Week 10: A Retrospective

On Tuesday, June 3, we presented our product to the group. Although we were not ultimately successful in integrating all of the mechanical, electrical, and software systems into a final product, we did design and manufacture almost all separate components to working condition. A video of these processes can be seen below.



Despite this setback, our product was met with positive feedback. The audience appreciated the music, aesthetics, systems, and complexity of the project, and the presentation overall went well. As a team, we were extremely grateful for this whole engineering experience. It was very informative in a number of respects, and all of us will look back on it as we continue into the professional world.

Given another week or so, we believe we could meet our overall goal, and perhaps that will be possible, depending on the living and academic situations of each of the team members in the future. However, if not, we are still pleased with the progress we made, and appreciate the opportunities we had this term.

The team

Week 9: Control Box and Small Modifications

Primarily, this week focused on developing the final report. However, more progress was also made on the project.

Small changes were made, like drilling holes into the frame for speakers and affixing a door to the back of the frame. This door is a simple piece of backboard which can swing open and close on hinges. Featuring a deadbolt, it allows for access to the inner workings of the final product while still keeping all components within the frame. Handles were screwed into the frame to allow for easier transportation of the entire product. Minor tweaks in programming occurred to continue accurate communication with the modified electrical system. Finally, as another jumper mechanism is being printed out, the current mechanism was fine-tuned by sanding down pieces of it for smoother backboard movement, and gluing small metal brackets to help guide the jump movement.

Additionally, a control box was designed and constructed. This was a relatively simple task. Using scrap wood, a small, handheld box was built with slots into which the push buttons were embedded. This allows users a contained and visually-appealing method of controlling the player figure.

As the jumper mechanism was modified, the lift mechanism was changed as well to reflect these modifications. In order for the jumper mechanism to travel along the length of the lift mechanism to move the player figure in the direction of the x-axis, the jumper mechanism must fit inside an upside-down T-shaped slot. Initially, the plan was to route this into the lift mechanism, but it became clear that this would be difficult to physically accomplish with the given tools. In place of this, two L-shaped brackets were glued to the lift mechanism to create the desired T-shape. An image of this can be seen below.

The jumper mechanism will move underneath these brackets

Week 8: Circuitry and Programming

This week focused primarily on circuitry and programming, as electronics and control are the final pieces of the project as it comes together.

Unfortunately, it turned out that the solder job done on the servo driver was faulty; due to some misunderstandings and a lack of experience, the jumper cables did not properly connect to servo driver, and the driver was damaged beyond use. After turning to a more experienced upperclassmen for assistance, a new circuit was built on a larger breadboard.

Through this new circuit, communication with servos was achieved, signifying a large step forward in programming - coding the program is actually the easier step when compared to establishing communication. Through the breadboard circuit that had been set up, some simple code was written to communicate varying frequencies to a servo, which results in a faster or slower servo rotation. A video demonstrating this can be seen below.



In addition to these advances, minor changes were made to the lift system: a groove was cut into the backboard, giving the ball a slot to ride on; the rubber tubing was glued to the PVC column; and a ramp was affixed to behind the backboard, which allows the obstacles to exit the lift shaft and enter the play area again.

Week 7: Simulations, Models, Soldering, and Programming

As planned, a CAD model of the character jump mechanism was modeled and sent to be 3D-printed. This mechanism functions by sitting on the lift and rolling from side-to-side on it; in front of the backboard is a seat for the servo. The servo can rotate a pair of gears, which let the figure placeholder and its accelerometer rise within a groove in response to a jump command. Pictures of these models can be seen below.

A front-angle shot of the movement mechanism; this is what the player will see

A back-angle shot of the movement mechanism; this section comes in contact with the lift

Additionally, a simulation was made using MATLAB to calculate the speed the obstacles would attain at the endpoint of a ramp, as constrained by the degree tilt of the ramp. A video looping this simulation can be viewed below.

The process of soldering the circuitry together began as well. A servo driver was purchased last week; this will act as a channel of communication and source of power for the five servos involved in the device, as the Raspberry Pi is not powerful enough to power the servos sufficiently. A progress picture of the soldering can be seen below.

