Design
The design process for this project was broken down into four different stages. First the customer requirements were attained through customer interviews, and these requirements were then translated into engineering requirements. A house of quality was used to ensure all the engineering requirements satisfied the customer requirements as well as any other requirements the team deemed necessary. This process is show in the Problem Definition. From there a functional decomposition was used to break down the project into its constituents. Benchmarking was performed to understand what current technologies were being used in similar applications. These technologies were combined in a morphological chart and then analyzed using a pugh chart to determine which combination of technologies would work best for our project. A feasibility analysis was performed to ensure all technologies would be applicable to our project. All of this is summarized in the System Design. From there, the project was broken down into three subsystems: Control, Navigation, and Force Actuation. Preliminary designs were worked up for each and a bill of materials was generated for the needed parts. This is shown in the Subsystem Design. The particulars of each subsystem were then designed and combined together to create out Detailed Design. This detailed design encompassed everything we planned on doing with this project. Although some modification were made as the project was built, the overall design remained fairly consistent.
Problem Definition & System Design
Team Vision for Problem Definition Phase
The project objectives were elaborated in detail to come up with a problem definition which satisfies all parties. Customer interviews were held, and engineering requirements were drafted. House of quality analysis was performed and use case scenarios were drafted.
Project Definition
An Inflatable Robotic Hand is a portable, mountable device that can inflate, manipulate an object, and deflate remotely. The system will be house in a container mounted on a RC car. This device will utilize some of the same principles, specifically the air muscles, used in previous RIT senior design projects P14253, P09023, P08023, and P08024. This project will add the ability of inflating out of a small container.
The goals of this project are to analyze previous air muscle designs, and other inflatable robot technologies, to identify an opportunity to combine these ideas into one product. The expected results is a functional prototype that can be applied to the task. The prototype must use air for generating actuation forces while resembling a hand with a minimum of three fingers.
Use Case
Project Goals & Key Deliverables
- The arm, hand, and vehicle can be remotely controlled by user
- Pick up a tennis ball
- Mounted on an RC vehicle
- Inflate out from a compartment
- Actuation force is produced by air muscles
Customer Requirements (Needs)
Purpose
To decompose the Problem Statement into functions of elements needed to satisfy the customer.
Customer Requirements
| Rqmt # | Importance | Description |
|---|---|---|
| C001 | 9 | Must use air for inflation and actuation forces |
| C002 | 9 | Must be able to pick up a tennis ball up to 2 in off the ground |
| C003 | 9 | Must resemble a hand or fingers |
| C004 | 9 | Must inflate from a container housed on an RC vehicle |
| C005 | 3 | Must deflate fully back into the container |
| C006 | 9 | Must be remote controlled |
| C007 | 9 | Material selection must withstand inflation/deflation cycles without popping or tearing |
| C008 | 3 | Use a single controller to control both the robotic arm and the RC vehicle |
| C009 | 3 | Prototype and final model must be built with a $750 budget |
| C010 | 3 | Move object (tennis ball) from one location to another |
| C011 | 1 | Mounted camera for targeting and navigation |
Inputs
- PRP
- Problem Statement
- Customer Interviews
- Art North & Dr. Lamkin-Kennard.
