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I would like to know if the energy utilized by a robotic arm is greater compared to the energy utilized by human arm. Robotic arm is essentially servo motors that use electromagnetic field to create motion while human muscles use muscle fiber compression/elongation and to activate motion. So is there any comparison study that points out the efficiency for both?

It does appear that human muscles uses far less energy as the amount of cooling required for human to move say 1km is not significant (body temperature rarely reaches 38 deg C, while motors do tend to heat up to 40 deg C for mild load. Now this is probably oversimplification hence I would like to know if there is some analysis that concludes or indicates the efficiency of the human muscle vs motor for same or similar actuation?


Based on the comments, I would like to know if there is a comparison for both based on unit energy, keeping the mass of both the actuators same.

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  • $\begingroup$ Your running example is deeply flawed. It is not comparing muscle to motor. It is comparing crappy batteries to chemical fuel. What you just did is like comparing an electric car to a gasoline car and concluding that engines are more efficient than motors since gasoline cars can travel much farther. It is, in fact, the opposite. Motors are more than 3-5x as efficient as engines, but gasoline stores 100x more energy than batteries, so the higher efficiency of motors means nothing. $\endgroup$
    – DKNguyen
    Aug 7 '20 at 21:52
  • $\begingroup$ Does the robot arm have more mass than the human arm? $\endgroup$
    – Solar Mike
    Aug 8 '20 at 8:01
  • $\begingroup$ @DKNguyen, yes you are absolutely right. I actually indeed referring to actuation, given same energy is applied to both. $\endgroup$
    – gfdsal
    Aug 8 '20 at 19:40
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    $\begingroup$ @gfdsal If I recall, Stephen Vogel's book Comparative Biomechanics says that pound for pound, motor and muscle are pretty similar in terms of power density. So motor and muscle that are capable of the same power output will weigh the same, except that the muscle will be larger and the motor will be smaller due to difference in density of materials, but they will be of similar weight. There was no mention about input power requirements and therefore no mention about efficiency. I am unsure if this takes into account temperature since steel can run a lot hotter than flesh. $\endgroup$
    – DKNguyen
    Aug 8 '20 at 22:22
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    $\begingroup$ @gfdsal You should take a look at that book. It also talks about our use of pure materials versus biology's use of composite materials and the advantages and issues with both of which the temperature thing I mentioned is part. What I told you was in the Google books preview version of it. I've never gotten my hands on the full book. $\endgroup$
    – DKNguyen
    Aug 8 '20 at 22:26

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