Fluidic muscle

Fluidic muscle is a tensile actuator which mimics the natural movement of a muscle. It consists of contractible tubing and appropriate connectors.

The contractible tubing is formed by a pressure-tight length of rubber hose, sheathed in high-strength fibres. The fibres create a rhomboidal pattern with a three-dimensional grid structure.

The tubing stretches in circumferential direction when an internal pressure is applied, generating a tensile force and a contraction movement in the longitudinal direction of the muscle. The usable tensile force is at its maximum at the start of the contraction and then decreases to zero in a virtually linear manner as a function of the stroke.

The fluidic muscle can only apply tensile forces. The size of the stroke which can be achieved through contraction is about 25% of the total muscle length. External tensile forces permit maximum pretensioning of 5%.

For the fluidic muscle, not only the force, but the stroke directly depends on the current working pressure. Positioning in the stroke direction is very easy. Instead of a displacement encoder which has to be integrated parallel to the drive, a pressure sensor can be installed at a favourable position. By allocating pressure and stroke, almost any number of positions can be realised.