Spring 2018: BiPed Ultrasonic Sensor Board Power Test

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By: Jorge Hernandez (Electronics & Control Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Approved by: Miguel Garcia (Quality Assurance)

Table of Contents

Introduction

From the research performed, the number of ultrasonic sensors required to make a bi-ped robot for our project is one. We know one sensor will be used which will cause the robot to only detect objects in a one-directional plane which will act as the eyes of the robot. We are using the ultrasonic HC-SR04 sensor to meet our level two requirements:
Shall be able to see other robots to avoid a collision. The robot will stop completely and wait for a command. (Ultrasonic sensor). This expands further:
1. If the sensors are too far from an object, the robot will move forward.
2. If the sensors are too close to an object, the robot should move backward.
3. If the sensors are within the range of an object, the robot will not move.

Choosing our Ultrasonic

For economical reason, we chose to go with the SEN136B5B ultrasonic sensor as the previous Biped Robot from spring 17’ had left thiers with Professor Hill (along with other parts); L1-8: Micro FOBO shall not exceed a cost of $200 to construct. Although there are more precise sensors all we needed was a sensor to provide a measurement of how far an object is away (3cm-400cm) which the Sen136B5B does well. Another reason why we chose this ultrasonic is to satisfy requirement L1-4: Micro FOBO will be a toy robot based on the design of the FOBO, which make it seem as the eyes of Micro Fobo.

Power Estimates

Due to the fact, the  3DoT board we are using has a 3.3V input is another huge reason we are using the SEN136B5B as it functions at 3.3V, unlike the HC-SR04. We could have used the HC-SR04 but to save space we eliminate the idea of a booster shield which will allow us to use this sensor and other 5V sensors if needed. The global current consumption was very hard to test as it only draws 15 mA according to http://wiki.seeedstudio.com/Ultra_Sonic_range_measurement_module/ which is very low and did not give me a reading when I attached it to a current sensor which would’ve given me the power estimates of this ultrasonic.

 

Fig.1 Ultrasonic 6in Test

Fig.2 Ultrasonic Connections

 

 

 

 

 

 

 

 

 

 

This sketch reads a PING))) ultrasonic rangefinder and returns the distance to the closest object in range. To do this, it sends a pulse to the sensor to initiate a reading, then listens for a pulse to return. The length of the returning pulse is proportional to the distance of the object from the sensor.

The circuit:

  •     +V connection of the PING))) attached to +5V
  •     GND connection of the PING))) attached to ground
  •     SIG connection of the PING))) attached to digital pin 7

Wiring & Code

*/

// this constant won't change. It's the pin number of the sensor's output:

const int pingPin = 7;

voidsetup() {

  // initialize serial communication:

  Serial.begin(9600);

}

voidloop() {

  // establish variables for duration of the ping, and the distance result

  // in inches and centimeters:

  long duration, inches, cm;

  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.

  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:

  pinMode(pingPin, OUTPUT);

  digitalWrite(pingPin, LOW);

  delayMicroseconds(2);

  digitalWrite(pingPin, HIGH);

  delayMicroseconds(5);

  digitalWrite(pingPin, LOW);

  // The same pin is used to read the signal from the PING))): a HIGH pulse

  // whose duration is the time (in microseconds) from the sending of the ping

  // to the reception of its echo off of an object.

  pinMode(pingPin, INPUT);

  duration = pulseIn(pingPin, HIGH);

  // convert the time into a distance

Fig.3 Ultrasonic Test#2

Power Estimates Continued

We choose to go with the Seed Ultrasonic Sensor (SEN136B5B ) as it is 3.3V compatible, the sensor was available from previous biped projects, and to meet requirements for our project which were explained above. This 3 pin ultrasonic requires power, Gnd, and a digital pin has an operating current of 15 mA and can read up to 400cm as tested.

Fig.2 Part 1 Power Estimates Table

 

Fig.2 Part 2 Power Estimates Table

Conclusion

We choose to go with the Seed Ultrasonic Sensor (SEN136B5B ) as it is 3.3V compatible, the sensor was available from previous biped projects, and to meet requirements for our project which were explained above. This 3 pin ultrasonic requires power, Gnd, and a digital pin has an operating current of 15 mA and can read up to 400cm as tested.

References

  1. https://www.arxterra.com/tracking-sensors-trade-off-study/
  2. http://www.arduino.cc/en/Tutorial/Ping
  3. http://wiki.seeedstudio.com/Ultra_Sonic_range_measurement_module/

Spring 2018: BiPed Preliminary Design Documentation

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By: Miguel Gonzalez (Project Manager), Jeffery De La Cruz (MST), Jorge Hernandez (E&C)

Approved by: Miguel Garcia (Quality Assurance)

Table of Contents

Mission Objective

By: Miguel Gonzalez (Project Manager & Manufacture)

Our goal for this project is to design and manufacture a BiPed Robot. This robot will be slightly similar to the BiPed robot that was created in Spring 2016 and another bipedal robot named FOBO, created by Jonathan Dowdall. Our design will be based on FOBO but will be much smaller in size that implements micro servos for walking and turning. For sensing its surroundings, the robot will utilize ultrasonic and Infrared sensors. Other key differences between the FOBO and our micro version of FOBO are that:

  1. The head of our robot shall house a 3DoT board, servos controller shield, and a sensor shield.
  2. The movement of our robot will be conducted via SG90 micro servos that will replace the clunky and oversized Hitec HS-805BB servos.
  3. The legs of our robot will have a more efficient method to mount and utilize its servos for weight reduction and for longer walking steps.
  4. Our robot will utilize Bluetooth technology for user to robot communication and movement control
  5. The robot’s power system will be changed from heavy LIPO batteries to a single Samsung 18650 battery located near the robot’s center of mass.

The mission of Project BiPed is to design the BiPed to navigate a predesigned maze. The BiPed shall be able to navigate the maze with user input from the Arxterra App/Control Panel. The BiPed will be able to memorize the user-defined path and will be able to navigate it autonomously. In addition, the BiPed will acknowledge other robots while traversing the maze and avoid collisions using its sensors. To learn more about the mission objective you can take a look here. For preliminary maze designs and definitions take a look here.

Project: Level 1 Requirements

By: Jeffery De La Cruz (MST Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Will:

L1-1: Micro FOBO will stand on its own without any physical help.

L1-2: Micro FOBO’s electronic components will be easily assembled and disassembled.

L1-3: Micro FOBO will have 2 legs.

L1-4: Micro FOBO will be a toy robot based on the design of the FOBO by Jonathan Dowdall.

L1-6: Micro FOBO will fit within the classroom cabinets shelves. 28”x13”x14.5”

L1-7: Micro FOBO will utilize a 3DoT board or Sparkfun Pro Micro 3.3V/8MHz.

L1-8: Micro FOBO’s part components will be 3D printed using the material carbon fiber PLA.

L1-9: Micro FOBO will not exceed a print time of 7.80 hours. Upon approval of the waiver.

