Position Control of a Rail Guided Mover Using a Low-Cost BLDC Motor

This paper presents the design and control of a rail guided mover system using a brushless dc (BLDC) motor as traction. In the designed system, the roller on the rail surface is driven by the BLDC motor, and the high-definition camera moves up and down driven by a dc motor. In order to keep the reference position in the low-speed region around the stop position, a modified microstepping method using torque angle is proposed. The proposed microstepping method uses the variable current magnitude according to the estimated torque angle in order to reduce the torque ripple. Then, the actual rotor follows the rotating current vector with the proper torque angle band. Moreover, a smooth deceleration is achieved by a variable gain of the position controller, which is obtained by the deceleration time and position error. Furthermore, the slip effect between the roller and the rail surface is simply compensated by the measured slip coefficient in both forward and backward directions. The proposed position control method is verified by the experiments of the practical rail moving security system.