Generally speaking, industrial robots consist of three parts and six subsystems.
These three parts are mechanical part, sensing part and control part.
The six subsystems can be divided into mechanical structure system, driving system, sensing system, robot-environment interaction system, man-machine interaction system and control system.
1. Mechanical structure system
From the mechanical structure, industrial robots are generally divided into serial robots and parallel robots. The characteristic of serial robot is that the movement of one axis changes the coordinate origin of the other axis, while the movement of one axis of parallel robot does not change the coordinate origin of the other axis. Early industrial robots all used serial mechanisms. A parallel mechanism is defined as a closed-loop mechanism in which a moving platform and a fixed platform are connected by at least two independent motion chains. The mechanism has two or more degrees of freedom and is driven in parallel. The parallel mechanism has two parts, namely wrist and arm. The active area of the arm has a great influence on the active space, and the wrist is the connecting part between the tool and the main body. Compared with serial robots, parallel robots have many advantages, such as high rigidity, stable structure, large bearing capacity, high micro-motion accuracy and small motion load. In the position solution, the forward solution of serial robot is easy, but the reverse solution is very difficult. On the other hand, the parallel robot has a difficult forward solution, but an easy backward solution.
2. Transmission system
The drive system is a device that provides power for the mechanical structure system. According to the different power sources, the transmission modes of the drive system are divided into four types: hydraulic, pneumatic, electric and mechanical. Early industrial robots were driven by hydraulic pressure. Due to the problems of leakage, noise and low speed instability in the hydraulic system, and the heavy and expensive power device, there are only large heavy robots, parallel processing robots and hydraulically driven industrial robots in some special applications. Pneumatic drive has the advantages of high speed, simple system structure, convenient maintenance and low price. However, the working pressure of pneumatic device is low, so it is difficult to locate accurately. Generally, it is only used to drive the end effector of industrial robots. Pneumatic gripper, rotary cylinder and pneumatic sucker can be used as end effectors for grasping and assembling medium and small load workpieces. Electric drive is the most widely used drive mode at present, which is characterized by convenient access to power supply, fast response, large driving force, convenient signal detection, transmission and processing, and various flexible control modes can be adopted. Generally, stepping motor or servo motor is used as the driving motor, and there are direct driver at present, but the cost is high and the control is complicated. The reducer matched with the motor generally adopts harmonic reducer, cycloidal pin wheel reducer or planetary gear reducer. Due to the large number of linear drive requirements of parallel robots, linear motors have been widely used in the field of parallel robots.
3. Perception system
The robot sensing system transforms all kinds of internal state information and environmental information of the robot from signals into data and information that can be understood and applied by the robot itself or between robots. In addition to sensing mechanical quantities related to its working state, such as displacement, speed and force, visual sensing technology is also an important aspect of industrial robot sensing. Visual servo system takes visual information as feedback signal to control and adjust the position and posture of robot. Machine vision system is also widely used in quality inspection, workpiece identification, food sorting and packaging. The sensing system consists of an internal sensor module and an external sensor module. The use of intelligent sensors improves the mobility, adaptability and intelligence of robots.
4. Robot-environment interaction system
Robot-environment interaction system is a system to realize the interaction and coordination between robot and equipment in the external environment. Robot and external equipment are integrated into a functional unit, such as processing and manufacturing unit, welding unit and assembly unit. Of course, multiple robots can be integrated into one functional unit to perform complex tasks.
5. Man-machine interaction system
Man-machine interaction system is a device that people communicate with robots and participate in robot control. For example: computer standard terminal, command console, information display board, danger signal alarm, etc.
6. Control system
The task of the control system is to control the execution mechanism of the robot to complete the specified actions and functions according to the operation instructions of the robot and the signals fed back by the sensors. If the robot does not have information feedback characteristics, it is an open-loop control system; It is a closed-loop control system with information feedback characteristics. According to the control principle, it can be divided into program control system, adaptive control system and artificial intelligence control system. According to the form of controlled motion, it can be divided into point control and continuous trajectory control.