DEVELOPMENT OF MAGNETORHEOLOGICAL ELASTOMER LINEAR ACTUATOR

Abstract

Nowadays, the piezoelectric actuator is commonly used in micro-scale precision systems. However, the use of piezoelectric material is limited to a certain degree of motions because this material has a high tendency to fracture when prolonging exposure to vibrant environments. In contrast, magnetorheological elastomers (MRE) material has high elasticity properties which could capable to withstand this environment. Thus, this project aimed to use MRE in the development of the linear actuator system and observed its displacement responses. The MRE specimens were fabricated using silicon rubber and magnetic particle with the composition of 70/30, 60/40, 50/50, 40/60, and 30/70 percent by its weight percentage (wt%) using compression moulding technique. The surface morphologies were performed to observe the distribution of the particles. Then, the vision-based measurement system was developed in order to perform a displacement test on the MRE specimens. Besides that, the system is also acting as displacement feedback for MRE linear actuator closed-loop control system. System identification approach was adapted to estimate an MRE linear actuator plant model and then used to tune a proportional integral derivative (PID), controller. Prior testing, a sample of the linear actuator was designed and simulated using SOLIDWORKS 2016 x64 Edition and Finite Element Magnetic Method (FEMM) 4.2, respectively in order to observe the magnetic field. It is observed that magnetic particles distributed on the specimen surface similar to the isotropic types. Besides, the vision-based positioning system developed was reported having an accuracy of up to 0.0025 μm. Furthermore, the highest displacement span was 84 μm, which obtained from composition 50/50 silicon rubber: magnetic particles by its wt%. The experimental result shows that the PID controller successfully reduces a steady-state error (7 μm) and settling time (12s) for MRE linear actuator. According to the finite element analysis, the maximum magnetic density observed at plunger with the value of 1.8 tesla. MRE plant model was successfully developed by 85% fitted to real experimental data. Besides, the PID values for Kp, Ki, and Kd were tuned to 5.26, 5.25 and 0, respectively. As a conclusion, the MRE using silicon rubber and magnetic particle were successfully developed and 50/50 by wt% composition had optimum displacement response. Furthermore, the displacement response for MRE based actuator design used in this research was comparable to the existing linear actuator. The vision-based positioning system developed also can be used as measurement and control the displacement in the actuator application.