Team Vision for Detailed Design PhaseFor 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 StudyThe 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.
Ultrasonics Mounting StudyThe 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 MountAfter 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 MountA final decision on the LiDAR mount was made and can be seen below.
Drawings, Schematics, Flow Charts, Simulations
Emergency StopThe 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 ImprovementThe 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 OverrideAdditionally, 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 InformationFrom 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 PlansTest plans for all of the team's engineering requirements were created and can be found here.
Design and Flowcharts
High Level Software Block DiagramThis flow diagram shows the relationship between all of the subsystems and logic throughout the people mover.
Mode Control DiagramAdditionally, 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.
Corresponding Document: Risk Register