The principal input to the model is the voltage to the motor. Motor parameters include resistance (ohm), motor inductance (henrys), back emf constant (volt-sec/rad), torque constant (N-m/a), rotor inertia (kg m^2), and mechanical damping. The automotive parameters include vehicle inertia, vehicle damping (friction), transmission dynamics, gearing ratios, and a simplified model of tire friction on the paved surface. The electric vehicle models tracks system including motor electrical current (amps), rotor angular velocity (radians/sec), rotor angle (radians), wheel angular velocity (rad/sec), wheel angle (radians), vehicle velocity (m/sec), and distance travelled (m).

! APMonitor Modeling Language ! http://www.apmonitor.com ! Electric Vehicle Model Model car Parameters ! motor parameters (dc motor) v = 36 ! input voltage to the motor (volts) rm = 0.1 ! motor resistance (ohm) lm = 0.01 ! motor inductance (henrys) kb = 6.5e-4 ! back emf constant (volt-sec/rad) kt = 0.1 ! torque constant (N-m/a) jm = 1.0e-4 ! rotor inertia (kg m^2) bm = 1.0e-5 ! mechanical damping (linear model of friction: bm * dth) ! automobile parameters jl = 1000*jm ! vehicle inertia (1000 times the rotor) bl = 1.0e-3 ! vehicle damping (friction) k = 1.0e2 ! spring constant for connection rotor/drive shaft b = 0.1 ! spring damping for connection rotor/drive shaft rl = 0.005 ! gearing ratio between motor and tire (meters travelled ! per radian of motor rotation) tau = 2 ! time constant of a lag between motor torque and car ! velocity. this lag is a simplified model of the power ! train. (sec) End Parameters Variables i = 0 ! motor electrical current (amps) dth_m = 0 ! rotor angular velocity sometimes called omega (radians/sec) th_m = 0 ! rotor angle, theta (radians) dth_l = 0 ! wheel angular velocity (rad/sec) th_l = 0 ! wheel angle (radians) dth_v = 0 ! vehicle velocity (m/sec) th_v = 0 ! distance travelled (m) End Variables Equations lm*$i - v = -rm*i - kb *$th_m jm*$dth_m = kt*i - (bm+b)*$th_m - k*th_m + b *$th_l + k*th_l jl*$dth_l = b *$th_m + k*th_m - (b+bl)*$th_l - k*th_l tau * $dth_v = rl * dth_l - dth_v dth_m = $th_m dth_l = $th_l dth_v = $th_v End Equations End Model

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Page last modified on March 06, 2010, at 09:40 AM