Finite element analysis of the cogging force in the linear synchronous motor array for the Thirty Meter Telescope

In this paper, a finite element analysis of the cogging force generated by an array of linear synchronous motors (LSM) moving on a curvilinear track is presented. This system is under consideration as the driving system for the two main axes of the proposed Thirty Meter Telescope that will be built in Mauna Kea, Hawaii. The main objective of this work is the quantification of the effects of the curvilinear track of LSM arrays on the cogging force. The finite element analysis is carried out using planar cross sections, and the results found are used to find an approximate solution for the three-dimensional model. The results show that the presence of the curvilinear–configured track increases the cogging force of a single LSM significantly, while the presence of the array of LSMs interacts in limiting the increase in the cogging force. A geometric optimization in regards to the relative positions of the LSMs along the curvilinear tracks is subsequently carried out in order to reduce the total cogging force.

Research highlights
► The cogging force in a curvilinear–configured track with an array of linear motors was studied.
► Such track can increase the cogging force in each motor due to the interaction with adjacent motors.
► Max. increase in the cogging force was 240% for the elevation track compare to that of a single motor.
► Total cogging force was 160% higher when no gap was present between the motors.
► Total cogging force was reduced to 60% when the relative position between the motors was optimized.