Outputs
Engineering Requirements (Metrics & Specifications)
Purpose
Create a contract between the engineer and the customer where indisputable satisfaction of the engineering requirements equates to customer satisfaction
Engineering Requirements:
| Rqmt # | Importance | Engineering Requirement | Unit | Target Value | Marginal Value |
|---|---|---|---|---|---|
| 001 | 1 | Air compressor power | psi | > 120 | 100 |
| 002 | 9 | Air compressor flow rate | scfm | > 0.88 | 0.3 |
| 003 | 9 | Inflation time | sec | < 2 | 5 |
| 004 | 3 | Deflation time | sec | < 10 | 15 |
| 005 | 3 | Inflation arm reach | in | > 6 | 4 |
| 006 | 1 | Object lift distance | in | > 6 | 4 |
| 007 | 9 | Hand grip strength | psi | > 20 | 15 |
| 008 | 3 | Stored air volume | ml | > 1200 | 200 |
| 009 | 3 | Stored air pressure | psi | < 100 | 80 |
| 010 | 9 | Number of fingers on robotic hand | units | = 3 | 3 |
| 011 | 9 | Battery life | min | > 90 | 30 |
| 012 | 3 | Chassis load weight capacity | lb | < 40 | 120 |
| 013 | 9 | Chassis surface mount area | in^2 | < 24x24 | 30x30 |
| 014 | 3 | Arm container cross-sectional area | in^2 | < 6x6 | 8x8 |
| 015 | 1 | Arm container height | in | < 8 | 10 |
Inputs and Source
- PRP
- Dr. Lamkin-Kennard
- Art North
Outputs and Destination
- HoQ
Constraints
From Customer Requirements
- Inflation mechanism must use air only
- Robotic arm and hand must fit inside a small container
From Engineering Requirements
- Weight of robotic arm, air compressor, tank, and control systems must not exceed chassis weight capacity
- Must have large enough power source to supply power to the motors, compressors, and control systems
House of Quality
Inputs and Source
- PRP
- Customer Requirements
- Engineering Requirements
- Benchmarking Data
Outputs and Destination
Design phase
Team Vision for System-Level Design Phase
Our plan was to develop the functional decomposition of our system, come up with possible solutions, and out line the system architecture. We also planned on benchmarking the different components and analyzing the feasibility.
We were able to complete all of the tasks we set forth to do for this phase.
Functional Decomposition
Benchmarking
Morphological Chart and Concept Development
Concept Selection
Concept Selection & Pugh Chart
Systems Architecture
Feasibility: Prototyping, Analysis, Simulation
Risk Assessment
Subsystem Design
Team Vision for Subsystem-Level Design Phase
Our primary objective in this phase was to prototype and analyze our 3 subsystems which were the Control, Navigation, and Force Actuation. For each subsystem, we came up with different proof-of-concepts for different designs, which we then benchmarked and chose the best design to move forward with.
Control: H-bridge, Motor drivers, Solenoid drivers,
Navigation: Motors, Chassis, Wheels, Gearbox, BOM
Force Actuation: Solenoid valves, Flow loop design, Arm designs, Hand, BOM
Sub-Subsystem Design & Engineering Requirements
Feasibility: Prototyping, Analysis, Simulation
Control:
Micro-controller:
- considered PWM requirements
- MSP430
Peripherals:
- Drivers
- solenoid drivers
- motor drivers
- compressor driver
Power Regulators:
Navigation:
Locomotion:
- motors
- CIM
- Pololu 100:1 gear motor
- wheels
- Pololu wheels
- gearbox
Structural: 
- frame (2ft x 2ft)
Force Actuation:
Arm:
- 2 arm designs considered
- 4 Channel Arm (4ChA)
- Slinky Arm (SA)
- preliminary prototyping of 4 Channel Arm (4ChA)
- mold being made
- material considerations: Smooth-On Ecoflex 0030, mold-star
Finger:
- 1 finger design considered
- PneuNets Bending Actuator (PNBA)
- preliminary prototyping of PNBA has begun
- prototype part made
Pressure Distribution:
- Flow loop designed (schematic below)
- Solenoid valves tested
- Pressure regulators tested
Inputs and Source
- Engineering Requirements
- Concept Selection
- System Architecture
Outputs and Destination
- A list of Design Parameters, Quantified Targets, and acceptable tolerances
- Sensitivity analysis
- Concept Selection
Drawings, Schematics, Flow Charts, etc.
