Modeling and flatness based feedforward control of a hydraulic axial piston pump

Automation in hydraulic applications increases a lot. This yields to higher requirements for the dynamic properties of the supply for the hydraulic energy consisting of pressure and volume flow. For this purpose, firstly a detailed mechanical model of the axial piston pump including a torque balance on the swashplate as well as as the modeling of the hydraulic actuation is performed, which is then used for a model based calculation of a feedforward and feedback controller. The nonlinear model is simplified to obtain a differentially flat output to implement a flatness based feedforward controller and to use linear control techniques in the flat coordinates. For the feedforward controller a smooth trajectory together with its derivatives must be calculated. The feedforward and feedback controller together with the trajectory generation is implemented on the real system and the performance is reviewed. At first, the performance is validated with a physical simulation model and the tracking behaviour of the system output to a reference trajectory is examined. Then, the behaviour of the real system is examined and results for exemplary movements are illustrated. These results show a shorter delay-time for the supply volume flow due to the feedforward controller and a shorter settling time for the error of the system pressure to a given reference due to the model based feedback controller. The volume flow supply is more even hence the movement of the equipment is smoother.