A few days ago, Yushu G1 robot realized the somersault and kept its balance. This kind of somersault needs to overcome the asymmetric angular momentum distribution caused by rotation. The experimental data show that the peak angular acceleration in the air phase is 180 rad/s, and the landing impact force is 4.5 times its own weight, which requires the joint drive system to be explosive and lightweight! The localization rate of its core parts is over 90%, and the cost is 40% lower than that of imported parts. Congratulations to China enterprises for overtaking in corners by reducing costs through electric drive! Today, Heketai will explain to you the module structure of humanoid robot and how the MOS tube involved completes the energy conversion for robot cartwheel.

Composition of robot joint module

The joint module of humanoid robot is developing in the direction of "high integration, high dynamics and low time delay", the core of which lies in the cooperative optimization of motor, reducer and sensor. The joint module has eight core components (as shown in the figure), including the absolute encoder at the motor end, the temperature sensor of DC driver, the multi-turn absolute encoder at the output end, the friction brake holder, the frameless torque motor, the torque sensor and the precision harmonic reducer.

The servo system is responsible for driving the movement of the robot, which consists of servo driver and servo motor. Among them, the servo driver is responsible for position, speed, torque and other controls; Servo motor is an engine that controls the operation of mechanical components in servo system, and converts the received voltage signal into torque and speed to drive the controlled object.

MOS tube application

1. Motor control:

The hip and knee joint output peak torque within 10ms at the moment of somersault off the ground, which requires high instantaneous power. As the core drive of the motor, MOS should have low on-resistance (RDS(on) <1mΩ) and high current tolerance (> 500). Moreover, the dynamic response demand of joint motor needs to shorten the control period to millisecond level, and the switching frequency of MOS needs to be above 100kHz to meet its fast switching response demand. Finally, heat dissipation and reliability are also very important for motor control.

2, power management:

When the battery flips, the instantaneous discharge power can reach 50kW, and the current conversion efficiency can be improved by synchronous rectification MOS switch. Through the intelligent switch matrix of MOS, energy can be preferentially distributed to key joints to ensure the continuity of action. When the bus voltage fluctuates (for example, 20 V), TVS-MOS integrated protection can quickly turn off the MOS tube, which can prevent overvoltage from breaking through the drive circuit.

3. Signal guarantee:

Low threshold MOS is used in IMU and torque sensor, which can reduce acquisition noise and ensure feedback accuracy. The sensor fuses data through LVDS interface to meet the real-time control requirements.

Selection recommendation

Compared with imported products, the on-loss of the self-developed MOS transistor of Heketai is reduced by 15%. We recommend the following MOS transistors with good performance in terms of motor control, power management and signal guarantee. See the following figure for detailed parameters: