Solution of equation (10) at switching levels S_L = 0.05 and S_H = 0.95, for dimensionless parameters α = 0.05 and β = 0.5. This solution is not optimal for the switching level S_L = 0.05. a) Left vertical axis: dimensionless motion of the electrode z(t) (blue solid line) and charge q(t) (green dotdash line). Right vertical axis: voltage u(t) (red dashed line). b) U-Q cycle in dimensionless variables, showing efficiency of 70.7%.