Preliminary Detailed Design

Team Vision for Preliminary Detailed Design Phase

Summarize:

• What did your team plan to do during this phase?
  • Preliminary bill of materials
  • Prototypes of paper securing system, gripper and belt system
  • Test plans written
  • Subsystem drawings
  • Subsystem flowcharts
  • Well written documentation, up-to-date Gantt chart and risk management.
• What did your team actually accomplish during this phase?
  • Subsystem drawings
  • Subsystem flowcharts
  • Prototypes of tool change array
  • Draft test plans
  • Preliminary bill of materials
  • 3D CAD models of the mechanical subsystems
  • Well written documentation, up-to-date Gantt chart and risk management.

System Architecture

                                                             Preliminary 3D model of the Robotic Art Assist

User Interface Subsystem

Microcontroller Configuration

1. 3 microcontrollers (1 for student input, 1 for teacher input, 1 for device)
   1. Student Input
      • Arduino
      • Teensy
      • Low power
      • need bluetooth
   2. Teacher Input
      • Need screen output
      • raspberry pi
      • need bluetooth
   3. Device
      • Need bluetooth
      • need many pins
      • Arduino
      • Raspberry pi
2. 2 microcontrollers (1 for student input, 1 for teacher input and device)
   1. Student Input
      • Arduino
      • Teensy
      • Low power
      • need bluetooth
   2. Teacher Input and device
      • Need bluetooth
      • need screen output
      • need many pins
      • Raspberry pi
3. 1 microcontroller
   • Need many pins
   • need screen output
   • Raspberry pi

Team decided to plan on using 2 microcontrollers, with the possibility of 3 if the control requires extra pins

Determination of Programming language

Python was chosen as the programming language for the teacher input as it is the most familiar and would be the easiest to work with.

C was chosen as the programming language for the student input as it can run on arduinos and teensys and allows for low power and fast execution.

Design of Teacher Input Screen

The teacher input screen was designed to allow the teacher to be able to remotely control the device along with the student, stop the student from being able to control the device if necessary, input the size of drawing area, and select tools for drawing. The design can be seen below:

Student Input Parts

Buttons:

• Adafruit arcade buttons
  
  • https://www.adafruit.com/category/757
  • 60mm-100mm
  • $5.95-$9.95
  • Colors
    • White
    • Green
    • Red
    • Blue
    • Yellow
• Sparkfun buttons
  • https://www.sparkfun.com/categories/313
  • 100mm
  • $11.95
  • Colors
    • Red
    • Green
    • Blue
    • Yellow

Joystick

• Sparkfun Arcade Joystick - Short Handle
  • https://www.sparkfun.com/products/9182
  • $16.95
  • 4 direction
  • 4 switch output
  • Top can be removed
• Sparkfun Arcade Joystick
  • https://www.sparkfun.com/products/9136
  • $19.95
  • 4 direction with top button
  • 5 switch output
• Adafruit small arcade joystick
  • https://www.adafruit.com/product/480
  • $14.95
  • 8 direction
  • 4 switch output
  • Top can be removed

Microcontroller

• Arduino Nano 33 IoT
  • Has Bluetooth and Bluetooth low energy connectivity
  • Input voltage of 3.3V
  • 14 pins
  • Sparkfun ($24.95)
    • https://www.sparkfun.com/products/15589
  • Mouser ($20.25)
    • https://www.mouser.com/ProductDetail/Arduino/ABX00027?qs=PzGy0jfpSMvleC8D9q4oLA%3D%3D
  • Jameco ($19.95)
    
    • https://www.jameco.com/z/ABX00027-Arduino-Arduino-Nano-33-IoT-without-Headers_2304695.html
  • Digi-Key ($21.55)
    • https://www.digikey.com/en/products/detail/arduino/ABX00027/10239968

Student Input Options

Updated Microcontroller Benchmarking

The microcontroller benchmarking from the previous phase was trimmed down to focus on the most important features to better facilitate choosing which microcontroller to control each of the subsystems. The main features being looked into were Bluetooth connectivity, low power, high number of I/O pins, and a display port.

