Modeling of a Hydraulic Braking System

Sammanfattning: The objective of this thesis is to derive an analytical model representing a reduced form of a mine hoist hydraulic braking system. Based primarily on fluid mechanical and mechanical physical modeling, along with a number of simplifying assumptions, the analytical model will be derived and expressed in the form of a system of differential equations including a set of static functions. The obtained model will be suitable for basic simulation and analysis of system dynamics, with the aim to capture the fundamentals regarding feedback control of the brake system pressure. The thesis will mainly cover hydraulic servo valve and brake caliper modeling including static modeling of brake lining stress-strain and disc spring deflectionforce characteristics. Nonlinearities such as servo valve hysteresis, saturation, effects of under- or overlapping spool geometry, flow forces, velocity limitations and brake caliper frictional forces have intentionally been excluded in order not to make the model overly complex. The hydraulic braking system will be described in detail and basic theory that is needed regarding fluid properties and fluid mechanics will also be covered so as to facilitate the reader in his understanding of the material presented in this work. Overall, the scope of this thesis is broad and more work remains in order to complement the model of the system both qualitatively and quantitatively. Although not complete in its simplified form and with known nonlinearities aside, the validity of the model in the lower frequency domain is confirmed by results given in form of measurements and dynamic simulation. Static analysis of the brake caliper model is also verified to be essentially correct when comparing calculated characteristics against actual measurements, as is also the case for the static models of the brake lining and disc-spring characteristics.