Pneumatic Actuators vs Hydraulic. Let it Give a Little.

As I’ve mentioned previously, and as you likely thought of when you were 10 years old (I didnt, but I wasnt the smartest calf in the heard), most mechanical means of movement arent forgiving. Hydraulics, motors, whatever other actuators you use, if anything is in their path between their current position and their programmed destination, it will attempt to keep on pushing through, and if they are strong enough, will not give to a reasonable degree. In most industrial or commercial cases, this is fine. We dont want hydraulic rams on excavators giving when it hits a patch of hard packed ground. You want that beast to bust on through without a grunt. However when you want a gripper on your Mech to pick up an apple without making apple sauce, some more finesse is necessary. Sometimes you need only a little finesse. Sometimes you need a lot. Like with baby chicks. Dont hurt the baby chicks with your heartless cold robot-hands.

Anyway, air is squishy and compresses nicely for a situation like this. So a pneumatic ram, when pressed against an obstacle, will need to increase pressure to compensate for the compression of the air inside. Of course this also happens with hydraulics, but it compresses so little you have less room to work with. Of course you can have pressure sensors on the tips of hydraulics too to sense the give or pressure between your Mech’s robot fingers and the object of its pressure, but lets keep it simple and not risk the abrupt demise of your grips focus. Using air will give you a nice buffer to sense the increase in pressure in your air reservoir, and stop/adjust/keep-pressing/whatever.  The smaller your air reservoir, the less tolerance though, so this would be adjustable by your setup.

You could even have a hybrid approach, where an air bladder of some sort is within a hydraulic system to give a little of airs natural give, but then the brute force of hydraulics immediately behind

 

Here is a great video demonstrating the give of air in a pneumatic cylinder (And the article in which I found it, from Make!)

 

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