Our bloggers look at a flexible lower limb robotic exosuit, which could help firefighters and others who have to carry heavy loads.
The lower limb suit developed by researchers at Harvard University, reduces metabolic demand, which leads to fatigue and decrease in performance (image: Harvard University)
Soldiers, first responders, and even athletes all face physically demanding tasks while walking, owing to having to haul 45kg worth of gear and equipment. Carrying heavy loads alters the biomechanics of walking, which leads to an increase in metabolic burden. The handling of heavy loads requires higher muscle activation in the lower limbs, which is required to sustain the load and balance the joints; there is an increased metabolic demand, which leads to an early onset of fatigue and a decrease in performance. Carrying heavy loads also leads to an increased risk of injuries such as foot metatarsaglia (foot pain), stress fractures, and back strains.
Researchers from Harvard University have developed a flexible lower limb robotic exosuit, which reduces the metabolic demand by decreasing energy expenditure by approximately 7.3 per cent. The exosuit significantly reduces the work done by the lower limbs without negatively affecting step frequency or length.
The exosuit is made from soft, functional textiles woven together into a piece of smart clothing and created to be lightweight – 6.6kg – with most of the mass being worn at the wearer’s centre of mass, leading to minimal impact on the energetics of gait.
The suit comprises a waist belt, two thigh pieces, and two calf motors. It works by transmitting moments around the biological joint axes via flexible cable-based transmissions and textiles that anchor the body. The straps positioned around the lower half of the body contain a low-power microprocessor and a network of supple strain sensors that act as the ‘brain’ and ‘nervous system’ of the Soft Exosuit. These sensors monitor various data signals continuously, including suit tension and the position of the wearer. It does this while minimally influencing the wearer’s natural walking kinematics and is only active when walking is detected.
The researchers studied the biomechanics and physiology of human walking (image: Harvard University)
According to Connor Walsh, an assistant professor at Harvard’s Wyss Institute for Biologically Inspired Engineering, this programmable suit can act in parallel with the body’s tendons and muscles, ultimately mimicking the way in which the body moves.
Previous models of the exoskeleton suit have attempted to achieve the same goal of making load carriage easier. Some suits have tried to reduce the effort required to carry heavy loads by providing a parallel load path to the ground, while others have applied torque directly to the wearer’s joints. While the rigidity allows for transmission of high forces, it takes away from the main goal of the suit, which is to provide locomotion. What makes this model, created by the Harvard research team, distinct from these previous models is that it provides a soft frame compared to the rigid frames of previous models.
The exosuit has been worn and tested on uneven terrain, avoiding obstacles - the system is fully in sync with the human wearer (image: Harvard University)
While rigid suits may be ideal in some cases, the flexibility provided by this newer model would be advantageous for first responders who have to carry heavy equipment in the face of emergency. This suit would allow for maximum flexibility with minimal metabolic cost; first responders would be able to carry heavy equipment without having to worry about rigidity or stiffness, while at the same time reducing their risk of injury. Additionally, first responders would not tire as quickly, thus increasing their ability to perform pertinent tasks for a longer period of time without tiring.
The exosuit has a valuable role in the industry of crisis response by enhancing first responders’ physical abilities to better withstand and adapt to the demands of an austere environment.