Axel Scoop Sampling Device - PowerPoint Presentation

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Axel Scoop Sampling DeviceSummer Seminar Day Presentation

Nikola Georgiev 08/23/2012

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Introduction to Axel Rover

The Axel rover is designed to access extreme extra-planetary terrain that is characterized by steep craters, overhangs, loose soil.Axel is a lightweight two-wheeled vehicle that is supported by a host platform through a tether and can be detached from the host in order to explore challenging terrain and collect samples.

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Figure 1: Axel deploying an instrument on a slope at Black Point Lava Flow in

Arizona

Figure 2:

Axel rover detached at a cliff

slope at Black Point Lava Flow in

ArizonaSlide3

Objectives of the Project

Design and build a prototype of a sampling device that can efficiently sample loose soils at states ranging from dry to wet and sticky or possibly icy state.Design criteria is maximum capability for minimum actuationTake multiple samples and store them in the Axel’s instrument bay.Allow for access of samples at the central modulus or for a return mission.No Earth contamination or cross-contamination is allowed

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Figure

3: Cad model of Axel instrument bay with deployed instrument panel containing a camera.Slide4

AssumptionsThe samples taken may potentially contain unstable substances, therefore, an effective sealing system has to be included when the samples are stored

Collecting unstable substances would also require fairly quick sealed storage of the sample after collection.The goal of the project is to prove the concept that Axel can efficiently collect samples and store them. Therefore, the device should operate in field tests.4Slide5

Consideration of Existing Sampling Devices

Pneumatic sampling, single scoop and drilling/coring sampling devices were considered.I concluded that each of these devices do not comply with one or more of the objectives/assumptions.5Slide6

Consideration of Container Designs

I considered container designs that would not require additional actuation, investigated in Sample Sealing Approaches for Mars Sample Return Caching by Paulo Younse Even though some container designs are suitable for a return mission, non of them are reusable and allow the sample to be analyzed on site and resealed.

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Axel Scoop Sampling Device.

Considering all of the information presented in the previous slides I decide to attempt to design and build a device that uses its containers as scoops that are sealed through a linear motion of the lid relative to the container.Each container is only unsealed when it collects a sample and is used to acquire only one sample. This way Earth contamination and cross-contamination is avoided.

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Container Design Approach

The container are designed to have the following features:A cutting edge to allow collection of sticky, wet and potentially harder icy samplesCollect and

store approximately 20g of sample materialSide cuts allow for efficient hold of the container by a gripperSealing is achieved

by pushing the cutting edge of the container 0.3mm/0.012in into the seal. The sealing action is achieved by the point contact between the three bearings and specifically designed extrusion on the lid on each side.The lid is held in the proper

place, when closed

by a couple of spring

plungers (not shown in the model)

Due to the fact that the cuts in the container are sufficiently larger than the size of the lid extrusion, no jamming due to dirt is expected.

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Cutting edge

Seal

Gripper cut

Contact

Spring plungersSlide9

Axel Scoop Sampling Device DesignThe objective is to design mechanism that can effectively manipulate the containers in order to collect and store multiple samples with minimum actuation.

The required motions can be carried out by a prismatic joint, a revolute joint and a gripper (in addition to the 4-bar mechanism of the deployable volume, which I had to redesign).

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Axel Scoop Sampling Device

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Container Storage

Gripper

Lid Removal Mechanism

Revolute Joint

Container

Prismatic JointSlide11

Axel Scoop Sampling Device

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Container Storage

Gripper

Lid Removal Mechanism

Revolute Joint

Prismatic JointSlide12

Axel Scoop Sampling Device

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Container Storage

Gripper

Lid Removal Mechanism

Revolute Joint

ContainerSlide13

Axel Scoop Sampling Device

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Container Lid

Gripper

Lid Removal Mechanism

Revolute Joint

Opened Container

Prismatic JointSlide14

Axel Scoop Sampling Device

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Container Lid

Gripper

Lid Removal Mechanism

Revolute Joint

Closed Container

Prismatic JointSlide15

Prototype

The prototype was built in the ME shop. All parts are either 3-D printed plastic or CNC aluminum. It is ready-to-mount on Axel.The motors, encoders, hobby servos are controlled with an arduino.All systems and subsystems are working with good accuracy and control. However, if some of the aluminum parts are remachined

and some of the 3-D parts are made of metal, the performance of the system will improve slightly.Scooping experiments are yet to be carried out as additional calibration is necessary.

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Prototype

The container-lid design concept proved to have a lot of potential as the 3-D printed prototype creates a good enough seal to hold water inside without leakageIt also interacts very well with the lid-removing mechanismPreliminary manual sample acquisition shows that the actual amount of sample that can be collected is lower than the volume of the container

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Prototype Demonstration

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AcknowledgementI would like to thank:

Prof. Joel Burdick and Melissa Tanner for all the help and the great opportunity to participate in the projectAndKeck Institute for Space studies and Dr. Chandler C. Ross SURF Fellow from providing the necessary fundi

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