Defining robot movement

You're probably wondering what exactly "robot movement" means. 

In short, it refers to the physical motion and mobility of robots. The way a robot moves depends on its configuration and joints. 

The major types of motion are:

1. Linear
2. Rotational
3. Cartesian
4. Cylindrical
5. Spherical
6. Articulated
7. Selective Compliance Assembly Robot Arm (SCARA)
8. Delta

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Types of robot motion

There are many types of motion used in robotics, and each is ideal for different tasks. Let's explore the main ones:

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1. Linear motion:

This is one of the most basic ways a robot can move, similar to a train on a track:

• Straight-line glide: The robot smoothly travels along a single axis, perfect for transporting materials or tools in a straight line.
• Extension and retraction: In some robots, the arm segments extend and retract to reach different points along the path, like a telescope adjusting its focus.

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2. Rotational motion:

Picture a spinning top or a dancer twirling — that's rotational motion. It works like this: 

• Joints in motion: Robots have joints, just like our shoulders, elbows, and wrists, that rotate to enable flexible and controlled movement.
• A full spin: Some bots have a rotating base, allowing a complete 360-degree turn of their entire arm.
• Precise maneuvering: This motion type allows for super-intricate tasks like assembly, product handling, and packaging, where accuracy is key.

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3. Cartesian motion:

Think of a chessboard or a 3D grid — that's a good way to picture Cartesian motion:

• Grid-like movement: The robot moves along three perpendicular axes (X, Y, and Z), covering a large work area — much like a 3D printer or a robotic arm on an assembly line.
• High accuracy: These robots have very precise movements and rigid structures, which makes them perfect for tasks that demand high levels of accuracy, like welding and assembly.
• Defined workspace: Cartesian robots typically have a fixed base, so their movement is limited to their predefined work area.

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4. Cylindrical motion:

Cylindrical motion, in a nutshell, is a twisting tower crane combining vertical and horizontal movements like this:

• Vertical lift and horizontal rotation: The robot has a vertical column for lift and a rotating arm to move around the column, creating a helical path.
• Curvy moves: This design is perfect for tasks that involve curved surfaces or require the robot to follow a circular path, like wrapping or painting cylindrical objects.
• Flexible like a yoga teacher: Independent control of vertical and rotational movements gives cylindrical robots a wide range of motion and adaptability.

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5. Spherical motion:

Spherical motion works in a way akin to the ball-and-socket joint in your shoulder:

• Three-axis rotation: Three rotational joints intersect at a single point, allowing the robot to move its end-effector in any direction.
• Unrestricted movement: This type of motion offers an incredible range of movement, similar to a human shoulder joint.
• Complex tasks made easy: With spherical motion, robots can effortlessly handle intricate assemblies or navigate obstacles.
• Precision control: Getting the desired movement requires precise coordination of the rotational joints.

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6. Articulated motion:

Mimicking the movement of a human arm, articulated motion enables robots to bend, twist, and extend their arms with multiple joints:

• Multiple rotary joints: Typically featuring four to six rotary joints, these robots have a wide range of motion and flexibility.
• Human-like skill levels: These robots can perform complex tasks requiring pinpoint movements, like picking and placing delicate objects.
• Super versatile: Articulated robots are popular in a wide range of industries, from manufacturing to healthcare, for jobs like assembly, welding, painting, and more.

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7. SCARA motion:

Selective Compliance Assembly Robot Arms (SCARA robots) are the speed demons of the robot world, known for their rapid and precise movements:

• Two rotational joints: SCARA robots have two rotational joints that allow for quick and precise movements in a horizontal plane.
• The speedsters: They excel at tasks that require high speed and accuracy, such as electronics assembly, pharmaceuticals, and medical applications.
• Wide reach: With their extended arms and rotational joints, SCARA robots can cover a large work area, which makes them a good fit for a wide range of tasks like assembly, picking and placing, etc. 

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8. Delta robot motion:

These parallel robots are known for their speed and agility — pretty much three-armed ninjas. 

Unique features of delta robot motion are:

• Three arms, one base: Delta robots have three arms connected to a common base, allowing for rapid and precise movements.
• Lightning-fast pick and place: They are the go-to choice for high-speed pick-and-place operations, such as packaging and sorting.‍
• Parallel design for precision: The parallel structure of the arms nearly guarantees constant accuracy and stability, even at high speeds.

Factors that affect robot motion

The major factors influencing how a robot moves are its joint types and degrees of freedom. 

Robot joints, like elbows and shoulders, can rotate, slide, or both. Their range of motion determines the robot’s skill level.

Robot joints that can only rotate, known as revolute joints, provide rotational motion. Prismatic joints, on the other hand, can only slide to enable linear movement. Some robots have hybrid joints that combine rotation and sliding for added flexibility.

A robot’s degrees of freedom refers to the number of directions in which it can move. 

The more degrees of freedom, the more complex the motion. Industrial robots typically have 4 to 6 degrees of freedom, with 3 positions (x, y, z) and 3 orientations (roll, pitch, yaw).

Other factors impacting a robot’s movement include:

• The kinematic structure is how its joints and links are arranged. Serial kinematic chains have a straightforward arrangement, while parallel structures, like Delta robots, enable fast, dexterous motion.
• The actuators are the mechanisms driving its joints, such as electric motors or hydraulic actuators. More powerful actuators allow for higher speeds, larger payloads, and higher precision.
• The control system includes the hardware and software coordinating its motion. Advanced control systems using techniques like PID control and path planning enable precise, responsive, and autonomous movement.

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Programming robot motion

Robot movement is controlled by specialized computer programs that direct the robot's joints and manipulators. 

Programming a robot's motion necessitates a complete understanding of the robot's degrees of freedom — the number of independent movements it's capable of — as well as its kinematics.

The programmer must specify the path the end-effector (robotic hand or tool) will take to accomplish the required task. They define a series of waypoints the robot will move between, using linear or joint interpolation. Waypoints are connected by straight line paths for linear interpolation or curved paths for joint interpolation, allowing for smoother motion.

The speed, acceleration, and deceleration of the robot along the programmed path must also be defined if you want to get quick, precise, and safe movements. 

Programmers typically create code using languages like C++ or Python and customize it for the specific robot and its control system. Simulation software is often used to test and troubleshoot the program before executing it on the actual robot.

Keep in mind that more modern robots can use drag-and-drop interfaces, teach pendants (you show the robot, and it replicates your movements) or revolutionary no-code interfaces. None of these require programming knowledge. 

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Summing up

That was a crash course on the inner workings of robot movement and motion types. From linear to spherical, rotational to articulated, we covered all the key types of motion that give robots their signature action capabilities. 

While you may not be ready to build and program a robot just yet, you now have a solid base of knowledge — unless you choose to go with a bot with a no-code framework. 

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Next steps

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