Simulate machines with nominal data, tolerances, wear and faults

7th February 2019
Alex Lynn

Specialist in virtual prototyping software and services, ESI Group, has released SimulationX 4.0, the new version of its software platform for dynamic system simulation. SimulationX has proven itself for many years in industrial companies and research institutions for technical concept studies, optimisation tasks and virtual system tests. 

Starting with version 4.0, manufacturing tolerances, ageing, wear and faults can be systematically integrated into system models. The newly designed user interface allows for efficient workflows and a quick access to the world of system simulation. New model libraries including those for modelling Bowden cables and spatial vehicle dynamics make it easier for companies to reduce the number of physical prototypes through time- and cost-saving simulations.

Typically, system simulation is based on nominal data (as designed). However, the behaviour of the actual machine deviates from the nominal behaviour to a certain extent, e.g. due to manufacturing tolerances of the individual components. In addition, ageing and wear continuously change the behaviour over its lifespan. 

Defects or malfunctions of individual components can also have a significant influence on the machine or system. Whether and to what extent such deviations affect the behaviour of the entire machine depends not only on the specific component, but also significantly on the system architecture and the interaction of all components with each other. The new ‘System Reliability Analysis’ module provides a user-friendly solution for a systematic and semi-automatic integration of both discrete and time-continuous faults in SimulationX models. This allows for analysing the effects of such faults efficiently and reliably for different scenarios and for any period of time.

The behaviour of a vehicle’s powertrain, brakes, suspension and control systems (ABS, ESP) is influenced by the vehicle’s spatial dynamics. In order to avoid costly revisions and delays in time-to-market, these systems must be tested under realistic conditions even before the vehicle is available as a prototype. 

SimulationX has has many years in the development and virtual testing of such systems and now also includes a library of multi-body vehicle models, driving manoeuvres and driver behaviour. This allows for the virtual representation of spatial vehicle dynamics (translatory/rotatory motion and acceleration) and for the efficient evaluation of their impact on the 1D models of the vehicle systems. These models are real-time capable and are designed to accurately represent the vehicle behaviour with a minimum of input parameters.

The assumption that Bowden cables are simple machine elements and have little to do with high-tech is misguided. These cable systems are indeed complex components and are used for applications that require maximum precision. Endoscopes or robots for endo-surgery, for instance, require high-precision movements with precisely defined forces transmitted via such a cable. Also in cars, complex Bowden cable systems must meet the highest standards.

However, mastering those cable systems reliably and under changing boundary conditions used to be a task that could only be solved with great efforts. Bowden cables change their shape and position when forces are transmitted through them. When they collide with surrounding parts, they can cause damage and undesired noises. Furthermore, the friction behaviour between cable and housing, which varies with many factors, leads to unwanted effects when forces and motions are transmitted. Especially with precise movements as required in medical technology or for closing mechanisms, these non-linearities of the backlash hysteresis pose a great challenge to engineers, especially in the development of the corresponding control systems. 

So far, such investigations could only be performed in a virtual environment through very time-consuming and CPU-intensive finite element methods. With the new module "Bowden Cables" in SimulationX 4.0, such analyses and development tasks require significantly less time and can be realised with standard desktop computers.

The simulation is not limited to the mere Bowden cable, but includes the boundary conditions, the drives and outputs as well as the control system.

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