pysim models - vehicle model

Simulation model : Vehicle

Description

• Simulate vehicle dynamics of EV

Modules summary

• Body module - simulate dynamics of drivetrain

  • Drivetrain_config - configure drive train Parameters
  • Lon_equivalence - calculate rotational dynamics of equivalent vehicle
  • Driveshaft_dynamics - calculate rotational dynamics of drive shaft
  • Tire_dynamics - calculate rotational dynamics of tire
  • Motor_dynamics - calculate rotational dynamics of motor out

• Vehicle module - contain power module and body module, simulate vehicle behavior

  • Veh_init_config - configure initial vehicle state, position, velocity
  • Veh_config - configure vehicle parameters
  • Veh_position_update - update vehicle position according to speed and steering

  • Veh_driven - calculate vehicle velocity and wheel theta

    • Veh_lon_driven - simulate longitudinal vehicle behavior (include Mod_Power(Motor_driven), Mod_Body(Lon_equivalence))

      • Veh_lon_dynamics - calculate vehicle acceleration according to traction force and drag force
      • Acc_system - determine desired torque set according to acceleration pedal position
      • Brake_system - determine brake torque set according to brake pedal position
      • Drag_system - determine air and rolling resistance force

    • Veh_lat_driven - simulate lateral vehicle behavior

      • Veh_lat_dynamics - calculate tire wheel dynamics according to steering input

• Module diagram:

  Veh_driven( Veh_lon_driven, Veh_lat_driven )
      >> Veh_lon_driven( Veh_lon_dynamics, Acc_system, Brake_system, Drag_system, Motor_driven, Lon_equivalence )
          >> Lon_equivalence in Mod_Body
          >> Motor_driven in Mod_Power
      >> Veh_lat_driven( Veh_lat_dynamics )
  

Update

• [18/05/31] - Initial release - Kyunghan
• [18/06/01] - Seperate powertrain class in new file - Kyuhwan
• [18/06/11] - Modification - Kyunghan - Modify drivetrain module to body module - Modify model configurations - Add regeneration module in body.brake_system
• [18/08/08] - Restructure - Kyunghan - Modify drive train module - Modify tire module - Modify drag force module

class pysim.models.model_vehicle.Mod_Body

Bases: object

• Body module

Driveshaft_dynamics(t_shaft_in, t_shaft_out, w_shaft)

Calculate rotational dynamics of shaft

Args:

• t_shaft_in: shaft in torque = motor_out torque - mechanical loss [Nm]
• t_shaft_out: shaft out torque [Nm]
• w_shaft: previous rotational speed of shaft [rad/s]

Return:

• w_shaft: updated rotational speed of shaft [rad/s]

Drivetrain_config(conf_rd_wheel=0.301, conf_jw_wheel=0.1431, conf_jw_diff_in=0.015, conf_jw_diff_out=0.015, conf_jw_trns_out=0.015, conf_jw_trns_in=0.01, conf_jw_mot=0.005, conf_eff_trns=0.96, conf_eff_diff=0.9796, conf_eff_diff_neg=0.9587, conf_gear=6.058, conf_mass_veh=1200, conf_mass_add=0)

Drivetrain and body parameter configuration Parameters not specified are declared as default values If you want set a specific parameter don’t use this function, just type:

Mod_Body.conf_veh_len = 2
...

Parameters:

Vehicle mass Wheel radius Momentum of inertia: shaft, wheel Drive shaft efficiency, gear ratio

Lon_equivalence(t_mot, t_brk, t_drag)

Calculate equivalent rotational dynamics of vhielce

Equivalet component: Motor + Shaft + Wheel + Vehicle

Dynamics:

w_vehicle_dot = (t_motor - t_drag - t_brake) / j_veh
...

Args:

• t_mot: motor torque [Nm]
• t_brk: brake torque [Nm]
• t_drag: equivalent drag torque [Nm]

Return:

• load torque: load torque of each component [Nm]
• f_lon: longitudinal traction force [N]

Motor_dynamics(t_mot, t_mot_load, w_motor)

Calculate rotational dynamics of motor

Args:

• t_mot: motor generated torque [Nm]
• t_mot_load: motor load torque to shaft [Nm]
• w_shaft: previous rotational speed of motor [rad/s]

Return:

• w_shaft: updated rotational speed of motor [rad/s]

Tire_dynamics(t_wheel_load, t_wheel_traction_f, t_brk, w_wheel)

Calculate rotational dynamics of wheel

Args:

• t_wheel_load: wheel in torque = shaft out torque [Nm]
• t_wheel_traction_f: wheel out torque to traction force [Nm]
• t_brk: brake torque [Nm]
• w_shaft: previous rotational speed of wheel [rad/s]

Return:

• w_shaft: updated rotational speed of wheel [rad/s]

class pysim.models.model_vehicle.Mod_Veh(powertrain_model, drivetrain_model)

