For our Senior Design process, we made an effort to address and consider every detail to determine our final concept and product design. Our design process consists of five sub-processes, which are used to guide us to a final product.

Figure 1: Design Process

· 1. Problem Identification

Clearly identifying a problem is imperative for the design process because it is the root of the project. Determining the central issue of a certain subject can allow one to focus on that problem without deviating from it and allow one to develop a problem statement. [4]

Search Inventory

· 2. Problem Formulation

Clearly defining the problem is essential to the design process. This consists of finding and learning about the major and minor details of the problem subject to make well-educated decisions regarding the central issue. The methods of problem formulation include background research, research on competitive products, user research, and design specifications. [3]

· 3. Conceptual Design

A crucial aspect of the design process is to determine the functions of the product that are sought to solve the problem that is identified. Within these functions, solutions can be presented specifically to those functions and cohesively brought together into concept variants. From here, a final design can be determined based on qualitative or quantitative eliminations.

· 4. Embodiment Design

The embodiment process brings the final concept to life and requires using engineering aspects to tackle technical questions. The design specifications of the product itself are considered, and the final design is realized.

Tools

· 5. Testing and Validation

In this final sub-process, the final design is tested, evaluated, and optimized so that it can be used to effectively solve the problem identified. After testing and validation, the final product can be directly led to a higher level of production.

Clipboard Mixed

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PROBLEM IDENTIFICATION

Clearly identifying a problem is crucial for the design process because it is the root of the project. We, as a team, have decided to make an impact within our local community by tackling a problem introduced by mesquite farmers within Linn, Texas.

Product Opportunity Gap

Given the growing trend for healthier foods and products, there is a greater demand for mesquite beans. Because the main harvesting method of the mesquite industry is manual labor, which is very strenuous and time-consuming with minor results, there is a demand for a new and more efficient way for harvesting mesquite beans.

Value Opportunity Chart (VOA)

For our Product Opportunity Gap, we developed a Value Opportunity Chart (VOA), which directly compares Manual Labor to our prospective product. The purpose of these two graphs is to compare the ideal solution to that of the current workflow of the Cappadona Ranch.

Table 1: Value Opportunity Chart

Figure 2: Describing Our Value Opportunity Chart

Although our product would have these clear advantages over manual labor, our product would have a couple of drawbacks.

- The first drawback of our product would be that it would need proper training for operation. However, this is specific towards the safety of the user.

- The second drawback would be that our product may not be as effective as manual labor in their ability to access to hard-to-reach areas.

- Despite the drawbacks of the product, with safety being an upmost priority, the pros certainly outweigh the cons of manual labor, especially considering the safety hazards that the current field workers must go through every year during harvest season.

FINAL PROBLEM STATEMENT

Click the icon above to hear our Final Problem Statement!

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PROBLEM FORMULATION

Clearly defining the problem is essential to the design process. The methods of problem formulation include background research, research on competitive products, user research, and design specifications.

BACKGROUND RESEARCH

To better understand the context of the problem to solve, we conducted Background Research on the following topics:

All the sub-categories above are incredibly important when setting up the foundational work of the design process. With all of these in mind, we can use the knowledge gained towards conceptual design work.

To view our Background Research folder, view here.

COMPETITIVE PRODUCTS

To avoid “reinventing the wheel,” we looked at existing solutions and competitive products:

Much of the references that were looked at for competitive products were that in use for agriculture. For example, the hook as shown above is a Kadıoğlu Emr400 Branch Shaker Harvesting Machine. This mechanical hook is used for vibrational applications to branches and is one of the many competing products that were found during our research.

To view our Competitive Products folder, view here.

USER RESEARCH

Understanding the user wants and needs is key for the design of a valuable product, we applied a variety of User Research techniques for that purpose:

Technique #1: Stakeholder Map

Figure 3: Stakeholder Map

Our stakeholder map shows us the people and businesses that will be directly affected by the decisions made for our designs. To assist with understanding the user and the pains and gains of the business, we have conducted a personal interview between the team and the Cappadona family, which can be heard below.

Technique #2: Scenario Development

Click on the icon above to view our Scenario Development!

To view our Scenario Development document, view here.

Technique #3: Interview with the Cappadona’s

Click the icon above to hear the audio file from our interview with the Cappadonas!

