Characteristics of the robot control system
The structure of the robot adopts the spatial open link structure, and the motion of each joint is independent. In order to realize the motion trajectory of the end point, the motion coordination of multiple joints is needed. Therefore, its control system is much more complex than the ordinary control system, with the following characteristics:
1. Robot control is closely related to structural kinematics and dynamics. The state of the robot hand can be described in a variety of coordinates. According to the need to choose different reference coordinate system and do the appropriate coordinate transformation;
2. It is often required to solve the forward and inverse problems of motion. In addition, it is also necessary to consider the influence of inertial forces, external forces (including gravity), Coriolis forces, and centritic forces.
3, a simple robot also has at least 3 to 5 degrees of freedom, more complex robots have more than a dozen, or even dozens of degrees of freedom. Each degree of freedom generally contains a servo mechanism, which must be coordinated to form a multivariable control system.
4. Organically coordinate multiple independent servo systems to make them act according to human will, and even give the robot certain intelligence. This task can only be completed by the computer. Therefore, the robot control system must be a computer system.
5, the mathematical model describing the state and motion of the robot is a nonlinear model, with different states and changes in external forces, its parameters are also changing, and there are still coupling between the variables.
6 , the movement of the robot can be accomplished by different ways and paths, therefore, there is an "optimal" problem. Advanced robots can use artificial intelligence methods to establish a huge information base with computers, with the help of the information base for control, decision-making, management and operation.
Traditional automatic machinery is not focused on its own action, while the control system of industrial robot focuses more on the relationship between the body and the operation object.
Therefore, the robot control system is a coupled, nonlinear multivariable control system closely related to kinematics and dynamics principles.
As the actual work situation is different, there can be a variety of different control methods, from simple programming automation, microprocessor control to small computer control and so on.
The characteristics and basic requirements of the robot control system
To implement good control of the robot, it is important to know the characteristics of the controlled robot, and from what we know about the dynamics of the robot, it has the following properties:
1. The essence of robot is a nonlinear system. There are many factors that cause the nonlinearity of the robot, such as structure, transmission parts, driving components and so on.
2. There is a coupling effect between the joints, which is manifested as the movement of a certain joint. There will be dynamic effects on other joints, so that each joint has to bear the disturbance caused by the movement of other joints.
3, is a time-varying system, and the dynamic parameters change with the position of the joint motion.
From the point of view of use, the robot is a special automation equipment, and its control has the following characteristics and requirements:
1, multi-axis motion coordination control to generate the required working trajectory. Because the robot hand motion is the synthesis of all joint motion, in order to make the hand move according to the set law, it is necessary to control the coordination of each joint, including motion trajectory, action sequence and other aspects of coordination.
2, high position accuracy, large speed range
3. The static error rate of the system should be small
4. The velocity error coefficient of each joint should be as consistent as possible
5, position no overshoot, dynamic response as fast as possible
6, need to use plus (minus) speed control
7, from the operational point of view, the control system is required to have a good man-machine interface, as far as possible to reduce the requirements for the operator
8. From the perspective of system cost, it is required to reduce the hardware cost of the system as much as possible, and more software servo methods are used to improve the performance of the control system
Robot control mode:
There is no unified standard for the classification of industrial robot control mode:
1. Robot action control mode
2. Robot motion control mode
(1. Robot position control mode: positioning control mode - fixed position mode, multi-point position mode, servo control mode; Path control mode: continuous trajectory control, point-to-point control)
(2. Robot speed control mode: speed control mode - fixed speed control, variable speed control; Acceleration control mode - fixed acceleration control mode, variable acceleration control mode)
(3. Control mode of robot force)
Robot action sequence control mode
3. Robot teaching control mode
(1. Teaching with actual robot: direct teaching method - the power level is separated from teaching, and the servo level is connected to teaching; Remote control teaching method - teaching box teaching method, joystick teaching method, master-slave teaching method)
(2. No robot teaching: indirect teaching method - model robot number, special tool number; Off-line teaching method -- numerical input showing, graphical showing, software language teaching)
Robot control system structure and working principle
An industrial robot system is usually divided into two parts: the mechanism body and the control system. The elements of robot control system mainly include computer hardware system and operation control software, input/output equipment and devices, drive system, sensor system.
The control system of industrial robot is an important part of the robot to complete the task to be determined. The basic functions are:
1. Memory function
2. Teaching function
3, with peripheral equipment contact function
4, coordinate setting function
5, man-machine interface
6. Sensor interface
7. Position servo function
8. Fault diagnosis and safety protection function