Virtual tools for modelling and designing hydro- pneumatic ... · Napoli 27 Giugno 2016 – New Trends in Fluid Power, Design and Simulation Symposium Virtual tools for modelling

Engineering Department Enzo Ferrari – University of Modena and Reggio Emilia

Napoli 27 Giugno 2016 – New Trends in Fluid Power, Design and Simulation Symposium

Virtual tools for modelling and designing hydro-pneumatic suspension systems for off-road vehicles

Massimo Borghi, Barbara Zardin Laboratorio di Idraulica del Veicolo – Fluid Power Lab

DIEF Engineering Department Enzo Ferrari University of Modena and Reggio Emilia



OUTLINE OF THE PRESENTATION Introduction: AGT suspension

system Reference vehicle Modelling Experimental test Results Conclusion and Future works



SUSPENSION OF AN AG TRACTOR ROLE: to isolate the suspended part of the vehicle by dampening

vibrations in very different operating conditions (comfort & handling).

To separate the sprung mass from the unsprung one. CHARACTERISTICS: “elastic/spring” element: stores/accumulates energy “damping” element: dissipates energy



Design tasks Critical Issues: Big weight, position of the centre of gravity, static load changing as function of the equipment, dynamic load transferring from back to front axle, “high” vehicle speed

EVOLUTION from rigid axle to front suspended axle + cabin suspension INTERNATIONAL STANDARDS on vertical acceleration peaks amplitude and frequency (dangerous values in the 1-5 Hz range)

EXPERIMENTAL TESTING OF THESE FUNCTIONS AND TUNING

OF THE CONTROL ON DIFFERENT OPERATING CONDITIONS IS TIME

CONSUMING

SUSPENSION OF AN AG TRACTOR



Driveline

Front Chassis Front Axle

Case IH Puma 215 CVX

Panhard Rigid Bar

Rear Axle

VEHICLE



SUSPENSION OF AN AG TRACTOR



MODELLING FIRST APPROACH: LUMPED PARAMETER Hydraulic system + Quarter Car Model in LMS Imagine.Lab AMESim + Control Unit in Simulink

P ML

HYD CTRL



HYDRAULIC MODEL EHPV 3D model

Pilot Pin

Pilot Seat

Main Poppet

Contact Model

Hydraulic model details

EH

PV

FC

AM

ES

im M

odel



-ideal gas -heat exchange with the environment modelled using a time constant (Highsimilar to adiabatic; Lowsimilar to isothermal process)

HYDRAULIC MODEL



VEHICLE SETUP & TESTS

VEHICLE SETUP: • CAN Network • Accelerometer • Pressure Sensor VEHICLE DATA • Tire Pressure:

• 1,2 bar (Front) • 1,6 bar (Rear)

• Weight distribution • 42% Front – 58% Rear

• No Stabilizing Mass

SUSPENSION SETUP • SOFT • NORMAL • HARD



RAISING LOWERING

Raising valve [%] Lowering valve [%]

TESTING: STATIONARY

STATIC TESTS LEVELING

W/O PARK LOCK



SENSITIVITY ANALYSIS Load distribution Coulomb friction coefficient Stiction friction ceofficient

Friction concentrated on Panhard Bar

NUMERICAL vs EXPERIMENTAL: TUNING AND ANALYSIS



TESTING: DYNAMIC DYNAMIC TESTS BUMP TEST 7 / 10 kph

Valve 31 30___ SOFT 100% - 80% NORMAL 55% - 67% HARD 37% - 37%

Displacement

Pressure



COMMENTS AND LIMITS Qualitatively good comparison the influence of: load distribution configuration, suspension damper setup, modification and test of the Skyhook control (control logic), time responses of the damping valves. The dangerous vertical acceleration frequency values in the bump test in numerical/experimental analysis are the same (0-3 Hz), as well as the frequency correspondent to the peak of acceleration

1 Hz 1 Hz

BUT: No pitch, yaw, roll movements No modelling of the tyre-ground interface



FULL CAR VEHICLE MODEL: Bump Simulator Tyre Model Driveline & Chassis Panhard Bar & Rigid Bar Front Axle Hydro-Pneumatic Suspension

STEP FORWARD

Contact point trajectory

calculation



CONDITION Transmission in NEUTRAL

No CVT Dynamics Constant velocity (7/10 kph) Suspension in NORMAL mode

STEP FORWARD



FINAL COMMENTS A tool integrating a multibody full car model of the tractor and the

detailed hydraulic model of the suspension system has been realized

Experimental tests on the vehicle have been useful both to characterized some critical aspects (friction) and to validate the model

An experimental – numerical comparison, considering the leveling test, the hysteresis test and the bump test has been performed.

A good correlation with experimental data has been found by the model analysis

We are working to optimize and improve the model, especially for: Contact between wheel and terrain Thermal effects on accumulator

Documents

Virtual tools for modelling and designing hydro- pneumatic ... · Napoli 27 Giugno 2016 – New Trends in Fluid Power, Design and Simulation Symposium Virtual tools for modelling