electromagnetic lineair actuator
- Hello everyone,
mostly walkers have rotating motors, but their movements are linear
(they don't have wheels). Let's forget for a moment (to keep it
simple) that legs of walkers have rotating joints.
When linear movements are used for robotics, it mostly isn't for
legs. When a linear movement is necessary mostly mechanisms like
Timing belt/pulley, spindle/nut or a gear along a guide are used.
Thinking about factors like speed ratios, mechanical friction and
backlash we don't need to have much imagination to understand that
mechanisms like these are not very power-efficient. Moreover, when
the mechanism is more complex (more gear steps etc.) the mechanical
rigidty is smaller (as much as important as power efficiency).
Until so far nothing new, you will think. In some scientific areas
experiments are done with direct linear movement. For instance the
CWRU made a hexapod Robot III (check it out:
This Robot III is an impressive cockroach-like hexapod. Every leg of
this hexapod has 4 segments that gives all the necessary degrees of
freedom. Really im-pres-si-ve (the opinion of someone with a
mechanical background)!! The thing can correct its attitude when
absorbing shocks and accelerations (some sort of force-feedback
mechanism). The linear movements are realised with pneumatic
Ah, there we are, you think. And, yes, as far as I can judge it,
Robot III is not stand-alone. It needs a "lifeline" with compressed
air. So it doesn't tow around it's own little compressor cart.
(wouldn't make a realistic cockroach anyway)
Another approach is that of air muscles. Air muscles are a kind of
strengtened rubber tubes that will get shorter when inflated with low
pressure air (see for instance
8.html and http://www.imagesco.com/catalog/airmuscle/AirMuscle.html).
But again a compressor is needed.
But now the electronics domain. I must say, with intervals I follow
the discussion about robots on the internet and haven't seen many
instances of the use of electromagnetic linear actuators. Is this
strange, or is there a logical explanation for this? I assume the EMC
shielding of these devices will ask a lot of attention. Further, to
analyse a leg with a few segments, springs and
electromagnetic "cilinders" will ask a lot of control engineering.
But still, my doorbell has coil magnet lineair actuator and I removed
a few of these things from an old cassettedeck. Although those ones
need a high voltage (24V), can't they be made for the low voltage
domain of solar bots?
I would appreciate if someone could give me some answers. What are
the bears on the path I don't see? If there are possibilities, can
someone point out what issues can be encountered when developing
Thanks for the attention,