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Concurrent Engineering Approaches for SustainableProduct Development in a Multi-Disciplinary Environment,DOI: 10.1007/978-1-4471-4426-7_78, � Springer-Verlag London 2013

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Application of Reverse Engineering Techniques in Vehicle Modifications

Zoran Lulić, Rudolf Tomić, Petar Ilinčić, Goran Šagi, Ivan Mahalec 1

Abstract: In this article the measurement and generation of 3D models of various vehicles, on which significant design changes had to be made, is described. In or-der to make the required design changes on the original vehicle, a 3D model of the vehicle had to be created. Therefore, the original vehicle had to be measured in order to create the CAD model of the vehicle. The surface of such complex ob-jects and specific points on the object can be digitized using various optical meas-uring systems. Based on gathered digital measuring data and via specialized soft-ware packages, 3D CAD models of the vehicle or models of specific part of the vehicle can be created. The obtained models represent a good basis for design in-terventions and various analyses and simulation tasks required for making good decisions regarding the design changes on the vehicle. For those purposes, two measuring systems were used: TRITOP and ATOS. The ATOS system was also used to digitize serial production cars in order to modify them or to use their parts in new products. The use of such measuring system and 3D modelling and analy-sis tool is allowing the engineers to find better design solutions.

Keywords: optical measuring system, reverse engineering, CAD modelling, FEM analysis

1 I. Mahalec () University of Zagreb, Faculty of Mechanical Engineering and Naval Architecture, Ivana Lučića 5, 10000 Zagreb, Croatia e-mail: [email protected]

J. Stjepandic et al. (eds.),

1. Introduction

The article describes modifications of various vehicles with a focus on the measurement of the vehicle and its rebuild as a 3D CAD model. This is necessary in many cases if the production cars should be customized for special purposes. The measurement method and the rebuild method are described on various exam-ples: alteration of a city bus into a panoramic bus for city sightseeing, moderniza-tion of an old tram, fitting of already existing parts (side doors) on to a newly de-veloped race car body and the development of a new rear door opening mechanism for an existing production car. In all cases a measurement of the vehi-cle or a part of the vehicle had to be performed. The city bus space frame body is a complex structure and in order to rebuild it in a 3D CAD tool, the best way is to determine the positions of structure joints. Therefore the measurement was per-formed with the TRITOP optical measurement system which measures the posi-tion of specific markers placed on the measured object. The TRITOP system was also used during measurements of an old tram that had to by modernised. Another example of the use of optical measuring methods is shown in the development of a race car for the Dakar rally. In order to cut development and production costs, the doors and the door opening frames of a suitable serial production car were used. To implement those parts to newly designed vehicle structure, CAD models of the door and the door frame have to be created. Conventional measuring methods hardly allow digitalization of such complex geometries. Transfer of the door and the door opening frame from real to virtual world was made by three-dimensional scanning, using the ATOS optical measuring system. The same system was used in the case of the Fiat Punto, in order to adapt it for person with disabilities. For this purpose the new rear door opening mechanism was to develop, allowing translatory movement of the door and enabling better accessibility of compartment behind the driver’s seat. To develop such a mechanism, 3D models of the rear door and the rear door frame were necessary. They were created on the basis of 3D scans, performed with the ATOS measurement system.

2. Optical Measuring Systems

In all adaptation and design cases described in this paper TRITOP and ATOS optical measuring systems where used (GOM mbH, Germany). TRITOP and ATOS enable fast, easy and accurate recording of different forms of objects, re-gardless of their material, size and complexity. Systems are portable and robust, so measurements are not limited to laboratories, but can easily be implemented on the field. Detailed forms of objects remain stored in the computer, which with ad-vanced software features provides a number of different application areas.

922 Z. Lulić, R. Tomić, P. Ilinčić, G. Šagi, I. Mahalec

TRITOP Measuring System

TRITOP is a mobile industrial optical measuring system that determines the 3D position of markers and other visible elements which can be placed on the meas-ured object. The TRITOP system provides a non contact measurement of high re-liability with the possibility of three-dimensional measurement of geometric ele-ments such as bores, edges, cylinders, cones and spheres. The system consists of a photogrammetric camera, a set of coded and unencoded points, a set of scale bars and a high performance PC with the TRITOP software for the calculation of the positions of point’s photographed with the camera (Figure 1).

Figure 1: TRITOP measuring system

The position of a point in the 3D space can be determined by triangulating mul-tiple bundles of observation rays. If the spatial orientation of each bundle is known in the object coordinate system, the intersection of the rays delivers the desired 3D point coordinates. All relevant object points are marked and, using a photogram-metric camera, images of the measured object are recorded from various angles of view. Then the TRITOP software calculates the 3D coordinates of the adhesive markers and object characteristics from these digital images.

ATOS Measuring System

The ATOS measuring system is based on optical triangulation and stereo-viewing thus allowing accurate measurement and capture of the shape and size of the visible surface of almost any three dimensional object. The main parts of the ATOS measurement system are the sensor head with two cameras, the high per-formance PC and the dedicated application software.

