Lunar Wheel
From Clemson Engineering Design Applications and Research
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[edit] Goals
- Constructing an endurance testing apparatus (carousel) to evaluate the behavior of lunar wheels on varying terrain geometries of sand.
- Testing will also focus on mechanical wear of the wheels and tread materials over longer distances (10,000 km) than what has been tested before.
- Acquire four revelant measurements: Relative Slip, Applied Load, Applied Torque and Ground Deflection
[edit] Background
The NASA Lunar Wheel Endurance Testing Apparatus project simulates the rotation of a lunar wheel. The simulation of the TWEEL has several objectives to accomplish in order to create a successful testing environment. The turntable subsystem represents the terrain holding mechanism and central pivot point. A large circumference is desired to minimize the effect of apparent turning in the terrain. Large losses occur in this system due to the components in bearing and its large mass. The wheel fixture houses the majority of the sensor systems and must be fixed in order to support those systems. It also supplies power to the wheel, provides the counterweight system, and houses the suspension components. The sensory system will provide the torque, slip, loading, and deflection data. The turntable, at first, will adapt to the forces applied by the TWEEL. Then when further analysis is done, a motor can be added to move the turntable at various speeds. In the future, additions such as a mound generator and a sand sifter can add more realism to the experiment. All terrain is not ideally flat land and compacted. Therefore, these instruments can generate bumps and mounds, and realistic soil behavior.
[edit] Data Acquisition (DAQ) System
The results will be generated from the Data Acquisition (DAQ) System. The DAQ system will focus on persistently acquiring four relevant measurements which will be indicative of wheel performance with regards to the shear band and the tread. These measurements include relative slip, applied load to the wheel, applied torque, and ground deflection.
- Applied Load: An instantaneous load applied to the wheel can be obtained by an appropriately placed load cell. It is important to know the load at the wheel rather than in the suspension or the counterweight system. Therefore, the load cell would need to be integrated somewhere within the wheel mount or hub.
- Applied Torque: The applied instantaneous torque can be determined from the motor as long as the power supplied to the motor is known in conjunction with the induction and capacitance of the motor. As a result, the torque over time can be backed out from the time dependent factors and the instantaneous power supply to the motor itself.
- Relative Slip: The relative slip is the relative speed between the wheel and the turntable. It also gives an approximation of slip which the wheel is experiencing at any given time. This in turn can be used in concurrence with the load and deflection measurements to determine their relations with slip behavior.
- Ground Deflection: Ground deflection requires the instantaneous distance between the center of the hub and the surface of the turntable. Combining with data of the applied load this generates an instantaneous load/deflection curve which can be studied for trending either towards stiffening or softening.
[edit] Publications
Videos:
Recently, there was an article published in the diSCovering Research Newletter about the designing and testing of the lunar wheel. This article provides information on the efforts of multiple developers and students from Clemson. In addition, the cryogenic testing is mentioned as well. EPSCoR/IDeA Article
[edit] Videos
[edit] Pictures
[edit] Endurance Testing
We've found a space to build, once we get it cleared out.
The space is cleared, now work can start.
Our first material shipment- the trough segments that have been bent into trough shape by MTS.
The floor gets painted white to officially claim our building space.
Uh-oh! What now?
Painting is complete- we're ready to build!
The first shipment arrives: the bent sheet metal for the trough
This is the frame being constructed in the jig.
The complete trough frame.
The merry-go-round being built. We have a center column and a trough frame so far.
Part of the trough set on the frame.
The center column.
The base assembly.
With a few cables up, we lift it off the ground for its first test spin.
View with all cables attached.
Lateral center hub is added to reduce trough tilting
Sand is added to the trough.
Power train frame is placed next to the rotating trough. Now we need the rest of the power train components.
The merry-go-round goes merrily around!
[edit] Sand Traction Prototype Testing (Clemson)
Possible Traction test location-1
Possible Traction test location-2
A tire and wheel assembly to be used for sand traction testing prototype.
An adhesive being applied to the backside of the material to be applied to the tire tread.
Compression straps around a nearly finished prototype to aid in curing of the adhesive.
Another prototype curing.
A prototype mounted on the ATV for a test run on pavement. This run tested the adhesive used, wheel mounting adapters, and the wheel revolution counter.
A 50 ft. course marked off to test operation of wheel revolution counter. (Lines on pavement highlighted with with orange for clarity.)
Sand bed on which traction tests are planned
Tire Slip captured while testing Prototype made with carpet textile
Tire path just before the tire starts slipping
