FibreMap FP7 608768

1

FibreMap 608768

Automatic Mapping of Fibre Orientation for Draping of Carbon Fibre Parts

SEVENTH FRAMEWORK PROGRAMME NMP Priority

Deliverable D3.2: “Laboratory setup of the workcell for 3D part scanning”

Due date of deliverable: 2014-11-30 Actual submission date: 2014-12-02

Start date of project: 1st September 2013 Duration: 36 months Coordinator: Christian Eitzinger Profactor Revision 1 Lead Beneficiary: UNIPD Contributions by: UNIPD, ITROBOTICS

Project co-funded by the European Commission within the 7th Framework Programme

Dissemination Level PU Public X

PP Restricted to other programme participants (including the Commission Services)

RE Restricted to a group specified by the consortium (including the Commission Services) CO Confidential, only for members of the consortium (including the Commission Services)

FibreMap FP7 608768

2

Contents

1. Introduction ........................................................................................................................................... 3

2. Overview of the work cell ..................................................................................................................... 3

2.1 Comau Smart5-SiX, C4G Open and PC interconnections .................................................................... 3

2.3 Measurement sensor ............................................................................................................................. 5

3. 3D Work Cell Simulation ...................................................................................................................... 8

4. Conclusions ........................................................................................................................................... 9

FibreMap FP7 608768

3

1. Introduction This document describes the laboratory setup of the work cell installed at the University of Padova for 3D part scanning. The hardware building blocks of the FibreMap demonstrator are presented, together with their interconnections. The interface to the work cell simulator is also described. As we will see, the developed interface between the software systems and the hardware is generic so that different robots and sensor systems can be easily integrated.

2. Overview of the work cell The FibreMap demonstrator is composed of a robot equipped with a particular sensor which allows to measure fibre orientation, as shown in Figure 1a. The work cell set up at the University of Padova is shown in Figure 1b. The scanning robot is surrounded by a cage with proper safety measures allowing to immediately stop the robot if someone enters the cage. Outside the cage, the robot controller is placed, together with two PCs used for communicating with the robot and for processing the acquired data.

(a) Robot scanning a test part (b) Work cell at UNIPD Figure 1: Pictures of the work cell set up at UNIPD.

2.1 Comau Smart5-SiX, C4G Open and PC interconnecti ons The robot used for the 1st year demonstrator is a Comau Smart5-SiX. Comau

Smart5-SiX is an anthropomorphous robot with six axes / degrees of freedom and a payload of 6kg at the wrist. Its repeatability is +/- 0.05 mm and its working area is illustrated in Figure 2a. The robot is equipped with a Comau C4G control unit which maintains a real-time communication with the robot every 2 ms and which is endowed with the “Open” interface, which allows the control by means of a PC.

As depicted in Figure 2b, the C4G module is also connected to a PC running Ubuntu 13.04 and the RealTime Application Interface (RTAI) for Linux, which allows to write applications while preserving real-time communication with the robot controller. This PC is used to listen to TCP position messages sent by the path planning module

FibreMap FP7 608768

4

and send them to the robot controller. If more messages are received, they are stored in a First-In-First-Out queue, which is then read by the robot control thread. Moreover, another thread is responsible for the streaming of the robot positions and time stamps over the network by means of UDP messages, so that every PC connected to the network can know the position of the robot every 2 ms. Another PC, running Windows 7, is connected by Ethernet connection to the Linux PC. This PC is responsible for all the high-level tasks of the demonstrator:

• the generation of the scanning path, • the synchronization of robot and camera time stamps, • the image acquisition, • the fibre angle computation, • the projection of the fibre angles to the 3D model of the part.

The hardware/network interconnections between these PCs, the robot and the sensor are illustrated in Figure 3. ETH1 is responsible for the communication between the Linux PC and the robot, while ETH2, ETH3 and ETH4 connect the robot and the two PCs to the same local network, allowing for example to emulate the robot Teach Pendant with the WinC4G software or the Linux PC to stream messages to the Windows PC and viceversa. Finally, the sensor is connected to the Windows PC by means of an Ethernet cable (ETH5) for streaming the images and a Serial to USB cable responsible of triggering the illuminators.

(a) Robot working area

FibreMap FP7 608768

5

(b) Description of how the different tasks are distributed to the different machines

Figure 2: 1st year demonstrator installed at the University of Padova

Figure 3: Description of the hardware interconnections set up in the work cell.

2.3 Measurement sensor The core components of the first version of the fibre angle sensor (FScan sensor) are a light ring with 48 LEDs and a PhotonFocus MV-1-D1312 GigE Camera. The resolution of the camera is 1312x1024 pixel. The lens attached to the camera is a SKR STD XENON 17/0,95. A dedicated microcontroller triggers the camera for image capturing and at the same time switches on and off groups of neighboring LEDs. Figure 4 shows a photo of the sensor. The sensor is powered over two pins of a D-Sub (DB-25) jack. A serial RS485 connection also runs over this D-Sub jack and connects the controlling PC with the microcontroller (TRI cable of Figure 2). Image data is delivered by the sensor over Gigabit Ethernet via a standard RJ45 jack. For mechanical integration with the robot, an adapter was manufactured which can be attached to the sensor.

FibreMap FP7 608768

6

For attaching the FScan sensor to the robot TCP, the two plaques illustrated in Figure 5 have been manufactured. Two pictures of the sensor mounted on the robot are shown in Figure 6.

