High-Performance Positioning Control of a Linear Brushless Motor using Identification of the Loading Mass

Recently, a linear motor has become major interest as a direct drive type actuator that can realize linear motion without auxiliary mechanism. A linear DC brushless motor (LDM) is suitable for a high-accuracy servo with small size. In the LDM, the loading mass changes its values in dependence on the operating condition, and the gravity of the loading mass on a slope becomes disturbance for the control system. The damping coefficient of the LDM changes with the contact surface between the linear guide and the mover. It is difficult to keep the condition uniform. Then, parameter variations in the LDM should be considered to be large. In order to overcome above points, an adaptive identification method is applied for estimation of the loading mass, the damping coefficient and disturbance and pole assignment type positioning controller is designed using the identified loading mass. In experimental studies for the LDM, overshootless positioning control is realized in the maximum velocity for different LDMs or loading masses.