Coupe
This example shows a full throttle acceleration maneuver for the Coupe electric vehicle with the Polynomial chassis and SingleMotorRWD powertrain using the open loop longitudinal driver.
To enable the use of traction control, the controller in the powertrain has been redeclared to PropulsionControl torque controller. The parameter trc_routing={6} for the TorqueArbitration block inside the controller allows the torque limitation to be performed on the rear axle if either or both the wheels reach the lower slip limit defined by the slip_min parameter in the TRC3 block in the controller.
The plot below shows the following quantities:
- Vehicle longitudinal velocity: chassis.summary_v_x
- Actual motor torque: vehicle.powertrain.motor.summary.tau_rotor
- Motor torque requested: vehicle.powertrain.controller.controlBus.machine[1].tau_ref
- Maximum power limit from the battery: vehicle.powertrain.batteryPack.controller.limits.p_max_out
- Power drawn from the battery: vehicle.powertrain.batteryPack.summary.p_out
It can be seen that when full throttle is applied at 2 sec, the traction control system is limiting the maximum torque (280Nm) from being applied. Between 2.82 to 7.22 seconds the motor is producing the maximum torque as the battery power output is still below the limit of 213 kW. Once this limit is reached at 7.22 sec, the motor is operating in the constant power region seen as a reduction in torque as the motor rotational velocity increases.
The default parametrization of the detailed Electric powertrains in VDL imposes only a power limit from the battery with the current and voltage limits set to very high values. In this case, the power limit is set to 213 kW as shown in the plot above.
Effect of traction control
The plot below shows the vehicle velocity, motor torque and the power drawn from the battery for two simulations run with and without traction control (Traction control can be turned off by setting on=false in the TRC3 block inside vehicle.powertrain.controller). It can be seen that without traction control, the peak torque is applied as soon as full throttle is applied resulting into wheel spin and the power limit being reached at 3.25 sec. This reduces the maximum torque available from the motor and shows the importance of including a traction control system in case of acceleration performance simulations for electric vehicles.
The motor torque vs rotational velocity characteristics for the two cases are shown below. The plots are identical apart from the traction control system limiting the torque output around zero motor speed corresponding to starting from standstill.
The traction control system implemented in this example is a simplified system with fixed slip limit targets. Implementing a more detailed system is made possible by the use of Interfaces and Templates for the ControlUnits for electric powertrains where custom torque modulation, addition and arbitration blocks can be used.