Project Overview
A US-based robotics startup needed a compact, high-efficiency BLDC motor controller with sensorless Field-Oriented Control (FOC) for their collaborative robot arm series. InnovChip developed the complete solution — from FOC firmware algorithm optimization to custom PCB design and thermal management.
Client
Industry: US Robotics Startup (Silicon Valley)
Project Duration: 16 weeks
Budget: $55,000
Industry
Robotics / Collaborative Automation
Challenge
- Required sensorless FOC with smooth torque down to near-zero RPM
- Board size constrained to 60mm × 40mm to fit inside robot joint housing
- Peak current of 30A continuous, 50A transient in a PCB-only design
- Thermal management — keep MOSFET junction temperature below 105°C at full load
- CANopen communication for multi-axis synchronization
- Low audible noise requirement for collaborative robot environment
- BOM cost target under $25 at 1,000-unit volume
Solution
- MCU: STM32G4 (Cortex-M4 with CORDIC and FPU for FOC math)
- Driver: Integrated 3-phase gate driver with current sense amplifiers
- MOSFETs: 60V N-channel MOSFETs in parallel (low Rds(on) = 3.2mΩ)
- Control: Sensorless FOC with sliding mode observer + PLL for rotor position estimation
- Switching: 40kHz PWM with adaptive dead-time compensation
- Communication: CANopen CiA 402 drive profile for velocity, position, and torque modes
- PCB: 4-layer design with optimized thermal vias and copper pour on bottom layer for heat dissipation
- Protection: Over-current, over-voltage, under-voltage, over-temperature with configurable thresholds
Technical Details
| MCU | STM32G474 (Cortex-M4 @ 170MHz) |
| Voltage Range | 18-48V DC |
| Continuous Current | 30A (with forced air cooling) |
| Peak Current | 50A for 10 seconds |
| PWM Frequency | 40kHz |
| FOC Loop Rate | 20kHz current loop, 10kHz speed loop |
| Position Sensor | Sensorless (back-EMF observer) |
| Communication | CANopen (CiA 402), UART, I²C |
| Board Size | 60mm × 40mm × 12mm |
Result
- Motor efficiency reached 92% at rated load (10% better than client’s previous vendor)
- Sensorless FOC achieved smooth torque control down to 5 RPM (electrical)
- Passed thermal validation: MOSFET junction at 98°C under 30A continuous load at 40°C ambient
- CANopen synchronization achieved < 10μs jitter between axes
- BOM cost: $23.50 at 1,000-unit volume (under target)
- UL 60730-1 functional safety pre-assessment completed
- Integrated into client’s cobot arm, enabling 6-axis coordinated motion