Case studies

A Perfect Helmet for Formula 1

Schuberth Engineering AG in Braunschweig, Germany, develops and manufactures high-tech helmets that are also preferred by many Formula 1 teams. Michael Schumacher, Rubens Barrichello, Ralf Schumacher and Nick Heidfeld rely on the individual and tailor-made helmets.

For tailor-made manufacturing, the 3D digitizing system ATOS II, a product of GOM, records the shape of the racing driver's head precisely, quickly and completely.

During a Formula 1 race, forces occur that are four times the amount of the gravitational acceleration. In order to allow for best possible protection, convenient wearing and mobility, a light, stable and compact helmet is required that is individually adapted in shape and upholstery. For this purpose, a special layered structure with a high-performance carbon fiber is used, the material of which the Formula 1 monocoque chassis are made of as well.

For optimizing the shape of the helmet, reducing its weight and improving aerodynamics, it is important to precisely and completely record the individual shape of the driver's head.

Fig. 1: ATOS digitization R. Barrichello

For measuring, the hair is pressed on the head by means of a rubber skin in order to simulate the force of pressure of the helmet. Then, the ATOS system measures the head from different directions to completely digitize it.

Fig. 2: Measuring images

In the areas of the driver's face and ears, digitization is also performed with the helmet on, in order to later transform the point cloud of the head into the coordinate system of the helmet.

Fig. 3: Special helmet: Measuring for data transformation
into the coordinate system of the helmet

The result: A polygonal network which completely describes the shape of the head in detail. Then, using CAD, the helmet is constructed around the head. In case of suggestions regarding optimization - e.g. from the wind tunnel - it is possible to immediately check, if all minimum distances between helmet and head are met.

Fig. 4: Measured and helmet data

Due to the Schuberth technology and the GOM measuring system, Rubens Barrichello's helmet just weighs 1050 grams and thus is about 500 g lighter than his old helmet. That way, during a race, the muscles of the neck are essentially relieved. The slender form of the helmet results in less air resistance and better streaming to the air box. Therefore, an increased power of 10 HP is available.

We would like to thank the company Schuberth and Rubens Barrichello for the trust in the digitizing technology and the permission to share this special digitizing event

3D Measurement of a GAJETA Using TRITOP

The GAJETA is a small traditional fisher boat from Croatia . It is made of wood, approximately 7 to 12 meters long and was used in the Mediterranean Sea along the Adriatic coast for fishing and transportation between the islands. The boat excels by its rounded bow and stern, its high carrying capacity and its good navigability, especially on the rough sea. However, when less expensive plastic boats appeared that were mostly produced by foreign manufacturers, the number of authentic boats drastically reduced.

One of the few still existing Croatian shipyards, specialized in the construction and repair of wooden boats, is located in the small town of Nerezine on the island Losinj. Enthusiastic about the beauty and navigability of its 8 m long GAJETA, the Lekic family decided to restart the production of these wooden boats. They own a boat with excellent characteristics and have the infrastructure, the knowledge and the necessary experience in building wooden boats. Now, with the help of modern technology, they want to revive traditional boat building.

Making wooden boats is a big challenge. The boat's frame consisting of ribs, beam and keel defines the shape, the stability and the navigability of a boat. In the past, experienced craftsmen produced these wooden frames by guess and experience but with varying success.

A reliable method to create a good new boat was to copy a boat that proved to be successful. The ribs of the original boat were copied by stencils and their shape was transferred to the wood out of which the ribs for a new boat were produced. Modern technology simplifies and quickens the manufacturing of products having reproducible characteristics. In order to make it possible to create a faithful copy of the Nerezine boat, the Croatian company TOPOMATIKA performed a 3D measuring of the boat's shape using the photogrammetry system TRITOP of GOM. Figure 1 shows the equipment used for measuring: A professional digital photogrammetric camera, a notebook with TRITOP software for calculating the measuring points from the images, scale bars and additional equipment.

