Composition of industrial robots

Generally speaking, industrial robots are composed of three major parts and six subsystems.

The three parts are mechanical part, sensing part and 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.

1. Mechanical structure system

In terms of mechanical structure, industrial robots are generally divided into series robots and parallel robots. The characteristic of the serial robot is that the motion of one axis will change the coordinate origin of the other axis, while the motion of one axis of the parallel robot will not change the coordinate origin of the other axis. The early industrial robots were all series mechanisms. Parallel mechanism is defined as a closed loop mechanism that 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 connection between the tool and the main body. Compared with the serial robot, the parallel robot has the advantages of large stiffness, stable structure, large bearing capacity, high micro motion accuracy and small motion load. In the position solution, the positive solution of the serial robot is easy, but the inverse solution is very difficult; On the contrary, the parallel robot has a difficult forward solution, but a very easy inverse solution.

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, electrical 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 cumbersome and expensive power units, there are only large heavy-duty robots, parallel processing robots and industrial robots driven by hydraulic power in some special applications. The pneumatic drive has the advantages of high 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 locate accurately, so it is generally only used to drive the end effectors of industrial robots. The pneumatic hand grab, rotary cylinder and pneumatic suction cup can be used as the end effector for the grab and assembly of medium and small load workpieces. Electric drive is one of the most widely used driving methods at present. It is characterized by convenient access to power, fast response, large driving force, convenient signal detection, transmission and processing, and can adopt a variety of flexible control methods. The driving motor is generally a stepping motor or servo motor. At present, there are also direct driving motors, but the cost is high and the control is more complex. The reducer matched with the motor is generally a harmonic reducer Cycloidal pin gear reducer or 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.

3. Perception system

The robot perception system transforms various internal state information and environmental information of the robot from signals to data and information that can be understood and applied by the robot itself or among robots. In addition to the need to perceive mechanical quantities related to its own working state, such as displacement, speed and force, visual perception technology is an important aspect of industrial robot perception. The visual servo system uses visual information as feedback signals to control and adjust the position and posture of the robot. Machine vision system is also widely used in quality inspection, workpiece identification, food sorting and packaging. The perception system is composed of internal sensor modules and external sensor modules. The use of intelligent sensors improves the mobility, adaptability and intelligence level of the robot.

4. Robot environment interaction system

The robot environment interaction system is a system that realizes the interconnection and coordination between robots and equipment in the external environment. The robot and external equipment are integrated into a functional unit, such as processing and manufacturing unit, welding unit, assembly unit, etc. Of course, multiple robots can also be integrated into a functional unit to perform complex tasks.

5. Human computer interaction system

Human computer interaction system is a device for people to connect with robots and participate in robot control. For example: standard terminal of computer, instruction console, information display board, danger signal alarm, etc.

6. Control system

The task of the control system is to control the executive mechanism of the robot to complete the specified movement and function according to the robot’s work instructions and the signals fed back from the sensors. If the robot does not have the characteristics of information feedback, it is an open loop control system; If it has the characteristics of information feedback, it is a closed loop control system. 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 control motion, it can be divided into point control and continuous trajectory control.