Mobile Robots Taken From The Energy Chain

2023 Author : Hannah Pearcy | [email protected] . Last modified: 2023-05-24 11:12

Detect products automatically, grab them safely and get them to their destination quickly: Portal robots are considered a tried and tested means for the intralogistic material flow within a machine or application. While machines and systems used to be connected to each other in many production facilities over long travels by conveyor belt or person-guided vehicles, mobile transport systems can now easily overcome such routes. However, they are usually connected to energy transmission systems such as conductor lines or drag chains.

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The machine builder EMAG in Salach, 50 km east of Stuttgart, has designed portal robots together with SEW-Eurodrive. Drive technology and communication were literally taken off the chain. The energy supply chains that are currently known in portal systems are a thing of the past in current developments.

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A novelty that could be realized because SEW-Eurodrive can enable optical and inductive ways of signal and energy transmission. SEW-Eurodrive is established in the market with energy-efficient drive and automation components. The still relatively new business area "Maxolution Machine Automation" is now additionally pursuing the goal of serving selected industries with customized system solutions from a single source. The company from Bruchsal shows the advantages of bundling competencies with the robot portal without energy supply chains.

Cartesian portal: quieter and more flexible

Using a Cartesian portal, SEW-Eurodrive demonstrated for the first time almost a year ago to the public which solutions with today's technology are all possible if intelligent software with reliable mechatronics are combined to form fully integrated solution packages.

What immediately catches the eye in such an intralogistics application with contactless energy transfer is the drive concept with which the portal robots are traveling on the rails. It is striking because several robots can largely move freely on the same horizontal route. This then regularly results in overlapping sections. And in the end, this is exactly what enables enormous freedom in the logistics processes.

More energy efficiency without energy chains

"Such processes would not be so easy with energy supply chains," explains Klaus Just. The group leader for system planning at SEW-Eurodrive refers to the higher masses that are constantly to be moved in systems with energy supply chains. Energy supply chains create noise, wear out, increase inertia and have an overall negative impact on dynamics and also on energy efficiency as a result of the friction.

Another advantage of the new solution: there are no more restrictions with regard to installation space, no cable breaks or limited number of cycles as a result of the energy chain and the moving cables. This smart design was made possible for EMAG with SEW by the Movitrans inductive power transmission and the decentralized TES supply module. Depending on the version, these modules deliver transmission powers between 3 and 8 kW.

Retain regenerative energy from portal robots in the process

The exciting thing about this logistics solution: the robot consumes less than 500 W over the transmitter head over the entire load cycle, even though the horizontal axis alone requires more than 3 kW of acceleration power when accelerating. The short-term energy requirement is fed by the DPS memory from SEW-Eurodrive, a double-layer capacitor package that takes over the primary power supply for the robots with 100 VDC intermediate circuit voltage.

The typical driving profiles of a gantry robot with changing acceleration and deceleration phases led the developers to consider that the regenerative energy generated during braking should not be dissipated via resistors, but kept in the process. The energy storage DPS absorbs this braking energy and also acts as a booster when the portal drives accelerate at 6 m / s².

The structure works so effectively that only the mechanical efficiency losses in the energy network can be compensated for with Movitrans, in total around 500 W. "In contrast to the well-known DC link network of multi-axis applications in the central control cabinet, we enable each unit to work for itself to save the energy. That makes it very easy to scale such a system,”explains Klaus Just.

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Control up to four robots wirelessly

The contactless energy transmission with the omission of limiting cables continues within the robot portal for communication. A data light barrier for EtherCAT is used. It transmits the interpolated position - target values in 1 ms increments from the central SEW control to the four servo drives in the accompanying SEW housing box.

A Movi-C controller calculates the complex robot motion control - for up to four robots at the same time. Part of the motion control are calculations to avoid collisions as well as the coordination of the robot network with a view to a productive whole.

If a machine within a production network requires twice the material flow rate, a robot can be flexibly removed from another area in the portal system. However, if handling units are supplied via an energy chain, they are bound to their area. "We take machine areas off the chain, make the associated resources flexible and plants as a whole more flexible and productive for the future," says Klaus Just in a nutshell. Correspondingly high demands are placed on communication.

Supplementary information on the EMAG Group From machine tools to system suppliers

The EMAG Group is one of the most important manufacturers of manufacturing systems for components from the areas of transmission, engine and chassis component production worldwide. By accessing a very wide range of technologies (turning, drilling, milling, gear cutting, grinding, laser welding, inductive hardening, ECM deburring, PECM machining, automation), EMAG realizes the entire process chain. "The market demands system solutions," explains Ronald Matzig, Key Account Manager for SEW-Eurodrive at EMAG. "The requirements to which we have to respond at EMAG are extremely different. We therefore started to develop our own automation solutions years ago in order to be able to react as flexibly as possible to customer requirements. However, because we are primarily a manufacturer of machine tools, we decidedto look for a partner for the further development of this automation technology, who supports us above all in the subjects of electrical and control technology.

Real-time optical communication

In the portal, SEW-Eurodrive uses the real-time Ethernet protocol EtherCAT - also without a cable, by means of an optical connection to the mobile units. The drive data are cascadably transferred to the robots via a data light barrier. "We therefore dispense with a separate control in each robot," explains Klaus Just. With a cycle time of 1 ms, the optical system has practically no latency when transferring the interpolated position target values to the controller and when reporting the corresponding one Actual values.

Communication for functional safety technology takes place in the same way. In this application, SEW-Eurodrive used a central safety controller for all robots and the entire machine. This communicates directly with the Movi-C automation controller via EtherCAT and uses the EtherCAT safety protocol FSoE (Fail Safe over EtherCAT). This structure enables simple data exchange between the two controls, simplifies program creation significantly and, with its information density, offers very good framework conditions for diagnosis and debugging.

The seamless integration of the FSoE Safety Master or the EtherCAT data light barrier into the automation world of SEW-Eurodrive signals which path the Bruchsal company is taking when they speak of Maxolution machine automation. Standardized interfaces play a major role here, as do prepared software modules or application-specific function modules.

* Marco Wolff, Sales Machine Automation; Heiko Füller, Head of Market Management, both SEW-Eurodrive, Bruchsal