UC Riverside
Digital Mockups
Copyright 2011.

"Digital Mockups" is a joint UC Riverside/Irvine research project developing real-time observable/controllable executable models of physical systems. Such real-time models can be used during development/test of the cyber device in cyber-physical systems, such as a medical ventilator, as well as for device-user training. As depicted below, a cyber device can be connected to a mathematical model of the physical environment implemented on a computing platform. That model's implementation represents a "digital mockup" of the physical environment. For example, a medical ventilator can connect to a human respiratory system model, a cardiac pacemaker to a model of human heart electrocardiography, or a satellite might think that it is in orbit when really it is being fed sensor data by an environmental model of space. Digital mockups enable easier testing of dangerous or expensive scenarios, more thorough testing of border cases, fully automated testing, faster testing, reproducible testing, and even a view of what's happening inside the physical system. They are useful for test/development of new devices, for training/education (e.g., training of respiratory therapists on ventilator use), and for reproducing field errors.
Digital mockups can be used directly (typically requiring bypassing a device's transducers and instead interfacing directly to internal device processors) or can be incorporated into hybrid physical/digital mockups.

Synthesis of Models
Complex models commonly run much slower than real-time on normal computers. A key aspect of the project is to compile mathematical models into circuits for real-time implementation on Field-Programmable Gate Arrays (FPGAs). Circuits are a good match for physical models, due to both items involving fine-grained parallel computation and local communication. However, tools for automatically compiling a model's differential equations into circuits do not exist today. We have invented an automated tool flow for compiling high level model descriptions to networks of Processing Elements for real-time execution on an FPGA. See this link for more information.

Digital mockups enable the possibility of observing the internal behavior of a physical system, such as internal pressures in different regions of a human lung during ventilation. Insights from such observation can lead to better designs and to better user training. Furthermore, digital mockups enable the possibility of controlling the physical model: stop, play, fast forward, step, rewind, etc. Another key aspect of the project is to create circuits such that internal values can be observed in real-time, and debug control is incorporated too.

Current digital mockup practice is scattered and ad hoc. Another project aspect involves defining a discipline for digital mockup creation and use.

Publications Links to some of the above papers can be found at Prof. Vahid's publications page.

The below video shows an implementation of a digital mockup for a commercial ventilator device. An FPGA hosts a lung model and
interfaces to internal ventilator processor busses to intercept actuator and sensor commands.


This work is supported in part by the National Science Foundation (CNS1016792) and by the Semiconductor Research Corporation (GRC 2143.001). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation or other supporting agencies.