Design and implementation of a real-time wireless sensor/actuator communication system

For industrial automation applications using production machines and robotic installations, truly wireless systems offer advantages in terms of cost and flexibility. Requirements on power supply and real time communication for such applications are highly demanding, and cannot be satisfied with today´s off-the-shelf systems. A novel factory communication system, called WISA (wireless interface for sensors and actuators), has thus been developed which provides both wireless communication and wireless power supply. The power supply is based on magnetic coupling while real time wireless communication uses a new TDMA protocol combined with frequency hopping. The TDMA protocol uses optimized parameters for reliable and low delay transmission for a high number of active nodes. The frequency hopping sequences are optimized to mitigate effects of multi-path propagation, interference from other systems operating in the 2.4 GHz ISM band, and self-interference. The new design re-uses existing RF transceivers. The paper explains design concepts of the WISA communication system, and describes practical experience gained with its deployment in industrial environments