This paper presents a three-dimensional (3-D) digital electromagnetic actuator able to reach 12 discrete positions distributed in a 3-D space. The mobile part of this actuator includes a cuboid permanent magnet fixed in a hexagonal casing. The mobile part is able to reach six discrete positions in xy -plane at level z $_1$ and the remaining six discrete positions at level z $_2$ . The switching of the mobile part in xy -plane is achieved by injecting currents in the fixed planar wires situated beneath it. The actuator design integrates a coil to switch the mobile part between two predefined levels in z -axis. To maintain the mobile part at a discrete position without energy consumption, six fixed cylindrical permanent magnets are placed around the mobile part. To design the actuator, a model has been developed and is presented in this paper. Rapid prototyping approach (laser cutting) is used to fabricate the actuator prototype. The maximum and the minimum strokes in xy -plane are between 0.5 to 1.0 mm while along z -axis the actuator is able to perform a stroke of 1.0 mm. Experiments have been conducted on the prototype to validate the proposed design and the 3-D actuation. The performance characterization has been conduced and the experimental and the simulated results have been compared.

A Novel Three-Dimensional Electromagnetic Digital Actuator With 12 Discrete Positions

The electromagnetic positioning technology is a good method to obtain the position and attitude of magnetic micro-robots, which has high positioning accuracy and is easy to realize. Analytic solutions of position information can be obtained by using magnetic dipole model directly, but the positioning error is large in the magnetic interference environment. The model established in this paper takes into account the error caused by noise interference, and the simulation results show that compared with the direct positioning algorithm without denoising, the accuracy is greatly improved, the positioning error is less than 1 mm, and the attitude error is less than 1 degrees.

Anti-Noise Electromagnetic Positioning Algorithm Based on Magnetic Dipole Model

In this paper, a novel micro-positioning device based on a 3D digital actuator is presented. The proposed system allows realizing planar motions of micro-objects, which could be implemented in several applications where micro-positioning tasks are needed such as micro-component manufacturing/assembly, biomedicine, scanning microscopy, etc. The device has three degrees of freedom, and it is able to achieve planar motions of a mobile plate in the xy-plane at two different levels along the z-axis. It consists of a hexagonal mobile part composed of a permanent magnet that can reach twelve discrete positions distributed between two z-axis levels (six at each level). Two different approaches are presented to perform positioning tasks of the plate using the digital actuator: the stick-slip and the lift-mode approaches. A comparison between these two approaches is provided on the basis of the plate displacement with respect to different current values and conveyed mass. It was observed that for a current of 2 A, the actuator is able to displace a mass of 1.15 g over a distance of 0.08 mm. The optimal positioning range of the planar device was found to be ±5.40 mm and ±7.05 mm along the x- and y-axis, respectively.

Planar Micro-Positioning Device Based on a 3D Digital Electromagnetic Actuator

In multi-axis motion control, cross-axis couplings cause error force and position disturbances in an axis when a desired motion is generated along another axis. Different from the parasitic errors that result from the imperfections of the mechanical bearings and reference surfaces, cross-axis perturbations are caused by errors that occur both statically (geometrical errors) and dynamically (in the transient responses) and are more prevalent in air-bearing and magnetic-levitation (maglev) stages. The parasitic errors are heavily dependent on the sizes of the stage's mechanical components, while the cross-axis perturbations depend significantly on the mover's speed and acceleration. For stages using permanent magnets (PMs) and Lorentz coils, the causes of off-axis forces include 1) errors in the coil turns' straightness, perpendicularity, and parallelism of the motor axes, and 2) errors in the local magnetizations and PMs' fringing effects. The purpose of this paper is to analyze the topologies of 6-degree-of-freedom (6-DOF) single-moving-part stages to minimize cross-axis couplings. The outcome is a stage configuration with reduced couplings and cross-axis perturbations. This is supported by experimental results performed on a newly developed 6-DOF maglev laser-interferometer stage. Its achieved root-mean-square (rms) positioning noise and minimum step size in XY are 3 nm and 10 nm, respectively. Its achieved resolution in out-of-plane rotations is 0.1 μrad. In addition to the analysis supported by these results, this paper introduces a new measure to represent cross-axis perturbations and to compare the effects of couplings in multi-axis positioning. This measure is entitled the cross-coupling quantity (CCQ) and calculated from the displacement of the stage in the axis of interest, the peak time of the response, and the peak-to-peak (p-p) error in the perturbed axis.

Error analysis to minimize cross-axis couplings in 6-DOF motion systems with a single moving part

This paper presents a micro-fabricated digital electromagnetic actuator able to realize 3D displacements. The actuator consists of a mobile part, placed inside a silicon hexagonal cavity. The mobile part of an actuator can reach up to twelve discrete positions distributed between two different levels along z-axis(six positions at each level). The switching in xy-plane between the six positions is achieved using planar conductors placed beneath the cavity whereas, switching between the levels along z-axis is obtained with the help of an electromagnetic air-core coil. The cavity is surrounded with six cylindrical permanent magnets, in order to obtain magnetic holding. A semi-analytical model has been realized to design the prototype. Deep reactive Ion Etching(DRIE) process has been undertaken in order to obtain a microfabricated prototype. Experiments have been conducted to verify the ability of the actuator to reach twelve positions and to characterize the displacement stroke along x-, y- and z-axis.

A Micro-fabricated Hexagonal Digital Electromagnetic Actuator

This paper presents a planar digital actuator based on hexagonal design. The actuator is comprised of a Mobile Permanent Magnet (MPM) surrounded by six Fixed Permanent Magnets (FPMs). The originality of the proposed actuator lies in its ability to reach six discrete positions in xy-plane with different stroke sizes (along x-axis: 0.50 mm and 1.00 mm; along y-axis: 0.86 mm). An analytical model has been developed to compute the electromagnetic and magnetic forces exerted on the MPM. Using this model, the design parameters of the actuator have been selected. A prototype has then been realized using the rapid prototyping manufacturing techniques. Through experiments, the motion behavior of the actuator has been verified. The driving current impact on the MPM displacement has been observed. For an MPM switch between two discrete positions, the obtained 10% settling time is between 10 and 20 ms.

Development of a six positions digital electromagnetic actuator

An actuator array dedicated to the collaborative actuation is presented in this paper. The array consists of several elementary digital actuators to carry out planar conveyance tasks. Each elementary actuator of this array is based on an electromagnetic principle and has an ability to achieve six discrete positions in a 2D plane. A semi-analytical model has been developed to compute the electromagnetic and magnetic forces, which helps to design an actuator prototype. The homogenous behaviour of all elementary actuators of the array has particularly been studied using the model. An array prototype has then been realized using laser cutting and rapid prototyping technique. This prototype is based on a honeycomb architecture and composed of seven elementary actuators. Experiments has been conducted to characterize the actuator array performances. The pulse duration needed to switch the actuators and the energy consumption has been calculated. Finally, the principle of conveyance using the array is detailed and the collaborative actuation have been experimentally tested and shown.

Ajinkya Deshmukh

Papers

Development of a six positions digital electromagnetic actuator

A Novel Three-Dimensional Electromagnetic Digital Actuator With 12 Discrete Positions

Planar Micro-Positioning Device Based on a 3D Digital Electromagnetic Actuator

A Micro-fabricated Hexagonal Digital Electromagnetic Actuator

Hexagonal Digital Actuator array for Micro Conveyance Application