	Arduino Due	Arduino Nano	Raspberry pi 4B	Teensy 4.1
Size	101.52mm x 53.3mm	45mm x 18 mm	85.60mm x 56mm	60.96mm x 17.78 mm
Weight	36g	5g	45g	11g
Price	$40.30	$18.40	$35.00	$26.85
Input Pins	54 Digital I/O, 12 Analog	14 digital I/O, 8 Analog	40 pin GPIO header	55 digital IO pins,  18 analog input pins
Output pins	54 Digital I/O, 2 Analog	14 digital I/O, 1 Analog	40 pin GPIO header	55 digital IO pins, 35 PWM output pins
Programming Language	Arduino C	Arduino C	C, C++, Python, etc	C, C++
Power	7-12V Input, 3.3V/5V Operating, 800mA per pin	3.3V, 7mA per I/O pin	5V DC via USB-C connector/GPIO header (min 3A)	5V Vin, 3.3V out
Clock speed	84MHz	48MHz	1.5MHz	600 MHz
Ports	MircoUSB, 4 UARTs	1 UART, 1 USB port	USB-C, 2 USB 2.0, 2 USB 3.0 ports, 2 Micro HDMI Ports	USB Host, FlexIO (includes UART)
Comments	High Price. Requires higher input voltage. Fairly fast. UARTs could be used for Bluetooth	Cheap. Few I/O ports. Has Bluetooth connectivity	Relatively slow. Comes with Python (convenient). Has Bluetooth connectivity. HDMI ports included (for display). Heaviest	Relatively fast. UARTs could be used for Bluetooth. A lot of I/O pins
Link	Arduino Due	Arduino Nano	Raspberry Pi 4B	Teensy 4.1

Block Diagram of User Interface

Motor Subsystem

Initial Motor Specification Requirements

Motor Benchmarking:

Control Subsystem

Benchmark encoders

Magnetic encoders would require a 2 pole round magnet. Since steppers are being used, encoders are not needed.

Benchmark stepper drivers

Control Subsystem schematic

Power Subsystem

Power Analysis

The device will be split into two power subsystems. One for the user interface and one for the device and aid input; the systems will be powered separately. 

Live document found here.

Battery Options

The user interface will be powered by a small rechargeable battery. The device will either be powered by a larger rechargeable battery or plugged into the school outlets. To use the AC power from the school we'll need an ACDC converter (https://www.digikey.com/en/products/detail/mean-well-usa-inc/LRS-150-12/7705011?s=N4IgTCBcDaIDYCcDOBaAjAVgAzogXQF8g).

Power Block Diagram

Live document here. The Raspberry Pi will use the standard Raspberry Pi power supply to ensure the voltage is regulated at 5V properly. This eliminates the need for a voltage regulator within the circuit. The Motors and Servos will run off power from an AC/DC converter. The AC/DC converter and Pi will be plugged into a power strip with serge protection. The power strip will have a long enough cord that it can be plugged into the wall without the cord elevating from the ground. The Arduino Nano for the user interface will be connected to a separate 3.7V rechargeable lithium ion battery.

Gripper Subsystem

GrabCAD Links for Two-Finger Gripper: 

https://grabcad.com/library/two-finger-gripper-1 

https://grabcad.com/library/robotic-gripper-17

Preliminary 3D Model

The vertical servo powers the geared gripper jaws to open and close around the tool, while the horizontal servo controls the angle of the subassembly to raise or lower the tool onto the paper.

Automatic Utensil Changer

There are two main ways to automatically pickup the tool, a carrier and a gripper. The two options were compared and the team decided to pursue 

Gripper	Carrier
PRO	PRO
Gripper will adjust to different tool sizes	The device doesn't have to open and close to grasp a tool → the carrier connection picked up by the device is the same and more stable regardless of the tool
Gripper is purchased off the shelf → easy to purchase and a attach a new one if it breaks	Carrier would be designed to accommodate all utensil sides needed
Tool Holder Array allows for easier utensil addition mid drawing
Easier and shorter setup time
CON	CON
Tool size limited by selected gripper opening	Carrier would be custom designed → harder to repair over product lifetime
Gripper will be grabbing a different sized tool each time, will need to ensure utensils	Need many carriers to support an automatic utensil change
	If a student wanted to use more colors than carriers, a carrier's drawing utensil would need to be changed out which could take longer
	Longer set-up time
LINK	LINK
http://svenhb.bplaced.net/?CNC___Plotter_2___Greifer	http://www.doublejumpelectric.com/projects/toolchanging_pen_plotter/2019-03-17-toolchanging_pen_plotter/

Automatic Tool Changer Process

Belt Subsystem

Paper Holding Subsystem

Rubber used for the "restaurant ticket holder" device

https://www.mcmaster.com/8466K13-8466K143/

Mechanical Subsystem

Wheel Chair Attachment 

Framework 

The framework for the machine consists of 8020 aluminum extrusion sides with a rail slider system to change the X Y position of the utensil.

Bill of Material (BOM)

Preliminary BOM

The live document is found here.

Test Plans

System Design and Flowcharts/System Block Diagram

                                                             Preliminary 3D model of the Robotic Art Assist

High Level System Block Diagram

Risk Assessment

Design Review Materials

Preliminary Detailed Design Review Notes & Actions

Plans for next phase

• Finalized design of system
• Finalized bill of materials
• User interface components ordered
• Test Plans written

Individual plans

• Andrew Pasek
• John Owens
• Allison Morgan