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Student Spotlight continued
Mission Control
The test stand design and development process evolved in several ways. Initially the design team
tried using stepper motors to control valves, but they found this approach to be difficult and unable to provide the necessary feedback. They moved to using pneumatically actuated valves and electric solenoid valves, both easily interfaced with the PLC via
relays. As development continued, more valves were progressively automated, eventually reaching a total of 12.
For instrumenting the test stand and rocket engine, temperature and pressure sensors sourced from AutomationDirect were specified for the neces- sary ranges and service. Industry-standard 4 to 20 mA signals ensured straightforward connection to the PLC and provided reliable signals.
Core automation elements were assembled into
a control panel mounted on-board the test stand (Figure 2). The team designed and fabricated the control panel, using AutomationDirect ZIPLink pre- wired connection cables and modules to facili-
tate field wiring of the devices. The use of a mod- ular PLC and ZIPLink cables provided flexibility for design updates. Other complementary panel fabrica- tion hardware and devices were also obtained from AutomationDirect.
Figure 3: Picture of team remotely operating the test stand. The test stand is remotely monitored by team members.
Test stand operation encompassed several types of functionality including:
• Valve control
• Ignition
• Auto-abort
• Status and data logging
The team developed a human-machine inter-
face for monitoring and control of test operations from a remote operating location, and also used video recording (Figure 3). Complete valve control is generally achieved through timing sequences pro- grammed into the PLC so all actions can be per- formed repeatably and precisely once triggered by the operator. For a typical test session, an opera-
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Figure 2: Picture of control panel.
The team designed, fabricated, and wired a control panel mounted on-board the test stand, featuring an AutomationDirect Productivity2000 PLC, with ZIPLink connector cables installed at the top.
Student Spotlight | Issue 43
tor remotely actuates valves while a techni- cian performs the pro- pellant filling. Once propellant tanks are filled, the technician joins the operator in the control bunker where they set the test parameters.
Before a test
can begin, the PLC enforces that all valves are in the cor- rect state. The opera- tor initiates a test and the PLC takes over
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