So this is my summer worklog:

Monday 24 July 2006 So I've been working mostly on assembling the second stickybot body. Right now, I'm waiting to use the Haas for the first time, to machine some of the limb pieces that didn't turn out the first time. The assembly is a lot more difficult than I thought it would be. So far I've done some drilling and tapping of polyurethane, a lot of filing motor horns so that they can slip with less friction, and a lot of supergluing. Another project on the back burner is obtaining dessicant for the toe pad production, and also obtaining chemicals to try modifying the surface properties of the polyurethane. Woo, chemistry. The surface modification examination is getting rather interesting- I've found an area of research which has the same goal. The production of MEMS creates nanostructures which get close enough to experience van der waals forces, as well as other sticking forces. I'm not sure exactly what the literature says, yet, but some interesting things talk about modifying the surfaces of nanomaterials to be rough, to reduce the van der waals attraction, and others discuss low surface energy coatings that are suitable for silicone.

Friday 14 July 2006 Taking some data for wax melting points to capture the polyurethane pillars. Point to WaxProperties.

Tuesday 11 July 2006 Ok, so we've actually shifted gears this time smile Mark has decided to make Stickybot performance more of a priority than the Rise platform sticky feet. So now I'm assisting Sanjay with the assembly of some circuit boards. In the meantime I'm also researching chemical modifications to the sticky pads that could allow us to increase pillar density: BlockedPillars. I think I might also build a miniature van der graaf generator to investigate electrostatic effects on polyurethane- but that'd be a rather silly project. Well, how about a request for comment- anyone reading this, please post ideas for putting an electrostatic charge on a sticky pad? So far a van der graaf generator, and a huge voltage difference using the foot as an electrode have been suggested...I'm not sure either makes sense. Electrostatics in general probably are a bad idea, since part of the point of the sticky pads is that they are passive, require no energy, and are biologically inspired. I think that it is much more "mimetic" to use chemistry to modify the properties of the pads. While we wait for the body to cure, I'm also thinking through this idea for a SafetyLine for stickybot.

Thursday 6 July 2006 Actually, it seems like we've kind of dug in our heels- while Ren and I have been working on scaling Sangbae's feet, we've honestly been spending more time working on alternative actuation mechanisms. I'm still really amazed at the mechanism Ren's working on- the initial design used a single pull cable, distributing force along each segment to generate the same moment in each segment. It moved really cool (one segment at a time) could handle obstacles decently well (curling around them), but had a huge tendency to buckle, which some FBDs revealed was in fact a feature of the design :). I've spent most of the past week and a half struggling with statics analyses of various designs, but things really got cooking when I noticed that our designs acted like a finger and did a few literature searches. My favorite out of these is this article: which talks about the development of a prosthetic. What piqued my interest is that their problem is similar to the one that I decided we were trying to solve- distributing forces equally amongst the segments of a robotic foot. I do think that my demands are more modest though- I just want the forces to be equal when the foot is splayed out against the wall. Anyway, I've got a page here discussing some analysis of a human hand inspired foot design: GrabFoot.

Tuesday 27 Jun 2006 Looks like we're going to shift gears- rather than do a dramatic redesign of the feet for Quadrarise, we're going to try to scale Sangbae's feet, preserving most of the initial design. Matt has also suggested that it will be worth the effort to add actuators for the curling of toes. I'm also beginning to read up on Finite Element Analysis- I think it'd be really useful and also neat to have FEMs of the sticky pads and toes. I was also introduced to Derrick's project, incorporating spines into the tips of the sticky feet. Looks neat, and I note that he's using a very different sort of prototyping method. While Ren and I have been brainstorming and then building foamcore models, he's been making models in solidworks- I've got to ask Sangbae what he called them, but something to the effect of models which test a single critical parameter of the desired device. It makes me wonder if this is a more efficient approach for design. In any event, Ren and I are going to spend more time working in solidworks. Some of the scaling issues we thought of immediately include: Does the size change actually increase the compliance requirement? Can we achieve the same curve which Sangbae used, given that we have a maximum tool height of 20mm? What will scaling do to the stiffness of the foot? Will the joint be sufficiently compliant, given that the push pull cables currently restrict the range of motion? How will we alter the foot to accomodate RiSE's ankle?

Monday 26 Jun 2006 So last week Allen took responsibility for giving Amanda, Ren, and I stuff to do. I ended up working with Ren on designing sticky feet for QuadraRiSE. The sticky foot design took a lot of turns- we started out playing with some adhesive pads, styrene, an ankle joint, in order to get an intuitive feel for the materials. Some interesting things: a foot sized pad of styrene alone is sufficiently flexible that it will not make complete contact with a wall when loaded from the bottom, that we'll need on the order of 18sqin of sticky material, the sandwich sticky pads feel really cool when squeezed... Then we started bouncing ideas around, and eventually started making feet from foamcore and styrene, getting a handle on the problems we needed to solve. Unfortunately, as we made more prototypes, problems appeared and disappeared. For example, Sangbae indicated that the curling mechanism used to detach StickyBot's feet from the wall seemed unnecessary as a result of the anisotropic dry adhesive. So that problem, incorporating an actuated detachment mechanism as easily as possible into the feet, vanished. It seems now that our major problem will be better compliance, to accomodate proportionally larger feet (geometry makes compliance more important at edges). The idea that I'm currently working on is prototyping a pipe/pipe joint to redirect normal force from the ankle joint to the edges of the feet. The hope would be that this would provide a level of compliance by pinning the edges of the rigid foot to the flat substrate.

Sunday 18 Jun 2006 I'm thinking that this page will function as a notebook- both for communication and also to get my thoughts organized. So, if you're reading this, I'm afraid that these won't be polished thoughts necessarily:

Last friday I got a chance to meet everyone in the lab at the lab retreat. That was really exciting- I compare it to a previous work experience where I had no idea who exactly my coworkers were :). We also learned about each person's summer work goals, which was also a great introduction to each person's research project, since it was focused on what they'd be doing over the summer. It seems like I'll mostly be working with a guy named Matt, on the QuadraRiSE project. I wish I'd thought to mention some of the questions I'd had- like the hours he usually worked, his phone number/email etc. but I guess I'll catch him sometime Monday and figure it out. Right now, I'm wondering what the introductory session the department is holding tomorrow will be like. I'm also thinking about planning a lab event- I'd like to have a Kite flying/barbecue day, where we can go down to Roble field, set up a small grill and have burgers, while some people make and fly some simple kites, and others play frisbee/ have an impromptu soccer game. I'm also concerned about the amount of reading I should be doing- I've spent most of this weekend hanging out with my family as opposed to prepping as much as I probably should. And housing- I still need to get two references to my landlord.

Materials: Tissue paper Rubber Cement Wooden dowels Kite string Exacto Knives Pens Portable Grill Veggie Burgers Burgers Buns

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