This report is a master’s thesis in Electro-Mechanical System Design (EMSD) at Aalborg University,
Denmark.
Daniel Henriksen designed, in the year 2010, a test bench for hydraulic cylinders. This test bench
constitutes the base for this project, with a minor modification to his design, as two servo valves, instead
of one, controlling the load produced by at cylinder. The test bench had at the beginning of the project,
not yet been operational and different electrical circuit boards where needed to be designed, documented
and manufactured.
A full system model was developed based on fluid-mechanical expressions. This model was incorporated
in the simulation program, Simulink. The expressions where linearised in order to develop controllers
suitable for the chosen control strategies. Satisfactory controllers where developed and the performance
of these where documented. To enable implementation of the chosen control strategies in the physical
setup, a control program was developed in Code Composer Studio v4. Semi-automatic execution of
experiments where achieved and a procedure on how to use the system, for friction determination, was
formulated.
Investigations, in the field of friction, have been made by studying the documented work made by recognized
scientists dating back to the sixties. The most well documented friction phenomena are presented
throughout this report, including the Stribeck effect, friction lag and hysteresis loops. Steady state and
dynamic friction models are introduced and the assumptions and simplifications made within these are
stated. The friction models presented are the Márton and Lantos model (in which the Tustin model is
used), the pressure-based model, the LuGre model and a modified Leuven model.
Experiments where conducted, on the test bench, in order to test the properties of the friction models,
which are incorporated in a developed simulation model of the full system. In order to compare the
friction models, values for respective friction parameters where derived from the data. Regrettably, no
successful implementation was achieved, but the characteristic friction phenomena was documented and
the efficiency of the test cylinder was derived.