The Sosaley Technologies two-wheeler ISG (STWISG) is a full-featured control system developed for and in conjunction with Lucas-TVS.
Tested extensively on realistic loads in the labs of Lucas-TVS, the STWISG is capable of controlling PMSM motors with a high level of accuracy.
STWISG works with three sensors. One is a hall sensor to read data for the PMSM motor, the second a reluctance sensor to read the vehicle speed, and the third is a temperature sensor.
Though the STWISG works in 5 modes, it is built as 3 major functional blocks. In the first block, we built a powerful and accurate power supply to deliver power from the battery to all the electronics including the sensors.
In the second block, the STWISG acts as a power generator. It takes energy coming from the PMSM motor, modulates and cleans the signal, converts AC to DC, and feeds the energy back to the battery. The objective here was to maximize energy regeneration. Sosaley and Lucas-TVS have together worked on the STWISG to suit Indian conditions, and optimize the regeneration by delivering 10-15% more energy to the battery than what was felt possible. This way, the two-wheelers that use STWISG will be able to drive a long distance and offer more ‘fuel’ efficiency.
The third block is the starter/motor mode. In this the objectives were simple:
- Start the motor quickly without and crank the IC Engine with efficiency close to 95%.
- Optimised switching to control alternator output and not overcharge the battery.
- Deliver additional torque instantly when needed to improve fuel efficiency.
All these were achieved well within the pre-determined parameters. Sosaley developed all the drivers needed as well as the signal modulation and smoothening logic.
Using three Hall Sensors to read motor data, the controller uses a six-step commutation logic for exact control of the motor. Ta, Tb, and Tc timer values are fed into a PWM register and a graph analyzed to study the effectiveness of the controller. We have managed to achieve the accuracy needed in terms of the gaps between the timings and a perfect sinusoidal wave.
The motor controller is linked to a CAN/LIN bus. The CAN/LIN interface sends data to the ECU, displays current status, and gets control instructions. The motor controller is also designed to use GPS and other modes for cloud-based information flow.