Lightning-fast cobot through active energy management 

Germany's Gerhard Schubert GmbH showed at Interpack 2023 a pick&place cobot that managed to make up to 90 picks per minute. Traditional drive and control technology did not offer a solution because the very short start and stop cycles led to very high power losses and associated heat generation. The solution was found in the active energy management system PxtFX from the German company Koch, represented in the Benelux by Elincom Electronics. A simple solution for servo and AC drives that is capable of storing braking energy at lightning speed and making it available again just as quickly.

Automation in the packaging industry, among others, is of great importance to achieve the desired speeds, without the need for a lot of manpower. Cobots are a rewarding solution in this regard. 

Cobot tog.519

The current generation of cobots is easy and flexible to program, but developments are (far) from over. Gerhard Schubert, for example, focused on a lightning-fast cobot called tog.519. The naming is a combination of the English "together," a reference to the five axes, and the year of construction of the first prototype: 2019. The company's requirements for the cobot were no mean feat: 90 picks per minute, a 700-gram product and high-accuracy placement. 

These requirements affected both the mechanics and the drive and control electronics. In the end result, the resilient mechanics can withstand accelerations of up to 7G and allow a movement radius of up to about 760 mm. In the process, the cobot remains stable. The computational speed in image processing is also high to maintain the process speed of the entire system. 

In drive and control technology, the company ran into the limits of the selected drives: two 400 V drives for the two main axes and three 48 V drives for the three secondary axes. The bottleneck lies in the extremely high accelerations and decelerations that the drives must must muster to achieve the fast cycle times. Initial attempts were made to combine a servo amplifier with excellent heat dissipation with braking resistors. However, the latter resulted in very high power losses due to the enormous heat generation and, consequently, a particularly short service life of the drives. 

Active energy management PxtFX 

The solution was found in the application of Koch's PxtFX active energy management system. In short, this compact module is able to actively and quickly transfer the braking energy released during deceleration to a capacitor. This in turn can return this energy at lightning speed when the system needs to accelerate. This happens completely autonomously and so quickly that the DC link voltage only drops when the capacitor is empty and the system has to draw energy from the power supply (battery or mains). In concrete figures, over 1 kJ of kinetic energy is released in one pick and place cycle; that is, two accelerations and two decelerations. At speeds of up to 90 cycles per minute, this results in significant energy savings.

Secondary benefits

By choosing the PxtFX, the company also benefits from some additional advantages. For example, the low heat generation makes the cobot also usable in the food, cosmetic and pharmaceutical industries. There are also no hot components such as brake resistors. Furthermore, the load on the drive electronics is lower due to a controlled and governed voltage profile, which benefits the service life. Not to mention, the capacitor can briefly act as a UPS when minor mains failures occur. The cobot then does not fail, but can simply continue its work - at lightning speed.

Finally, the energy management system is compact and reliable, making it suitable for industrial applications with high demands. To further increase reliability, the Pxt solutions can be equipped with permanent capacity monitoring of storage capacitors. This predictive maintenance function warns when a predefined minimum capacity value is reached. There is then sufficient time to carry out maintenance and continue operating the application at full capacity.