P13045: Mobile Pediatric Stander
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Detailed Design

Table of Contents

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Tipping Analysis

The additional equipment that will be used to motorize the stander will mostly be added to towards the bottom of the device, therefore further lowering the center of mass of the device. This is only making the device safer and it would take upwards of 90 lbs to tip the motorized device from any angle.

Tipping Calculations

Power Consumption Analysis

Analysis of Power Consumption
Component Current Draw
Motors 1.5A*2
Motor Controllers 50mA*2
Inputs negligible
Microcontroller ~50mA
Sensors negligible

It can be seen that the major consumer of power will be the motors which will draw a minimum of 3 A (no load). This will increase dependent on the weight being moved but during our testing it maxed out at just 4 A. The batteries we have looked at are rated in Amps * Hours. For purposes of estimation we’ll assume a student will use the power stander with small bursts of movement and large spans of no movement. Discussions with the customer have determined that the device would be used for roughly 2-3 hours per day. This time is filled by two one-hour sessions as well as the possibility of some additional usage throughout the day. Using our value of power (~4 A) and our maximum timeframe, 3 hours, we can see that a battery with a power rating of 12 Amps*Hours will provide enough power to power our stander for a standard day. Because this device is so important to the daily function of the client, we would want to add a small buffer time to prevent the stander from dying completely. Finally, we must choose a battery with a current rating of at least 4 A, which is not a simple task.

Drawings, Schematics, Flow Charts, Simulations

System Design

System Design

Software Flow Chart

Software Flow Chart

Sensor Coverage

Currently the sensors being used for object detection include ultrasonic sensors and bump sensors. There will be four bump sensors, one on each of the wheel mounts, and seven ultrasonic sensors. The scenarios below describe the two different areas of coverage using the wide and narrow range sensors.

Scenario 1

public/Photo Gallery/DDR/AllSensorsTop_1.jpg public/Photo Gallery/DDR/AllSensorsIso_1.jpg public/Photo Gallery/DDR/UltrasonicCorner_1.jpg

Scenario 2

public/Photo Gallery/DDR/30DegTop_1.jpg public/Photo Gallery/DDR/30degIso_1.jpg

Bill of Material (BOM)

Bill of Materials

Test Plans

Summary of Preliminary Test Plan
Mode 1
Mode 1 for the stander requires the user to hold the button down to move.
Mode 2
Mode 2 for the stander requires the user to push a directional button and it will move in that direction until the same button is pressed again or the STOP button is pressed

Sensor Safety Tests

Risk Assessment

General Risk Assessment

Technical Risks

Detailed Design Review

Detailed Design Review Presentation

Detailed Design Review Action Items

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