Cyclopolis Mobile (bike-mounted) sensor kit

As part Chania’s VS2, both public (Chania’s bike sharing system) and private bicycles were mounted with customed mobile sensor kits to measure pollutants.

Parameters measured by the sensor:

• Particulates of various sizes (PM1, PM2.5, PM10) from sources like smoke, dust, pollen, metal and organic particles, using the PMS5003 sensor. The sensor uses laser light scattering principle to measure the value of dust particles suspended in the air. Sensor provides precise and reliable reading of PM2.5 value.
• Temperature and relative humidity using the SHT35 sensor
• Noise pollution using the Waveshare sound sensor

Particulate matter data are enriched with temperature and relative humidity data from the corresponding sensor, which is also located into the sensor kit. All available data is geolocated to trace possible pollution hotspots. The sensory kit is designed  to be mounted on public bikes and for this reason it is light, reliable and with a low need for power.

The data is acquired:

• When the bicycle is docked at any of the four bicycle stations of Chania: every hour
• When the bicycle is moving: every minute

What were the technical need and the market need?

There is extensive research on how exposure to air pollutants has been linked to various acute and chronic health issues, such as the increased risk of cardiovascular disease and respiratory infections, dementia, Parkinson’s disease, cognitive impairment, kidney disease, diabetes, and issues with the reproductive system. However, air pollution levels can vary significantly over short distances, particularly in urban areas such as Chania, and near emission sources.

Therefore, measurements on local pollutants is crucial to understand and develop adequate mitigation actions. However, sensors to measure local pollutants (like PMx and noise) were (and still are) expensive: a multitude of sensors in a dense network is needed, and to make the matter even worse, communicating data of such a size can also be costly. In the last few years, technological developments have increased the reliability of low-cost sensors, and facilitated IoT solutions through geolocation and advanced data transmission techniques (eg GPS, LoRa networks),  while at the timesensor costs and telecom rates keep falling , and machine learning techniques have made their processing and analysis of large data pools more cost effective.

Taking these factors into account, Cyclopolis considered that:

• affordable solutions for measuring effectively on the local level were now possible.
• shared micromobility fleets now flood the streets of modern urban environments
• the severe effects of poor air quality and noise on human health and well-being have been broadly recognised

Cyclopolis therefore proposed to design a mobile (bike-mounted) low-cost sensor kit to measure local air pollution levels.

How was it developed?

The sensor kit needed to be designed to be mounted on public bikes; it had to be light, reliable and with a low need for power. It is based on a Cyclopolis’ proprietary PCB. The digital ecosystem of the kit has 3 main components:

• A protocol, supporting Wi-Fi communication
• A Front-End server, implementing the network service, the visualization service and the API for data ingestion
• A Back End server, implementing the database.

Data collection

A database stores the data coming from the different registered devices ; for VARCITIES implementation Cyclopolis initially started with a NO-SQL database (InfluxDB), but during the test phase, shifted to another database (PostgreSQL).

The collected data can be shared with APIs. For the purpose of VARCITIES, the collected data are fed into VARCITIES Health & Well-Being Platform.

Telecommunication

Mindful of cost effectiveness, Cyclopolis’ mobile sensor-kits is designed and programmed so that it locally stores the data collected during a bike ride and, as soon as the bike approaches the bike station, it transmits the collected data, using the pre-configured WiFi Network provided by the respective bike station.

Power management

Cyclopolis tested several power harvesting solutions (solar cells, supercapacitors), But, the power needs of the kit were such that the size of the necessary solar cells (50×50 cm) was such that it was a stopper considering the importance of keeping the size of the kit small enough to mount on any bicycle. Consequently, low power techniques were implemented and the solution of rechargeable batteries, mounted on the sensor kit’s casing, has been selected.

Casing 

After exhaustive testing taking under consideration the bike dimensions, weather conditions, optimal functionality, maintenance and marketability in order to finalise mounting and positioning on the bike, Cyclopolis finalised the sensor kit design, its 3D printing method and its materials.

Data reliability

Although sensors come calibrated, Cyclopolis undertook considerable further calibration efforts, measuring side-by-side with reference stations bearing expensive sensors that measure the same pollutants in an effort to analyse and compared collected data over an extensive time period. From this process Cyclopolis concluded that data did need calibration due to considerable differences between the data produced by expensive and those produced by cheaper sensors. However, given that the deviations were systematic, after long analysis and tests, Cyclopolis inferred the respective calibration algorithms.

In effect, we consider the data produced by Cyclopolis mobile sensor kits as reliable as those produced by any reference station.

Market potential

Any owner of public micro-mobility means is a prospect customer. Specifically, public entities looking to improve public health, advertise its good air quality level. For private entities (e.g. bike sharing solutions providers or operators, real estate developers), it can produce valuable data that can be either sold (raw or processed) or used for marketing purposes.

Patents pending for both the mobile sensor-kit and the data collection and storage method.