Bases: object

• Vehicle module: Set the power and body model when initialization

Acc_system(u_acc)

Determine desired motor torque

Args:

• u_acc: acceleration pedal of driver [-]

Return:

• t_mot_des: desired motor torque [Nm]

Brake_system(u_brake, t_reg_set=0)

Determine brake torque

Regen control:

swtRegCtl = 0 # Meachanical braking
swtRegCtl = 1 # Transfer braking torque to regenerative motor torque
swtRegCtl = 2 # Set the specific regenerative motor torque

Args:

• u_brake: acceleration pedal of driver [-]
• t_reg_set: Regenerative torque set [-]

Return:

• t_brake: Braking torque [Nm]
• t_mot_reg: Regenerative motor torque [Nm]

Drag_system(vel_veh)

Calculate drag torque

Air drag:

f_drag_air = 0.5*1.25*self.conf_drag_air_coef*vel_veh**2

Rolling resistance:

f_drag_roll = self.conf_drag_ca + self.conf_drag_cc*vel_veh**2

Args:

• vel_veh: vehicle velocity [m/s]

Return:

• t_drag: total drag torque [Nm]
• f_drag: total drag force [N]

Veh_config(conf_drag_air_coef=0, conf_add_weight=0, conf_drag_ca=143.06, conf_drag_cc=0.4405, conf_veh_len=2, conf_acc_trq_fac=82.76, conf_brk_trq_fac=501.8, conf_motreg_max=100)

Vehicle parameter configuration Parameters not specified are declared as default values If you want set a specific parameter don’t use this function, just type:

>>> Mod_Body.conf_veh_len = 2
...

Parameters:

• Vehicle size
• Air drag coefficient
• Rolling resistance coefficient
• Acceleration, Brake coefficient

Veh_driven(u_acc, u_brake, u_steer=0)

Simulate vehicle behavior according to driver’s input

Args:

• u_acc: Acceleration pedal position [-]
• u_brake: Brake pedal position [-]
• u_steer: Steering wheel angle [-]

Return:

• vel_veh: Vehicle velocity [m/s]
• the_wheel: Wheel heading angle [rad]

Include:

• Mod_Veh(Veh_lon_driven,Veh_lat_driven): Simulate vehicle behavior

Veh_init_config(x_veh=0, y_veh=0, s_veh=0, n_veh=0, psi_veh=0, vel_veh=0, theta_wheel=0)

Initialize vehicle state

State:

• Vehicle position on environment
• Velocity
• Heading angle

Veh_lat_driven(u_steer)

Simulate lateral vehicle behavior according to driver’s input

Args:

• u_steer: steering input [-]

Return:

• the_wheel: wheel heading angle [rad]

Include:

• Mod_Veh(Veh_lat_dynamics): Calculate wheel dynamics

Veh_lat_dynamics(the_wheel, u_steer)

Calculate lateral vehicle dynamics

Dynamics:

the_wheel_dot = (u_steer - the_wheel) / lat_dynamic_coeff
...

Args:

• u_steer: steering input of driver [-]
• the_wheel: longitudinal drag force from Drag_system, Brake_system [N]

Return:

• the_wheel: vehicle velocity [m/s]

Veh_lon_driven(u_acc, u_brake)

Simulate longitudinal vehicle behavior according to driver’s input

Calculate total drag force from Drag_system in vehicle module

Determine driven force from Acc_system and Brake_system in vehicle module

Drive Lon_equivalence function in body module

Args:

• u_acc: Acceleration pedal position [-]
• u_brake: Brake pedal position [-]

Return:

• veh_vel: Vehicle velocity [m/s]
• s, n position: Road relative vehicle position [m]
• psi_veh: Vehicle heading angle [rad]

Include:

• Mod_Veh(Acc_system, Brake_system, Drag_system, Veh_lon_dynamics): Determine driven torque
• Mod_Body(Lon_equivalence): Calculate vehicle rotational dynamics
• Mod_Power(Motor_driven): Determine motor driven torque

Veh_lon_dynamics(f_lon, f_drag, vel_veh)

Calculate longitudinal vehicle dynamics

Equivalet component: Motor + Shaft + Wheel + Vehicle

Dynamics:

veh_acc = (f_lon - f_drag) / m_veh
...

Args:

• f_lon: longitudinal driven force from Lon_equivalence [N]
• f_drag: longitudinal drag force from Drag_system, Brake_system [N]

Return:

• veh_vel: vehicle velocity [m/s]

Veh_position_update(vel_veh=0, the_wheel=0)

Update vehicle position on environment

Args:

• vel_veh: Vehicle velocity [m/s]
• the_wheel: Wheel angle [rad]

Return:

• x, y position: Absolute vehicle coordinate [m]
• s, n position: Road relative vehicle position [m]
• psi_veh: Vehicle heading angle [rad]

pysim.models.model_vehicle.Ts = 0.01

global vairable: simulation sampling timeself.

you can declare other sampling time in application as vairable Ts