Team Name
Under Pressure
Timeline
Spring 2019 – Summer 2019
Students
- Nathan Merrill
- Carlos Meza
- Aaditya Purani
- Vijit Singh
- Colby Stauss
Sponsor
Social Knowledge LLC.
Abstract
This projects goals was to create a prototype, or proof-of-concept, of a IoT TPMS solution that is targeted towards a US consumer market. Social Knowledge LLC has over 25k customers that already use their app, RVLife, to plan there vacations and trips. This user base however is vulnerable to injury, because not all users are checking RV tire pressure. By using a few applications and hardware, communicating over various mediums, we aimed to create a solution that can address the needs and safety of this user base. Our solution explored multiple mediums, SoC, and software stacks. Mediums we finalized on included BLE and 315MHz RF. The SoC we explored included boards from NXP, Raspberry Pi, TI, and Infineon, but we finalized on a NXP and Raspberry Pi based solution. The software stacks we explored were limited by the SoC choose, and was a influencing matter when deciding our hardware. Our project was successful in creating this proof-of-concept design and reliability alerts the user RVlife application if tire pressure or temperature is abnormal. We also were able to create a prototype housing for our sensor and hub.
Background
Similar to cars and trucks, RVs are susceptible to loosing pressure in their tires. This can lead to blowouts which can damage property and in the worst case cause death. To prevent this, sensors are placed in the wheel assembly or on the valve stem to monitor the tire pressure and temperature. The reliability of these sensors is vital to alert the operator of any impending danger.
RV Life has sponsored our team to create a better, more reliable tire pressure and temperature monitoring system for trailers and RVs. There are many solutions currently on the market, each with their own flaws. Our goal as a team is to combine the benefits of these sensors while reducing the negative side effects. We aim to do this in conjunction of maintaining a low production cost.
One of the major problems with the current solutions is the delay on transmitting pressure information. To increase the battery life of the sensor the transmission time of some sensors can be as low as once every five minutes. A blowout can occur in under three minutes from gradual pressure loss, creating an issue of reliability in these sensors.
Most tire pressure monitoring systems for RVs and trailers today only measure pressure. This is acceptable for constant temperatures. Temperature affects the pressure of the assembly. Cooler temperatures in the morning can trigger the warning light to go off giving a false negative. If the tires are then inflated to turn off the warning light before driving, the pressure may increase beyond a safe range when the tires heat up from driving. By incorporating a temperature sensory one can effectively create a safe range for the pressure in the tire and only alert the operator when necessary. A temperature sensor is also an effective warning system to detect an immanent blow out. Just prior to a tire failing, the temperature will rise drastically from the friction of rubbing sidewalls. Detecting this can prevent damage to people and property.
The reliability of these sensors come into question frequently. Some sensors have a very limited range of effective data transfer. If data is lost or corrupted, no new signal is received. This can delay the system of warning the operator of any change in pressure; In some cases, up to a five minute delay.
Many displays implemented in these TPMS solutions are not user friendly. Most require an addition display on their dash to transmit the data. These displays can be confusing to set up and difficult to read. Without a quality user interface, many operators will chose to not use a system all together. System installation can also be difficult to the user. Some sensors require special tools to lock them in place. If the tool is lost, a replacement tool must be ordered to remove the faulty sensor.
Project Requirements
- 0-66 C +/- .1 C
- 0-150 PSI +/- .1 PSI
- Range of 30-40m
- Low power, sleep mode
- RF transceiver
- Under $10 in volume (10k+ units)
- RF transceiver, BLE enabled
- USB for power
- Low cost
- iOS should integrate to existing RVLife app
System Overview
There are three main parts to the underpressure tpms system. This includes the sensor module, hub and the mobile phone. The sensor device and the hub communicates using 315 Mhz RF Communication and the hub passes on the sensor information to the mobile device using Bluetooth Low Energy (BLE).
The sensor device is composed of three main parts, this includes the one SoC that powers the device, a battery and a housing. The SoC we are using it FXTH87, this module contains the computer, processor, memory, flash and RF Module. The housing ensures that we are able to properly read from the pressure valves.
The Hub is composed of two main parts, one is RF module and the second is raspberry pi zero w, with a BLE integration. The operating system on the ZeroW is written in python and bash scripts and runs on the raspbian operating system at startup. We aim to use a generic RF module, but couldn’t get it done. Hence, we fallback to the proprietary NXP RF module.
The mobile app, through BLE, communicates with the hub. The app displays temperature and pressure of each tire, based on the tire ID.
Results
We were able to meet all our requirements. We had to use a propitiatory RF Module instead of generic RF Module. We were also not able to test battery life due to time constraints, but our estimations indicate that it should meet the requirements.
demo videos go here
Future Work
Integrate generic RF Module instead of propitiatory RF module. Create housing that can house a battery with the sensor. Create housing for the hub. Allow for Over the Air (OTA) updates. For the application, allow more users to look at and interact with the data. Also, to provide more user control on the readings.
Project Files
Project Charter (link)
System Requirements Specification (link)
Architectural Design Specification (link)
Detailed Design Specification (link)
Poster (link)
References
Any references go here, properly formatted
