HEV Modelling & Optimization

- Deepak Chandran

Praveen S R

Objective

• To analyze the existing test data of the 2015 Honda Accord,determine the control strategy and model the same for a 1.4 UDDStest cycle data.

• To optimize the parallel mode region and deduce the change in MPG.

STEPS INVOLVED IN OPTIMIZATION

Reverse Engineering existing Test data

Obtain Parallel mode region

Use the above control strategy to model Accord HEV for a 1.4 UDDS cycle

Analysis of test data

The fuel economy and electrical energyConsumption for the given UDDS cycle ofThe test data has been calculated.

Time(s) vs SOC vs Speed (MPH) for the given cycle is plotted.

Similar analysis has been performed onDifferent cycles to obtain more data Points.

Obtaining Parallel operation in UDDS

To obtain the parallel region of operation for the given UDDS cycle, ratio of vehicle speed(MPH) and Engine Speed (rpm) was plotted against time(s). The region of constant ratio (0.027) was selected as the parallel operating mode.

Tractive Force Battery Current(A)

EV only Positive (Pretransmission power < ENG ON)

Positive

Engine (ParallelMode)

Positive Negative

Engine only (Series Mode)

Positive(Wheel demand > Engine power)

Negative

Engine (assist mode)

Positive(Pretransmission power > ENG ON)

Positive

Regen Mode Negative Negative

Parallel region analysis

Data points obtained from cycles Were plotted with respect to Tractive effortAnd Speed.

2 HWY 2 US 06 2 UDDS

Parallel operating region was determined As Speeds >45 MPH and Force <900N

HEV Modelling

Based on the control strategy obtained earlier we have modelled a HEV operating in 1.4 UDDS .

We have obtained a fuel economy analysis with the NETC tolerance limits.

Tractive Force Battery Current(A)

EV only Positive (Pretransmission power < ENG ON)

Positive

Engine (ParallelMode)

Positive Negative

Engine only (Series Mode)

Positive(Wheel demand > Engine power)

Negative

Engine (assist mode) Positive(Pretransmission power > ENG ON)

Positive

Regen Mode Negative Negative

Determination of Engine Power & Fuel Consumption –RSM Model

WW = -1.70711E-1 +2.17320E-4 * A2 +9.11151E-3 * B2 -1.41102E-9 * A2^2 +1.63838E-6 * A2B2 -1.09140E-4 * B2^2 -5.04269E-12 * A2^3 +9.58023E-10 * A2^2B2 -6.44252E-9 * A2B2^2 +6.38647E-7 * B2^3

For N < 2000 rpm, T = 0.015 * N + 60

For N > 2000 rpm & N < 2500 rpm, T = 0.04 * N + 10

For N > 2500, T = 0.02 * N + 60

Basis of Optimization

Reasons for picking Highway Cycle

In a highway cycle, vehicle is more often at high speeds and steady state. This lea to more opportunity for parallel analysis (High speed and Low traction conditions)

STEPS INVOLVED IN OPTIMIZATION

Reverse Engineering existing Test data

Obtain Parallel mode region

Modify speed and torque of Parallel Mode region of HWY data

Assumptions

• Pre-transmission wheel demand and opportunity charging are the same.

• Engine efficiency is 40% instead of 42% since it operates at a lesser power region.

THANK YOU