Xerox uses MathWorks tools to develop prototypes of their printers and test their control strategies.
"Simulink and Simulink Real-Time let us simulate the printer at various levels," says Dr. Krucinski. "Conveniently exchanging simulated components to real components lets us experiment quickly."
Engineers use Simulink® to model the printer’s electronic components, including DC motors, solenoids, sensors, and gates that guide the paper flow for duplex printing. This model of the printer serves as the plant model for subsequent control system development.
Xerox verifies the printer plant model by running simulations with Simulink. They use MATLAB and System Identification Toolbox™ to analyze experimental data from actual printers. After comparing the data, they tune the models so that the results match.
Using Simulink and Control System Toolbox™, Xerox designs the controllers for the DC motors, gates, and roller releases. They use Stateflow® to model operating modes and measure the trajectories and velocity of the paper.
"Stateflow lets us easily model state machines to facilitate specific activation times, which are critical to moving the paper along the path correctly," says Daniels.
They verify the operation of the controllers by combining the controller model with the plant model using Simulink configurable subsystems. Simulink Coder™ is used to generate code for the controller and the plant. The Simulink Real-Time plant system enables them to run real-time, closed-loop experiments on the hardware-in-the-loop, simulated plant to validate prototype controller operation.
"When the controller runs, it’s unaware of whether it’s connected to a real or simulated plant," explains Dr. Krucinski. "Even while the machine is being built, we can exchange half the plant with the real plant and continue simulating the second half of the plant that is yet to be built."
Because Simulink Real-Time uses flexible PC configurations, Xerox runs experiments with smaller printers using an office PC containing two I/O cards. For larger applications, they use a PC with a large expansion chassis that supports up to 19 off-the-shelf I/O cards.
"MathWorks tools let us quickly produce reference plots and replace a configurable block with a real hardware block to collect experimental data. We can then compare graphs to validate results," says Dr. Krucinski. "The massive amount of data logging and signal interrogation that these tools handle is amazing."
The Xerox Innovation Group is now working with product divisions to implement the controller software in their printers.