Cobots: Human-machine teamwork

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They not only carry out programmed processes, but also respond to people: Collaborative robots (Cobots) with efficient sensors open up new forms of cooperation in production and service delivery.

The International Federation of Robotics (IFR) predicts that by 2020 the number of industrial robots worldwide will rise from the current 1.8 million to three million. China is by far the largest robot market. The strongest growth at present is in Japan, South Korea, and Germany. In South Korea, there are already more than 600 robots for every 10,000 industrial employees. In Germany, there are 309 robots per 10,000 factory workers. In the automotive industry there is even one robot for every ten workers and this trend is rising.

From gripper arm to work buddy

However, conventional industrial robots now have competition. In many industrial nations, full automation is already well advanced. On the other hand, partial automation still has a lot of potential, especially in the area of human-robot collaboration (HRC).

Collaborative robots – or cobots as they are known – are gaining ground in all sectors of industry. As opposed to traditional industrial robots that work in enclosed areas, humans and robots share the same working space in MRC scenarios with no separating protective fence. Cobots are integrated in existing production lines where they assist the employees in their work. In many cases, they even have physical contact with the employees.

Robots are only now able to interact with humans because they are equipped with smart sensors that enable them to perceive their surroundings and respond to changes, such as people moving. Advances in materials science and in the field of semiconductors have also considerably increased the processing power of collaborative robots over the past few years. In addition, biologically inspired technologies have created new momentum. Soft robotics is based on soft, organic structures and aims to imitate natural movements.

Intelligent work sharing

HRC applications combine human skills, such as experience, the ability to learn and make decisions, versatility, and improvisation with robot abilities like strength, precision, and speed. While the robots carry out monotonous, physically exhausting, or health-endangering tasks, human employees can focus on other work.

At Audi, for example, an adhesive application with robot assistance – known as KLARA – helps employees install CFRP roofs in coupes. The robot recognizes when a human is touched and automatically stops any movement in dangerous situations. If there’s a malfunction, the light ring of the cobot turns red. In the production halls of many car makers, buckling arm robots hand skilled workers tools for complex installations. Daimler uses lightweight robot arms in axle production.

Safety technology and standards rather than protective fences

When humans and industrial robots work together in small spaces, strict safety regulations are enforced to minimize the risk of employees being injured. As opposed to conventional, enclosed robot applications, in HRC applications, machines and humans are allowed to touch. However, this must not lead to injuries.

The most important technical requirements for safe interaction include smart sensors, reliable control of the robot, and safe drive functions. Plant safety is also defined in various standards, guidelines, and specifications. The requirements for safe robotics in the industrial area are defined in ISO 10218 “Safety of Industrial Robots” Part 1: “Robots” and Part 2: “Robot systems and integration”. These are available in German as EN ISO 10218-1:2011 and EN ISO 10218-2:2011.

Technical specification ISO/TS 15066 “Robots and Robotic Devices – Collaborative industrial robots”, which has supplemented EN ISO 10218 since 2016, helps in the implementation of HRC applications: With the corresponding safety concepts it is possible to implement four cobot operating modes – from coexistence to collaboration: With “safety-rated monitored stop”, the cobot stops immediately if a person enters its working area. In “hand guiding”, a human controls the robot manually, such as with a joystick, giving the human complete control at all times. In “speed and separation monitoring” mode, sensors monitor the distance between humans and robots and adjust the robot’s speed accordingly.

If the safety gap becomes too small, the robot automatically moves slower. In other words, there is basically no chance of a collision between a human and a robot with these three operating modes. However, the situation is different with the operating mode “power and force limiting”. This is collaborative robotics in the narrower sense – the supreme discipline in which humans and machines work together directly without damaging each other. When a human enters the working area of the robot while it is moving, contact between the human and robot is possible, whether intentionally or unintentionally. In this operating mode, sensory, mechanical. or electronic limiting of force and power in case of a collision must be ensured using the “force atlas” of ISO/TS15066.

The body region model: How hard may a cobot “hit” someone?

Collisions can be cushioned through various measures. The most important preventive measure is to reduce the robot’s movement. In other words, the dynamics and force of the robot’s movements are limited to a great extent so that there is no chance whatsoever of a person being injured. The movement range can be adjusted in order to prevent injuries to sensitive parts of the body. Safety can also be increased by rounding edges and corners, with padding and with large contact areas.

However, a measuring process is necessary to determine whether possible collisions could cause pain or injury. ISO/TS 15066 regulates the permitted level of pain. Annex A of this standard contains a body region model with 29 body regions. For each area of the body, such as head, hand, or leg, there are limit values or pain thresholds with regard to force and pressure. The face is the body region with the lowest permitted collision values. The maximum permitted force here is 65 newtons. Pressure must not exceed 110 N/cm2. The biomechanical limit value for the tip of the index finger is much higher, at 300 N/cm2.

CE marking by user

According to the Machinery Directive 2006/42/EC, a robot is an incomplete machine. It is only when the robot system is fitted with the tool required for its application that it fulfills its purpose and is then regarded as a complete machine. The user or integrator thus becomes the manufacturer of the machine and is responsible for the CE mark, including safety test. The requirements for the safety concept always depend on the respective application. In addition to the risks from the robot itself, spontaneous, incalculable movements of the machine must also be considered.

Service robots booming worldwide

At present, industrial robots dominate. But industry observers assume that in just a few years, service robotics could overtake industrial robotics. The International Federation of Robotics predicts average growth in sales of between 20 and 25 percent per year through to 2020. The most interesting areas of application in this segment are logistics, agriculture, medicine, care, and rehabilitation. For example, with stroke victims, certain areas of the brain could take over the tasks of other areas that are not functioning properly. To do this, movement sequences have to be repeated up to 40,000 times. Service robots rather than human physiotherapists could train the patients at home. Exoskeletons are increasingly counted among the professional service robotics applications. The IFR expects to see sales increases of between 30 and 35 percent per annum for private applications. Currently, mass products are limited to vacuum cleaners, lawn mowers, and edutainment.

Collaborative robotics is changing job descriptions

Will robots and cobots take work away from humans? According to an estimate from the Institute for Employment Research (IAB) of the German Federal Employment Agency, in Germany, the transition to Industry 4.0 will destroy about 490, 000 traditional jobs by 2025. However, through the increase in productivity resulting from automation, 430,000 new jobs will be created. In any case, the increasing use of robots in production processes will change job descriptions. On the one hand, humans will be relieved. On the other, they will constantly have to learn new skills at very short intervals to keep up with the rapid rate of innovation.

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You can find out more about collaborative robotics in medicine at the electronica Medical Electronics Conference.