The important position of rotary actuators in robots

Parts of the rotary actuator

The current mainstream humanoid robot rotary actuators mainly consist of reducers (harmonic reducers or planetary reducers), motors (torque motors), controllers, encoders (position sensors), force/torque sensors and bearings, which are the core of the rotary actuator. parts.

The flexibility of the joint module allows the rehabilitation robot to perform single-joint or multi-joint training, and dynamically adjust the motion trajectory and resistance strength according to the patient's physical condition to meet the needs of different patients.

1，Rotating joint reducers are mainly harmonic reducers, and planetary reducers have room for substitution. The harmonic reducer has the advantages of small size, low mass, high motion accuracy, and can work normally in confined spaces and medium radiation conditions. Therefore, it is more suitable for humanoid robot actuators than other reducers such as RVs. The price of precision planetary reducer is lower than that of harmonic reducer, and it has stronger load-bearing capacity and efficiency. Using planetary reducers instead of harmonic reducers on joints with lower precision requirements can reduce robot production costs

2，The motor system is mainly frameless torque motor. The frameless torque motor has no shaft, bearings, housing, feedback or end cover. It only contains a stator and a rotor. The rotor is a hollow structure to facilitate the internal wiring of the joint. One of the important features of the torque motor is its compact structure, small size, and light weight. It can achieve "zero transmission chain", no mechanical friction, 365-day maintenance-free, and long-term accuracy. Therefore, torque motors have broad application prospects in robot joints, medical robots, sensor universal joints, and UAV propulsion and guidance systems.

3，Optical encoders and magnetic encoders each have their own advantages, and the dual encoder solution can improve control accuracy. Encoders are sensors that encode motion parameters such as rotation angle, linear displacement, and speed. The design of humanoid robots must take into account both the accuracy of movements and the ability to withstand the harshness of the working environment. Robots using optical encoders can achieve higher movement accuracy, while robots using magnetic encoders can adapt to more complex working environments. In the dual-encoder solution, the motor-side encoder is used to drive the motor, and the output-side encoder is used to measure changes in output position. Therefore, the dual encoder solution can monitor the speed and position of the motor and gearbox side at the same time, and can control the joint motion trajectory with higher precision than a single encoder.

4，Bearings are distributed in the joint joints, reducers and motors of the robot. Deep groove ball bearings and four-point contact bearings are usually used at linear joints. In the harmonic reducer, both a rigid bearing and a flexible bearing are required. The rigid bearing is generally a crossed cylindrical roller bearing, and the rolling elements are cylindrical rollers distributed in raceways arranged vertically. The planetary reducer has a compact structure and various shapes, so the bearings are widely used, including deep groove ball bearings, angular contact ball bearings, tapered roller bearings, stamped needle roller bearings and double row angular contact ball bearings, etc.