The application of industrial robots is increasing, mainly because industrial robots have many advantages. For industrial robots, industry related personnel must have some understanding. But for ordinary people, industrial robots are far away from our life. In order to increase our understanding of industrial robots, this paper will introduce four control methods of industrial robots.
At present, the most widely used robot in the market is industrial robot, which is also the most mature and perfect one. Industrial robot can be widely used because it has a variety of control methods. According to different tasks, it can be mainly divided into point control method, continuous trajectory control method, force (torque) control method and intelligent control method There are four control modes, and the function points of these control modes are described in detail below.
1. Point position control (PTP)
This control method only controls the pose of the end effector of the industrial robot at some specified discrete points in the workspace. In the control, the industrial robot is only required to be able to move quickly and accurately between adjacent points, and the trajectory to reach the target point is not specified. The positioning accuracy and the time required for motion are the two main technical indexes of this control mode. This control method has the characteristics of easy implementation and low positioning accuracy. Therefore, it is often used in loading and unloading, handling, spot welding and inserting components on the circuit board, which only requires the end effector to maintain accurate position and pose at the target point. This method is relatively simple, but it is quite difficult to achieve the positioning accuracy of 2 ~ 3um.
2. Continuous trajectory control (CP)
This control method is to continuously control the position and pose of the end effector of the industrial robot in the working space. It is required to move in a certain precision range in strict accordance with the predetermined trajectory and speed, and the speed is controllable, the trajectory is smooth, and the motion is stable, so as to complete the task. Each joint of industrial robot moves continuously and synchronously, and its end effector can form a continuous trajectory. The main technical index of this control method is the tracking accuracy and stability of the position and pose of the end effector of the industrial robot. Generally, this control method is used for arc welding, painting, deburring and inspection robots.
3. Force (torque) control mode
In the process of assembling, grasping and placing objects, in addition to accurate positioning, the force or torque used must be appropriate. In this case, the (torque) servo mode must be used. The principle of this control mode is basically the same as that of position servo control, except that the input and feedback are not position signals, but force (torque) signals, so the force (torque) sensor must be used in the system. Sometimes, the sensing functions such as approaching and sliding are used for adaptive control.
4. Intelligent control mode
The intelligent control of robot is to obtain the knowledge of the surrounding environment through sensors, and make corresponding decisions according to its own internal knowledge base. Intelligent control technology is adopted to make the robot have strong environmental adaptability and self-learning ability. The development of intelligent control technology depends on the rapid development of artificial intelligence such as artificial neural network, genetic algorithm, genetic algorithm and expert system in recent years. Perhaps this kind of control mode really has the taste of “artificial intelligence”, but it is also the most difficult to control well. Besides algorithm, it also depends heavily on the accuracy of components.
From the perspective of control essence, the industrial robot is still in the lower level of space positioning control stage in most cases, without much intelligence content. It can be said that it is just a relatively flexible manipulator, and there is still a long distance from “human”.