Antonio Vasilijevic | FER Zagreb (original) (raw)

Papers by Antonio Vasilijevic

Abstract: This paper describes a procedure that utilizes a series of off-line algorithms for pre-... more Abstract: This paper describes a procedure that utilizes a series of off-line algorithms for pre-planning a two-dimensional path for an AUV in a cluttered waterspace. The trajectory is planned as a clothoidal spline or interpolation based on the work of

2018 IEEE 8th International Conference on Underwater System Technology: Theory and Applications (USYS), 2018

Positioning, Navigation and Communication on land would be very difficult and nowadays unimaginab... more Positioning, Navigation and Communication on land would be very difficult and nowadays unimaginable without satellite communication networks. The situation underwater is much more complex due to high attenuation of radio waves. Moreover, due to the different nature of communication above and underwater, facilitation of relevant data flow between these environments requires existence of some kind of communication hub. Idea of replicating concept of positioning/communication satellites able to play both roles simultaneously to set up Internet of Underwater Things (IoUT), is therefore, worth considering. In light of this idea, the University of Zagreb developed a oneman portable autonomous surface vehicle (ASV) with suitable lightweight localization and communication payload. This paper describes an ASV and its role as a satellite for the underwater environment and implementation of IoUT. The paper elaborates three real applications: support to diving operations where a diver tracking ...

2011 Proceedings of the 34th International Convention MIPRO, 2011

Unmanned Underwater vehicles (UUVs) are routinely used for data collection during underwater rese... more Unmanned Underwater vehicles (UUVs) are routinely used for data collection during underwater research missions. UUV operators which perform advanced data collection are usually not qualified for data interpretation. On the fly adaptation of data collection methods based on interpreted data can increase data quality and lower the operator's effort. However, this requires the presence of an expert on site. In order to avoid this, a system of remote monitoring and control over the Internet is proposed. Closing the vehicle control loop over the Internet is problematic due to latency issues, therefore a supervisory control approach is used. This requires only high-level commands to be sent over the Internet while closing the control loop locally. Service oriented architecture (SOA) is used as an API for vehicle monitoring and mission control, while software gadgets are used to display collected data and to send commands for mission adaptation. Gadgets provide support for modifying an...

OCEANS 2017 - Aberdeen

This paper described the basic concept behind the second and final validation trials of the Cogni... more This paper described the basic concept behind the second and final validation trials of the Cognitive Autonomous Diving Buddy (CADDY) system. The CADDY system is composed of three components: autonomous surface vehicle (ASV), an autonomous underwater vehicle (AUV) named BUDDY, and a diver. CADDY aims to establish an innovative setup between a diver and companion autonomous robots (underwater and surface) that exhibit cognitive behaviour by adapting to diver's physical state, and actions, thereby improving overall diving experience by assisting the diver. Although certain problems were encountered during trials, the collected data and experience were valuable to identify potential improvements. Most importantly, divers felt safe and comfortable working and interacting with a robotic BUDDY thus achieving the primary goal.

Sustainability

Documentation and conservation of underwater cultural heritage (UCH) are crucial to preserving hu... more Documentation and conservation of underwater cultural heritage (UCH) are crucial to preserving humankind’s history and traditions, safeguarding tangible testimonies of past human life while ensuring its accessibility to future generations. The TECTONIC (Technological Consortium TO develop sustainability of underwater Cultural Heritage) project is promoting an intersectoral collaboration between academic and non-academic professionals (i.e., archaeologists, conservators, geologists, engineers, etc.) working on different topics related to UCHs, to find solutions to the issues still existing in the field. The overall aim is the exchange of skills for the improvement and assessment of innovative materials and techniques to develop solutions and marketable products for the conservation and management of the UCH, sustainably. To achieve its overall aim, TECTONIC is undertaking activities driven by the following objectives: (a) the study, documentation, and mapping of selected UCHs; (b) th...

Remote Sensing

Underwater cultural heritage sites are subject to constant change, whether due to natural forces ... more Underwater cultural heritage sites are subject to constant change, whether due to natural forces such as sediments, waves, currents or human intervention. Until a few decades ago, the documentation and research of these sites was mostly done manually by diving archaeologists. This paper presents the results of the integration of remote sensing technologies with autonomous marine vehicles in order to make the task of site documentation even faster, more accurate, more efficient and more precisely georeferenced. It includes the integration of multibeam sonar, side scan sonar and various cameras into autonomous surface and underwater vehicles, remotely operated vehicle and unmanned aerial vehicle. In total, case studies for nine underwater cultural heritage sites around the Mediterranean region are presented. Each case study contains a brief archaeological background of the site, the methodology of using autonomous marine vehicles and sensors for their documentation, and the results in...

