This paper deals with the robust control problem of a pneumatic actuator subject to parameter uncertainties and load disturbances. The control strategies are based on second- and third-order sliding mode approaches. These controllers require measurements of acceleration for feedback. However, accelerometer is seldom used in practical drive systems, because of the complexity they add to the overall process as they are mounted to the load in displacement. For this, a robust differentiator via sliding mode is used to estimate the acceleration. A comparative study between the robust differentiator and a classical one is presented. Implementation results of the proposed sliding mode differentiator-controller design on an experimental set-up are given to illustrate the developments.