PowerWalk knee brace: powering soldiers on the go

The soldiers of today must carry batteries to power a variety of gadgets, namely “night vision goggles, radios and navigation gear”. Typically, 13 to 15 batteries weighing up to 5 kilograms are carried. To reduce the weight on soldiers’ shoulders, the company Bionic Power has put forth a lightweight knee brace, called ‘PowerWalk’. The device generates electricity from the motion of walking to power the aforementioned gadgets. A closer look at the knee brace’s design reveals its triumphs and shortcomings.

A soldiers equipped with PowerWalk

The device has a “targeted design weight of 800 grams”, much lighter than that of the batteries soldiers must carry. The majority of the weight is contributed by the PowerWalk’s gear box. To achieve the targeted weight, engineers are designing the gear box so that it has the least possible width. With low width also comes greater comfort to the soldier, as the gear box takes up less space and interferes to a lesser extent with the soldier’s motion.

The PowerWalk produces electricity from the motion of walking. More specifically, Bionic Power’s CEO Yad Garcha explains that the “negative energy that occurs in the hamstring as the human leg decelerates or brakes” is converted into electricity. In lieu of being dissipated as heat, this energy is harvested by the device and converted directly into electricity. To get a quantitative sense, a soldier walking at a normal pace can generate “an average of 12 watts of electricity”. One hour of walking can produce enough energy to “fully charge four mobile phones”.

Graph of power generated at various timeframes

Stealth can be a necessity during certain military missions. PowerWalk’s metal and plastic gears render the device quiet during motion. Garcha has plans for the future as he says that “eventually, we’ll also introduce a mechanical clutch” that will fully disengage the device and ensure total quietness.

Despite its accomplishments, the knee brace faces a few trade offs. While doing full squats, “thighs expand by an inch to an inch and a half”. The rigid structure of the brace prevents soldiers from performing exercises such as this. To address this problem, engineers at PowerWalk are working on finding a way to make the brace fully compliant with the body’s movements. Another drawback to consider is that in rough terrains, the device could be damaged. Sometimes, soldiers operate in mountainous or icy regions. Any physical contact between the gear box/brace and the environment could lead to broken parts. Thus, the PowerWalk must be tested in extreme military environments to discover its limits.

Garcha has stated that his company is receiving funding to research how PowerWalk can “assist the soldier in carrying heavy loads”. If the brace is modified to incorporate load-carrying assistance, the risk of the brace doing damage to the body must be considered. Unbalanced forces on sensitive joints can lead to broken bones and serious injuries.

PowerWalk M-Series

The brace and gear box of the PowerWalk

The energy converting mechanism of the PowerWalk also faces a few trade offs. The distribution of power across the soldier’s body remains a challenge. One option is wireless power distribution. However, Garcha has ruled out this option possibly due to its inefficiency and need for more hardware, increasing weight. The option that remains is using wires to connect PowerWalk with gadgets. Once again, wires running over a soldier’s body could restrict his motion or cause discomfort. Also, PowerWalk is not applicable to soldiers travelling in vehicles. For example, the device would not have be useful “in urban settings” like Iraq, where soldiers “mostly traveled in personnel carriers”.

To conclude, the integration of PowerWalk in the military could lead to fewer load and great cost savings. If a soldier performs 200 missions per year, “the cost savings add up to $27,000 per soldier per year”, according to Bionic Power. Nevertheless, additional fine-tuning with respect to design and power distribution is required to consider PowerWalk ‘battle-ready’.

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