Eager Evaluation Considered Harmful

In real-time systems potentially unbounded loops and lazy (late) evaluation are often avoided in order to improve predictability. This paper will show that a commonly suggested way to implement semaphores can lead to unnecessary blocking of high-priority tasks. It also presents a scheme with lazy evaluation and (potentially) unbounded loops that gives less blocking of high-priority tasks

Flexible application development and high-performance motion control based on external sensing and reconfiguration of ABB industrial robot controllers

New robot applications increasingly require external sensing to accomplish robustness and performance despite the variations and uncertainties that come with the increasing demands on flexibility for manufacturing of customized products. The demands on productivity then require high performance, which for well known feedback-control reasons means short response times from external process event to reaction on the robot motor control. The need for high- performance sensor interfaces connected to the motion control without excessive buffering and computations has therefore gained increasing attention over the last decade. Apart from high sampling frequencies and short latencies, there are also engineering aspects to consider. Control engineering tools should be possible to utilize, additional computing power is better connected via real-time Ethernet connections, and all interfaces should check compatibility without sacrificing performance. Furthermore, all that should preferably coexist with the original system, superimposing the effects on external sensing while still maintaining safety and consistency of data. The reason is that the original control software is model based and built on millions of lines of C-code, and tested beyond the possibilities of a research lab. Such a system has been accomplished for control and application development using ABB robots. A short description of the system is given, and its use for application/control development is exemplified. User specific feedback control can be done easily with short sampling periods and less than 1ms of latency from sensing to motor reaction

Laboratories and Real-Time Computing

The paper describes the approach used at the Department of Automatic Control at Lund Institute of Technology to maintain a high level of practical laboratory experiments. The Department integrates laboratory experiments into its control courses. If the laboratory exercises are properly organized and the student volume is sufficiently large, it is possible to combine a high level of practical laboratory experiments in control education at a reasonable cost. The use of off-the-shelf hardware and open-source software are important, With desktop processes, it is possible to achieve high utilization of lab space and high student throughput

Garbage collector interface

The purpose of the presented garbage collector interface is to provide a universal interface for many different implementations of garbage collectors. This is to simplify the integration and exchange of garbage collectors, but also to support incremental, non-conservative, and thread safe implementations. Due to the complexity of the interface, it is aimed at code generators and preprocessors. Experiences from ongoing implementations indicate that the garbage collector interface successfully provides the necessary functionality in an efficient way

On the Integration of Skilled Robot Motions for Productivity in Manufacturing

Robots used in manufacturing today are tailored to their tasks by system integration based on expert knowledge concerning both production and machine control. For upcoming new generations of even more flexible robot solutions, in applications such as dexterous assembly, the robot setup and programming gets even more challenging. Reuse of solutions in terms of parameters, controls, process tuning, and of software modules in general then gets increasingly important. There has been valuable progress within reuse of automation solutions when machines comply with standards and behave according to nominal models. However, more flexible robots with sensor-based manipulation skills and congnitive functions for human inteaction are far too complex to manage, and solutions are rarely reusable since knowledge is either implicit in imperative software or not captured in machine readable form. We propose techniques that build on existing knowledge by converting structured data into an RDF-based knowledge base. By enhancements of industrial control systems and available engineering tools, such knowledge can be gradually extended as part of the interaction during the definition of the robot task

Efficient Java™ monitors

In most real world systems, objects vastly out- numbers threads. This paper shows how this characteristic can be used to implement eficient JavaTMmonitors in a way that reduces the num- ber of needed monitors to be equal to the number of threads, while fulfilling the Java™synchronized semantics. Some additional benefits related to prior- ity inheritance and hierarchical resource locking will also be briefly explored