Hands-On: Complete HIL Validation Project

#!/usr/bin/env python3
# EPS plant model: vehicle + steering column + PMSM
# Integrates bicycle model with EPS assist torque

import numpy as np

class EPSPlantModel:
    def __init__(self):
        # Steering column parameters
        self.K_torsion = 15000   # torsion bar stiffness (Nm/rad)
        self.J_column  = 0.02    # column inertia (kg.m2)
        self.B_column  = 5.0     # column damping (Nms/rad)

        # Vehicle (bicycle model)
        self.m  = 1500; self.Iz = 2500
        self.lf = 1.2;  self.lr = 1.4
        self.Cf = 60000; self.Cr = 50000
        self.Vx = 0.0

        # States
        self.theta_sw   = 0.0   # steering wheel angle (rad)
        self.dtheta_sw  = 0.0   # steering wheel velocity (rad/s)
        self.theta_col  = 0.0   # column/rack angle (rad)
        self.vy = 0.0; self.r = 0.0

    def step(self, T_driver_Nm, T_assist_Nm, Vx, dt):
        """
        T_driver_Nm: driver hand torque input (Nm)
        T_assist_Nm: EPS ECU assist torque output (Nm) -- from HIL I/O
        Vx: longitudinal speed (m/s)
        """
        self.Vx = Vx

        # Torsion bar torque
        T_torsion = self.K_torsion * (self.theta_sw - self.theta_col)

        # Steering wheel dynamics
        d2theta_sw = (T_driver_Nm - T_torsion - self.B_column*self.dtheta_sw)
        d2theta_sw /= self.J_column
        self.dtheta_sw += d2theta_sw * dt
        self.theta_sw  += self.dtheta_sw * dt

        # Column dynamics (with assist)
        T_rack = T_torsion + T_assist_Nm
        delta_f = self.theta_col / 15.0   # steering ratio 15:1

        # Vehicle lateral dynamics (bicycle model)
        alpha_f = delta_f - (self.vy + 1.2*self.r) / max(Vx, 0.1)
        alpha_r =          -(self.vy - 1.4*self.r) / max(Vx, 0.1)
        Fy_f = self.Cf * alpha_f
        Fy_r = self.Cr * alpha_r
        self.vy += ((Fy_f + Fy_r)/self.m - Vx*self.r) * dt
        self.r  += (1.2*Fy_f - 1.4*Fy_r)/self.Iz * dt

        return {
            "torque_sensor_Nm":  T_torsion,
            "steering_angle_deg":np.degrees(self.theta_sw),
            "yaw_rate_degps":    np.degrees(self.r),
        }

#!/usr/bin/env python3
# EPS HIL validation test suite
# pytest test_eps_hil.py -v --html=eps_validation_report.html

import pytest, time

@pytest.mark.req("TSR-EPS-001")
@pytest.mark.asil("ASIL-D")
def test_eps_assist_nominal(hil):
    """EPS shall provide assist torque proportional to driver torque at 50 km/h"""
    hil.set("Plant/Speed_kph",          50.0)
    hil.set("Plant/Driver/Torque_Nm",    5.0)
    hil.wait(0.5)
    assist = hil.get("ECU.EPS.AssistTorque_Nm")
    assert 10.0 <= assist <= 25.0, f"Assist {assist:.1f} Nm out of range"

@pytest.mark.req("TSR-EPS-015")
@pytest.mark.asil("ASIL-D")
def test_eps_safe_state_on_torque_sensor_fault(hil):
    """EPS shall remove assist within FTTI=200ms of torque sensor fault"""
    hil.set("Plant/Speed_kph",          80.0)
    hil.set("Plant/Driver/Torque_Nm",    5.0)
    hil.wait(1.0)

    t0 = time.time()
    hil.inject_fault("TorqueSensor_ChA", "SHORT_GND")

    safe = False
    while (time.time()-t0)*1000 < 250:
        if abs(hil.get("ECU.EPS.AssistTorque_Nm")) < 0.5:
            t_ms = (time.time()-t0)*1000
            print(f"  Safe state at {t_ms:.1f} ms")
            safe = True; break
        time.sleep(0.005)

    assert safe, "Safe state not reached"
    assert t_ms <= 200, f"FTTI exceeded: {t_ms:.1f} ms > 200 ms"