Robotice Pivot Joint: How to use Mechanical Joints in Robotics

With enough brains and willpower, anyone can learn how to build a robot. If you’re interested in mechanics or robotics, all it takes is a little ingenuity and you can make a difference in the world of machines.

From MIT’s MiniCheetah to the US military’s recent robotics projects, some of the most interesting robots feature apposable joints, gears, and human emulated parts.

The robotic pivot joint is based on anatomical parts found in the wild which give the worlds fiercest predators or simplest rodents the ability to move. If you’re interested to see how mechanical joints will improve your industrial robotics or machine hobbies, read on to learn more!

What is a Pivot Joint?

A pivot joint, when identified in animals, is the part of anatomy which allows for rotation. This joint-type gives rise to movement and mobility in almost all animals with skeletons.

In the pivot joint category, there are multiple types of joints that take form.

Ball-and-Socket Joint

This usually requires two bones, a bone with a rounded end which fits into a depression or cover of another bone. This joint allows for many degrees of rotation, as the axis falls on the limits of a circle.

In robotics, a ball-and-socket joint is used for full rotation of limbs to perform complex tasks. For example, in the automotive industry, articulated robots rotate on a grounded axis (similar to a ball-and-socket) to retrieve and add on parts to vehicles.

Condyloid Joint

The Condyloid allows for biaxial movement or movement along two planes. The wrist bone is a good example, in which case a bone fits into another side cavity of another bone.

The Condyloid is typically found in serial manipulators and other small precise-movement robots. The biaxial movement lets a robot perform two-plane tasks such as moving fluid into containers from left to right.

Hinged Joints

Much like a door hinge, hinge joints only allow for one plane of movement. Think of the human elbow or knee, which doesn’t permit any rotation, and only accepts movement in one direction.

This applies to mammal-like robots. For instance, Boston Dynamic’s WildCat robot uses hinged joints to crouch, run, and jump. The hinged joint design is almost exactly like human leg-joints, making this form of joint potent at making mobile machines.

Robotic Pivot Joints

Whether it is industrial or non-industrial, as long as a robot needs the freedom to move it will likely need a joint-structure. The most common robotic joints depend on the natural world or the list of typical joints mentioned above.

Let’s look at some robotic pivot joint examples.

Serial Manipulators

These robots emulate the structure of a human arm, elbow, and wrist. Each of these parts uses different joints for different radial movements and rotations.

For example, a serial manipulators arm holds the robot in place, while the elbow gives a hinge axis for downwards movement. Finally, the wrist gives biaxial movement so the robot can attend to adjacent tasks.

Serial manipulators sometimes include rotational joints, like pivot joints, to perform two-way movements that elbow-joints cannot manage.


Centauro is a robot from IIT which mimics human and horse joint-structures. The hips, legs, and ankles experience near full rotation. Each rotation attaches to a pivot joint, giving it the ability to turn its frame, curve angles, and walk.

The upper-body uses the same means of rotation and curling to pick up weighted objects. Centauro is like man, so its hands experience many degrees of rotation in order to reach around tight spaces.

Delta Robots

The industry defines Delta as a parallel robot, capable of operating on its axis in the shape of a parallelogram. The Delta’s arms connect to a joint-system which gives it control of 90-degree movement.

As pivot joints dictate rotation, the Delta’s pivot joints are basic, if not implicit to the rest of the frame which controls its free range of rotation and twisting.

Scara Robots

Scara is an example of a small robotics assembly item, capable of full automation, pieced together with an articulated robotic arm. It’s typically put together with two functional arms and a base, each arm has a biaxial joint for adjacent movement.

Some Scara robots have rotational joints (pivot joints) but like most examples of industrial robotics, common tasks don’t require full rotation.

Building Your Own

Piecing together a pivot joint requires a few working parts:

  • Rotational engine
  • Rotating shaft, or connecting parts with the same function
  • Understanding robotics and pivot joints

When you’re using mechanical joints in robotics, one of the easiest places you can start is with your idea of movement. That is, what tasks require mobility?

Once you found the answer to your question about mobility, make sure you’ve found an engine that supports the maximum radial or rotational movement you’re aiming for.

After this step, it’s highly recommended that you find an emulated form of the final result you’re looking for. In other words, if you’re building an elbow-joint controlled arm, make references to the actual human arm.

Become a Mech Expert

You have to admit, being a machines expert is one thing, but mastering robotic movement? That can be a road to some exciting discoveries.

After reading this post, you understand the pivot joint, how it works, and where to apply it to your basic robot. But, what’s next?

You are the decider of the next working robot. If it’s industrial, just a hobby, or for our military, understanding how these machines work can save the world a lot of time and energy.

So, what do you say? It’s time for you to build the next big project. Go for it, and along the way, learn some more about design factors when building robots.

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