Collaborative Robots

A cobot is a robotic arm that can work in close proximity to humans. It is designed to be safe by relying on lightweight materials, an inherent limitation of speed and force, or sensors and software. This design has the goal to prevent collisions or reduce the impact in the event of a collision. Though Cartesian robots and gantry robots are used interchangeably, gantry robots generally have two x-axes while Cartesian robots will have only one each of the two/three axes (according to the configuration).

Cobot stands for Collaborative (Co) Robot (bot), which refers to the safety of the robot. It is a robot that is built to collaborate with humans.

Choosing the right cobot requires a complete and comprehensive assessment. Therefore, here are some quick definitions of the specs to take into consideration to help you pick the right cobot that fits your requirements and needs.

1. Payload:
Payload is essentially the weight that the cobot can carry. All cobots have a designated payload which is calculated as the sum of the weight of the End Of Arm Tooling (EOAT) and the weight of the product being picked. Palletizing or handling heavy products require a big payload, while handling small electronics does not.

Advice: Much like a human, a cobot arm will be better able to handle a load closer to the body. This explains why it is important to compare load diagrams of different cobots. We recommend narrowing down the cobots considering just the payload, but when you have a shortlist of 5 cobots, make sure to put the load diagrams next to each other.

2. Reach:
The reach of a cobot is measured by the distance from the center of the cobot to the fullest extension of the robotic arm. It is an intuitive indication of the working area of the cobot. If your application is palletizing, you will need a large reach. If your cobot needs to pick and place objects close to each other, a low reach will do.

Advice: By filtering cobots on an estimation of payload and reach, you will easily narrow down your search by 80%. That is why payload and reach always need to be the starting point of your search.

3. Repeatability:
In technical terms, repeatability of a cobot is the positional deviation from the average of displacement. It is the closeness of agreement between several positions reached by the cobot’s end-effector for the same controlled position, repeated several times under the same condition. Essentially it is the cobot’s ability to repeatedly execute the same task or the accuracy of the cobot.

Advice: Just like payload, repeatability depends on the position of the end effector with respect to the cobot’s body. Hence it is important to take into consideration that the repeatability that is expressed as a single value, is actually a spectrum. The smaller the repeatability, the more accurate the cobot, but also the more expensive. Therefore it is important to consider the needs of your application to choose the accuracy that is needed in the position that it is needed.

4. Ease of Use:
Cobots are much easier to program than conventional industrial robots. For cobot programming, it is often not necessary to write code, due to the software being intuitive. There are for example options for teaching by demonstration. This means that you would have to manually show the robot what to do by holding the cobot arm in your hands, like you would hold a child’s hand to demonstrate a movement. The steps include downloading a cobot software application and creating tasks in it, then teaching the cobot the specific movements that you would like to perform while recording them in the application. Reprogramming during production can also be carried out easily if necessary.

Advice: Ease of use is very important aspect to consider while making a purchasing decision of a cobot. The reason is that the programming salaries still make up for a big chunk of the budget. Faster implementation means a lower project price. But it also means less downtime if the plant engineers know how to reprogram the cobot for a new application without the need of an external integrator. While the previous parameters (payload, reach, repeatability,...) are parameterizable, ease of use is much more difficult to put a value on. It is a subjective parameter, which is why Qviro gathers product reviews to reveal the ease of use of cobots.

5. Quality of Documentation:
Documentation means all content available to assist during setup, programming, use or maintenance of a cobot. The documentation can be in different formats like datasheets, instruction videos, manuals, FAQ pages. High quality documentation results in successful projects with little or no contact with the supplier.

Advice: Visit the Qviro product page of the cobots you are interested in. The resources you find give a first impression of how well the supplier's documents prepare you for implementation. You can also have a look at the supplier’s website. The best way to know if a cobot has good documentation is to talk to people who have used the documentation during a project. That is why Qviro surveys people and asks them to rate the quality of documentation. Make sure to have a look at the reviews on the product pages.

6. ROS:
ROS (Robot Operating System) is a flexible framework for writing robot software. It is a collection of tools, libraries and conventions that aims to simplify the task of creating complex and robust robot behaviour across a wide variety of robotic platforms. Choosing a cobot that can run ROS will make things significantly easier.

