##1

Individual Electro-Hydraulic Drives

for Off-Road Vehicles

(a DOE supported project)

Maha Fluid Power Research Center

Purdue University, West Lafayette, IN (USA)

https://engineering.purdue.edu/Maha/

Shaoyang Qu, Dr. Lizhi Shang

Prof. Sudhoff (co-PI) Uwe Neumann, Enrique Busquets Gary Kassen, Roman Plaszewski

PI: Prof. Andrea Vacca

##2Basic Idea

Electric – Hydraulic Hybrid

architecture

Main features

✓ Self contained individual drives

✓ No fluid throttling

✓ Energy recuperation

✓ Reduced ICE size

✓ Enables smart actuators, operating

as modern “plug & play” elements

✓ Zero emission modes

DOE Objective: Lower power

consumption of the fluid power

system up to 70%

##3Key components

P

Objective 1 (O1). 4-quadrant EH hydraulic unit

Objective 2 (O2). Individualized EH system

Objective 3 (O3). Technology demonstration

##4

4

• Baseline measurements

• Power consumption analysis

• Simulation model of mechanism

Reference vehicle

System configuration

EH unit optimization

(Baseline)

Contents

(Hydraulic circuit)

(Electric motor and pump)

##5

Off-road construction vehicle: skid-steer loader Case TV 380

boombucket

• Two functions (boom, bucket) considered for the technology demonstration

• Machine instrumented for baseline measurements of hydraulic power consumption

• Execution of test plan representative of typical machine duty cycle

Machine Main Specification

Engine TypeDiesel, Turbo – Direct

Injection,4 cylinders

Max power 90 hp [67 kW]

Fuel Capacity 25.5 gal [96.5 L]

Max Standard flow 24.2 gpm [91.5 L/min]

Machine Weight 10,207 lb. [4630 Kg]

Engine speed 1150-2500 rpm

Reference Vehicle

##6

Raise Lower Raise Lower

high load – low speed low load – high speed

𝐹𝑝1𝑝2

The reference machine is designed towards functionality and cost more than efficiency.

Reference Vehicle

Boom test

##7

Model of the hydraulic system

Model of the mechanism

Bucket

Boom

Tip Cylinder

Lift Cylinder

Simulation Method: Mechanism

Reference Vehicle

##8

Simulation Method: Mechanism

Reference Vehicle

##9

9

• Circuit configuration

• Evaluation of efficiencies

• Experimental set up

Reference vehicle

System configuration

EH unit optimization

(Baseline)

Contents

(Hydraulic circuit)

(Electric motor and pump)

##10

VALVES

ECU

VALVES

ECU

Boom control (EHA)

main control

unit

Operator interface

Energy StorageBattery

EngineGeneratorICE

External Grid

Bus

EHA Power Electronics

Bucket control (EHA)

DC Link Distribution

EHA Power Electronics

• EHA units are powered by a vehicle DC

power distribution network

Proposed architecture

##11

closed circuit option open circuit option

Proposed architecture

##12Results – Boom cycle

Remarks

✓ Closed vs open

circuit architecture

✓ Independence on load

##13

Raise boom Lower boomBucket

downBuc

up

Results – Boom/Bucket cycle

##14Energy Flow

ሶ𝑥𝐹

Raising phase

Accumulator power 𝑝𝑎𝑐𝑐

System efficiencyInput power

𝑝𝑖𝑛𝑝𝑢𝑡EH unit

power

𝑝𝐸𝐻

User power

𝑝𝑈𝑠𝑒𝑟

𝑝𝑢𝑠𝑒𝑟𝑝𝑖𝑛𝑝𝑢𝑡 + 𝑝𝑎𝑐𝑐

× 100%

Circuit efficiency𝑝𝑢𝑠𝑒𝑟

𝑝𝐸𝐻 + 𝑝𝑎𝑐𝑐× 100%

##15

Input power

𝑝𝑖𝑛𝑝𝑢𝑡 𝜔, 𝑇

Shaft power𝑝𝑠ℎ𝑎𝑓𝑡

Electric Motor efficiency

𝜂 𝜔, 𝑇 =𝑝𝑠ℎ𝑎𝑓𝑡

𝑝𝑖𝑛𝑝𝑢𝑡× 100%

EH unit power

𝑝𝐸𝐻

𝑝1

𝑝2

Pump efficiency

𝜂 𝑝2 − 𝑝1, 𝜔 = 𝜂𝑉 ∗ 𝜂ℎ𝑚 =𝑝𝐸𝐻𝑝𝑠ℎ𝑎𝑓𝑡

× 100%

Energy Flow

##16

• Raising with 1000lbs

• 4-quadrant pump, closed loop

• Average speed: 2867rpm

Motor&

Inverter

92.0%

6.04kW

Power

input

5.56kW

Shaft

Hydraulic

Pump

88.6%

Heat0.48kW

4.93kWCircuit

98.4%

Accumulator

0.08kWHeat &

Leakage0.63kW

Heat0.08kW

4.93kW

User

power

Power flow

##17

• Lowering with 1000lbs

• 2-quadrant pump, open loop

• Average speed: -3576rpm

Motor&

Inverter

91.8%

2.33kW

Power

Output

2.53kW

Shaft

Hydraulic

Pump

93.7%

Heat

2.71kWCircuit

98%

Heat &

Leakage

2.75kW

User power

Heat

0.2kW 0.18kW 0.04kW

Power flow

##18

• Building EHD with standard hydraulic components (later with new designed

DOE-Unit)

