PSI - Issue 37

Pedro J. Sousa et al. / Procedia Structural Integrity 37 (2022) 826–832 Sousa et. al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 6. Revised pneumatic circuit

In summary, the pneumatic circuit was simplified, leading to a smaller number of components, taking less space but also reducing air leaks. 3. Electronic circuit The main control system was implemented in a printed circuit board, and centred around a dsPIC33EV256GM102 from Microchip Technology. This particular microcontroller was chosen due to its fast 70MIPS core, meaning fast processing and response; 5V logic, enabling direct output of 5V TTL pulses compatible with the high-speed cameras; and diverse hardware modules, which allowed the implementation of core-independent pulses. It had been previously been used by the authors in other projects which shared features with this one, enabling faster development times. The developed architecture and main control logic are shown in Fig. 7.

Fig. 7. Architecture and main control logic of the developed control system

One of the main features of this systems is its controllability from the data acquisition PC, which was implemented using an on-board FT232RL from FTDI, connecting the UART module to a virtual serial port on the computer, which is then used to interact with the developed software. Through this user interface, it is possible to configure the output pulses, select the target pressure and start the procedure. This in turn starts Timer4 and its associated control loop, which is responsible for reading the pressure sensor using the ADC module, controlling the valves using GPIO pins and, when the target pressure is reached, actuate the trigger valve and output two sync signals using the output compare module. The actual pressure when the shot took place is also reported to the user through the computer user interface. The electro-pneumatic interfaces, shown in Fig. 8, are very simple: the chosen pressure sensor includes an analogue output (0~10 V) which only have to be scaled to the microcontroller’s voltage range (0~5 V); the valve control was