To view our notes from our Interview with the Cappadonas, view here.

DESIGN SPECIFICATION

The Design Specification captures the “essence” of the design by showcasing the demands and wants of our users. The following table shows the Design Specifications for our project:

Table 2: Design Specification Table

Date Changed

Demand/Want

Requirement List for the Mesquite Bean Picker

Responsibility

2/18/2020

5/1/2020

3/3/2020

Geometry

Maximum Radius -- 24 ft.

Average Canopy Radius – 15 ft.

Telescoping Arm Extender - 6 ft - 12 ft.

Localized Collection (1/4^th of Canopy Area)

Vibration Interface – Meets Branch Perimeter

3/3/2020

Energy

Localized Vibration

Battery – 24 Volt Battery (Car Battery)

Gasoline/Motor

Rotational

Gravitational Freefall

Electric (for Vibration)

3/3/2020

Material

Heavy Duty Material for Tarpaulin

Aluminum Arm Extender

Steel Branch Interface

Aluminum Frame (Tarpaulin)

Aluminum Hopper

3/3/2020

Signals

Dial for Vibration Control

LED Light

LED Display

Sound for I/O of Vibration Interface

3/3/2020

Safety

No sharp blades

Remove the user from physically touching the tree due to thorns

Remove the need for standing on elevated height

3/3/2020

Ergonomics

Low profile to account for small canopy height

< 50-75 lb. to Maneuver the collection device

Can be easily pushed by physical effort

< 125 lb. for Easy Movement

Ease of Use

Handheld Vibration Machine

Costs

< $400 for the whole project

To view more details about our Design Specifications, view here.

Figure 4: Our Goal and Proposed Solution on a single PowerPoint slide

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CONCEPTUAL DESIGN

FUNCTIONAL DESIGN

Creating a Functional Diagram allows us to understand what the product needs to do but not necessarily how.

Figure 5: Functional Diagram

Although our Functional Diagram shows only one function, we decided to divide our project into two parts. One function for Picking Mesquite Beans and the other for Collecting Mesquite Beans. Each of these functions contain sub-functions within themselves.

MORPHOLOGICAL CHARTS AND SUB-FUNCTION CHARTS

The Morphological Chart helps us explore the universe of viable solutions for each function’s sub-function in an orderly fashion. The Sub-Function Chart helps us to decide on the best solution for the specific sub-function based on certain criteria.

Function #1: EXCITATION

Table 3: Excitation Morphological Chart

The Excitation function is broken down into six functions: Branch Interface, Power, Control, Motor, Method of Vibration, and Arm Extension.

Table 4: Excitation Subfunction Chart - Branch Interface

The Branch Interface requires connection between the machine and the branch to allow for constant vibration. This subfunction is comparing all its solutions to the following criteria: Ease of Use, Cost, Mobility, and Safety.

Table 5: Excitation Subfunction Chart - Power Supply

The second subfunction is the Power Supply. Its solutions will be compared using the following criteria: Ease of Use, Cost, Maneuverability, and Safety.

Table 6: Excitation Subfunction Chart - Control

Control is essential for both holding the vibration frequency and for connecting the machine together. Its solutions will be compared using the following criteria: Ease of Use, Cost, Maneuverability, and Safety.

Table 7: Excitation Subfunction Chart - Motor

The fourth subfunction is the Motor. Its solutions will be compared using the following criteria: Frequency Range, Size, and Programmability.

Table 8: Excitation Subfunction Chart - Method of Vibration

Method of Vibration is important because different mechanisms have different variables that are considered. The method that is applied will also affect the target vibration modes. Its solutions will be compared using the following criteria: Ease of Use and Maneuverability.

Table 9: Excitation Subfunction Chart - Arm Extension

Arm Extension allows the machine to reach into the higher points of the tree. Its solutions are evaluated with the following criteria: Weight, Cost, Maneuverability, and Safety

Function #2: COLLECTION

Table 10: Collection Morphological Chart

The Collection function is broken down into five sub-functions: Guiding Beans, Storage, Power, Method of Movement/Control of Beans, and Transportation.

Table 11: Collection Subfunction Chart - Guiding Beans

Guiding the beans requires that there be a location for beans to fall and allows for the guidance of the beans to the next step of the process. Its solutions will be evaluated through the following criteria: Ease of Use, Cost, Maneuverability, and Safety.

