Self-stabilizing platform : How to compensate for imbalance with feedback from an IMU

Sammanfattning: To be able to measure and compensate for imbalance is essential for stabilizing mechanisms. The technique is applied in everything from self-stabilizing cameras to helicopters and noise reducing equipment. This report describes the development of a self-stabilizing platform, and includes theory about sensors, filters and motor modelling, and also practical tests. The purpose is to answer how the system will behave when a load is placed asymmetrically on the platform and if it is possible to compensate for the imbalance that occurs. The tilt of the platform is measured by an IMU, a sensor combining accelerometers and gyroscopes. A Kalman filter is used to combine the data. From this a signal, with noise levels within the requirements, was obtained. A theoretical model was set up for the system. The system was modelled based on a loadof 125g placed in the center of the platform. Two DC-motors compensate for the tilt around each axis. The motors are seen as separate sub systems and are controlled independently. The system is controlled by two PID-controllers which were designed based on the requirements that were set up regarding speed and stability. A short rise time and a small overshoot were essential to be able to minimize the torque on the motor shafts. The same requirements were set for each sub system. The chosen PID-parameters acquired a system which at a step input of 11.4° had a rise time of 0.75s, a settling time of 1.35s and an overshoot of 0.8%. The demonstrator that was constructed was put through a number of tests to answer the research questions. By placing the load at different distances from the center, the theoretical model was examined from its sensitivity to deviations. The test showed that a farther distance between the load and the center corresponded to a greater angular fluctuation and a longer settling time.