Shall:

L1-10: Micro FOBO shall not exceed a cost of $250 to construct.

L1-11: Micro FOBO shall be 60% or less of the overall size of Jonathan Dowdall’s FOBO

L1-12: Micro FOBO shall detect intersections in the maze.

L1-13: Micro FOBO shall be able to perform static walking.

L1-14: Micro FOBO shall produce 90 degrees turn.

L1-15: Micro FOBO shall be guided through the maze with the use of the Arxterra application.

L1-16: Micro FOBO shall record the path of the maze.

L1-17: The Micro FOBO shall traverse the maze using the recorded path.

L1-18: Micro FOBO shall be able to traverse cloth, paper, and linoleum materials.

L1-19: The Final Biped shall be completed by May 10th, 2018.

Should:

L1-20: Micro FOBO should step over a square rod 1cm tall, 1 cm wide by 10 cm long

L1-21: Micro FOBO should be able to perform dynamic walking

System/Subsystem: Level 2 Requirements

By: Jeffery De La Cruz (MST Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Will:

L2-1: Micro FOBO will be connected via Bluetooth to the app on an android phone.

L2-2: Micro FOBO dimensions of the robot will need to be small enough to fit in a 4in by 4in box for maze purposes.

L2-3: Micro FOBO will use SG90 micro servos.

Shall:

L2-4: Micro FOBO shall use UV/IR sensors to detect intersections.

L2-5: Micro FOBO shall use the color of the maze to establish if it needs to turn. black (0,0,0) green (0,255,0) for line following.

L2-6: Micro FOBO shall use a battery that outputs 3.7V nominal.

L2-7: The user shall use the Arxterra application to move the robot forward, backward, left, and right.

L2-8: Micro FOBO connectors shall be able to connect and reconnect all the wiring in less than 10 min.

L2-9: Micro FOBO wiring shall be nice and clean with the use of terminal blocks, contact pins, 2.0mm PH series JST connectors, and barrel connectors.

L2-10: Micro FOBO shall play a musical tune when the maze is completed.

L2-11: Micro FOBO shall have indicating LEDs to demonstrate either a left or right turn.

L2-12: The Micro FOBO shall record the path of the robot on the 3DoT board or the Sparkfun Pro Micro 3.3V/8MHz to navigate the robot through the maze.

L2-13: Micro FOBO shall use a 3D printed chassis and leg components.

L2-14: Micro FOBO shall measure within 4.5” x 3.25” x 7.25”.

L2-15: Micro FOBO shall weigh no more than the allocated mass of 460g.

L2-16: Micro FOBO shall detect objects 8 inches from it.

Should:

L2-17: Micro FOBO should be able to see other robots to avoid a collision. The robot will stop completely and wait for clearance. (Ultrasonic sensor)

L2-18: Micro FOBO should take a bow at the end of the maze as a victory celebration.

 

System Block Diagram

By: Jorge Hernandez (E&C Engineer)

Verified By: Miguel Gonzalez (Project Manager)

After looking at all the constraints and requirements for the robot our group came up with a system block diagram that could help us visualize how the robot’s components interacted with one another. This diagram made it clear to understand where initial designs should be made and provided great insists to some challenges we would have in the future. For example, we can see the product breakdown structure down below and notice that our robot’s chassis contains more sub-branches than the rest of the diagram sibling branches. This indicates that most of the designing will be involved in the creation of the robot’s main hardware. This would help our manufacturing engineer know that designing of the robot’s chassis should be done as early as possible to prevent set back. Another branch that stands out is the software section. This branch is made up of multiple sections that include Arxterra control, line following, avoidance detection, and turning code. This branch is important as the diagram illustrates that our robot is highly dependent on its software to achieve a successful mission objective.

Fig.1 System Block Diagram

Work Breakdown Structure

By: Miguel Gonzalez (Project Manager & Manufacture)

Once we had a clear idea of how the robot would be made we proceed to create a WBS. A work breakdown structure allows us to list and assign tasks/work that needs to be completed for the success of the robot. The tasked listed on the WBS based on the team member’s job description and are directly imported from the tasks created on the Spring 2018 Task Matrix that can be found here. The diagram below is a much easier method of reading the tasked matrix as it clearly shows each team member’s responsibilities.

Our group consists of three members fulfilling the roles of Project Manager, E&C, MST, and Manufacturing Engineer. Since the group has fewer members than the positions available the manufacturing role of the team was given to the Project Manager.

The diagram below shows the workload of the project and how it is distributed among the team. It is based on the job descriptions and shows major tasks that each person is responsible for. We will be taking a look at each team members role more closely to better understand the structure of the team and its workload.

Fig.2 BiPed Work Breakdown Structure

Miguel Gonzalez (Project Manager)

Fig.3 PM and Manufacturing Engineer Tasks (Blue)

At the top of the WBS in blue, we have the project manager section. Note that in our case the project manager is also the manufacturing engineer and thus the tasks for both roles are given to the same person. The second blue icon shows the tasks specific to the project manager which has the project manager responsible for the following tasks:

  • Creating and managing schedule
  • Creating a budget list
  • Creating the preliminary report
  • Creating the final blog post
  • Creating project video
  • Define Work Breakdown Schedule

The manufacturing tasks given to the project manager are listed to the right side of the WBS also in blue. These tasks are broken down into three sections Mechanical Design, 3D Modeling, and Assembly. These sections were created based on which tasks are needed to be done before moving on to the next section. For example, Mechanical Design is a prerequisite for 3D Modeling and Assemble thus it is located on top of the other tasks.

Jeffery De La Cruz (MST)

Fig.4 MST Tasks (Red)

Moving on to the left side of the WBS (in red), we have all the tasks assigned to the MST engineer. Once again, these tasks are divided up into three sections System Designs, Software, and System Tests. The system designs include tasks that have a focus on research and trade studies that will end up helping with the software development and system test. Once those tasks are done the MST engineer can proceed with implementing the software with the Arxterra control panel and onto an android application. The final tasks for the MST engineer focus on verifying and testing all sections of the robot to see if they are operational.

Jorge Hernandez (E&C)

Fig.5 E&C Tasks (Green)

The final branch in the WBS applies to the E&C engineer and his tasks needed for a successful project. The E&C has the greatest responsibility for the success of the robot becoming operational. His roles are divided into 4 categories Electronics Design, Experiments, Microcontroller, and Control. These categories cover a wide range of tasks that need to be realized to proceed with the overall goal of the Biped project.

Product Breakdown Structure

By: Jeffery De La Cruz (MST Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Fig.6 Product Breakdown Structure

Based on System Block

Sensor Suite

  • The color sensor will be able to detect colors and its data input range Ex, black (0,0,0) green (0,255,0) for line following.
  • Will be able to see intersection sign on the maze and differentiate its color from the path lines.
  • Shall be able to see other robots to avoid a collision. The robot will stop completely and wait for a command. (Ultrasonic sensor/IR)
  • The robot should have to indicate LEDs to show where the robot plans to make a turn (left or right)

Smartphone App

  • Will allow usage of the app to navigate the robot through the maze through forward, back, left, and right commands.
  • Will record the path of the robot in 3Dot board to navigate robot without the user controlling it.
  • The robot will be connected via Bluetooth to the app on an android phone.

