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PBSC needed a system to monitor trips made with its fleet of Citi Bikes in New York. The company asked Spiria to undertake a proof of concept and develop the architecture of an on-board GPS system.
- On-board systems
Maximum number of bikes able to simultaneously send data to the kiosk.
Technical problems solved with 500 hours of expertise in on-board systems.
Stations, or 7,000 bikes, potentially using the on-board system.
- Proof of concept
- Energy efficiency
Spiria developed an energy-efficient on-board system for PBSC to collect precise GPS data on every trip. Data is transmitted wirelessly to the kiosk every time a bike is parked at a station. The kiosk then forwards the data to a central server for processing. Thanks to this technology, PBSC was able to gain a better understanding of bike-share users, quantify environmental gains provided by the service, and enhance the Citi Bike network.
PBSC needed on-board systems expertise to demonstrate the technical feasibility of its concept and to develop a plan for the physical platform to support GPS data acquisition. It was crucial to get these right, as the tool had to:
- Provide quantitative data on the environmental gains yielded by the service as tangible proof of Citi Bike’s environmental benefits, which would help obtain new funding.
- Incentivize users by providing them with personnalized Citi Bike data: calories burned, environmental footprint, etc.
The proof of concept covered four key points.
Data integrity had to be comparable in two different environments: open, and “urban canyon” (buildings, obstacles, etc.)
The on-board GPS systems had to be able to transfer trip data to the radio frequency module in station kiosks.
There needed to be a data transfer logic and protocol to optimize available power when bikes were parked.
Data from bikes parked in the furthest spots had to reach the station kiosk despite the distance.
Energy generated by the dynamo from pedaling activates the bike-mounted on-board system to collect trip data.
Every time the bike is parked at a station, trip data is sent to the radio frequency module in the station kiosk. The GPS system has three minutes of residual energy to send this data.
The radio frequency module gathers and stores data from each bike. It then forwards it to a central server.
The central server receives the data through a 3G cellular network. It then synchronises data to map out bike trips and produce usage statistics.
It contains the Atmel ATmega128RFA1 microcontroller which executes the SNAPpy source code.
The main on-board GPS system component.
Spiria went to great lengths to optimize this component. For example, we modified the SNAPpy script to improve data sequencing, which reduced the size of data packets and optimized data collection and transmission. Energy efficiency gains are achieved through the data transmission protocol.
Further, the SM200 contains a radio frequency antenna that sends data to the kiosk module thanks to a protocol optimized by Spiria.
Other components of the on-board GPS system:
store energy produced by the bike-mounted dynamo to run the GPS when moving and send data to the kiosk when parked.
reads, writes and records data from the microcontroller.
Radio frequency moduleIn the station kiosk
receives data recorded by the GPS. An external antenna on the kiosk’s radio frequency module ensures reception of data sent from bikes parked in the furthest spots.
Radio frequency module
Receives bike data collected when moving and transmitted when parked. Data is stored in a file which, when complete, is sent to a central server.
Microprocessor Atmel AT91SAM9G20
Spiria modified code logic for the microprocessor to track the number of GPS points recorded and time needed to receive them. This modification was crucial in proving feasibility.
It receives data sent by the bike’s on-board system through the external antenna. Its microcontroller, also an Atmel, sends the data to the ARM microprocessor.
Spiria assessed the technological potential of components to meet the following requirements:
- Ability to collect accurate GPS data every 6 seconds (longitude, latitude, bike ID, schedule, etc.)
- Ability to maintain data integrity and track itineraries regardless of environment (clear or obstructed).
- Ability to optimize available power when bike is parked and relying on residual energy previously accumulated through pedaling.
- Ability of kiosk radio frequency module to handle large volumes of data when several bikes are simultaneously parked at the station.
The system development plan and proof of concept allowed PSBS to proceed with the large-scale implementation of an electronic device crucial to the development of its urban mobility solutions.