It's been a while since the last time I wrote about the A3 project. It has recently morphed into the Prometheus Arm project, in which I work with a friend of mine. What motivated the change? Take a look yourself:
I must admit it. I can't resist Iron Man. That's just it, and now I want to contribute. My friend Pablo and I are now working on a better design of the arm, balancing between cost, simplicity, repairability and functionality, and will try to contribute to Limbitless' project with it.
Talking specifics, we are making the first tests with a 3d printed, improved version of the antagonistic mechanism that allows for better, finer and simpler adjustment of the joints.
The main problem with antagonistic actuation is obviously the cost. Since you are basically doubling the number of actuators, the costs goes up very quickly. However, a good mechanical design can simplify things a lot. I still don't have it fully documented, but I will soon post a method that uses symmetric cinematic chains to factor out some actuators while retaining the basic functionality. Reducing the number of actuators necessarily reduces the number of degrees of freedom (which originally was two for each joint), but I think this is a good trade off if all you are loosing is strength degrees.
More specifically, the tension regulators are shared among similar joints, so they will all be adjusted at the same time, but individual elasticity and torque tolerance is fully kept. I don't think the use-case for trying to exert different amounts of force with each finger is much common, so it is definitely worth the cost drop.