Remote Sensing

Plitvice Lakes National Park is the largest national park in Croatia and also the oldest from 194... more Plitvice Lakes National Park is the largest national park in Croatia and also the oldest from 1949. It was added to the UNESCO World Natural Heritage List in 1979, due to the unique physicochemical and biological conditions that have led to the creation of 16 named and several smaller unnamed lakes, which are cascading one into the next. Previous scientific research proved that the increased amount of dissolved organic matter (pollution) stops the travertine processes on Plitvice Lakes. Therefore, this complex, dynamic but also fragile geological, biological and hydrological system required a comprehensive limnological survey. Thirteen of the sixteen lakes mentioned above were initially surveyed from the air by an unmanned aircraft equipped with a survey grade GNSS and a full frame high-resolution full-screen camera. From these recordings, a georeferenced, high-resolution orthophoto was generated, on which the following surveys by a multibeam sonar depended. It is important to menti...

IEEE/ASME Transactions on Mechatronics

Water pollution generated by accidental spill of hazardous materials is a growing problem worldwi... more Water pollution generated by accidental spill of hazardous materials is a growing problem worldwide. There is an urging need for a tool which would help environmental response teams to perform rapid understanding of the location and the extent of the spill, to effectively establish an appropriate response. This paper presents a cooperative robotic system for environmental monitoring consisting of an Autonomous Underwater Vehicle (AUV) and an Autonomous Unmanned Surface Vehicle (USV). The main contributions of the paper are: systematic description of the design and implementation of the proposed cooperative robotic system, novel human-on-the-loop (HOTL) approach applied on the system for environmental monitoring and demonstration of the results of the open-sea experiments on pollution deliberately caused by harmless Rhodamine WT, carried out in Cartagena, Spain in June 2015. The proposed HOTL system provides near real-time pollution measurement data, while not consuming a significant amount of human time and effort. It supports decision-making and allows the operator to initiate the most adequate mission in a current situation, i.e., ensures mission change on-the-fly. While the AUV samples the ocean, the USV maintains the localization and communication data transfer to the control centre and corrects the AUV's dead reckoning error.

Applied Acoustics

Abstract The majority of Human–Machine Interfaces (HMIs) designed for the teleoperation of unmann... more Abstract The majority of Human–Machine Interfaces (HMIs) designed for the teleoperation of unmanned vehicles only present information visually. Frequent overloading of the operator’s visual channel may result in accidents. To reduce the occurrence of accidents and improve overall operating performance, this paper proposes the extension of the HMI to the hearing modality. The proposed HMI takes the form of a spatial auditory display for complex navigation tasks such as path following (route guidance) or trajectory tracking. The interface incorporates two novel components. The first is the application of a modified “lookahead distance” guidance strategy, as a guidance law for generating a reference. The reference is presented to the operator as a spatial auditory image of the virtual target to be followed. Before being presented to the operator, the reference information is preconditioned through “supernormal” transformations to increase azimuth and distance resolution in regions of interest and thus to improve efficiency and overcome the comparative disadvantages of the hearing channel. A series of experiments show that the proposed guidance strategy provides a comprehensible and effective auditory reference. The enhanced supernormal auditory interface improves performance by reducing the tracking error of both path following and trajectory tracking compared to a non-enhanced interface without the supernormal transformation. Experiment participants report that the novel auditory interface is intuitive and easy to use, providing very good situational awareness. While the auditory interface investigated in this paper is shown to be effective for the teleoperation of unmanned vehicles, it may have other applications such as navigation for the visually impaired.

Automatika Casopis Za Automatiku Mjerenje Elektroniku Racunarstvo I Komunikacije, Jul 22, 2011

