Energy Efficient Exoskeletons

There are endless examples of exoskeletons that humans interact with on a day-to-day basis. Beetles, scorpions, crabs, and snails all exist within the protective confines of their shells, rather than bones. Movies and video games have characters that don superhuman suits to battle the forces spawning against them.

Each of these instances provide evolutionary defensive measures or unrealistic situations in which an exoskeleton is necessary. However, not every exoskeleton must be an all-encompassing body armor or war tactic. Imagine a factory worker squatting numerous times to lift heavy equipment, a firefighter scaling the stairs of a burning building, military personnel marching up the side of a mountain, or even a medical patient being provided the ability to learn how to walk for the first or second time.

A minimalist exoskeleton may be able to provide supportive services to daunting tasks that require repetitive kneeling, squatting, climbing, and/or lifting heavy loads, improving strength, endurance, and safety. In short, every productivity goal is met: do more, with less effort and/or in less time.

Lockheed Martin has been at the forefront of exoskeleton technology. One of their more well-known research projects is the exoskeleton called the H.U.L.C. (the “Human Universal Load Carrier” pronounced “hulk”). This supportive, lower-extremity suit is powered by hydraulics and electric actuators, operated by a flexible and expandable on-board microcontroller. This all takes much more power than one would imagine to operate. The untethered support suit may only operate for 96 hours at most. While four days may seem like a suitable lifespan, that is with the eight lithium-ion batteries stored on the lower lumbar. This added weight and size does not help in the design for prospective clients.

There are numerous other use case examples: a knee-focused exoskeleton to assist lower extremities (reduced size means reduced core benefits, such as less actuators). Battery-powered walking-assisted medical exoskeletons that may be used for cerebral palsy and trauma patients, and even full exoskeleton suits that turn the user into a personal forklift. Although the products seem simple, there is a reason you do not pass them while walking the aisles of your local market. Both the poor battery life and cost of parts make these products extremely expensive compared to the benefit they will return.

Battery life and power management are not new hurdles to overcome in the realm of battery-powered exoskeletons and gear. Exoskeletons use large and/or multiple batteries, and have short usage time per charge. Getting the energy out of the batteries to the actuators can be challenging. The power used by the exoskeleton’s electric motors require thick, heavy power harnesses to ensure there is no risk to safety and adequate current is transferred.

Innovations like these are ideal fits for our Cable-based Capacitors (CBC) to improve battery life by complementing to the energy storage system. The actuators use electrical energy in pulses for each electromechanical movement made. By storing and then releasing this energy at the actuator, rather than constantly drawing from the batteries, efficiency improves, and battery life will be prolonged. This means that the system could do more, last longer, or designers can achieve the same performance they have now using fewer batteries. Also the life of the battery would have a longer operating life too. In addition, Capacitech’s CBCs are mechanically flexible, making them easier to work into the design. One area to consider is integrating the CBC, a supercapacitor, into the wiring harness.

Capacitech’s Cable-Based Capacitor (a flexible supercapacitor) can be installed off circuit boards and as part of the wiring infrastructure. This helps engineers and designers pack more energy storage capability into their products, without having a tradeoff to design, function, etc...

Flipping the battery life issue on its head, picture the benefits of using the exoskeleton to prolong the life of batteries by recharging them as you walk? That is what PowerWalk Kinetic Energy Harvester by Bionic Power does.

The energy harvested from flexing the knee is able to produce 10-12 watts of power, similar to regenerative braking within a hybrid car, which may then be used to assist recharge batteries. In these cases, this is more efficient than carrying more batteries. Cable-based Capacitors can help capture more of that energy and condition the power (smooth power surges) to improve battery charging.

An electric actuator can draw a current much higher on start-up than during continuous operation. CBCs can provide this inrush current until batteries can play catch up, protecting them from damage and increasing the lifespan. On top of that, after the actuator is warmed up, CBCs can help recover energy during braking and when idle.

Many of us can relate to having injuries that limits movement or the ability to lift and move things. Even though exoskeleton is evolving at a rapid pace, it may still be quite a while before one can get a prescription for an exoskeleton from a doctor or rent one from a business. When exoskeletons are ready for commercial availability, it is a good bet that it will be with the help of Capacitech Energy and its wire-shaped supercapacitor.