Chassis

  • The wiring for the robot shall be nice and clean with the use of terminal blocks, contact pins, 2.0mm PH series JST connectors, and barrel connectors.
  •  All connectors shall be able to connect and reconnect all the wiring in less than 5 min.
  • Dimensions of the robot will need to be small enough to fit in a 6in by 6in box for maze purposes.

Battery

  • The robot power management system will use two 1000mAh 2S 20C Lipo Pack rechargeable LIPO batteries.

Interface Matrix

By: Jeffery De La Cruz (MST Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Fig.7 Interface Matrix

The current interface matrix for the prototype Micro FOBO uses the Arduino UNO. A CD4017BE IC was used to control the eight servos. The output of the CD4017BE IC has then connected the Arduino UNO which will the Robot Poser control the movement of the servos so that the Micro FOBO can walk. The interface matrix will be updated once the 3DoT board or the Sparkfun Pro Micro 3.3V/MHz is acquired. This is currently for the prototype of the Micro FOBO. The excel file containing the interface matrix for the prototype Micro FOBO can be found here.

Prototype Fritzing Diagram for Biped

By: Jorge Hernandez (E&C Engineer)

Verified By: Miguel Gonzalez (Project Manager)

The Fritzing application allows a physical breadboard design to be created digitally. By designing a digital version, the beginning PCB designs can begin. One difficulty with using the free software is that the library does not have all the parts needed for many designs. Using Google, many of the parts required were found with Github.

Here are links to the Fritzing libraries for FOBO:

(If using the Adafruit Servo Driver)

https://github.com/adafruit/Fritzing-Library

(For the Bluetooth Module HC-06 and Accelerometer/Gyroscope MPU-6050)

https://github.com/RafaGS/Fritzing

Fig.8 Electronic Fritzing Diagram

There was nothing to change at all as we are using the FOBO’s same hardware build. We decided

to go with 2 Lithium Ion batteries, 12 servos, and ultrasonic as well. The color sensor is being

discussed since we know Spiderbot wants to use UV sensors but will be added to fritz diagram

once we know the final maze descriptions.

References

Spring 2016 ROFI

Spring 2017 Velociraptor

Updated Fritzing

Mechanical Drawings

By: Miguel Gonzalez (Project Manager & Manufacture)

Related Requirements

Level One Requirements

L1-3: Micro FOBO will have 2 legs.

L1-4: Micro FOBO will be a toy robot based on the design of the FOBO by Jonathan Dowdall.

L1-11: Micro FOBO shall be 60% or less of the overall size of Jonathan Dowdall’s FOBO

Level Two Requirements

L2-2: Micro FOBO dimensions will need to be small enough to fit in a 4in by 4in box for maze purposes.

L2-14: Micro FOBO shall measure within 4.5” x 3.25” x 7.25”.

Micro FOBO Design

For some clarification and for better understanding our design of the Micro FOBO, I have created a color-coded assembly of the robot with matching titles indicating the names of each component. Below I discuss the design of these components that make up the Micro FOBO.

Fig.9 Micro FOBO Colored Parts

As you can see from the image above, the Micro FOBO consist of 9 different parts: Servo Hip, Foot, Servo Band, Servo Bracket, Servo Wrap, Bearing Frame, Body Riser, Electronics Frame, and the Head. Note that Micro FOBO can be made up of multiple copies of the same part component and thus colored coded with the same color. For example, there are four servo bands in Micro FOBO which are shown in light green on the picture. Now that we know which parts make up the robot we can begin looking at the design of each part individually.

Part 0: Servo Hip

Fig.10 Part 0: Servo Hip

The “Servo Hip” component of the Micro FOBO is responsible for attaching the two upper micro servos which are the hip servos. This bracket connects both servos (right and left legs) together to act as a hip bone that allows the robot to move its legs left to right. The connection to the servos is made via servo horns that are provided by the manufacturer. This part has two allocated trenches that match the dimensions of the servo horns allowing the servos to mount to the part. The horns are then screwed onto the servo hip using M2.5 screws that are 8mm in length.

Drawing File

Part 1: Foot

Fig.11 Part 1: Foot

The “Foot” component is the same for both legs and is a simple shoe like design with wide pads on its sides. The extra material on the sides allows a greater amount of surface to touch the floor allowing the robot to balance easier. Currently, this part is in its simplified state as there is not much detail design put on it. This is because the team plans on mounting UV sensors onto the bottom of the foot where the hole is located. This would allow the sensor to be as close to the ground as possible to maintain an accurate reading. Once we receive the sensor additional design changes will be made to this part. Currently, the part allows the ankle servo, which is the servo closest to the ground, to be mounted onto one side of the foot though servo horn cutouts. The horn cutout is located on the inside wall of the part. The hole then allows an M2.5 X8 screw to secure the servo onto the foot piece.

Drawing File

Part 2: Servo Band

Fig. 12 Part 2: Servo Band

There is a total of four “Servo Bands” located on the Micro FOBO. This part is responsible for grouping two micro servos together which forms a section of a leg. The two servos are pressure fitted into the square cutout and thus this part must be dimensionally precise to prevent servos to come loose. This piece had several revisions to satisfy the dimensional accuracy need to keep the servos secure. The servos were measured with a caliper and the thickness of the servos stickers even had to be considered when designing this piece. Due to leg movement constraints, only one servo can have extra material to be screwed onto the part.

Drawing File

Part 3: Servo Bracket

Fig.13 Part 3: Servo Bracket

The ‘Servo Bracket” is a shorter version of part 0: servo hip and serves a similar purpose. This component mounts onto two servos that are located on the servo bands. This allows the second to the top servo to move the lower leg. This piece is located in the middle of the leg and connects the top and lower sections. This piece can be thought as the knee of the robot. Just like the other brackets, there are two cutout trenches that allow servo horns to be mounted and secured through a single screw. This piece can be varied in length to adjust the height of the robot and adjust the walking stride of the robot itself.

Drawing File

Part 4: Servo Wrap

Fig.14 Part 4: Servo Wrap

The “Servo Wrap” is a small piece that attaches the back of the hip servo (top leg servo) to be mounted onto part 5: Bearing Frame. It is connected via an M2 screw that is 18mm in length. The screw goes through the servo, through the servo band, and screws into this piece. A hole on the left side of the wall was added to allow the servo wires to feed through and connect back to the electronics. Notice there is a hexagon trench located near the middle of the part. This trench allows an M3 nut to be placed in that location and lets a screw to secure Part 4 with Part 5. Another key design feature is the chamfer cutout located on the backside of the part. This permits higher degrees of movement from the hip servos by at least 45 degrees more.

