Abstract Details
| Name: Kumar Affiliation: ARIES Conference ID: ASI2018_964 Title : Demonstration of suitability of observer based velocity estimation in distributed telescope control systems Authors and Co-Authors : T. S. Kumar Abstract Type : Poster Abstract Category : Instrumentation and Techniques Abstract : Modern astronomical telescopes are driven by direct drive brushed or brushless DC motors with high resolution rotary encoders directly mounted on the main axes for achieving accurate velocity feedback control. At very low velocities the encoders suffer from errors due to quantization and temporal discontinuities. We present here observer based velocity estimation technique for feedback control of DC motors at very low speeds. A Luenberger proportional integral (PI) observer is designed to estimate the velocity between the discontinuities and validated along with a PI controller, controlling a precision brushed DC motor, on a hardware-in-the-loop platform. This technique could also be utilized for increasing the accuracies of a lower resolution encoder used in smaller telescopes by combining the observer velocity with the velocity estimated from the encoder to offset the exorbitant cost of higher resolution encoders. In case of large telescopes, distributed control system is normally preferred where the sensors, actuators and controllers are distributed over a realtime network. Thus, for practical implementation on such systems the observer and controller are implemented on separate embedded controllers distributed over a controller area network (CAN). The velocity feedback from the observer is provided to the controller over CAN bus and the controller performance at different speeds are evaluated. |