The Large Adaptive Reflector is the Canadian concept for a new type of large-scale radio telescope. This new telescope is composed of a reflector made of individually actuated panels and a multi-tethered feed platform held aloft by an aerostat. The present thesis focuses on the position and orientation control of the feed platform. In the first part of the thesis, a model of both the cable and the feed platform are derived. Then, a control fully adapted to the particular system's dynamics is designed. This control strategy is based on the cascade control technique. The inner control loop adjusts the tension in each cable. The inner loop controller is synthesized using Hinfinity optimal control technique. In addition, gain scheduling is used to adapt the Hinfinity optimal controller to the cable properties. The outer control loop corrects the pose of the feed platform. To do this, control techniques such as Inverse Dynamics Control, PID controller and Hinfinity robustness analysis are used. Then, the model derived previously is connected to the multi-loop controller. Simulation is run and the control strategy performance level is calculated from simulation results.