Elevator Actuated Clamp & Anti-Crush Mechanism

First principles design to harness mechanisms already in use off-planet

Contributions: Designing, building, and testing elevator actuated clamp and anti-crush mechanism

Project Overview

As an intern at Honeybee Robotics during the summer of 2023, I was responsible for designing and building an extraterrestrial sample cup clamp for a vibrational mass measurement system that utilizes the existing elevator architecture present in the Sample Analysis at Mars (SAM) carousel system for actuation so that additional clamp release actuators could be omitted for the sake of minimizing weight and complexity. I also designed an anti-crush mechanism to protect the vibrational mass measurement system’s actuator and sensor from forces involved in its analysis chamber sealing process. Unfortunately, I am not permitted to display the internals of either aforementioned mechanism.

Elevator Actuation of the Clamp

When the system is lowered to the lowest possible point by the Sample Analysis at Mars sample carousel elevator, (thumb screws acting as a substitute during the prototyping process) the V-shaped stoppers (grey) collide with the horizontal poles protruding from the sides of the upper clamp jaw (red), causing the spring between the upper and lower jaws (orange) to compress, which allows the clamp jaw to open and the sample cup foot (magenta) to be removed horizontally by the rotation of the Sample Analysis at Mars sample carousel (rotary aluminum block acting as a substitute during the prototyping process). The V shape is designed to rotate the upper jaw's horizontal openings into alignment with the sample cup carousel's rotary path.

Anti-Crush Mechanism

When the upper section of the sample cup (magenta) is sealed in a spectroscopy chamber, large forces load the entire system vertically. When this occurs, the lower spring (not shown due to NDA) beneath the platform (cyan) attached to the bottom of the piezoelectric transducer (lime green) is compressed, causing the piezo housing (blue) and the lower clamp jaw stopper (conical feature of yellow part) to collide and divert the sealing load around the fragile piezoelectric vibrational actuation and sensor system. To the right is an early model of the mechanism that better displays the gap between the lower jaw stopper and the piezo housing.

Stress Analysis for Weight Optimization

Fuel consumption minimization constraint
Optimized strength-to-weight ratio
Utilized Autodesk Inventor stress analysis tool

Open-Ended Inception of Design

I proposed several quick-change coupling methods designed to be actuated by the movement of an onboard elevator already present in the SAM carousel architecture and highlighted the advantages and disadvantages of each.

Collet Chuck

Over-Center Latch

Alternative Sample Measurement Methods

Before the vibrational mass measurement method was chosen for development, various other mechanisms were considered. It was decided that methods that require physical or optical exposure of the sample with an open or windowed container posed too many risks. Additionally, centrifugal mass measurement was deemed too delicate for the application Honeybee Robotics had in mind for the Dragonfly mission to Titan, but would be well suited for environments with microgravity.

Laser Rangefinder

Non-contact probing of a sample without altering the proposed container opening would entail inserting a photonic periscope horizontally into the mouth of the sample cup with a four-bar linkage or similar mechanism, given the dimensions of the cup and commercially available rangefinders.

Series of Laser Tripwires

This design requires optical windows on the side of the container and additional infrastructure to prevent a sample from clinging to the walls due to surface tension and electrostatic force. Additionally, this method was unable to analyze transparent substances such as water or liquid methane, the latter of which is abundant on the surface, the intended destination for this mechanism.

Confocal Rangefinder

Use of this commercially available model requires altered cup dimensions or light cone demagnification. Additionally, slight atmospheric changes risk altering the hue of the confocal rangefinder's light, potentially throwing off measurements.

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