Force Analysis in Design of High Power Linear Permanent Magnet Actuator with Gas Springs in Drilling Applications

This paper mainly describes the force analysis in the design optimization of a reciprocating linear permanent magnet actuator with interior magnet and slotless stator. This paper predicts the force characteristics according to design parameters such as pole pitch, magnet width and stator inner diameter on the basis of numerical calculations. The design is unique because of the combination of a heavy piston and gas springs. The gas springs allow the piston to oscillate at high frequency and with a long stroke length, in spite of pistons large weight. A large electromagnetic force, due to the use of permanent magnets makes a high power linear electric actuator available. The heavy piston causes a considerable vibration in the housing which is utilized in the drilling application. The load can then be attached directly to the housing and the machine can be made hermitically sealed, which eliminate leakage problems. These features make the actuator suitable as a hammer in oil drilling applications.