Basic composition of traditional joint robot
Traditional articulated robots are mainly composed of body structural parts, reducers, servo motors, controllers, etc.
Body structure
The industrial robot body is composed of rotating base, upper arm, forearm and other parts, which is the most direct mechanical structure outside the robot. The structural parts of the robot body include cast iron, cast steel, cast aluminum, structural steel and other materials.
reducer
The reducer is used to carry the load of each joint of the robot. The high speed and low torque output by the motor passes through the reducer to form a low speed and high torque, thereby increasing the output torque of each axis of the robot, so that the robot can bear a larger load. The robot has high requirements on the reducer, which requires the reducer to be small in size, small in mass, large in reduction ratio, high in precision, and impact resistant.
At present, there are mainly two kinds of reducers widely used in multi-joint robots: one is RV reducer, and the other is harmonic reducer. RV reducers are generally placed on heavy loads such as arms and shoulders due to their higher rigidity and rotation accuracy; harmonic reducers are placed on forearms and wrists.
drive control system
The drive control system is mainly used to control the robot to move according to the set motion parameters. It mainly includes servo drives, servo motors and controllers.
(1) Servo motors are mainly used to drive the joints of robots, and require maximum power-to-mass ratio and torque-to-inertia ratio, high starting torque, low inertia, and a wide and smooth speed regulation range;
(2) The servo driver is a device that drives the servo motor to move. According to the instructions of the controller, the servo driver gives the corresponding current to the servo motor, so as to ensure that the servo motor moves according to the required movement speed, acceleration, and operating position. The movement of the mechanical arm meets the set requirements.
(2) The controller can manually set its internal parameters to realize various functions such as position control, speed control and torque control of the robot.
Six-axis serial robot "axis" function
Traditional six-axis industrial robots generally have 6 degrees of freedom, which commonly include rotation (S-axis), lower arm (L-axis), upper arm (U-axis), wrist rotation (R-axis), wrist swing (B-axis) and wrist rotation. (T axis). 6 joints are synthesized to realize 6 degrees of freedom movement at the end.
picture
One axis: The first axis is the part connected to the base, which carries the weight of the entire robot and the left and right rotation of the base;
Two axes: control the front and rear swing of the robot arm;
Three-axis: control the front and rear swing of the robot arm;
Four-axis: control the rotation of the arm of the robot;
Five-axis: Control and fine-tune the rotation of the manipulator wrist up and down, usually when the product is grasped and the product can be flipped;
Six-axis: Rotation function for the end gripper part for more precise positioning to the product.
According to different application scenarios, the wrist part also has different structural design methods. B (bend) indicates a bending structure, and R (revolve) indicates a rotating structure.
Advantages and disadvantages of six-axis serial robot
Advantage
(1) Compact structure, small installation area;
(2) Good flexibility, wide range of hand reach positions, and good obstacle avoidance performance;
(3) There is no moving joint, the joint sealing performance is good, the friction is small, and the inertia is small;
(4) The driving force of the joint is small and the energy consumption is low.
disadvantage
(1) There is a balance problem during the movement, and there is coupling in the control;
(2) When the boom and forearm are stretched out, the structural rigidity of the robot is poor;
(3) There are singular points in the control motion process, and the use and control algorithms need to be avoided.