Fig. 1: Photogrammetric
system TRITOP

Fig. 2: Preparation of the bow
for photogrammetric recording

Approximately 300 reference point markers (adhesive paper with white points on a black background) were applied to the boat in order to exactly define the shape of the hull (fig. 2). Then, several images from various directions were recorded with the digital camera and loaded into the notebook PC. The TRITOP software automatically identified all reference point markers in the digital images with high accuracy.

After the reference point positions in all images are defined, the system automatically allocates the individual markers for the pre-orientation of the images and exactly calculates the 3D position of the reference points. Scale bars, the gauge length of which was ultra-precisely certified by an approved calibration office, provide for proper scaling of the measurement. The TRITOP computation results in numerous precise 3D measuring point coordinates in a global coordinate system.

Fig. 3: Reference points (red) and
camera positions (yellow) shown
in the TRITOP software

Fig. 4: Result of the photogrammetric
measurement - the measuring points
define the shape of the boat's hull

Fig. 3 shows the position of the measuring points on the boat's hull (red points) and the camera positions during recording of the images (yellow). The yellow lines represent the lines of sight from various camera positions to one measuring point. The intersection point of these lines of sight defines the point's exact position in space. Such lines were determined for all measuring points but are not all shown here for reasons of clarity. The exact positions of the measuring points in space (coordinates X, Y and Z) define the 3D shape of the boat. Thus, the dimensions of the boat (e.g. its length – fig. 4) are determined as well. A software for surface reconstruction then defined mathematical surfaces spanning between the measuring points. These surfaces completely define the shape of the hull as CAD model.

Calculated CAD model of the boat based on photogrammetric measurement

Fig. 5: Calculated CAD model of the boat based on photogrammetric measurement

Fig. 5 shows the calculated 3D model of the boat based on photogrammetrically measured reference points. Fig. 6 illustrates the characteristic lines of the hull (parallel sections in all three planes).

RCharacteristic lines (parallel sections) of the boat's hull

Fig. 6: Characteristic lines (parallel sections) of the boat's hull

Now, it is easy to adapt the CAD model to customer-specific modifications. Based on the CAD data and the sections lines, the designer can easily and precisely define the ribs and other supporting elements of the hull. Fig. 7 shows the shape of the ribs and the position of the top hull edge. The green area (right side) shows the bow ribs, the stern ribs are displayed in yellow. A CNC milling machine may use the CAD data to directly cut the shape of the ribs into the wood. For small lots, the rib shapes defined in CAD are printed on a plotter, manually transferred to the wood and sawn out.

Fig. 7: Rib shape, based on the
calculated boat model

Measuring the hull using TRITOP is fast, flexible and precise. The created mathematical model of the boat is a faithful copy of the original. Customer wishes can easily and correctly be implemented and optimal planning and execution of production is possible.

We would like to thank the Nerezine shipyard for their trust in TOPOMATIKA and for the permission to publish this report.

The Wolseley 6/110 mk11

Celebrating Bravery

In November 2010, the Imperial War Museum opened its newest gallery, 'Extraordinary Heroes'. The gallery, made possible by a £5m donation from Lord Ashcroft, is dedicated to the world's largest collection of Victoria Crosses and tells the stories of the personal bravery and sacrifice behind each medal. Lord Ashcroft's personal collection of 162 Victoria Crosses joined the 48 VCs and 31 George Crosses already held by the Museum.

A year earlier, in a shed in Surrey, a team of specialists gathered to make a start on re-creating a rather special part of the exhibition. Creative 2D and 3D modelling studio Berry Place was commissioned by the Imperial War Museum to produce a 1:17 scale model of a 1960s police car. The Wolseley 6/110 mk11 was driven by George Cross holder PC Tony Gledhill during a car chase across south east London in pursuit of a gang of armed robbers. The police car crashed, and PC Gledhill gave chase on foot, finally catching and apprehending the criminals, who included John McVicar - Scotland Yard’s 'Public Enemy No. 1' at the time.

