Adaptive Nonlinear Control for Linear Induction Motor Based on Q-Axis Current Compensation

The aim of paper is to propose position control of linear induction motor (LIM) taking into account the end effect, external force disturbance and the uncertainties of LIM model by use of an adaptive command-filtered back stepping controller based on q-axis current compensation to improve the dynamic performance and robustness of controlled system. Two simulation cases are carried out to demonstrate the possibility and effectiveness of proposed controller. Introduction LIM is a kind of driving device with excellent performance, which does not need the intermediate transmission device and produce linear motion thrust directly compared with the rotary induction motor [1-3], which has been widely used in industrial machine, transportation, military and other fields. However, the parameters of LIM are time-varying and uncertain 0. So, the exact model of LIM is difficult to obtain, and advanced and effective control scheme need to be studied. In the control method, backstepping is easy to combine with adaptive control technique [1], which can eliminate the influence of parameter variation and external disturbance, so it has been applied in control of LIM so that satisfactory control performance is obtained [1-2]. Furthermore, the essence of adaptive law for motor parameters is to compensate the q-axis controller current so as to achieve the purpose of current tracking. So, in this paper, we design to compensate the q-axis control current directly in the velocity tracking error, which avoids the complex calculation of the adaptive law for each uncertain parameter. The rest of the paper is organized as follows. In section 2, model of LIM considering the end effect is described. In section 3, the design process and stability analysis of proposed control scheme has been presented step by step. In section 4, simulation results are shown to demonstrate the possibility and effectiveness of the designed controller. Finally, some conclusions are discussed in Section 5. Model of LIM Considering End Effect By use of the indirect vector control, the rotor flux linkage is oriented to the d-axis and model follows that 0 qr qr      , dr r    0. So, LIM model of indirect vector control [3-4] is expressed as follows           , 1 , , 1 ( ) , ( ) ( ) ( ) ( ) ( ) ( ) 1 ( ) , ( ) (1) 1 /