 Simulink in barebones form not-well suited for simulating networks/nodal systems ◦ 1) No sense of bi-directionality ◦ 2) No notion of ‘nodes’ ◦ 3) Energy conservation has to be maintained via algebraic constraint blocks in each sub-unit  Can be done….but very messy, difficult to expand

 Approach ◦ Solve network state in one custom block  Pros ◦ Better understood on how to get the correct solution  Cons ◦ Not well-suited for ‘group’ approach ◦ Code interface to solver block could get messy fast ◦ Hard to expand to new sub-systems

 Approach ◦ Use Simulink ‘Simscape’ Libraries  Pros ◦ Let Simulink do the book-keeping for energy conservation, flows, network state, time etc ◦ Graphical components for building networks  Cons ◦ Built-in Hydraulic domain assumes constant temperature ◦ New thermo/hydraulic domain (and accompanying components) have to be written/re-written

 A simulink package to model physical domains and networks  Based off of ‘Bond-Graph’ Theory ◦ Physical dynamic systems can be abstracted into networks in which:  1) There exists “Flow” variables  2) There exists “Effort” variables  3) Energy is conserved

 How to write a domain that couples hydraulic and thermal behavior? ◦ Learn the mechanics of ‘Simscape’ Language (structure, syntax, etc) ◦ Test with a sample, energy conserving networks  How to modify that domain to accurately model our system? ◦ Mass flow rate, pressure, enthalpy, momentum, etc. ◦ Build a source, flowing into a simple network of pipes

Electro-Hydraulic Servo valve Example

 2 ‘Effort’ (across) variables ◦ Temperature and Pressure drops  2 Corresponding ‘FLOW’ variables  Power = Flow*Effort ◦ Energy conserving variables noted ◦ Default values assigned (but are over-written in each model)

A t,p + B t,p - Component Template qfqt

 Includes both domains, but not coupled  Units matter!! Constraints, not assignments!

Reference node

 What are our effort variables and units?  What are our flow variables and units?  What are the governing network equations, in nodal form?  What are the domain coupling expressions/constraints between the two domains?