Nick and Valerie soldering the servo driver

Once the driver soldering has been completed, the process of communicating between the Pi and the servos will begin. At this point, the Pi is connected to a wired network, which can then be remotely accessed via Secure Shell. While this is useful, a more convenient solution would involve the Pi connecting wirelessly to a network for completely unshackled programming. As such, this is one of the current secondary objectives. A picture of Andy writing the MATLAB simulation and Amndeep communicating with the Pi can be seen below.

Amndeep and Andy programming

However, regardless of the wireless or wired nature of the connection, as soon as the driver soldering is done and the servo driver is connected to the Pi, communication between the Pi and the servos can begin - which will be a substantial step forward.

Week 6: Moving Forward on Manufacturing

A lot was accomplished this past week. In addition to making additional purchases of electronics (such as extension cords and speakers). Numerous hours were spent in the machine shop turning the theoretical design into physical reality. Along the way, sometimes it became clear that an idea would not work in practice as well as it did in theory; the lift was determined to be too opposed by friction when it enclosed its vertical columns, it was decided instead to place it between the vertical columns and the backboard.

Servos were also mounted to the inner top of the frame. To do this, the servos were screwed to wooden blocks, which were screwed to the main frame to act as extrusions. The current plan is to attach plastic spools to their rotary disks and have them spin continuously, pulling or releasing the lift by way of nylon string, but implementation has not yet occurred as the jumping mechanism has not yet been printed to the point of being functional. The servo configuration can be seen below.

The servo is attached to wooden blocks, which are attached to the frame

Furthermore, the physical ball conveyor also underwent its initial construction. This conveyor was discussed in the previous update: essentially, it acts similarly to an Archimedes screw, forcing the balls up a locked channel by seating them on a rotating helix. A brief mechanical simulation of this technique can be seen in the below video. (Full screen viewing is recommended, as the video is small otherwise.)

The placement of this conveyor can be seen in the picture below; it should be noted that this picture is a rough initial positioning, and does not display the channel through which the ball will travel or the servo which will rotate the helix.

Estimated and unsecured location of conveyor

In order to be sure that the servos ordered were sufficient for the project's purpose, some calculations were carried out.

The first calculation determined if the servos would be able to raise the player lift beam. The specifications for the servo were given by the manufacturer that, stating that the device's torque was 3 kg*cm; the mass of the wooden lift beam was 0.4 kg, as calculated with the wood's density and dimensions (and inflated somewhat to ensure that the servo was more than sufficient). 

Since τ = F x r, r = τ/F, in which r gives the maximum possible radius of the pulley. Plugging in the values results in (3 kg*cm)/(0.4 kg) = 7.5 cm. As the servo radius pulley is much smaller than this, it should be capable of the task at hand.

The second calculation dealt with determining the length of tubing needed to build the conveyor ball lift. Given that the tubing (radius = 3/16 inches) will be wrapped around a 2-foot shaft (radius = 5/16 inches) at a rate of 1 coil/inch, the total radius (Rt)of the device is (5/16 + 3/16) inches = 1/2 inch. Since the number of coils = (2 ft)/(1 in) = 24 coils, the total needed tubing length = (2πRt)*(number of coils) = (2π)*(1/2 inch)*(24) = 75.4 inches, or 6.3 feet.

It was initially expected to need 25 feet of tubing; however, by doing these calculations, an appreciable sum was saved by reducing the order to 10 feet of tubing.

Week 5: Purchasing Mechanism Materials and Changing the Conveyor Belt

On Saturday, April 26, the team met to purchase materials for the mechanical and software aspects of the toy. Matthew ordered a Pi Cobbler Kit, which interfaces between a breadboard and the Raspberry Pi; a breadboard, to transmit signals from the Raspberry Pi to, ultimately, the servos and game functions; fishing line, to lift the figure movement shaft; steel balls of 0.5" diameter; brackets to stabilize the barrier between the main game environment and the ball conveyance shaft; three high-torque servos to lift the figure movement shaft and activate the conveyor belt; push buttons for player input; micro-servos to handle figure jumping and conveyance shaft opening; and jumper wires for breadboard circuitry. Most of these materials have since arrived.

