Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Electric motors as muscles?

  1. Apr 22, 2008 #1
    Is it possible for electric motors to compare to the strength of human muscles, in terms of power-to-weight ratios? That is, with the proper engineering, is it theoretically possible? I don't see why not, simply increasing voltage increases power, if the heat generated is a problem, can't the motor be engineered to withstand the temperatures? Or does it have something to do with how muscles can vary torque/speed at will but motors can't?

    Thanks :)
     
  2. jcsd
  3. Apr 23, 2008 #2

    stewartcs

    User Avatar
    Science Advisor

    Although I'm not 100% sure, I would imagine that as far as power-to-weight goes the answer would be yes. However, as far as efficiency goes, the answer is no.

    CS
     
  4. Apr 23, 2008 #3

    wolram

    User Avatar
    Gold Member

    I think it is possible but more complex, using a motor for a gripper instead of a pneumatic or hydraulic actuator for example.
     
  5. Apr 23, 2008 #4
    The Japanese have some robots that mimic many of the muscles of a human, and can even run. I think Aibo is one, and it's using only electric motors.

    It's got a box on its back though, probably batteries taking too much weight in it. So while electric motors may be very energy efficient, probably more efficient than muscles, the energy storage technology at present is inferior to that of a living organism.
     
  6. Apr 23, 2008 #5

    wolram

    User Avatar
    Gold Member

  7. Apr 23, 2008 #6
    I don't know if i can agree with the efficiency of muscle.
    animals and humans consume one hell of a lot of matter to generate power.
    average of 3 meals a day and that is just to sustain a lifestyle of sitting at a desk and moving your fingers (obviously wrt humans and not animals. heh.)
    As soon as you talk about physical labor the food requirement increases dramatically.
    Then there is the water requirement.
     
  8. Apr 23, 2008 #7

    Mech_Engineer

    User Avatar
    Science Advisor
    Gold Member

    But how much energy is that really? A normal human consumes about 3000 calories a day, which is only about 12000 joules. Physical labor requirements can push that energy requirement as high as 8000 calories, or 33 kJ.

    If my calculations are correct, a 100W lightbulb can consume 33KJ in less than half an hour.
     
  9. Apr 23, 2008 #8

    stewartcs

    User Avatar
    Science Advisor

    I've always been under the impression that the human body is more efficient. Here is a quick link comparing humans to cars, for example. Not sure if it is considered a reputable source though.

    http://recipes.howstuffworks.com/diet1.htm


    However, this paper offers some good insight to the mechanical efficiency of human muscles.

    CS
     
  10. Apr 23, 2008 #9
    You can survive quite a lot of days without eating regardless of body weight, if you consider only muscles. Surviving is another issue, it is related with the inner stability of the human body or let say sustainability, therefore if we isolate the muscles for the discussion they are incredibly efficient. Also the brain makes them more efficient if you consider walking for example. The argument might be over repeatability or let say durability. Then things obviously change.
     
  11. Apr 24, 2008 #10

    Mech_Engineer

    User Avatar
    Science Advisor
    Gold Member

    Overall, I would say that from a net power/weight standpoint some motors can equal the performance of human muscles. From an power/energy input standpoint, human muscles are more efficient but also more affected by number of repetitions and duty cycle.

    Another problem is that motors are not inherently linear in their application of power; as a general rule motors are rotational, which means you have to have a special linear stage to convert the motor's angular speed and torque into linear speed and force. This would of course be subject to certain efficiencies based on the type of stage used. It also adds a significant amount of weight to the motor assembly and could possibly make it such that human muscles are able to put out more linear power per pound than a motor/stage assembly.
     
  12. Apr 30, 2008 #11
    i recently heard of technology that is still in research and development phase.
    this is a synthetic material similar to plastic, but biobased that expands and contracts with electric pulses.

    the following is from Science Daily article 'Biobased Plastic Flexes Its Muscle'
    i could be grouped into large masses with similar construction to the human muscle and used in advanced robotics
     
  13. May 2, 2008 #12
    The 'Calorie' commonly quoted in a food context is actually a kilocalorie.
     
  14. May 2, 2008 #13
    That one is well known for dumping unsubstantiated "words of wisdom" under a false air of authority in mechanics, but his new degree in biology and associated wisdom is an impressive development indeed.
     
    Last edited: May 2, 2008
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Electric motors as muscles?
Loading...