• Coupling force controlled cylinder drive (transmission ratio=1) for load

simulation

18

Test rig

##19

19

Test rig

Experimental set up

##20

20

• Hydraulic unit

• Electric machine

• Model integration & optimization

• Prototype

Reference vehicle

System configuration

EH unit optimization

(Baseline)

Contents

(Hydraulic circuit)

(Electric motor and pump)

##21

Fluid-Dynamic Module

-Analysis of Main Flow

-Effect of Porting grooves

-Aeration and Cavitation

Lateral Gap Module

Fluid Structure and

Thermal Interaction

Loading Module

Evaluation of

Instantaneous Radial

Forces and Torque

Journal Bearing

Module

Fluid Structure

Interaction

Micro-Motion Module

Evaluation of Gears’

Micro-Motion

Noise FEM/BEM Module

-Fluid-Borne Noise

-Structure-Borne Noise

-Air-Borne Noise

CAD Drawings

Geometrical Module

-Flexible geometry from CAD

-Asymmetric teeth

-Cycloidal-involute Profile

-Helical Gears

HYGESim (HYdraulic GEar machines Simulator)

Model integration – Hydraulic unit (O1)

##22Model integration – Hydraulic unit (O1)

Journal Bearing

Module

Fluid Structure

Interaction

Micro-Motion Module

Evaluation of Gears’

Micro-Motion

Lateral Gap Module

Fluid Structure and

Thermal Interaction

Coupled Lumped/Distributed param. modeling of:

• Inertial motion of floating elements

• Static cavitation

• Mixed Lubrication

• Elastic Body deformation

• Elastic Fluid-Structure Interaction

𝑀 =𝑑𝐻

𝑑𝑡 റ𝐹 = 𝑚

𝑑 റ𝑣

𝑑𝑡

ℎ = ℎ 𝑝, 𝑥, 𝑦, 𝑡

##23Model integration – Hydraulic unit (O1)

High Efficiency Piston PumpHigh efficient compact EHA

Variable Displacement External Gear Machine

##24Model integration – electric machine (O2)

Set of optimal design

solutions

Electric drive

performance

Mechanical output

Operating Conditions

Magnetic

Material Characterization

Winding Configuration

Vehicle power

requirements;

EHA requirements;

manufacturability constraints; …

Geometry

Candidate Create

feasible

geometry

Hydraulic

s

Mass,

volume, ...

Electric

Analysis

Magnetic

Analysis

Control

Leakage and

magnetizing

inductances,

Ohmic resistance,

proximity effect,…

Select current

commands,

winding and

semiconductor

losses, …

Core

losses,

torque, …

Electric Drive Optimization

##25EH unit optimization (O2)

NSGA-IIAlgorithm

InitialDOE

Gear & Groove

Parameters

GearGenerator

Gear calculation

Feasibility Checks

Geometrical Model

C++

Groove design

.txt files

Tooth profile

.txt files

Geometry files

.txt files

Rejected

Previous Optimization

Results

Post

Processing

Results files

.txt files

Design Grooves

##26

Elec

Mach

High Power DC

Distribution

Low Voltage

Control Power

Vehicle

CommunicationVehicle Safety

Cooling

Cooling

Power Electronic Inverter

Controller

6 Switch

Bridge

VALVES

ECU

VALVES

ECU

Boom control (EHA)

main control

unit

Operator interface

Energy StorageBattery

EngineGeneratorICE

External Grid

Bus

EHA Power Electronics

Bucket control (EHA)

DC Link Distribution

EHA Power Electronics

Electric system Architecture

##27Accomplishment

O1. EH unit

• 4-quadrant hydraulic unit design

• 4-quadrant electric motor design

• Performance evaluation of the EH unit

• EH unit Design integration

O2. EH module

• Modular simulation approach

• Duty cycle definition

• System configuration

• Circuit mode and control laws definition

O3. Technology Demonstration

• Baseline measurements

• Energy consumption analysis

• Simulation model of mechanism

##28

O1. EH unit

O2. EH module

• Thermal analysis and cooling solution

• Experimental validation of the functionality

• Controllability analysis and tests

O3. Technology Demonstration

• Configuration on the reference vehicle

• Supervisory controller for energy management

• Integration of energy generator and power electronics

Future work

O1. EH unit

• Design for manufacturing• Evaluation of Internal & external gear

machines

• Cooling solutions (fan, oil circulation)

• Structural analysis

##29

Thank you!

Question?