Some people have the guts to go skydiving. I’m not one of them. Though I sincerely admire those who enjoy this sport, the only way I’m even thinking about jumping out of a plane is if it’s barreling toward the ground with no hope of recovery. Despite my misgivings about the thought of leaping from a perfectly functioning aircraft, skydiving is clearly an exhilarating experience and I would certainly like to have knowledge of it — albeit in a way that doesn't require me to exit a plane before it is safely on the ground.
Apparently I’m not alone, which explains the popularity of vertical wind tunnel simulated skydiving operations such as SkyVenture. Since 1998, SkyVenture has designed and built what are considered by many to be the most advanced skydiving wind tunnels in the world. The company’s patented wall-to-wall airflow technology creates “safe indoor flight for Special Forces military teams, professional skydiving teams, and birthday parties for 10 year olds,” according to the company’s literature.
So what does all this have to do with industrial automation? Well, behind the fun of the freefall experience in a SkyVenture wind tunnel are CC-Link industrial communication networks and Mitsubishi programmable logic controllers (PLCs) and variable frequency dives (VFDs).
See a video of John Wozniak of the CC Link Partner Association testing out SkyVenture’s wind tunnel freefall experience in the image box in the upper right portion of this article.
A few years after building its first tunnel in Orlando, SkyVenture sought a control system that allowed for easier operator control and on-site installation. In 2005 SkyVenture incorporated CC-Link communications to improve the operator interface experience as well as the control operation and installation process. As part of this redesign from an older Modbus platform, SkyVenture also upgraded to a Mitsubishi Q Series PLC. A CC-Link Master card within the Q Series PLC rack is used to control the CC-Link communications. CC-Link is used to communicate with four F740 VFDs using Mitsubishi Electric FR-A7NC CC-Link interface cards.
According to SkyVenture, the company chose CC-Link communication because it “allows a more interactive communication with the drives.” Using one CC-Link communication line, the SkyVenture operator can monitor Volts, Amps, kW, set frequency, and alarms as well as set the operating frequency. Before switching to CC-Link, the SkyVenture wind tunnel operator had to control all of these different functions over 10 or more different communication cables.
SkyVenture’s Seattle installation is one of the company’s more recent additions and features an advanced installation of the controls system that includes communication to smaller VFDs and the use of many more remote I/Os on the CC-Link network. These new SkyVenture tunnels are known as recirculating tunnels, which use four 600hp direct driven 2.8 meter vent-axial fans (rated at 400hp for continuous use). The fans, each weighing 17,000 lbs., are mounted on top of the building to draw air up through the flight chamber at maximum speeds greater than 170 mph – equivalent to a Category 5 hurricane.
In this new, updated design, the CC-Link network is also used to control the air temperature in the flight chamber by opening and closing 20-foot wide by 10-foot high doors. These doors are connected to linear actuators driven by Mitsubishi VFDs communicating on CC-Link. The information on the status of the doors is also displayed on the human machine interface (HMI) used by the operator.
Additional I/O monitored and controlled by CC-Link includes the air speed in the chamber, which is displayed on the operator interface. The interface also provides predefined flight time options that the operator selects and is used to determine the remaining flight time, which is also displayed. This air speed and flight time information are displayed on another HMI monitor used as a guide by those in the flight chamber, as well as any spectators.