Reverse Engineering with a Difference

In order to fulfil this commission, Berry Place needed to call in a range of experts to help them reverse engineer the Wolseley. They had several discussions with Guildford-based 3D scanning and measurement specialist Physical Digital Ltd and with Performance Engineered Solutions Ltd (PES - then Bromley Performance Engineered Solutions) to look at the feasibility of producing the scale model to budget and within the timescale.

In many reverse engineering projects, the end goal is a new part for production or the creation a prototype for quality control. For Physical Digital, PES and Berry Place, recreating a moment in history and illustrating the bravery of a single policeman added a new dimension to the project.

Building an exact replica of the police car, complete with crash damage, was a real challenge for the team at Berry Place. They needed to source exactly the same model of Wolseley in order to produce the car faithfully, and obtain exact measurements of the entire car to ensure complete accuracy. Working at a scale of one seventeenth of the original meant that scanning needed to be absolutely precise or details like headlights or chrome trim wouldn’t replicate properly.

Managing Director of Physical Digital, Tim Rapley, explains how Berry Place got their hands on the right car. "The team contacted the Wolseley Owners Club, along with several other auto collectors' organisations to see if they could find the right model and a willing owner who would let them measure and reverse engineer it. They were lucky enough to be put in touch with Conrad Parr of the Cambridge-Oxford Owners Club who had a Wolseley 6/110 mk II and was happy for us to measure it. What's more, Conrad was an authority on Wolseley in general and so was able to fill us in on period details and answer any questions that the Berry Place guys had in order to ensure that the model was as authentic as possible."

Challenging 3D Measurement

The Wolseley was delivered to Surrey and scanned using state-of-the-art GOM equipment - the ATOS IIe and the TRITOP. The requirement for the model to be faithful to the original meant that it was vital all the features were correctly captured during scanning. Any data that wasn’t precise enough simply couldn’t be scaled down to the right size for the digital models to be accurate. What's more, scanning was particularly complex because the scanners rely on the interaction of light with the measured surface in order to be accurate. Conrad's car was black, which absorbs the light, but shiny and with chrome detail, which reflects the light, so it presented unique problems to the Physical Digital team.

Setting up the scanning equipment, capturing precise data and transferring that data to the appropriate format took between five and six hours. The scanning process worked at a tolerance of 50 microns per m3, giving PES the very best information from which to reverse engineer the car and give Berry Place the final digital mockups they needed to begin building the model. Although the vehicle was scanned as a complete model, the data was then broken down into pre-determined sections so that the digital modelling could be done in manageable and accurate segments. Completing the measurement and digital modelling in this detail was vital because it allowed the Berry Place team to ensure that they could build each part exactly without compromising any of the rest of the vehicle. For example, the data for the hub caps was separated from the data for the wheels. This allowed the hub caps to be chrome plated without the whole wheel needing to go through the same process.

Precision Digital Engineering

For PES, the reduction in scale meant they were working at the very limits of the ability of the rapid prototyping processes they were using, making this project particularly challenging. Design Director Dan Fleetcroft explains why: "We used a combination of 3D CAD surfacing and solid modelling techniques with advanced Rapid Surfacing software to manipulate the scan data and complete the final design solution for the project. It was not just a question of giving Berry Place an exact copy of the car; we needed to design and engineer how the model would be assembled and how each component was going to be manufactured. The physical size of each component and desired finish - painted, chromed, transparent etc. - influenced the design and manufacturing techniques that would be employed." PES supplied Berry Place with .STL files for each component that needed to be built using Additive Manufacturing technologies and .STP files for those that needed to be machined. The incredible detail on the final files allowed Berry Place to produce a fantastic replica of the original police car.

