Robotics Research Technical Report Operating Systems for Robot Control Classic Reprint

Excerpt from Robotics Research Technical Report: Operating Systems for Robot Control

This paper is a survey of some operating systems primarily designed for robot control systems. Of particular concern in this survey are the systems used at the low end of the control hierarchy. Robotic devices are growing in complexity both in the degrees of freedom to be coordinated and in the sensory input available. For comparison a typical six degree of freedom arm with position sensors for each joint and the Utah/MIT hand which has 16 degrees of freedom with both position and torque sensors for each joint. The complexity of the tasks requested of robot control systems has grown accordingly so that the computing power of contemporary control computers and operating systems is being strained.

Operating systems for robot control systems fall within the category of real-time operating systems. Perhaps the most salient feature of real-time operating systems is preemptive scheduling which means that it is possible for a high priority task or tasks to demand immediate access to the processor so that some real-time constraint can be met. Many real-time operating systems are otherwise normal operating systems with preemptive scheduling added. A characteristic of low level robot control, the servo loop, permits further refinement of the operating system to the point that some of systems discussed in this survey bear little resemblance to normal operating systems. Servo loops demand repetitive and timely service and a robot control system is likely to have many loops. Special scheduling techniques can be used because of the repetitive nature of the loops. The demands of timely service (particularly in high frequency loops of low level control) require a low tolerance for blocking of tasks for indeterminate lengths of time. As a result one finds that queues play a diminished role in the systems presented in this survey when compared to normal operating systems.

The…