Modeling And Controlling Of The Mount Drive Of Slant Axis Telescope

Slant mount telescope (SMT) become a forefront issue of frame structure research of astronomical telescope. Compared with traditional horizontal astronomical telescope, this new structure can overcome vibration problem when passing the midheaven and be driven more smoothly in vertical direction. However, using 45-degree slant mount instead of pitch axis also bring some new problems. Slant mount rotates on tangent plane results in vertical shift which induces kinematic coupling (KC)of two axes, rotation of tracking system images and vertical unbalance. These problems result in dauting challenges in control. Related control system researched of SMT around the world are still in the exploratory stage. It is necessary to study on these problems and to give a feasible control scheme.At first, we study on the kinetic characteristic of SMT, mainly about coupling relation between motion of the two axis. We set up a precise mathematic model of the moving trail of SMT according to mechanical drive theory and parameter equation of 3D circle. And then integral and local characteristics of moving trait is also analyzed by kinematic simulation which lays the theoretical foundation for following researches about KC, rotation of images (RI) and anti-interference control algorithm. Secondly,we design two decoupling schemes according to the mathematic model mentioned above and transformation relations between different axes, they are Feed-forward Compensation Decoupling Algorithm (FCDA) and Parameter Conversion Decoupling Algorithm (PCDA). The simulation results show that both decoupling algorithms can solve the problem of coupling movement effectively, but in terms of stability, FCDA is superior to PCDA. For RI problem, we calculate the position of target centroid by celestial sphere mapping and space coordinates transformation, and then isolate accurate independent reference quantities of two axes through decoupling algorithm.This algorithm is also tested by simulations. As to interference problem of slant mount,we design PID bi-loop internal model control algorithm to simplify the controller's parameters and to improve the performance of anti-jamming.Finally, based on previous researches and a prototype of SMT, hardware and software module of the control system is designed and tested. The results show that average locating errors of horizontal and vertical are 5.4960' and 4.8540', and average tracking errors of azimuth axis and slant axis are 5.8877' and 6.3821'. In conclusion,these algorithms are feasible and this research may provide technical support for future drive system study of SMT in China.