Tag Six-Axis Robots

The basic composition and characteristics of the traditional six-axis robot.

Traditional articulated robots are mainly composed of body structural parts, reducers, servo motors, controllers, and so on.

Body structure

The body of the industrial robot consists of a rotating base, a big arm, a small arm, and other parts, which are the most direct mechanical structure outside the robot. Robot body structure includes cast iron, cast steel, cast aluminum, structural steel, and other materials.

Reducer

A reducer is used to carry the load of each joint of the robot. The high speed and low torque output from the motor passes through the reducer to form a low speed and high torque, which improves the output torque of each axis of the robot and enables the robot to withstand larger loads. The robot has high requirements for the reducer, which needs to be small in size, small in mass, large in reduction ratio, high in precision, and shock resistant.

Currently, there are two main types of gearboxes used in multi-joint robots: one is RV gearbox and the other is the harmonic gearbox, which is generally placed in the heavy load position such as big arm and shoulder because of higher stiffness and rotary accuracy; the harmonic gearbox is placed in the small arm and wrist.

Drive control system

The drive control system is mainly used to control the robot to move according to the set motion parameters. It mainly consists of servo drivers, servo motors, and controllers.

(1) Servo motors are mainly used to drive the joints of the robot and are required to have the maximum power-to-mass ratio and torque-to-inertia ratio, high starting torque, low inertia, and a wide and smooth speed range;

(2) The servo driver is the device to drive the servo motor, according to the instructions of the controller, the servo driver gives the servo motor the corresponding current, so as to ensure that the servo motor moves in accordance with the demanded movement speed, acceleration, running position, and other conditions, so as to ensure that the movement of the robotic arm reaches the set requirements.

(2) The controller can manually set the internal parameters to realize the position control, speed control, and torque control of the robot.

Six-axis tandem robot “axis” role

Traditional six-axis industrial robots generally have six degrees of freedom, commonly including 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 synthesized to achieve the end of the 6 degrees of freedom of action.

First axis : The first axis is the part that connects the base and carries the weight of the whole robot and rotates left and right with the base;

Second axis: controls the back-and-forth swing of the robot’s big arm;

Three axes: control the small arm of the robot to swing back and forth;

Fourth axis: controls the rotation of the small arm;

Fifth axis: control and up and down fine-tuning the rotation of the robot wrist, usually when the product gripping can be carried out after the product flip action;

Six-axis: for the end of the fixture part of the rotation function, can be more accurate positioning to the product.

According to different application scenarios, there are different structural designs for the wrist part. b (bend) means bending structure, r (revolve) means rotating structure.

Advantages and disadvantages of 6-axis tandem robots

Advantages

(1) Compact structure, small installation footprint;

(2) Good dexterity, large range of hand reach positions, and good obstacle avoidance performance;

(3) No moving joints, good joint sealing performance, low friction, low inertia;

(4) Small joint driving force, low energy consumption.

Disadvantages

(1) There is a balance problem in the motion process, and there is coupling in the control;

(2) Poor rigidity of the robot structure when the big arm and small arm are stretched out;

(3) There are singularities in the process of controlling the motion, and the use and control algorithms need to be circumvented.