Controls, Modeling and Simulation |

received one Christmas. Science does lead us to truthful answers about nature but for me the factors of mystery,

exploration and discovery have been equally important. Connecting mathematical models with physical reality

eventually became my main interest, and I suppose this led me to pursue my career in feedback control.

Feedback is an amazing device. It exists in nature, but can also be synthesized to meet practical needs. Engineers can

design and apply feedback to a system and incredibly influence how it will respond in terms of stability, speed and

accuracy. For me, the most interesting aspect of control engineering has been modeling and simulation of the systems

themselves. Models, expressed in terms of mathematics help explain how systems work. Modeling not only provides a

foundation and direction for control design, but also serves as the key to unlocking a fundamental nature of how

systems work. Modeling requires a firm knowledge of the underlying physics and accordingly the mathematics required

to express them, but with the power of modern simulation tools, models can be realized in ways that widen perspective

and deepen our understanding as well as offering ways to easily express their behaviors to others. With the power of

simulation we can reveal hidden worlds much like what can be explored under the microscope.

Control Systems & Simulations Specialist

Solutions of Westford, MA. With VisSim, models can be easily and rapidly expressed as a simulation but it also provides the control engineer with an incredibly

easy to use real time interface to sensors and actuators. These two capabilities enable a low cost hardware-in-the-loop tool for rapid prototyping and feasibility

testing. VisSim helps the Control Engineer to build and visualize systems and to rapidly synthesize control solutions using a complete suite of functional

libraries. VisSim provides a full, hybrid simulation environment of continuous and discrete time components. VisSim's intuitive methods for connecting and

configuring functional block diagrams allow rapid construction of conceptual simulation experiments. Compared with other simulation tools, VisSim leads the

way in terms of usability, performance and cost. Let's look at some of the examples where I've applied VisSim.

mechanical ventilation for critical care patients. Much of my work in

controls and simulation has been for medical devices and especially for

critical care ventilators. VisSim provides a simple simulation platform for

developing linear parameter varying systems that closely model the

nonlinear behavior of compressed gas flow in the ventilator tubing and

patient airways. Models have become so reliable that most control

solutions can be developed without actual hardware or at least to the point

where only minor adjustments are required for specifying final design.

Having worked problems in VisSim for at least several ventilator

companies, successful reports spread through the industry and VisSim

has become a leading choice for simulating lung dynamics and ventilator

controls.

In 2001 I achieved an exciting breakthrough in developing an adaptive

control method for pressure based ventilation. This development and the

hardware in the loop results were largely possible because of VisSim.

These results were published in the proceedings from the 2001 American

Control Conference meeting at Arlington, Virginia.

by direct visualization of structures. The block diagram illustrated

above is used for real-time calculation of the covariance matrix for a

recursive least squares estimator. This structure was synthesized and

operating in a few minutes time. This diagram illustrates the

visualization benefit not offered by coding. Each wired connection in

the diagram can be 'probed' by a mouse click to evaluate operation

while the diagram runs or at any desired stopping point.

Email Mike Borrello at stablesystems@ieee.org (619) 889-5452 |

visualize simulation results. The 3D plot to the right illustrates an isometric view

of a ballistic projectile trajectory with drag forces in a gravitational field

systems that include both continuous and discrete

time components. The plot on the left illustrates an

example of hybrid simulation of IGBT switch states

in a 3 phase PWM power converter together with

one of the normalized phase voltages. VisSim

version 8, released in 2011 now also offers UML

state chart tools for simple synthesis of state

machines.

fern leaf was generated in VisSim

using an 'Iterated Fractal System' or

IFS of equations. Fractals have the

property of self similarity over scale,

and for the fern leaf this self similarity

is apparent as one views the leaf

segments at finer and finer

magnifications using the zoom feature

in the VisSim plot block.