Designs
Both actuators consist of a rigid frame, a 1-DoF joint and two antagonistic soft air bellows. The joint angle is measured using a Hall encoder. The semi-modular actuator has one pneumatic tube per bellows connected to it. When stacked, the tubes and sensor cables are led through the whole system, leading to an increased footprint if many actuators are to be stacked. The modular actuator has integrated microvalves connected to one single pneumatic supply line for the whole system. A PCB within each actuator realizes modular communication to control the valves and read the encoder. This way, the footprint remains constant for an arbitrary number of stacked actuators.
| semi-modular | modular |
|---|---|
 |  |
The actuators are (except for electronic components and screws/nuts) fully 3D-printable. They are printed using Polyjet technology, enabling multi-material printing. This way, the soft air bellows with rigid platforms can be printed. During printing, the parts are coated with a gel-like support material, which can be removed using dentist tools, followed by loosening in an ultrasound bath. The valve interfaces for integrating the microvalves into the modular actuator are printed using resin technology, as this allows better surface smoothness to achieve airtightness.
| printer | materials |
|---|---|
| Stratasys Objet350 Connex3 | VeroBlackPlus/VeroWhitePlus Agilus30 SUP706 |
| Formlabs Form 2 | BlackV4 |
| Ultimaker 3 | any PLA filament |