The so-called collaborative robot is actually a type of robot that can work in a shared space with humans and interact closely with them. In short, it means being able to work together with humans. Collaborative robots are mainly composed of robot body, hollow torque motor, harmonic reducer, servo driver, and controller.

Characteristics of collaborative robots: 1. Lightweight. The smaller the robot, the better its safety. 2. Friendly. The surface and seams are smooth and flat, without sharp corners or gaps that are easily pinched. 3. Human machine cooperation. Having sensitive force feedback characteristics, the robot will immediately stop when the force reaches the set value. 4. Programming is convenient, and programming and debugging can be easily completed without technical background.

Collaborative robots with different structures: mainly single arm and dual arm robots. Single arm collaborative robots have only one arm, which is a common form of mechanical arm. Due to its flexible layout and simple control, it is widely used in various industry scenarios. Dual arm collaborative robots have redundant action space, are efficient and flexible, and are suitable for load applications that require interactive collaboration, or scenarios where multiple actions are completed in a limited space, such as the collaborative action of twisting bottle caps with both hands. Therefore, dual arm design will bring about increased costs and complexity in control.

Collaborative robots with different loads: Due to application scenarios and structural characteristics, the load of collaborative robots generally does not exceed 20kg. Usually, we define the load of light load collaborative robots as 3-10kg, the load of heavy load collaborative robots as 10kg or more, and the load of desktop collaborative robots as 3kg or less. Lightweight collaborative robots are commonly used in the consumer electronics, testing, medical, and service industries. Collaborative robots are commonly used in industrial scenarios such as assembly, handling, palletizing, and packaging, while desktop collaborative robots are used in work scenarios such as sorting, dispensing, coating, and automatic testing.

Collaborative robots with different forms of force perception: Force perception is the basic and important function for collaborative robots to achieve interaction, mainly divided into current loop, joint torque, six axis force/torque sensors, and electronic skin. Among them, the sensing form based on current loop is an early one. Directly obtain the motor currents of each joint of the robot through its servo system, and then calculate the output torque of each joint using the torque coefficient provided by the motor manufacturer. This method is both economical and simple, and is widely used in robot manufacturers. Due to the inability to obtain accurate external forces, it is often used for collision detection and simple drag teaching.

Collaborative robots based on joint torque sensors have been a research hotspot in recent years. A popular flexible joint is composed of a torque sensor, a multi turn encoder, and a single turn absolute value encoder, and the torque of each joint axis is directly output by the torque sensor. Compared with existing feedback methods, this method has higher accuracy and feedback frequency, and is easy to achieve compliant control of robots. It has been applied in precision assembly, polishing, surgery and other scenarios. However, using torque sensors will reduce the joint stiffness and trajectory accuracy of robots, and structural integration will also increase the difficulty of design and manufacturing.