7. Communication Protocol Possibilities:
Communication Protocols are a form of communication between a cobot and an operator or between a cobot and another cobot. With the rise of cobots, it is more and more common to witness cobots take on more intricate tasks. For example, this creates a potential situation where cobots are to interact with other cobots which requires a mode of communication to uphold efficiency and rapid production times. Hence there are a range of communication protocols that are suitable for a cobot, for example, I/O, Fieldbus, TCP/IP, MODBUS, ProfiNet, EtherNet/IP and XMLRPC just to name a few.

8. Offline Programming Possibilities:
The newest cobots tend to not use any programming. As mentioned in point four, cobots learn their tasks from their human operators. This is carried out by the operator manually showing the cobot the steps needed to complete the action or task required of them.

9. Compatibility:
When it comes to compatibility, choosing the right tool to go hand-in-hand with the cobot is crucial for the job you would like to perform. Whether it is assembling, positioning, picking up, or cutting and what kind of actions are required. Whilst selecting tools, it is important to take into consideration the shape and size of the workpiece, payload limits, target cycle time, and actuators. These factors are all interdependent. Some cobots are compatible with almost end-of-arm tools, whilst others are limited to specific brands.

Advice:
1. Always choose all products required for your project at the same time.
2. Think about the future, you might use the same cobot for different applications and cobots that are compatible with a lot of brands offer more flexibility.

10. Unique features:
There are a plethora of varying types of cobots, each unique and fitted with distinctive features. For example, there are cobots that possess built-in vision systems (f.e. Techman's cobots) specifically for pattern recognition, object positioning and barcode identification. Another example includes dual-arm cobots (f.e. ABB Yumi) that are flexible collaborative work for space, gestures and collaboration methods. Dual-arm cobots allow for multi-objective optimization in respect to optimal collaboration.

With all these various factors to consider when examining your next cobot purchase, Qviro makes these criteria transparent with reviews of real users. This encapsulates what Qviro intends to do, to help users make the most confident of decisions on their next cobot purchase.

Collaborative robotscome in four different types: Power and Force Limiting, Safety Rated and Monitored Stop, Speed and Separation, and Hand Guiding. Each of these types meets the standards set by the ISO Cobot Safety Guide. That means they can all work safely alongside humans.

Yet they also have their differences. Take the example of the Power and Force Limiting cobot to understand this point. It stands out from the rest due to its additional sensors. These sensors help it use standard industrial robots while remaining safe for human-cobot interaction.

The other three cobots lack this functionality. Though they make up for this ‘shortcoming’ by offering unique features of their own.

1. Power and Force Limiting Cobots:
Power and force limiting cobots stop operation on sensing contact with people. They have smart collision sensors and are equipped with physical features to prevent or minimize damage or injury in the event of contact. This allows them to work with (or near) humans.

Once a risk assessment ensures that it’s safe to use them, power and force limiting cobots won’t require any safety devices like vision systems, barriers, and external scanners. This reduces their upfront cost as you don’t have to purchase a plethora of safety equipment with them.

That isn’t to say that everything is great about these cobots. They are slower, smaller, and less powerful than the other three types of cobots. You cannot count on them to handle massive payloads either. Nor are they famous for their precision, which is currently lower than other cobots.

Pros:
1. Have smart collision sensors
2. Can safely work alongside humans
3. Require lower investment

Cons:
1. Cannot handle a massive payload
2. Types of power and force limiting cobots

• Joint Sensing

These cobots use joints to monitor the forces applied to their body. Some collaborative robots use force-torque sensors to accomplish this objective, others rely on the current of their motor. They are extremely easy to operate and are by far the best choice for human-cobot interaction.

• Skin Sensing

These cobots use tactile sensors to monitor the forces that might be applied to their body. Upon sensing potential impact, the sensor sends instructions to the cobot to stop moving, thereby preventing collisions. They are relatively difficult to operate than joint-sensing cobots but are equally safe.

• Force Sensor Base

These cobots provide the best of both worlds. On the one end, they are capable of handling massive payloads. On the other, they still provide a good enough level of sensitivity to work safely alongside humans. Though adjusting these cobots isn’t easy when compared to joint sensors.

• Inherently Safe

Their name makes it clear what ‘inherently safe’ cobots are all about. They cannot hurt their fellow human workers in most ways imaginable, mainly because they only handle low payloads. Though the end-of-arm-tooling (i.e. a welding tool) you might be using with them could affect their safety level.

