Figure 3. m-SPAs with three chambers-Triple Bellows. a Structure of the Triple Bellows. b Deformation geometry of the Triple Bellows with two DOFs: bending relative to the ground and rotation above the z-axis. c Equivalent section force diagrams of the Triple Bellows. d Working flow chart of DIDO. When the conditions along the arrows are satisfied, the actuator moves to the next stage. e Working flow chart of IEAR. f Experimental pressures and theoretical pressures of DIDO and IEAR in 0-3 s. \(p_{low}\)= 10 kPa, \(\Delta p\)=10 kPa. g Steady-state actuation frequency with \(p_{high}\) from 50 to 100 kPa. h Steady-state energy consumption per cycle with \(p_{high}\) from 50 to 100 kPa.