2-DoF magnetic actuator for a 6-DoF stage with long-stroke gravity compensation

High-precision positioning systems, such as lithography wafer scanners, vibration isolators and gravity compensation systems require multi-DoF stages. These stages generally apply magnetic actuators because of their contactless operation and high-force capacity. The working range of current magnetic actuators in the levitating direction is limited to around 1mm [1]. However, in some applications such as wafer loading in nanoimprint lithography, a long-stroke motion is required. Although increasing the airgap width would increase the working range, it would also require a larger driving current and, thus, more heat dissipation, which is undesirable for high-precision systems. To alleviate this problem, the design of a novel 2-DoF magnetic actuator is presented in this paper. The actuator, presented in Section 1, is capable of both long-stroke (20mm) and short-stroke (2mm) motions in two perpendicular axes. In the long-stroke direction the actuator can achieve high-precision positioning with low power and a tuneable constant force, which is confirmed both by simulation and experiments. In the short-stroke direction, it works as a conventional reluctance actuator. Moreover, as shown in Section 2, the actuator could also be used to design 6-DoF maglev positioning stages with gravity compensation (see Figure 1).