The six different types of manipulators in robotics

Cartesian manipulators

Cartesian manipulators, also known as XYZ manipulators, have three linear joints that use the Cartesian coordinate system—X, Y, and Z—to move in straight lines along these axes. This straightforward geometry makes them easy to understand and program.

These manipulators are often found in applications like 3D printing, milling, and laser cutting, where you need straight lines and precision. You'll mostly see Cartesian manipulators doing monotonous tasks that require a high degree of accuracy, like placing electronic components on a circuit board.

Pros: 

• The design is simple, making them easier to maintain and troubleshoot.
• Due to their straightforward geometry, Cartesian manipulators excel in tasks requiring high precision.
• They can handle substantial loads since the weight is distributed evenly across the structure.

Cons:

•  They can only move in straight lines, so if your application requires rotational movement, this isn't your best bet.
• They often occupy a larger workspace compared to other types, which can be a disadvantage in confined spaces.

Practical tip

When considering a Cartesian manipulator, evaluate the workspace carefully. If you have ample room and require precise, linear movements, this manipulator is an excellent choice. But, be cautious about using it in areas where multi-directional or rotational movements are necessary—Cartesian manipulators simply aren't built for that.

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Cylindrical manipulators

At first glance, cylindrical manipulators look somewhat like an arm extending from a cylindrical base. They have one rotary joint at the base and a linear joint that allows the arm to move vertically and radially. Their movement is based on cylindrical coordinates—hence the name.

You'll find these manipulators in action where there's a need for a robust and straightforward system. They're often used in applications like material handling, simple pick-and-place tasks, and some types of machine tending.

Pros: 

• They can handle various tasks without needing constant adjustments, thanks to their fixed base.
• With fewer axes to worry about, programming a cylindrical manipulator can be less complex compared to more articulated systems.

Cons:

• Their reach is confined to a cylindrical space, which limits where they can go.
• While they're efficient for specific tasks, they might not be the fastest option available, especially for complex operations.

Practical tip

If you're eyeing a cylindrical manipulator, consider the space in which it will operate. If your tasks fall within a cylindrical work envelope and don't require complex maneuvers, this type might be an ideal fit. 

But, if your application calls for agility or a broad reach, you might want to explore other options.

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Spherical (Polar) manipulators

Unlike Cartesian or cylindrical manipulators, spherical manipulators use a combination of rotary joints to move within a spherical workspace. 

They have a fixed base and usually two or three rotary joints, allowing them to cover a broad range of motions within that sphere.

You can find them in tasks requiring a bit more freedom in movement than cylindrical ones can offer but still within a confined space. Applications might include welding, spray painting, or basic assembly tasks.

Pros: 

• Their design allows them to move with greater range within a confined workspace.
• Because they operate within a spherical envelope, they're better suited for spaces where the footprint needs to be minimized.
• They usually require fewer parts than more complex manipulators, making them relatively economical.

Cons:

• While they offer more freedom of movement, they might not be as precise as Cartesian or cylindrical systems.
• Despite their fewer parts, the spherical geometry can make them a bit more complex to program than their Cartesian counterparts.

Practical tip

If you need something more dynamic than a cylindrical system but still somewhat limited in its working envelope, a spherical manipulator could be your go-to. Just be prepared for a steeper learning curve when it comes to programming.

SCARA manipulators

SCARA stands for Selective Compliance Assembly Robot Arm, and as the name suggests, these manipulators are particularly well-suited for assembly tasks. They have two parallel rotary joints that provide compliance in a plane, making them ideal for horizontal movements.

You'll commonly find SCARA manipulators in environments that require fast, precise horizontal movements. Think of applications like high-speed assembly, sorting, or even certain types of packaging tasks.

Pros: 

• SCARA manipulators are built for speed, especially in horizontal directions. They can execute tasks quickly, making them efficient for high-throughput applications.
• They are highly accurate, especially in horizontal plane movements.
• With fewer joints and simpler construction, they're generally easier to maintain than more complex systems.

Cons:

• They excel in horizontal tasks but are not designed for extensive vertical movements.
• These manipulators operate best within a specific plane, so if your task requires multi-plane movements, you might need to look elsewhere.

Practical tip

If your application revolves around quick, precise horizontal movements—say, an assembly line for small electronics—a SCARA manipulator could be a game-changer. However, if you require a lot of lifting or vertical positioning, you might be better off considering other options.

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Articulated manipulators

Articulated manipulators, or robotic arms, are the closest to mimicking the human arm, with rotational joints that can range from just two to more than ten. They offer a high degree of freedom, allowing for movements in multiple planes.

They are very versatile, so they are widely used across various sectors, from healthcare and research to advanced manufacturing and even entertainment. You'll see them in tasks that require a high degree of dexterity, such as surgical procedures, complex assembly, and even artistic endeavors like painting.

Pros: 

• Their wide range of motion makes them suitable for tasks that require complex movements and high dexterity.
• Despite their complexity, articulated manipulators often have a smaller footprint due to their ability to fold into themselves.
• Many articulated systems are designed to handle substantial loads, given their mechanical complexity and stability.

Cons:

• The multiple degrees of freedom make these systems complex to program and control.
• Due to their complexity, articulated manipulators are often more expensive than other types, both in terms of initial purchase and ongoing maintenance.

Practical tip

Before opting for an articulated manipulator, take stock of the complexity of tasks you're looking to automate. If your operations require a high degree of dexterity and versatility, then the articulated system can be a strong contender. However, be prepared for the associated complexities in programming and costs.

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Parallel manipulators

Parallel manipulators, sometimes called hexapods, are unique because they rely on multiple, parallel-linked arms working together. This structure enables the end-effector—the part of the robot that interacts with the environment—to maintain its orientation as it moves.

These manipulators excel in specialized applications like flight simulators, precision assembly, and medical surgery. Whenever you need high accuracy, stiffness, and a relatively compact footprint, a parallel manipulator could be a good fit.

Pros: 

• These manipulators offer high levels of precision due to their multiple arms working together.
• The parallel linkage provides a level of rigidity, making these manipulators stable even under load.
• Due to their architecture, parallel manipulators can be incredibly responsive, which is vital in applications like medical surgery.

Cons:

• Despite their precision, their operational space is typically smaller compared to other types.
• The parallel structure requires sophisticated control algorithms, making them more challenging to program and operate.

Practical tip

If your application demands pin-point accuracy and stiffness within a confined space, a parallel manipulator could be a strong option. However, make sure you've got the expertise to program and maintain such a complex system, as it's not as straightforward as dealing with some of the other types.

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Conclusion

Selecting the right manipulator for your robotic application isn't a task that should be taken lightly. Your choice can have far-reaching implications on efficiency, cost, and the overall success of your operation. 

By understanding the characteristics, advantages, and limitations of different types of manipulators, you're better equipped to make an informed decision that aligns with your specific needs.

Whether you're aiming for speed in a high-throughput assembly line or precision in medical procedures, there's a manipulator out there tailored to your requirements. The key is to critically assess your operational demands and match them to the manipulator that offers the best synergy.