The sensor unit projects different fringe patterns (parallel lines) onto the object to be measured which is then recorded simultaneously by the two measurement cameras from different angles. From each single measurement, typically calibrated to area of 400 by 350 mm, by using digital image processing, the software gener-ates up to 4 million object data points. In order to digitize a complex object com-pletely, several individual measurements are required from different viewing an-gles. Based on the reference points in form of circular markers, ATOS transforms

Application of Reverse Engineering Techniques in Vehicle Modifications 923

these individual measurements fully automatically into a common measurement of a complete object in global coordinate system. The reference points can be applied to the object directly or by means of measuring plate or a fixture. Depending on the measuring object size, few measuring techniques can be used. For example, when measuring object that fits into the ATOS measuring volume, only scanning without photogrammetric TRITOP measurement of the object can be used. The number of necessary individual measurements is relatively small (Figure 2, right).

Figure 2: ATOS measuring techniques

If the measured object is slightly larger than the scanning volume, the object can be digitized by dividing it into several measuring volume sections. On the other hand, when the measuring objects is many times larger than the scanning volume, a combination of the photogrammetric TRITOP measurement and the ATOS optical scanning is needed.

3. Modifications of City Buses

In order to convert a city bus into a panoramic bus the roof of the bus had to be removed (Figure 4). The removal of the bus roof construction causes significant decreasement in the bus body structure stiffness. In order to restore the stiffness of the vehicle’s body the structure has to be significantly modified. Additionally, in order to protect the passengers in the event of a bus rollover, installation of roll bars at the front and rear of vehicle is necessary.

Figure 3: Damaged city bus that has to be converted to panoramic bus


Figure 4: Modified city buses

To make good decisions regarding the modification of the bus body structure, various cases of yield stress and stiffness calculations of various variants of the bus body structure modifications had to be performed. To perform such calcula-tions various FEM analysis tool can be used. In order to calculate a structure with a FEM analysis tool, a CAD model of the structure is needed. To model the origi-nal bus body structure technical documentation of the bus is needed or the bus has to be measured. In the case that the technical documentation of the original city bus is not available, the bus body structure has to be measured. The described process is graphically shown on Figure 5.

Figure 5: 3D CAD model generation process


Dimensions and shapes of vehicles body structure were measured by the TRITOP optical measurement system. The measured data was processed in the TRITOP software application and the cloud of points from witch only a loom form of the bus can be seen (Figure 6) was transformed into a set of points, lines and planes which represent specific attributes of the bus body struc-ture.

Figure 6: Measurement results in TRITOP software

Based on the data imported from the TRITOP software, an accurate wire frame

model of the city bus was created (Figure 7). The wires in the wire frame model represent the centrelines of the square tubes from which the bus frame structure is made.

Figure 7: The wire frame models of the original buses and the FEM calculation model


The wire frame model was the basis for the creation of the model for FEM cal-culations (Figure 7) and the model of the space frame structure of the panoramic bus (Figure 8). As there are no regulations for this bus category, in agreement with Croatian vehicle technical inspection authorities a load case for the modified bus is determined in accordance with similar provisions (laws and regulations on the safety of road motor vehicles). It has been agreed that the roll bars and the remain-ing body structure have to be strong enough to endure static load corresponding to the maximum technically permissible mass of the vehicle. In other words, in case of bus rollover, body structure and roll bars must ensure the stability of structure and “safe space” for passenger survival. According to defined load case, FEM cal-culations of various modification solutions for the bus space frame structure were performed. Final design of the modified bus body structure, shown in Figure 8, was reached through several consecutive FEM analyses. On the other hand, such a load case is unlikely, since in the case of actual rollover dynamic forces occur and therefore loads may be considerably higher. Because of all that, all calculations were made with the safety factor S = 1.5 taken into account. Also a design solu-tion for the vehicles interior and exterior was modelled in accordance with rele-vant laws and regulations.

Figure 8: The space frame and the design solution of the panoramic bus for city sightseeing


4. Modernization of Old Trams

Zagreb Municipal Transit System, which is specialized for passenger transpor-tation in the city of Zagreb, decided to modernize 50 check to modernize 50 trams, model TMK-301 acquired 1987. so that they would be made functional for an-other 10 years. Trams needed to be adjusted to new standards by installing the heating and air conditioning unit on the roof above the driver’s cabin. A voltage converter unit and a new pantohraph were also installed. Total mass of these de-vices was 240kg what was 140kg more than the previously built-in devices. The assignment was to check the influence of the added weight on the strain of the roof construction and on the stability of the vehicle, and to make all the necessary technical drawings and calculations of the changes that were done to the tram.

Original tramTRITOP meausurementresultats in a 3D CAD tool

3D CAD model

Modified tram

Original tramTRITOP meausurementresultats in a 3D CAD tool

3D CAD model

Modified tram

Figure 9: Workflow during the modernization of the KT-4 tram for transportation system

of Zagreb

For that purpose a tram body had to be measured. The measuring was made us-ing the Tritop measurement system. Surfaces and plains obtained through process-ing measured data were imported as IGES file into the 3D CAD system, serving as a basis for the making of the tram model. All changes in the tram construction were first analysed on a CAD model in order to find the optimal solution. After that, the same model was used as the basis for FEM roof construction analysis (Figure 10). Analyses which were carried out have shown that the structural and dynamic stability of the vehicle was not disturbed by the installation of the new


devices onto the roof, as well as that the conditions of use of the modernised tram can remain as they were. The entire process is shown in Figure 9.

