A novel super-twisting adaptive sliding mode control law is proposed for the control of an electropneumatic actuator. The key-point of the paper is to consider that the bounds of uncertainties and perturbations are not known. Then, the proposed control approach consists in using dynamically adapted control gains that ensure the establishment, in a finite time, of a real second order sliding mode. The important feature of the adaptation algorithm is in non-overestimating the values of the control gains. A formal proof of the finite time convergence of the closed-loop system is derived using the Lyapunov function technique. The efficiency of the controller is evaluated on an experimental set-up. (C) 2012 Elsevier Ltd. All rights reserved.