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I'm planning the design of a wrist for a humanoid robot. I would like to choose a design that is sturdy while allowing for dexterity comparable to a human wrist.

One option that was presented to me was to use a Stewart platform. This setup appears to correctly recreate all possible movements of the human hand. My immediate concern is that this platform will use a total of six actuators which will require additional power and computational requirements. I don't want to commit to this design until I am certain that there isn't a better alternative.

Is a Stewart platform a good choice for replicating the dexterousness of the human wrist? If not, what is a better solution?

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    $\begingroup$ Can you define your criteria for "good choice"? I would be more concerned with physical size of adding 6 actuators than powering them. The power requirements should have a minimal impact as the same load will be supported by 6 actuators. What is driving your decision making process? Cost? How many degrees of freedom do you need? $\endgroup$
    – Chuck ♦
    Commented Jun 10, 2015 at 1:07
  • $\begingroup$ @Chuck Sure, a "good choice" in this case should have a minimum of 2 degrees of freedom to allow the wrist to bend up/down and left/right. The minimum number of degrees of freedom is an absolute requirement. Cost is a factor, as is the concern that this design might be better achieved in a setup that uses fewer actuators. $\endgroup$
    – Gunther
    Commented Jun 10, 2015 at 10:59

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The "best" robot wrist in terms of human analog is probably the omni-wrist by Mark Rosheim. It has a large range of motion, and does not have singularities or gimbal lock that plague other more conventional wrists. However, it is fairly complicated mechanically, and thoroughly patented i believe.

The book Robot Evolution: The Development of Anthrobotics by the same author has a good discussion of human analog robotics design.

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  • $\begingroup$ Thank you. The design of the omni-wrist seems to be a much better method then using a Stewart platform. $\endgroup$
    – Gunther
    Commented Jun 11, 2015 at 12:10
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Bear in mind a Stewart platform has six degrees of freedom - yes it does reproduce the main motions of the human wrist, but it adds extra ones such as the ability to change its overall length. There is (I would guess) additional complexity in building one - finding suitable compact actuators and linkages, additional work to control its path, perhaps robustness.

If your objective is just to get a simple arm working, I would look for a more conventional three axis design. However the Stewart platform idea does add extra features - those extra degrees of freedom - and might be seen as a more novel concept.

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  • $\begingroup$ Great point about the extra degrees of freedom. This is something to consider as the Stewart platform will also allow the wrist to extend. This was not a requirement, but it might not subtract from the robot's capabilities. $\endgroup$
    – Gunther
    Commented Jun 10, 2015 at 11:04

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