Guidance and positioning of a linearly indexed mobile truss complex

Abstract

Three methods of sensing the positions of components of a multi-jointed mobile truss structure and transmitting this information with single bit data to a controller were proposed. A control algorithm utilizing the single bit truss position information and on/off control commands was developed for each position sensing method, creating three different guidance and positioning systems for moving the truss complex through the field. One system used microswitches for sensing the angular misalignment between trusses. Another system used the same microswitches for guidance during rough positioning and introduced a laser reference plane for final truss alignment. Both of these systems sensed perpendicular field alignment with microswitch sensing and a reference cable stretched the length of the field baseline. The third system used the position sensing employed in the second system, and also used a second laser reference plane to establish perpendicular alignment in the field. All three systems used an encoder mounted to a wheel rolling along the field baseline cable for distance measurement. A dynamic model of the mobile truss complex was developed and combined with each proposed discrete control algorithm in a computer simulation. This simulation was used to evaluate each guidance system for accuracy, speed, and the number of control commands needed to index the structure. While the third system proved to be slightly faster and more accurate than the first two, the first system was the simplest and most economically feasible. Position sensing equipment based on this microswitch system was constructed and the software and hardware for a microprocessor based controller was designed and constructed. This controller was laboratory tested for proper response to simulated input of truss position data and was found to perform adequately.