Session: MESA-06 / MESA-11 / MESA-15

Paper Number: 112409

112409 - A Tale of Two Turrets: Transitioning Hands-On, Project-Based Learning to a Remote Environment 

This paper presents an open-source MATLAB tool developed as a partial ``digital twin'' for a hands-on, project-based learning (PBL) course. The aforementioned course is a semester-long, mechatronic design exercise that guides students through the interface, modeling, and control of a one-dimensional turret system integrated with an electronic NERF RIVAL-series blaster. The digital twin presented is a MATLAB-based simulation that replicates key elements of the existing in-person course for use in a remote setting. Results show a highly visual, open-source tool that accomplishes 55\% of the key tasks associated with the in-person PBL course; allowing students to explore experimental modeling, control tuning, and camera-based feedback techniques in a remote setting. Source code, documentation, and installation functions for the Turret Simulation Toolbox are available at https://github.com/USNA-WRCE/TurretSimToolbox.

The United States Naval Academy (USNA) continues to offer a required course entitled “Guided Design Experience.” This course provides an opportunity for students to solve a multifaceted, mechatronics problem in a semester-long guided engineering design project. While the Guided Design Experience course does not require a specific project semester after semester, the most popular in recent years is the “NERF Turret.” This project requires student teams to work with a one degree-of-freedom (DoF) rotational turret holding an electronic NERF blaster. The project goal is to reliably hit a known target or targets using encoder feedback from the turret actuator, voltage supplied to the actuators within the NERF blaster and turret, and visual feedback from a USB webcam that is rigidly mounted to the NERF blaster. Students are provided: (1) a turret integrated with a brushed DC motor that includes a gearbox and encoder; (2) a NERF RIVAL Khaos MXVI-4000 Blaster modified to expose the leads of the DC actuators; (3) a USB webcam mounted to the NERF blaster; and (4) a support electronics kit including a power supply, breadboard, microcontroller, MOSFETS, H-bridge motor driver, etc.

During mid-March of 2020, nine weeks into the sixteen-week spring semester, USNA was forced into a fully remote-learning environment due to COVID-19. This left >40% of a hands-on course incomplete including the final project assessment. Further, the following constraints were imposed by the situation: (a) students were assumed remote with access to their school laptops and high-speed internet connectivity; and (b) shipment of partial or complete hardware kits was infeasible due to time and resource limitations. Course completion required the rapid development of a software tool capable of providing: (1) angular position data comparable to the actual turret; (2) an angular position control response similar to the actual turret; (3) NERF Blaster shot patterns for approximating ballistics; (4) target images simulated within a relevant context; and (5) an environment to integrate and demonstrate system performance.

The developed digital twin incorporates a turret model, visualization environment and camera simulation, and a NERF ballistics model. The turret model includes two key functions: (1) mimic the realistic open-loop dynamics of the turret, and (2) mimic closed-loop PID position controller performance given controller gains and a desired position. The visualization environment creates a noisy background using actual classroom images scaled to linear units and placed within a simulation space. Within this space, simulated lights are added, and objects including targets, labeled crosshairs, etc. are inserted. Realistic simulated images are created rapidly using specific property settings of the MATLAB axes object, and details to mimic this approach are provided. Lastly, the ballistics model is approximated using five terms and an assumed multivariate Gaussian form.

Results show a realistic non-linear turret PID control response including asymmetry for positive and negative desired positions. Visualization results demonstrate a good correlation between real and simulated images, appropriate scaling of inserted calibration objects, and appropriate color variability of targets using simulated lighting and out-of-plane “wobble” of target orientation during placement. Ballistics results show appropriate distribution changes with range, and variability of sampling for a fixed range. Lastly, a performance analysis tool is presented showing simple assessment capabilities.

Presenting Author: Michael Kutzer United States Naval Academy

Presenting Author Biography: Michael D. M. Kutzer received his Ph.D. in mechanical engineering from the Johns Hopkins University, Baltimore, MD, USA in 2012. He is currently an Associate Professor in the Weapons, Robotics, and Control Engineering Department (WRCE) at the United States Naval Academy (USNA). Prior to joining USNA, he worked as a senior researcher in the Research and Exploratory Development Department of the Johns Hopkins University Applied Physics Laboratory (JHU/APL). His research interests include robotic manipulation, computer vision and motion capture, applications of and extensions to additive manufacturing, mechanism design and characterization, continuum manipulators, redundant mechanisms, and modular systems.

Authors:

Michael Kutzer United States Naval Academy
Levi Devries United States Naval Academy
Tracie Severson United States Naval Academy