Session: 07-10-02: Mobile Robots and Unmanned Ground Vehicles

Paper Number: 114014

114014 - Design, Prototyping, and Experiments Using Small-Scale Helical Drive Rover for Multi-Terrain Exploration 

Rovers designed for polar exploration primarily operate in homogenous terrains, such as the flat and arid central plateau of Antarctic and are unsuitable for the diverse terrains such as slushy snow, wet soil, floating ice, and open ocean, present in the Arctic. The Multi-terrain Amphibious ARCtic explOrer or MAARCO rover is a multi-terrain amphibious vehicle design concept that has been designed to navigate the diverse and constantly changing conditions in the Arctic to perform autonomous research missions. The MAARCO rover uses a multi-functional propulsion system, a pair of helical drives that consist of augur or screw-like rotating cylinders with helical blades. The hollow cylinders also act as ballasts that can be empty, or partially- or fully filled while the rotating helical blades provide propulsion on land, on water and under water.

A small-scale prototype (3:10 scale) was developed to test and evaluate the terrestrial locomotion performance of the MAARCO rover's propulsion system in real-world conditions. The prototype allows researchers not only to evaluate the rover's capabilities more cost-effectively and efficiently than building a full-scale version but also to identify any design flaws, issues, or challenges that may arise before developing a full-scale rover. The small-scale prototype is 18.4 cm tall, 25.4 cm wide, and 33 cm long, and weighs approximately 4.5 kg. Its chassis comprises two quarter-inch thick 6061 aluminum waterjet cut plates spaced apart with three pieces of aluminum extrusion. The modular and easy-to-manufacture chassis enables switching out different helical drives designs with relative ease. The pair of helical drives are 3D printed with ABS plastic material to make them impact and wear resistant. The drive electronics consist of two 12 VDC brushed motors providing 133.2 kg.cm of torque, two brushed motor electronic speed controls (ESC), and a 3s 11.1V LiPo battery. The torque is transmitted to the helical drives via a set of GT2 timing belt pulleys and belts. The ESC’s receive a PWM signal and control the direction and speed of the motors. The PWM signal is either sent through an RC receiver allowing for the rover to be controlled manually for testing electronics and chassis components or through an Arduino allowing the rover to follow a specific set of commands for data collection and dynamic testing. The rovers sensors include an IMU and rotary encoders built into the motors. The chassis is designed to house loads of varying weights to analyze the effect of carrying different types of payloads.

The rover was used to test the performance of the helical drive in different terrains, operating conditions, and driving maneuvers, in a field setting. These tests include transitioning between terrains, straight-line driving in a single terrain and in multiple terrains, turning left and right, and tracking a prescribed path. Tests were also performed to determine the maximum angle of incline that the rover can traverse on different surface media under different payload conditions. Results of the field tests were compared with the simulation results obtained from a dynamic model developed previously by the team. There was considerable agreement between simulation and testing data in the case of substrates with higher shear strength, such as wet sand, wet soil, mud, and clay, where the substrate is less likely to fail. However, on substrates such as sand and gravel, there was considerable disagreement between the two data sets. The results and learnings from these field tests will be used to develop a higher fidelity dynamic model capable of capturing the locomotion dynamics on a wider variety of substrates.

The development of a small-scale prototype has provided valuable insights into the performance of the MAARCO rover's propulsion system, improved rover configurations, and validated the terrestrial locomotion dynamics model of the rover. These results have guided the development of the full-scale rover, ensuring that it is optimized and capable of performing its intended mission in the challenging and ever-changing conditions of the Arctic.

Presenting Author: Ashwin Vadlamannati North Carolina State University

Presenting Author Biography: PhD Student working at the Engineering Mechanics and Space Systems Laboratory at North Carolina State University, specializing in multi-body dynamic modeling and control systems.

Authors:

Ashwin Vadlamannati North Carolina State University
Sumedh Beknalkar North Carolina State University
Dustin Best North Carolina State University
Matthew Bryant North Carolina State University
Andre Mazzoleni North Carolina State University