Proceedings of the 2008 International Conference on Electrical Machines Paper ID 1299 978-1-4244-1736-0/08/$25.00 ©2008 IEEE 1 Demonstration Model of a Linear Permanent Magnet Actuator with Gas Springs Ravindra Babu Ummaneni 1 , Robert Nilssen 1 and Brennvall.J.E. 2 1 Department of Electrical Power Engineering, Norwegian University of Science and Technology 2 Resonator AS Trondheim, Norway E-mail: Ravindra.B.Ummaneni@elkraft.ntnu.no Abstract- This paper describes the design and modeling of demonstration model of a linear permanent magnet actuator. This demonstration model used to verify the idea of using gas springs with linear permanent magnet actuator to produce strong vibrations for drilling applications I. INTRODUCTION Linear permanent magnet machines with oscillatory motion have been widely proposed to operate as alternators and oscillatory motors often called as linear permanent magnet actuators. These devices would be advantageous in many applications like compressors, pumps, electro magnetic valve actuators, vibrators etc. In addition oscillatory motion of the linear actuator can be effectively utilized in more demanding drilling applications [1]. The power level required for drilling applications is higher than normal. With the conventional mechanical spring concept on both sides of the heavy mover will not produce sufficient fast oscillations. The mechanical springs are not well suited to oscillate heavy masses at higher frequencies due to mechanical constraints. The concept of gas springs with linear machine can oscillate heavy mover mass at higher frequency to produce strong vibrations for drilling applications. The concept of integrating linear machine with gas springs is shown in Fig.1.this paper mainly describes the design and dynamic modelling of proposed demonstration model. Fig.1 Linear Actuator II. ACTUATOR DESCRIPTION The actuator shown in a cross section in Fig. 1 has a tubular shape. The stator part consists of peek material, provide smooth bearing surface to mover and completely eliminates the iron losses. The mover part consists of interior permanent magnet having steel parts on each side. Due to the alignment problem, iron parts are replaced by steel parts on both sides of piston with the cost of reduced flux density. This proposed machine is completely air cored, not good in performance but it proves the concept very well. Fig.2. linear actuator (a) crosses sectional view. (b) Built prototype The entire machine on both sides is sealed with two end caps to create the gas spring effect on both sides of the piston. To keep the piston in centre position against the gravitational force, two simple mechanical springs are attached on both sides of mover as shown in Fig. 2b.By applying the proper current control depends on mover position, the piston will oscillate between the gas springs in resonance. In result of oscillating piston inside the machine the total casing also starts vibrating .these vibrations are effectively utilized in drilling applications. The piston and casing (stator) are moving in opposite directions. The main dimensions of the demonstration model are: 1) length of machine: 80mm; 2) permanent magnet diameter: 15mm Gas springs Outer casing Linear machine Piston rod, mover Peek Magnet Coils Gas springs N S End Cap steel