Dynamic Modeling and Anti-Disturbing Control of an Electromagnetic MEMS Torsional Micromirror Considering External Vibrations in Vehicular LiDAR

Hua, Yimin; Wang, Shuangyuan; Li, Bingchu; Guo-zhen, Bai; Zhang, Pengju

doi:10.3390/mi12010069

Cited by 16 publications

(8 citation statements)

References 23 publications

(22 reference statements)

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“…In this paper, the concept of cascaded torsional beams is adapted to the FPCB micromirror frame to help increase the scanning angle or increase the primary resonant frequency (and then the robustness) without lowering the scanning angle. Building upon the The robustness of such a micromirror against external vibration is determined by the first mode of the resonant frequency of the micromirror [17,18]. The challenge associated with that mirror is that in order to increase the resonant frequency, the torsional stiffness should be increased.…”

Section: 𝐹𝑜𝑀 = 𝜃 𝑓 𝑑mentioning

confidence: 99%

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Cascaded 2D Micromirror with Application to LiDAR

Ghazinouri,

2023

Micromachines

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This paper introduced a novel approach to enhance the vertical scanning angle of a large aperture 2D electromagnetic micromirror through the utilization of a cascaded torsional beam design. The primary objective was to increase the vertical scanning angle without compromising the robustness, which was achieved by optimizing the trade-off between the rotation angle and the first mode of resonant frequency. The cascaded design provides flexibility to either increase the outer frame’s rotation angle without sacrificing torsional stiffness or enhance the torsion beam’s stiffness while maintaining the same rotation angle, thus elevating the first-mode resonant frequency and overall robustness. The effectiveness of the cascaded design was demonstrated through a comparative study with a non-cascaded 2D micromirror possessing the same aperture size, torque, and mass moment of inertia. Theoretical analysis and finite-element simulation are employed to determine critical parameters such as the stiffness ratio between the cascaded torsion beams, and to predict improvements in the scanning angle and primary resonant frequency brought by the cascaded design. Prototypes of both cascaded and non-cascaded designs are fabricated using a flexible printed circuit board combined with Computer numerical control (CNC) machining of a Ti-alloy thin film, confirming the superior performance of the cascaded 2D micromirror. The cascaded design achieved vertical scanning angles up to 26% higher than the traditional design when both were actuated at close resonance frequencies. Additionally, the micromirror was successfully integrated into a 3D LiDAR system. The light detection and ranging (LiDAR) system was modelled in Zemax OpticStudio to find the optimized design and assembly positions.

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Section: 𝐹𝑜𝑀 = 𝜃 𝑓 𝑑mentioning

confidence: 99%

“…The robustness of such a micromirror against external vibration is determined by the first mode of the resonant frequency of the micromirror [17,18]. The challenge associated with that mirror is that in order to increase the resonant frequency, the torsional stiffness should be increased.…”

Section: Introductionmentioning

confidence: 99%

Cascaded 2D Micromirror with Application to LiDAR

Ghazinouri,

2023

Micromachines

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“…In other words, the packaging area must be 1.41 times the device's size and the external magnet's size. As a result, it is challenging to reduce the packaging area [16]. In addition, driving multiturn coils must be placed on a gimbal with 2 degrees-of-freedom connected only by narrow beams in the conventional electromagnetic MEMS scanner.…”

Section: Introductionmentioning

confidence: 99%

Two-Axis Electromagnetic Scanner Using an Asymmetric Frame on a One-Axis Lateral Magnetic Field

Okamoto,

Nakashima,

Oda

et al. 2024

J. Microelectromech. Syst.

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Conventional electromagnetic microelectromechanical system scanners require a biaxial (two-axis) external magnetic field to obtain a biaxial torque, which increases the number of bulky external permanent magnets and the packaging size caused by 45 • -orientated placement of permanent magnets. Thus, this study developed a two-axis resonant electromagnetic scanner with an asymmetric gimbal frame that generates two-axis torque via a one-axis lateral external magnetic field. As external permanent magnets can be placed parallel to the device die, the proposed method reduced the packaging size. Two driving forces were generated by two independent electromagnetic actuators placed on both sides of the asymmetric gimbal frame, which converted the unidirectional forces into two-axis torque. As the two driving actuators were independent of the connecting beams, gimbal frame, and mirror and were connected to the thick outer Si handle frame, the temperature increase of torsion beams and the asymmetric gimbal frame, which affects the resonant performance, were reduced. Additionally, as the current paths were not multiturn coil shapes, the paths can be formed with a via-less single metal layer. Also, the drive circuit can be simplified since drive signals for two-axis rotation can be applied to individual actuators. We demonstrated biaxial scanning using the proposed structure with a 4-mm mirror. The optical scanning angle was 4.84 • for the 1.308 kHz X-axis scan and 16.1 • for the 2.568 kHz Y-axis scan when a current of 300 mA was applied independently to the X-and Y-axes driving actuators. We obtained the large displacement at the resonant frequency using the asymmetric gimbal frame under a lateral magnetic field.[

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“…None of them analyzed the effects of vibrations on the resulting point cloud and most of them focused on mitigating the vibration effects of lidar subcomponents. Two studies [3] and [4] investigated the effects on Micro-Electro-Mechanical Systems (MEMS) based lidars. Both studies used shakers to apply vibrations to the micro-mirrors.…”

Section: Introductionmentioning

confidence: 99%

Automotive Lidar and Vibration: Resonance, Inertial Measurement Unit, and Effects on the Point Cloud

Schlager

Goelles

Behmer

et al. 2022

IEEE Open J. Intell. Transp. Syst.

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Lidar is an important component of the perception suite for automated systems. The effects of vibration on lidar point clouds are mostly unknown, despite the lidar's wide adaption and usual application under conditions where vibration occurs frequently. In this study, we performed controlled vibration tests from 6 to 2000 Hz at 9 and 12 m/s 2 in vertical direction on the automotive lidar OS1-64 by Ouster. An information loss emerged which is mostly independent from frequency and acceleration. The loss of points is randomly distributed and does not correlate with range, intensity, or ring number (the horizontal line of the rotating lidar unit). The resonance frequency of 1426 Hz proved to be unproblematic as no pronounced negative effects on the point cloud could be identified. For vibration detection, the internal Inertial Measurement Unit (IMU) of the OS1-64 is accurate and sufficient for vibrations up to 50 Hz. Above 50 Hz, external IMUs would be required for vibration detection. Counting the number of points on a target close to the edges was investigated as an exemplary way to detect vibration purely based on the point cloud, i.e., independent of the lidar's IMU.

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Dynamic Modeling and Anti-Disturbing Control of an Electromagnetic MEMS Torsional Micromirror Considering External Vibrations in Vehicular LiDAR

Cited by 16 publications

References 23 publications

Cascaded 2D Micromirror with Application to LiDAR

Cascaded 2D Micromirror with Application to LiDAR

Two-Axis Electromagnetic Scanner Using an Asymmetric Frame on a One-Axis Lateral Magnetic Field

Automotive Lidar and Vibration: Resonance, Inertial Measurement Unit, and Effects on the Point Cloud

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