Publications

1. A. Chhabra and D. Kim
DYNAMOS: Design, Implementation, and Validation of a Hardware-in-the-Loop Simulation Testbed for In-Space Servicing
IEEE Aerospace and Electronic Systems Magazine, Jan. 22, 2026.

The growing number of space missions has led to increased interest in In-space Servicing, Assembly, and Manufacturing (ISAM) operations. Consequently, Hardware-In-the-Loop (HIL) simulations for in-space missions have become an important research area. The authors' earlier work focused on mathematical modeling and validation, proposing a new HIL spacecraft motion emulator design composed of a robotic arm and a Stewart platform, which offers several advantages over existing robotic simulators, such as a wide motion range, improved accuracy, fast response, and flexibility due to kinematic redundancy. This work advances the state of the art by describing the platform's design and construction, outlining the associated software framework, and presenting experimental validation through two ISAM operation scenarios: orbital motion tracking and a module installation.

2. G. Das, A. Vera, D. Choi, A. Chhabra, D. Kim, and B. Jayne
From Nature to Robots: A Comprehensive Survey on Lizard-Inspired Robotics, Righting Reflex, and Space Exploration
Bioinspiration & Biomimetics, Dec. 10, 2025.

Lizards are among the most biomechanically versatile animals, exhibiting a broad range of physical and behavioral adaptations, such as adhesion, agile locomotion, vertical climbing, righting reflexes, and various tail-assisted aerial maneuvers. These features have inspired a growing body of biomimetic technologies spanning robotics, medical devices, and control algorithms. This survey provides a comprehensive overview of lizard-inspired design principles and their applications in engineering systems. Starting from biological foundations, we review key physical and behavioral traits and map them to their engineered analogs, including soft adhesion mechanisms, metaheuristic control algorithms, and multi-modal locomotion systems. Special attention is given to lizard righting strategies in the development of self-righting robotic platforms. The survey also extends to the extraterrestrial relevance of lizard-inspired systems, highlighting studies of lizard behavior under altered gravity conditions. Applications in space robotics are explored through gecko-inspired adhesive grippers, locomotion analogies for planetary rovers, and dynamic parallels between lizard biomechanics and free-floating space manipulators. Despite the growing body of work, a comprehensive synthesis uniting terrestrial and extraterrestrial biomimetic insights has been lacking. This review aims to bridge that gap by mapping the trajectory of lizard-inspired biomechanics from biological foundations to robotic implementations, highlighting key achievements, interdisciplinary linkages, and frontiers for future exploration.

@article{10.1088/1748-3190/ae2b18,
	author={Das, Gargi and Vera Gonzalez, Alhim Adonai and Choi, Daegyun and Chhabra, Anirudh and Kim, Donghoon and Jayne, Bruce C},
	title={From Nature to Robots: A Comprehensive Survey on Lizard-Inspired Robotics for Ground and Space Exploration},
	journal={Bioinspiration & Biomimetics},
	url={http://iopscience.iop.org/article/10.1088/1748-3190/ae2b18},
	year={2025}}
  

3. A. Chhabra and D. Kim
Fuzzy Logic-based Multi-Task Control of a Redundant Robotic Spacecraft Simulator (Accepted, In Press)
International Journal of Aeronautical and Space Sciences, Jun. 9, 2025.

4. A. Chhabra and D. Kim
Ground Robotic Platform for Simulation of On-Orbit Servicing Missions
Journal of Aerospace Information Systems, Jul. 2022.

Autonomous on-orbit servicing missions require high precision because any unwanted contact forces can cause damage to space systems. This makes the on-ground hardware-in-the-loop simulations necessary as operations must be thoroughly evaluated before such missions are carried out in space. A robotic platform is proposed, where a 3-degree-of-freedom (3-DOF) robotic arm is placed atop a 6-DOF Stewart platform. A mathematical model is developed for the resulting 9-DOF redundant manipulator, and the corresponding dynamics are modeled and verified. Simulation studies are conducted using a constrained and singularity-robust pseudo-inverse control scheme, and the systems capability to follow a scaled-down orbital trajectory is tested. The results are presented, and the future implications of this study are discussed.

@article{Chhabra2022JAIS, author = {Chhabra, Anirudh and Kim, Donghoon}, title = {Ground Robotic Platform for Simulation of On-Orbit Servicing Missions}, journal = {Journal of Aerospace Information Systems}, volume = {19}, number = {7}, pages = {480-493}, year = {2022}, doi = {10.2514/1.I011008}, URL = {https://doi.org/10.2514/1.I011008}, eprint = {https://doi.org/10.2514/1.I011008}}
  

5. A. Chhabra, J. Venepally, and D. Kim
Measurement Noise Covariance-Adapting Kalman Filters for Varying Sensor Noise Situations
Sensors, Dec. 12, 2021.

An accurate and reliable positioning system (PS) is a significant topic of research due to its broad range of aerospace applications, such as the localization of autonomous agents in GPS-denied and indoor environments. The PS discussed in this work uses ultra-wide band (UWB) sensors to provide distance measurements. UWB sensors are based on radio frequency technology and offer low power consumption, wide bandwidth, and precise ranging in the presence of nominal environmental noise. However, in practical situations, UWB sensors experience varying measurement noise due to unexpected obstacles in the environment. The localization accuracy is highly dependent on the filtering of such noise, and the extended Kalman filter (EKF) is one of the widely used techniques. In varying noise situations, where the obstacles generate larger measurement noise than nominal levels, EKF cannot offer precise results. Therefore, this work proposes two approaches based on EKF: sequential adaptive EKF and piecewise adaptive EKF. Simulation studies are conducted in static, linear, and nonlinear scenarios, and it is observed that higher accuracy is achieved by applying the proposed approaches as compared to the traditional EKF method.

@Article{Chhabra2021Sensors, AUTHOR = {Chhabra, Anirudh and Venepally, Jashwanth Rao and Kim, Donghoon}, TITLE = {Measurement Noise Covariance-Adapting Kalman Filters for Varying Sensor Noise Situations}, JOURNAL = {Sensors}, VOLUME = {21}, YEAR = {2021}, NUMBER = {24}, ARTICLE-NUMBER = {8304}, URL = {https://www.mdpi.com/1424-8220/21/24/8304}, PubMedID = {34960398}, ISSN = {1424-8220}, DOI = {10.3390/s21248304}}
  

6. D. Choi, A. Chhabra, and D. Kim
Intelligent Cooperative Collision Avoidance Via Fuzzy Potential Fields
Robotica, Oct. 18, 2021.

This paper proposes an intelligent cooperative collision avoidance approach combining the enhanced potential field (EPF) with a fuzzy inference system (FIS) to resolve local minima and goal non-reachable with obstacles nearby issues and provide a near-optimal collision-free trajectory. A genetic algorithm is utilized to optimize parameters of membership function and rule base of the FISs. This work uses a single scenario containing all issues and interactions among unmanned aerial vehicles (UAVs) for training. For validating the performance, two scenarios containing obstacles with different shapes and several UAVs in small airspace are considered. Multiple simulation results show that the proposed approach outperforms the conventional EPF approach statistically.

@article{Choi2022Robotica, title={Intelligent cooperative collision avoidance via fuzzy potential fields}, volume={40}, DOI={10.1017/S0263574721001454}, number={6}, journal={Robotica}, author={Choi, Daegyun and Chhabra, Anirudh and Kim, Donghoon}, year={2022}, pages={1919-1938}}