This article presents a robust and heavy duty physical latching connection mechanism, which can be actuated with DC motors to actively connect and disconnect modular robot units. The special requirements include a lightweight and simple construction providing an active, strong, hermaphrodite, completely retractable connection mechanism with a 90 degree symmetry1 and a no-energy consumption in the locked state. The mechanism volume is kept small to fit multiple copies into a single modular robot unit and to be used on as many faces of the robot unit as possible. This way several different lattice like modular robot structures are possible. The large selection for dock-able connection positions will likely simplify self-reconfiguration strategies. Tests with the implemented mechanism demonstrate its applicative potential for self-reconfiguring modular robots.

This paper presents an experimental research that focuses on collaboration in a multi-player game. The aim of the project is to study the cognitive impacts of awareness tools, i.e. artifacts that allow users of a collaborative system to be aware of what is going on in the joint virtual environment. The focus is on finding an effect on performance as well as on the representation an individual builds of what his partner knows, plans and intends to do (i.e. mutual modeling). We find that using awareness tools has a significant effect by improving task performance. However, the players who were provided with this tool did not show any improvement of their mutual modeling. Further analysis on contrasted groups revealed that there was an effect of the awareness tool on mutual modeling for players who spent a large amount of time using the tool.

This paper presents an experimental research that focuses on collaboration in a multi-player game. The aim of the project is to study the cognitive impacts of awareness tools, i.e., artifacts that allow users of a collaborative system to be aware of what is going on in the joint virtual environment. The focus is on finding an effect on performance as well as on the representation an individual builds of what his partner knows, plans and intends to do (i.e., mutual modeling). We find that using awareness tools has a significant effect by improving task performance. However, the players who were provided with this tool did not show any improvement of their mutual modeling. Further analysis on contrasted groups revealed that there was an effect of the awareness tool on mutual modeling for players who spent a large amount of time using the tool.

The Biologically Inspired Robotics Group (BIRG, http://birg.epfl.ch) at the Swiss Federal Institute of Technology in Lausanne (EPFL) carries out research in robotics, computational neuroscience, nonlinear dynamical systems, and learning/optimization algorithms. We are interested in understanding the fascinating control and learning abilities observed in animals, and to develop systems –programs, simulations, and robots– that exhibit and replicate those abilities. In particular, we are interested in developing systems that evolve, adapt, self-organize, and self-repair. The group was founded in November 2002. It is headed by Auke Ijspeert (assistant professor), and is composed of one part-time postdoc –Dr Olivier Michel–, three PhD students –Jonas Buchli, Alessandro Crespi, and Ludovic Righetti–, one programmer –Yvan Bourquin–, and two part-time electromechanical technicians –André Badertscher and André Guignard. The group has funding from the Swiss National Science Foundation, the Swiss CTI (Swiss Federal Office for Professional Education and Technology), the EPFL, the European Space Agency, and the European Union, through the Integrated Project ROBOT-CUB (IST-FET6).

This paper describes the findings of an experimental research concentrating on collaboration in a multi-player video game. The overall goal is to study the cognitive impacts of the awareness tools. The focus is in finding an effect on performance as well as on the representation an individual build of what his partner knows, plans and intends to do (i.e. Mutual Modelling). Using an awareness tools has a significant effect by improving task performance. However, the players who were provided with this tool did not show any improvement of their mutual modelling. Further analysis on contrasted groups revealed that there was an effect of the awareness tool on mutual modelling for players who spent a large amount of time using the tool.

A recent consensus within an international society for sports traumatology revealed that approximately 40% of ACL grafts are being surgically misplaced in current clinical practice. To help solve this problem, a computer-assisted system has been developed at the M.E. Müller Institute for Biomechanics to perform intraoperative planning and guidance of ACL replacement. Dynamic reference bases are fixed on the femur and tibia to track the knee's movement. No intraoperative imaging is required, and potential ligament attachment sites can be directly digitized using a computerized palpation hook in a minimally invasive fashion when used in conjunction with standard endoscopic tools. The palpation hook can be used by the surgeon to interactively define various anatomical structures and reference landmarks that are important for proper ligament positioning. The system can input a standard diagnostic X-ray (sagittal view of the femur) and allows intraoperative registration of this image with the patient to provide valuable X-ray landmarks for intraoperative guidance. The computer helps in situ planning of ligament placement by providing the surgeon with a 3D overview of the relevant anatomical landmarks and information on graft impingement and elongation for various simulated surgical insertions and graft sizes. After planning, the computer helps guide placement of the chosen insertion tunnels. This approach provides an augmented 3D view of knee anatomy and ligament function prior to drilling that is not possible with current procedures. The flexibility of the system in permitting surgeon-defined landmarks and free interpretation of functional factors allows it to support a variety of surgical workflows and techniques.

