Abstract
The magnetically levitated rotary table (MLRT) has the potential to be applied in many industrial applications due to its excellent rotation ability and good positioning accuracy. This paper presents the prototype of a novel MLRT with a simple and compact structure. The table employs a circular permanent magnet (PM) array and a circular coil array to generate large scale rotation around the vertical axis and limited movement in the other directions. This MLRT has a higher current carrying capacity and simpler commutation law than the existing MLRT. Furthermore, different from the previous works, the magnetic force model presented in this paper is obtained by a novel analytical-numerical method that considers the clearances in the circular PM array. Thus, the predicted magnetic force and torque are more accurate than those from the existing modeling method. The translation and rotation of the table are measured by six laser sensors, which are distributed around and below the mover respectively. The PID controller is used to stabilize the system. Experiments related to the motion decoupling, trajectory tracking and load change are carried out to verify the motion performance of the novel rotary table. Compared with the existing magnetic force model, the experimental results illustrate that the novel magnetic force model, which considers the clearances in a circular PM array, is more suitable for motion control of the MLRT.
Highlights
A precise rotary table is a promising equipment to be applied in many areas, such as mechanical micromachining [1], [2], target tracking devices [3] and radar antenna servo turntables [4], due to its strong rotation ability and high positioning resolution
Each actuator which consists of an ironless coil and one or two permanent magnets can produce magnetic force in one direction
MECHANICAL DESIGN As shown in Fig. 1, the proposed magnetically levitated rotary table (MLRT) is mainly composed of an optical vibration isolation platform, a base, sensors, coil windings, permanent magnets, a platen and a square object
Summary
A precise rotary table is a promising equipment to be applied in many areas, such as mechanical micromachining [1], [2], target tracking devices [3] and radar antenna servo turntables [4], due to its strong rotation ability and high positioning resolution. Vibration and the hazards of high pressure gases are eliminated, the magnetically levitated rotary table (MLRT) has better dynamic performance and higher reliability than a traditional turntable that uses mechanical. When all actuators work together, the tables can realize the precise positioning motion with multiple degrees of freedom. These tables have compact and simple structures and can be applied in various applications such as scanning probe microscope and coordinate measuring. Their range of motion is small and obtaining an accurate magnetic force model in a large range of motion is difficult.
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