Design and Implementation of Nominal Characteristic Trajectory Following (NCTF) Controller for Linear Motion Servo System Noor Hisham Jalani Advanced Technology Training Centre (ADTEC) 83000 Batu Pahat, Johor, Malaysia jnhisham@adtecbp.gov.my Abstract The Linear Motion Servo System consists of a cart driven by a DC motor, via a rack and pinion mechanism to ensure consistent and continuous traction. Since many controllers can be implemented in this system in order to control the position, therefore the implementation of a practical controller must be investigated. A practical controller is proposed known as a Nominal Characteristic Trajectory Following (NCTF) to control the position of the cart. This paper presents a position tracking control strategy that meets the position tracking performance. The effectiveness of the proposed NCTF controller is evaluated and compared with Proportional-Velocity (PV) controller through simulation and experiment. Keywords: NCTF, PV, position control, linear motion servo system. 1. Introduction Motion control system is a challenging problem in the area of control systems and very useful to demonstrate concepts in linear control such as the stabilization of unstable systems. Until now, a lot of intelligent approaches about the position control for linear motion servo system have been proposed. A two-degree-of-freedom internal model control method based on fuzzy logic has been presented, which adjusts the parameter of feedback controller on-line for the permanent magnet linear synchronous motor position servo system. The control system structure is simplified and has fast dynamic response, while parameter identification is not demanded [1]. Another researcher has also used fuzzy logic controller for position control. The results gave smaller overshoot, shorter settling time and smaller steady-state error than the PID controller [2]. The position control of a linear induction motor using adaptive fuzzy back-stepping design with integral action is proposed; the controller can track periodic step, sinusoidal and triangular inputs precisely [3]. The NCTF controller has been proposed as a practical controller for point-to-point (PTP) positioning systems [6]. Therefore, the purpose of this project is to evaluate and compare the effectiveness of the NCTF and PV controller through simulation and experiment. 2. NCTF Controller In order to determine the NCT, a simple open-loop experiment has to be conducted. In the experiment, an actuator of an object is driven with stepwise inputs, and displacement and velocity responses of the object are measured. Figure 1 shows the stepwise inputs, and the velocity and displacement responses due to the stepwise inputs. In this study, the rated input to the actuator u r is used as a value of the stepwise inputs.