Free space laser communication links for short range control of mobile robots using active pointing and tracking techniques

In certain hazardous environments, the use of umbilical and radio control for tele-operation of mobile robots may be prohibited. Such environments include nuclear power plants where the cluttered structure may cause catching and snagging of the umbilical and where radio frequencies would interfere with the safe operation of the plant. Under these conditions, reliable tele-operation using line of sight (LOS) laser links would be preferable. Current research and development of LOS optical links has tended to concentrate on satellite communication applications, rather than robot vehicle telemetry. Many of the techniques developed for satellite pointing and tracking are well researched and documented, but may not be sufficiently robust for short range tracking of vehicles, where abrupt changes of speed and direction, ambient lighting conditions, and environment are common. For LOS laser communication beams to be effective as tele-operation links, they need to maintain continuous pointing and tracking between the operator´s command post and the mobile robot. The communication pathway would typically comprise of control data sent to the robot for its navigation, and video plus sensory data sent from the robot to the command post as an aid to operation. The work described concerns the implementation of a dual-ended, LOS laser link for control of a small tracked robot for reconnaissance and inspection applications. In addition, it describes how, with the use of an intermediate tracking repeater, the communication pathway can be maintained without direct line of sight between vehicle and operator