Analysis of the advantages of RV reducer and harmonic reducer for robots

Analysis of the advantages of RV reducer and harmonic reducer for robots
Why do robotic arms use reducers?

Robotic arms typically require repetitive actions, which places high demands on their positioning accuracy and repeatability.

1. Reduce speed, increase torque, and achieve better operating characteristics; When the load is large, the output torque can be increased within an appropriate speed range by using a reducer;

2. The reducer can reduce the moment of inertia and control the start stop and speed change in a timely manner. Increasing the torque through the reducer is equivalent to increasing the input power, which can reduce the power required by the input motor (in situations where speed regulation is needed);

3. The reducer has a protective effect on the motor during driving. During operation, the reducer bears a large torque, and if it is directly borne by the motor, it may cause damage to the motor. When the overload is very large, the reducer will be damaged first, and the reducer only needs to be replaced with spare parts to be reused, with relatively low cost. If the motor is directly damaged, the repair process will be relatively slow and the cost will be higher; Compared with general reducers, robot reducers require characteristics such as short transmission chain, small size, high power, light weight, and easy control.

There are two main types of reducers widely used in articulated robots: RV reducers and harmonic reducers.

Introduction to RV reducer

RV reducer is a transmission mechanism developed on the basis of traditional cycloidal pinwheel and planetary gear transmission devices. With the development of the market and technology, it has become the core component of joint drive on industrial robots, especially medium and heavy-duty industrial robots. RV reducers are used for the leg, waist, and elbow joints of robots with high torque (usually divided by 30KG, RV is used for all six axes above, and RV is used for axes 1, 2, and 3 below). Compared to harmonic reducers, RV reducers have the advantage of higher fatigue strength, stiffness, and lifespan, unlike harmonic drives where the motion progress significantly decreases over time.

Advantages and disadvantages of RV reducer and harmonic reducer
Harmonic reducers have a large single-stage transmission ratio, small size, small mass, high motion accuracy, and can work normally in enclosed spaces and medium radiation conditions. Compared with general reducers, harmonic reducers can reduce their volume by 2/3 and weight by 1/2 when the output torque is the same, which gives them strong advantages in robot arms, wrists, hands and other components.

RV reducers have good rigidity, strong impact resistance, smooth transmission, and high precision, making them suitable for applications with medium and heavy loads. However, RV reducers need to transmit a large amount of torque, withstand significant overload impacts, and ensure the expected working life. Therefore, relatively complex over positioning structures are used in the design, and manufacturing processes and cost control are difficult. There are no elastic deformation force elements inside the RV reducer, so it can withstand a certain torque. The bearing of the RV reducer is its weak link, and it is easy to break through the bearing capacity limit when subjected to force, resulting in abnormal wear or breakage of the bearing. This problem is more prominent during high-speed operation, so the rated torque input speed of the RV reducer decreases significantly.