Mr. Philip C. Irwin Profile

Philip C. Irwin

at Jet Propulsion Lab

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Proceedings Article | 13 December 2002 Paper

Real-time control using an open source RTOS

Philip Irwin, Richard Johnson

Proceedings Volume 4848, (2002) https://doi.org/10.1117/12.463557

KEYWORDS: Real-time computing, Servomechanisms, Control systems, Databases, Interferometers, Operating systems, Interferometry, Mirrors, Computer simulations, Human-machine interfaces

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Complex telescope systems such as interferometers tend to rely heavily on hard real-time operating systems (RTOS). It has been standard practice at NASA's Jet Propulsion Laboratory (JPL) and many other institutions to use costly commercial RTOSs and hardware. After developing a real-time toolkit for VxWorks on the PowerPC platform (dubbed RTC), the interferometry group at JPL is porting this code to the real-time Application Interface (RTAI), an open source RTOS that is essentially an extension to the Linux kernel. This port has the potential to reduce software and hardware costs for future projects, while increasing the level of performance. The goals of this paper are to briefly describe the RTC toolkit, highlight the successes and pitfalls of porting the toolkit from VxWorks to Linux-RTAI, and to discuss future enhancements that will be implemented as a direct result of this port. The first port of any body of code is always the most difficult since it uncovers the OS-specific calls and forces “red flags” into those portions of the code. For this reason, It has also been a huge benefit that the project chose a generic, platform independent OS extension, ACE, and its CORBA counterpart, TAO. This port of RTC will pave the way for conversions to other environments, the most interesting of which is a non-real-time simulation environment, currently being considered by the Space Interferometry Mission (SIM) and the Terrestrial Planet Finder (TPF) Projects.

Proceedings Article | 24 July 1998 Paper

Hardware design and object-oriented hardware driver design for the Real-time Interferometer Control System Testbed

Philip Irwin, Renaud Goullioud

Proceedings Volume 3350, (1998) https://doi.org/10.1117/12.317190

KEYWORDS: Sensors, Actuators, Servomechanisms, Control systems design, Interferometers, Control systems, Software development, Clocks, Electronics, Ferroelectric materials

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Since modern astronomical interferometers require a large number of sensors and actuators for closed-loop control of opto-mechanical components, reconfigurability of the hardware is a strongly desired feature of interferometer control software. In order for software control systems to access hardware with a standard interface and be easily reconfigurable, a layer of software is needed to communicate with the hardware driver software that is modular. If the details of the hardware configuration can be abstracted from the controller software, moving a device to a different I/O board or channel becomes a much easier task. Device mobility is important when testing the performance of computer and instrument hardware, and controller software; it also makes the software much easier to reuse in different instruments. Object-oriented programming provides a model that permits the abstraction of this hardware driver layer. The JPL Realtime Interferometer Control System Testbed (RICST) has developed hardware driver software that employs an object- oriented paradigm and allows relatively simple reconfigurability of devices and I/O boards. This scheme is especially useful since RICST is developing software for use by multiple projects. The top level of the class hierarchy includes Boards, Channels, Channel Banks, Clocks, and Interrupts; these abstract objects provide a common interface for control software to communicate with the hardware.

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