Introduction

FSAE vehicles, such as the QUT Motorsport vehicle, use four motors, one in each motor hub. This enables better delivery of torque and torque vectoring. As a result, these already small vehicles now have 4 relatively low powered motors. There are some existing solutions used by teams, such as the Bucher 60kW dual control unit, the Sevcon HVLP 20, and the VESC 100/250. However, these drives are made for auxiliary pumps and fans in larger buses and tractors, not meeting the packaging or performance requirements, or in the case of the VESC, designed for a skateboard, and so lacks the isolated safety requirements.

The goal of this project was to design a robust, power-dense motor control solution that can fit into small vehicle spaces. The solution should minimise unnecessary complexity, focusing on delivering working and validated hardware

Initial Design

Refer to thesis

Solution

The final device assembly is shown below, with control board on top, interface breakout, gate drives and power PCB on the bottom. Aluminum section has been used as a heatsink for initial testing.

Low Voltage (600V) Testing

The goal was to perform double pulse testing to validate

• Turn on and turn off characteristics. Tuning of the on/off gate resistors on the drivers
• Turn on and turn off delays in digital and analog systems
• Deadzone calibration
• Phase current shunt calibration
• Delay in delta sigma modulator phase current from real current

Test Setup

Testing at hazardous voltages, an isolation barrier between the test device and test interfaces was important. A basic enclosure was used as a physical barrier. An emergency stop was present to turn off the supply and connect a dicharge resistor across the capacitors.

Scope Connections

The below shows the test setup.

• The co-located control board during testing enables the MMCX +/- 50V probe to connect to the gate MMCX connector.
• VDS 0.200" probe connection connected to pre-made lead.

A close up of the connection shows the MMCX connector, as well as an additional differential probe used to measure the delta sigma modulator output.