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The 'plastic dog, as the system was named, was a series of steppers, tubes, reservoirs and sensors specifically designed to simulate the complexities of a cardiovascular system. When in full, closed loop control, the system would pump water through a series of lines and reservoirs, all with their own independent variables (varying volumes, pressures, etc) simulating blood flow. All key hardware components represented a set of variables in a series of equations modeling the cardiovascular system. The system was specifically designed for training and educational purposes at a renowned biomedical institute.

The challenge was two fold. First, replace an antiquated set of hardware components (stepper motors, controllers, switches, transducers) that dated back to the late 60's with modern day hardware and components. Second, replace an old C program with a feature rich LabVIEW control application.


All hardware was replaced with modern day components, ensuring that all control (and feedback) variables could be easily managed via a low cost National Instruments MIO data acquisition card. This included stepper motors and controllers, custom built signal conditioning circuits for medical-grade pressure transducers and a new, 12 bit MIO data acquisition card.

The software consisted of three main interfaces: calibration, simulation (real-time control mode), and troubleshooting.

Upon startup, the application performed an automatic calibration. Water flow and levels (resulting in corresponding pressures) had to be accurately calibrated to ensure proper operation of the apparatus.

In simulation mode, a user interface was specifically designed to provide feedback to users (students) while the apparatus was functioning. Graphs of pressure over time represented both venous and arterial pressures, particularly when affected by external stimuli. During runtime, certain configuration adjustments could be made, all for the purposes of demonstrating real-life conditions of a cardiovascular system.

Given the number of moving parts in this apparatus, it was useful to have control over (or read from) components on an individual basis (i.e. move stepper A to position N, monitor the effects of valve B on pressure D, etc). This allowed for tweaking of individual components to achieve better closed loop performance.

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