Table 12: Collection Subfunction Chart - Storage

Storage of the beans is the last step of the system. With the guidance of the bean to the storage selection, the beans reach their destination where the user can use the beans for the next step of their manufacturing process. Its solutions are evaluated with the following criteria: Ease of Use, Cost, Maneuverability, and Safety.

Table 13: Collection Subfunction Chart - Power

The third subfunction is Power. Its solutions are evaluated with the following criteria: Ease of Use, Cost, Maneuverability, and Safety.

Table 14: Collection Subfunction Chart - Method of Movement/Control of Beans

The fourth subfunction is Method of Movement/Control of Beans. Its solutions are evaluated with the following criteria: Ease of Use, Cost, Complexity, and Safety.

Table 15: Collection Subfunction Chart - Transportation

The fifth subfunction is Transportation. Its solutions are evaluated with the following criteria: Ease of Use, Cost, Maneuverability, and Safety.

CONCEPT VARIANTS AND SELECTION PROCESS

Combining all practical solutions would generate a factorial number of concept variants, we had to be selective to find the best ones. This is our Concept Variant Elimination Process:

Figure 6: Concept Variant Elimination Process

Function 1: EXCITATION

To begin our selection process, we set up a datum to compare our concept variants against each other. The concept variants are evaluated by the following criteria: Ease of Use (3 points), Durability (2 points), Maneuverability (2 points), Cost (1 point), and Manufacturability (1 point).

The three concept variants with the highest scores will survive the Primary Qualitative Elimination and move towards the Secondary Qualitative Elimination process.

Table 16: Primary Qualitative Elimination for Excitation

The top three concept variants are put through a secondary qualitative elimination process and evaluated by the following criteria: Method of Vibration (3 points), Arm Reach (2 points), and Surface Contact with Branch (1 point).

Table 17: Secondary Qualitative Elimination for Excitation

The highest scoring concept variant is the circular, extending hook. This concept variant maximizes surface contact with the branch, maximizes arm reach, and will produce the bending vibration of the mesquite beans.

COLLECTION

To begin our selection process, we set up a datum to compare our concept variants against each other. The concept variants are evaluated by the following criteria: Durability (3 points), Mobility of Guidance (2 points), Maneuverability (2 points), Cost (1 point), and Manufacturability (1 point).

The three concept variants with the highest scores will survive the Primary Qualitative Elimination and move towards the Secondary Qualitative Elimination process.

Table 18: Primary Qualitative Elimination for Collection

The top three concept variants are put through a secondary qualitative elimination process and evaluated by the following criteria: Tarp Clearance/Range of Motion (3 points), Storage Size (2 points), and Weight (1 point).

Table 19: Secondary Qualitative Elimination for Collection

The highest scoring concept variant is the Pivoting, Adjustable Height 180 Tarp. This concept variant maximizes tarp clearance/range of motion, maximizes storage size, and will be heavy enough to avoid tipping with the weight of the tarp.

FINAL CONCEPT(S)

After the selection process we arrived at the Final Concepts for both Excitation and Collection.

Figure 7: Circular Hook with Telescoping Pole – EXCITATION

Figure 8: Circular Hook with Telescoping Pole on Tree

Figure 9: Pivoting 180 Degree, Adjustable Height – COLLECTION

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EMBODIMENT DESIGN

STRATEGIES AND PRIORITIES

Starting from our final concept, we identified the necessary analyses and engineering work to realize the concept into a product.

TASK 1: DETERMINE THE TYPE OF VIBRATION TO DROP THE MESQUITE BEANS

Before building, we needed to determine the most optimal form of vibration to get the beans to fall. The different forms of vibration, along with their respective stress concentrations, are:

Figure 10: Forms of Vibration

The primary vibrational concepts used for this project are Natural Frequency Resonance, and Mode Shapes.

· Natural Frequency: The frequency in which a system vibrates at after an initial disturbance without external forces. [2] The natural frequency of a system can be denoted as:

Equation 1: General Natural Frequency Equation

where k is the system’s stiffness and m is the system’s mass. The mesquite bean can be modeled as a single degree of freedom mass-spring system, shown in Figure 11. With SDOF systems, there is only one natural frequency within the system.

