"HAL" has two control systems which work closely together.
Cybernic Voluntary Control (Bio-Cybernic Control System)
When a person attempts to walk, for instance, the brain sends electrical impulses to muscles. when they arrive at muscles, faint bio-electrical signals appear on skin surfaces. "HAL"'s system works as described below.
Faint bio-electric signals are observed on the surface of the skin.
Power units generate torque and put limbs into action.
Thus, HAL assists the wearer with an intended movement.
Robotic Autonomous Control System
A human motion (for example standing up from a chair) can be recognized as an aggregate of several elemental movements.
It is similar to a sentence that consists of several words. For a given motion, "HAL" assembles small movements from the database, just as words from a dictionary are concatenated to form a sentence.
Using the database (which is also automatically augmented by the information that sensors collect from the body) "HAL" autonomously coordinates each motion to be assisted smoothly by power units.
Furthermore, in the case that no good bio-electrical signals are detectable due to some problems in the central nervous system or in the muscles, "HAL" can be of use through the Robotic Autonomous Control.