1. INTRODUCTION The engineering design of a controller must satisfy a large number of requirements and constraints of different natures (e.g, performance, cost, safety and reliability), and it often involves a choice among several equally good solutions. Many factors, also subjective, may influence the choice. The definition of the right product features and the development of a design consistent with them are crucial to the realization of profitable products. The lack and need of a structured and systematic framework to assist this difficult task is well recognized (Astr6m and Wittenmark, 1990). 43233
This study concerns this subject. The design of a new industrial controller is tackled according to a codified methodology, Referring to a state-of-the-art commercial product, the Comau C3G 9000, the first objective of the study is to design a new controller ("next generation", since it should replace the current product) with innovations based on the forthcoming commercial needs and advances in sensor, actuators and information technologies. The design development follows the Control Development Methodology (CDM), a design methodology defined by the European Space Agency (ESA) for structuring the design process of automation and robotics control systems for space applications. Actually, it is a second objective of the study to assess the effectiveness and possible drawbacks of the application of the CDM to industrial problems.
According to the CDM, the design process consists of three major steps. The first step, referred to as activity analysis, defines precisely and formally the tasks the robot has to accomplish. The second one (requirements or functional analysis) establishes the control functions required to accomplish the tasks and the interaction with the human operators. This entails, for instance, the choice of control principles and algorithms, as well as of control and measured variables. The third step (architectural design) concerns the detailed design of the controller hardware and software. The CDM supports the first two steps in particular, supplying principles, methods and tools in order to proceed in a structured and formal way.
The organization of the paper reflects the steps of the controller design process. In Section 2 the CDM is described. Section 3 deals with the activity analysis for next-generation industrial robots. Section 4 discusses, as an illustrative example, the functional analysis for hybrid position/force control, Section 5 outlines hardware and software implementation architectures.