PRELIMINARY DESIGN, PRELIMINARY DESIGN, FABRICATION AND TESTING OF FABRICATION AND TESTING OF THE FWTHE FW--350 LUNAR FLEXIBLE 350 LUNAR FLEXIBLE

WHEEL PROTOTYPEWHEEL PROTOTYPE

Mohamad Farhat, Erick Dupuis, Mohamad Farhat, Erick Dupuis, Stephen Lake, Alessio SalernoStephen Lake, Alessio Salerno

ASTRA 2011ASTRA 2011

ESTEC, Noordwijk, ESTEC, Noordwijk, The NetherlandsThe Netherlands

ObjectivesObjectives Investigating utility of flexible wheel to Investigating utility of flexible wheel to

reduce number of rover wheels normally reduce number of rover wheels normally needed at low ground pressure needed at low ground pressure

Developing flexible wheels technology for Developing flexible wheels technology for planetary explorationplanetary exploration

Flexible Wheel ConceptFlexible Wheel Concept Emulating the pneumatic radial tire design Emulating the pneumatic radial tire design

in functionin function OffOff--road vehicles traction is of particular road vehicles traction is of particular

interestinterest Pneumatic radial wheel functions were first Pneumatic radial wheel functions were first

decomposed then the initial wheel design, decomposed then the initial wheel design, FWFW--100, was synthesized to emulate 100, was synthesized to emulate functions and their interaction. functions and their interaction.

IntroductionIntroduction Wheels is a critical mobility technologyWheels is a critical mobility technology Design reliable and robust wheelsDesign reliable and robust wheels FWFW--350 flexible metal lunar rover wheel 350 flexible metal lunar rover wheel

using fastusing fast--prototyping techniques prototyping techniques R&D by the robotics group at CSAR&D by the robotics group at CSA Partnership agreement between CSA, Partnership agreement between CSA,

academia (university of McGill) and academia (university of McGill) and industry (Neptec Inc) on Lunar Traction.industry (Neptec Inc) on Lunar Traction.

Radial Pneumatic TireRadial Pneumatic Tire Air pressure: transmits car Air pressure: transmits car

load to treadload to tread Tread: vehicle load to Tread: vehicle load to

ground and produce traction ground and produce traction

Body ply: holds tire together and transmits Body ply: holds tire together and transmits torque from rim to tread.torque from rim to tread.

Steel belts: a base for the tread and hold Steel belts: a base for the tread and hold the wheel circular shape.the wheel circular shape.

Bead: helps to seal air inside the tire and Bead: helps to seal air inside the tire and provides torque transmission. provides torque transmission.

Wheels RequirementsWheels Requirements Wheel loads 50 to 100 KgWheel loads 50 to 100 Kg Very light construction.Very light construction. High traction. High traction. Power efficient.Power efficient. Low ground pressure terrain.Low ground pressure terrain. Sandy terrain with some rocks.Sandy terrain with some rocks. Path to flight design.Path to flight design. Reliable, 100 Km operation.Reliable, 100 Km operation.

FWFW--100 Wheel Development100 Wheel Development--2 2 Emulates pneumatic tireEmulates pneumatic tire Blue tempered spring Blue tempered spring

steelsteel Chafer and body ply Chafer and body ply

wwerere replaced by radial e replaced by radial bands bands

Bead function is performed by two rim beltsBead function is performed by two rim belts Tread belt: 2X spring steel sheetsTread belt: 2X spring steel sheets Air pressure: VAir pressure: V--linklink

FWFW--100 Wheel Development100 Wheel Development--3 3 Lateral stiffnessLateral stiffness Contact patch size drives Contact patch size drives

design.design. Radial band sides and Radial band sides and

VV--link control pressure link control pressure

Sand trapped between Sand trapped between grousers form a tread.grousers form a tread.

Traction ConceptTraction Concept

FWFW--100 Wheel Development100 Wheel Development--4 4 ATV AL rimATV AL rim Components fasteningComponents fastening Friction dampingFriction damping Issues:Issues:

Tempered spring steelTempered spring steel Lateral stabilityLateral stability Wheel side tractionWheel side traction Manufacturing complexityManufacturing complexity Radial band slipRadial band slip Grousers limited tread flexibilityGrousers limited tread flexibility-- traction traction

FWFW--350 Wheel Development 350 Wheel Development FWFW--100 issues 100 issues Stainless steel Stainless steel SingleSingle--sheetsheet Flexible VFlexible V--grousers grousers Grousers wallsGrousers walls Grousers wire meshGrousers wire mesh CF BeadCF Bead--lock rimlock rim Wire beadsWire beads OOOO shaped pillow like springshaped pillow like spring

Manufacturing Manufacturing

ManufacturingManufacturing--2 2 Water jet Water jet single sheetsingle sheet Bent and folded to form a wheelBent and folded to form a wheel OO radial band pillows OO radial band pillows Grousers were bent separatelyGrousers were bent separately Four wheel prototypes were madeFour wheel prototypes were made Special pressurizing rigSpecial pressurizing rig Grouser wire mesh Grouser wire mesh

Laboratory Testing Laboratory Testing Wheel characterization Wheel characterization McGillMcGill--U single wheel rigU single wheel rig

Power consumption and coefficient of rolling resistance for the wheel was characterised by driving the wheel over the sand bed for a specific distance at various constant velocities for a given wheel loads.

Compared well with rough terrain rubber wheel

Drawbar Pull test was performed on the same test bed using 100% slip. Load was measured by a load cell at different wheel loads

Field Testing Field Testing At the CSA new extended Mars Emulation At the CSA new extended Mars Emulation

Terrain (MET).Terrain (MET). Level and upLevel and up--hill driving hill driving Point turnPoint turn Right patch sizeRight patch size--imprintimprint Grousers DeformationGrousers Deformation BandBand--OO misalignmentOO misalignment All other structural elements held wellAll other structural elements held well

Discussion Discussion Preliminary results indicate that use of Preliminary results indicate that use of

flexible metal wheel has the potential to flexible metal wheel has the potential to reduce number of wheels required for low reduce number of wheels required for low ground pressure planetary operation.ground pressure planetary operation.

SoilSoil--toto--soil grouser concept workssoil grouser concept works Single sheet wheel is less complex to Single sheet wheel is less complex to

manufacturemanufacture FWFW--350 concept is scalable 350 concept is scalable

ConclusionConclusion

Initial results indicate the feasibility of Initial results indicate the feasibility of producing a flexible lunar rover wheel with producing a flexible lunar rover wheel with relatively large contact patch and good relatively large contact patch and good traction while maintaining adequate rolling traction while maintaining adequate rolling resistance.resistance.

Future WorkFuture Work Rigorous field and laboratory testingRigorous field and laboratory testing Wheel failure modes and reliability Wheel failure modes and reliability Investigating use of other materialInvestigating use of other material