Figure 10: The stress analysis for the new load case of the tram's roof

5. Race car for Dakar Rally

One of the tasks in the development of the racing vehicle for the Dakar Team of Croatia was to fit the drivers and co driver’s door from a serial production SUV (Opel Antara) on to the space frame of the developing racing vehicle. The vehicle was developed according to FIA regulation 285-2010. Such a development im-plies vehicle design from sketch and includes development of different parts such as suspension, power train, vehicle body and safety roll cage. When developing the body structure of the vehicle one of the major problems is water and dust proof sealing of passenger compartment doors. Development of completely new doors only for this specific application would be too expensive and too complicated. Be-cause of that, door and door opening frame from a serial production vehicle are used. To insert existing door opening frame to newly designed racing vehicle a CAD models of the door and the door frame have to be created. The door and the door opening frame ware first measured using TRITOP and then scanned with ATOS like shown in figure 11.


Figure 11: The ATOS measurement of the door and the door opening frame

Figure 12: STL files of the door and door opening frame

After the complete digitization of the measured objects, the scan data in form of point clouds were processed by ATOS system and transformed into an editable polygon mesh data set in STL format (Figure 12). Each part individually, door and door frame, was then remodelled using STL format in a 3D CAD package.

After reverse engineering was done, the door model and the door opening frame were used as a base for adjustment and design of whole vehicle body frame (Figure 13). Later, on the space frame of the vehicle, the door and the door open-ing frame were used as a frame for the design of the vehicles body.

Figure 13: The 3D model of the Dakar Team Croatia rally vehicle and its design


6. Rear Door Opening Mechanism

One of the fields of the automotive industry, where reverse engineering meth-ods can be widely used, is the adaptation of serial production vehicles to the needs of persons with disabilities. In this case the idea was to develop a rear door open-ing mechanism which would perform translatory movement of the door so that a person with disabilities could easier put his wile char behind the driver’s seat or pull it out when he wishes to step out of the vehicle. In order to develop such a mechanism, a 3D model of the rear door and the rear door frame are necessary. Those 3D models were created based on the 3D scans performed with the ATOS measurement system. First the door and the door opening frame ware measured using TRITOP and then scanned with ATOS (Figure 14).

Figure 14: Measurement of the rear door and door opening frame

The final measurement result is a mesh or a cloud of points (with even few mil-lion measurement points, if needed) in the form of cross sections, characteristic lines or separate points. By processing the obtained measurement results useful CAD models shown in Figure 14 were created. These models were then used for the development and analysis of a new rear door opening mechanism (Figure 16).

Figure 15: CAD models of the rear doors and rear door opening frame


Figure 16: The new rear door opening mechanism

7. Conclusion and Outlook

To be competitive in today’s vehicle reconstruction and adaptation tasks means to do the work fast and more cost efficient. One of the major parts of such tasks is measurement. Optical measurement systems like TRITOP and ATOS have shown many advantages concerning accuracy and speed of measuring process and they allow fast creation of 3D models of existing objects, thereby allowing the engi-neers to spend more time on finding better design solutions. The result is that the overall development time is shorter and thereby more cost efficient. With this ap-proach the end-of-life vehicle can be reused with limited rebuilding costs. Also the special customization of production cars can be performed.

8. References

1. Tomić R, Ilinčić P, Lulić Z (2009) Optical measuring on vehicle reconstruction, Innovative Automotive Technology - IAT'09, Nova Gorica, Slovenia, Proceedings

2. Ilinčić, P., Lulić, Z., Mahalec, I., Šagi, G., Tomić, R. (2009): Modification Of A City Bus Into A Touristic Panoramic Bus, Innovative Automotive Technology - IAT'09, Nova Gorica, Slo-venia, Proceedings

3. Ilinčić, P., Tomić, R., Šagi, G., Lulić, Z., Mahalec, I. (2009): Optical measurement methods – the new quality in reverse engineeringf design, 6. Naučno-stručni skup sa međunarodnim učešćem „KVALITET 2009“, Neum, Proceedings

4. Bühler, O.-P. A., Omnibustechnik – Historische Fahrzeuge und aktuelle Technik (2000), Vieweg & Sohn Verlagsgesellschaft, 2000, ISBN 3-528-03928-0

5. Pippert, H., Karosserietechnik – Konstruktion und Berechnung (Omnibus, Lkw, Pkw), 3. Aufl. (1998), Vogel Buchverlag, 1998, ISBN 3-8023-1725-4

6. TRITOP User Manual – Software, TRITOP v6.1, GOM mbH, 2008 7. ATOS User Manual, ATOS v6, GOM mbH, 2006 8. Topomatika d.o.o. - http://www.topomatika.hr/ 9. GOM mgh - http://www.gom.com/


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