Experimental test data for hydraulic/pneumatic muscle operation

McKibben muscles have been shown to
have improved stiffness characteristics when operating hydraulically. However,
when operating pneumatically they are compliant and so have potential for safer
physical Human Robot Interaction (pHRI). This research explored a method for
rapidly switching between pneumatic and hydraulic modes of operation without
the need to remove all hydraulic fluid from the actuator. These data were
obtained from experiments performed on a single McKibben muscle acting on a
load with gravity providing a restoring force. The data show the results
obtained when applying step and sinusoidal control inputs to a McKibben muscle
when operating both pneumatically and hydraulically. The graphs show the
difference in behaviour in the two operating modes. The experimental data also
show how the muscles react to disturbance loads and how a damping effect is
produced as a result of the hydraulic mode of operation.