Interdisciplinary communication of three-dimensional kinematic data arising from in vitro biomechanical tests is challenging. Complex kinematic representations such as the helical axes of motion (HAM) add to the challenge. The difficulty increases further when other quantities (i.e. load or tissue strain data) are combined with the kinematic data. The objectives of this study were to develop a method to graphically replay and animate in vitro biomechanical tests including HAM data. This will allow intuitive interpretation of kinematic and other data independent of the viewer's area of expertise. The value of this method was verified with a biomechanical test investigating load-sharing of the cervical spine. Three 3.0 mm aluminium spheres were glued to each of the two vertebrae from a C2-3 segment of a human cervical spine. Before the biomechanical tests, CT scans were made of the specimen (slice thickness=1.0 mm and slice spacing=1.5 mm). The specimens were subjected to right axial torsion moments (2.0 Nm). Strain rosettes mounted to the anterior surface of the C3 vertebral body and bilaterally beneath the facet joints on C3 were used to estimate the force flow through the specimen. The locations of the aluminium spheres were digitised using a space pointer and the motion analysis system. Kinematics were measured using an optoelectronic motion analysis system. HAMs were calculated to describe the specimen kinematics. The digitised aluminium sphere locations were used to match the CT and biomechanical test data (RMS errors between the CT and experimental points were less than 1.0 mm). The biomechanical tests were "replayed" by animating reconstructed CT models in accordance with the recorded experimental kinematics, using custom software. The animated test replays allowed intuitive analysis of the kinematic data in relation to the strain data. This technique improves the ability of experts from disparate backgrounds to interpret and discuss this type of biomechanical data.

Anterior cruciate ligament (ACL) reconstruction with an autogenous graft through the use of a minimally invasive endoscopic approach has become the standard in ACL replacement. The arthroscopically assisted technique causes minimal trauma and can sometimes be performed on an outpatient basis. There have been, however, alarming reports of high misplacement rates of these grafts. These misplacements can partially be attributed to the restricted local view provided by arthroscopy, which does not give the surgeon a global overview of ligament position with respect to knee anatomy. Thirty-degree endoscopes, lens distortions, and the difficulty of judging depth from the 2-dimensional (2-D) view makes mental orientation of internal structures with respect to desired reattachment sites difficult. Another problem is the lack of a general consensus on the best type of graft and on the proper placement of these grafts. As a result, there is a rather large variety of surgical techniques and a variety of different graft types. To help solve these problems, we have developed a computer-assisted system to aid surgeons in planning and intraoperative placement of ligament grafts.

The application of spinal interbody cages as an adjunct to spinal fusion may be regarded as common surgical practice for a number of spinal interventions. Morbidity from surgical approaches as well as learning curves for planning of cage insertion and the actual in vivo application may be considerable, however. On the other hand, computer-assisted surgery (CAS) technologies have been successfully introduced into the field of orthopaedic surgery and may be regarded as routine, at least for the area of pedicle screw insertion. The present study evaluates the potential of computer-assisted technologies in assisting spinal cage application, (ie, the Bagby and Kuslich cage). It shows that technological priciples are available to accurately plan cage insertion, including the preoperative demonstration of distraction and alignment consequences for the entire segment. Furthermore, during surgery, the surgeon may be guided to the appropriate spinal segment, followed by precise execution of the preoperative plan. These features are combined with endoscopic techniques and are available for in vitro training of spinal surgeons. For in vivo applications, however, matching and registration procedures have to be refined to enable detection of bony structures, especially from a single anterior surgical approach. For this purpose, various possibilities, such as the use and integration of ultrasound, are under evaluation.

Femoral graft placement is an important factor in the success of ACL-reconstruction. Besides improving the accuracy of femoral tunnel placement, Computer Assisted Surgery (CAS) can be used to determine the anatomic location. This requires a 3D femoral template with the position of the anatomical ACL-center, based on endoscopical measurable landmarks. This study describes the development and application of this method. The template is generated through statistical shape analysis of the ACL-insertion, with respect to the anteromedial- (AMB) and posterolateral bundle (PLB). The data is mapped onto a cylinder and related to the intercondylar notch surface and the cartilage border on the lateral notch wall (n=33). The template was programmed in a computer-assisted system for ACL-replacement and validated. The program allows real-time tracking of the femur and interactive digitization under endoscopic control. In a wizard-like fashion the surgeon is guided through steps of acquiring the landmarks for the template alignment. The AMB- and PLB-center are accurate positioned within 1-3 mm of the anatomic insertion-centers in individual knees.

Bending and shaping of longitudinal orthopedic fixation devices like rods and plates is often a difficult and time-consuming process to perform during surgery under sterile conditions. This study presents a novel device for implant contouring and introduces two strategies to obtain parameters necessary for the bending process. The first strategy is based on surgical navigation techniques as established within the framework of computer-assisted orthopedic surgery. Geometrical landmarks, e.g., the location of pedicle screws in a case of posterior spinal fixation, are collected with a three-dimensional pointing device. Subsequently, the final shape of the implant and the associated contouring parameters are calculated. The alternative strategy utilizes a flexible material intended to be used intra-operatively to enable the optimal shape of the implant to be modeled by hand. Contour parameters are calculated from a depth image of this model obtained using an object scanner. Bending of spinal rod systems is used to illustrate both strategies. A newly designed semi-automatic bending machine is proposed to impose the computed deformation on the implant material once parameters are obtained. Integrating the bending device into a system for computer-assisted surgery allows for the interactive control of the contouring process.