Robotic arm

Robotic arms are computer-controlled machines that are made to move and replicate the functions of human arms. These devices can be designed to perform a variety of tasks and are categorized by the types and numbers of joints they have. They are widely used in manufacturing because they can perform repetitive tasks quickly, consistently, and precisely, allowing companies to control the quality and cost of production. Robotic arms can also be used in situations that would expose humans to harm, such as those in outer space, in deep water, and where explosives, chemicals, temperature, or disease cause hazardous conditions. In some cases, robotic arms are manipulated by human handlers observing from a distance.

Background

Some of the earliest robotic devices were designed in the fifteenth century by the famous artist Leonardo da Vinci. However, his work focused more on entertainment than on practical information. This was also true of the French inventors Jacques de Vaucanson, who built a human-shaped machine that could play a flute in 1738, and Wolfgang von Kempelen, who constructed a mechanical chess system in 1769. During the next two centuries, these and similar robotic creations sparked the imaginations of many inventors, who made a wide variety of robotic devices and envisioned others that could perform functions in place of humans.

Early robotic devices had gears and pulleys. The addition of electronics in the 1930s enabled the development of the first true robotic arms. In 1938, an inventor named Willard Pollard patented a robotic arm that could spray paint, but his device was never manufactured. Also in the 1930s, another inventor, Harold A. Roselund, designed the first robotic spray arm put into use.

In the 1960s, General Motors installed the first industrial robotic arms in their Ternstedt, New Jersey, factory. The device—known as the Unimate—was designed by George Devol and marketed by Joseph Engelberger. This made Unimation, the company that made them, the world’s first robotics company. It sold 8,500 of the two-ton units that could diecast materials in factories before selling the license to Kawasaki in 1966. As manufacturers realized the potential of robotic arms to standardize and speed up the production process, more and more types of robotic arms were designed by countless other companies over the next decades.

Overview

A robotic arm replicates the maneuverability of a human arm. This limb has three major joints—the shoulder, elbow, and wrist—along with multiple smaller joints in the hand and fingers. These joints all move differently and perform various functions.

Early robotic developers in the 1960s borrowed nautical terms for the degrees-of-motion in robotic joints. These motions are known as pitch, yaw, and roll and refer to how a ship rocks from back to front and up and down. The shoulder joint has the widest range of motion and degrees-of-freedom of any joint in the human body, moving in all three of these directions. It is also the largest load-bearing joint in the arm. Duplicating these capabilities is key in any form of robotic arm.

The elbow joint helps the arm extend forward, retract backward, and reposition the hand so it can reach in different directions. Adding these motion capabilities increases the usefulness of a robotic arm. Some “elbow” joints of mechanical arms also add the ability to telescope or extend the length of the arm. This increases the abilities of a robotic arm beyond those of a human arm.

The wrist joint is vitally important in both human and robotic arms. It allows the end portion of the arm to move in three-dimensional space, which greatly increases its usability. While simple mechanical arms like cranes do not include wrist-type joints, the development of increasingly complex joints replicating the function of wrists was crucial to the design of the more complicated robotic arms used in contemporary manufacturing.

The “hand” of the robotic arm can be designed to perform a range of functions and provides the end-use capabilities of the arm. Some robotic hands have a device to spray paint, while others are equipped to cut or stamp metal, plastic, or another material. Still others have “fingers” or pincers that allow items to be grabbed, manipulated, or moved in other ways.

Robotic arms can be constructed with various combinations of these joints in whatever way will best suit the arm’s intended use. Most modern robotic arms include up to six main joints connecting as many as seven segments of the arm. Each joint is moved by a motor that is controlled by a computer that directs its specific function.

There are four main categories of robotic arms. Cartesian or gantry robotic arms, which have three joints that work together to position a tool or device in a particular location. These robotic arms are often used in machining parts or to pick up and position parts along a conveyor belt.

Cylindrical robot arms are designed so all their movements can be contained in an imaginary space shaped like an empty can or a cylinder. Anchored at the base, the arm moves up, down, and side-to-side performing its tasks, which often include the assembly of products and welding. Polar/spherical robotic arms are similar to cylindrical arms but are anchored to a swiveling joint, which creates a larger area in which the arm can work. These arms are also used for assembly and welding, as well as for diecasting processes. A selective compliance assembly robot arm or a selective compliance articulated robot arm (SCARA) has more refined abilities to restrict or expand motion. This makes it well-suited for assembly applications where care must be taken not to disturb other parts of the item. For example, SCARA arms can insert chips or other delicate components without damaging other delicate parts of the device.

Robotic arms can be designed to do everything from spraying large areas to manipulating the tiny parts of a circuit board to performing complex surgical procedures. These functions can be fully computerized, allowing the robotic arms to perform a wide range of functions. Some are also designed to be manipulated by humans using joysticks or other controllers. These are used in situations that pose hazards to humans, such as during space and underwater exploration and when handling explosives or infectious diseases. Robotic arms can also perform precise surgeries, with or without the direct control of a surgeon.

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