Integrated System Build & Test
Table of Contents
Team Vision for Integrated System Build & Test PhaseDuring this phase we sought to
- Lay out rough outline of paper for MSD
- Finish manufacturing of mounting subsystem
- Manufacture controls mounting, and devise a solution for waterproofing
- Finish electrical system testing
- Assemble the entire electrical subsystem
- Finish submission to access technology conference
- Assemble entire system on wheelchair and begin initial testing
During this phase we managed to
- Finished manufacturing of mounting subsystem
- Finished Electrical System testing
- Assembled the electrical subsystem
- Finished submission to Access Technology Conference
- Stress analysis on working end of the wheelchair.
- Found suitable materials for mounting of the controls subsystem
Mechanical Strength Analysis
Current Part Strength Analysis
Modified Part Strength Analysis
- Modified Part Strength Analysis
- Failure Strength Analysis for Modified Part
Part and Battery Box AnalysisThe decision behind the placement of the box on top of the part was straightforward. After maximizing the surface area of the mounting plate in order to stablize the box as much as possible, the box is to be placed in a vertical orientation as shown below. The batteries are placed inside the box as shown, so they are mainly supported by the strong steel mounting piece.
The box was initially positioned a little further back away from where connectors are bolted. Alan suggested that the box can be on top of the whole part, so the box can be even more stabilized, and we can make use of the bolts as well. The result is shown in the model below.
- 3D Model Views & Images
- Strength Analysis
- Failure Analysis
Mechanical Subsystem AssemblyAfter getting all of the parts together a preliminary assembly was made to see what problems would need to be overcome for the final build. At first the motor was attached to the rider's left side of the gearbox bracket. This caused the system to have unwanted rotation that allowed the motor to hit the ground. Several solutions were iterated through to see what would eliminate this rotation about the axis the best. The first was very crude and used bungee cords to hold the motor up. This was not sufficient because the motor still hit the ground. Looking at the tie rod ends of the toplink closest to the motor it seemed that the freedom provided was too much. Thus the tie rod ends were welded so that they no longer had the freedom to about anything other than the bolt. Upon reassembly this seemed to help however the motor was still touching the ground. After another investigation it was found that the top links unscrewed in the direction the the motor was applying its force. To correct this the motor was moved to the drivers right side of the gearbox bracket. This resulted in the motor always applying a tightening force on the toplinks which will prevent the motor from touching the ground.
Unfortunately our old buzzer wasn't able to work with our application so with the help from Dr. Fuller we were able to get a new buzzer. The CPE-220 CUI Inc Buzzer is shown below along with its datasheet.
Wiring DiagramHere is a wiring diagram of how we wired all the electrical components and motor. The buzzer and circuit added is not displayed yet since it is pending on what we will do.
Electrical Circuit AddedProblems we were having with adding this buzzer was it needed to be rated at 5V for it to work. Because of this we added a voltage regulator which will decrease the 24V from the battery to 5V which will allow the Buzzer to work. Below is the schematic of the voltage regulator and what the part looks like.
This is simulation results of the voltage regulator when applying 24V input to it. As you can see the voltage coming out with be 5V and the current is around 4.1mA which is perfect for our situation.
As well a P16NF06 NMOS transistor was added to the circuit in order to control when we want the buzzer to go off. We want it to go off when the motor goes in shutdown mode. The datasheet for the NMOS is shown below.
The full circuit added is shown below with the NMOS transistor and Voltage Regulator combined together.
When the Motor goes into shut down mode the buzzer starts buzzing as expected.
Motor Shut Down Mode Demo: https://www.youtube.com/watch?v=f7Tg0c2mbvU
However the problem we are having is we are getting Current Spikes when we first turn the PWM on which is making the buzzer go off for a second or two. We are currently trying to find ways in order to limit the current spikes or get rid of them all together. We are currently working with Dr. Fuller on a solution.
Current Spiking Demo: https://www.youtube.com/watch?v=RIKgMGATi1w
PWM with Load TestThe PWM was tested again with a load this time and the results achieved were exactly what we wanted. The completed test is shown below.
Risk and Problem Tracking
Plans for next phase
- Find a working solution to mount the box
- Finish strength analysis and future recommendation for continuation
- Fully assemble the device and tests
- Start writing the paper for final report
- Prepare poster for Imagine RIT