Beckhoff’s eXtended Transport System (XTS) has found its way into numerous new machines. It has supported the development of innovative automation concepts in a diversity of forms, from simple to highly complex. The possibilities are illustrated by a multi-XTS application which was shown by SAP at Hannover Messe as an example of a smart factory production line.
The 4 x 6 metre multi-XTS demo is used for transporting and sorting different beverage cans. It consists of five XTS systems with a total track length of 26 m and 100 movers. There are 72 movers alone running on the inside of the 17 m long outer XTS. In addition there are two 4 m long elevated systems, each with up to 12 movers running on the outside, as well as two lifting stations, each consisting of two vertical 25 cm XTS modules. Each of the lifting modules has one of the new 70 mm movers for increased payload.
Complex motion control through simple software configuration
In this complex system, the high flexibility of the software-based motion control functionality is evident. Each mover is a self-contained servo axis, and can be controlled individually or even synchronised to other movers or process sequences as required. As a property of each mover, the dynamics can be changed individually at any time and on the fly according to requirements. This means that a mover can transport a smaller white beverage can faster than the larger red cans and will move even more dynamically with no can at all.
Several processing and accumulation stations have been implemented. For example, the cans are transferred to the two elevated XTS systems by a lifting device comprised of two movers connected by a mechanism consisting of a gear wheel and toothed rack. For the lifting movement, the arriving mover in the lower system and the first of the two coupled movers in the upper system must be synchronised with each other. Subsequently the second upper mover moves relative to the first in order to pick up the can from the lower mover via the gear wheel mechanism.
The synchronisation of two cam plates ensures that no additional lifting movement of the two coupled movers is generated when driving through curves, so the can is transported without jerks. The relative distance between the movers will always remain constant, even when driving into and out of the curve. Through control software parameterisation, it is possible to switch between the two corresponding cam plates, allowing the complex lifting function to be implemented in a simple and extremely flexible way. Preconfigured function blocks simplify the implementation. TwinCAT software provides ideal support for the simple implementation of any desired movement.
The individual movers can be mapped as conventional servo axes with all common motion control functions such as flying saw, electronic gearbox and cam plate. Specific XTS requirements, such as automatic accumulation, collision avoidance, jerk avoidance and centrifugal force limitation, can be realised with functional extensions in TwinCAT. In addition, complex kinematics involving two or more movers are already integrated within the XTS motion control toolbox, with which users can define, for example, a group of several movers as a 2D axis (X/Y table) or a 3D axis. Furthermore, integrated condition monitoring enables online monitoring of the movers during operation.
The preconfigured function blocks facilitate a station-oriented implementation of the transport and handling tasks. For instance, the cans must be accumulated before entering more time-consuming processing stations such as the lifting stations. A waiting station uses the collision avoidance provided by TwinCAT so that all movers automatically accumulate behind the mover in first place. If the first mover drives onwards, the second-placed mover simply takes its place. Synchronous movements can also be realised with similar ease.
This many-core technology provides significantly higher computing power for the integration of additional functions into the multi-XTS application. A prime example of this is computationally intensive condition monitoring functionality, which allows the very early detection of wear in a mover roller or soiling of the guide rails. For this purpose the computer platform must acquire a huge amount of data and continuously analyse it to detect certain threshold values or vibration frequencies. The immense computing power of the C6670 is required in order to be able to realise this.
For more information contact Kenneth McPherson, Beckhoff Automation, +27 (0)11 795 2898, [email protected], www.beckhoff.co.za
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