MSD Group 14045Mobile Pediatric StanderFinal Presentation

Guide: Edward HanzlikSponsor: Dr. Steven DayCustomer: Linda Brown

Alex Hebert - Mechanical Engineer LeadGreg Roeth - Project Lead/M.E.Emily Courtney - Mechanical EngineerJohn Daley - Electrical Engineer LeadMartha Vargas - Electrical Engineer

Project Description

Motivation: To give a disabled child the autonomy of self-propulsion around his or her therapy/classroom environment that he or she ordinarily wouldn’t have.

Key Features:○ Upright position ○ Safe, comfortable, and smooth transportation of the passenger○ Ability for third party control○ Interchangeable controls○ Adjustable tray system○ Better electronics packaging○ Functional remote control

Key High Level Customer Needs/Engineering Specs

● Tray - Flexibility to accommodate a wide range of user needs○ Move forward/back,left/right○ Pivot up/down

● Battery Box - Professional and safe packaging solution○ Hide electronics○ Keep user safe○ Accessible for maintenance

● Controls - “Plug and Play” capability○ Interchangeable○ Flexibility for future development

Concept Summary

● Tray System● Remote● Battery Box● Electrical System

Tray System

Remote

● Wired○ Buttons○ Power

● Bluetooth● Override/Assist● Code

Battery Box

System Architecture● 3 large pieces, only 2 were made

○ Stander Driver, Stander Controls, Remote was not made● Implemented this way so that the controls could be switched out, ● All communication done through UART

○ Further development can make anything as long as it communicates in the same way○ UART routed through a USB cable for ease of use (it is not USB communication)○ Communication needs to be fast enough for the user to not notice

● Stander Driver makes the big decisions○ Receives controls and inputs○ Decides what is the ultimate command○ Translates commands into speeds at the wheels

● Stander Controls ○ Takes user controls, (buttons) and turns it into a valid command for the stander driver○ Sanitizes user input

System Architecture

Stander Driver● Takes commands over UART● Converts command to wheel speeds● Monitors Wheel Speeds

○ Using Quadrature Encoders○ Tries to keep the wheels straight

■ Master-Slave wheel system■ Proportional controller■ PI controller

○ Tries to control acceleration of stander■ Acceleration isn’t noticeable

Controls● Ultimately Communicates a command to the Stander Driver through UART

○ Forward, Reverse, Right, Left, …○ No further protocol was developed○ Is not 2 way communication at this time○ Further Improvements could be incorporating a speed in with the command

● Easiest to Implement is Buttons○ Fast, and robust○ Software debouncing (hysteresis through polling)○ Each button corresponds to a command, with a few multi-button commands○ Certain combinations of buttons are not valid○ Sends new command when a new button is pressed, or no button is pressed

Electrical System Tests● Connection

○ designed to only be 1 USB cable from controls to driver○ PASSED

● Max Current Draw○ Needs to stay low enough to protect wires and not blow fuses in worst case scenario○ 15A fuses on wheels (main current draw)○ Only Draws 8.5A max in a stall○ PASSED

● Controls/Debug Stander controls test○ Should be less than 150ms○ was 16ms from button push to voltage on motors○ PASSED

● Bump Test○ Bumper on the front of the stander prevents forward commands○ Allows backward movement○ PASSED

Mechanical Tests● Dynamic

○ Max Speed-> 0.78 mph○ Acceleration-> 0.049 g○ Straight Travel-> Failed, but correctable○ Maximum Tilt Angle->

■ Side 34.4 degrees■ Front 43.6 degrees■ Back 55.9 degrees

● Sharp Corners/ Pinch Points->Pass● Weight Test-> 74.5 lbs

Objective Project Evaluation: Success and Failure

Success:● Battery Box

○ Components fit○ Much cleaner packaging solution

● Tray System○ Increased Adjustability○ Folds

● Button Controls○ Sends commands to Stander

● Bump Sensor○ Stops stander as designed

● Tears of joy from Dr. Hanzlik● Popular exhibit at Imagine, 2nd place in

the ARM contest, and we made the news!

Failures:● Remote

○ Not operational● Multiple Controls

○ Only buttons developed● Control System

○ Does not travel straight○ Other bugs

Instructables

Budget

Allotted Funds $1,400.00

Total Spending $1,399.13

System System Cost

Tray $ 305.60

Controls $ 662.35

Wheels $ 438.85

Battery Box $ 304.79

Overall Cost $ 1,711.59

Team Spending: Kit Cost Breakdown:

Opportunities/Suggestions for Future Work

● Battery Box○ As is, everything fits...barely○ If it is redesigned/remade, adding more room in both the electronics

compartment and battery compartment would be useful○ Making it in such a way that it can be waterproof would be beneficial

as well. Due to warpage from welding this was not possible for us.● Control System

○ Position Feedback was implemented but it isn’t tuned properly, so the stander does not drive straight.

○ For some reason, “back” + “right” doesn’t work.○ Potentiometer knob for speed control was installed but not

implemented

Opportunities/Suggestions for Future Work

● Remote○ Mechanically there, but coding/wiring was not able to be completed

due to time constraints.○ This is something the customer really wants, so it should definitely be

included in v3.0.○ Bluetooth for remote system wasn’t developed

● Wheel Adapters○ Alex designed a concept for a replacement for the stock adapters,

which was too expensive to manufacture by 3D printing or CNC○ If this is truly developed into a kit, making these parts affordably would

be a great addition.

Acknowledgements

MSD Administration● Dr. Ed Hanzlik - Faculty Guide● Dr. Steven Day - Customer● Linda Brown - Customer

Faculty Experts● Mark Indovina - Control System Assistance● Dr. Mark Kempski - Control System Assistance● Dr. Stephen Boedo - Wheel Adapter Design Assistance● Dr. George Slack - Control System Assistance● Rob Kraynik - Fabrication Assistance● Jan Maneti - Fabrication Assistance● Dave Hathaway - Fabrication Assistance

Thank you!