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Support from further afield01 September 2006A requirement in the competitive environment in machine building today is remote maintenance, which is able to support commissioning and operating personnel during most phases of the product life-cycle. Remote maintenance is a component of L-Force, Lenze’s new generation of drive and automation technologyThere are three typical cases where remote maintenance gives cost advantages: commissioning, data acquisition and servicing. For example, if a commissioning engineer is a long way from his or her offices and requires support from experts at head office, remote maintenance allows savings in time and cost, as the engineer does not have to travel to work on the problem.
Quality assurance often requires the acquisition of data on line, followed by processing and evaluation. The system used to perform these functions can be automated using a remote access, thus ensuring continuous quality control.
If a machine breaks down, help is needed quickly. If the error cannot be located immediately due to lack of skilled personnel locally, then service engineers with the requisite skills have to make the journey to site, thus extending down times still further. However, problems can sometimes be remedied using software. It might simply be a case of acknowledging a message or modifying a parameter. In such cases remote maintenance eliminates the need to travel to site. Even if the error cannot be corrected using software, service engineers can still pinpoint the nature of the fault, agree remedial strategies with colleagues and
obtain any necessary spare parts remotely. Although service resources still need to be deployed, the process can be carried out much more efficiently, thus reducing costs.
The three application examples above show how important remote maintenance is today. Selection of the software and hardware components for remote maintenance depends to a large extent on the particular application environment. Decisive factors are the extent to which integration with existing systems is required, and whether any existing remote connections can also be used. A classic remote maintenance solution is a dial-up connection. Such direct-switched connections are a simple form of remote maintenance. In such cases it is sufficient to make an analogue telephone line available at the plant. The technical installation is clear and simple. It is also relatively easy to protect access by using password mechanisms or call back. Such designs are individual solutions that can only be used in conjunction with specific components. This can lead to the use of different modems, each with a separate telephone line, being required for the remote maintenance of devices supplied by different manufacturers. To some extent these disadvantages can be balanced out by connecting the individual components that are to be maintained remotely to a higher level system, for example via Ethernet. However, this raises questions concerning integration into IT systems and such solutions have to be agreed with IT departments, not set up by an engineer working in isolation. For this reason simple dial-up connections are still a common solution.
Lenze offers the ModemCAN communication module for classic switched connections. This is a CANopen device for DIN rail mounting with an integrated analogue modem configurable for all relevant countries worldwide. For “exotic” telephone standards or others such as ISDN or GSM, modems can be connected to the Lenze ModemCAN via RS232. Password protection and callback ensures that access is secure. Buffering large data packages brings in the risk that data transfer may be incomplete if a connection is
interrupted, thus leaving the device in undefined state. The ModemCAN is designed to only forward the data via the CANbus once it has all been received.
This solution is beneficial for applications with a small number of nodes. The limits of the architecture become apparent when it is used to maintain larger plant remotely, because the expenditure involved in providing individual machine components, or even individual machines with a separate telephone line, cannot be justified. A comprehensive solution that allows as many components as possible to be maintained remotely via a uniform access path must be found for such applications. This can be achieved by initially implementing access via Ethernet for all devices to be remotely maintained. Various standard
solutions exist for remote access to Ethernet networks. The appropriate solution can be selected in accordance with requirements in respect of security, availability and various transmission media. Standard Ethernet also provides the basis for the use of low cost standard components for remote maintenance.
Many modern devices, including the new Lenze L-force servo drives from the 9400 range, already feature onboard Ethernet interfaces. If these do not exist, fieldbus converters can be used to establish the connection to Ethernet. Lenze offers the EthernetCAN communication model for this purpose. This is a CANopen device, which facilitates access to other such CANopen devices via Ethernet. These varied applications include networking in large plants. It allows CANbus lines to be short and confined within the control cabinet. Ethernet, for which line length is not critical, is then used to make the connection to higher level systems. This also provides a means of physically isolating a number of CAN lines, yet still enables all
devices to be accessed simultaneously from a single connected PC.
Another application for this device is remote maintenance via the Internet. If a secure connection exists, for example a VPN (Virtual Private Network), every CANopen node can be reached in this way with aid of EthernetCAN. The same is true if router technologies, for example ISDN routers, are used.
In order to make use of these advantages of Ethernet, machine elements must be equipped with an Ethernet interface or special gateways must be used (either separate devices or controls which have an Ethernet connection). PC based systems are an alternative to this. A PC transfers the conversion of a fieldbus protocol to an Ethernet capable software interface. The OPC specification (OLE for Process Control) has developed into an industry standard in this regard. As soon as an industrial PC with an appropriate fieldbus card is available in a plant, the PC can be used as the Ethernet gateway based on an OPC server.
Lenze can offer its DriveServer concept, a multi-stage system of OPC servers defined by DRIVECOM, for such applications. The bus servers contain the appropriate fieldbus protocol and the higher level Drive Server contains the device functionality. Due to the DCOM technology on which OPC is based, OPC servers and OPC clients can be located on various PC’s. The PC’s are then linked via local area network or a remote access connection. DCOM and the associated Windows mechanisms also cover the question of access protection.
Lenze have built facilities for remote maintenance into the L-force 9400 drive series. The current status of the drive can be determined at any time and from any location. Status variables and even application programmes can be changed remotely by simple telephone connections or Ethernet networks. An Ethernet module is available for the 9400 drives alongside the communication modules mentioned above. This Ethernet module is plugged into a slot in the servo drive. It is thus possible to access the drive controller directly via Ethernet NRT (Non -Real Time). Contact Details and Archive...Related Articles...Most Viewed Articles... |
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