arXiv subjects

Azadeh Ansari

Publications and source records attributed to Azadeh Ansari.

4 recordsLinked to original sources

arXiv2025

FAVbot: An Autonomous Target Tracking Micro-Robot with Frequency Actuation Control

Robotic autonomy at centimeter scale requires compact and miniaturization-friendly actuation integrated with sensing and neural network processing assembly within a tiny form factor. Applications of such systems have witnessed significant advancements in recent years in fields such as healthcare, manufacturing, and post-disaster rescue. The system design at this scale puts stringent constraints on power consumption for both the sensory front-end and actuation back-end and the weight of the electronic assembly for robust operation. In this paper, we introduce FAVbot, the first autonomous mobile micro-robotic system integrated with a novel actuation mechanism and convolutional neural network (CNN) based computer vision - all integrated within a compact 3-cm form factor. The novel actuation mechanism utilizes mechanical resonance phenomenon to achieve frequency-controlled steering with a single piezoelectric actuator. Experimental results demonstrate the effectiveness of FAVbot's frequency-controlled actuation, which offers a diverse selection of resonance modes with different motion characteristics. The actuation system is complemented with the vision front-end where a camera along with a microcontroller supports object detection for closed-loop control and autonomous target tracking. This enables adaptive navigation in dynamic environments. This work contributes to the evolving landscape of neural network-enabled micro-robotic systems showing the smallest autonomous robot built using controllable multi-directional single-actuator mechanism.

cs.RO↗

arXiv2021

Phonon heat conduction in Al1-xScxN thin films

Aluminum scandium nitride alloy (Al1-xScxN) is regarded as a promising material for high-performance acoustic devices used in wireless communication systems. Phonon scattering and heat conduction processes govern the energy dissipation in acoustic resonators, ultimately determining their performance quality. This work reports, for the first time, on phonon scattering processes and thermal conductivity in Al1-xScxN alloys with the Sc content (x) up to 0.26. The thermal conductivity measured presents a descending trend with increasing x. Temperature-dependent measurements show an increase in thermal conductivity as the temperature increases at temperatures below 200K, followed by a plateau at higher temperatures (T> 200K). Application of a virtual crystal phonon conduction model allows us to elucidate the effects of boundary and alloy scattering on the observed thermal conductivity behaviors. We further demonstrate that the alloy scattering is caused mainly by strain-field difference, and less by the atomic mass difference between ScN and AlN, which is in contrast to the well-studied Al1-xGaxN and SixGe1-x alloy systems where atomic mass difference dominates the alloy scattering. This work studies and provides the quantitative knowledge for phonon scattering and the thermal conductivity in Al1-xScxN, paving the way for future investigation of materials and design of acoustic devices.

cond-mat.mtrl-sci↗

arXiv2020

Bidirectional Microrocker Bots Controlled via Neutral Position Offset

The recent advancements in nanoscale 3D printing and microfabrication techniques have reinvigorated research on microrobots. However, precise motion control of the microrobots on biological environments using compact actuation setups remains challenging to date. This work presents a novel control mechanism and contact design that enables bidirectional steering via biasing the neutral position of the microrobot. Equipped with rockers to contact the substrate, the microrobot, hence microrocker bot, is capable of well-controlled forward and backward movement on flat and non-flat biological surfaces. The 100um by 113um by 36um robots were 3D printed via two-photon lithography and subsequently deposited with nickel thin films. Under a relatively small static magnetic field, the microrocker bot tilts either forward or backward to align the thin film magnetization direction with the magnetic field lines. When combined with an oscillating magnetic field, the robot undergoes stick-slip motion in the predisposed direction, dictated by the neutral position tilt. The microrocker bots are further equipped with sharp mechanical tips that can be selectively engaged. When the frequency and offset of the actuation sawtooth waveform are optimized, the robot travels up to 100um/s (1 body length per second) forward and backward showing very linear trajectories. Finally, to prove the functionality of the microrocker bots in direct contact with biological surfaces, we demonstrate the robot's ability to traverse forward and backward on the surface of a Dracaena Fragrans leaf, and upend/engage on its mechanical tip.

cs.RO↗

arXiv2020

On the Forward and Backward Motion of Milli-Bristle-Bots

This works presents the theoretical analysis and experimental observations of bidirectional motion of a millimeter-scale bristle robot (milli-bristle-bot) with an on-board piezoelectric actuator. First, the theory of the motion, based on the dry-friction model, is developed and the frequency regions of the forward and backward motion, along with resonant frequencies of the system are predicted. Secondly, milli-bristle-bots with two different bristle tilt angles are fabricated, and their bidirectional motions are experimentally investigated. The dependency of the robot speed on the actuation frequency is studied,which reveals two distinct frequency regions for the forward and backward motions that well matches our theoretical predictions. Furthermore, the dependencies of the resonance frequency and robot speed on the bristle tilt angle are experimentally studied and tied to the theoretical model. This work marks the first demonstration of bidirectional motion at millimeter-scales, achieved for bristle-bots with a single on-board actuator.

eess.SY↗