Dual-Axial Motion Control of a Magnetic Levitation System Using Hall-Effect Sensors

Abstract

This paper presents a new methodology to determine the position of a magnetically guided robot (MGR) in horizontal planes using magnetic flux sensors. This position determination methodology can be used independently as well as in collaboration with optical sensors in the case of the optical blockage. A combination of linear Hall-effect sensors (two sensors for each axis of motion) was employed to measure the magnetic flux in the MGR's working space. A configuration of several electromagnets was used as a source of magnetic field, and an analytical model of the system is developed. The MGR's position was determined based on the polynomial relation between the Hall-effect sensors' output and the location of the minimum magnetic potential energy point in horizontal planes. Using the cross-validation method, it was found that a fourth-order polynomial model could accurately predict the MGR's position. Experiments were conducted on a horizontal plane to validate the performance of position estimation using the magnetic flux sensing method. The accuracy of the position determination method was 0.4-mm root-mean-square errors in both the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> - and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> -direction over 8 × 8 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> working area. This paper also experimentally validates a combined optical-magnetic position determination technique for the motion control of a magnetically guided robot in optical blockage conditions as unknown environment that can be used as a promising replacement of X-ray and ultrasound techniques.