Figure 4: Version 1 of fibre angle sensor (FScanH1)

(a) Plaque attached to the robot TCP. (b) Plaque for attaching the FScan sensor.

Figure 5: Mechanical drawings of the plaques needed to attach the FScan sensor to the robot. Legend: M6: 6mm unthreaded holes, M6-I: 6mm unthreaded flared holes, S: holes for small plugs between the two plaques, M6-F: threaded 6mm holes, M8-I: 8mm unthreaded flared holes.

FibreMap FP7 608768

7

(a) Sensor mounted on the robot flange (b) Sensor taking images of a checkerboard Figure 6: Pictures of the FScan sensor mounted on the robot TCP.

In order to perform a scan, the object to be scanned has to be placed in a known position with respect to the robot reference frame. Since the objects to be scanned for the FibreMap project have different sizes and shapes and the preforms are not rigid, it was not possible to produce a fixture for aligning the object to a known reference frame. Instead, a part calibration procedure has been studied in order to relate the reference frame of the part with that of its CAD model by touching three reference frames on the part with a tip mounted on the robot flange. This procedure is shown in Figure 7, where a L bar is used to better detect the reference points starting from the alignment of this bar to the part. For the future of the project and for real industrial installations, we plan to mark these reference points on the part at manufacturing time, so that they can be easily retrieved for calibration. This procedure consists in drawing with the gypsum the contour of the tool on the preform while the tool is closed.

Figure 7: Robot-part calibration based on aligning a rig to the part.

FibreMap FP7 608768

8

3. 3D Work Cell Simulation The whole work cell developed at UNIPD can be simulated thanks to the work cell simulation software developed by IT+Robotics. This allows to automate the definition of the fibre parts inspection cycle. The work cell and process simulation is organized in different stages. In a first step, the virtual work cell has to be defined. To this end, the work cell components have been designed with the Component Editor (CE) application. Every component is represented as a kinematic chain that is a set of links connected to each other by joints to form a tree structure (or more generally a graph). Every link has one or more degrees of freedom relatively to its parent link. In particular, in the FibreMap work cell, two types of components are needed: the inspection device and the robot manipulator. In order to help the user, the CE has been customized with two particular plugins:

• A robot plugin to define the Denavit-Hartenberg robot parameters, set up axes limits and speeds and custom inverse kinematics. Using this plugin a virtual Comau Smart5 SiX has been created.

• A camera plugin that is used for handling the simulation of the second crucial component, the sensor vision system. For the demonstrator a virtual component representing the Profactor sensor has been designed.

Each component can be enhanced with custom reference frames that are useful for getting and setting particular transformations between the robot and the component. For instance, a particular reference frame has been defined at the optical centre of the camera. This information is necessary for several reasons:

• After the hand-eye calibration, to place the virtual camera correctly with respect to the robot.

• In the coverage planner algorithm, to specify the position and the distance of the camera with respect to the surface of the product.

The virtual components have been used in WorkCell Editor to set up the corresponding virtual work cell of the UNIPD demonstrator. The work cell layout can be completed adding environmental objects, such as the floor or the product fixtures. Collisions with all these objects are taken into account. To achieve a more precise positioning of each component, the robot-part calibration described in Section 2.3 is needed. The estimated reference frame has then to be inserted in the calibration tool. In this way every object will be automatically placed in the exact position relatively to the robot. This procedure has been used to correctly position the carbon fibre part in the UNIPD cell. To manage and setup the inspection process a first version of the main Fibremap application has been developed. The application is a front end to help the user to configure all the parameters for the inspection system. When the application starts, a new inspection project must be created using, other than the previously created work cell, the 3D model of the product to be inspected. Given this, the Fibremap application contains an editor where a specific panel to set-up the parameters for the path planning has been developed (see Figure 8). The position of the product with respect to the robot is crucial for a meaningful inspection. Then, the application has been enhanced with the WorkCell Editor calibration tool (see Figure 9).

FibreMap FP7 608768

9

The trajectory generated with the simulator is then translated to the robot JSON data format and sent through the developed communication module between the path planning software and the path listener in the Linux PC.

4. Conclusions In this document, we presented the work cell developed for the FibreMap project for scanning carbon fibre parts. The work cell design and the calibration procedures have been developed allowing to scan different objects in the same work cell. Moreover, the work cell is modular: other than the part to be scanned, also the robot or the sensor

Figure 9: Fibremap calibration tool

Figure 8: Product settings and coverage planner section

FibreMap FP7 608768

10

could be easily replaced with minimal change in the work cell. In particular, if the sensor or the robot will change, only the drivers, the CAD models and the intrinsic parameters used for them in the work cell simulation software have to be replaced. This work cell will be used throughout the project for developing fibre mapping algorithms, scanning the test cases for providing input to the simulation software and for demonstrating FibreMap progress to possible end users and system integrators. We foresee that the entire work cell will be used for four months per year for this project. After the project, the work cell could still be used for demonstrating the achievements of this project since it will be maintained at the University of Padova to be exploited also for other research projects. We think that this work cell could also reflect how an industrial work cell would look like. To be sure to address all parts that will become relevant in the automotive industry, this work cell will need to cover an operating area of about 2x2 m2, as in the work cell at the University of Padova. What would need to be adapted to industrial environments is the PC used for processing, which should probably be replaced with an industrial PC.