Original scientific paper Currently, one of the most widely used distance measures in speech and ... more Original scientific paper Currently, one of the most widely used distance measures in speech and speaker recognition is the Euclidean distance between mel frequency cepstral coefficients (MFCC). MFCCs are based on filter bank algorithm whose filters are equally spaced on a perceptually motivated mel frequency scale. The value of mel cepstral vector, as well as the properties of the corresponding cepstral distance, are determined by several parameters used in mel cepstral analysis. The aim of this work is to examine compatibility of MFCC measure with human perception for different values of parameters in the analysis. By analysing mel filter bank parameters it is found that filter bank with 24 bands, 220 mels bandwidth and band overlap coefficient equal and higher than one gives optimal spectral distortion (SD) distance measures. For this kind of mel filter bank, the difference between vowels can be recognised for fulllength mel cepstral SD RMS measure higher than 0.4-0.5 dB. Further on, we will show that usage of truncated mel cepstral vector (12 coefficients) is justified for speech recognition, but may be arguable for speaker recognition. We also analysed the impact of aliasing in cepstral domain on cepstral distortion measures. The results showed high correlation of SD distances calculated from aperiodic and periodic mel cepstrum, leading to the conclusion that the impact of aliasing is generally minor. There are rare exceptions where aliasing is present, and these were also analysed.

OCEANS 2015 - Genova, 2015

This paper summarizes the main accomplishments of the first year of the FP7 project “CADDY - Cogn... more This paper summarizes the main accomplishments of the first year of the FP7 project “CADDY - Cognitive Autonomous Diving Buddy”. The main objective of the project is to replace a human buddy diver with an autonomous underwater vehicle and add an autonomous surface vehicle to improve monitoring, assistance, and safety of the diver's mission. While all envisioned objectives of the project are listed, the paper focuses on the results that were obtained in the following areas of research: development of the multicomponent robotic system, “Seeing the Diver” (underwater perception), “Understanding the Diver” (cognition in the form of interpreting diver sign language, behaviour and physiological parameters), and diver-robot cooperation and control.

21st Mediterranean Conference on Control and Automation, 2013

Majority of ROVs are underwater vehicles with relatively slow dynamics virtually providing a ROV ... more Majority of ROVs are underwater vehicles with relatively slow dynamics virtually providing a ROV pilot extra time to perform other tasks, such as inspections and arm operation. However, with many tasks performed simultaneously with flying, the relevant information is typically dispersed on a number of screens overloading the pilot's visual channel. Surprisingly, there is very little research examining the unique human-factors problems associated with unmanned underwater vehicles. Use of audio display has been suggested as a means to reduce visual workload, to enhance situation awareness, and mitigate the visual and cognitive demands of contemporary ROV operations. Our research investigate the effects of secondary visual tasks on operators workload and performance using standard visual navigation interface, augmented reality visual interface and audio interface. All experiments were performed on the state-of-the-art, real-time ROV simulator developed by Mobile & Marine Robotics Research Centre, University of Limerick and augmented reality system developed by Laboratory for Underwater Systems and Technologies, University of Zagreb. As expected, the results show that in no-load conditions visual guidance is better than the guidanceby-sound. By contrast, the effects of secondary visual load affect operators' performance. The use of augmented reality paradigm and especially hearing, in the form of the auditory display, emerges as an important advantage. Improvement depends on a level of experience in using auditory guidance system. Practice has a major effect on performance, bringing us to the conclusion that there is a more room for improvement in using auditory interface.

Lecture Notes in Computer Science, 2013

Research related to diver safety, navigation and monitoring has been identified as crucial for ad... more Research related to diver safety, navigation and monitoring has been identified as crucial for advancing diving activities. These issues are usually dealt with by pairing up divers and adopting well defined rules for diving operations to reduce the chance of accidents. However, during more challenging dives (such as technical dives) these procedures may not be sufficient to ensure almost accident-free operations, for the divers must manoeuvre in complex 3D environments, carry cumbersome equipment, and focus attention on operational details. In this work it is stated that research and technological development in the area of cognitive robotics can significantly contribute to the effectiveness and safety of diving operations. The current research performed in LABUST is based on an autonomous surface platform for following divers and transmitting GPS signal to the underwater. Future envisioned applications include the development of a cognitive autonomous diving buddy consisting of both the surface platform and an underwater vehicle that will serve as diving "guide", "slave" and "observer".