Drawing File

Part 5: Bearing Frame

Fig.15 Part 5: Bearing Frame

The “Bearing Frame” is a mirror-like component to part 0 as both pieces work together to provide the connection of legs to body. One of the key differences is that this piece contains two large circular trenches in which a bearing can fit onto. Using a 10mm circular bearing we place it on the part to provide free angular movement to the left and right sides of the pieces. Once the bearings are fitted inside, we can use M3X14 bolts to attach the servo wrap pieces to the left and right side of the Bearing Frame. Since the legs servos are already attached to the servo wrap we effectively attached the two legs to the body of the robot.

Drawing File

Part 6: Body Riser

Fig.16 Part 6: Body Riser

Micro FOBO mainly consists of a head and two legs but this part, body riser, can be considered the body of the robot. This component connects the two attached legs with the head. There are two fork-like structures located at the top of the piece that allows part 0 and part 5 to fit in snugly effectively connecting the two legs to this piece. Part 0 and part 6 are secured through a couple of M3 screws with an approximate length of 16 mm. The back side of this component is flat and has two holes for connecting to part 7 which is the electronics frame. The body riser can be increased in height allowing the robot’s head to be located higher above the legs. We can experiment with changing the height to allow shifting the robot’s center of mass higher or lower as needed.

Drawing File

Part 7: Electronics Frame

Fig.17 Part 7: Electronics Frame

The Electronics Frame is a thin component that is responsible for connecting the PCB to the body riser. The PCB will contain four mounting holes which will allow the board to connect to this part. Note that the part contains extruded cubes that correspond to the location of the PCB hole mounts. These extruded cubes also have a hole cut out to fit M3 screws that secure the board in place. Finally, the part can be secured to the head via similar M3 screws on the side of the part and head

Drawing File

Part 8: Head

Fig.18 Part 8: Head

One of the first challenges in creating a miniature FOBO we observed was that our robot would need to support large amounts of electronic components that used to be on the regular size FOBO. These electronics would need to be smaller in size or our head design would need to optimize to fit all the electronics. Our first design was based on the prediction that the new electronics would have a smaller footprint and thus the head of the Micro FOBO is much smaller. The exact dimensions can be found on the link below. Once the size of the head was set I began to look at some redesigns that I can implement to change the look and functionality of the robot’s head. That is when I stumbled on an image of a tin toy robot from the 1950s.

Fig.19 1950’s Tin Toy

As you can see from the image above this robot has a similar head as the FOBO which gave me the idea of emulating the design of the face. The ultrasonic sensor will take place as the robot’s eyes and the mouth and nose features would simply be aesthetics. Another thing that I noticed was that the tin toy contained antennas on the left and right side of the head. One of the redesigns I wanted to incorporate since the beginning was adding turn signals to the robot and the antennas can certainly be used for that. My idea is to have small 5mm red LED’s as the tip of the antennas that would blink indicating when the robot will turn and in what direction. Finally, we see that there is a small red light on top of the robot that can be designed to indicate on/off status of the robot.

Fig.20 Mechanical Design Improvements

Drawing File        Tin Robot Toy

Resource Reports (Power, Mass, Cost)

By: Jeffery De La Cruz (MST Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Below are the preliminary resource reports for the mass, power, and cost for Project BiPed. As we continue working on Project BiPed, the resource report will be updated to the actual numbers of each mass, power, and cost.

Fig. 21 Mass Report

The total mass of the Micro FOBO is at around 351.5 grams. This mass consists of the following:

Part 0: Hip Bracket x1

Part 1: Foot x2

Part 2: Servo Band x4

Part 3: Servo Bracket x2

Part 4: Servo Wrap x2

Part 5: Bearing Frame x1

Part 6: Body Riser x1

Part 7: Electronics Frame x1

Part 8: Head Compartment x1

Micro Servos x8

Samsung ICR18650 x1

Arduino UNO x1

Servo Shield x1

Ultrasonic HC-SR04 x1

To view the excel file of the mass report, click here.

 

The mass of the Micro FOBO will change because the material used to print the parts of the Micro FOBO will change from regular PLA to carbon fiber PLA. The Micro FOBO will become just lighter but not by much. The mass of the Arduino UNO and servo shield is included at the moment but will be updated once the 3DoT Board of the Sparkfun Pro Micro 3.3V/8MHz is included. Also, the battery case was not included because the position of the battery is to be determined.

Fig.22 Power Report

Cost Report

By: Miguel Gonzalez (Project Manager & Manufacture)

Related Requirement

L1-10: Micro FOBO shall not exceed a cost of $250 to construct.

Project BiPed is one of this semesters robot production division in which a bipedal robot will be designed, engineered, and produced by the end of the semester. One of the most important tasks of any project is to evaluate and determine the cost of production of said products. In this post, we will be looking at the estimated cost of producing the BiPed robot. These costs will solely rely on physical component cost and any design and research development cost will not be mentioned in this post.

As part of the requirements stated by the customer, a budget was set for each project divisions. This is a loosely budget of $250 in which all material bought can be reimbursed in full. Any additional items and/or services that exceeded this budget will be covered by the team members working on the project. To help reduce costs, the customer has allowed access to his lab stock inventory of electronics, hardware, and materials. Borrowed items will be included in the budget table but the costs of the items will not be included in the total money spent.

Fig.23 Spring 2018 BiPed Budget Table

Budget Table (for access to links found on the table)

The above table shows the cost of components we have used and purchased as of April 18, 2018. The budget table above is divided into ten separate columns indicating important information about the used and purchased products. In the left column are the names of the parts and items used by the team to produce the biped robot. To the right of the parts column, is a link section that allows viewers to find the same parts we used for this project online. The table is also set up for invoice collection for any items that were purchased these invoices/receipts are linked on the second column to the right of the table. The budget table tries to incorporate all useful information that may be needed for future part purchases, replacement of parts, and for reimbursements.

Overall, we wanted to make sure not to spend any unnecessary money and to reuse as many electrical components and hardware as we could. It is important to note that some additions to the table will be made as the project continues and more items are needed. Multiple hours of reading past blogs as well as research were done to reduce unnecessary consumption of resources and to allocate as much possible reused parts from previous semester projects. Our total expenditures as of April 18, 2018, is a grand total of $226.54 which is under the customer’s project funding of $250.

Planning & Schedule

By: Miguel Gonzalez (Project Manager & Manufacture)

This schedule is comprehensive and accounts for all tasks that should be completed by the displayed due dates. Using Project Libre, we can list the tasks needed to have a successful project. By using the Gantt chart feature we can see the tasks in a much more comprehensive chart that clearly demonstrates time frames and work periods. All tasks and due dates listed were imported from our class task matrix.

