<title>Design And Software Aspects For The Control System Of The 30 m MRT</title>

Abstract

The 30 m Millimeter Radiotelescope (MRT) will have a beamwidth of less than 10" when operated at a wavelength of 1.2 mm. It is an open air telescope located on a mountain ridge in southern Spain. 4here the instrument is exposed to severe environmental influences, especially wind and temperature changes. The pointing and tracking accuracy required is of the order of a few seconds of arc. Simulations have shown that these specifications cannot be met with conventional servo design. An improvement of performance can be obtained applying the modern concept of state control. The state controller needs the acquisition of data about position and velocity at several points of the instrument in real time.Additionally the state controller requires repetition rates of a few milliseconds, in which the data have to be read, converted and the servo algorithms calculated. This is performed by microprocessors operating in CAMAC crates close to the driving system. The whole system is controlled by two identical computers. One usually controls the antenna and data acquisition from the receivers, the other can be used for data analysis or as a backup controller. All receivers are connected via CAMAC, too.Special software tools have been developed for the use of this system. They allow an easy access to the variety of different process control items needed to drive the complete system. They have proved to be a powerful aid in developing the process control hardware and in the installation phase. They will be used for the communication between the operators and the system.In the development of the system the possibility of expanding the system to remote observing has been kept open. State controllerThe 30 m millimeter radio telescope (MRT) requires a pointing accuracy of a few arcseconds. Extended investigations of Juen and Zeitzl have shown that the required accuracy can only be obtained with a state controller, but not with a conventional cascade controller. Fig. 1 shows the principal structure of the state controller. It consists of a proportional feedback of position and velocity (state variables) of -antenna axis (elevation and azimuth), -motor (elevation and azimuth), -counterweight -box (azimuth), -vertical movement of the elevation bearing.The stationary position accuracy is reached by use of an integral feedback of the position error. The gains of the controller are computed by a minimizing procedure. The quantity to be minimized is the time integral over a weighted sum of the set point error and the motor torque. For this procedure a sufficiently accurate mathematical model of the telescope is essential. The weighting factors in the procedure are the design parameters of the state controller.For a satisfactory performance of the control high gains are required. High gains are obtained by choosing the weighting factor for the motor torque sufficiently small. Practical limitations for the magnitudes of the gains are:-non -linearities like friction and backlash, -time -delays in the motors, -time -delays and noise in the measu...

Trends in Architecture and Middleware of Radio Telescope Control System

“…Owing to the relatively single scientific requirements, fewer hardware devices of radio telescope, simple device functions, and less business logic function between subsystems, the control system was built with a centralized architecture to satisfy the requirements of radio telescope. e centralized architecture was mainly applied in early radio telescopes, such as the 30 m Millimeter Radio telescope control system [1], Effelsberg control system [23], Nobeyama Radio Observatory 45 m (NRO45M) telescope control system [24], and Parkes control system [25]. is type of control system centrally processed all the business logic of antenna, receiver, and other subsystems.…”

“…Meanwhile, the progress of astronomy has put forward higher requirements for radio telescope. In the early days, radio telescopes have a simple equipment structure, a single business logic functionality of software [1,2]. However, with the increase of scientific needs, the continuous breakthroughs in key technologies of radio telescope, the degree of automation, and the requirements of antenna accuracy are also continuously improved.…”