The Transformation of the Control System of the YNAO Solar Chromosphere Telescope

In this paper we describe a control system based on Digital Signal Processors (DSP) to control the stepper motors of the right-ascension axis, the declination axis, and the mirror cover of the YNAO (Yunnan Observatory) Solar Chromosphere Telescope. This system can process signals of the manual-control box, encoder, zero-point, positioning limits, and so on to appropriately set the speed and displacement of the telescope. Considering that stability is essential to a solar-telescope servo system we allow this system to control acceleration or deceleration in fast moving the telescope. The use of DSP in the control makes changes of high motor speeds smooth to avoid loss of synchronization of a step motor. The system with DSP brings high-precision control of low-speed motions allowing the telescope to track the sun for a long time with a high accuracy. For convenience the system includes the manual-control mode, so that the pointing and motion of the telescope can be controlled through a computer in both automatic and manual modes. The system uses communications between an STC5204AD MCU and DSP to realize the power-off memory of encoder count values and system states. We present the flowchart of the system and details of the implementation of the servo control. We also compare DSP-based and MCU-based servo systems and show that a DSP-based system is superior in performance.