Biomimetics and Dextrous Manipulation Lab


category: SummerBlogs

Marcela's summer blog

Day 1, Week 1

June 19th, 2018

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Alternative materials ranked from least flexible
to most flexible. Original material is laid
horizontally across the bottom above the final material

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SuperSCAMP model with new legs

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Marcela in BDML for summer 2018

Today I helped Stephanie with SuperSCAMP, mostly working on the robot's legs. The material we were currently using, a carbon-based material, was durable and somewhat pliable, but not flexible enough for the type of movement we were looking for. SuperSCAMP's legs should allow the robot to translate horizontally and vertically and curl when scaling a surface without a bowing motion. I spent most of the day looking for an alternate material that was slightly more bendable than the carbon, without sacrificing strength and sturdiness. I cut several strips of material out of different carbon sheets and tested for flexibility by analyzing how it bent and comparing how it functioned to a piece of the currently used material of the same size. Oftentimes, the material would seem strong enough when tested as a a full sheet, but would become significantly less sturdy and sometimes would even curl and twist when cut to the same length as the current material. On the other hand, other materials were too brittle and would easily fray when cut with scissors, demonstrating that it would most likely break if used for superSCAMP's legs. I was unable to find a material that worked when cut to the same width as the current material. Thus, I decided to use one of the materials that was too flexible and make it stronger by increases the width of the strip. Once I created a strip with the desired thickness and flexibility, I attached it to the pulley system on SuperSCAMP's body.

Day 2

June 20th, 2018

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Active spine mechanism with a spring

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Prototyping with springs and legos

Today I listened in on a meeting between Stephanie and Will where they discussed possibilities for incorporating old spine ideas and current drones onto SuperSCAMP. We looked at several spines with different functions: one was meant for rough, flat surfaces and used an active mechanism, another was used for the same surfaces and used a passive mechanism, and the last spine was meant for rough, round surfaces like trees. The mechanism that was most applicable to SuperSCAMP was the active mechanism. When we returned to the lab, I analyzed the system that this spine used and prototyped with legos and rubber bands to try to create a similar system that could work for SuperSCAMP. The property of the old spine that I was trying to mimic was it's ability to compress, using a spring, and allow the spines to attach to a surface when perching, and then expand when taking off from a surface.

Day 3

June 21st, 2018

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Sketch of previously used mechanism. This
one uses a tube sliding system

Because Stephanie is now rethinking the design and purpose of SuperSCAMP, I spent most of today researching past projects that were similar to SuperSCAMP and reading about how they overcame the challenges we're facing now. As mentioned earlier, we would like to use an active mechanism for SuperSCAMP because even though the motors make it heavier, slower, and less energy efficient, it makes the robot easier to control and results in a higher perching success rate. We also decided that superSCAMP will most likely use one actuator (servo) and that it will use 2 opposing groups of spines to allow the robot to adhere to the wall using shear forces. After reading several papers on past related projects, like SCAMP, I analyzed how they created their system and I noted whether they used mechanical stops, a cable and pulley, a tube sliding system, or another unique system. Additionally, I looked into how different projects designed their spines and how they mounted them to allow for compliance in the x and y direction.

Day 4 & 5

June 22nd and 25th, 2018

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SolidWorks part file for base

Day 4 was mostly just a cleaning day, aside from lab meeting, but today I spent most of my time learning about Sam's project and past iterations of the project. I then began to create a SolidWorks part for a newer model of the project. The piece I'm creating will serve as a base that will attach to a handle for physicians to grip onto and three sliding glass tubes that will allow the machine to have a more optimal, controllable motion. The base I created in SolidWorks includes a hole in the top, designed so that many different types of handles can fit in the space. This part attaches to the glass tubing on each of the three legs using a universal joint, which allows for relatively frictionless motion in the x and y direction and slightly more friction when rotating. Also, I included circular trusses connecting each of the legs for support.

Day 6, Week 2

June 26th, 2018

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Practice gecko skin pieces

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Football demonstration with gecko adhesive

I spent most of this morning finishing up the SolidWorks part for Sam's project. I am working on adding the correct dimensions to the base so that it fits properly with the handle and the universal joints. Later, I helped Tony create more gecko skin adhesives. Earlier this week, I watched him use the reusable mold to create a layer of gecko skin on a fiberglass backing. Although this attempt did not work out, I was able to see the process of using a mold to create the gecko skin. After Tony made a successful mold with a different backing, I cut and pieced together several different gecko adhesive strips that will be used for demonstrations like the football demonstration show in the picture. In order to get the hang of how to cut and fix the pieces together, I practiced on pieces whose microwedges had already begun to deteriorate. I then made a successful new gecko adhesive strip and tried it out with the football demonstration. This new strip is a slight improvement from the older ones because I cut out the unused gecko adhesive in the middle of the strip and replaced it with a different material, saving some of this extra material to be used for different projects or demonstrations.