Overall Goal

Of course, like any project, our goal for BiPed robot is to finish every task on time while meeting our initial level one and level two requirements. To succeed, the following Gantt Chart was created with very precise timelines and due dates for procedural tasks that must be met to succeed in completing the BiPed robot on time. When creating the Gantt Chart, we notice three major tasks that are important to the success of the project. These tasks were the general project plan, finalization of the 3D model, and the final blog post. The deadlines for these tasks are March 15th, April 12, and May 8th in that order. Because the completion of these tasks is important we made sure to leave time after deadlines for adjustment and revisions. It is allowable to miss a deadline for tasks, but a penalty exists that increases as time passes. To prevent loss of points, additional precautions were put in place. As a group, we set the goal to complete these important tasks and blogs one class day in advance to confirm the completion of tasks within the timeframe.

Fig.24 Gantt Chart pt1

Fig.25 Gantt Chart pt2

Fig.26 Gantt Chart pt.3

Burndown Chart

Fig.27 Burndown Chart

At the start of the semester, our team was quick and productive in submitting material and doing research for the project. Initially, the number of tasks was low and amount of time was high thus, we were more productive compared to the actual workload that was given. As the weeks passed our team fell behind as other classes also increased in workload. The increase of work, unfortunately, caused our group to fall behind on assignments that resulted in our group to work overtime during the spring break. This inrush of productivity allowed our team to regain a proper schedule by the end of our spring break.

Now that we are approaching the end of the semester we are tasked to meeting tough deadlines and yet again when looking at the breakdown chart we can see have more stuff to work on compared to the time that we have.  At this time our group has developed a mutual consensus that we need to increase our productivity and work together for the success of our robot.

Summary of Experiments done / Rapid Prototyping Completed

By: Miguel Gonzalez (Project Manager & Manufacture)

It has been approximately eight weeks since the start of the semester and most of the first month consisted of mainly research and write-ups. But after the first month, we began experimenting with small components and sections of our BiPed. We started by looking at the legs of our robot as we knew that making the robot walk on two legs was a crucial part of our design. We created a copy of the 2016 Fall ROFI design and just focused on the legs of that robot. This initial design consisted of having 6 servo motors operating the leg and foot. Using the blog post on that robot and using help from projectbiped.com we were quick to get the robot’s leg to move. If you would like to see images and videos of the robot when it’s operating, you can view our drive folder here. In this configuration, the robot’s leg is very robust and can do very intricate movements while maintaining the robots balance. The issue with this design is that nearly 70 percent of all the weight of the robot consists of the legs alone. We knew that if we can decrease the weight on the robot we could have easier walking movements that in theory can speed up its walking speed. Our secondary design for the robot was to reduce the number of servos operating on the legs by only having four servo motors instead of six.

Fig.28 ROFI vs FOBO

Fig.29 Original Size vs Micro Size

This newer design would remove both the knee servo and middle leg servo on both legs. Theoretically, the newer design should remain functional and provide the ability to take longer strides when walking. It is important to note that the designs for the new leg designs have been modeled and 3D printed but the test will take place on March 17, 2018. This experiment will allow us to verify that the legs can perform walking movement and maintain a higher walking speed than the six-servo design.

Spring 2018: BiPed Preliminary Budget

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By: Miguel Gonzalez (Project Manager & Manufacturing)

Approved by: Miguel Garcia (Quality Assurance)

updated: 4/29/2018

Related Requirement

L1-10: Micro FOBO shall not exceed a cost of $250 to construct.

Objective

Project BiPed is one of this semesters robot production division in which a bipedal robot will be designed, engineered, and produced by the end of the semester. One of the most important tasks of any project is to evaluate and determine the cost of production of said products. In this post, we will be looking at the estimated cost of producing the BiPed robot. These costs will solely rely on physical component cost and any design and research development cost will not be mentioned in this post.

As part of the requirements stated by the customer, a budget was set for each project divisions. This is a loosely budget of $250 in which all material bought can be reimbursed in full. Any additional items and/or services that exceeded this budget will be covered by the team members working on the project. To help reduce costs, the customer has allowed access to his lab stock inventory of electronics, hardware, and materials. Borrowed items will be included in the budget table but the costs of the items will not be included in the total money spent.

Fig.1 Spring 2018 BiPed Budget Table

Budget Table (for access to links found on the table)

Summary

The above table shows the cost of components we have used and purchased as of April 18, 2018. The budget table above is divided into ten separate columns indicating important information about the used and purchased products. In the left column are the names of the parts and items used by the team to produce the biped robot. To the right of the parts column, is a link section that allows viewers to find the same parts we used for this project online. The table is also set up for invoice collection for any items that were purchased these invoices/receipts are linked on the second column to the right of the table. The budget table tries to incorporate all useful information that may be needed for future part purchases, replacement of parts, and for reimbursements.

Overall, we wanted to make sure not to spend any unnecessary money and to reuse as many electrical components and hardware as we could. It is important to note that some additions to the table will be made as the project continues and more items are needed. Multiple hours of reading past blogs as well as research were done to reduce unnecessary consumption of resources and to allocate as much possible reused parts from previous semester projects. Our total expenditures as of April 18, 2018, is a grand total of $226.54 which is under the customer’s project funding of $250.

References

  1. https://www.arxterra.com/wp-content/uploads/2018/04/Budget-Table.pdf

Spring 2018: Biped Mass Report

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By: Jeffery De La Cruz (Mission, Systems, and Test Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Approved by: Miguel Garcia (Quality Assurance)

Fig.1 Mass Report

The total mass of the Micro FOBO is at around 351.5 grams. This mass consists of the following:

  • Part 0: Hip Bracket x1
  • Part 1: Foot x2
  • Part 2: Servo Band x4
  • Part 3: Servo Bracket x2
  • Part 4: Servo Wrap x2
  • Part 5: Bearing Frame x1
  • Part 6: Body Riser x1
  • Part 7: Electronics Frame x1
  • Part 8: Head Compartment x1
  • Micro Servos x8
  • Samsung ICR18650 x1
  • Arduino UNO x1
  • Servo Shield x1
  • Ultrasonic HC-SR04 x1

To view the excel file of the mass report, click here.

 

The mass of the Micro FOBO will change because the material used to print the parts of the Micro FOBO will change from regular PLA to carbon fiber PLA. The Micro FOBO will become just lighter but not by much. The mass of the Arduino UNO and servo shield is included at the moment but will be updated once the 3DoT Board of the Sparkfun Pro Micro 3.3V/8MHz is included. Also, the battery case was not included because the position of the battery is to be determined.

References

  1. https://drive.google.com/open?id=1d0iSAl9_i4ClQRSkrW_wMS650_uzvDZU

Spring 2018: Updated Prototype Fritzing Diagram

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By: Jorge Hernandez (Electronic & Controls Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Approved by: Miguel Garcia (Quality Assurance)

Fig.1 Updated Prototype Fritzing Diagram

This is an updated Fritzing diagram, especially for Micro Fobo. A PCA9865 servo expander was used because we need to drive 8 micro servos and this expander breakout board lets us use up to 16 micro servos if needed. We only need 8 and that is why 8 headers are empty as they are not needed. A TCS9648A multiplexer board was used as we are using 2 UV’s and they will need different addresses If we want to gather information from them individually. This multiplexer board allows us to have 8 of the same sensor all with different addresses but we will only be using 2. We also have an external power source that will be connected directly to the Ultrasonic that is connected to the Pro Micro. The external power source is also connected to the servo expander and the micro servos will need much more than just 3.3V that is provided from the pro-Micro to run.

