Pneumatic actuation systems have been considered for many years as a controversial subject in the fields of automation and control. Their main advantages, such as high power to weight ratio, cleanliness, low cost, reliability, and a simple mechanism, have contributed to their widespread distribution, especially for implementation in automated production lines and industrial tools. On the other hand, the compressibility of the working media (usually air) makes it difficult to accurately anticipate their dynamic behavior. This disadvantage traditionally restricts the control development effort of open-loop applications where accurate motion is not required.

In this thesis we develop a position control of a pneumatic actuation system. By applying the nonlinear backstepping method, the controlled actuator demonstrates accurate trajectory tracking while being subjected to disturbances of a time varying external force. To prove the applicability of the method, we have implemented the controller on a test rig. The reported test results demonstrate excellent performance tracking sinusoidal and square wave reference signals. During the experiment, the magnitude of the disturbing external force varied between 250[N] to 1050 [N].

As a preliminary step for the control design, we propose a different approach to the modeling methodology of a pneumatic system. Instead of using the traditional force analysis, we derive the actuator's dynamic model based on energy method. First we define the kinetic energy and potential energy, combine them to formulate the Lagrangian of the actuator, then by using the Euler-Lagrange equation we derive the system's equation of motion.

Although we design the control based on a simplified mass flow-rate model, we include in the appendix an original and throughout methodology for its modeling. We utilize an experimental identification procedure in order to fit a three dimensional model for the mass flow-rate as a function of the input to the valve and the pressure in the ports. The method, which can be applied to other types of valves, shows a very good model correlatio