This article was updated December 2023.
Robots are widely used in industry to perform specific tasks on assembly lines and other critical areas by mimicking the manual movements of human arms. These robots are known as robotic manipulators.
Image Credit: Nomad_Soul/Shutterstock.com
A robotic manipulator can perform tasks in hazardous environments, handling dangerous biohazards or radioactive materials, but they are increasingly being employed in everyday environments from factories to outer space.
A series of sliding or jointed segments are combined to form an arm-like robotic manipulator that is capable of automatically moving objects within a given number of degrees of freedom. Every commercial robot manipulator includes a controller and a manipulator arm.
The performance of the robotic manipulator depends on its speed, payload weight and precision. However, the reach of its end-effectors, the overall working space, and the orientation of the work are determined by the manipulator’s structure.
Robotic manipulators are not a new idea and have already been in operation in many areas of manufacturing for several years. As AI advances, increasing the accuracy and function of robotics will allow a greater range of tasks to be achieved compared to the robotic manipulators of previous decades.
Kinematics of a Robotic Manipulator
A robot manipulator is constructed using rigid links connected by joints with one fixed end and one free end to perform a given task, such as moving a box from one location to the next.
The manipulator’s joints are the movable components that enable relative motion between the adjoining links. There are also two linear joints that ensure non-rotational motion between the links, and three rotary-type joints that ensure relative rotational motion between the adjacent links.
The arm and body of the robotic manipulator consist of three joints connected by links. These can be used to move and place tools or objects within the workspace. The function of the wrist is to arrange objects or tools, with its structure consisting of two or three compact joints.
Robotic Manipulator Arm Configuration
Manipulators are grouped into several types based on the combination of joints, which are as follows:
Cartesian Geometry Arm
This arm employs prismatic joints to reach any position within its rectangular workspace by using Cartesian motions of the links.
Cylindrical Geometry Arm
This arm is formed by the replacement of the waist joint of the Cartesian arm with a revolute joint. It can be extended to any point within its cylindrical workspace by using a combination of translation and rotation.
Polar/ Spherical Geometry Arm
When a shoulder joint of the Cartesian arm is replaced by a revolute joint, a polar geometry arm is formed. The positions of end-effectors of this arm are described using polar coordinates.
Articulated/Revolute Geometry Arm
Replacing the elbow joint of the Cartesian arm with the revolute joint forms an articulated arm that works in a complex thick-walled spherical shell.
Selective Compliance Automatic Robot Arm (SCARA)
This has two revolute joints in a horizontal plane, allowing the arm to extend within a horizontal planar workspace. The TH650A SCARA Robot by TM Robotics is a great example of the pick-and-place functionality of robotic manipulators.
Cosmetics handling and packaging using SCARA robots from TM Robotics (Europe) Ltd
Video courtesy of TM Robotics.
Wrist Configuration
The two main types of wrist design include:
- Roll-pitch-roll or spherical wrist
- Pitch-yaw-roll
The spherical wrist is more common because of its mechanically simpler design. It has 6 degrees of freedom and consists of a Hooke shoulder joint followed by a rotary elbow joint.
Applications
Some of the major applications of a robotic manipulator are presented below:
- Motion planning.
- Remote handling.
- Teleoperation.
- Micro-robots.
- Humanoid robots.
- Machine tools.
- Space operations (such as onboard the ISS.).
- Military EOD.
- Medical applications, such as surgery.
Teleoperation is one application that has the potential to revolutionize the interaction between humans and robotics. Such capabilities allow human operators to take control of the robotic manipulator to perform hazardous tasks, such as telemedicine or even in the care industry.
Telemedicine robotic manipulators can perform delicate operations such as keyhole surgery and reduce potential human error. Robotic manipulators can replace human pickers and packers, freeing workers up for more value-added tasks in the supply chain. Additionally, manipulators can be used for high-precision PCB assembly.
In Summary
Robotics is an established field that has provided benefits for multiple industries, producing devices that can perform tasks with higher precision and faster than human counterparts. Moreover, robots are improving the safety of human workers by replacing them in hazardous or inaccessible environments.
Robotic manipulators are increasingly being employed in sectors such as the space, biomedical, and delivery industries. With the increasing implementation of AI and associated technologies in the field of robotics, the use of a robotic manipulator continues to provide vast benefits for operators and companies.
References and Further Reading
BrightHub (2022) Robotics: Structure of Industrial Robots or Manipulators: Types of Base Bodies – I [online] brighthubengineering.com. Available at: https://www.brighthubengineering.com/robotics/26371-robotics-structure-of-industrial-robots-or-manipulators-types-of-base-bodies-one/
Pires, J.N.(2007) Robot Manipulators and Control Systems Industrial Robots Programming pp. 35-107 [online] link.springer.com. Available at: https://link.springer.com/chapter/10.1007/978-0-387-23326-0_2
EVS (website) What is a Robotic Manipulator? A Guide [online] evsint.com. Available at: https://www.evsint.com/what-is-a-robotic-manipulator/