P17421: Robocomposter 2.0
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Systems Design

Team Vision for System-Level Design Phase

Goals and Initiatives:

Completed

With the goals above in mind prior to starting the systems design phase, there was a heavy focus on trying to determine the entire state of the Robocomposter to begin identifying areas that would need redesign, parts that would need to be purchased, and begin brainstorming a structure for controls integration. All deliverables were completed on time and are outlined in the sections below. Additionally, planning was done to coordinate efforts for programming and coding going forward so that controls and automation can be implemented before the final phases of MSDII. The mechanical components of the prototype were stripped off the platform and analyzed and the sensors were removed to determine their existing state. All documentation and analysis are outlined below in the Systems Design webpage.

Functional Decomposition

A functional decomposition was produced to determine all vital functions that the end product will be capable of performing. The functional decomposition starts with the overarching goal of producing compost and delivering more specific functions to achieve this goal as the tree branches down.

public/Photo Gallery/Functional Decompostion.png

public/Photo Gallery/Functional Decompostion.png

The link to the live document can be found here

Benchmarking

Although the hardware for the Robocomposter was solidified during the first prototype, it was thought to be worthwhile to benchmark in case there are any glaring improvements that could be made within the budget. To complete the benchmarking, the functional decomposition was utilized to break down the prototype into basic functions and then searching was utilized to benchmark technologies that could perform the objective better than what is currently on the prototype.

 Benchmarking Pictures

Benchmarking Pictures

 Benchmarking Pictures

Benchmarking Pictures

Concept Selection

To compare the system concept designs against one another, a number of criteria were brainstormed. The concepts were based off of the engineering requirements and customer requirements and are as follows:

  1. Safety of components
  2. Impact on composting speed
  3. Ability to maximize size
  4. Durability of components
  5. Feasibility of constructing the components
  6. Cost of the components
  7. Educational value of the components
  8. Ease of use of the components
  9. Portability of the system (i.e weight)

Morphological Chart and Concept Selection

Driven from the customer requirements, the functional decomposition, and the benchmarking that was performed, the functions of the Robocomposter were established and input into a Morphological table. The Morphological table was then utilized to produce a Pugh chart where the existing prototype was set as the datum. Even with the benchmarking and brainstorming that was performed, the prototype came out with the highest score.
 Morphological Table

Morphological Table

 Pugh Chart

Pugh Chart

Concept Development

 Concept 1: Feed Port

Concept 1: Feed Port

 Concept 2: Gearbox Cover

Concept 2: Gearbox Cover

Feasibility: Prototyping, Analysis, Simulation

To test whether the existing motor powering the shredder of the prototype is capable of delivering the required torque, a calculation needed to be conducted to determine the mechanical requirements. Since wood is generally taken as being the strongest material to pass through the shredder, it was used as a "worst case" for organic material that might pass through the shredder. Calculations for torque and power were conducted during the first iteration of the design and repurposed to ensure that the motor used was within spec. Since one of the biggest concerns is the ability of the motor to granulate the material to expedite the composting process,a check was performed as is shown below.

 Motor Speed Calculation

Motor Speed Calculation

 Motor Torque and Power Calculation

Motor Torque and Power Calculation

To ensure that the existing motor could supply the required torque, the spec sheet was obtained. The link to the spec here

The key specs listed on the OEM's webpage for this motor is that:

In order to determine if the sensors needed to be replaced they were evaluated for the operating conditions expected within the reaction chamber of the composter.

Sensor Feasibility

Sensor Feasibility

The datasheets and information for the sensors can be located

Ammonia Sensor Datasheet

CO2 Sensor Datasheet

Methane Sensor Information

Oxygen Sensor Datasheet

Temperature Sensor Datasheet

VH400 Soil Moisture Sensor Information

Power Calculations

Power Calculations

Motor connection feasibility

Motor connection feasibility

Motor connection feasibility

Motor connection feasibility

Simple sensor request walkthrough and implementation requirements.

Walkthrough

Implementation Requirements

Systems Architecture

System Architecture

System Architecture

Visio file for System Architecture

The system architecture consists of 7 individual subsystems, the user interface, the Raspberry Pi, the Arduino, the sensors, the motors, the motor drivers, and the power systems.

Designs and Flowcharts

Loading Compost Flow Chart

Loading Compost Flow Chart

Excel file for Loading Compost Flow Chart

Unloading Compost Flow Chart

Unloading Compost Flow Chart

Excel file for Unloading Compost Flow Chart

Data Handling Flow Chart

Data Handling Flow Chart

Excel file for Data Handling Flow Chart

Risk Assessment

Risk Assessment

Risk Assessment

Excel file for Risk Assessment Weeks 6-10

Preliminary Testing

Empirical testing of composting was started to determine a feasible goal for composted material. To do this, 5 gallon buckets were filled with compostable waste in varying recipes. The recipes were documented and every couple of days, metrics and observations were documented in the spreadsheet found here

Testing Batch A

Testing Batch A

Testing Batch B

Testing Batch B

Design Review Materials

Look here for sensor data

Plans for next phase

Plans For Next 3 Weeks

Plans For Next 3 Weeks

Plans for next phase excel sheet


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