Figure 11: Mesquite Bean Modeled as a SDOF Mass-Spring System

· Resonance: When the driving frequency of the system reaches/equals the system’s natural frequency, resonance occurs. During resonance, the system is prone to breakage or failure. Resonance can be denoted as:

Equation 2: Evidence of Resonance

Where ωn is the natural frequency of the system. [2] The goal of the vibrational aspect is to find the natural frequency of the mesquite bean to match the driving frequency. From here, we should be able to reach resonance and cause the mesquite bean to break off the branch.

· Mode shape: The shape that a system takes when it is excited. For this project’s analyses, the mode shape number is denoted as ⴖ.

For this analysis, we decided to use Frequency Studies through the Finite Element Analysis method for multiple Computer Aided Design (CAD) models. Through this study, we would be able to determine the natural frequencies of the mesquite beans.

To view our Mesquite Bean Sample Measurements, view here.

For the primary testing, we used simple cylinders with dimensions similar to that of our mesquite bean sample measurements. We completed the studies by treating our mesquite beans as clamped-free cantilever beams. We used the following figures and equations for reference to complete sanity checks for each type of vibration and their first mode shape [2]:

· AXIAL VIBRATION

Figure 12: Axial Deformation Due to Axial Vibration

Equation 3: Natural Frequency Equation for Axial Vibration for the nth Mode Shape

· BENDING VIBRATION

Figure 13: Perpendicular-To-X Deformation Due to Bending Vibration

Equation 4: Natural Frequency Equation for Bending Vibration for the nth Mode Shape

· TORSIONAL VIBRATION

Figure 14: Deformation Due to Torsional Vibration

Equation 5: Natural Frequency Equation for Torsional Vibration for the nth Mode Shape

Figure 15: Sanity Checks for the Different Forms of Vibration

Our sanity checks checked out with errors less than 1%. From here, we moved to increase the complexity of our mesquite beans, as shown in Figures 16 and 17. We completed the same FEA (Finite Element Analysis) process for the complex beans.

Figure 16: Different CAD Models Created

Figure 17: Increasing the Complexity of Mesquite Bean CAD Models

To view all our Mesquite Bean CAD Models, view here.

To view the FEA Simulations on our Mesquite Bean CAD Models, view here.

To view the Sanity Checks for the FEA Simulations, view here.

By completing a comparative analysis between our theoretical and experimental values, we determined the following:

· Bending Vibration is the prospective method of vibration on its own.

Figure 18: Prospective Vibration and Its Corresponding Motor Speed

To view our full Mesquite Bean Comparative Analysis, view here.

TASK 2: OFFSET MASS/MOTOR SYSTEM

With knowledge of Vibrations, an offset mass will be designed and utilized to create a radial load. [2] Given the following equation:

Where F_T is the transmitted force, m_o is the offset mass (typically the center of mass of the offset mass), e is the mass eccentricity, and ωdr is the driving frequency. Our offset mass is designed with the following template:

Figure 19: Offset Mass Diagram/Template

The radial load generated by the offset mass and the driving frequency will cause the vibration necessary to excite the mesquite beans throughout the mesquite branch. The radial load will depend on the orientation of the motor, such that:

Figure 20: Offset Mass/Motor Orientations and Their Respective Vibrations

Horizontal vibration will facilitate bending and torsional vibrations, while vertical vibration will facilitate axial vibration. [1] Based on this information, we decided to place the motor upright to facilitate the bending vibration necessary to drop the mesquite beans.

TASK 3: BUILD OUR PROTOTYPES ON SOLIDWORKS

Figure 21: Excitation - SolidWorks Prototype

Figure 22: Collection - SolidWorks Prototype

TASK 4: COMPILE A MATERIAL LIST

To view our Material List, view here.

TASK 5: BUILD OUR CIRCUIT

Our circuit utilizes an Arduino UNO, connection wires, a potentiometer, a 400KV DC Brushless Motor, a Speed Controller, and a rechargeable battery. This circuit will be used to operate the DC Brushless Motor to create a radial load given by the offset mass.

Figure 23: Our Theoretical Circuit

Figure 24: Our Physical Circuit

TASK 6: DESIGNING OUR MOTOR MOUNT

Click on the icon above to see the Design Process of the Motor Mount!

