Project Robotics - March 2009 - (Page 15) maintained between the expressions on either side at all times. if multiple equations are used in a model, they are evaluated concurrently. in the architecture statement, both vin and vout need to be declared (k was declared in the entity). since the electrical terminals (input and output) of this model have both voltage (across) and current (through) aspects associated with them, these terminals cannot be directly used to realize the model equation. instead, individual objects are declared for each, and these objects are then used to realize the model equation. in Vhdl-aMs, analog-valued objects used to model conserved energy systems are called branch quantities because they are declared between two terminals. Branch quantity vin is declared as the voltage across port input relative to electrical ground, specified as electrical_ref in Vhdl-aMs models. Branch quantity vout is declared as the voltage across port output relative to electrical_ref. in the architecture listing, there no quantity declaration for the input current, since this is supposed to be an idealized voltage amplifier model and acts an ideal load, not drawing any current. since no branch quantity is declared for this current, the input current is zero. The idealized output can supply any current, so the through quantity iout is declared along with across quantity vout. The simulator will then solve for the instantaneous value of iout needed to ensure vout is the correct value for the expressions in the governing equation: vout == k * vin. While it is possible to model with much greater complexity using Vhdl-aMs, the inherent simplicity of the modeling statements do not create a barrier to their use. hopefully, you’ll be interested in pursing the language further, in which case the references given in the appendix will prove extremely useful. Contents Viewpoint the Cutting edge for haptiC researCh Modeling CoMplex eleCtroMeChaniCal systeMs deVeloping a two-wheeled self-BalanCing transport platforM aPPeNdiX how to Model Mechatronic systems using Vhdl-aMs, systemVision Technology series, Mentor graphics, series editors scott Cooper, Mike donnelly, darrel Teegarden, http://www. mentor.com/products/sm/techpubs/ index.cfm The system designer’s guide to Vhdl-aMs: analog, Mixed-signal, and Mixed-Technology Modeling,. by peter ashenden, university of adelaide, gregory peterson, university of Tennessee, and darrell Teegarden, Mentor graphics. http://books.elsevier. com/mk/default.asp?isbn=1558607498 “fundamentals of Vhdl-aMs for automotive electrical systems,.” online workshop presented by Mentor graphics. available from the systemVision website (http://www.mentor.com/products/sm/ system_integration_simulation_analysis/ systemvision/demos/fund_vhdl_ams) home page product training Module online ordering suppliers Catalog VoluMe 1 15 || nuMBer 1 http://ad.doubleclick.net/clk;212422364;32989198;o?http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&keywords=robotics http://ad.doubleclick.net/clk;212362954;32989198;w?http://www.digikey.com http://ad.doubleclick.net/clk;212362954;32989198;w?http://www.digikey.com http://www.mentor.com/products/sm/techpubs/index.cfm http://www.mentor.com/products/sm/system_integration_simulation_analysis/systemvision/demos/fund_vhdl_ams http://ad.doubleclick.net/clk;212363051;32989198;l?http://digikey.com/PTM/PTMMaster.page?site=us&lang=en http://www.mentor.com/products/sm/techpubs/index.cfm http://www.mentor.com/products/sm/system_integration_simulation_analysis/systemvision/demos/fund_vhdl_ams http://ad.doubleclick.net/clk;212363300;32989198;i?http://ordering.digikey.com/ordering/addpart.aspx?site=US&source=search http://www.mentor.com/products/sm/techpubs/index.cfm http://books.elsevier.com/mk/default.asp?isbn=1558607498 http://www.mentor.com/products/sm/system_integration_simulation_analysis/systemvision/demos/fund_vhdl_ams http://ad.doubleclick.net/clk;212363091;32989198;p?http://digikey.com/Suppliers/SupplierIndex.page?site=us&lang=en http://books.elsevier.com/mk/default.asp?isbn=1558607498 http://ad.doubleclick.net/clk;212363309;32989198;r?http://dkc1.digikey.com/us/en/pdf/Current.html
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