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Testing Without a Prototype – the HiL Test Rig

HiL simulators for automated software testing | by Anne Naumann

How many hours of prototype testing did you invest in the development of your latest machine? And how much do you think it cost? Palfinger Platforms, ESI ITI and Hydrive Engineering have identified great savings potential here. The partners have been working in collaboration to develop solutions for a more sophisticated development process. At the same time the three key aspects of machine development were taken into consideration. Efficient testing with HiL test rigs is the key to optimisation. For the development of a mobile access platform at Palfinger Platforms the partners set up one such HiL test rig.

HiL-Prüfstand an Hubarbeitsbühnen
©HYDRIVE ENGINEERING GMBH

Functioning and safety as drivers for development

We are all familiar with the inherent conflict in wanting to develop a machine which offers even more functionalities in record time. At the same time prices shall remain affordable and competitive on an international scale.

And just like the legislator and trade association insurances, we are all aware that using a machine always bears a potential risk. That is why we want to take both effective and efficient measures to minimise the risk of any damage to property or persons. In Europe and Turkey, safety is regulated through Directive 2006/42/EC, better known as the Machinery Directive.

Functional diversity, competitiveness and safety place complex demands on any machine development. It therefore comes as no surprise that development expenses are extremely high.

The three key aspects of machine development

For this reason, we need innovative methods to make machine development rational while still meeting all of the above requirements. A good starting point to solving this problem is to examine what exactly makes development so expensive.

Based on the project management triangle, we have identified the three key aspects of machine development:

  • Duration of development, considering the fact that time is money
  • Number of prototypes and tests, and the resultant tying up of capital
  • Personnel costs – in mechanical engineering companies in Germany in 2009, personnel costs amounted to 25.6% of the total output.

The ongoing trend towards even more complex machine controls, particularly with mobile machines, calls for powerful and efficient test processes in order to ensure both the quality and reliability of control systems. ESI ITI, Palfinger Platforms and Hydrive are aware of the fact that this involves dedicating a large portion of machine development to testing such functions. This is why the project partners have set themselves the objective of improving the test phase of control development for a mobile access platform. This means taking a threefold approach which encompasses the three key aspects of machine development.

Setting up a HiL test rig

The principle of the HiL test rig is very simple: bespoke control software and a bespoke electronic control unit are connected to a simulation model of the machine together with certain machine components. The model then simulates the sensors, the motion behaviour of the machine and other functionalities. This enables to analyse the software’s response in typical operational situations, as well as in critical ones.

In the case of the mobile access platform, the HiL test rig consists of the following components:

  • Machine model of the access platform developed using SimulationX® software
  • Real electronic control unit with control software
  • The control board used at Palfinger Platforms (HMI, for short)
  • ECU-Test® test management software

Any effects on the machine behaviour resulting from changes to the control software one can now immediately observe on the test rig. This means that developers can test machine functions at a very early stage of overall machine development – long before the first prototype exists.

Eliminating cost drivers

With reference to the three key aspects of machine development, the use of an HIL test rig has the following effects:

Prototypes

The number of necessary prototypes to test the access platform’s control system decreases significantly. This has a direct effect on the capital employed. In addition, there are indirect cost savings for storage, maintenance and prototype coordination (overhead).

Personnel expenses

A significant proportion of this overhead consists of personnel costs, which will automatically drop when fewer prototypes are used.

The development process also requires extensive coordination efforts. This ensures the flow of information between engineers testing prototypes and developing the control system. Here too, there is potential for reducing costs if the collaborating departments are able to integrate the HIL test rig into test management, thus simplifying cross-departmental communication.

Duration of development

While the software development department carries out tests on the HiL test rig, other work on the prototype can be performed at the same time. Development can use the test rig in the laboratory at any time, irrespective of the weather conditions. This reduces weather-dependent delays in development.

Conclusion

The advantages of functional testing on the HiL test rig are clear. It forms the ideal basis for the efficient development of machines, thanks to the considerable savings potential for machine development.

Hydrive is happy to answer any questions you might have on this topic.