On railways with overhead lines, pantographs play a crucial role in electric trains. Maintaining the contact force between the pantograph and the overhead line is essential to ensure the robustness of the power supply and to minimise mechanical wear. This paper proposes an innovative pneumatic pressure-controlled active pantograph, tested through Hardware-in-the-Loop (HIL) experiments. The proposed easy-to-implement active pantograph is achieved by controlling the air pressure entering the pantograph. The controller design is based on an identified linear model, considering disturbance rejection performance and control input limitations. Experimental results show that the closed-loop active pantograph can robustly and effectively reduce the contact force deviation. This highlights the capability of designing active pantographs through pressure control and model-based design philosophy to achieve improved pantograph–catenary contact performance.