TASK 7: MANUFACTURING OUR PROTOTYPES

EXCITATION

Figure 25: Excitation Hook - From Idea to Reality

Figure 26: Carlos and Our Assembled Excitation Hook

Click on the icon above to see the Steps to Use Excitation!

COLLECTION

Figure 27: Milling and Welding Our Center Shaft

Figure 28: Partial Shaft/Swivel Assembly

Figure 29: Frame/Cart Weldments

Figure 30: PVC/Tarp Assembly

Click the icon above to see our Collection Tarp Swivel and Retraction!

Click the icon above to see the Steps to Use Collection!

Figure 31: Both Excitation and Collection in Use

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TESTING AND VALIDATION

EXPERIMENT 1

Our goal for this experiment was to test the vibrational frequencies emitted by the motor with its off-set mass. Our goal was to simulate a high and low bending frequency of 24.045 Hz (1442.7 RPM) and at least 8.0486 Hz (482.916 RPM) respectively at the end of the mesquite branch where the beans would naturally grow and develop during harvesting season.

For our first experiment, instead of following the chosen design of a hook, we attached our motor to the tree with a belt to get a closer contact with the tree. This would provide the least amount of dissipation caused by a branch interface. Because we were past the bean season, measuring the levels of vibration where the beans would naturally grow was the next best solution.

To view the full testing protocol of this experiment, view here.

Figure 32: Alexandra and Stephanie holding the circuit/motor assembly for testing

Click the icon above to see our assembly exciting the leaves of a mesquite tree!

Figure 33: Phone Used as an Accelerometer for Testing Purposes

We used our cell phone as a means of recording our data. The app used was called phyphox, which utilizes the accelerometer within a smartphone to measure the acceleration of the vibrations transmitted to the end of the branches.

phyphox_dark – phyphox

Figure 34: phyphox - The application used to obtain our vibrational data

Figure 35: Acceleration vs Time Obtained from Experiment 1

The raw data collected through this experiment allowed us to create an acceleration vs time graph. Within this data, one can see the lower peaks in which there is minimal excitation and one can see the higher peaks that represent the approach to resonance at that location on the branch of the tree.

With a signal like the one shown in Figure 31, the approach to this would be to apply a Fourier analysis to convert the signal from its time domain to the frequency domain. From there, the dynamic response of the mesquite bean would be obtained.

After further analysis of the experiments data, we noticed that by adding the cell phone to the end of the branch would make a significant difference in the data we wished to collect. This would change the problem from a cantilever beam to one with a weight at the end of it therefore making the experimental data invalid.

EXPERIMENT 2

For the second experiment, our purpose was to test the concept further by simulating the drop of a mesquite bean due to excitation. However, since the harvesting season had already passed, we looked to an alternative and used rubber bands simulate the mesquite bean stem being attached to the tree.

Figure 36: Mesquite Bean Suspended onto Branch by Rubber Band

Figure 37: Image Showing the Mesquite Beans Suspended on a Branch with Rubber Bands

We were going to replicate the protocol in Experiment 1, but our motor began to malfunction due to faulty wiring and completely stop working. We were unable to complete further testing because finding and ordering a new motor was necessary. However, if our motor had not given out, the vibrational frequency transmitted from the motor to the bean would have been measured and collected by analyzing a video of the vibrations in the bean as it fell shot by shot. Experiment 2 would have provided us with important data which would have confirmed our FEA analysis on the bending frequencies.

Click the icon above to see our motor setup for Experiment 2. You will be able to see the motor malfunction.

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REFERENCES

[1] AB-027 : Eccentric Mass Parameters For Vibration Motors - Application Notes. (n.d.). Retrieved March 21, 2020, from https://www.precisionmicrodrives.com/content/ab-027-eccentric-mass-parameters-for-vibration-motors/

[2] Inman, D. J. (2014). Engineering vibration. Boston: Pearson.

[3] Lesson 2: Problem formulation. (n.d.). Retrieved November 27, 2020, from http://betterthesis.dk/getting-started/type-of-study . University of Southern Denmark Library and the Unit for health promotion research. University of Copenhagen, Department of International Health and Faculty Library of Natural and Health Sciences

[4] Problem Identification. (2019, January 02). Retrieved November 27, 2020, from https://www.cdc.gov/policy/polaris/policyprocess/problem_identification.html

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