References

  1. https://www.arxterra.com/spring-2016-rofi-pcb-design-alternative-arduinos-and-custom-eagle-components/

Spring 2018: BiPed Planning and Schedule

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By: Miguel Gonzalez (Project Manager & Manufacture)

Approved by: Miguel Garcia (Quality Assurance)

updated: 4/21/2018

Objective

The objective of this post is to implement organization for the overall schedule of our BiPed project. This schedule is comprehensive and accounts for all tasks that should be completed by the displayed due dates. Using Project Libre, we can list the tasks needed to have a successful project. By using the Gantt chart feature we can see the tasks in a much more comprehensive chart that clearly demonstrates time frames and work periods. All tasks and due dates listed were imported from our class task matrix.

Overall Goal

Of course, like any project, our goal for BiPed robot is to finish every task on time while meeting our initial level one and level two requirements. To succeed, the following Gantt Chart was created with very precise timelines and due dates for procedural tasks that must be met to succeed in completing the BiPed robot on time. When creating the Gantt Chart, we notice three major tasks that are important to the success of the project. These tasks were the general project plan, finalization of the 3D model, and the final blog post. The deadlines for these tasks are March 15th, April 12, and May 8th in that order. Because the completion of these tasks is important we made sure to leave time after deadlines for adjustment and revisions. It is allowable to miss a deadline for tasks, but a penalty exists that increases as time passes. To prevent loss of points, additional precautions were put in place. As a group, we set the goal to complete these important tasks and blogs one class day in advance to confirm the completion of tasks within the timeframe.

 

Fig.1 Gantt Chart pt1

Fig.2 Gantt Chart pt2

Fig.3 Gantt Chart pt3

Burndown Chart

Fig.4 Burndown Chart

At the start of the semester, our team was quick and productive in submitting material and doing research for the project. Initially, the number of tasks was low and amount of time was high thus, we were more productive compared to the actual workload that was given. As the weeks passed our team fell behind as other classes also increased in workload. The increase of work, unfortunately, caused our group to fall behind on assignments that resulted in our group to work overtime during the spring break. This inrush of productivity allowed our team to regain a proper schedule by the end of our spring break.

Now that we are approaching the end of the semester we are tasked to meeting tough deadlines and yet again when looking at the breakdown chart we can see have more stuff to work on compared to the time that we have.  At this time our group has developed a mutual consensus that we need to increase our productivity and work together for the success of our robot.

Spring 2018: Micro FOBO Mechanical Designs

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By: Miguel Gonzalez (Project Manager & Manufacturing)

Approved by: Miguel Garcia (Quality Assurance)

Table of Contents

Notice

In this blog post, you will learn about initial mechanical designs for the Micro FOBO. We will discuss our thought process for each design component and relate it back to the customer’s requirements. Note that this the first post for the mechanical drawings of the miniaturized FOBO design created by Jonathan Dowdall. New advances in construction and design of the robot will be updated in a future post and linked at the bottom of this page. It is important to note the models shown in this post have yet to be physically tested. But plans to 3D print them have been made and the parts will be tested together. All results will be posted in a follow-up update blog post detailing our results of the models introduced here.

Introduction

The ROFI and FOBO bipeds can be considered as aging robots in which the designs have been used in many occasion for EE 400D projects. This can be particularly helpful if new students like ourselves would like to make such robots, considering resources for these models are plentiful on Arxterra.com. Unlike previous semesters our biped design will not encapsulate the same model but instead be a miniaturized version of those robots. Our group will particularly focus on the FOBO design by Jonathan Dowdall which is found on projectbiped.com. The miniaturized FOBO will be much smaller than the original approximately 60 percent its size and be controlled via micro servos (SG90S). We hope that in miniaturizing the design we can achieve a more efficient way of making the robot walk, turn, and avoid obstacles; all which are some design criteria for the maze.

Related Requirements

Level One Requirements

L1-3: Micro FOBO will have 2 legs.

L1-4: Micro FOBO will be a toy robot based on the design of the FOBO by Jonathan Dowdall.

L1-11: Micro FOBO shall be 60% or less of the overall size of Jonathan Dowdall’s FOBO

Level Two Requirements

L2-2: Micro FOBO dimensions will need to be small enough to fit in a 4in by 4in box for maze purposes.

L2-14: Micro FOBO shall measure within 4.5” x 3.25” x 7.25”.

Micro FOBO Design

For some clarification and for better understanding our design of the Micro FOBO, I have created a color-coded assembly of the robot with matching titles indicating the names of each component. Below I discuss the design of these components that make up the Micro FOBO.

 

Fig.1 Micro FOBO Colored Parts

As you can see from the image above, the Micro FOBO consist of 9 different parts: Servo Hip, Foot, Servo Band, Servo Bracket, Servo Wrap, Bearing Frame, Body Riser, Electronics Frame, and the Head. Note that Micro FOBO can be made up of multiple copies of the same part component and thus colored coded with the same color. For example, there are four servo bands in Micro FOBO which are shown in light green on the picture. Now that we know which parts make up the robot we can begin looking at the design of each part individually.

Part 0: Servo Hip

Fig.2 Servo Hip

The “Servo Hip” component of the Micro FOBO is responsible for attaching the two upper micro servos which are the hip servos. This bracket connects both servos (right and left legs) together to act as a hip bone that allows the robot to move its legs left to right. The connection to the servos is made via servo horns that are provided by the manufacturer. This part has two allocated trenches that match the dimensions of the servo horns allowing the servos to mount to the part. The horns are then screwed onto the servo hip using M2.5 screws that are 8mm in length.

Drawing File

Part 1: Foot

Fig.3 Foot

The “Foot” component is the same for both legs and is a simple shoe like design with wide pads on its sides. The extra material on the sides allows a greater amount of surface to touch the floor allowing the robot to balance easier. Currently, this part is in its simplified state as there is not much detail design put on it. This is because the team plans on mounting UV sensors onto the bottom of the foot where the hole is located. This would allow the sensor to be as close to the ground as possible to maintain an accurate reading. Once we receive the sensor additional design changes will be made to this part. Currently, the part allows the ankle servo, which is the servo closest to the ground, to be mounted onto one side of the foot though servo horn cutouts. The horn cutout is located on the inside wall of the part. The hole then allows an M2.5 X8 screw to secure the servo onto the foot piece.

Drawing File

Part 2: Servo Band

Fig. 4 Servo Band

There is a total of four “Servo Bands” located on the Micro FOBO. This part is responsible for grouping two micro servos together which forms a section of a leg. The two servos are pressure fitted into the square cutout and thus this part must be dimensionally precise to prevent servos to come loose. This piece had several revisions to satisfy the dimensional accuracy need to keep the servos secure. The servos were measured with a caliper and the thickness of the servos stickers even had to be considered when designing this piece. Due to leg movement constraints, only one servo can have extra material to be screwed onto the part.

