Humanoid robots integrate such subsystems as servo control, battery management (BMS), sensors, AI system control and more. Size and heat dissipation requirements are challenging to meet when integrating these systems into the volume of a human shape while maintaining the smooth operation of the system.
To achieve a range of motion similar to that of humans, 40 or more servo motors and control systems can be deployed throughout the robot. Each motor requires high power density and precise control in a compact space. The motors are distributed through different parts of the robot’s body, such as the neck, torso, arms, legs, toes and hands. To simulate the freedom of human hands alone requires the integration of more than a dozen motors.
The power requirements of these motors depend on the specific functions performed. For example, motors driving a robot's fingers possibly only require a few amps, while motors driving a hip or leg can require 100 amps or more.
To coordinate these motors in the robot body while maintaining the stability of the system, demands high requirements. These can be met by increasing the speed of the motor control loop and the PWM frequency. A high-resolution motor current waveform also improves the operating efficiency of the motor and reduces motor heating.
For MOSFET-based servo drivers, however, the increase in PWM switching frequency brings some losses. When the switching frequency increases from 10kHz to 20kHz, in a MOSFET-based driver the overall loss increases by 20% to 30%, which is unacceptable for humanoid robots. This shortcoming can be overcome via use of GaN (more on this shortly).
By leveraging TI’s advanced gallium nitride (GaN), gate driver and precision sensing devices in your robot designs, you can increase productivity as well as enhance safety. To learn more read “Design safer, smarter and more compact humanoid robots with our system-level solutions.”
GaN Solutions
Gallium nitride (GaN) is a wide bandgap semiconductor that enables higher power density and more efficiency than traditional silicon metal-oxide semiconductor field-effect transistors (MOSFETs) and insulated gate bipolar transistors (IGBTs). GaN processes power more efficiently than silicon-only solutions, reducing loss in power converters and minimizing the need for added cooling components.
Thanks to integrated drivers, GaN technology can reduce the size of the power stage by more than 50% compared to MOSFET alternatives. With its low switching losses, GaN enables high-frequency pulse-width-modulation control in the hundreds of kilohertz range. Its ability to maintain efficiency without excessive heat helps address the demands of humanoid robot systems.
The reason why GaN can achieve such low switching losses is due to the characteristics of the GaN device. GaN devices have smaller gate capacitance (Cg) and smaller output capacitance (Coss), which results in switching speeds 100 times faster than Si-MOSFET. As the turn-off and turn-on time is shortened, the dead time can be controlled within a shorter range, such as 10-20ns, while MOSFETs usually require dead time of about 1us. The reduction of dead time results in lower switching losses.
Other improvements are needed to make it possible to create smaller, more flexible and energy efficient devices. Texas Instruments further reduces footprint area by integrating the FET and gate driver. This allows for a 4.4mΩ half-bridge + gate driver in a package of just 4.5 × 5.5mm. Integrating the GaN FET and driver in the same package also reduces parasitic inductances and optimizes switching performance.
The article “Application of GaN FET in Humanoid Robots” explains the various advantages of GaN technology in motor drives and shows how GaN can help solve the challenges faced by servo systems in humanoid robots.
Radar Sensing
Long-range capabilities, high motion sensitivity and privacy features make radar-based sensor integrated circuits (IC) a popular technology for position and proximity sensing designs. 60-GHz and 77-GHz radar sensors are replacing 24-GHz radar sensors, delivering higher resolution, improved accuracy and a smaller form factor. The 60-GHz and 77-GHz radar bands enable new applications such as object presence detection in industrial robotics and mobile robotics applications found in factories or homes.
A critical aspect of humanoid robots is the ability to detect and decipher a physical environment. The application brief “mmWave Radar Sensing and Sensor Fusion in Humanoid Robots” explores the benefits of millimeter wave (mmWave) radar sensors for navigation, identification, and integrating radar with camera sensors to enable sensor fusion in humanoid robots.
Summary
TI’s integrated circuits and reference designs help you create compact, efficient and fully protected systems for humanoid robots. Our analog and embedded processors enable improved motor-control performance and exceed IEC isolation and electromagnetic compatibility requirements.
By leveraging TI’s advanced gallium nitride (GaN), gate driver and precision sensing devices in your robot designs, you can increase productivity, enhance safety, and meet your cost and performance requirements.
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