Understanding Industrial Robot Wrist: Functionality, Working Principle, and Degrees of Freedom

What is an industrial robot Wrist & How it Works?

1. A Brief Comparison between Robot Arms & Human Arms.  

Before the discussion of an Industrial Robot Wrist, we will have to compare a human arm with a robot arm. As in a Human Arm the wrist is almost at the end before 5 Fingers. Likewise in an Industrial Robot Arm the wrist is almost at the end of the arm before the end effector. Technically speaking the Robot End Effector is the Last Working Link of the robot also technically called Wrist End Attachments. 

The Last working links or attachments of an Industrial Robot Wrist can be Drills, Cameras, Cutting Tools, Brushes, Precision Sensors, Welding Tools, Process Tools, Sanders, Magnets, Suction Cups or Grippers.      

In a human being shoulder and elbow are joints & the bones connecting them are a sort of links. The working principle, structure and mechanism of the arm & a robot is the very same & carbon-copy.

The fundamental basic structure of an industrial robot and a human arm are almost alike. Same-wise a robotic arm is also a union of joints & links. Associating a robot arm to human body, it is built as of such parts that can be freely moved or bent about such as a human shoulder or elbow which are free to movement in any direction within a limited sequence.

So, the workability & style within the arm links is the same in both robots & humans. But according to the overall structure a human arm is like a Series Robot as its joints are in series i.e., wrist, elbow and shoulder.

2. What’s an industrial Robot Wrist and it’s Multi- Purpose Functionality & Working?                            

In the language of Mechatronics Engineering a “Robot Wrist” is specifically made for assisting End-of-Arm Tooling also known as (EOAT). A robot wrist working

mechanism is according to work specifications & workload demands & a lot of other factors which come into play when an Industrial Robot operates. 

The Robot Wrist Mechanism is an integral part of the overall a fully systemized robot and its work is to keep the robotic end effector fully oriented for different types of high-end industrial tasks because when a robot is working then 2 of its integral basic parts are in action i.e., the overall robot body and the robot arm. Mechanically speaking an industrial robot as a whole is a high-tech System composed of multiple parts that working together to complete predefined tasks.       

The robotic wrist basically comprises two to three solid joints allowing a robot to work in the most exact style possible to complete the most demanding jobs day by day, as robots are used in industrial environment is increasing especially in automobiles industry & such areas in different industry where hazardous material can’t be handled by human beings.   

3. Robot Wrist Mechanisms and Different Working Configurations.

From the above detailed discuss we have now come to the basic point that an Industrial Robot Wrist overall performs end tasks, assignments and works. Thus, this special mechanism of the robot wrist makes it fully compatible with fully revolve/spin around an axis and consist of joints that enable the wrist to carry out multi -dimensional moves in any desired direction. 

The robot wrist is prone to many adverse factors while working in an industrial environment where it is exposed to variable vibrations and such working vibrations have an untoward effect on the wrist & it needs periodic inspect. 

Now we discuss in simple words below what is Yaw, Roll and Pitch of any robot wrist before we get into more detailed study of 6 axis industrial robot wrist Configurations.

1. The first wrist movement configuration is Yaw. Yaw is wrist rotation around a vertical axis. In other words a wrist in Yaw position means turning and associated motion to left and right.

2. The second movement configuration of wrist is Roll. Roll is the rotation around arm axis. In simple words a wrist Roll configuration is also known as Swivel Configuration of the wrist as it is also referred to as the wrist rotation feature round the arm axis.

3. The third wrist movement mechanism is Pitch. The wrist Pitch configuration is rotation around horizontal axis.

In simple words the wrist pitch configuration is also known as a robot Wrist Bend.

Now we will study below in full detail the total six possible working mechanisms & configurations of a 6 axis industrial robot wrist which are, 

• Pitch: The 1^st type wrist configuration is Rolling backward & forward which is also called Bending

• Yaw: 2^nd kind of wrist working configuration is Spinning from left to right or from right to left which is also termed as Yawing

• Roll: 3^rd type of wrist configuration is Rotating down to the left or right also referred as Swiveling.

• Notation TLO: In this 4^th type of wrist configuration a robot wrist specifically work in relevance to a vertical column. In this working configuration the wrist move in & out or up & down according to the work & load.     

• Notation TRL: According to this 5^th kind of wrist working mechanism it features a specialized sliding arm which has the ability of rotating on both the horizontal axis & vertical axis.

• Notation LOO: This 6^th type of wrist configuration features three sliding joints which easily allow a wrist to make movements in any or multiple directions. Another special specification of this wrist working configuration is that out of total three sliding joints the two joints are orthogonal. This type of wrist working configuration is found X,Y,Z and rectilinear type of robots. 

4. Robot Wrist Degree of Freedom.

So now it’s totally easy to understand that a fully functional industrial robot arm has multidimensional degrees of freedom. The robot arm “shoulder” can easily rotate in any side or direction, so it has three degrees of freedom. While the elbow of an industrial robot arm can make a movement in only one direction thus it has only one degree of freedom and likewise The Robot Wrist can Turn, Circle and Revolve in three sides so it has mechanically speaking Three Degree’s of Freedom. 

So, an industrial robot wrist different movements can be also expressed in another Manner as under.   

• Bend-roll pitch and roll
• Roll-roll pitch and roll or yaw & roll
• Roll-roll
• Bend-bend-roll
• Bend-roll-roll
• Roll-bend-roll
• Roll-roll-rollpitch-yaw-roll

Summary

So, the essence of the above article is that the Robot Wrist must be totally configured according to work & load because the end effector of the robot arm will make movements only in the possible directions where the wrist can easily move. That’ why the best possible configuration & mobility standard of the wrist makes end effector working very precise & exactly as wanted by us.