Drawing File

Part 3: Servo Bracket

Fig.5 Servo Bracket

The ‘Servo Bracket” is a shorter version of part 0: servo hip and serves a similar purpose. This component mounts onto two servos that are located on the servo bands. This allows the second to the top servo to move the lower leg. This piece is located in the middle of the leg and connects the top and lower sections. This piece can be thought as the knee of the robot. Just like the other brackets, there are two cutout trenches that allow servo horns to be mounted and secured through a single screw. This piece can be varied in length to adjust the height of the robot and adjust the walking stride of the robot itself.

Drawing File

Part 4: Servo Wrap

Fig.6 Servo Wrap

The “Servo Wrap” is a small piece that attaches the back of the hip servo (top leg servo) to be mounted onto part 5: Bearing Frame. It is connected via an M2 screw that is 18mm in length. The screw goes through the servo, through the servo band, and screws into this piece. A hole on the left side of the wall was added to allow the servo wires to feed through and connect back to the electronics. Notice there is a hexagon trench located near the middle of the part. This trench allows an M3 nut to be placed in that location and lets a screw to secure Part 4 with Part 5. Another key design feature is the chamfer cutout located on the backside of the part. This permits higher degrees of movement from the hip servos by at least 45 degrees more.

Drawing File

Part 5: Bearing Frame

Fig.7 Bearing Frame

The “Bearing Frame” is a mirror-like component to part 0 as both pieces work together to provide the connection of legs to body. One of the key differences is that this piece contains two large circular trenches in which a bearing can fit onto. Using a 10mm circular bearing we place it on the part to provide free angular movement to the left and right sides of the pieces. Once the bearings are fitted inside, we can use M3X14 bolts to attach the servo wrap pieces to the left and right side of the Bearing Frame. Since the legs servos are already attached to the servo wrap we effectively attached the two legs to the body of the robot.

Drawing File

Part 6: Body Riser

Fig.8 Body Riser

Micro FOBO mainly consists of a head and two legs but this part, body riser, can be considered the body of the robot. This component connects the two attached legs with the head. There are two fork-like structures located at the top of the piece that allows part 0 and part 5 to fit in snugly effectively connecting the two legs to this piece. Part 0 and part 6 are secured through a couple of M3 screws with an approximate length of 16 mm. The back side of this component is flat and has two holes for connecting to part 7 which is the electronics frame. The body riser can be increased in height allowing the robot’s head to be located higher above the legs. We can experiment with changing the height to allow shifting the robot’s center of mass higher or lower as needed.

Drawing File

Part 7: Electronics Frame

Fig.9 Electronics Frame

The Electronics Frame is a thin component that is responsible for connecting the PCB to the body riser. The PCB will contain four mounting holes which will allow the board to connect to this part. Note that the part contains extruded cubes that correspond to the location of the PCB hole mounts. These extruded cubes also have a hole cut out to fit M3 screws that secure the board in place. Finally, the part can be secured to the head via similar M3 screws on the side of the part and head

Drawing File

Part 8: Head

Fig.10 Head

One of the first challenges in creating a miniature FOBO we observed was that our robot would need to support large amounts of electronic components that used to be on the regular size FOBO. These electronics would need to be smaller in size or our head design would need to optimize to fit all the electronics. Our first design was based on the prediction that the new electronics would have a smaller footprint and thus the head of the Micro FOBO is much smaller. The exact dimensions can be found on the link below. Once the size of the head was set I began to look at some redesigns that I can implement to change the look and functionality of the robot’s head. That is when I stumbled on an image of a tin toy robot from the 1950s.

Fig.11 1950’s Tin Toy

As you can see from the image above this robot has a similar head as the FOBO which gave me the idea of emulating the design of the face. The ultrasonic sensor will take place as the robot’s eyes and the mouth and nose features would simply be aesthetics. Another thing that I noticed was that the tin toy contained antennas on the left and right side of the head. One of the redesigns I wanted to incorporate since the beginning was adding turn signals to the robot and the antennas can certainly be used for that. My idea is to have small 5mm red LED’s as the tip of the antennas that would blink indicating when the robot will turn and in what direction. Finally, we see that there is a small red light on top of the robot that can be designed to indicate on/off status of the robot.

Fig.12 Mechanical Design Improvements

Drawing File        Tin Robot Toy

 

Spring 2018 3DoT Hexy: System Block Diagram

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By: Raymundo Lopez-Santiago (Mission System and Test)

Verified by: Eduardo De La Cruz (Project Manager and Manufacturing Engineer)

Approved by: Miguel Garcia (Quality Assurance)

Table of Contents

Introduction

This blog post covers 3DoT Hexy’s System Block Diagram. The 3DoT Hexy robot along with all its peripherals will be powered from a single 3.6V RCR123A battery. The 3DoT board will connect to all other devices. The 3DoT board comes equipped with a BLE Bluetooth module, Dual DC motor driver and (3) 8-pin connections to attach peripherals. Communication for mobile operation of 3DoT Hexy will be done using a BLE Bluetooth module which will be paired to the ArxRobot application. Two separate custom PCBs will be designed and sent for fabrication. The custom sensor PCB will have an I2C expander which will incorporate all sensors which include the color, ultrasonic, and light sensor. The custom Boost Converter PCB to provide 5V to the micro metal motors used to drive the gears/cam-system as well as three UV LEDs. Fig. 1 shows the system block diagram for 3DoT Hexy.

Update 04/17/18

Due to changes in the maze printing material and the fact that we are no longer using a boost converter, the UV LEDs will no longer be used and instead IR LEDs along with Light sensors will be used to handle intersection detection. Another change that is noticeable is instead of using an 8-channel I2C expander, we are now using a 4-channel I2C expander. The color sensor was removed from the design since we are using light sensors for intersection detection. A new addition to the design is the use of a gyroscope to aid in directional turning and two LEDs to act as eyes of the spider robot. The interface matrix was updated to reflect changes. Fig. 2 shows the updated system block diagram for 3DoT Hexy. Only 8-pins from the bottom shield of the 3DoT board will be used.

Fig. 1: 3DoT Hexy Updated System Block Diagram

 

 

Preliminary System Block Diagram (03/15/18)

The system block diagram mimics the interface matrix developed for 3DoT Hexy. The 3DoT Hexy system block diagram below shows the different parts of the robot and how they interact with each other. A total of 9 pins out of the 16 pins available from the 3DoT board will be used for the custom PCB’s. The two custom PCB’s will be designed and built to add an I2C expander which will connect to all sensors, also a boost converter to provide 5V to the motor driver. 3DoT Hexy will be powered from a single 3.6V RCR123A battery. Communication for mobile operation of 3DoT Hexy will be done using the HM-11 bluetooth module. Any changes will be added as needed.

