Virtual Prototyping Using VTB with HUT
As explained by Researcher Mills Estes
Figure 1. A basic view of the system my research group is working on.
What is Virtual Prototyping?
Virtual prototyping is the process of using a computer simulation to help design real world products and components without having to spending huge amounts of money to create their physical counterparts.
What is VTB?
VTB stands for Virtual Test Bed. It is a computer simulation program that can be used to generate many different accurate models of real world systems, such as anything from basic electrical circuits to sophisticated fuel cell systems.
What is HUT?
HUT stands for Hardware Under Test. It is generally used to describe a component, such as some form of circuitry or perhaps even a DC motor that is being tested. In this case, it would be the test hardware being used with VTB in virtual prototyping.
What Is the Main Focus of the Group's Research?
Our purpose is to design a system that can use a simulation done on a computer to drive real hardware, like a motor or some form of circuitry. Real components use real power (in the form of voltage and current), while simulations only pass numbers that are equivalent to power. The problem that occurs with interfacing the real with the virtual world is resolving the numbers that are equivalent to “virtual power” into real power that can drive physical hardware. This task is done with an H-bridge, which is just a technical name for a voltage-controlled switch, that is controlled by the waveform signals coming from our virtual simulation. Usually these virtual systems are used to test control system circuits to see how well they will work with actual hardware (i.e. HUT). Modern control theory suggests that most control systems require feedback to make them stable, so we need some sort of output signal that we can feedback to the computer simulation. In order to do this, we require an ADC (analog-to-digital converter) to make the output signal readable for our system. And in order to make the entire system work well, we need the system to work at or very close to real time. This real time aspect requires that our ADC be very quick in processing the incoming signal.
What Is the Objective of My Research?
My objective is to make a resizing and filter circuit that will be part of the interface circuit between the output of the analog hardware and the ADC input of the computer. The computer input must be precisely digitized so it can correctly pass the output signal information, and since the output signal is 3 times larger [roughly a 10V analog output compared to a 3V maximum input to the ADC] than what the analog-to-digital converter input of the computer can effectively use, the output signal must be resized. The filtering aspect of this circuit is built in to insure the input will be free of noise and distortion, which can cause the ADC to incorrectly sample the incoming waveform. Once this circuit is constructed, the entire system will be tested for speed, accuracy, and amount of distortion.
Figure 2. Pictures of the schematic and circuit board I designed and constructed.
A More Technical Overview of Our Project
The experiment my group is going to be working on consists largely with H-bridges. An H-bridge is fundamentally a bi-directional toggle that can switch very quickly and with very little power loss. The first part of this experiment will revolve around replacing an analog-to-digital converter (ADC) on our microcontroller. A microcontroller is a board that can be programmed to react to certain impulses and generate some needed output. The impulse to this controller will be a digital version of the analog output of our system created by the ADC. The reason for this replacement ADC is to create a quicker version of our control system so that we can better control our H-bridges. The control system we have created uses traditional control theory practices and is used to drive the error between our input and output signals down to a small value, hopefully to zero (i.e. no error). After this, we will replace the original silicon H-bridges with gallium-nitride versions of the same H-bridge. Silicon and gallium-nitride refer to semiconductor materials that have electrical characteristics of both insulators and conductors. Due to this quality, they have different capacities for dissipating heat energy, with gallium-nitride being the better of the two [which is one of the main reasons for why this project was created]. After this new component is in place, testing will be done on the system and an optional research proposal will be to see if this system can be used in a new version of the class D amplifier, which is the current industry standard for audio amplifiers found in basic home stereos.
Figure 3. The full system my research group is working on, with some physical components shown.