The Industrial Research Institute for Automation and Measurements (PIAP) has designed, developed and tested a novel actuation solution for the Stiff-Flop project. The previous design relying on external braiding to limit the chamber expansion caused a lot of issues with regards to position sensing as well as actuation.
Although this approach was very effective in precventing the external expansion of the module, there were a number of disadvantages. The module cross-section geometry changed under internal pressure, which influenced the behaviour of internal sensors and introduced non-linearities to the actuation system.
The solution developed by PIAP is based on a reinforcement of each chamber instead of braiding the module externally. This solution directly eliminates the expansion effect, not only the external symptoms of it. The reinforcement is based on single polyester threaded spirally around each individual chamber.
This new approach creates cham-bers that elongate, but are prevent-ed from expansion in radial direc-tion. The cross-section geometry is much more constant during opera-tion and the behaviour of the ma-nipulator is almost linear. Using the new approach, the Stiff-Flop module can achieve far greater bending angles and elongate about three times.
The passive properties of the cham-ber reinforcement have also been tested. The results show that it has almost no influence on the module shape under external disturbance. Therefore, the structure employed in the proposed solution can be easily incorporated in the new modeling algorithm.
Bending angle achieved for certain values of pressure applied for the new design
Bending angle achieved by the modules with and without individual chamber braiding when applying external force