Control of a Linkage with an Embedded Pneumatic System
Qualifying Exam Technical Talk, presented 6/18/99
This presents the experimental set-up and controller used to
regulate the pressure inside a small pneumatic piston using two one-way
on/off solenoid valves. The reduction of the transport volumes between
the valves and the piston results in a very short pressurizing time that
is near the same magnitude as the time constants of the solenoid valves.
This makes the traditional approach of flow control using
Pulse-Width-Modulation of the solenoid valves almost impossible.
Moreover, the delays in the solenoid valves depend on flow and pressure
conditions. The control approach implemented considers the four states
it can command to the two one-way valves and predicts the resulting
future errors based on a model of the system. It then chooses the best
command based on these predicted errors. Moreover, the models of the
system used to estimate future errors are adapted to accommodate large
changes in the volume using the Least Mean-Squared Algorithm. Results
show significant improvement over other techniques such as Bang-Bang
control for the worst-case scenario in which the piston is fully retracted.