Hardware-in-the-Loop
Simulation of Wheel Loader
The purpose of the project is to develop a Hardwarein-the-Loop Simulation model of one of their wheel
loaders. As the name HWIL suggests, it means that
hardware is used in the simulation loop as oppose to
the pure software simulation normally used. In this
project, the hardware is the lifting hydraulics system,
which consists of a hydraulic pump and lifting cylinder.
Test Rig
The hardware in this HWIL simulation is the weel loaders lifting
hydraulics. The test rig used does not actually have a lifting cylinder, but two hydraulic motors. These can though be used to imitate
an asymmetrical cylinder like the lifting cylinder of a wheel loader.
The test rig consists of three important sections:
The drive side is used to describe the diesel engines rotational speed
and is controlled by the simulation model of the diesel engine.
The lifting hydraulics section consists of the hydraulic pump connected to the drive side shaft and two hydraulic motors. These motors are used to imitate the lifting cylinder. This is done by letting
the flows in the lifting hydraulics section in the test rig answer to the
flows in the real lifting cylinder.
Project Members: Tommy, Andreas, Niclas and Tobias
xPC Target
For interaction between the operator, the simulation models and
the test rig a system called xPC Target is used. This system consists of two computers (Target and Host):
The Target computer is equipped with a real-time operating system and data acquisition and controlling cards. It is on this computer that the simulation models are run.
The Host computer is used for communication with the Target.
The operator can control the simulation, and it is here the visualization of the simulation is run.
The load side of the rig consists, like the drive side, of a servo valve
controlled hydraulic motor that is used to describe the load that acts
on the lifting cylinder.
xPC Target Overview
Visualization
Hydraulics in Wheel Loader
To see what is happening in the simulation we need to visualize
the wheel loaders moovments. To do this we use positions given
from the mechanical models.
Hydraulics in Test Rig
Simulation Models
When building the simulation models there are two main things to think
about:
The first thing is to make the structure
of it modular, so that if someone in the
future would like to exchange one of
the models. This is solved by modeling
each component in the wheel loader separately.
The second thing is that all of the models
need to run in real-time. This because
of that the models will control the test
rig while they are executed. This means
that the models can’t be to complex.
Models:
• Drivetrain
o Diesel Engine
o Fly Wheel
o Torque Converter
o Power Shift Gearbox
o Propeller Shaft
• Wheels and tire
• Chassis
• Lifting Framework
• Hydraulic Systems
o Pump for Tilting
o Valve for Tilting
o Tilting Cylinder
• Ground
• Gravel (As Load)
Control Panel and Visualization
Controllers
To control the rotational speed of the drive- and load side, controllers with feed forward of the reference value are used. To get
rid of the stationary error a PI-controller is used after the feed
forward.
Project members:
Tommy Fredriksson, Niclas Gunnarsson,
Andreas Laghamn & Tobias Ragnarsson