Developing the All-in-One Test System, a New Integration Concept in Test Benches for a Smart Metering Production Line

Walid Lachiheb, SAGEMCOM TUNISIA

"We chose LabVIEW as the development environment so we could benefit from our knowledge and experience with NI tools and the skills acquired by our qualified engineering team through participation in NI training courses and certification. "

- Walid Lachiheb, SAGEMCOM TUNISIA

The Challenge:

Developing multidevice functional and calibration test benches for a new smart electricity meter production line that conforms to machinery directive 2006/42/CE and reducing the occupied implementation space for all the test benches.

The Solution:

Designing and realizing a rotary table machine to replace six separate test benches using the CompactRIO platform to perform vision inspection, functional test, metrological calibration, laser marking, ultrasonic welding, and quality control.

Author(s):

Walid Lachiheb - SAGEMCOM TUNISIA
Seifallah Lejri - SAGEMCOM TUNISIA

 

Project Overview

Sagemcom Tunisia is a subdivision of Sagemcom, a French communications company and European leader specializing in electronic manufacturing. Our test department designs and develops turnkey test systems for metering and energy activities. Director Mr. Walid Lachiheb and Mr. Seifallah Lejri, Test Development Manager, lead this department.

 

When opening a new factory in France for smart metering production, we faced the following challenges:

  • Developing a multiproduct testing line for both operator handled and fully robotized use
  • Ensuring high reliability of the machines for a fully robotized production line with little to no human intervention
  • Adhering to European Union machinery directive 2006/42/CE
  • Ensuring fast and easy setup time, including plug and play smart fixtures
  • Reducing line occupancy to increase profitability and reduce COGS

 

The biggest challenge for our design team in Tunisia was developing a solution that meets the above criteria and guaranteeing the highest reliability and robustness of our solution in a fully robotized plant located in France

 

Metering Integration Line Process

 

A classic integration line includes the following standalone machines:

  • Vision inspection test for meter’s LCD screen
  • Functional test
  • Calibration and verification of meters with reference to a Class 0.04 standard meter, which is the key point of Sagemcom knowledge and requires a lot of arithmetic and synchronized parallel operations
  • Laser marking machine
  • Ultrasonic welding machine
  • Quality control bench or poka yoke tester

 

All-in-One Machine Concept History and Challenges

After contemplating the benchmarks to meet all the required criteria, we thought, “What about integrating all the test benches in a single, special machine?”

 

The concept of the all-in-one machine consisted of a single machine with eight testing positions in a rotary table, with each position replacing a classical test bench and performing a specific test or operation.

 

The most important technical challenge was finding a way to overcome the complexity of the project and ensuring a complete synchronized and parallel job in each position. Taking into consideration the existing EMC perturbation, calibration was particularly tricky. Four of the eight positions are dedicated to calibration and this process requires current levels to reach 60 A.

 

All-in-One Machine Requirements

After analyzing the available solutions in the market for machine control, we decided to work on our own concept due to the high reliability expectations we had. We dismissed all Windows OS-based platforms due to their inability to manage parallel operations and their common crashing issues.

 

We thought of using a well-known platform for our team, Festo PLC’s, but those PLCs are limited when it comes to complex floating point operations during the calibration phase.

 

We also needed to ensure safe communication between the control unit and all the instruments/actuators in the machine, which had to be in compliance with machinery directive 2006/42/CE. Thus, we decided to implement Ethernet/IP protocol to control all moving part systems and laser marking. For interfacing with an external ABB IRB2600 robot, we chose to adopt DeviceNet protocol.

 

The machine was designed to run many products, so we used an additional XYZ electrical table based on IndraDrive controllers from BOSCH Rexroth to adapt our testing tools with the product. Therefore, the system became more complex, reaching 244 I/O control signals

 

 

Conclusion

We needed a real-time based control system to ensure the reliability of the machine and run the eight positions in true parallel. It needed to support industrial communication protocols and be easily programmable and flexible to manage several deported I/O signals.

 

Hardware and Software Architecture

We chose LabVIEW as the development environment so we could benefit from our knowledge and experience with NI tools and the skills acquired by our qualified engineering team through participation in NI training courses and certification.

 

The state machine architecture suited our needs and LabVIEW could handle multithreading, which was a key differentiator in reducing development time and avoiding multithreading programming challenges we had faced in the past with text-based programming languages like LabWindows™/CVI software.

 

We needed true parallel operations and synchronization for this automatic standalone machine, which led us to the CompactRIO platform. We also used the LabVIEW Real-Time Module and the LabVIEW FPGA Module.

 

We used the cRIO-9066 controller because of its powerful dual-core ARM Cortex-A9 processor and Artix-7 FPGA. It is a cost effective solution that empowered us to control all 244 I/O signals through a deported NI 9146 chassis, which helped us reduce wiring and facilitated the reach to limited access areas within the machine.

 

This choice helped us to implement industrial communication protocol DeviceNet and Ethernet/IP through its support of the NI 9882 module and NI-Industrial Communications for EtherNet and DeviceNet drivers libraries.

 

We used a host PC to ensure traceability records in the background and to run the vision inspection test using VBAI.

 

Project Outcome

We overcame a big technical challenge by creating a complete production line within a single machine and ensured stable test time thanks to the real-time operating mode. We reduced space occupancy, offered easier maintenance, and certified a single machine instead of six (CE).

 

We also reduced the planned number of robots to be used as we designed a single machine, which also reduced handling time for the DUT

 

Reducing the number of the machines also impacted global power consumption. This is in accordance with the objective of the smart metering program, which is to reduce energy consumption and harmful environmental impacts. We were able to produce smart meters efficiently by reducing power consumption in our plant too.

 

As an extra optimization and in order to lower implementation cost and increase accuracy, we selected electrical actuators, reducing the need of pneumatic installation within the plant and saving installation cost. This choice helped us with the multiproduct compatibility issue: when plugging a fixture, we scan its serial number and automatically configure the tooling in an accurate position through the LabVIEW code controlling the XYZ axes and launch the respective test sequence.

 

Conclusion and Future Outlook:

After successfully designing and developing our standalone machine running in full LabVIEW Real-Time mode, we plan to spread out the use of the FPGA mode and integrate all complex floating point operations within the FPGA. An important planned optimization is to migrate the vision inspection from the desktop to the cRIO.

 

In conclusion, this project provided a considerable return on investment and offered a new test bench platform architecture so we could adopt CompactRIO as a standard for test bench development.

 

Author Information:

Walid Lachiheb
SAGEMCOM TUNISIA
Tunisia
Tel: +216 50 543 528
Lachiheb.walid@sagemcom.com

Figure 1. Classical Integration Line Process Flow
Figure 2. Classical Metering Integration Line in Sagemcom
Figure 3. A look inside the machine
Figure 4. Hardware Architecture of the Machine, Part 1
Figure 5. Hardware Architecture of the Machine, Part 2 (Calibration)
Figure 6. Comparison of Space Occupancy Between Classical Integration Line and the New Machine Concept
Figure 7. Front of the Developed Machine
Figure 8. Benefits of the Machine