In FC, one will thus find functions like path preparation and interpolation, path servo control, inverse kinematic transformation, and joint servo control. In NF, functions include proprioceptive and exteroceptive sensor data processing (SDP), and process-, or device-, and control-oriented data processing (PODP, CODP, respectively). Further details on this ARM can be found in (Putz and Mau, 1992), where it has also been shown that the most prominent control concepts can be well represented as certain instantiations of this general architecture.
For given user requirements (actions to be executed for a specific control application), the CDM recommends that the functional requirements should be derived according to the ARM framework. The resulting functional architecture (logical model) of the control system is called the application architecture (AA). An example is given in Section 4. In the following sections, the design of an industrial controller is developed following the CDM principles and guidelines.
3. ACTIVITY ANALYSIS FOR
INDUSTRIAL ROBOTS
Activity analysis performs a functional analysis of the application process(es) in order to define what has to be done by the robot (including the controller) under design. According to the CDM, the result of the activity analysis is the list of the activities (tasks, actions) the robot should be able to execute.
The activity analysis for industrial robots has been based on available teclmical and scientific documentation, and especially on the expertise of engineers from COMAU Robotics, the major Italian robot manufacturer and FMS integrator, who were extensively interviewed. Potential new applications have been carefully investigated with respect to their technical feasibility and commercial relevance for the immediate future. It has been found that it would be commercially interesting to improve tile programming and control capabilities of the next generation of robots to allow easier and more effective application to tasks like polishing and deburring, arc-welding, peg-into-hole and conveyor- tracking. Such applications, in fact, require capabilities to generate a trajectory on-line or to control the interaction (force) with the environment that are not available in current industrial controllers. Sometimes they are tackled in industry using compliance devices such as remote center compliance (RCC), or very accurate (but expensive and inflexible) positioning mechanisms of the working parts, or special sensorized flange-mounted actuators that compensate for positioning errors (e.g., for arc welding) or for high contact forces (e.g., for deburring).