The interaction of a robotic manipulator with unknown soft objects represents a
significant challenge for traditional robotic platforms because of the difficulty
in controlling the grasping force between a soft object and a stiff manipulator.
Soft robotic actuators inspired by elephant trunks, octopus limbs and muscular
hydrostats are suggestive of ways to overcome this fundamental difficulty.
In particular, the large intrinsic compliance of soft manipulators such as
‘pneu-nets’—pneumatically actuated elastomeric structures—makes them
ideal for applications that require interactions with an uncertain mechanical
and geometrical environment. Using a simple theoretical model, we show
how the geometric and material nonlinearities inherent in the passive mechanical response of such devices can be used to grasp soft objects using force
control, and stiff objects using position control, without any need for active
sensing or feedback control. Our study is suggestive of a general principle
for designing actuators with autonomous intrinsic impedance control.