George Cross Hero "Thrilled"

Whilst 3D measurement and digital reverse engineering was used to create the scale model of the Wolseley, Berry Place needed to handcraft the crash damage using period photographs from the scene as reference. Once finished, the car was delivered to the Imperial War Museum, where it was seen by PC Gledhill GC who said he was "thrilled" with the accuracy of the replica. The model can now be seen in the 'Extraordinary Heroes' exhibition, which is a free, permanent gallery.

Piper PA-31-310 Navajo Nose Cone

In order to install new hardware in the nose cone of a test aircraft, 2Excel Aviation required a new nose cone to be manufactured for their Piper Navajo. Physical Digital’s optical scanning technology was utilised to reverse engineer the new component to a high level of accuracy; using a combination of photogrammetry and 3D digitising to capture surface data.

Project Background

Scimitar, formed in 2008 and based at Sywell Aerodrome in Northamptonshire, are the dedicated research and development department of 2Excel Aviation, best known for THE BLADES Aerobatic Display Team. Scimitar design, test and evaluate avionic systems for use in military and civilian applications. The current project involves nose cone mounted instrumentation. To enable them to accurately mount the test system onto the airframe, a new nose cone needed to be manufactured. The final product needed to maintain its original form, to avoid costly CAA recertification, but remove the extrusions from the surface (Fig 1.0 & 4.1). The company requested that the nose cone be symmetrical, as the instruments were sensitive to geometry, whilst still fitting to the original airframe mating surface. Scimitar have used Physical Digital, and their optical scanning technology for past projects and are aware of the reduction in time and cost in reverse engineering components from scan data.

Fig 1.0

(Fig 1.0)

Objectives

Measure the current nose cone and airframe in position using TRITOP Photogrammetry
Digitise the external surface of the nose cone, 1m of airframe and mating surfaces using ATOS IIe
Capture critical geometry including locating pins, spheres, hole centres and diameters using Touch Probe
Align all data to agreed aircraft coordinate system
Reverse engineer from the scan data, creating a symmetrical nose cone
Evaluate new CAD model against original scan data

Data Capture Process

The digitising was carried out in the aircrafts storage hanger at Scimitar headquarters in Sywell. This was possible due to the portability of the equipment used and the ability to work in environments that other hardware would find difficult.

Three systems were used to capture the necessary data for this project:

1. TRITOP

The aircraft was prepared with the current nose cone fitted to the airframe, then coded and un-coded markers (Fig 3.0 & Fig 1.0) were applied to, and around, the areas to be captured. Extra markers were applied near the edges of the mating surfaces. This allowed Physical Digital to use the same coordinate system to scan the surface currently hidden inside the airframe.

A total of 49 photos were taken from different angles (Fig 2.0 & 2.1). From this the software calculated the 3D coordinates of all the markers. The accuracy was checked by Physical Digital Engineers and the file saved.

TRITOP - Optical CMM Explained
The TRITOP system takes high resolution 2D images of the object and created an accurate 3D coordinate framework based on digital photogrammetry techniques. Markers are applied (coded and un-coded) to and around the object along with internationally certified scale bars, then multiple photographs are taken from different angles. The software precisely works out the 3D coordinate of the centre of the markers. These coordinates are then used as a reference framework for scanning.

Marker Seen By different Cameras (Fig 2.0) Fig 2.0

Markers Seen By Single Camera (Fig 2.1) Fig 2.1

(Fig 3.0)

2. ATOS

The TRITOP file was imported into the ATOS scanning software, for use as a reference frame. Physical Digital then began to scan the airframe in the assembled state. When all the required data from the exterior was captured, the nose cone was carefully removed and the markers located around the edges were used to align the scan of the once hidden surface. This was repeated on the nose cone using the points on the outside to capture the mating surfaces within the same global alignment system.

The point cloud data was then converted by the software to form a polygon mesh file, the mesh was checked for any errors and post processed to a file size appropriate to the application. The original data was saved in order to produce an inspection report on the new CAD model. For this project .STL file was exported, for use in the available CAE systems.

