Robot Joint Types: The Essential Introduction

Understanding the various types of robot joints is crucial as they greatly influence the performance and functionality of robots.

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Each joint type significantly affects the motion range and capabilities of your robot.

For newcomers to robotics, categorizing robot joints can be daunting due to the multitude of types available.

However, a basic familiarity with joint types enhances your ability to maximize the benefits from your robots. In this write-up, we delve into the different perspectives for categorizing robot joints.

How Are Different Robot Joint Types Determined?

At first glance, you might view a robot as a cohesive machine. Nevertheless, analyzing its individual parts reveals more complexity.

All industrial robots can essentially be understood as chains or assemblies of "joints." These joints function as mechanisms that allow movement along one or more of the robot's axes. Together, they orchestrate the specific motions of the robot's appendages.

Understanding robot joint types is beneficial for discerning the most suitable robots for your requirements.

There are three primary ways to classify robot joints:

1. By actuation type
2. By kinematic design
3. By joint function

This classification provides valuable insights into the mechanisms that govern particular robot joints. We will explore each category further below.

3 Types of Robot Joint by Actuation Type

The first method of categorizing robot joints revolves around their actuation type. An actuator refers to any mechanical or electromechanical device that creates motion by generating force through a specific energy form.

Here are the three fundamental types of robot actuators:

1. Electric

Electric actuators convert electrical energy into motion via an electric motor, producing torque that facilitates joint movement.

Among the actuator types, electric ones are the most prevalent in robotics for their speed, precision, and portability. While they may not offer as much power as other types, they demonstrate an excellent balance of cost and strength.

2. Pneumatic

Pneumatic actuators generate force through using compressed air. Given that many manufacturing facilities already have pneumatic lines, this option can be convenient and is frequently utilized for robot tools.

Pneumatics provide rapid movement and are straightforward to implement; however, they have limited power compared to hydraulics and require more additional components such as pumps and pipes than electric systems.

3. Hydraulic

Hydraulic actuators utilize pressurized liquid to create motion, offering more strength than their counterparts, making them suitable for heavy-duty applications.

Hydraulic robots often possess a greater strength and mobility range, although they can be costly, demand significant maintenance, and can lead to messy situations if leaks occur.

3 Robot Joint Types by Kinematic Design

Another perspective for classifying robot joints is based on their movement principles, which stem from their kinematic design. Each joint encompasses one or more degrees of freedom arranged differently according to the joint type.

The three most common joint types based on kinematic design include:

1. Linear

Linear or prismatic joints can shift along a single axis in either translational or sliding movements.

This type is arguably the simplest to visualize and manage, adjusting the joint's length upon actuation.

2. Revolute

Revolute or rotational joints pivot around a single point with one degree of freedom. Consider the elbow joint in your arm; it bends predominantly in one direction.

Many industrial robots are primarily composed of a series of revolute or rotational joints, allowing for well-defined control strategies.

3. Spherical

Spherical joints permit movement in multiple degrees of freedom around a common point. They resemble the shoulder's top joint, which can move in various directions but remains centered around one point.

Controlling a spherical joint can be relatively complex, often described as three revolute joints intersecting at a shared axis.

3 Robot Joint Types by Function

This method of analyzing robot joints is particularly useful for industrial robotics, as it relates to a joint's function or role within an industrial manipulator.

The three primary functions of a joint in an industrial manipulator are as follows:

1. Shoulder Joint

Located at the base of the robotic manipulator, the shoulder joint is typically the largest and influences the robot's rotational capabilities. It significantly determines the robot's workspace size.

2. Elbow Joint

Situated in the center of the robotic manipulator, the elbow joint most affects the lifting strength of the robot. Any restrictions on this joint can limit the robot's workspace.

3. Wrist Joint

The wrist joint is positioned at the end of the robotic manipulator and greatly affects the posture of the robot's end effector. In many cases, wrist joints are capable of full 360-degree rotation and experience more environmental vibrations than other joints.

Essential Insights on Robot Arm Joint Design

Now that you have a foundational understanding of robot joints, you can better appreciate the design process behind robots.

However, unless you're constructing robots yourself, there's little additional knowledge required. It's most crucial to identify which type of robot you'll utilize and how to apply it to your specific application.

With appropriate robot programming tools, most complexities are managed by the software.

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