Generally speaking, industrial robots are composed of three major parts and six subsystems.
The three major parts are the mechanical part, the sensing part and the control part.
The six subsystems can be divided into mechanical structure system, drive system, perception system, robot-environment interaction system, human-computer interaction system and control system. [3]
1. Mechanical structure system
From the perspective of mechanical structure, industrial robots are generally divided into series robots and parallel robots. The characteristic of the series robot is that the movement of one axis will change the coordinate origin of the other axis, while the movement of one axis of the parallel robot will not change the coordinate origin of the other axis. Early industrial robots all used tandem mechanisms. A parallel mechanism is defined as a closed-loop mechanism in which the moving platform and the fixed platform are connected by at least two independent kinematic chains, the mechanism has two or more degrees of freedom, and is driven in parallel. The parallel mechanism has two components, the wrist and the arm. The arm activity area has a great influence on the activity space, and the wrist is the connecting part of the tool and the main body. Compared with the series robot, the parallel robot has the advantages of large rigidity, stable structure, large carrying capacity, high precision of micro-motion, and small moving load. In terms of position solving, the forward solution of the series robot is easy, but the reverse solution is very difficult; while the parallel robot is the opposite, the forward solution is difficult, but the reverse solution is very easy. [3]
2. Drive system
The drive system is a device that provides power to the mechanical structure system. According to different power sources, the drive system can be divided into four types: hydraulic, pneumatic, electric and mechanical. Early industrial robots were hydraulically driven. Due to the leakage, noise and low-speed instability of the hydraulic system, and the bulky and expensive power unit, currently only large-scale heavy-duty robots, parallel processing robots and some special applications use hydraulic drive industrial robots. Pneumatic drive has the advantages of fast speed, simple system structure, convenient maintenance and low price. However, the working pressure of the pneumatic device is low, and it is not easy to accurately locate it, and it is generally only used to drive the end effector of an industrial robot. Pneumatic hand grip, rotary cylinder and pneumatic suction cup as the end effector can be used for medium and small load workpiece gripping and assembly. Electric drive is currently the most widely used driving method. Its characteristics are convenient power supply, fast response, large driving force, convenient signal detection, transmission, and processing, and can adopt a variety of flexible control methods. The driving motor generally uses step Into the motor or servo motor, the direct drive motor is currently used, but the cost is higher and the control is more complicated. The reducer matched with the motor generally uses a harmonic reducer, a cycloid reducer or a planetary gear reducer. Due to the large number of linear drive requirements in parallel robots, linear motors have been widely used in the field of parallel robots