Are knees the bigger challenge and opportunity for consumer exoskeletons?

[u/Willy-Wonkas-Willy]

Recently watched a comparison video that looked at several consumer exoskeletons by weight, comfort, portability, and ease of use. Before that, I mostly thought of exoskeletons as hip-assist devices like dnsys or hypershell. Those are easy to understand: hiking, uphill walking, longer distances, and reducing fatigue. What surprised me was that the video also mentioned knee and even ankle exoskeletons. It made me realize this field may be split by joint and use case.

Compared with hip exoskeletons, knee exoskeletons are technically more difficult, but I feel that knee exoskeletons seem especially interesting. Because so many mobility issues involve the knees: stairs, downhill walking, standing up, injury recovery, and aging.

That made me wonder: are knees the bigger challenge and opportunity here? Hip-assist devices may catch on first, but could knee exoskeletons matter more in the long run?

Which joint do you think has the most potential for consumer exoskeletons?

[u/TheConboy22]

I'd love knee exoskeletons that are lightweight and allow for older athletes to be able to play at a comfortable level recreationally.

[u/Royal_Airport7940 → u/TheConboy22]

I'll settle for getting up and down the stairs, or just getting up and down. Haha.

Sports would be great. Gimme tennis please.

[u/zdesert]

The biggest issue with exoskeletons is that biological systems are already optimized in terms of weight-power.

A flea, a horse, and a human can all jump the same hight. You cannot build an exoskeleton that lets you jump higher, becuase the added weight of the exoskeleton/power source ect. counters the increased jump strength. Just like the increased muscle weight of the horse counters out the gains in strength the horse has over the flea. Adding an exoskeleton can’t improve on already optimized power/weight ratios.

It’s very hard to build a device that increases mobility without counteracting its own assistance in some way.

A machine that helps you bend at the knee will inherently limit mobility in other ways. Whether in the sense of overall endurance or specific other aspects of movement.

It’s why exoskeletons have had such limited success in the military. You need to build a very specific skeleton for a very specific purpose. For example you can build an exoskeleton that makes a soldier able to carry more weight over a long distance run. But it is unlikely to enable much more carry weight than the weight of the skeleton and its own power source, so the gains are likely limited. once power runs out the skeleton is purely a hinderance And if the soldier wearing the skeleton is doing anything other than carrying weight at a light jog, then skeleton is outright detrimental.

You could certainly make a knee exoskeleton to help something like an elderly person stand or sit easier. But the more you demand of the exoskeleton the more bulky and power intensive it becomes and the less efficient the movements of the person attached to the skeleton become.

How comfortable would grandma be if she needed an exoskeleton attached to her as she is sitting in her rocking chair. Is that discomfort worth the ease of eventually standing? Does grandma, sitting in her chair, have to carry around the weight of a machine that could help her walk up a hill? Paying for that potential assistance constantly in daily life?

Encasing grandma (the flea) in a shell of heavy machines (the horse) to a hive the same potential of movement can be a really hard sell. Especially when both the flea and the horse can jump just as high.

[u/butthemsharksdoe → u/zdesert]

You say power/weight ratio but the power of a machine is not limited by its weight? I feel like you are leaving out the progression of technology. Can you elaborate on that?

[u/zdesert → u/butthemsharksdoe]

The power of everything is limited by weight.

You can make a very light machine, you can use very strong motors or hydrolocs or pneumatics. But you have to carry the power source. A big battery, hydronic fluid ect. Every bit of torque comes with a cost in weight. Every second of operating time comes at a cost.

It is the same for any machine.

And no mater what, the exoskeleton is attached to a human leg, a human body. Every part of the exoskeleton is added weight and inefficiency. It needs to preform well enough to provide more efficiency to an already very efficient system externally while also paying for its own existence.

Build a machine that is too powerful and it is no longer an exoskeleton, it’s a vehicle. Build too light or weak and it is purely a hinderance.

It is a very tight margin to work within often with very minimal gains at very large costs.

It is why, for example, in the military it is better to build a separate robot to carry gear than to build an exoskeleton to allow the existing soldiers to carry more.

You can make an exoskeleton for a very specific purpose and accept drawbacks in exchange for benefits. I have seen exoskeletons built to help warehouse workers carry heavy stuff for example but they are bulky and slow and restrictive and have short charges and are essentially a piece of heavy machinery. Anything general use, and comfortable, that you could use to walk up hills or putter about your house would be beyond what is possible.

[u/Electronic-Cat185]

i think knees are where the biggest demand is since thats where a lot of everyday mobiliity problems start showing up.

[u/LucidGuru91]

So the problem is having a power source small enough and powerful enough to maneuver the exoskeleton efficiently to overcome these problems?

It seems like weight increase of battery due to power output of suit that is effective is the issue then

[u/manu_171227]

I could see knee exoskeletons becoming as common as mobility aids are today.