##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/

Andrea Vacca (PI)

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

##2

Classical centralized

architecture

Hydraulic Individualization

Electrification

Basic idea

##3

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%

Basic idea

##4

P

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

Objective 2 (O2). Individualized EH system

Objective 3 (O3). Technology demonstration

Key components

##5

reference vehicle

##6

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

• Tests 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

##7

Pump 1

Self Level

MR

Line 2

Line 3

Line 4

P5

P1

P2

P3

P4

Unit 2

Unit 1

Unit 3

Unit 4

metering

D1

Lift Cylinders Tip Cylinders

Hydraulic Couplers

Auxiliary Quick

Disconnections

Secondary Auxiliary

Quick Disconnecions

Gear Pump interface

to Tandam Pump Line 1Hyd Oil Filter

wl 50psi Bypass

Oil Cooler

wl 75psi Bypass

PR1 PR2 PR3

D2

Bucket

Boom

Tip Cylinder

Lift Cylinder

7

Cylinders

Case TV380

Instrumentation:

• Pressure sensors

• Position sensors

• Flow metering

Pump

Open Center Valves

Reference vehicle

##8

Raise Lower Raise Lower

high load – low speed low load – high speed

𝐹𝑝1𝑝2

Boom test

##9

High pressure

Low pressure

Boom control ሶ𝑥 ሶ𝑥

Raise Lower

Open Center System

##10

Area function plot (lowering)

Ω𝐵𝑇

Ω𝑃𝐴

Ω𝑃𝑇

𝐹

ሶ𝑥

𝐹

ሶ𝑥

Ω𝑃𝐵

Ω𝐴𝑇Ω𝑃𝑇

Raising phase (resistive) Lowering phase (overrunning)

Open Center System

##11

Equivalent Load

Pump PowerFull command, 1000 pounds load

Essential for sizing the EHA

Power Demands

##12Power Demands

##13

proposed solution

##14

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

• Power electronics convert DC voltage into

three-phase AC currents to regulate electric

machine torque, and thus pump output

Proposed Architecture

##15

MOT

Proposed Architecture

##16

MOT

MOT

MOT

MOT

Δ𝑝

ሶ𝑥

𝐹 > 0𝐹 < 0

𝐹 = 𝑝1𝐴 − 𝑝2𝑎

𝑄𝑎𝑐𝑐 = 𝑄𝑎 𝜑 − 1

𝑄𝐴

𝑄𝑎𝑐𝑐

𝑄𝑎

𝑄𝐴

𝑄𝐴

𝑄𝑎𝑄𝐴

ሶ𝑥𝐹

𝑄𝑎𝑐𝑐 = 𝑄𝑎 𝜑 − 1

𝑄𝐴

𝑄𝑎𝑐𝑐

𝑄𝑎

𝑄𝑎𝑄𝐴

ሶ𝑥𝐹

𝑄𝐴

𝑄𝐴𝑄𝑎𝑐𝑐 = 𝑄𝑎 𝜑 − 1

𝑄𝐴𝑄𝑎𝑐𝑐

𝑄𝑎

𝑄𝑎𝑄𝐴

ሶ𝑥𝐹

𝑄𝑎

𝑄𝑎

𝑄𝑎𝑐𝑐 = 𝑄𝑎 𝜑 − 1

𝑄𝐴𝑄𝑎𝑐𝑐

𝑄𝑎

𝑄𝑎𝑄𝐴

ሶ𝑥 𝐹

𝑄𝑎

𝑄𝑎

High pressure

Low pressure

𝐴 > 𝑎

Working Modes

##17

Δ𝑝

ሶ𝑥

𝐹 > 0𝐹 < 0

Working Modes

##18

Model of the hydraulic system

Model of the mechanism

Bucket

Boom

Tip Cylinder

Lift Cylinder

Simulation

##19Simulation

##20

Load data

from tests

Displacement tracking

𝜂𝑣𝑜𝑙 𝜂ℎ𝑚

Simulation

##21Simulation

##22

Raise LowerFor the proposed system:

• results based on simulation

• regenerates energy when

lowering

Results: boom cycle

##23

Remarks

✓ Closed vs open

circuit architecture

✓ Independence on load

𝜂 =𝐸𝑟𝑒𝑓

𝐸𝐸𝐻𝐴× 100%

Results: boom cycle

##24

Raise boom Lower boomBucket

downBuc

up

Results: boom/bucket cycle

##25

EH unit

##26

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

##27

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

Model Integration

##28

Objective functions

1. Minimize Cycle Power

2. Minimize EH Volume

3. Minimize Flow Ripple

4. Minimize Torque Ripple

Optimization

Design GoalsParametrize

Problem

Generate

Design

Calculate

Performance

Adjust

Parameters

Problem Definition

Optimize for Problem

𝑥𝑐𝑦𝑙

𝑡

𝑡𝑟𝑎𝑖𝑠𝑒 𝑡𝑙𝑜𝑤𝑒𝑟

2 3

##29

Nominal

Peak

𝜃1𝑋1

𝜃𝑃

𝑋3

HP

LP

𝜃3

𝜃𝑐

Optimization

##30Arrangement

##31Arrangement

##32Arrangement

##33

Conclusion

##34

O1. EH unit

• Design integration including alternative cooling solutions

• Performance evaluation internal gear vs external gear design

• Identification of tolerances and fabrication process

• EH Testing and verification of performance

O2. EH module

• Space limitation on the demo vehicle for applications

• Simultaneous actuation of multiple actuators

• Prototype implementation and testing

O3. Technology Demonstration

• Supervisory controller for energy management

• Zero emission mode of operation

• Integration of energy generator and power electronics

• Performance measurements

Remaining challenges