is illustrated by single (low-dimensional) and double (high-dimensional) arrows (colour figure online)