6-DoF miniature maglev positioning stage for application in haptic micro-manipulation

This paper presents a micro-positioning stage in six orthogonal directions (6-axis) based on magnetic levitation. The stage is intended to be used in a haptic tele-operated control scheme, as the positioning system of a slave robot for micro-manipulation. This application offers a particular set of requirements which are discussed in Section 1.A novel 2-axis actuator assembly is introduced, in which two fixed coils generate Lorentz forces on a single moving magnet, which is attached to the mover. Three such actuators generate the six forces that are required in the stage. The position of the mover is then sensed by using LED/photo-transistor pairs. The actuator assembly is studied in detail and characterized, both experimentally and through simulations. Non-linearity and position dependency in the transfer functions of the sensor and actuator are identified, characterized and integrated into a dynamic simulation of the system. A Monte Carlo study is then used to investigate the robustness of the complete system to manufacturing tolerances and the intensity of different noise sources.The stage is fabricated, including custom PCB’s for signal conditioning and amplification. With a movement range of 200 × 200 × 200 μm and rotations of 18–42 mrad, the achieved MIM (minimum incremental motion) is 50 nm and 3.5–7 μrad under closed loop control.

► A 6-axis micro-positioning stage based on magnetic levitation is presented.
► A 2-axis actuator is introduced, composed of two fixed coils and one moving magnet.
► A movement range of 200 μm translations and 18–42 mrad rotations is achieved.
► Position noise remains below 40 nm and 3.5–7 μrad under closed loop control.
► The stage is particularly useful for application to haptic micro-manipulation.