2. Safety Rated + Monitored Stop Cobots
These cobots detect when a person has entered a shared workspace and stop working until the individual leaves the designated area. You won’t have to manually restart them by pressing a button – they’d automatically resume the task once the person has left.

This lets the worker complete their task with the knowledge that their safety won’t be endangered while they are in the shared workspace with the cobot. The cobot only will spring back to life either when they leave the area or if they pushed a button.

Safety rated + monitored stop cobots are for workspaces that involve minimal cobot and human interaction. That’s because they aren’t very good at collaborating with humans, although they do ensure human safety and also provide the convenience of automatically resuming operation.

Pros:
1. Ensure human safety
2. Automatically resume operation

Cons:
1. Aren't very good at collaborating with humans

3. Speed and Separation Cobots
Speed and Separation cobots work on the same principle as their Safety Rated counterparts but allow more cobot-to-human interaction. They have a vision system constantly monitoring the work area, divided into ‘’warning zone’’ and ‘’stop zone”.

As a person enters the “warning” zone, the cobot slows down but continues working at a reduced pace. It will continue doing so unless the vision system detects presence in the ‘’stop zone”, after which it would signal the cobot to halt its operation.

The majority of speed and separation cobots you see on the market come with attached vision systems. This allows them to operate seamlessly. Some, like the TM Robot, are equipped with a built-in vision system to save you from spending extra on additional installments.

Pros:
1. Leverage industrial robots
2. Collaborate with human worker

Cons:
1. Pricier than Safety Rated Cobots

4. Hand Guiding Cobots
Hand guiding cobots come with a ‘hand-operated’ device using which the operator controls their movement and ‘teaches’ them tasks they’re required to perform. They are easier to reprogram than other collaborative robots, most of which require the recoding of their systems.

What’s more, since these cobots can be taught quickly, downtime is limited with them. This is incredibly useful in scenarios where the cobot has to be programmed (or reprogrammed) on the fly. However, if the cobot isn’t force limited, safety guarding should be in place to protect the human operator.

Pros:
1. Easy to reprogram
2. Limited downtime

Cons:
1. Require proper safety guarding if it isn't a force limited cobot

1. Palletizing:
Palletizing is the process of loading products on or unloading products from pallets. It is a very repetitive and ergonomically hazardous task for humans.

Cobots are used for palletizing because their ease of programming and installation makes it possible to use a cobot on different production lines on one day. Cobots don’t require fencing which makes it easier to be activated where needed.

2. Picking and Placing:
Picking and placing is the process of picking up parts and placing them in another location. It is a very repetitive task.

Cobots are used for picking and placing in order to increase production rates and for consistency. Cobots can be used alone if the location of the parts is known or in combination with advanced vision systems to identify the location of objects.

3. Assembly:
Assembly is the process of putting parts together to make another product. Bolting, screwing, part fitting and insertion are examples of assembly tasks. Assembly can be repetitive and unergonomic, especially when workers handle heavy tools to drive screws and nuts.

Cobots are used for assembly because they can move heavy tools faster than humans. Because of their force-sensing they can ‘feel’ when tightening is complete in order to avoid an overload of torque.

4. Machine Loading:
Machine (un)loading, also called machine tending, is the process of supplying and placing parts into a machine so that the machine can perform an operation on the part. Examples of machines are CNC machines, injection molding machines, press brakes, stamping presses. There is a risk of injury associated with working in close proximity to heavy machinery.

Cobots are used for machine loading to reduce operation costs and to reduce accidental injuries.

5. Welding:
Welding is the process of fusing together two or more parts by means of heat, pressure or both forming a join as the parts cool. Welding requires very skilled operators.

Cobots are used for welding because they have the ability to create a longer, continuous weld seam and there is the opportunity to have a lower cost per part.

6. Polishing and grinding:
Polishing and grinding are processes of rubbing a surface to make it smooth. They are precision jobs that require experience. Workers are exposed to an unhealthy working environment.

Cobots are used for polishing and grinding because they have an internal force-feedback system that allows for a precise treatment.

7. Gluing and dispensing:
Gluing and dispensing are processes of applying a liquid to a part. Dosing the amount and dividing the liquid evenly make the process a precision task.

Cobots are used for gluing and dispensing in order to waste less material, reduce rework and improve cycle times.