I'm building a quadruped and I'm not sure of the features I should be looking for in a servo motor. e.g. digital vs analog, signal vs dual bearings. Some of the ones I'm considering are here
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$\begingroup$ I'm not sure how practical this question is. Could you provide a little context and explain why you think these motors might or might not be suitable. Generally speaking questions about how to solve actual problems you face get better answers than when people think you are asking for shopping advice. $\endgroup$– Mark BoothCommented Mar 8, 2013 at 12:03
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2 Answers
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If you are not on the budget, go for the digital with metal gears. Basically, higher the torque better your bot will be. For the legged bots speed of the servo is not an issue but torque is. To be sure that servo will have enough torque, you will need to roughly calculate the mass of the bot, divide it by number of legs - 2. As during the walk two legs will be in the air and other legs need to be able to hold the mass of the bot.
Also consider how many DOF one leg will have. In 3 DOF leg systems, one servo is used for rotation of the leg and it will not be under heavy load. So that one can be "cheaper" servo. Consider that on 4 legged system you will need 12 servos. Having 4 of them cheaper would mean more money for sensors or lighter material for construction ...
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Servo technology has evolved a lot over the last few years.
You can check out this video showcasing metal servos that power Petoi open source robot dog Bittle:
https://www.youtube.com/watch?v=FRE-sp05ia8
These digital servos are coreless and have operating travel of 270°, and stall torque of 3kg*cm.
