Hardware in the loop test stand
An important issue in constructing hydraulic systems is evaluating the compatibility with the application. The vast field of
use for hydraulic systems in mobile applications is a heavy argument for using software in studying the dynamics of the machine.
Main idée
Emulating the hydraulic system from valve to actuator makes
analyze of the system possible under laboratory conditions.
The environment must also be emulated as load and inertia.
This project has considered a forwarder crane application of
the L90LS hydraulic valve. Large flexibility in changing valve
configuration, crane geometry and mass is another reason for
using HWIL (Hardware in the loop) in this case.
Erik Axelsson: Project leader
Solution
The rig is designed in two main
parts. The HWIL cylinder on one side
represents the actuator in the real
machine. The cylinder is controlled
by a L90LS valve model, connected
to a pack of servo valves mounted
on the rig. The load cylinder on the
other side represents the forwarder
crane. A servo valve realizes the
model states and forces the HWIL
cylinder on the other side to follow
the model behaviour. These two
parts were integrated by a user interface for control of the valve
Jonas Ek: Crane emulation
Markus Ockborn: Valve emulation
Controllers
Important issues in this project were
running the time critical controllers in
real time during control and measurement.
Results
The charts show the results from tests
made in the test stand. A step was
made with the HWIL valve. The upper
chart shows the response of the crane
model. This response is the reference
signal to the controller. The middle chart
shows how well the cylinder stroke corresponds to that signal. In this case it
occur a control error showed in the
lowest chart.
System overview