P16241: Autonomous People Mover Phase 3
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Detailed Design

Table of Contents

Team Vision for Detailed Design Phase

For this phase, the team wanted to take a step back and realize everything that we needed in order to implement our designs next semester. This included drawings, schematics, flow diagrams, purchasing and budget information, as well as a preliminary schedule for building.

Prototyping, Engineering Analysis, Simulation

Subsystem Microcontroller Performance Study

The team identified an opportunity to minimize the number of microcontrollers used in order to simplify wiring and eliminate the risk of failure. To see if this was possible, the team performed a study to estimate how much processing power each subsystem is going to need and decide how many boards are needed.

Microcontroller Performance Study

Ultrasonics Mounting Study

The team discussed having 2-3 more ultrasonic sensors on the front of the cart to work with the LiDAR in recognizing and detecting obstacles. In this analysis, new ultrasonic sensors were looked at and modeled on the front of the cart to determine their detection patterns.

In addition to these ultrasonic sensors, small ultrasonic parking sensors are being looked into to account for the small gaps in between the vision patterns for the sensors.

Ultrasonics Mount

After the ultrasonics mounting study was performed, a mount was designed out of PVC piping to hold all of the sensors on the front of the cart. This mount can be seen below.

Corresponding Drawings: Ultrasonics Mount Assembly

LiDAR Mount

A final decision on the LiDAR mount was made and can be seen below.

Corresponding Drawings: LiDAR 5 Degree Bracket, LiDAR Assembly, LiDAR Plate, LiDAR Mount Vertical Member

Drawings, Schematics, Flow Charts, Simulations

Emergency Stop

The team decided to go with the electrical option for the emergency stop as opposed to the more expensive mechanical one. As for the electrical emergency stop, a switch will be placed in the original golf cart circuitry which will, when pushed, send the necessary signal for the brake actuator to recognize and apply the brakes. The schematic for this can be seen below.

Steering Control Improvement

The team dove into the current design of the cart and recognized some potential to simplify the hardware and logic with regards to the level shifting circuit. This involved using a DAC instead of PWM while only requiring 1 DAC instead of 3. Additionally, this would reduce the number of Arduinos needed from 2 to 1. The schematic for the proposed improvement can be seen below.

The improved circuit would split the output and use op amps to scale the voltages. Additionally, this circuit will have voltage subtractor and non-inverting configurations. This will allow for the conversion of the single output from 0-3.3V to a differential output from 0-5V. Furthermore, a diagram was created in order to show the inputs and outputs for the one Arduino that would be used. This diagram can be seen below.

Manual Mode Throttle Override

Additionally, the team identified a possible problem area in the future when thinking about testing the autonomous functionality. The scenario that was thought through was when we are out testing and an Arduino accidentally fails and shorts out. This proposed override mode would allow for the cart to be quickly switched out of autonomous mode and placed into manual mode in order to be able to drive the cart the original way it was intended rather than pushing the cart back. The proposed design can be seen below.

Budget Information

From all of the chosen designs, a list of materials was developed along with their corresponding costs. This can be seen below in the purchasing plan.

Test Plans

Test plans for all of the team's engineering requirements were created and can be found here.

Design and Flowcharts

High Level Software Block Diagram

This flow diagram shows the relationship between all of the subsystems and logic throughout the people mover.

Mode Control Diagram

Additionally, a mode control diagram was created to display the different modes that the people mover has and how they are all interrelated. This can be seen in the diagram below.

Risk Assessment

Corresponding Document: Risk Register

Design Review Materials

Include links to:

Plans for next phase

A preliminary schedule was developed for the build phase of the people mover. This will be fine tuned and adjusted over the next couple of weeks to develop a good visual aid as well as an accurate plan for implementing the team's designs.

Key Milestones

A set of milestones were added to the schedule in order to set clear goals for design implementations. These can be seen below.

Documentation

One of the first tasks that our team will focus on is documentation. The team will review and verify all past documentation done by Phases II and I. The team will then update any documentation that is incorrect while creating any schematics, wiring diagrams, and/or drawings that are non existent. The goal for this task is to document the entire current situation of the cart while making any updates as the team makes changes to the cart.

Troubleshooting

Another important task that our team will focus on is troubleshooting. The team will develop a system diagnostics system which displays all subsystem information in order to quickly see what is happening when certain signals are sent through various systems. Additionally, the electrical team will look for any loose connections and other wiring problems and fixing them to ensure none of the problems are caused by these issues.

Redesign of Main PCB

An additional important task that members of our team will be working on is the redesign of the main PCB. Since the majority of Phase II's problems were seen because of this board, there is a chance to fix these issues as well as simplify the system to help ensure successful autonomous functionality.

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