Fineline Solutions was approached to develop a control system for the roof of the Water Polo Arena at the London Olympics. The roof consisted of ten PVC-coated polyester cushions which were inflated with air. The brief was to produce a control system to manage the inflation and pressure inside each of the ten cushions, and also the operation of two independent fan units.
The brief was to produce a set of control boards with the following features:
- Two independent pressure sensors
- General purpose digital inputs (24V logic)
- General purpose digital outputs (24V logic)
- Analogue inputs (0 – 10V)
- Analogue outputs (0 – 10V)
- 24V DC power input
- KNX bus connection for configuration and status reporting
Control board design
The control board was based around a PIC microcontroller, which was used to perform all controller functions. In addition, a KNX communication module was used to send and receive data on the KNX bus. The control board was designed to ensure that all inputs and outputs were electrically isolated from the control processor and KNX bus: this was to ensure that any supply problems, voltage surges or cable damage would not adversely affect the operation of the controller. This was particularly important as the system was required to function long before construction of the venue was completed.
All of the cushions were connected to the main air duct, which was supplied at each end by a fan unit. Each cushion was provided with an air valve, allowing the cushion to receive air from the supply duct, or to be isolated from it.
The control board for each fan unit was used to maintain a constant pressure within the supply duct. A PID loop was used to constantly vary the fan speed based on the difference between the measured pressure and target pressure. If necessary, a second fan in each fan unit could be activated to increase the air flow.
Each cushion was also equipped with a control board. The control board modulated the air valve position to ensure that the air cushion maintained the pre-defined pressure target. In the event that the pressure in the supply duct dropped below the cushion pressure, the controller closed the valve to prevent air loss. In this way, the system could maintain inflation in the roof structure even if the supply duct was broken.
For further information, or to discuss a similar project, please contact Fineline Solutions.