Air System Schematic
- A, B, C, D, E - one-way solenoid valves
- F - two-way solenoid valve
Valve Positioning:
- 1 (power on - valve closed)
- 0 (power off - valve open)
| Valves | ||||||
|---|---|---|---|---|---|---|
| Task | A | B | C | D | E | F |
| Tank Fill | 0 | 0 | 0 | 1 | 0 | 0 |
| Arm Inflation | 0 | 1 | 0 | 0 | 1 | 0 |
| Finger Inflation | 0 | 1 | 1 | 0 | 0 | 0 |
| Finger Deflation | 1 | 0 | 1 | 1 | 0 | 1 |
| Arm Deflation | 1 | 0 | 0 | 1 | 1 | 1 |
| Pressure Release | 0 | 0 | 0 | 1 | 0 | 0 |
Bill of Materials (BOM)
Navigation:
| QTY | Description | Supplier | Cost ($) |
|---|---|---|---|
| ----- | ------------Structural------------ | ------------ | ---------- |
| 6 | 30” Aluminum C-Channel | Andymark | $18/ea |
| 8 | C-Base Aluminum Corner | Andymark | $4/ea |
| 42 | ¼” - 20 Hex Head Bolts | N/A | $14 |
| ----- | ------------Locomotion------------ | ------------ | ---------- |
| 2 | 2.5” CIM Motor | Andymark | $28/ea |
| 2 | Toughbox 14.88:1 Gear Box | Andymark | $75/ea |
| 4 | 4” Rubber Treaded Wheel | Andymark | $4/ea |
| 2 | ½” x 4” Free Axle | N/A | N/A |
| 2 | Direct Drive Collar | N/A | N/A |
| 2 | 3’ Drive Chain | N/A | N/A |
| 2 | Sprockets for Chain Drive | N/A | N/A |
Air System:
| QTY | Description | Supplier | Cost per Part($) | Link |
|---|---|---|---|---|
| 1 | Compressor | AndyMark | 69.00 | Link |
| 1 | Check Valve | McMaster | 17.03 | Link |
| 2 | Air Tank | AndyMark | 16.00 | Link |
| 8 | 1-Way Solenoid Valve | RIT | 0 | N/A |
| 1 | 2-way Soleniod Valve | RIT | 0 | N/A |
| 17 | Soleniod Valve Connector | RIT | 0 | N/A |
| 2 | Pressure Regulator | RIT | 0 | N/A |
| 2 | 2-Outlet Manifold | McMaster | 22.94 | Link |
| 6 | 1/4" NPT Compression Fitting | McMaster | 1.35 | Link |
| 4 | 1/8" NPT Compression Fitting | McMaster | 1.30 | Link |
| 25 ft. | 1/4" OD Polyethylene Tubing | McMaster | 0.10 per foot | Link |
| 25 ft. | 1/8" OD Polyethylene Tubing | McMaster | 0.05 per foot | Link |
Risk Assessment
Detailed Design
Team Vision for Detailed Design Phase
Our primary objectives for this phase were to:
- Update test plans
- Control: motor and solenoid drivers, power supplies, controller mapping, transmission range
- Navigation: motor/robot movement speed, battery life, frame weight and size
- Force Actuation: mock flow loop, arm and finger
- Acquire remaining parts necessary for test plans
- Update schematics and flow charts for each subsystem
- Come up with team and individual plans for MSD II
- Prepare for the gate review
Detailed Design Phase To-Do List
Prototyping, Engineering Analysis, Simulation
The following subsystems will be prototyped:
Control System
Solenoid Drivers
Force Actuation System
Arm
Fingers
Mock Flow Loop
Drawings, Schematics, Flow Charts, Simulations
Control System
Motor Driver:
Motor Driver Documentation
Power Supply:
5V Power Supply Documentation
24V Power Supply Documentation
Solenoid Driver:
Drive System
Priming of Air Flow System
Arm and Finger System
Controls Preliminary Code: Xbox controller Arduino code
Controls Risk Management: Bad User Input
Navigation System
Feasibility: Torque Analysis
Full Model Assembly:
Base Model Assembly:
Upper Model Assembly:
Force Actuation System
Feasibility: Air System
Detailed Flow Loop:
Mock Flow Loop:
Bill of Material (BOM)
We consolidated the BOM of each subsystem into one: Total BOM
Test Plans
Control System
Navigation System
Force Actuation System
Design and Flowcharts
Updated System Architecture
3 Subsystems:
- Control System
- Navigation System
- Force Actuation System
