Useful Links: ME112Notes, FinalProject2014, Biology Literature, Materials, Construction Tips, DuckObservations

15 March 2014: Great show everyone! And here's a nice writeup in the Alumni News.
25 May 2014: Congratulations to John, Marcos, Karan and Bryan for their Hoefer prize winning design document.

A certain internationally famous theme park 'destination resort' company takes great pride in creating a holistic experience of pleasure and entertainment. Everything -- including the costumed characters, the amazing rides, the shows and even the meticulously landscaped grounds -- is designed to surprise and delight. As part of this effort, a substantial budget goes into designing and maintaining beautiful flower gardens, manicured paths, ponds, fountains, and waterfalls.

a duck feeding frenzy

Of course, where there is water, you also get waterfowl. At first there are just a few of them, and they look real cute. And then people feed them. And you get a mess...

The company, which practically invented animatronics, is looking for a solution to this problem. The artificial can be so much more pleasing than nature itself! But there are challenges. The Duckamatronic creatures will have to convey the same sense of serenely cute paddling motion that real ducks do. Unlike an animatronic Abe Lincoln, they aren't rooted to the ground with hidden levers and pneumatic tubes. They're going to have to run on rechargeable batteries and they are going to have to propel themselves with an appropriate paddling motion. Their feet will be visible below the waterline -- alas, no propellers and no underwater towing cables.

The company in question turns to ME112, which has become famous for its biomimetic final projects. Surely the creative engineers that have made Lemurs, Turtles, Elephant Seals, Dragons, Horses, Rabbits and Sloths in previous years can come up with a Duck to surprise and delight for 2014.

1.  The Challenge

Create an autonomous, battery-powered animatronic waterfowl that propels itself using an authentic bio-inspired paddling motions. Don't worry too much about decoration; focus on performance. You can imagine that company will provide a lightweight shell to cover whatever you create. (There is some internal debate at the company about whether to go for a "naturalistic" or a "Donald/Daisy" aesthetic...)

2.  Design Requirements

2.1  Functional requirements

• Create a stable, autonomous, bio-inspired craft that floats and propels itself with "legs" and "feet."
• The vehicle should swim at a leisurely duck-like speed of approximately 0.35 m/s
  • (see Prange 1970 for why the speed should not exceed sqrt(g*L/2*pi), where L = length).
• The vehicle will be powered using onboard rechargeable NiMH batteries. There is a desire to maximize battery life while proceeding at an appropriate speed. However, this project does not focus on energy efficiency to the extent of the Crawlers (been there, done that).
• The vehicle will not be remotely controlled. Instead it should maintain a reasonably true course "open loop." There will be plastic side-rails installed in the water course (Terman Pond Arrillaga West pool) where it is tested. However a manually adjusted "trim rudder" is advised to ensure that it does not tend to go in tight circles or bang stubbornly against the side rails.
• In addition, the company asks for one additional biomimetic motion -- this could be a head motion, tail motion, etc. The design document produced by the team should also describe this feature clearly enough that the company can accommodate it in the outer "shell" that they will provide.

2.2  Physical requirements

• The watercraft should be the approximate size of a small duck, about 24cm long and should be able to paddle in water 13cm deep or greater. The final demonstration will be in Terman Pond Arrillaga West pool, and the water could be somewhat choppy.
• Any materials that are in continuous water contact should be highly water resistant, capable of hours of operation without failure.
• The prototypes should be very low cost, using readily available prototyping materials. PRL-approved plastics could be ideal for underwater components. Acrylic is brittle, so we will provide some sheets of polystyrene to help teams get started. Feel free to augment these with other materials.

