SpringLinear Actuator

A Single-Wheel Test Rig for Ocean Worlds: Fall 2018 UpdateYe Lu1, Athul Pradeepkumar1, Madhura Rajapakshe2, Maxim de Jong3, Brian Aiken3, James M. Longuski1, and Sarag J. Saikia1

1School of Aeronautics and Astronautics, Purdue University, West Lafayette, IN 47907, USA | lu496@purdue.edu2Ravenna Lab, Smithers Rapra Inc., Ravenna, OH 44266, USA

3Thin Red Line Aerospace, Chilliwack, British Columbia, V2R 5M3, Canada

Presented at NASA Outer Planet Assessment Group Meeting, September 11-12, 2018, Pasadena, CA

JPL Variable Terrain

Tilt Platform

JPL Rover Single

Wheel Test Track

CMU Single Wheel Soil

Imaging Testbed

MIT Robotic Mobility

Group Test Rig

Testing Capability MIT CMU JPL1 JPL2 Proposed

Single Wheel ✔ ✔ ✔Drawbar-Pull ✔ ✔ ✔Wheel Slippage ✔ ✔ ✔Soil Shear Imaging ✔Endurance ✔ ✔Large Diameter Wheel (>1m) ✔ ✔ ✔Vehicle Dynamics ✔Extreme Surface Features ✔ ✔Slip/Camber Angles ✔Active Load Control ✔

Ocean Worlds potentially offer regions varying from as smooth as

sea ice to as rugged as high cliffs, deep crevasses, blocky ice

boulders and tall penitentes. However, there is a lack of high

resolution image of Ocean Worlds surfaces.

▪ Earth analogs include: Penitentes, Glacial Chaos, Cryogenic Ice,

Salt Evaporates, and boulder fields

▪ Tire rig testbed flexible design accommodates all type of terrain

features and simulants

Modular Surface Simulant Testbed

Capability Comparison of Select Test Rigs

Hardware Selection

and Order

Tool Development

Test Rig Assembly

and Fabrication

Test Rig Testing

and Validation

Testing Method Development

2018 Q4 2019 Q1 2019 Q2 2019 Q3

Project Timeline

▪ Three solar system’s “Ocean Worlds”—Europa, Titan, and

Enceladus—believed to harbor sub-surface oceans and the

potential for habitable environments (hence life beyond

Earth) are interesting targets for planetary exploration.

▪ Exploration cadence:

o Flyby/Orbiter Lander Surface Mobility

o A mobility system enables science investigations at

multiple difficult-to-reach locations

▪ Challenges in test rig development:

o Low gravity condition

o Rugged terrain features

▪ No testing facility dedicated to mobility systems for Ocean

Worlds exists. The primary objectives of the technology

development is

1. Design, fabricate, and validate a single-wheel test rig for

Ocean World rovers

2. Design and fabricate a low-fidelity proof-of-concept

expandable and conformal test tire prototype for Ocean

World rovers.

Project Overview

Enceladus

Titan

Europa

This work is being supported by the 2016 COLDTech program funded by NASA.

Acknowledgment[1] Gregory D. Puszko, “Terramechanical Analysis of Rover Wheel Mobility over Simulated Martian Terrain at Various Slip

Conditions and Vertical Loads”, MIT, 2013 [2] Karl Iagnemma, “A Laboratory Single Wheel Testbed for Studying Planetary

Rover Wheel-terrain Interaction” MIT Technical Report 01-05-05, 2005 [3] Giancarlo Genta and Cristiano Pizzamiglio, “Testing

of planetary rover wheels: Design and setup of a testing machine”, 2016 IEEE Metrology for Aerospace, 2016 [6] Ishigami et al.

“Terramechanics-based model for steering maneuver of planetary exploration rovers on loose soil”, Journal of Field Robotics,

No. 24, Issues, 3 2007. Image Credits: ESA, NASA, JPL, GRC, CMU, ATI, firgelliauto.com, dynapar.com

References

Primary Sensors and Actuators

Linear actuator Electric motor 6-axis force and

torque sensor

Draw wire sensor

To achieve a low gravity testing

condition, the design incorporates an

active load control mechanism:

▪ Spring is compressed to lift load

▪ Linear actuator compensates for

terrain features and controls the load

Testing load range can be customized.

Simulation result shows the accuracy

of load control is within 1 N.

Dynamic Load Control Slip and Camber Angle Control

Variable slip and camber angle is a unique

capability of the test rig, which allows full

performance characterization of the tire under

different testing conditions.

▪ The tire is mounted to align its centroid with

the pivot of the spindle.

▪ The test rig can achieve

o Active slip angle control

o Preset camber angle

Linear Actuator

1. Wheel climbing performance

• The test rig simulates climbing

condition using dynamic load

control

Potential Add-on Capabilities

2. Full-Vehicle Mobility Facility

• The test rig can be reconfigured

for a full-vehicle performance

testing

Tire Design

Spokes tensioned

during deployment

Oblate spheroid,

unpressurized UHPV

UHPV fabric

Wear-resistant

Inner and outer Annuli

for deployment and

structural rigidity

The proposed tire features:

• Scalable to large diameters

• Extreme cold, wear resistance

• Puncture-proof

• Excessive tire deformation,

conformality & traction

• Lightweight tires

The prototype will be a low-

fidelity assembly that is approx. 1

m in diameter and 0.15 m in

width

Spheroids housed within UHPV

annulus using tension tendons

shown in red