Source code for suboptimumg.vehicle.powertrain.powertrain

import numpy as np

from ...constants import *
from ..models import VehicleModel




class Motor:
    def __init__(
        self,
        vehicle_model: VehicleModel,
    ):
        self.vehicle_model = vehicle_model
        self.params = vehicle_model.pwrtn.motor



    def get_torque_at_rpm(self, motor_rpm: float) -> float:
        """
        Get motor torque at a given RPM using piecewise function.

        The torque curve has three regions:
        1. Flat region (0 to fw_rpm): constant max torque
        2. Linear decay (fw_rpm to max_rpm): torque decreases linearly
        3. Zero region (above max_rpm): no torque

        Parameters
        ----------
        motor_rpm : float
            Motor RPM

        Returns
        -------
        float
            Motor torque at the given RPM (Nm)
        """
        if motor_rpm < self.params.fw_rpm:
            # Pre-field weakening: constant max torque
            return self.params.max_torque
        elif motor_rpm <= self.params.max_rpm:
            # Field weakening: linear decrease from max_torque to fw_torque
            # Handle edge case where fw_rpm == max_rpm (no field weakening region)
            if self.params.max_rpm == self.params.fw_rpm:
                return self.params.max_torque

            slope = (self.params.max_torque - self.params.fw_torque) / (
                self.params.max_rpm - self.params.fw_rpm
            )
            return self.params.max_torque - slope * (motor_rpm - self.params.fw_rpm)
        else:
            # Above max RPM: no torque
            return 0.0




    def calculate_max_ground_force_and_motor_power(self, v, ratio):
        """
        Calculates force and power output by the motor.

        Parameters
        ----------
        v : float
            Velocity of the vehicle (m/s)
        ratio : float
            Gear ratio

        Returns
        -------
        ground_force : float
            Force at the ground (N)
        motor_power : float
            Motor power output (W)
        """
        tire_cir = circumference(
            in_to_m(self.vehicle_model.tires.tire_radius)
        )  # meters

        # Calculate motor RPM from vehicle velocity
        rot_per_sec = v / tire_cir
        wheel_rpm = rot_per_sec * 60
        motor_rpm = wheel_rpm * ratio  # rpm_out = rpm_in / ratio

        # Get motor torque from piecewise function
        motor_torque = self.get_torque_at_rpm(motor_rpm)

        # Clamp motor torque with power limit
        motor_torque = min(
            motor_torque, self.params.pow_lim / max(rpm_to_rad_s(motor_rpm), 1e-6)
        )

        # Convert to wheel torque
        wheel_torque = (
            motor_torque * ratio * self.powertrain_efficiency()
        )  # torque_out = torque_in * ratio * efficiency
        ground_force = wheel_torque / in_to_m(self.vehicle_model.tires.tire_radius)

        # Calculate force and power
        return ground_force, motor_torque * rpm_to_rad_s(motor_rpm)




    def powertrain_efficiency(self):
        """
        Calculates the system efficiency of the powertrain.

        Uses system efficiency if it is set, otherwise uses the product of the individual efficiencies.

        Returns
        -------
        float
            System efficiency of the powertrain
        """
        # TODO: DIFF EFFICIENCY is set to 100% for now

        if self.params.efficiency_method == "sys":
            return self.params.system_efficiency
        elif self.params.efficiency_method == "indiv":
            return (
                self.params.moc_efficiency
                * self.params.motor_efficiency
                * self.params.chain_efficiency
                * self.params.diff_efficiency
            )
        else:
            raise ValueError(
                "Invalid efficiency method. Must be 'sys' or 'indiv'. Got: ",
                self.params.efficiency_method,
            )






class Powertrain:
    def __init__(
        self,
        vehicle_model: VehicleModel,
    ):
        self.vehicle_model = vehicle_model
        self.params = vehicle_model.pwrtn

        # Construct Motor object
        self.motor = Motor(vehicle_model=vehicle_model)