Politecnico di Torino - Corso Duca degli Abruzzi, 24 - 10129 Torino, ITALY

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Prosthetic Wrist Unit

cycloidalepicyclicfrictionGearboxInformatica Tsd EnplanetaryProsthesisWrist


Active prosthesis for wrist applications. It allows rotational movements in both directions. The gearbox is the strong point of this invention, with one epicyclical stage followed by one cycloidal, with two opposite disks for mechanical balance.

Technical features

This prosthetic wrist has a peculiar gearbox, connected to a commercial electric motor: the first stage is epicyclical, working with three friction wheels, and the second is cycloidal. This latter stage employs two opposite disks (with an angle of 180° between them) with the typical shape of the cycloidal applications, and a cam shaft, to allow their alternate movement against the outer profile. The resulted transmission is robust and rigid, with low backlash, and a high ratio (264:1) compared to the weight and the overall dimensions.

Possible Applications

  • Prosthetics;
  • Robotics.


  • High ratio;
  • Robustness;
  • High Torque;
  • Dynamic balance;
  • Low vibrations and noise.