Robotic Manipulators Overview

December 20, 2019
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Robotic manipulators are now prevalent in factories all across the world, but they were first conceived to operate in areas inaccessible to humans like handling radioactive materials. Quickly the technology was adopted by the manufacturing industry and has transformed the production process.

Modern robots are capable of carrying out a multitude of tasks at speed and to an accuracy far superior to humans.Their capabilities vary but typically they can perform painting, spot welding, lifting and cutting tasks – all repetitive jobs that can cause injury to humans, especially when tired and concentration levels are low. Additionally, robotic manipulators cut production times and save money.

Robotic manipulators come in all manner of shapes and sizes and have predetermined capabilities. Each has a range of motion or an envelope of work in which they operate.

Robots are restricted by their hardware but can be designed to have a good range of movement and in most cases are superior to humans. Conversely, manipulators may not require articulate movement for their intended purpose. They may only require a sliding joint. The main advantage is that robotic arms can be extremely flexible.

A robotic manipulator is operated by manipulating solid links attached to robotic joints with the free end performing a given task such as welding.

They are controlled by electronic motors and have diagnostic and safety systems built in to ensure they can run autonomously with little supervision.

Manipulators are categorized by their construction:

Rectangular

Also known as Cartesian geometry arm, this type of manipulator uses Cartesian coordinates to move linearly along three axes. This type of geometry is most commonly found in gantry cranes for picking and placing materials. Robotic arms that use Cartesian coordinates generate a rectangular work envelope.

Cylindrical

Cylindrical geometry arms move linearly in two directions and rotate in one more direction. This type of robotic arm is most often used in machine tending, assembly, material handling, and palletizing operations.

Robotic arms with cylindrical geometry move linearly in two directions.

  • Vertical linear motion is called the stroke.
  • Horizontal linear motion is called the reach.
  • Rotational linear motion is called the swing.

These types of robots produce a cylindrical work envelope.

This robot structure allows high repeatability, a smaller work area and has a larger payload capacity due to its structural rigidity.

Spherical

These robotic manipulators can rotate in two directions and move linearly in one. This robot has base rotation, shoulder rotation and linear motion at the arm. They are used in machine tending, welding, coating, painting and assembly tasks. These robots have a mostly spherical work envelope at their outer reach but are limited by the linear reach of the arm and the rotation of the shoulder joint.

Although they have proven useful in specific applications, compared to jointed spherical arm manipulators, they lack flexibility and take up larger floor space.

Jointed spherical

Jointed spherical arm geometry robots have rotational movement in three directions and use revolute coordinates.

They are one of the most popular types of robotic arms and most accurately mimic the movement of the human arm.

Robotic arms with articulated geometry rotate on at least three axes:

  • Left and right movements are provided by rotation at the base.
  • Horizontal movement is provided by rotation at the shoulder.
  • Vertical rotation is provided by rotation at the elbow.

Except for working extremely close to the body, the work envelope for this robot is spherical.

The advantage of this envelope is a robotic arm with a very deep reach, minimal floor space usage and high positioning mobility of the arm. Due to its complexity, these robots usually are more expensive and require skilled technicians to perform maintenance tasks.

Additionally, articulated robots can have a wrist that offers a further three ranges in motion giving complete control over the workspace. Typically, a robot wrist provides the same 3D rotations as a human hand: roll, pitch, and yaw.

The future of robotic manipulators

There is a definite trend in the manufacture of robotic arms toward more dexterity, more degrees-of-freedom, and capabilities beyond the human arm.

For example, robotic manipulators have made it to space on multiple missions. Currently, on Mars, the Curiosity Rover has a robotic manipulator arm that has five degrees of freedom of movement provided by rotary actuators known as the shoulder azimuth joint, shoulder elevation joint, elbow joint, wrist joint and turret joint.

The International Space Station has a robotic arm that is exceptionally versatile. At each end, the shoulder and wrist look identical, and both carry out similar functions like pitch, roll, and yaw. Unlike autonomous robots, the functions of the arm are controlled from inside the space station via a control panel.

Robotic manipulators are being applied in medicine and surgical procedures that require a high degree of accuracy and repeatability. It seems appropriate that mechanical joints are helping to replace knee and hip joints in patients across the world.

Tesla, the car manufacturer, has the most advanced manufacturing facility on the planet and robots control nearly every function. The body of its model S is completely put together using robots. Then it transferred to the paint shop by a huge manipulator where you guessed it, robots completely take care of painting the vehicle. The car manufacturing industry is renowned for its use of autonomous robots, but Tesla takes this to another level. The manufacturing process uses more than 160 specialist robots, including 10 of the most colossal robots in the world.*Tesla Will Produce 10,000 cars a week by the end of 2019.

Fun fact – Some of the robots have inside the Tesla factory have been given nicknames from the X-men series. Watch this video from Business Insider and Wired as they take a look around the mega factory.

Robotic manipulators are becoming a critical piece of technology the world over. In this ever-connected world where manufacturing and delivery times are only getting quicker, production lines will inevitably need to pick up the pace to cope with the increasing demand. Who knows what’s around the corner in the land of robotics?

 

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