(Fig 4.0)

(Fig 4.1)

TOS - 3D Digitising Explained
The ATOS (Advanced Topometric Sensor) system is a white light optical scanner which scans 3D objects and converts the images into a high density point cloud. This allows accurate measurement and capture of the shape and size of almost any object.

The scanning is based on optical triangulation and stereo-viewing. A projector is used to project a striped fringe pattern onto the object surface. These images are captured simultaneously by the cameras from different angles. 3D coordinates are captured fast to a high accuracy; this is repeated for up to seven million points per scan. The captured scan is then automatically integrated into the TRITOP framework; the sensor uses these markers to correctly align each scan. The markers are also used for self calibration and verification and can detect movement and lighting changes which would affect the accuracy.

3. TOUCH PROBE

The optically tracked touch probe was used to determine the location and size of each hole on the airframe and nose cone mounting surfaces (Fig 4.0). Using the touch probe enabled Physical Digital to create direct geometry within the coordinate system of the scan. These can be exported into the CAD software in compatible geometry files. For this project .IGS was used.

(Fig 5)

TOUCH PROBE Explained
The GOM touch probe is used for capturing geometry on the object that is being scanned. This handheld probe is optically tracked by the ATOS sensor and calibrated to a high accuracy; it allows movement of both the sensor and probe by using the TRITOP markers to precisely align the data when captured.

Reverse Engineering: Creating CAD Surfaces

The .STL file created from the scan data was imported into the CAD software. Using exact geometry matched (within agreed tolerance) to the mesh, a CAD surface was produced. This was mirrored to create a symmetrical nose cone. The .IGS files from the Touch Probe were then used to trim holes and features in the correct positions within the global coordinate system (Fig 7.0).

When the geometry of the nose cone was complete, the mating surface was assessed to see if a planar surface would correctly fit to the airframe. If this was not the case, a freeform surface would have been applied to the geometrically accurate nose cone. However, when the surface was inspected it was found to be within tolerance and a flat surface was chosen (Fig 6.0).

(Fig 6.0)

(Fig 7.0)

Inspection & Verification

The final part of the project was to verify the new CAD data against the original scan. Scimitar were keen to keep the new nose as close to the original as possible, whilst removing the features (Fig 7.0). Physical Digital supplied an inspection report using the inspection module of the ATOS Professional software.

The 3D images throughout this case study were taken from the inspection report that was produced.

This graphical representation shows the vector distance between the original scan data and the new CAD model. The green areas are within 1mm of the original. It is interesting to note the red area on the top right: this shows the airframe has been deformed (Fig 8.0). In this project the symmetry was important and the CAD was made slightly smaller to allow manual blending to the airframe.

A complete set of data was supplied to Scimitar, including: (Fig 8.0)

Original scan data
New CAD Model
Inspection reports
GOM INSPECT (free inspection software for further analysis)

(Fig 8.0)

Achievements

Quick and accurate capture of all surfaces
Creation of nose CAD data for use in all future projects
Reduction in time, compared to traditional methods
Increases in accuracy, compared to alternative methods
Final product inspection using Computer Aided Verification

With Special Thanks To:
2Excel Aviation Ltd
The Tiger House
Sywell Aerodrome
Sywell
Northamptonshire
NN6 0BN
+44 1604 671309

Supermarine Spitfire MkIIa - P7350

In order to create a highly accurate scale model of a MkIIa Spitfire, Physical Digital were commissioned by Amalgam Fine Model Cars to digitise an original. The aircraft, which is based at the Battle of Britain Memorial Flight (BBMF), RAF Coningsby, in Lincolnshire is the last remaining example of an airworthy MkIIa that saw active service in the Battle of Britain. The digital data was also presented to the BBMF for digital archiving, to be used as reference if the aircraft was ever damaged. A combination of photogrammetry, Touch Probe and 3D optical scanning was used to capture surface data.