Exoskeleton

Exoskeletons are generally powered motorized devices that are attached to the exterior of a person’s body. Two versions are common:

• lower limb exoskeletons that provide power to the hip, knee, and ankle joints.
• full-body suits that also provide power to the arms at the shoulder, elbow, and wrist joints.

Exoskeletons are being developed to serve two purposes:

• to assist people with disabilities. Most of these are lower-limb exoskeletons that help people walk. 
• to enhance human performance beyond normal capability. Most of these are military applications designed to help people carry heavy loads or move with less effort over longer distances.

Although there remains high interest in the development of exoskeletons since the first ones appeared in the 1960s, several technical challenges remain. Most exoskeletons are very heavy, and many of them are tethered to a power supply that is large and lacks the energy density to power a suit for very long. Common power supplies include batteries, internal combustion engines, fuel cells, and pressurized gas. These are generally loud and not well-suited for a covert operation. Electric motor, hydraulics, or pneumatics are often used to actuate the joints. Despite these engineering challenges, new advances in technology are being developed to overcome problems of the past. As an example, carbon and aramid fiber-reinforced composites have replaced metal, making the structure components of the suit much lighter.