Proceedings of the 19th IFAC World Congress, 2014

For teloperated unmanned vehicles, mishaps tend to occur during the periods of high workload, in ... more For teloperated unmanned vehicles, mishaps tend to occur during the periods of high workload, in situations where the operator must perform complex and stressful tasks. However, with many tasks performed simultaneously with flying, the relevant information is typically dispersed on a number of screens overloading the operator's visual channel. In order to address these unique human-factors problems associated with unmanned vehicles we suggest the use of an auditory display as a mean to reduce visual workload, to enhance situation awareness, and mitigate the visual and cognitive demands of contemporary marine teleoperations. Experiments were performed on the remotely operated surface marine platform (PlaDyPos) developed at the Laboratory for Underwater Systems and Technologies, Faculty of Electrical Engineering and Computing, University of Zagreb. The results show that the concept, guidance-by-sound is feasible in the real environment. The results are in line with previously obtained results from the real-time simulator showing that tracking quality can be further improved introducing supernormal auditory cues in order to provide better-than-normal operator's auditory resolution in the frontal region. We conclude that the use of hearing in the form of the auditory display emerges as an important advantage. Since practice has a major effect on performance, there is definitely more room for improvement in using interfaces we are not trained for.

Proceedings of the 19th IFAC World Congress, 2014

This paper presents experimental results obtained on an autonomous omnidirectional surface marine... more This paper presents experimental results obtained on an autonomous omnidirectional surface marine platform, developed at the University of Zagreb, during two-week field trials in Murter, Croatia. We focus on results that are a part of the second phase of research on the platform that is intended to be used as a diver tracking platform. This phase includes experimental verification of the control and dynamic positioning (DP) algorithms performed in real environmental conditions, where external disturbances and sensor characteristics have significant influence on the vehicle behaviour. Specifically, we demonstrate 1) experimental results showing successful heading control of the overactuated marine platform even in cases when the platform is performing simultaneous omnidirectional motion; 2) experimental results demonstrating the quality of the DP algorithm performance, and 3) how GPS update frequency influences the quality of DP performance and the quality of the commanded control signal with the navigation filter that uses only GPS measurement and an uncoupled dynamic model of the omnidirectional marine platform.

2012 20th Mediterranean Conference on Control & Automation (MED), 2012

10th IFAC Symposium on Robot Control, 2012

Abstract This paper presents an implementation of the Sigma-point Unscented Kalman Filter (SP-UKF... more Abstract This paper presents an implementation of the Sigma-point Unscented Kalman Filter (SP-UKF) used in the simulated task of open-water navigation of a large cruise-type autonomous underwater vehicle (AUV), the NPS * Aries. Open-water navigation is conducted on the basis of rate gyros, the AHRS ** , which includes accelerometers and a triaxial magnetic compass, and the DVL *** . All sensors function at many times the sampling time of the control loops, and therefore are available (with even the possibility of median or other filtering) at every sample time. Additionally, to correct for unavoidable dead reckoning drift, an inverted USBL **** system is used to sporadically fuse an absolute navigation fix with the projected solution of the dead reckoning navigation. The entire simulation environment includes a detailed dynamical model of the vehicle, non-stationary, non-Gaussian measurement noise generators, sporadic sensor failure and sliding mode controllers for heading, pitch and forward speed.

3rd IFAC Workshop on Navigation, Guidance and Control of Underwater Vehicles, 2012

ABSTRACT Majority of ROVs are underwater vehicles with relatively slow dynamics virtually providi... more ABSTRACT Majority of ROVs are underwater vehicles with relatively slow dynamics virtually providing a ROV pilot extra time to perform other tasks, such as inspections and arm operation. However, with many tasks performed simultaneously with flying the relevant information is typically dispersed on a number of screens overloading the pilot's visual channel. Therefore, mishaps are likely to occur. To improve pilots' perception of its surroundings and to unload their visual channel, a new method called AD AR (Audio Augmented Reality) which combines the concept of Augmented Reality with virtual audio-video user interface, is proposed. In this paper, the feasibility of proposed method used as an aiding tool for navigation is investigated. All experiments are performed on the state-of-the-art, realistic ROV simulator developed by Mobile & Marine Robotics Research Centre, ECE Department, University of Limerick, Ireland.

Journal of Intelligent & Robotic Systems, 2012

Rapid development of underwater technology during the last two decades yielded more affordable se... more Rapid development of underwater technology during the last two decades yielded more affordable sensors and underwater vehicles, and, as a result, expanded their use from exclusively offshore industry towards smaller interdisciplinary research groups. Regardless of application, knowing the location of the vehicle operating underwater is crucial. Relatively inexpensive solution is sensor fusion based on a dynamic model of the vehicle aided by a Doppler Velocity Log and a Ultra-Short Base Line position system. Raw data from the sensors are highly asynchronous and susceptible to outliers, especially in shallow water environment. This paper presents detailed sensor analysis based on experimental data gathered in shallow waters, identifies outliers, presents an intuitive and simple sensor fusion algorithm and finally, discusses outlier rejection. The approach has been experimentally verified on medium size remotely operated vehicle.