3.  Project Requirements and Organization

In addition to presenting a final working device, the project requires that you prepare for a series of design reviews at the conceptual, preliminary and final design stages. All members of the team must be fully briefed on all aspects of the project prior to the design reviews. The teaching team should be able to ask any question of any team member and get a correct response. At each of the checkpoints, we want to see your project schedule for the remaining time period, and we will look for specific items listed below:

3.1  First Design Review

This project involves mechanism design, analysis and fabrication. At this design review, we want to be sure that you are thinking about each of these aspects and scheduling team activities over the four weeks. In particular, we are looking for:

1. Sketches and perhaps Lego or other models showing concepts for your design.
   • We'd like to see at least one unique idea per team member
   • We'd like to see at least a couple of the ideas brought to a physical state (i.e., not just a rough sketch). Legos, cardboard, tape and other rough prototyping materials are fine.
   • The ideas could focus on the paddling mechanism, the transmission from motor to mechanism, or the layout of the watercraft and how it will fabricated and trimmed. All of these may turn out to be important.
   • Feel free to bring videos of concepts tested so that you can talk about early lessons learned.
2. Team organization – Show us your team web page, that you created (similar to Crawlers). Make sure you have an email link that can be used to send email to all team members. If you don’t have a photograph, we will take one in class so you can upload it to your page. We will use this team page as a portal to your team activities.
3. Evidence of planning -- We want the team to consider all of the challenges involved in the project: what questions you need to answer and how you intend to divide up tasks? You should have a calendar marked with required project deadlines, team time conflicts and team deadlines for resolving the challenges. Specifically:
   • When will you settle on a winning concept?
   • When do you need to order parts (lead time)?
   • What kinds of parts do you need?
   • Who will make parts in the PRL?
   • Who will create and and who will review computer programs needed to analyze motions, velocities, torque requirements?
   • Who is going to out of town, or has a major deadline, and when? -- and what is your plan about that?

Please turn in a single two-sided sheet with your names, team name and one or two figures that capture the gist of your current best idea(s).

Scoring:

• Early design space exploration 3pts (1 = weak, 2 = OK, 3 = honors)
• State of the designs & early prototypes or experiments (how realistic, how much attention to detail) 4pts
• Team organization 3pts

3.2  Second Design Review

At this point you should be well on your way to a working design. Bring some documentation and prototypes to make this clear!

Hardware (5 points)

• A functional prototype of a legs mechanism should be demonstrated. The idea here is to think about things like fasteners and parts chosen to form the joints.
• The prototype need not be finished, but we want to see real three-dimensional parts. Ideally the structure will be made from either final materials or easily substituted proxies for final materials (for example, if you will use laser cut plastic, you could show laser cut masonite or cardboard at this stage, but not preferably not hand-cut cardboard and duct tape).
• Show use of realistic fasteners for joints, shafts, etc.
• The structure does not need to be motor drive at this point, but it should be clear how it will be driven.

Analysis and explanation (5 points)

How well do you understand your design? If you can't do a good job of explaining it, you don't understand it as well as you think...

1. We want to see your updated project timeline and discuss your choice of design for the Duckbot. In particular, we want to see

to-scale design drawings for the major parts required, including dimensions and notes

1. A kinematic analysis of the "authentic paddling motion" and accompanying computer program
2. A preliminary analysis of your motor and drivetrain -- will it have enough torque at each stage of the cycle? Will it have enough power? Will it burn through batteries at a horrifying rate?
3. Specific plans for what each team member will do over the next, rather intense, week. Contingency plans for what you will do if something does not work out as planned.

Please turn in a short "briefing document" that contains your main kinematic analysis results (e.g. plots) and parts drawings. Consider this a head start on your final documentation.

3.3  Penultimate Design Review

The objective of the final design review is to convince the reviewers that you will have a working device during the presentations on Friday that meets all specifications. One obvious way to satisfy them that your device will work is to have a device that mostly works! You should be able to address all of the design requirements and demonstrate that your device currently meets them or the steps you will take to ensure that they are met by Friday March 14 in Arrillaga West pool. A Working Model or other simulation of the device can also provide support that you will meet your objectives.

As mentioned in class we'd like to hold the Penultimate Design Reviews at the kiddie pool outside of MERL133 with your design in the water. In terms of what to focus on, think "FUNKtional Prototypes" (a term borrowed from ME310). That is, functional but perhaps still funky. Focus should be on basic functionality versus "nice to have" stuff.

3.4  Final Demonstrations

Final demonstrations are held on the last day of classes, Friday 14 March in Arrillaga West pool. We will begin at 12:30 and go as long as it takes for all teams to show us their stuff (we hope to be done by 2:00). We will have several "lanes" for the animatronic ducks to swim in. Invite your friends.

• 13 March: See DuckObservations for advice based on what we saw on Wednesday March 13.