 

Fig. 2: 3DoT Hexy System Block Diagram

 

Conclusion

The system block diagram is designed taking in consideration of the 3DoT board as the main board to control any attached devices. Visually the system block diagram helps identify connections between devices and how many pins will be allocated or needed. The interface matrix and system block diagram were developed around the same time. I highly recommend to pair these two tasks very close to each other.

References

  1. https://www.arxterra.com/2016-spring-3dot-david-final-project-blog-post/
  2. https://www.arxterra.com/spring-2018-3dot-hexy-interface-matrix/

Spring 2018 3DoT Hexy: Product Breakdown Schedule

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By: Raymundo Lopez-Santiago (Mission, System and Test)

Verified by: Eduardo De La Cruz (Project Manager and Manufacturing Engineer)

Approved by: Miguel Garcia (Quality Assurance)

Introduction

This blog post covers the Product Breakdown Schedule (PBS) for 3DoT Hexy. This document follows the Work Breakdown Schedule (WBS) developed by Eduardo De La Cruz (Project Manager and Manufacturing Engineer). This PBS is split into five sections to outline the major components of 3DoT Hexy. The five sections are electronic hardware, software, movement, manufacturing, and power. Anything for movement which includes motors, joints, gears, and legs are the main parts in for mobility of the robot. Under the software section, communication via Bluetooth from a smartphone and the Arxterra app will allow for wireless control of 3DoT Hexy with custom commands. For electronic hardware, all peripheral sensors will be connected to a custom PCB.  Sensors used for this project include three UV light sensors which will aid in detecting intersections, an ultrasonic sensor which will aid in detecting other robots, and a gyroscope to aid in directional turning. For manufacturing, it includes designing a cam system. chassis, legs, joints and any other parts used for the mechanism. It also includes rendering models on Solidworks and 3D printing parts in either PLA/ABS plastic or other approved material. For the power section, 3DoT Hexy and its peripherals will be powered by a single 3.6V RCR123A battery. Power estimates of each components are further listed in the resource reports blog post.

Fig. 1: 3DoT Hexy Product Breakdown Structure

 

Conclusion

After going through two revisions after the PDR, I made sure this PBS was effective in following the WBS. For future reference, make sure to only define major components for the robot and not specific details. Do not try to go to a different path than the WBS, since the overall objective is to identify major components and who is responsible for them to further help with the production of the final product.

References

  1. https://www.arxterra.com/2016-spring-3dot-david-final-project-blog-post/
  2. https://docs.google.com/document/d/18vVkXfxwqulRn5qCdm2Y6NYleS1iGQ_p3y6FJUj5NJ4/edit

 

Spring 2018 3DoT Hexy: Interface Matrix

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By: Raymundo Lopez-Santiago (Mission, Systems, and Test)

Verified by: Eduardo De La Cruz (Project Manager and Manufacturing Engineer)

Approved by: Miguel Garcia (Quality Assurance)

Table of Contents

Introduction

This blog post covers 3DoT Hexy’s final interface matrix. If interested in seeing our preliminary design interface matrix click here. The 3DoT Hexy interface matrix was developed with information obtained from datasheets for each device used and pins allocated from the 3DoT V 6.43a board. Based on our design, we needed to design two custom PCBs, one for all sensors and one with a boost converter to drive our motors as well as power three UV LEDs. To make things easy to understand, the interface matrix is broken up into three interface matrices. As seen in Fig. 1, the main interface matrix relates each custom PCB to the 3DoT board and how each PCB will connect to the 3DoT board. As seen in Fig. 2, the Custom Sensor PCB interface matric further breaks down in detail which sensors will connect to the PCB to make sure no pins are used more than once (except for power and ground). As seen in Fig. 3, the Custom Boost Converter PCB also breaks down in detail which peripherals will connect to the PCB to make sure no pins are used more than once (except for power and ground). After researching different UV sensors, we were unable to find ones that had different I2C addresses, therefore we needed to add an I2C expander to our circuit design. Based on availability and previous semester success, the model I2C expander model used is TCA9548A. The boost converter model used is TPS61253A.  The Light Sensor (UV Index Sensor) model used is Si1145. The gyroscope model used is ITG-3200. The Ultrasonic sensor model used is Parallax Ping (a HC-SR04 may also be used).

Related Requirements

Level 1 Requirements

L1-4:

The robot shall have a custom PCB as platform to build from and will incorporate peripherals for sensors

C-12:

The robot shall use a v6.43a 3DoT board.

Level 2 Requirements

L2-2:

The robot shall use a single RCR123A 3.7 V, 650mA rechargeable Li-ion battery to power the 3DoT board, which will power the drivetrain and all attached peripherals.

L2-3:

The robot shall use three Light sensors and three IR LEDs connected to a custom sensor PCB to handle intersection detection.

L2-4:

The robot shall use a Parallax Ping (or HC-SR04) ultrasonic sensor to handle robot avoidance.

L2-10:

The robot shall have (2) LEDs acting as eyes of the spider.

 

Update 04/24/18

Based on customer concerns with the TPS61253A 9-ball 1.2-mm x 1.3-mm WCSP package, we explored other methods to not use a boost converter and further investigate operating all electronics of the robot at the rated 3.7 V from the RCR123A battery. After improving the gear mechanism with the addition of bearings and bushings, we were able to operate the robot at 3.7V while having stable movement with weight attached on top of the robot (simulating the final weight of all devices used for the final robot configuration). Since this change occurred, we no longer will use any connections from J1 and J2 from the 3DoT board. UV LEDs will no longer be used and will be replaced with IR LEDs. Based on customer recommendation instead of using the 8-channel TCA9548A I2C model, we are going to use a 4-channel model: PCA9544A. All peripheral devices will be connected to the Custom Sensor PCB developed by Kris Osuna (Electronics and Control Engineer). The Custom Sensor PCB is connected to J3 of the 3DoT board.  Two additional extra LEDs are added to act as eyes of the spider.

 

Fig. 1: 3DoT Hexy Interface Matrix

Fig. 2: Custom Sensor PCB Interface Matrix

Fig. 3: Custom Boost Converter PCB Interface Matrix

Conclusion

This blog post covers 3DoT Hexy’s interface matrix. This matrix is composed of the available pins of the 3DoT V 6.43a board and how they connect to each custom PCB. When using the Custom Boost PCB conected to the 3DoT board, Make sure to remove JP7 on the 3DoT board. This will avoid you messing up the 3DoT board. The objective of this document is to allocate pins to components used in the design and make sure no pin is used twice (except power and ground).

References

  1. https://www.arxterra.com/2016-spring-3dot-david-final-project-blog-post/
  2. http://www.ti.com/lit/ds/symlink/tps61253a.pdf
  3. http://www.ti.com/lit/ds/symlink/pca9544a.pdf
  4. https://cdn-shop.adafruit.com/datasheets/Si1145-46-47.pdf
  5. https://www.sparkfun.com/datasheets/Sensors/Gyro/PS-ITG-3200-00-01.4.pdf
  6. https://cdn.sparkfun.com/datasheets/Sensors/Proximity/HCSR04.pdf