It was also decided to scrap the idea of a physical conveyor belt, as shown in previous model renders, in favor of a variation of the Archimedes' Screw. This essentially is a double-helix of rubber tubing wrapped around a revolving tube made of PVC pipe. The ball enters the conveyance shaft, is trapped between two static wooden columns, and sits on the rubber tubing. As the PVC tube rotates, the rubber tubing appears to shift upwards because of its helical orientation; with the ball being trapped between the two wooden columns, it is forced to move upwards by the helical tubing. As the ball moves up the conveyance shaft, it spins against the PVC tube, and eventually reaches an opening that allows it to drop back into the game environment.

This design is much cleaner, simpler, and less expensive than the original conveyor belt design; instead of purchasing, in addition to a servo, an ANSI chain, gears, and wooden platforms, and being forced to combine all of these, all that is needed is a PVC pipe, rubber tubing, and a servo.

Week 4: Designing the Frame and General Maintenance

Over the course of time between Weeks 3 and 4, it was agreed to split up and do research and purchasing for materials and resources. This included a trip to Home Depot to pick up quantities of wood for the frame and structural materials such as wood glue, screws, and braces; an order of Plexiglas; and the research and collection of hand tools and machine-shop tools available.

Additionally, the blog was overhauled to reflect the design theme of the project further. This involved designing and implementing customized HTML/CSS markup, establishing a unique color scheme and appearance beyond the standardized Blogger layout, and organizing the links and posts to make navigation of the site more efficient and intuitive. Although it would be easier to simply use the preset layout, it was decided a well-designed website would improve the aesthetic appeal of the product as a whole.

Reconvening on Tuesday for Week 4's lab, much of the time in lab was spent determining the dimensions of the frame and marking up the wood as desired; immediately following lab, the wood was brought to the machine shop to be altered to match these designs. This allowed the immediate construction of the frame, matching the deadline imposed by the proposed schedule. These dimensions can be viewed in the picture below:

Picture 1: An illustration of the box dimensions

The box is 18.5" wide, 23.75" high, and 9.5" deep and features four ramps, each 0.75" high and reaching from the edge of the conveyor space to 3" short of the opposite side of the box. These ramps differ by 3" at their closest sections. A width of 4.5" was allotted for the conveyor space.

Overall, it was a very productive lab. All items needed for player movement and frame completion were purchased on Saturday, April 26, to meet the schedule for manufacturing.

Week 3: Nailing Down the Concepts

The final proposed idea for the Pirate Arrrcade! was presented to the instructor and met with approval. A simulation of the mechanical properties was made in AutoCAD; to view this simulation of the model in greater detail, view the following promotional video:

     

Basic model (back)

     
The basic model shows the ramps, front panel with slots, space for the vertical conveyor belt, and figure movement mechanism. The vertical conveyor belt, attached to a servo, will carry the steel balls from a hopper at the bottom of the arcade to the top of the arcade and eject them down the ramps. The figure movement controls will enable the user to jump over balls and cease motion. The initial design calls for a magnetic sensor in the figure to detect magnetic ball collision; when the magnetic sensor reads a magnetic value (that is, a ball passes within proximity of the player and therefore the sensor) and results in a negative endgame.

Figure movement mechanism

The initial figure movement mechanism is comprised of two servo motors attached to a gear which climbs up two shafts. The bracket attached to the figure will be attached to a ball bearing within the slot of the horizontal beam. This will allow for x-direction movement as the beam moves upwards. As a result, the figure will move up the ramps.

Concept drawing

The concept drawing shows possible ideas for design.  The function of the game will be worked on, and then design will be considered, but the concept drawing illustrates the aesthetic ideas behind the arcade.

The toy concept was presented to children for their input. Its appeal was graded on a scale from 1 to 5. Furthermore, during this time, changes were made to the initial design of the game.  Plans were developed to acquire raw materials and tools, research the resources available for woodworking, and make a frame by next lab meeting. The group decided to meet every other night on Floor 15 of Millennium Hall to maintain accountability and project movement. The formal design proposal was started in Week 2, and will be completed by Friday. 

