Animatronic Flower

(A Midsummer Night's Dream)

DISCLAIMER:

I worked with an animatronics team for this show to bring these flowers to life. During the design process, we decided to use another team members similar, but different inner-working design moving forward. The flower that follows is still my design, but the video showing them in action on stage is with the new design. I wanted to show my take on the design without taking anyone else's credit.

Initial Ideation: 

I joined the Purdue Theatre Animatronics team about 6 months ago. Earlier in the year, I helped create animatronic designs for a new take on the production "Frankenstein". (see more here!) I really enjoyed working together with others to make the Frankenstein story come to life in a whole new way! Later, I was told about a new project, for the production "A Midsummer Night's Dream". 

The project was to create around 15 animatronic flowers that could light up and open and close during certain portions of the show. The flowers would be spread out across a bed that Titania laid on during her entrancement from Oberon's love potion. These flowers, when open and lit up would signify her waking up in a pseudo reality and close when she snapped back into the real world. We wanted to create a design that was compact, easily duplicated, and had a fantastical element to best serve the story. We were also told that each flower should have 5 petals. Below are some sources of inspiration for our design:

Brainstorming: 

When first thinking about ideas for this project, I thought of using a flexible push-rod that could be secured on one end to a servo horn and on the other to the "pistil" of the flower that could hold the LED and and move all the petals when activated. After some research I found a different mechanism that sparked yet another new idea. 

I came up with 3 ideas to go forward with: 

• #1: Moving pistil actuated by a servo horn (My original thought)

• #2: Rotating petals with a central worm gear (What I researched)

• #3: Moving pistil actuated by a rotating drum and screw (Newly sparked idea)

I made a mock-up of the first idea and realized it was harder than I originally thought to actuate. The petals needed to move against the spring material (TPU Filament) that helped them open when closing and in doing so created a lot of unwanted friction (see below). I moved on to the second idea, but was having several issues getting the parts small enough with the 3D printer (Bambu A1) that I had access to. I then transitioned to the third idea. This is when I was able to get a working prototype with the new rotating screw idea. 

Designing & Programming: 

I used Autodesk Inventor to design all the parts and assembly for this project. I started by making the main casing that held the 5 pivots for each of the flower petals. I then designed the mounts that would hold the flower petals and allow them to be rotated/open & closed. Next I designed the screw (yellow component), the part that would lift up and spread the petals out. After this, I made an outside casing for the screw that also had the same screw pattern on the inside (blue component). This casing is what would be rotated by the servo motor and transfer the rotational to linear motion. Finally, I designed a servo mount that also acted as a cap to the bottom of the main casing.   

After printing out all the parts I got to assembling, starting with the screw and screw casing. I screwed the 2 pieces together and made sure they could rotate freely (I also added a little lubrication to help with this). Next, I put the assembly I just made inside the main casing and added all the small petal mount pieces. I then installed the servo motor on the end cap and connected it to the bottom of the main casing. Finally, I made some flower petals by taking small 1-2 in lengths of PLA filament and gluing a synthetic flower petal to either side. I glued and inserted the filament "stem" into each of the petal mounts to finish the mechanical design. For the light, I made a test circuit with a breadboard, including 5V and GND, a resistor, and a yellow LED. I found the voltage and amp draw for the type of LED I had during normal use and calculated the needed resistance for the circuit to work properly. 

Voltage Source: 5V

LED: 3V, 20 mA

Resistor: 5V - 3V = 2V ==> V = IR ==> R = V/I ==> 2V / 0.02 A = 100 ohms

Once I verified my circuit ran without any problems, I soldered and heat shrunk the resistor to the LED and also added extension wires to be connected to the controller. I then bent the wire and LED around the outside casing to meet with the servo wire. I then glued it in place to make sure it wouldn't go anywhere as the flower was opening and closing. 

Once everything was installed, I used an Arduino Uno to control the LED and servo. For software, I used an animatronics control software called Bottango. This allowed me to easily control the actions of both components in my system with keyframes on a timeline. I was also able to easily set up my servos limits of motion, making sure I never rotated more than I needed to/the servo could handle. The timeline above shows the LED turning on first, followed by the servo's position increasing on a slow curve when opening. Then when closing, the servo's position decreases sharply, with the LED turning off right after.

Troubleshooting: 

The first problem I encountered was when I originally made the screw and screw casing. The amount of motion I was getting wasn't enough for the flower to open as much as I wanted. To fix this, I made the thread coarser on both the screw and screw casing and was able to get almost double the range of motion as before. Below is a before and after look at the screw thread.

Conclusion: 

Although this design was not what we ended up using in the end, I still gained knowledge in CAD software, creating for storytelling, programming, designing for robustness in a theatre mindset, animatronics controls, teamwork, and a lot more from this production. The final version of the flowers ran for 6 official shows and many more rehearsal and test runs throughout the couple of weeks prior to the show starting. It was amazing seeing and hearing people's reactions to the flowers as they opened magically throughout the performance. I love working with others, especially when we can create something bigger than the sum of it's parts. I'm excited for the next animatronics team production project!