Performance metrics:

• Duck moves stably through water at moderate speed
  • 10 points if 30cm/s < speed < 50 cm/s (measured by timing linear progress along the lane) -- speed scoring will be generous.
  • 5 points if 18 cm/s < speed < 65 cm/s
  • else 2 points if it completes the course across the pond
• Biomimetic locomotion: 5 points (by vote of the judges)
  • displays minimal thrashing or churning (it's an elegant waterfowl, not an egg beater)
  • does not list heavily to one side or display other symptoms of serious imbalance
  • goes reasonably straight and does not spiral in circles
• Bio-inspired additional feature (e.g. head, bill, tail, wings): up to 5 points (by vote of the judges)

*Biomimetic behavior will be assessed by teaching team, using input from the audience. We care about motion more than aesthetics for this prototype.

4.  Grading

Grading for the project will be based not only on the final design and report, but also on the intermediate design reviews and analysis. (Learning an effective design process for projects like this is a valuable experience.) The approximate relative weight of each portion of the project is as follows:

4.1  Design reviews

• First design review: 10 points
• Second design review: 10 points
• Penultimate design review: 5 points

4.2  Design Performance

• Duckbot demonstration performance (see notes above): 20 points

4.3  Duckumentation

• Final documentation 40 points (20 points for content, 20 points for presentation clarity)
  • See the Documentation guidelines on Coursework for details - the final document guidelines are nearly the same as for crawlers. There is also a pretty good example of a previous year's report in the Final Project folder. This example is marked up in Word, so turn on "Track Changes" and view changes to see the comments on each section.

5.  Resources

5.1  Linkages

Check out the (4.5) linkages links on the ME112 Notes page.

5.2  Materials

• We are providing 2 sheets of 1/8inch polystyrene to help teams get started with underwater components. See the (coming... materials page) for more tips.This material can be cut by hand or on the lasercams in PRL.
• Other necessary parts (e.g., motors, gears, shafts) must be purchased by the teams. To assist with this, we will provide links to useful catalogs along with samples of motors and drivetrain elements that you might consider. Remember that this should be a very inexpensive 1st prototype.
• Everyone who uses the PRL must participate in safety training. If you have not had safety training this academic year, there will be opportunities in the next couple of weeks.
• A drill press and some simple hand tools will be provided in MERL 126. Please let the teaching team know right away if anything is broken. Also be aware that these tools are for minor on-the-spot alterations. For any serious cutting, etc. you want to use PRL so that you get good quality results.
• A battery charger for AA size NiMH (nickel metal hydride) rechargeable batteries will be provided. These batteries provide a good tradeoff for power/size. A couple of power supplies will also be provided for testing voltages and currents. Ask the TAs if you need to find resistors, alligator clips, etc.
• A kiddie wading pool will be set up outside the lab for testing

5.3  Prototyping Advice

The tips below are just a starting point - there is a FinalProjectMaterials page with much more!

1. You may notice that the voltage, size and weight are roughly in the same ballpark as the previous project. Thus your Lego bricks, gears and motor may prove useful for putting together initial prototypes. You may want to replace the flimsy Lego shafts with metal rods, gluing the gears to them with epoxy.
2. When planning a drivetrain and choosing the motor, you may want to think about ways in which you can alter your design easily. For instance, if you can swap pulleys with a chain drive, you have a degree of freedom in setting your gear ratio. Similarly, if you have a gearbox that is capable of multiple speeds, you can use this to tweak your design when prototyping.
3. The devil is often in the details! You should give some thought to issues such as how you will attach elements such as gears, pulleys, sprockets or links to shafts and how you will ensure that things are properly aligned and not wobbly. This has been the main failure mode of projects in the past! It may be worthwhile to perform some simple tests to see where you will need bearings and how much “slop” your design can tolerate.
4. Batteries can be modeled as a constant voltage and an internal resistance (per Assignment 4). The internal resistance varies with different battery types, but you should be able to devise a simple experiment to determine it for the batteries you are using. If you want to avoid burning through batteries while testing, you can simulate a battery using the power supplies and a resistor equal in magnitude to the internal resistance.

5.4  Literature

See: FinalProject2014Literature for (Prange 1970) and other useful articles and videos.

• Main.FinalProject2014Dates

FinalProject2014Literature