This paper presents the kinematic and dynamic modeling and experimental results with nonlinear adaptive control of the Hexaglide, a new 6 dof parallel manipulator that is used as a high speed milling machine. The dynamic equations in a linear form for use in a nonlinear adaptive control scheme are Þrst derived using a method based on the virtual work principle. These equations are then implemented on a powerful controller for real-time compensation of dynamical forces and on-line dynamic calibration. Experimental results show that the proposed nonlinear adaptive controller is capable of identifying the dynamical parameters and that it outperforms conventional linear axis controllers by far.

Starting from a user point of view the paper discusses the requirements of a development environment (operating system and programming language) for mechatronic systems, especially mobile robots. We argue that user requirements from research, education, ergonomics and applications impose a certain functionality on the embedded operating system and programming language, and that a deadline-driven real-time operating system helps to fulfil these requirements. A case study of the operating system XO/2, its programming language Oberon-2 and the mobile robot Pygmalion is presented. XO/2 explicitly addresses issues like scalabilty, safety and abstraction, previously found to be relevant for many user scenarios. IntroductionIn the mobile robotics community we can observe two approaches to the subjects of self-contained autonomy and real-time. On the one hand, vehicles are used as 'sensors with wheels' where information processing is done either off-board or even off-board and off-line. This procedure offers advantages for the researcher; he can focus on a precise topic without taking into account further complexity due to integration. On the other hand, robots are used as fully embedded systems which provide all means to acquire, process and act on-line and on-board. These systems exhibit a degree of self-contained autonomy which is compatible with application requirements but can suffer from high complexity. The choice of hardware, but particularly the choice of the embedded operating system and programming language is crucial when deciding to face this further application-relevant complexity. In this paper we argue that, when the researcher, the student and the end-user need or wish a certain functionality, flexibility or safety of the robot, properties like real-time capability coupled with a strong typed programming language can help to fulfil these needs. We present a case study of the XO/2 operating system which runs on the mobile robot Pygmalion as an example where exigent user requirements could get translated into a system that facilitates application to a real-world robot. Do we need self-contained systems?Although an unspoken question among many roboticists, we estimate that the majority of mobile robot research platforms in use today could not operate in a fully self-contained mode since their algorithms rely at least partially on wireless connections to off-board infrastructure. Whereas this limitation might not be relevant for research, it will not be acceptable for many applications where operating environment size, economical aspects and safety issues do not allow off-board computing. Autonomy with respect to perception, energy and processing for fully self-contained autonomous decision-making is not an option but should be addressed in its full complexity already as a research topic. Do we need real-time in mobile robotics?When on-board computation is required we are typically confronted with limited computing power. Hence, meeting timing constraints becomes a problem which is present but only ...

The control system of many complex mechatronic products requires for each task the Worst Case Execution Time (WCET), which is needed for the scheduler's admission tests and subsequently limits a task's execution time during operation. If a task exceeds the WCET, this situation is detected and either a handler is invoked or control is transferred to a human operator. Such control systems usually support preemptive multitasking, and if an object-oriented programming language (e.g., Java, C++, Oberon) is used, then the system may also provide dynamic loading and unloading of software components (modules). Only modern, state-of-the art microprocessors can provide the necessary compute cycles, but this combination of features (preemption, dynamic un/loading of modules, advanced processors) creates unique challenges when estimating the WCET. Preemption makes it difficult to take the state of the caches and pipelines into account when determining the WCET, yet for modern processors, a WCET based on worst-case assumptions about caches and pipelines is too large to be useful, especially for big and complex real-time products. Since modules can be loaded and unloaded, each task must be analyzed in isolation, without explicit reference to other tasks that may execute concurrently. To obtain a realistic estimate of a task's execution time, we use static analysis of the source code combined with information about the task's runtime behavior. Runtime information is gathered by the performance monitor that is included in the processor's hardware implementation. Our predictor is able to compute a good estimation of the WCET even for complex tasks that contain a lot of dynamic cache usage, and its requirements are met by today's performance monitoring hardware. The paper includes data to evaluate the effectiveness of the proposed technique for a number of robotics control kernels that are written in an objectoriented programming language and execute on a PowerPC 604e-based system.

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Progress in mobile robotics requires the researchers to access and improve all modules that compose the robot, from low-level mechanical components to highlevel reasoning systems. This paper presents the development process of the robots built at the Autonomous Systems Lab, EPFL Lausanne, Switzerland. Starting from the mechanical and electrical design up to the application, we show the challenges that needed to be faced as well as the solutions that have been devised. The description covers aspects like the operating system and framework, because of its role in the overall safety and dependability of the whole software system, the research as a precondition for innovative products, and the man-machine interface, which is indispensable for conveying information to the user as well as allowing the user to interact with the robot. The issues that have been faced stem from the hierarchical, layered construction of a complex mechatronic product, where the operation of the machine depends on the smooth cooperation of each layer; In the same way, the overall safety is undermined by the least reliable piece building the system. 1 2