Design and Analysis of a Self-balanced Video Monitor Steering Mechanism for Space Applications

Onboard a satellite, a Video Monitor Steering Mechanism (VMSM) is used to capture the video of an on-orbit operation. VMSM is steered about a single axis. The key elements of VMSM would be camera, motor, balancing mass and a mounting bracket with feedback system. Cooperative design of balancing mass ensures gravity centre of rotating mass coinciding with rotation axis which helps in static/dynamic balancing of mechanism during launch by reducing the disturbance torque about rotation axis. VMSM is developed as a compact, miniaturised system actuated by a back driving resisting motor. Together with the back-driving torque of the motor and minimal centre of gravity eccentricity, it prevents the rotation of camera during launch and thus avoiding a separate launch restraint system. The system should meet the required fundamental natural frequency in launch configuration. Analysis has been carried out to estimate the initial frequency of the system and to enhance it further to meet the stiffness requirements. Iterative normal mode analysis technique is used to increase the frequency by adding stiffeners at appropriate locations and removing material at non-load paths. Further, margins are estimated for stresses and loads in the components.