Electric Vehicle Modeling Utilizing DC Motor Equations<br />Clay S. Hearn, Damon A. Weeks, Richard C Thompson, and Dongmei...
Introduction<br />Previous electric and hybrid electric vehicle modeling experience and demonstrations at UT-CEM<br />PSAT...
Vehicle Modeling at UT-CEM<br />Plug-In Hybrid Fuel Cell Shuttle Bus<br />On road evaluations<br />3 different routes<br /...
Advantages and Limitations of PSAT<br />Large library of component models derived from testing for engines, motors, batter...
Model Development<br />Base vehicle model is ParCar SUV-LN<br />48V lead acid batteries<br />12.9 kW DC motor<br />Model v...
Bond Graph Model Development<br />Bond graph tracks power flow and causality<br />Idealized DC converters modeled as trans...
Derived Equations from Bond Graph Model<br />Battery SOC is a quasi-state based on Voc – R battery model<br />Main model s...
DC Motor Control<br />Separately wound DC motors allow active control of field and armature current<br />Below base speed:...
Driver Model <br />Driver model estimates required torque to move vehicle along given velocity profile<br />Feed forward c...
Feed Forward Control Design<br />Linearize vehicle motion equations about a specified V0 and solve for steady state EM tor...
DC Motor Current Requirements<br />Vehicle model uses separate PI controllers for armature and field loops (m and n duty o...
Field Weakening Current Estimate<br />Steady state expression for armature current demand <br />Steady state expression fo...
Simulink Model Overview<br />
Route Following Response<br />
Comparisons to PSAT Performance<br />
Summary<br />Presented a causal model of an electric vehicle driven by separately wound DC motor <br />Developed driver mo...
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Electric vehicle modeling utilizing dc motor equations clay hearn - july 2010

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Electric vehicle modeling utilizing dc motor equations clay hearn - july 2010

  1. 1. Electric Vehicle Modeling Utilizing DC Motor Equations<br />Clay S. Hearn, Damon A. Weeks, Richard C Thompson, and Dongmei Chen<br />2010 IEEE/ASME International Conference on Advanced Intelligent Mechatronics<br />July 6 – 9, 2010, Montreal, Quebec<br />
  2. 2. Introduction<br />Previous electric and hybrid electric vehicle modeling experience and demonstrations at UT-CEM<br />PSAT modeling toolbox and motor models<br />Acausal modeling<br />Steady state efficiency maps<br />Development of causal electric vehicle model<br />Account for transient dynamics and other constraints<br />Requires feed-forward control design<br />
  3. 3. Vehicle Modeling at UT-CEM<br />Plug-In Hybrid Fuel Cell Shuttle Bus<br />On road evaluations<br />3 different routes<br />PSAT models matched energy consumption data to within 5%<br />Columbia ParCar utility vehicle conversion<br />Upgrading with 8.5 kW fuel cell and ultracapacitor energy storage<br />PSAT modeling used in design process<br />Base vehicle modeling with DC motor used for model development<br />
  4. 4. Advantages and Limitations of PSAT<br />Large library of component models derived from testing for engines, motors, batteries, etc…<br />Quickly evaluate different component options and hybrid configurations<br />Development of supervisory control strategies<br />Acausal modeling techniques<br />Static power converters with efficiency transfers power between batteries, motors, and auxiliaries<br />Steady state efficiency maps used for motors and engine models<br />Validity of efficiency map<br />Loss of transient dynamics<br />Loss of other limitations such as current limits or thermal limits<br />Inaccuracies in transient dynamics and performance limitations<br />
  5. 5. Model Development<br />Base vehicle model is ParCar SUV-LN<br />48V lead acid batteries<br />12.9 kW DC motor<br />Model vehicle with DC motor equations and causal modeling techniques<br />Bond graph and equation formulation<br />Develop control strategies for route following<br />Feed-forward Torque demand estimation<br />Field and armature voltage control<br />
  6. 6. Bond Graph Model Development<br />Bond graph tracks power flow and causality<br />Idealized DC converters modeled as transforming elements<br />Nonlinearities included in motor constant<br />
  7. 7. Derived Equations from Bond Graph Model<br />Battery SOC is a quasi-state based on Voc – R battery model<br />Main model states<br />If = field current<br />Ia = armature current<br />V = Linear velocity<br />Controls<br />m = field current duty cycle<br />n = armature current duty cycle<br />Back EMF<br />EM Torque<br />Motor <br />Friction<br />Drag<br />Grade and Roll Resistance<br />
  8. 8. DC Motor Control<br />Separately wound DC motors allow active control of field and armature current<br />Below base speed: field current held constant and armature voltage controlled for constant torque<br />Above base speed: field current is weakened to increase motor speed at constant power<br />
  9. 9. Driver Model <br />Driver model estimates required torque to move vehicle along given velocity profile<br />Feed forward controller design<br />Linearize and invert vehicle equations <br />Feedback PI controller included to add additional corrections to reference speed<br />
  10. 10. Feed Forward Control Design<br />Linearize vehicle motion equations about a specified V0 and solve for steady state EM torque<br />Derive and invert transfer function from linearized equations. Inverted TF yields dynamic EM torque output, but requires low-pass filter<br />Set filter pole ~100X left of pole location<br />Steady state torque minus V0 torque requirement is added to dynamic estimation (above) <br />
  11. 11. DC Motor Current Requirements<br />Vehicle model uses separate PI controllers for armature and field loops (m and n duty outputs)<br />Translate torque estimates from driver model to field and armature current demands<br />Constant torque regime<br />Constant field current at 10 amps<br />Solve for the armature current<br />Field weakening regime<br />Solve for the steady state field and armature currents from initial state equations<br />Solution based on the motor speed demand<br />
  12. 12. Field Weakening Current Estimate<br />Steady state expression for armature current demand <br />Steady state expression for field current demand <br />Substitution yields quadratic equation that can be used to find required currents<br />Above base speed, PI motor current controllers solve for these reference currents<br />Current limits are set at 400 A for armature and 40 A for field<br />
  13. 13. Simulink Model Overview<br />
  14. 14. Route Following Response<br />
  15. 15. Comparisons to PSAT Performance<br />
  16. 16. Summary<br />Presented a causal model of an electric vehicle driven by separately wound DC motor <br />Developed driver models and vehicle control algorithms<br />Level of modeling will include transient dynamics as well as specified constraints<br />Current limitations<br />Addition of thermal modeling will allow current limits due to thermal constraints<br />ParCar SUV-LN is now at UT-CEM for testing and retro-fit<br />

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