Research Group - RRG
HW/SW architectures for rapid prototyping of digital controllers
Prototyping can be defined as: A type of development in which emphasis is placed on developing prototypes early in the development process to permit early feedback and analysis in support of the development process.
The implementation of a prototype starts from an idea which is then developed in a project phase, where several alternative solutions are considered to achieve the desired functionalities and specifications. Design relies on technical competence and objectives; several tools can help the designer to practice that competence and to define the objectives in details.
Using a Personal Computer in the prototyping phase as a replacement of traditional technical tools is a common practice today. One of the most important features of the PC is its ability of virtualizing the objects and the procedures to build them. For example, the computer graphics allows visualizing whole inhabited environments in extreme details and verifying the design hypothesis; or, it is possible to try to combine some graphical objects representing mechanical parts, starting from the drawings of such parts, to test their functionalities.
A major interest in prototyping derives from the possibility of knowing the influence of design solutions before the final production phase. In manufacturing, where small technological objects are often produced in large quantities, prototyping allows building trial versions in order to verify a subset of functionalities, before the cost of possible design errors grows up due to the large number of manufactured parts. In such a situation the PC can be useful since it automates the large number of procedures involved in the construction of the prototype.
In more general terms, the prototyping process makes easier the application of specific methodologies from different technological fields embedded into a real or virtual instance of a product. These aspects are today one of the major issues in control design for advanced mechatronic equipments and robotics. In the field of industrial robotics there are several kinds of prototyping processes; a manipulator embodies different technologies and competences: mechanical, electronic and electrical issues merged with automatic control and computer science competencies for a satisfactory design of the whole machine.
The aim of prototyping is often the implementation of new control algorithms or architecture allowing better performances at lower costs in well defined operating conditions. The so-called rapid prototyping is a methodology which allows going in a short time and with limited costs from the general idea to the realizable solution. After the prototype design is tested on the real equipment, one must be able to repeat cyclically the same procedure with only a marginal additional effort.
The prototyping process consists of a set of phases, often technologically very different. This fact complicates in a remarkable way the transmission of information, especially when formalisms and techniques used before the PC advent are involved. Rapid prototyping must be based on a friendly and homogeneous development environment, which should allow the designer to concentrate on conceptual problems freeing him/her from the tedious practical aspects involved in the progression from the idea to the prototype.
The PC plays a major role hosting the interactive environment allowing to develop many of the rapid prototyping process phases, such as for example:
The last point introduces a problem that is common to all the environments where automatic controlled evolution of physical phenomena is needed, i.e. real-time requirements.
Industrial robots are supplied with a controller cabinet containing hardware and software systems for control and supervision. Due to industrial secrecy, safety requirements or, sometimes, technological backwardness, these systems are closed to modification by the customers. On the other hand a controller presents many critical aspects due to the simultaneous presence of components with contrasting real-time requirements.
The user of a prototyping
system should have at least the possibility to interface the original
control environment, and in many cases partially or totally substitute
it. Therefore it is necessary to pay attention to the real-time issues
in order to avoid interferences with the native architecture, especially
when it is necessary to replace important functionalities.
Different HW/SW architectures where developed during the last few years, in a test-bed plant consisting of two planar arms driven by brushless motors. Since the plant was manufactured by IMI, a US mechatronic firm, it is simply known as the "IMI robot".
A detailed description of this plant can be found here
Different solutions were implemented
2005 04 16
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