Table of Contents
Team Vision for Subsystem-Level Design Phase
The team tasked itself with diving into the P15045 stander in order to identify existing problem areas and potentially fix them prior to our MSD II design. The team also desired a better understanding of the constraints surrounding the overall motor system to ensure that any difference from the P15045 system could be supported. SMEs for microcontrollers, motor systems, and sensors were identified for needed feedback on the team's design concepts and potential solutions. Further information on the control scheme and stander use cases was needed, and meeting with Linda Brown was determined necessary.
Feasibility: Prototyping, Analysis, Simulation
Initial testing (3/12)
- Made initial debugging changes to code retrieved from P15045 site
- Identified potential issues with encoders not matching
- Buffering issues with remote input (see analysis)
- Stop/Start jerking appears resolved
Performance Observations (3/16)
- Wheels rotate much better when suspended (right wheel doesn't move regularly on the ground)
- Wheel performance over multiple presses appears better than consistent force applied to button
- Speed dial affects the wheel performance (notably the right wheel)
- Right wheel may work briefly, at the expense of the left wheel stopping
- While button is pressed the stander may alternate which wheel it uses (stopping the other).
- Stander cannot make it 20 feet, has made at least a 90 degree turn by 5-10 feet.
- Left motor/wheel is kicked/tilted
- Overall, fewer rpm on right wheel regardless of air/ground contact.
Further testing (3/17)Meeting with Dr. Day about Project Scope What stander(model) will we be working with?
- Comes down to having a real customer to design the stander to (either someone who has reached out to Dr. Day or specified by Linda), or continuing the work completed by previous iterations to design a marketable prototype.
- If designing to a specific customer, then everyone needs to be on board to push for a completely working stander. This is a large commitment, and the team needs to come through if this is the route we choose to go.
- If nothing else, design should be to the rabbit size 1 or 2 pediatric stander.
Are we designing to Linda's specifications or a designated child?
- It is necessary to still gain input from Linda since she has expertise in the area.
- Not a huge change, but at some point the focus needs to be on the child's ability to use and access rather than Linda's preferences.
- If designing to a specific child, then communication with the family will be instrumental to the overall design process.
What happens if we decide to step up to a bigger scale product(i.e. multiple standers for multiple customers)?
- 3 to 6 standers could potentially be sent out to customers to gain insight on usability, product shortfalls, look, and other necessary modifications.
- There could be a change in the cost to the customer originally stated at $500 to free, for the first stander. This would allow for feedback on technology, but it must be clear that the product is a student project.
- Quality testing would need to be identified and written with testing specifications.
Debouncing the Encoders
- Found that there was a severe debouncing issue with the encoders.
- Found that vibrations in the stander could triger encoder hundreds of times a second.
- Verified proper operation after implementing debounce.
- Used properly working encoders to test varying versions of quickly sketched with the intent to see if stander could drive straight even if in a choppy manner.
- Found that all sketches developed behaved vastly different when stander wasn't suspended.
- Observations were that when actually on the ground stander tended to move in a circle.
- Found a working PID controller that we wish to modify and use to test stander.
- GUI found to help support measurements of wheel rotation.
- Team's self deadline of 2 weeks before moving on from P15045 stander.
P15045 Stander Analysis
A working copy of the action log being used to document all things done to the stander can be found here.
Drawings, Schematics, Flow Charts, etc.
Current Stander Design
- Attachment of Battery Mount
- Attachment of Bumper System
- Battery Housing Design
The design criteria and selection for microcontrollers can be seen in the Microcontroller Selection Diagram.
Pro/Con Analysis of Simblee After developing software flowchart and performing analysis of available micro-controllers, there was one - The Simblee - that stood out due to some unique features. A specific Pro/Con Analysis can be found here in the Simblee Pro/Con Analysis.
Wheel System Configurations
The live document with the motor analysis and configuration set-ups can be found here.
Finding Candidates for Test TrialP16045 has decided to include two candidates to participate in our test trial of our motor kit. There will be multiple phases to this.
Phase 1: Compile information of candidates that are interested in participating in the test trial.
Phase 2: Contact possible candidates that best fit the criteria of the trial. The conversation will help both parties understand what is expected from each other and to get on the same page.
SME NotesNotes from Meeting with Linda Brown
Please refer to the current risk analysis chart for the live document, and to see the overall changes in risk identified from the problem definition design review to the subsystem level design review.
Key Changes in Risk Analysis Chart
- According to recent conversations with Linda, it was determined that the current stander size and design is not seen as obtrusive to the point that other kids will not interact with the end user.
- Based on observations the connection of the batter box is not robust. This is due to the battery box not even using most of the velcro to be held onto the stander, and is an issue. Further, the velco makes the box extremely difficult to be removed for wire inspection or battery replacement. Design changes are being looked into to utilize the t-slot rods for easy removal and safe connection to the stander.
- As of recent interaction with Dr.Day, budget requirements are not seen as much of an issue or risk to design prototyping and creation. Although it should be noted that general component cost will continue to be looked at through the design process to reduce the kit cost without hindering robust design.
- Risks associated with communication to specific customers (other than Linda) need to be addressed prior to moving forward.
- Further, risks identified through P15045 stander testing have become more aware, especially through electrical systems.