Day 7 & 8, Week 2

June 27th & 28th, 2018

Yesterday was lab retreat at the Portola Redwoods State Park. It was really nice to bond with the other members of the lab, and it was helpful for me to hear about which careers that alumni from the lab go into and what their experience is like there. Today I finished the SolidWorks part for Sam's project by adding some fillets to the part's edges and ensuring that the dimensions were correct. Later, Tony got me up to speed with what they're currently working on for the NASA space gripper, the current problems they're encountering, and what their plan is for possibly resolving these problems. I will most likely be helping to finalize the gripper design, which will involve some CAD and 3D printing, and I will be able do a little bit of programming and playing around with sensors. I also got an Arduino micro controller today and Tony then began to teach some of the basics to me, explaining the difference between digital and analog, event driven tasks, timers, and breadboards. I'm really glad I have some programming experience because even though Arduino is in C, the concepts all seem very familiar from the class I took this year and I think I will be able to understand everything much quicker now. Overall, I'm really excited to be practicing more mechanical skills and rapid prototyping as well as some programming and circuits, which I'm not quite as familiar with but would really like to learn.

Day 9-11, Week 3

June 29th-July 3rd, 2018

For the past couple days, I have mostly been assisting Tony in creating new gecko adhesives and learning more about the process of creating the gecko adhesive tiles for the NASA space gripper. The most difficult and meticulous steps are intended to make sure that each tile is completely flat, otherwise the tile will not adhere as well. Additionally, we had to be very cautious when making the strips of gecko skin, in order to prevent bubbles from appearing in the gecko adhesive or from ruining the mold by accidentally tearing off the micro wedges. Today we made 3 successful pieces of gecko skin, two with the flexible backing and another with the fiberglass backing.

I also did a lot of research today on possible designs for a small 2 leaf spring that will attach the tile to the rig. First, I studied what the most common uses for leaf springs were, including automobiles and battery contacts. Typically, they exist in a vehicle's suspensions systems and they provide support for the vehicle while also absorbing any uneven surfaces over which the car travels. For cars, they are often made out of one, or multiple, thick pieces of steel. However, for smaller leaf springs like battery contacts, which are more similar to what we will be using, they can be made out of spring tempered steel, or even paper clips depending on its intended usage. In the end I decided to go for a relatively simple design in which the bolts will be perpendicular to the tendon and in line with each leaf on either side of it. I will make several copies of this leaf spring with varying thicknesses for the leafs. Tomorrow and Friday I plan to work on the CAD files on Onshape for the leaf spring so that we can laser cut them as soon as possible. I will also CAD a test rig that will be designed so it is easy to disassemble and adjust the tension in the springs. This will be helpful in collecting some data and seeing how successful the springs are.

Day 14, Week 3

July 6th, 2018

Today I finished laser cutting the test rig and leaf spring designs that I had been working on. Tomorrow I will on assembling the test rig with the leaf springs, tiles, gecko adhesives, and tendons. I will run some tests to see how well the new design for the 2 leaf spring works with each of the different sized leafs. I slightly modified my previous design, keeping the two bolts perpendicular to the tendon and the 2 leafs on either side of the tendon.

Day 15, Week 4

July 9th, 2018

Succesful test rig with the 2-leaf
spring lifting a piece of glass

I made a successful test rig today using the leaf spring with only two points of contact. This rig only had one pair of tiles, but we plan to make more tiles and springs tomorrow so that we can assemble a piece with 2 pairs of tiles and see how well it works. The 1 pair rig weighs 21g and it has a ~13g preload. I used the leaf spring with the smallest leaf width, which was 0.05", so that the system would be lighter and the k value would be less, leading to a smaller activation force.

Day 19, Week 4

July 13th, 2018

4 tile rig prototype

Sheet metal model of leaf spring with 2 bends

This week, I have been working on creating and improving a 4 tile test rig for the NASA gripper. On Tuesday, I assembled the 4 tile rig with the 2 point of contact leaf spring. It worked consistently, but only with a slightly larger preload than its own weight. Thus, I spent the rest of the week trying to improve the rig so that it adhere easily with only its weight as a preloading force. First, I added a second bend to the ends of the leaf spring so that the tile would rest more evenly across the surface of the spring. However, this did not improve the adhesion as much as I had hoped, so I began to explore other opportunities for improvement.

I noticed particular inconsistencies across the 4 tiles, preventing the 4 tiles from being on the same plane when pressed against the surface. Some of the holes that were drilled into the 3D printed test rig and the 3D printed tiles were too big, causing some of the tendons and bolts to slide. This significantly limited the rig's adhesive abilities. Therefore, on the next 3D printed parts, we will use smaller taps to drill the holes.

Additionally, because of the current process we are using to bend the leaf springs, they are not all bent consistently to the proper degree. Because of this, I spent most of today creating two bending rigs in Onshape that will consistently bend each spring and will be able to bend 2 springs at a time. I also edited our current CAD file for the leaf spring so that it is a sheet metal model and more realistically and accurately represents how the leaf spring should bend in order to achieve consistent adhesion. I measured the exact degree to which the spring should be bent and designed the bending rig based off this measurement. Now that I have CAD files for the bending rigs, I plan to 3D print them using the Object printer on Monday morning so that I can bend the leaf springs and assemble an improved rig next week.

A week from Monday I will be presenting my research process so far at the SURI meeting. In order to practice for this, I presented the NASA space gripper project to the tour group of high school students today. It was helpful for me to get a chance to explain our project, give a demonstration, and answer questions, because this is very similar to what I will be doing at the meeting. I oftentimes also find it helpful to teach others about what I'm working on in order to fully understand it myself.

Page last modified on July 13, 2018, at 07:36 PM