Modified collision detection

The initial plan for collision detection between magnetic balls and the figure was to use a magnetic sensor on the figure.  To simplify this mechanism, the figure will have an accelerometer attached to its axle (the blue box on the model).  This accelerometer will detect when the ball collides with the figure.

The initial design for the figure movement included two servos and gears to climb up two vertical shafts.  This will be modified to two servos connected to a pulley to lift the beam with the ball bearing and figure.  The new approach will be less complicated than fitting a gear to a vertical shaft.

Below is a tentative list of materials and a rough timeline for the project.  Several systems will be developed in conjunction to expedite the process and improve testing time.

Materials and Timeline

Process	Materials	Tools and Resources
Frame Week 4	24” x 20” x 9” frame with base Backdrop Hinges (2) Handle Lock Wooden ramps Plexiglas cover	Screws/screwdrivers Drill Wood glue Machine shop
Figure movement and jump Week 5	Servo motors (2) Cables Axle, pendulum, figure* Pulley Push buttons (2) Raspberry Pi Wires Connectors Battery 5-gram servo or piston Beam with slot Ball bearing	Soldering gun Pliers Solder
Cannon balls Week 7	10 steel balls Bike chain Ball platforms* 1 servo Gear Battery 1 piston 1 “door” (barrier between hopper and conveyor)*	Soldering gun Solder
Ball Detection Week 7	Accelerometer Wires	Soldering gun Solder
Testing Weeks 7-10	Miscellaneous; as needed

* denotes 3-D printing

Finally, testing was discussed. Testing will be performed with the individual systems listed in the first column, and then with the systems integrated together as each is developed. The core of the game should be built as soon as possible to assure enough time to fix errors. More research and planning will help decided where and how to build each system.

Week 2: Coming Up with a Project Design

At the start of this term, there were numerous ideas floating around for different toy designs, but nothing concrete. The ideas considered included engineering toys marketed towards girls; helicopter battle sets; a remote-controlled basketball hoop; a gyroscope controlled by human motion; and music games that required players to mimic pitch and rhythm. For these assorted concepts, discussion occurred further to determine what would be practical to design and enjoyable for children to use. The design choice selected to propose first was the remote-controlled basketball hoop, with an aesthetic style of jungle wildlife to entertain the demographic of children ages 5-7.

Unfortunately, this proposal was not accepted. After numerous hours of sketching out different designs and suggesting and rejecting ideas both concrete and abstract, a new idea came into consideration: an arcade-style, interactive obstacle course.

From a prototype perspective, the design consists of an upright box with alternating ramps at varying height levels. The player controls a character which moves at a constant speed up the ramps; two buttons offer the player the ability to make the character jump and stop its motion up the ramps. These two controls are the only tools the player has to avoid the obstacles: small metal balls which roll down the ramp system at random intervals towards the character. The game is won when the character reaches the highest ramp without colliding with any of the obstacles.

To propose the idea, more work needed to be done: it was an interesting prototype, but it lacked character. An aesthetic design was needed. Those considered included a jungle theme, an industrial theme, an antique theme, and, finally, a pirate theme. The latter was immediately selected as the best choice. The obstacles became cannonballs launched down the swaying deck of a ship, dodged by a swaggering captain gamely attempting to get to his treasure; the box lost its prototype look and became a chest, and the project became Pirate Arrrcade.

Week 1: Project Overview

AHOY MATEYS!

Our goal is to create a fun game where you get to move up wooden planks, dodge cannonballs and find booty! You can come aboard for entertainment starting at ages seven and up.  Building this Pirate Arrrcade experience will not be an easy feat.  It will require integrating mechanical and electrical systems through an Arduino. The mechanical systems will include Pirate Joe's ascent, jumps, and wait times.  Electrical and software systems will range from sensing cannon ball collisions to obeying user input on the control buttons. Lastly, the design of the game will be enhanced to give you the full benefit of a buccaneer's life at sea!

Follow our voyage journal and charts for weekly updates.  So get your hornpipe and join us on this swashbucklin' adventure!