Linux at the University

As the economy of the United States transitions from the Industrial Age to the Information Age, students from all engineering disciplines are required to enable the automation and control of large and small industrial production processes. The per dollar cost of storage media, CPU cycles and interface hardware continues to decline, allowing research agencies and for-profit companies to implement automation of their production processes in an effort to decrease costs and increase profit margin. At the College of Engineering and Sciences, located on the main campus of the University of Colorado, a new teaching paradigm has been realized with the completion of the Integrated Teaching and Learning Laboratory (ITLL). The ITLL was built as a resource for students of all engineering disciplines to facilitate the transfer of theory learned in the classroom to actual practice in the laboratory, in an effort to teach real world engineering and scientific skills.

The ITLL provides the resources to allow students to design and build complex engineering projects. A typical lab station is shown in Figure 15. Each of the lab stations is equipped with a Hewlett-Packard Vectra PC with a 500MHz Pentium-III processor, 384MB of RAM, an 8GB hard drive, the usual NIC and a National Instruments analog and digital data acquisition card. Several of the 80 available systems have been configured to boot Linux and RTLinux, in addition to Windows NT. Standard test equipment at each lab station includes a waveform generator, digital multi-meter, variable-voltage power supply and oscilloscope. The breakout panel provides easy access to analog and digital IO signals and to signal-conditioning hardware. The availability of sophisticated test equipment, coupled with the capabilities of the Linux and RTLinux operating systems, has enabled students to design and construct complex, real world applications integrating both hardware and software to accomplish a specified engineering or scientific task.

Figure 15. An ITLL Workstation Running Linux/RTLinux.

One such project is the University of Colorado's Robotic Autonomous Transport, a.k.a. the RATmobile, shown in Figure 16. The RATmobile is an unmanned ground vehicle (UGV) that navigates autonomously by sensing static and dynamic features within its environment. This vehicle was designed entirely from scratch by a group of undergraduate and graduate students from several engineering disciplines with supervision and guidance from members of the Aerospace department. Design and construction of the vehicle is truly multi-disciplinary, calling upon the theory and expertise of mechanical, electrical, aerospace and computer sciences.

The vehicle uses miniature video cameras mounted on the front to supply visual information concerning the surrounding environment. Static and dynamic obstacle detection is supplemented by an array of ultrasonic sensors. The sensed environmental conditions are combined into a local coordinate frame and then translated into a world representation map that contains the totality of the robot's knowledge concerning its environment. Depending upon the task at hand, the robot is able to make use of different navigational algorithms to traverse to a desired destination.

One such navigational mode allows for the vehicle to navigate an obstacle course that is delimited by painted white lines on a large field. The lines are approximately ten feet apart with straightaways, sharp curves and bends and even some occurrences of missing lines, which require that the navigation algorithm predict the desired vehicle direction based upon historical information. A second navigational mode makes use of differential GPS information for precise assessment of the robot's position in a world reference frame. In this mode, the vehicle has a priori knowledge of its static environment and can navigate to a predetermined location while avoiding unmapped or dynamic obstacles. Different navigational strategies, such as the optimization of path length or required path energy, are easily implemented.

Linux was chosen as the operating system for this project because it met all design requirements, allowed for a multi- user development environment and was free, which is of concern to students with a limited project budget. The capability of the multi-threaded software control architecture provided by Linux allows for easy implementation of differing vehicle capabilities. The primary functions of the vehicle, visual image acquisition; obstacle detection information acquisition; combination of input sensory data into a world representation; and the determination of the required navigational control outputs of velocity and steer angle, are all abstracted to different threads. If necessary, the CPU scheduling policy associated with different processes can be altered from the default scheduler, which optimizes for the average case, to allow for improved real-time performance under the standard Linux OS. In process control systems, where millisecond and below guaranteed scheduling is required, a real-time Linux variant, such as RTLinux, can be used.

Figure 16. The Robotic Autonomous Transport (RATmobile)

The ITLL stations, running either Linux or RTLinux, are also used in a class emphasizing hardware/software integration skills to undergraduate and graduate students. Advanced programming constructs, in the C and C++ languages, are required by laboratory exercises that emphasize the integration of real hardware, such as motors and micro-controllers. This allows students to develop confidence and expertise not just in proper software programming practices, but in combining control hardware with the standard PC. Examples of final student projects (all using Linux or RTLinux) in this class include:

Using the Linux OS and user-configurable development environments as a basis, we are able to impart a greater breadth of knowledge to our students, which is applicable to real world engineering problems. That is a true accomplishment whose accolades belong to the numerous kernel and development programmers whom have contributed to the power and success of Linux.

Linux also serves as a powerful teaching tool within our Computer Science department. The free availability of the Linux OS and associated development packages have opened the doors to a greater variety of course content in classes pertaining to Systems Administration. With a free operating system and the availability of cheap PC hardware, students have the ability to configure and administer all aspects of their very own system within a university computer lab. If something goes dramatically wrong, it is a simple matter to restore the entire disk across a network from a master system. This encourages students to experiment with no disastrous repercussions. Topics such as disk-level file recovery, device installation and management, user and file administration, kernel configuration and networking are all candidates for easily constructed exercises using the free Linux OS as the enabling technology.

Open source distribution of the Linux kernel source tree has allowed courses in Operating Systems Theory to not only teach the fundamentals but, even more importantly, allow the students to experiment with changes to the kernel code. As a result, students are offered a richer set of exercises that can be applied directly to the kernel source and not just on paper. Most assuredly, students will break their systems while experimenting, but system recovery strategies have definite educational value—better now on a cheap PC running Linux than on some multi-million dollar platform in the future. Having the kernel source allows for in-depth exercises in far-ranging topics including management of processes, resources, devices, files and memory, as well as implementation of kernel-space processes as Linux modules, scheduling policies and priorities, and fundamental synchronization methodologies. Linux enables a richer and more realistic educational experience for our students.