Implementation of velocity estimation method in DC motor for micro-friction characterization

• Main Author: Chua, Jian Pei
• Other Authors: Tegoeh Tjahjowidodo
• Format: Final Year Project
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering::Mechanical engineering::Mechanics and dynamics
• Online Access: http://hdl.handle.net/10356/63667
• Institution: Nanyang Technological University

Stick-slip phenomenon can be described as two surfaces stick and slip between each other and it results in a change in frictional force. This phenomenon occurs at certain velocity and the specific velocity depends on the type of materials that being used in the experiment. In order for the DC motor to achieve the velocity where the stick-slip phenomenon occurs, a precise position and velocity control must be realized. Generally, a good velocity control can be achieved by using tachometer but considering the fact that its cost and adaptability on DC motor, velocity estimation by using encoder is preferred. This report discussed how the random signals can be tuned effectively using PID tuning, how to apply a suitable filter on the unprocessed data from the DC motor, and lastly discussed about the methods to achieve velocity estimation and their effectiveness. MATLAB/Simulink software was used to establish a system controller that controls the motor, and the performance of the motor was monitored and recorded by the application of dSPACE ControlDesk software. The motor in the experiment has an encoder of 2500 line counts and a tachometer that was used as reference to compare the effectiveness of each velocity estimation method. The chosen type of filter was FILTFILT because of its zero phasing property and the cut-off frequency and order number of FILTFILT filter were chosen to be 3 Hz and 4 respectively. The velocity estimation methods in this report were direct differentiation and Euler approximation with backward steps. The results of these methods using different random signals were discussed. The effective velocity estimation method will allow the user to perform accurate velocity control thus the velocity at the point where stick-slip phenomenon occurs can be determined. Lastly, a trial experiment was done to determine the hysteresis of a sine wave by tuning the value of inertia. This experiment was insightful as it will provide useful information for future study in stick-slip phenomenon.