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Evaluation of the Design of a GaN-Based Motor Drive Optimized for Precision Motion in Humanoid Robots

Evaluation of the Design of a GaN-Based Motor Drive Optimized for Precision Motion in Humanoid Robots

GaN Talk – Francesco Musumeci Feb 11, 2025

Why Humanoid Robots Demand Precision Motor Drives

As humanoid robots become essential tools across industries like healthcare and logistics, precise motor control for intricate movements, such as wrist and toe articulation, is critical. The EPC91104 motor drive inverter reference design is tailored for compact, high-precision motor applications.

EPC91104: Optimized for Humanoid Robotics

The EPC91104 is a 3-phase BLDC motor drive inverter optimized for humanoid robotic applications. With its compact dimensions (81 mm x 75 mm) and ability to handle input voltages from 14 V to 80 V, it provides unparalleled performance for wrist and toe motor drives.

EPC91104 – 14 A<sub>RMS</sub> 20 A peak 3-Phase BLDC Motor Drive Inverter Board
EPC91104 – 14 ARMS 20 A peak 3-Phase BLDC Motor Drive Inverter Board

Featuring the EPC23104 ePower™ Stage IC, this solution offers:

  • Wide Voltage Range: Operates between 14 V and 80 V, making it compatible with various battery systems
  • High Current Handling: Delivers up to 15 ARMS steady-state and 20 ARMS pulsed current, ensuring robust motor operation
  • Precision Sensing: Equipped with high-bandwidth (120 kHz) current and voltage sensing for all phases, enabling accurate control and diagnostics
  • Compact Design: Ideal for wrist, finger, and toe motors in humanoid robots
  • Advanced Protection Features: Includes overcurrent and input undervoltage lockout to safeguard both the board and connected systems to enhance reliability
  • Versatile Control Options: Compatible with leading controllers from Microchip, Texas Instruments, and STMicroelectronics, simplifying integration

By integrating a highly optimized PCB layout and low-distortion switching, the EPC91104 reduces torque ripple and motor noise, ensuring smooth and quiet operation.

The Advantages of GaN Technology for Robotics

Precision motion is critical for humanoid robotics, particularly in small joint actuation. The EPC91104 excels in these applications by leveraging enhancement-mode gallium nitride (eGaN®) technology, which surpasses traditional silicon-based solutions in terms of efficiency, size, and switching speed.

GaN power devices offer several advantages over silicon-based counterparts:

  • Higher Efficiency: Reduced power losses translate to less heat generation and longer operational lifespans
  • Compact Size: Smaller devices allow for more compact designs, a crucial factor in robotics
  • Faster Switching: Faster response times enable precise motor control, critical for applications such as robotic toes, which require quick adjustments to maintain balance and fluid motion

Meeting the Growing Demands of the Humanoid Robotics Market

The humanoid robot market is projected to grow exponentially, driven by advancements in AI and the increasing demand for automation in aging societies. Precise motor control for intricate movements, such as wrist rotation and toe articulation, is essential for these robots to perform human-like tasks effectively.

The EPC91104 excels in motor drive applications where size and precision are paramount. For example, robotic toes must provide stability and dynamic movement, while wrists require dexterity and load management. The EPC91104's low distortion switching reduces motor audio emissions and torque ripple, ensuring smooth and silent operation—critical for robots working in environments like hospitals or offices.

Experimental Validation: Proven Performance

The EPC91104 has undergone rigorous testing to validate its performance under practical conditions. Using a 48 VDC power supply and switching at 100 kHz with 50 ns dead time, powering a 3 kW motor, the board delivered 11 ARMS steady-state phase current without a heatsink under natural convection. With a heatsink and natural convection the board delivered 15 ARMSsteady-state and a pulsed current up to 26.5 ARMS.

Thermal Management for Enhanced Reliability

The EPC91104’s thermal design, supported by optional heatsinks and thermal interface materials, ensures reliable operation even under high loads. When operated on a motor bench at an ambient temperature of 22°C, with a 48 VDC supply and natural convection, the EPC91104 can deliver 11 ARMS per phase without a heatsink and 15 ARMS per phase with a heatsink attached, with a temperature rise below 75°C from the GaN IC case to ambient. Results of testing shown in figure 1. Furthermore there is an online thermal calculator tool to help engineers simulate and optimize the thermal performance of their specific designs.

EPC91104 eGaN IC temperature (*) increase vs. the ambient temperature (22°C). Measurements taken at various PWM frequencies
Figure 1: EPC91104 eGaN IC temperature (*) increase vs. the ambient temperature (22°C). Measurements taken at various PWM frequencies

Expanding the Robotics Solution Portfolio

For higher-current applications, such as elbow and knee motors in humanoid robots, the EPC9176 reference design complements the EPC91104. Together, these solutions enable engineers to cover a full range of motor drive requirements, from delicate finger movements to robust knee articulation.

Conclusion: Enabling the Future of Robotics

The EPC91104 represents a significant step forward in enabling precise, efficient, and compact motor drives for humanoid robotics. With its innovative design and GaN technology at its core, this reference design empowers engineers to develop robots capable of lifelike movements and advanced functionality.

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