Abstract: This paper describes a procedure that utilizes a series of off-line algorithms for pre-... more Abstract: This paper describes a procedure that utilizes a series of off-line algorithms for pre-planning a two-dimensional path for an AUV in a cluttered waterspace. The trajectory is planned as a clothoidal spline or interpolation based on the work of

2018 IEEE 8th International Conference on Underwater System Technology: Theory and Applications (USYS), 2018

Positioning, Navigation and Communication on land would be very difficult and nowadays unimaginab... more Positioning, Navigation and Communication on land would be very difficult and nowadays unimaginable without satellite communication networks. The situation underwater is much more complex due to high attenuation of radio waves. Moreover, due to the different nature of communication above and underwater, facilitation of relevant data flow between these environments requires existence of some kind of communication hub. Idea of replicating concept of positioning/communication satellites able to play both roles simultaneously to set up Internet of Underwater Things (IoUT), is therefore, worth considering. In light of this idea, the University of Zagreb developed a oneman portable autonomous surface vehicle (ASV) with suitable lightweight localization and communication payload. This paper describes an ASV and its role as a satellite for the underwater environment and implementation of IoUT. The paper elaborates three real applications: support to diving operations where a diver tracking ...

2011 Proceedings of the 34th International Convention MIPRO, 2011

Unmanned Underwater vehicles (UUVs) are routinely used for data collection during underwater rese... more Unmanned Underwater vehicles (UUVs) are routinely used for data collection during underwater research missions. UUV operators which perform advanced data collection are usually not qualified for data interpretation. On the fly adaptation of data collection methods based on interpreted data can increase data quality and lower the operator's effort. However, this requires the presence of an expert on site. In order to avoid this, a system of remote monitoring and control over the Internet is proposed. Closing the vehicle control loop over the Internet is problematic due to latency issues, therefore a supervisory control approach is used. This requires only high-level commands to be sent over the Internet while closing the control loop locally. Service oriented architecture (SOA) is used as an API for vehicle monitoring and mission control, while software gadgets are used to display collected data and to send commands for mission adaptation. Gadgets provide support for modifying an...

OCEANS 2017 - Aberdeen

This paper described the basic concept behind the second and final validation trials of the Cogni... more This paper described the basic concept behind the second and final validation trials of the Cognitive Autonomous Diving Buddy (CADDY) system. The CADDY system is composed of three components: autonomous surface vehicle (ASV), an autonomous underwater vehicle (AUV) named BUDDY, and a diver. CADDY aims to establish an innovative setup between a diver and companion autonomous robots (underwater and surface) that exhibit cognitive behaviour by adapting to diver's physical state, and actions, thereby improving overall diving experience by assisting the diver. Although certain problems were encountered during trials, the collected data and experience were valuable to identify potential improvements. Most importantly, divers felt safe and comfortable working and interacting with a robotic BUDDY thus achieving the primary goal.

Sustainability

Documentation and conservation of underwater cultural heritage (UCH) are crucial to preserving hu... more Documentation and conservation of underwater cultural heritage (UCH) are crucial to preserving humankind’s history and traditions, safeguarding tangible testimonies of past human life while ensuring its accessibility to future generations. The TECTONIC (Technological Consortium TO develop sustainability of underwater Cultural Heritage) project is promoting an intersectoral collaboration between academic and non-academic professionals (i.e., archaeologists, conservators, geologists, engineers, etc.) working on different topics related to UCHs, to find solutions to the issues still existing in the field. The overall aim is the exchange of skills for the improvement and assessment of innovative materials and techniques to develop solutions and marketable products for the conservation and management of the UCH, sustainably. To achieve its overall aim, TECTONIC is undertaking activities driven by the following objectives: (a) the study, documentation, and mapping of selected UCHs; (b) th...

Remote Sensing

Underwater cultural heritage sites are subject to constant change, whether due to natural forces ... more Underwater cultural heritage sites are subject to constant change, whether due to natural forces such as sediments, waves, currents or human intervention. Until a few decades ago, the documentation and research of these sites was mostly done manually by diving archaeologists. This paper presents the results of the integration of remote sensing technologies with autonomous marine vehicles in order to make the task of site documentation even faster, more accurate, more efficient and more precisely georeferenced. It includes the integration of multibeam sonar, side scan sonar and various cameras into autonomous surface and underwater vehicles, remotely operated vehicle and unmanned aerial vehicle. In total, case studies for nine underwater cultural heritage sites around the Mediterranean region are presented. Each case study contains a brief archaeological background of the site, the methodology of using autonomous marine vehicles and sensors for their documentation, and the results in...

