Collaborative robots work in close proximity to humans – even as a team. The interaction between humans and machines is thus very close and direct. The robot has a multitude of sensors that allow it to perceive the human and adjust its movements accordingly.
What is a cobot?
A cobot, or collaborative robot,is a robot that possesses a range of safety features and characteristics that allow it to worknot only in proximity to humans but often also in collaboration with them.
In recent years, a new generation of robots has been pushing its way into the market, enabling the automation of processes while remaining cost-effective and allowing uncomplicated collaboration with humans: the cobots. Professor Robert Grebner, president of the University of Applied Sciences Würzburg-Schweinfurt, says, “Cobots are an important next step towards automating complex motion sequences. Wherever physically demanding and monotonous tasks occur, cobots will ease the work for humans by being integrated into work processes.”
To ensure human safety, almost all cobot components are equipped with sensors to detect humans, making all cobots an extensive Human Machine Interface. Unlike with classical robotics applications, this avoids the need for protective fences or similar barriers.
32 percent increase each year
The global market for cobots is set to grow from 1.23 billion US dollars in 2022 to 11.04 billion US dollars in 2030
Source: Grand View Research
Perception of the environment
Sensitive force monitoring continuously checks the torque and speed of various drives. If the robot encounters an obstacle – which can also be a human – the movement is either stopped immediately or continued very carefully and gently. Additional sensors enable the perception of the environment. Robots can thus adapt their way of working early on when a human approaches. For example, the Swedish lighting manufacturer Fagerhult Belysning currently has three Motoman cobots in operation. The robots, each with a load capacity of ten kilograms, take over complex assembly steps among other tasks. The unique thing about the cobots is that they can switch between the classic full-speed industrial robot mode and a safe collaborative mode. Safety scanners detect if an employee approaches the defined safety area and then slow down to a safe pace.
The closer, the slower
The “sBot Speed” safety system from Sick also enables adaptive perception of the environment: laser scanners and a safety control system guide the robot so that it slows down the closer a person moves into the robot’s working area – until it comes to a complete stop. The ability to automatically adjust the robot’s operating conditions to the position of people in the environment protects against accident hazards while simultaneously improving productivity, as downtime is reduced and workflows are optimised.
Smart safety zones
A research team from the Fraunhofer IWU is pursuing a slightly different approach. They have divided the robot’s perception areas into smart zones. With faster movements, such a zone “grows” to exclude the risk of collision with humans. Lidar sensor technology (Light Detection and Ranging), which recognises and categorises objects using pulsed laser light, as well as cameras, are used for environmental perception. The combination of response times (Lidar: 50 milliseconds, camera: 10 milliseconds) and surveillance areas (Lidar: larger areas; camera: near field) now allows the robot to move faster. Although the speed must still be reduced when humans approach, it is considerably less than before: about 25 percent faster robot movements mean a significant gain in efficiency.
Efficient wiring of sensors
The numerous systems that ensure human safety require many cable connections for sensors and actuators in traditional robot architectures. The wiring effort can be significantly reduced by using FSoE technology, or Fieldbus Safety over EtherCAT. Fraunhofer IWU, NexCobot and Synapticon have jointly developed a corresponding safety architecture. It is decentralised and enables safe human-robot collaboration even when work situations change dynamically – with significantly reduced wiring effort. “An intelligent safety system monitors the relevant areas and adjusts the robot control situationally to any conceivable interaction between humans and robots,” emphasises Dr Mohamad Bdiwi, team leader of Collaborative Robot Systems at Fraunhofer IWU. Another advantage: given that the safety of the motion sequences is monitored directly at the drive axis, there is significantly less reaction time.
Hand-guided teaching
Cobots differ from classical industrial robots not only in collaboration but also in their interaction with humans during programming. Even a person who is not a robot expert should be able to quickly and easily “teach” the cobot a new task. On the one hand, this is done using graphical programming systems or apps for tablets or smartphones, which do not require specific training. Above all, however, the cobot learns the execution of certain tasks by the human literally taking it by the hand: the employee manually guides the robot arm through the required motion profile. Additional control buttons “on the wrist” are used to save the respective positions – so not every position has to be confirmed on the robot’s hand control panel. Thanks to so-called hand-guided teaching, the cobot is ready for use very quickly. So this really is a case of humans and machines working together hand in hand.
