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How can I control hydraulic pistons using myoelectric (muscle signal) sensors ?

Hello, this is my first post. I've run into a problem. I've designed an exoskeletal armor system, yet don't know how to control it. I have an approximate idea; using myoelectric sensors on the major muscles of the arms, torso, and legs, it will track and replicate muscle movement patterns through hydraulic pistons in the suit. Problem being; I don't know how to activate the pistons using this method. I don't even know if you can attach the pistons to a micro controller the sensors are hooked up to. Any information that may help is appreciated. I am in no way a professional after all, and this is my most ambitious design yet. Certainly to be the most complicated, expensive, and tasking build I've done too. I will upload the designs whenever possible, as I have no scanner at this time.

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How are you getting proportional feedback from the hydraulics ? I assume you have proportional control valves ?

Decoding myoelectric signals is a black art, and a lot of research is proceeding to systematise the process. I don't think its as easy as clipping on a couple of wires and getting the signal out. The RATE of nerve impulses rather than the voltage affectst the degree of contraction.

Resolving WHICH muscles are firing requires multiple electrodes and a kind of tomographic approach to signal conditioning which takes fast, DSP level hardware.
doctor31415926 (author)  steveastrouk5 years ago
You're absolutely correct, proportional activity between muscle and piston has been daunting me for a while now. My best solution to this has been measuring the signal detected by the myoelectric sensors, and using that as a sort of "power scale" for the later to be added pistons.

The problem with this being that it requires the user to flex their muscles harder for more power to be output by the piston. Basically as long as the muscle is flexed the piston will fire, but the strength of the flex determines how much output force the piston fires.

Obviously this won't work for long term usage, as the users muscles would become too easily exhausted by the constant flexing. aside from that, this method would also require them to learn to move the suit as if it "was" their body, using their muscles as a sort of go between. Thus requiring extensive training.

As for the determining of which muscles fire at what time, the sensors will be located on the muscles which need to be used. Such as biceps, triceps, and calves. When the muscle is fired, the micro controller picks up on this using the myoelectric sensor on the muscle and the appropriate piston will fire.

To be honest, I know little about the application of myoelectrics to hydraulics. If you have any recommendations or ideas, I'm more than willing to listen. After all, that is why I asked the question in the first place. : )
Trouble is, I'm not sure what myoelectric signals will convey proportionally to your hydraulics. If, as I suspect, its FORCE, then you need proportional valves like Moog's in your hydraulic circuits, and, at over 1000 bucks a pop, you aren't going to like that at all.

If you took the "easy" route, and used positional feedback, you might be able to afford the controls, but it wouldn't be that relatable to myoelectric effects.

Picking up the microvolt signals from a SINGLE muscle is very very difficult, and HAS to be done by discriminating between multiple sensors - not easy at all.

You need GOOD "instrumentation amplifiers" to stand a chance of doing this - a single op amp really won't hack it ! Try INA 101 from TI for a really good amp.

This is fascinating, not leading edge, but bleeding edge stuff you're attempting.

Steve
lemonie5 years ago
Why not start with switches and do the complicated-stuff later when you've got the basics figured-out?
E.g. you move your arm like the central handle of a joystick and it pushes switches inside the exoskeletal armor arm-system, these actuate the servo's.

L
doctor31415926 (author)  lemonie5 years ago
I can't wait to try your Roasted hot pepper sauce recipe by the way! : P
Well, I'd considered this as well, but the problem I ran into was space. I quickly discovered that the arm would need to be massive to allow room for the switches, pistons, and arm movement. Unfortunately I had to scrap that idea.
Then again if it was easy Everybody would build one.

I sincerely appreciate your input though! Thanx man!
rickharris5 years ago
Sigh! Design in general suggests you think through the whole project and try to anticipate problems so they can be resolved in a timely manner.

Effectively you want to retrofit some kind of control system onto a framework you have already designed.

I suggest you research robots - there is plenty of information on the net, Medical measurements and electronics in general.

From your question you have a BIG uphill learning curve to work through long before your ready to design a control system, allow several years of development - personal and practical.

Sorry there isn't a quick 50 word answer to your question beyond pay someone with the skills and knowledge to build it for you.

doctor31415926 (author)  rickharris5 years ago
I'm sorry, perhaps you misunderstood me. I understand that the control system must be in the framework, and have already done so. And before any further discussion, I am referring to the Myoelectric sensors and related micro controllers they are hooked into. Those Micro controllers are hooked into an on board computer that reads the muscle data and responds accordingly. Also I have already designed in the pistons, tubing, mounting for both, and the 2 necessary hydraulic pumps, as one pump won't be able to handle all the pistons.

You see, this design is odd for me because it ISN'T a robot. When I said, "I am by no means a professional" I was referring to the fact that I don't have ANY experience with anything other that robotics. However, you are technically correct, If I had no background experience with robotics, I would be completely lost on this design. However, I also would not have been drawn to a site like this one; where like minds can communicate and discuss relevant building topics, not topics like; who is more mature, You're just not able to do this for whatever reason, or who has "personal development' to take care of. But, obviously this is not such a site.

And, in conclusion; A constructive piece of advice would have been something like this. "Why are you using hydraulic pistons"? "Try those pneumatic muscles". "They are much lighter, and stronger than hydraulics". "Plus this guy hooked them up to a similar setup to yours using a micro controller"!(see link below.) I just discovered this on my own this morning.
I do appreciate your help...
D31415926.

https://www.instructables.com/id/Pneumatic-Muscles/

http://cwwang.com/2008/04/08/soft-pneumatic-exoskeleton/
We are not mind readers and anyone would assume from your question that you have an idea but no idea how to put it into action.

DARPA has been trying to do this with multi-million dollar projects for several years so that give you some indication of the complexity.

Constructive actions includes searching and looking at the related column on the right.

https://www.instructables.com/answers/I-want-to-use-nerve-impulses-from-muscles-as-a-dat/

for example.

Some information about where you are , what your experience is, and what sort of general budget your dealing with - $100 or 1,000,000 and a more specific question relating to a single issue will get you a more specific response.


http://www.picaxeforum.co.uk/archive/index.php/t-11462.html


your going to need to amplify the minute muscle signals - an OPAMP would be a good place to start

Your going to need to interface to a series of hydraulic valves so need a suitable interface for the product your using See

http://www.picaxe.com/docs/picaxe_manual3.pdf