Remote Sensing

Plitvice Lakes National Park is the largest national park in Croatia and also the oldest from 194... more Plitvice Lakes National Park is the largest national park in Croatia and also the oldest from 1949. It was added to the UNESCO World Natural Heritage List in 1979, due to the unique physicochemical and biological conditions that have led to the creation of 16 named and several smaller unnamed lakes, which are cascading one into the next. Previous scientific research proved that the increased amount of dissolved organic matter (pollution) stops the travertine processes on Plitvice Lakes. Therefore, this complex, dynamic but also fragile geological, biological and hydrological system required a comprehensive limnological survey. Thirteen of the sixteen lakes mentioned above were initially surveyed from the air by an unmanned aircraft equipped with a survey grade GNSS and a full frame high-resolution full-screen camera. From these recordings, a georeferenced, high-resolution orthophoto was generated, on which the following surveys by a multibeam sonar depended. It is important to menti...

IEEE/ASME Transactions on Mechatronics

Water pollution generated by accidental spill of hazardous materials is a growing problem worldwi... more Water pollution generated by accidental spill of hazardous materials is a growing problem worldwide. There is an urging need for a tool which would help environmental response teams to perform rapid understanding of the location and the extent of the spill, to effectively establish an appropriate response. This paper presents a cooperative robotic system for environmental monitoring consisting of an Autonomous Underwater Vehicle (AUV) and an Autonomous Unmanned Surface Vehicle (USV). The main contributions of the paper are: systematic description of the design and implementation of the proposed cooperative robotic system, novel human-on-the-loop (HOTL) approach applied on the system for environmental monitoring and demonstration of the results of the open-sea experiments on pollution deliberately caused by harmless Rhodamine WT, carried out in Cartagena, Spain in June 2015. The proposed HOTL system provides near real-time pollution measurement data, while not consuming a significant amount of human time and effort. It supports decision-making and allows the operator to initiate the most adequate mission in a current situation, i.e., ensures mission change on-the-fly. While the AUV samples the ocean, the USV maintains the localization and communication data transfer to the control centre and corrects the AUV's dead reckoning error.

Applied Acoustics

Abstract The majority of Human–Machine Interfaces (HMIs) designed for the teleoperation of unmann... more Abstract The majority of Human–Machine Interfaces (HMIs) designed for the teleoperation of unmanned vehicles only present information visually. Frequent overloading of the operator’s visual channel may result in accidents. To reduce the occurrence of accidents and improve overall operating performance, this paper proposes the extension of the HMI to the hearing modality. The proposed HMI takes the form of a spatial auditory display for complex navigation tasks such as path following (route guidance) or trajectory tracking. The interface incorporates two novel components. The first is the application of a modified “lookahead distance” guidance strategy, as a guidance law for generating a reference. The reference is presented to the operator as a spatial auditory image of the virtual target to be followed. Before being presented to the operator, the reference information is preconditioned through “supernormal” transformations to increase azimuth and distance resolution in regions of interest and thus to improve efficiency and overcome the comparative disadvantages of the hearing channel. A series of experiments show that the proposed guidance strategy provides a comprehensible and effective auditory reference. The enhanced supernormal auditory interface improves performance by reducing the tracking error of both path following and trajectory tracking compared to a non-enhanced interface without the supernormal transformation. Experiment participants report that the novel auditory interface is intuitive and easy to use, providing very good situational awareness. While the auditory interface investigated in this paper is shown to be effective for the teleoperation of unmanned vehicles, it may have other applications such as navigation for the visually impaired.

Automatika Casopis Za Automatiku Mjerenje Elektroniku Racunarstvo I Komunikacije, Jul 22, 2011

