Classification of coordinate forms of industrial robot manipulators

Industrial robots are classified into the following categories according to the coordinate form of the manipulator:

1) Cartesian coordinate industrial robot

Its moving part consists of three mutually perpendicular linear movements (PPP), and its workspace is rectangular. Its moving distance in each axis can be directly read on each coordinate axis, which is intuitive, easy to program and calculate position and posture, with high positioning accuracy, non-coupling control, and simple structure. However, the space occupied by the body is large, the range of motion is small, the flexibility is poor, and it is difficult to coordinate with other industrial robots.

2) Cylindrical coordinate industrial robot

Its movement is achieved through a motion system consisting of one rotation and two movements. Its workspace diagram is cylindrical. Compared with the rectangular coordinate industrial robot, under the same workspace conditions, its body occupies a small volume and has a large range of motion. Its positioning accuracy is second only to the rectangular coordinate robot, and it is difficult to coordinate with other industrial robots.

3) Spherical coordinate industrial robot

The spherical coordinate industrial robot is also called the polar coordinate industrial robot. The movement of its arm consists of two rotations and one linear movement (i.e. RRP, one rotation, one pitch and one telescopic movement). Its working space is a sphere. It can pitch up and down and can grab coordinated workpieces on the ground or in low positions. It has high positioning accuracy and the position error is proportional to the arm length.

4) Multi-jointed industrial robots

Also known as a rotary coordinate industrial robot, the arm of this type of industrial robot is similar to a human upper limb, and its first three joints are rotary pairs (i.e., RRR). This industrial robot is generally composed of a column and large and small arms. The column and the large arm form a shoulder joint, and the large arm and the small arm form an elbow joint, which can make the large arm perform rotation and pitch swing, and the small arm perform pitch swing. Its structure is the most compact, flexible, and occupies the smallest area. It can work in coordination with other industrial robots, but its position accuracy is low, there are balance problems, and control coupling. This type of industrial robot is increasingly widely used.

5) Planar joint industrial robot

It uses a mobile joint and two rotary joints (PRR). The mobile joint realizes up and down movement, while the two rotary joints control the front and back, left and right movement. This type of industrial robot is also called SCARA (Seletive Compliance Assembly Robot Arm) assembly robot. It is flexible in the horizontal direction and has great rigidity in the vertical direction. It has a simple structure and flexible movements. It is mostly used in assembly operations, especially for the plug-in assembly of small-sized parts, such as the plug-in and assembly of the electronics industry.