Drives smarten themselves up
Mike Lomax examines the role of intelligent drive systems in optimising machine configuration and performance and aiding the adoption of Industry 4.0.
Machine manufacturers are under pressure to provide shorter development times for highly advanced machines, with less manpower available to them. This is especially so as the drive towards Industry 4.0 adoption gathers pace. The requirement for real time data to inform operational decision-making is growing. The keyword with Industry 4.0 is connectivity - between all participants in the production process, whether human or mechanical - even in facilities where Industry 4.0 adoption may still be some time in the future, it is important that any components or systems are at least compatible with the requirements of Industry 4.0 – and have the ability to connect to and communicate with internal and external networks.
While this is relatively easy to achieve with new components, replacing all systems to ensure compatibility is an unrealistic option and this had led to the development of a variety of devices which enable standard components to offer at least basic connectivity to Industry 4.0 systems, without impacting on the automation logic.
Enhanced functionality is a particular requirement with drives. Modern drive systems now have sufficient intelligence to perform position movements and velocity control. These functions are now regarded in the same way as accessing email via a mobile phone – almost a minimum expectation. A further expectation with Industry 4.0 is that drive systems are able to acquire data on machine functionality and performance, to then configure and present this data externally.
Thanks to advances in drives, manufacturers can now allocate functions directly to the drive, via in-built technologies that eradicate the need for an external PLC. The latest servo drives, for example, now include the IEC61131-3 PLC operating system which represents a step change from the minimal functionality offered by previous generations of drives.
The implications of this new capability can take time to fully understand, but essentially the drive now has the ability to solve control challenges in real time, whenever and wherever they may occur – a key facet of Industry 4.0. Furthermore removing the PLC and going direct to the drive eradicates any time lapse, and so optimises cycle time and production consistency.
Staying in sync
However, even if a drive system does contain the appropriate problem-solving tools or function blocks, the challenge of synchronising multiple movements on the machine remains. Where the bus system in use is not deterministic, the solution is for the drives to communicate between themselves, without having to refer back to a central control system. This is where technologies such as SERCOSIII – one of the first deterministic bus systems, which can now be installed directly into the drive - come into their own. However, a deterministic system is not necessarily a prerequisite for Industry 4.0 adoption as drives can store real time data and send it in a non-deterministic way to upward systems.
With such a range of function tools available within the drive, it is important that selecting the right tool for the job is as straightforward as possible. The goal should be that a machine builder programmer, with perhaps no previous experience of the particular challenge in front of him, is able to easily access and use these functions.
The solution lies in the employment of tried and tested PLC function blocks which can be used freely in IEC 61131-3 PLCs and can even be incorporated within conventional ladder logic programming.
A variety of function blocks are now available and can be selected depending on the individual application requirements. Their capabilities range from correcting the positions of products on conveyor belts, and the control of winders, to closed loop register control and even the creation of a complete motion profile for cross-cutters and cross sealers.
Creating a machine HMI
Creating an interface between the machine and operator – another vital component of Industry 4.0 – has previously required central PLC involvement along with a bus system, to convey key machine set-up information and variables to the drives. Diagnostics and machine status information is then redirected to the PLC before being displayed on the HMI.
Although modern bus systems can achieve this, it can require a great deal of programming effort when all the required information is already contained within the drive system. To address this, many drive systems now also contain all of the tools needed to create a HMI. In some instances, a central PLC may not even be required as the drives are capable of using a full range of inputs and outputs which would normally be connected to the PLC.
A key factor which must be kept under control is the time taken to set up and commission the machine. Intelligent drives now offer a number of tools that can reduce start-up time through the optimisation of the axis movements and process synchronisation.
These rapid start-up tools have been designed to enable the drives to be moved at an early stage of the machine commissioning, even before the machine control software is installed on the system. This results in rapid and easy testing of machine mechanics with only basic IT tools, such as mobile phones or tablets, required to gather information.
Help with maintenance?
Modern drives can now even play a part in a proactive maintenance regime as they can be supplied with a fully integrated series of software tools capable of performing key predictive maintenance functions, with minimal additional programming effort. This software can be set up to continuously monitor in real time the condition of the machine mechanics and process conditions – from waveform analysis through the analysing the rate of temperature change, as well as checking for backlash, increased friction or process overload. If a fault condition arises, a code is generated and passed to the machine HMI. Furthermore, if a critical issue is identified which required the machine to cease operating immediately, this decision can be made inside the drive, minimising lost production and the risk of machine damage resulting from unsafe operation.
Whether or not Industry 4.0 is the immediate goal, what is undeniable is the enhanced processing power and functionality of intelligent drives which present numerous opportunities to optimise programming, production and maintenance. With the need for central PLC’s now eliminated in many instances, not only is component count reduced but more advanced machines can now be created in much shorter timeframes.
Mike Loma is electrification manager at Bosch Rexroth.>
Source: Control Engineering Europe - All Articles