KUKA Robots On-Site
Within a relatively short time span, industrial robots have turned from an exclusive tool for high-end industries to a multifunctional machine for a wide range of users, from small and medium enterprises to architectural and industrial design offices. The demands of these users differ significantly of how robots are used in the automotive industry, with robots working on-site and even in the close proximity of human workers. New technological advances are required to cover these needs, from light-weight robots with an array of sensors to mobile platforms that can autonomously move heavy robotic arms with millimeter accuracy.
KeywordsKUKA Lightweight robot Soft robotics Mobile robot platform Robotic arms Man–machine collaboration Collaborative robotics
Nearly 40 years have passed since the presentation of the KUKA (http://www.kuka-robotics.com) FAMULUS, the first industrial robot to use the now standard setup of six electric motor-driven axes. In this timespan, industrial robots have become faster, more efficient, and more accurate—but most importantly also more affordable and accessible. Where the use of automation and robotic arms used to be the domain of large industries, now even small firms and offices can afford robotic arms and benefit from automation. This is not only made possible by the affordable prices, but also through new interfaces, sensors and strategies that safely enable the accessible programming of industrial robot, by e.g. allowing the direct import of G-code or utilizing new, visual programming strategies for defining robotic tool paths.
This development brings along new possibilities, but also new challenges. Where an automotive welding line is largely unattended, new applications may see robots in much closer proximity to, and collaboration with, human workers. Similarly, there is a great potential in allowing robots to work on-site or even to move themselves autonomously on-site, significantly increasing the flexibility of these multifunctional machines.
New technical solutions that go beyond current industrial robots will be required to realize these goals.
2 Lightweight Robots
It was initially developed at DLR for use in non-structured environments and interaction with humans (Albu-Schaeffer et al. 2007). Where common robotic arms depend on position control via position sensors on the motor side and current measurements, the KUKA LWR implements compliance control with position sensors on the motor side as well as position and torque sensors on the output side. Instead of relying on a stiff design of the mechanical structure, the LWR achieves high stiffness through active vibration damping.
In compliant mode, these sensors allow the user to program the robot manually—not through the KUKA control panel, but by physically moving the robot’s joints (Bischoff et al. 2010). More importantly, the sensors enable the robot to continuously monitor itself and to stop when certain torque thresholds are exceeded or unexpected objects are sensed. In the case of a collision, where most other robots would seriously injure a person in its path, impact tests with the LWR show only a very low injury level even at its maximum speed of 2 m/s (Albu-Schaeffer et al. 2007). These results are also made possible by the special design of the LWR, relying on a soft silhouette with rounded edges to offer increased protection.
An additional benefit of the soft-robotics model is that it can be used to deal with inherent product- or material tolerances. With a regular, “stiff” robot, positioning data has to be completely accurate, requiring expensive equipment such as laser scanners. Inaccuracies can lead to damage of the material or even the robot, e.g. when a workpiece does not fit perfectly into a mounting element. Using impedance control, the lightweight robot itself is able to react to resistance, e.g. by rotating or slightly shifting the element, instead of forcibly moving along the preprogrammed path. This system is successfully applied for the assembly of complex gears in the automotive industry.
The most current iteration of the lightweight robot is the KUKA LBR iiwa—the intelligent industrial work assistant—that is available with payload capacities of 7 and 14 kg, making it the first lightweight robot for industrial use with a payload capacity of over 10 kg. It is also the first robot to implement KUKA.sunrise, a single controller kernel with modular, open interfaces, enabling object-oriented programming of complex robot systems, including safe, sensor-based, multi-kinematic systems.
3 On-Site Robotics
In the area of service robotics, the combination of robotic arms with a mobile platform to expand the robot’s workspace (see Sect. 2) is very common. However, doing so with larger, industrial robots is complicated due to their high weight—the easiest way to increase a robotic arm’s workspace is therefore the use of additional rotational or linear axes, which either rotate the workpiece or linearly move the robot itself. While these external axes are robust and proven technology, they again constrain the movement of the robot and cannot easily be moved or expanded.
In 2013, KUKA presented the moiros concept, which combined existing, state-of-the-art components to create an industrial robot with an unconstrained workspace, capable of working autonomously for over 8 h due to its high-powered, 20 kWh battery system.
A mobile system is therefore able to adapt itself to the size of the building elements and can be utilized flexibly, e.g. in different fabrication sites, depending on demand. Especially interesting is that the moiros concept only uses existing component that are already available on the market, making large-scale mobile robotics immediately possible.
In the past years, many new technologies were developed that will over time become industry standards. Especially the new KUKA LBR iiwa pioneers innovative collaborative robot concepts that are expected to enable projects that go far beyond of what we are using robots for at the moment.
With the ongoing demographic change, service robotics will not only find their way into our homes to support elderly care, but will also become increasingly important for small and medium enterprises, either as a third-hand for workers or as fully automated machines that perform separate tasks—but integrated into a shared space, not within an enclosed cell. However, the challenges for achieving this man–machine collaboration with robots are not only of a technical nature, but also regulatory issues, as many safety regulations still prohibit workers from entering a robot’s workspace. Over time, new regulations will have to be found that take advanced safety measures into account.
Already, technology pioneered by the lightweight robot family of robot is beginning to filter down to the more common robot series such as the KUKA KR AGILUS, switching either an axis or a Cartesian direction to a soft mode.
Especially in the creative industry, where factories are not built around robots, but robots are now progressively introduced, factors such as user-safety, light-weight, and waterproofing will greatly facilitate many processes.
- Bischoff R, Kurth J, Schreiber G, Koeppe R, Albu-Schäffer A, Beyer A, Eiberger O, Haddadin S, Stemmer A, Grunwald G, Hirzinger G (2010) The KUKA-DLR lightweight robot arm—a new reference platform for robotics research and manufacturing. In: Proceeding of: ISR/ROBOTIK 2010Google Scholar