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Announcement - Agenda - Paper Presentations

In this paper, we present a distributed system to fill the need for an open architecture for robot control. The system is based on simple processing nodes called Actuator Interface Cards (AIC). The hardware is composed by an AIC for each joint of the robot. Each AIC contains a dspPIC processor and can drive a D.C. motor with nominal voltage ranging from 12V to 60V through a PWM converter. Also, it interfaces with an incremental encoder performing quadrature decoding. A CANbus is used for real-time data transfer such as sensor measurements and actuator commands, between each AIC and a host PC. A real-time library running in the host PC, models the devices embedded in each AIC and supports all the possible operations, for example: shutoff and voltage setting for the motors and reading of count for encoders. This library also implements the communication with AICs using a protocol where a priority is associated with each command and card, thus ensuring the real-time requirements. The library accesses the AICs through CANbus with a real-time driver. A simple PID controller was implemented as a hard real-time thread in user-space using RTAI/LXRT modules to demonstrate the use of AIC and the real- time performance. Currently, an integration of the proposed architecture with the OROCOS project is under development.