Adaptive model predictive tuning of industrial servo drives for motion control applications

Abstract

The linear motion systems are commonly used in precision machine newlinetool applications. The main elements of a linear motion system are the servo newlinedrive, ball screw assembly, and control electronics. The servo controller, along newlinewith the servo drive, is used for the position control of the servo motor. newlineThe servo motor has an in-built encoder which gives feedback about its position newlineand velocity. The performance of linear motion systems depends on the efficient newlinefunction of their control with respect to the machine dynamics. Traditionally, newlinePID controllers are used for the closed-loop control of servo drives for automatic newlinecompensation of various positional errors that occur in linear motion systems. newlineThe PID controller is a simple implementation of feedback from encoders. The newlinePID controller needs to be optimally tuned for better tracking performance and newlinedisturbance rejection capability. newline The position precision in the ball screw assembly is affected by newlinethe temperature, backlash error, feed screw pitch error, and error due to feed newlinescrew torsion or expansion. The positional accuracy is also affected by the newlineencoder measurement errors caused by temperature, vibration, and humidity. newlineProportional Integral Derivative (PID) controllers that are employed in linear newlinemotion systems are normally efficient and easy to implement, but have several newlinedrawbacks. By its design, it is a reactive type, and thus it requires a high level of newlineposition error to achieve effective control results. Also, the tuning process newlineinvolves a high degree of expertise and experience. The tracking performance of newlinea PID controller can be enhanced by integrating fractional order derivative and newlineintegral action in the existing PID controller which is named as Fractional order newlinePID (FO-PID) controller and also upgrading it to an International Society of newlineAutomation (ISA-PID) controller. newline