Simon Kern

Working space analysis and optimization of the main positioning system of FAST cabin suspension

This paper devotes to the working space analysis of the main positioning system of FAST cabin suspension, a flexible-cable-driven parallel manipulator. The problem formulation is deduced through equilibrium analysis of the cabin platform and suspension cables, which changes subsequently into a nonlinear constrained optimization intending a uniform allocation of the six cable tension force. The analysis verifies the accessibility of focus cabin to the whole focus surface. The optimization investigates the orientation of the focus cabin under equilibrium and the optimal cable forces, as well as elaborates their importance in the finite element modeling of the cable-cabin system and the respective layout designs of the rotator, Stewart stabilizer and capstan motors. In the end, the influences of the tower height and the position of mass center of the focus cabin on the optimization results are discussed.

Mobile inverse pendulum modeling and control

Modeling using Lagrange equation of 1st kind and state-space control of a real inverse pendulum is considered. The mathematical model of the pendulum is derived and compared with measurements of the real system. The negative influence of the dry friction was considered and the oscillation was successfully reduced.

Proposed design concepts of the FAST focus cabin suspension

The National Astronomical Observatories of China (NAOC) plan to build a 500m radio telescope in southern China [1]. The telescope has a fixed but active main reflector, and large sky coverage is achieved by moving the receivers on a focus surface 160m above the main reflector. The paper describes recommended design concepts for the cable system, the drives and the cabin mechanisms, which position and point the receiver platform. The simulation study, which is basis of the presented results, was executed by engineers of the Technical University Darmstadt under a contract of NAOC in cooperation with two visiting engineers of NAOC and lead by the author [2]. The analysis results and end-toend simulations itself are described in more detail in two other contributions to this conference [3], [4].

Rotatorischer MRF-Aktor für einen Türassistenten (Rotary MRF-Actuator for an Automotive Door Assistent)

Aktoren auf Basis magnetorheologischer Fluide zeichnen sich durch eine hochdynamische und weitgehend lineare Verstellung der Schubspannung aus und stellen deshalb eine interessante Alternative zu konventionellen Bremsen, Kupplungen und Dämpfern dar. Im Rahmen dieses Beitrags wird ein rotatorischer MRF-Aktor modellgestützt entworfen, der sich insbesondere für die Bewegungssteuerung von Türen und Klappen in Fahrzeugen eignet. Actuators based on magnetorheological fluids offer a high dynamical and almost linear force generation and represent therefore an interesting alternative for conventional brakes, clutches und dampers. In this paper a model-based design of a rotary MRF-actuator is described. The designed actuator is especially suited for the motion control of automotive doors.

Trajectory control of cable suspended FAST telescope focus cabin

Operation of the Five-Hundred-Meter Aperture Spherical Telescope (FAST) requires accurate positioning and movement of the receiver platform on a spherical workspace with a radius of 160 m. Supported above the 500 m diameter main reflector it has to be positioned with an accuracy of several millimeters. To achieve this, the receiver is located in the receiver cabin that is suspended on six cables. The cables are attached to six towers located on the circumference of the main reflector and can be actuated via six capstans. In this paper a control concept for the cable-system is presented. Using a detailed mathematical model of the system the performance of the control and the sensitivity to wind and other disturbances is evaluated via simulation. The mechanics are modeled via FEM, the capstan-drives as lumped-mass elements including nonlinear effects like friction and backlash. The control scheme presented consists of position control loops for the capstans and numerically optimized PID-controllers for the positioning of the cabin platform.