BLDC-motor driven E-Skateboard (TAPAS powered)

About TAPAS

The Siemens SDI TAPAS is a 48V GaN (Gallium Nitride) based three phase inverter board with onboard filters, expected to change the way people approach power electronics. The design choice allows for a high switching frequency, while producing a smooth output waveform. The unique combination of high bandwidth and smooth output makes TAPAS to some degree universal, giving rise to applications ranging from robotics to power conversion, making the inverter truly software configurable. The TAPAS board is designed as an educational platform that addresses enthusiasts as well as experts at universities and in the industry. The development of the TAPAS board is community driven. Together with open-source code examples and extensive documentation we made TAPAS as accessible to the community as possible.

Why an E-Skateboard?

E-skateboards are a part of a very interesting segment compromising e-bikes, e-skateboards and e-scooters. It is a market that has a lot of potential for a low voltage converter platform like TAPAS. We created our own version of an electric skateboard using TAPAS and components readily available in the market. The firmware for the project was developed by adapting the stock motorware API and a very good online support platform. We believe that the true capability of our board is very well demonstrated with the skateboard.

First Version

For the first version of the TAPAS E-Skateboard a normal skateboard available in every market was used. One of its rear wheels is connected to a 3 phase motor through a belt drive. The motor is controlled by a TAPAS board. The first version of the skateboard is programmed for sensorless field orientation control (with PWM frequency @ 90kHz and current control frequency @15kHz). Further, a simple speed controller running at constant RPM and a hardwired start/stop function is implemented by interfacing a switch to the GPIO pins. The software is based on InstaSPIN-FOC developed by Texas Instruments.

Second Version

Highlights

• Operates at 24V with LiPo batteries
• Made from Commercial Off the Shelf Components
• Sensorless FOC using InstaSPIN from Texas Instruments
• Good dynamic response with torque control
• Can support weights up to 100kg
• Regenerative braking
• Wireless bidirectional control

This second version of the TAPAS powered E-ekateboard is designed to consume less power and is more energy efficient than other skateboards available in the market. The skateboard consumes <50W in no load conditions and <500W under loaded conditions which should lead to more battery life. It is fully sensorless and is also able to start from any rotor position at near full load conditions.

Modifications on the TAPAS Board

Because, in the first version, the motor did not start smoothly from all rotor positions and the skateboard vibrated back and forth when starting, in this second and final version, the PWM frequency was lowered to 45kHz. Therefore, the on board LC filters are disabled as their cut off frequency is around 90kHz. Further, the capacitors connected to each phase output are removed and heat sinks are attached to inductors. Similiar heat sinks are also mounted on GaN FETs on the bottom side of the PCB for cooling purpose. Also, a reasonably big electrolytic capacitor was added to the input in order to augment the on board DC Link capacitor.

Technical Details

• 1x Turnigy SK3 5055 280Kv Outrunner motor from hobbyKing.com connected through a belt drive to one of the wheels
• 2x 3S LiPo batteries (11.1 V each)
• 1x TAPAS configured at 45kHz PWM modifying the output filters
• 1x Wirless remote from hobbyKing.com configured through eCAP

Happy skateboarding! :)