P16007: Motor-Assisted Wheelchair
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Customer Handoff & Final Project Documentation

Table of Contents

Team Vision for Final Demo and Handoff

During this phase we sought to

During this phase we managed to

Test Results Summary

Most of the tests could be completed as listed in the testing plans (Also here and here). However there were difficulties in performing the battery life test, as there were mechanical failings on the motor gearbox wheel assembly.

While trying to test the capability on more severe inclines, it was found that the omniwheel would not remain in place axially along the gearbox output shaft before ImagineRIT.

Because of this, a hole needed to be drilled perpendicular to the keyway. However the hole was not aligned with the midpoint of the keyway. As a result the set screw inserted would regularly fail as well. After bringing the gearbox to the machine shop again, another hole was drilled perpendicular to the key midway between the keyway so that the wheel hub would lie directly over the keyway.

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Ramp Testing by team member Nick

Individual Test Results

In Use Length Test Results

In Use Width Test Results

Stored Volume Test Results

Weight of Addition Test Results

Noise Level Test Results

Max Climbing Incline Test Result 1

Max Climbing Incline Test Result 2

Max Speed Test Results

Driving Range and Battery Life Test Results

Risk and Problem Tracking

Final Risk Analysis and Problem Tracker

Final Project Documentation

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Technical Paper

Team Poster

Final Bill of Materials

User Manual

Assembly Manual

Motor Software

Final Cad and Drawings

System Photos

The motor has various operating modes. The two modes tested are speed control and torque control. Both of these modes are proportional to the duty cycle of a PWM signal. The higher the duty cycle yields the higher torque or speed. Each mode has its own advantages. However, the torque suits our need the best. In torque mode, when the motor is powered but duty cycle is zero, the motor is still free to spin. On the other hand, the speed mode prevents it from spinning to do 0% duty cycle meaning zero speed. The torque mode only has a max speed limitation, which is for shutting down the motor when the motor is at max speed for over 10 seconds. However, if the motor stalls, it will shutdown still. Please refer to the following document for more information about controlling the motor in other way.

Clearpath Motor Manual form Teknic

In the case of stall, a buzzer would go off. The buzzer is controlled by the output signals HLFB+ and HLFB- coming from the motor. HLFB+ and HLFB- conduct when the motor is working. When the motor enters shutdown mode, these two signals become an open in the circuit.

Schematic

From the control panel, there are two switches and one knob. One switch is a rocker switch that turns the motor on or off. The other switch is an emergency push button switch. It is a quick way to shut of the motor, it can't be turn back on accidentally. The knob is for changing the duty cycle of the PWM signal.

About the wiring connections, please refer back to Assembly Manual for how the wire connectors looked like. However, basically, the positive terminal, labeled as "Red", from the battery goes into the emergency button, to the rocker switch and the pwm controller. From the PWM controller and the rocker switch, the positive terminal comes back as the "Red Black" wire. This wire will then go into the power of the motor. The negative terminal is labeled as "Black". It goes into the PWM controller and to the motor directly. The yellow wires represent the PWM controller signals. The "yellow" is the positive, and the"yellow black" is the negative. The white wires from the control panel are the switch that splits the two sections in the schematic link shown above. The green wires in the box are connected to the enable of the motor. The PWM signal goes into the motor as yellow wires as well. The white wires coming out of the motor are the HLFB+ and HLFB-.

Recommendations for Future work

Functional Demo Materials

Final Presentation Single Slide

Max Incline Test: https://www.youtube.com/watch?v=vhn57Zr9fn8

Max Distance Test: https://www.youtube.com/watch?v=dNdWmki-pTA

Plans for Wrap-up

The last thing needed to be done was documentation. The project works as intended, though there are many aspects that can be improved with extra time and money. Most problems encountered were solved by changing the motor operating mode from speed control to torque control. Torque control has the flexibility of letting the motor to operate at any speed under the programmed max speed as long as the torque stays at assigned value that is controlled by the PWM controller. When power is on, the motor is no longer locked into place because the motor is providing no torque, allowing the user to push him/herself.

With assistance, the system can propel the user up an incline as seen in the max incline test. On its own the system does have some difficulty in propelling itself. This can be solved by changing increasing the gear ratio of the gearbox. However, it can also be done by adding another 12V battery in series to increase the power. There are trade-offs between either large amount of additional funding or increased weight. The weight issue needs to be resolved and can be adjusted by changing some of the materials used.

The wheelchair and system will be returned to the BAD lab (as that was the 'official workspace'). There is a possibility that Alan will take it to the end user for opinions/critiques. If this is the case, he will be in contact with the MSD department.


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