Original scientific paper Currently, one of the most widely used distance measures in speech and ... more Original scientific paper Currently, one of the most widely used distance measures in speech and speaker recognition is the Euclidean distance between mel frequency cepstral coefficients (MFCC). MFCCs are based on filter bank algorithm whose filters are equally spaced on a perceptually motivated mel frequency scale. The value of mel cepstral vector, as well as the properties of the corresponding cepstral distance, are determined by several parameters used in mel cepstral analysis. The aim of this work is to examine compatibility of MFCC measure with human perception for different values of parameters in the analysis. By analysing mel filter bank parameters it is found that filter bank with 24 bands, 220 mels bandwidth and band overlap coefficient equal and higher than one gives optimal spectral distortion (SD) distance measures. For this kind of mel filter bank, the difference between vowels can be recognised for fulllength mel cepstral SD RMS measure higher than 0.4-0.5 dB. Further on, we will show that usage of truncated mel cepstral vector (12 coefficients) is justified for speech recognition, but may be arguable for speaker recognition. We also analysed the impact of aliasing in cepstral domain on cepstral distortion measures. The results showed high correlation of SD distances calculated from aperiodic and periodic mel cepstrum, leading to the conclusion that the impact of aliasing is generally minor. There are rare exceptions where aliasing is present, and these were also analysed.

OCEANS 2015 - Genova, 2015

This paper summarizes the main accomplishments of the first year of the FP7 project “CADDY - Cogn... more This paper summarizes the main accomplishments of the first year of the FP7 project “CADDY - Cognitive Autonomous Diving Buddy”. The main objective of the project is to replace a human buddy diver with an autonomous underwater vehicle and add an autonomous surface vehicle to improve monitoring, assistance, and safety of the diver's mission. While all envisioned objectives of the project are listed, the paper focuses on the results that were obtained in the following areas of research: development of the multicomponent robotic system, “Seeing the Diver” (underwater perception), “Understanding the Diver” (cognition in the form of interpreting diver sign language, behaviour and physiological parameters), and diver-robot cooperation and control.

21st Mediterranean Conference on Control and Automation, 2013

Majority of ROVs are underwater vehicles with relatively slow dynamics virtually providing a ROV ... more Majority of ROVs are underwater vehicles with relatively slow dynamics virtually providing a ROV pilot extra time to perform other tasks, such as inspections and arm operation. However, with many tasks performed simultaneously with flying, the relevant information is typically dispersed on a number of screens overloading the pilot's visual channel. Surprisingly, there is very little research examining the unique human-factors problems associated with unmanned underwater vehicles. Use of audio display has been suggested as a means to reduce visual workload, to enhance situation awareness, and mitigate the visual and cognitive demands of contemporary ROV operations. Our research investigate the effects of secondary visual tasks on operators workload and performance using standard visual navigation interface, augmented reality visual interface and audio interface. All experiments were performed on the state-of-the-art, real-time ROV simulator developed by Mobile & Marine Robotics Research Centre, University of Limerick and augmented reality system developed by Laboratory for Underwater Systems and Technologies, University of Zagreb. As expected, the results show that in no-load conditions visual guidance is better than the guidanceby-sound. By contrast, the effects of secondary visual load affect operators' performance. The use of augmented reality paradigm and especially hearing, in the form of the auditory display, emerges as an important advantage. Improvement depends on a level of experience in using auditory guidance system. Practice has a major effect on performance, bringing us to the conclusion that there is a more room for improvement in using auditory interface.

Lecture Notes in Computer Science, 2013

Research related to diver safety, navigation and monitoring has been identified as crucial for ad... more Research related to diver safety, navigation and monitoring has been identified as crucial for advancing diving activities. These issues are usually dealt with by pairing up divers and adopting well defined rules for diving operations to reduce the chance of accidents. However, during more challenging dives (such as technical dives) these procedures may not be sufficient to ensure almost accident-free operations, for the divers must manoeuvre in complex 3D environments, carry cumbersome equipment, and focus attention on operational details. In this work it is stated that research and technological development in the area of cognitive robotics can significantly contribute to the effectiveness and safety of diving operations. The current research performed in LABUST is based on an autonomous surface platform for following divers and transmitting GPS signal to the underwater. Future envisioned applications include the development of a cognitive autonomous diving buddy consisting of both the surface platform and an underwater vehicle that will serve as diving "guide", "slave" and "observer".

Proceedings of the 19th IFAC World Congress, 2014

For teloperated unmanned vehicles, mishaps tend to occur during the periods of high workload, in ... more For teloperated unmanned vehicles, mishaps tend to occur during the periods of high workload, in situations where the operator must perform complex and stressful tasks. However, with many tasks performed simultaneously with flying, the relevant information is typically dispersed on a number of screens overloading the operator's visual channel. In order to address these unique human-factors problems associated with unmanned vehicles we suggest the use of an auditory display as a mean to reduce visual workload, to enhance situation awareness, and mitigate the visual and cognitive demands of contemporary marine teleoperations. Experiments were performed on the remotely operated surface marine platform (PlaDyPos) developed at the Laboratory for Underwater Systems and Technologies, Faculty of Electrical Engineering and Computing, University of Zagreb. The results show that the concept, guidance-by-sound is feasible in the real environment. The results are in line with previously obtained results from the real-time simulator showing that tracking quality can be further improved introducing supernormal auditory cues in order to provide better-than-normal operator's auditory resolution in the frontal region. We conclude that the use of hearing in the form of the auditory display emerges as an important advantage. Since practice has a major effect on performance, there is definitely more room for improvement in using interfaces we are not trained for.

Proceedings of the 19th IFAC World Congress, 2014

This paper presents experimental results obtained on an autonomous omnidirectional surface marine... more This paper presents experimental results obtained on an autonomous omnidirectional surface marine platform, developed at the University of Zagreb, during two-week field trials in Murter, Croatia. We focus on results that are a part of the second phase of research on the platform that is intended to be used as a diver tracking platform. This phase includes experimental verification of the control and dynamic positioning (DP) algorithms performed in real environmental conditions, where external disturbances and sensor characteristics have significant influence on the vehicle behaviour. Specifically, we demonstrate 1) experimental results showing successful heading control of the overactuated marine platform even in cases when the platform is performing simultaneous omnidirectional motion; 2) experimental results demonstrating the quality of the DP algorithm performance, and 3) how GPS update frequency influences the quality of DP performance and the quality of the commanded control signal with the navigation filter that uses only GPS measurement and an uncoupled dynamic model of the omnidirectional marine platform.

2012 20th Mediterranean Conference on Control & Automation (MED), 2012

10th IFAC Symposium on Robot Control, 2012

Abstract This paper presents an implementation of the Sigma-point Unscented Kalman Filter (SP-UKF... more Abstract This paper presents an implementation of the Sigma-point Unscented Kalman Filter (SP-UKF) used in the simulated task of open-water navigation of a large cruise-type autonomous underwater vehicle (AUV), the NPS * Aries. Open-water navigation is conducted on the basis of rate gyros, the AHRS ** , which includes accelerometers and a triaxial magnetic compass, and the DVL *** . All sensors function at many times the sampling time of the control loops, and therefore are available (with even the possibility of median or other filtering) at every sample time. Additionally, to correct for unavoidable dead reckoning drift, an inverted USBL **** system is used to sporadically fuse an absolute navigation fix with the projected solution of the dead reckoning navigation. The entire simulation environment includes a detailed dynamical model of the vehicle, non-stationary, non-Gaussian measurement noise generators, sporadic sensor failure and sliding mode controllers for heading, pitch and forward speed.

3rd IFAC Workshop on Navigation, Guidance and Control of Underwater Vehicles, 2012

ABSTRACT Majority of ROVs are underwater vehicles with relatively slow dynamics virtually providi... more ABSTRACT Majority of ROVs are underwater vehicles with relatively slow dynamics virtually providing a ROV pilot extra time to perform other tasks, such as inspections and arm operation. However, with many tasks performed simultaneously with flying the relevant information is typically dispersed on a number of screens overloading the pilot's visual channel. Therefore, mishaps are likely to occur. To improve pilots' perception of its surroundings and to unload their visual channel, a new method called AD AR (Audio Augmented Reality) which combines the concept of Augmented Reality with virtual audio-video user interface, is proposed. In this paper, the feasibility of proposed method used as an aiding tool for navigation is investigated. All experiments are performed on the state-of-the-art, realistic ROV simulator developed by Mobile & Marine Robotics Research Centre, ECE Department, University of Limerick, Ireland.

Journal of Intelligent & Robotic Systems, 2012

Rapid development of underwater technology during the last two decades yielded more affordable se... more Rapid development of underwater technology during the last two decades yielded more affordable sensors and underwater vehicles, and, as a result, expanded their use from exclusively offshore industry towards smaller interdisciplinary research groups. Regardless of application, knowing the location of the vehicle operating underwater is crucial. Relatively inexpensive solution is sensor fusion based on a dynamic model of the vehicle aided by a Doppler Velocity Log and a Ultra-Short Base Line position system. Raw data from the sensors are highly asynchronous and susceptible to outliers, especially in shallow water environment. This paper presents detailed sensor analysis based on experimental data gathered in shallow waters, identifies outliers, presents an intuitive and simple sensor fusion algorithm and finally, discusses outlier rejection. The approach has been experimentally verified on medium size remotely operated vehicle.