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Proceedings ArticleDOI

Fiducial Marker Approach for Biomechanical Smartphone-Based Measurements

TL;DR: This research reviewed and evaluated various fiducial marker systems by developing an Android mobile application for real-time biomechanical measurement and selected AprilTag2 as the best fiducIAL marker option for this application.
Abstract: Marker-based measurement has been used to assess human body positioning, but human marker tracking has yet to make the transition from the laboratory to personal computing devices, such as smartphones. A novel smartphone-based approach could use a fiducial marker system. Fiducial markers are applicable to augmented reality, robotics, and other applications where a camera-object pose is required and tracked. However, few fiducial systems can be implemented on a mobile phone because of the processing requirements for identifying and tracking the tags in realtime. In augmented reality, virtual information is shared with the real world to further enhance a person’s view of the environment; therefore, this illusion is directly associated with good registration of both virtual and real worlds. Measurement applications also require accurate and fast registration so that real objects are in alignment with virtual objects in real-time. Our research reviewed and evaluated various fiducial marker systems by developing an Android mobile application for real-time biomechanical measurement. A test was designed for two nominated fiducial systems to compare their speed and robustness on the mobile phone. AprilTag2 was selected as the best fiducial marker option for this application.
Citations
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Proceedings ArticleDOI
01 Jul 2020
TL;DR: A novel Android smartphone augmented-reality-based application was developed using the AprilTag2 fiducial marker system and obtained valid and reliable angle and distance measurements with smartphone positions and cameras that would be expected in practice.
Abstract: Marker tracking for postural and range of motion (ROM) measurements transcends multiple disciplines (e.g., healthcare, ergonomics, engineering). A viable real-time mobile application is currently lacking for measuring limb angles and body posture. To address this need, a novel Android smartphone augmented-reality-based application was developed using the AprilTag2 fiducial marker system. To evaluate the app, two markers were printed on paper and attached to a wall. A Samsung S6 mobile phone was fixed on a tripod, parallel to the wall. The smartphone app tracked and recorded marker orientation and 2D position data in the camera frame, from front and rear cameras, for different smartphone placements. The average error between mobile phone and measured angles was less than 1 degree for all test settings (back camera=0.29°, front camera=0.33°, yaw rotation=0.75°, tilt rotation=0.22°). The average error between mobile phone and measured distance was less than 4 mm for all test settings (back camera=1.8 mm, front camera=2.5 mm, yaw rotation=3 mm, tilt rotation=3.8 mm). Overall, the app obtained valid and reliable angle and distance measurements with smartphone positions and cameras that would be expected in practice. Thus, this app is viable for clinical ROM and posture assessments.

7 citations


Cites background from "Fiducial Marker Approach for Biomec..."

  • ...Fiducial systems are viable for mobile posture and ROM measurement since the computational cost is low with high accuracy [13], and fiducial markers will be more easily recognizable than colour or light-based markers....

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Journal ArticleDOI
28 May 2022-BioMed
TL;DR: A novel Android smartphone augmented-reality-based application was developed and evaluated to enable real-time AprilTag2 marker measurement at the point of patient contact and obtained valid and reliable angle measurements for postural and ROM assessments using the smartphone’s front camera.
Abstract: Human posture and range of motion (ROM) measurements are important health indicators for identifying abnormalities from various disorders (e.g., scoliosis, musculoskeletal disorders, pain syndromes). A viable real-time mobile application for measuring body posture and ROM is currently lacking. To address this need, a novel Android smartphone augmented-reality-based application was developed and evaluated to enable real-time AprilTag2 marker measurement at the point of patient contact (Biomechanical Augmented Reality-Marker, BAR-M). Mobile app performance was evaluated on a body opponent bag (BOB) and 15 healthy participants by comparing smartphone app and Vicon motion analysis output (pelvis, shoulder, arm, torso angles). A Samsung Galaxy smartphone recorded live video, calculated AprilTag orientations and angle of “a line connecting the center of two tags”, and displayed outcomes in real time. For the BOB test, the absolute difference between Vicon and smartphone angles were 0.09° ± 0.05° for hip, 0.09° ± 0.06° for shoulder, and 0.69° for arm abduction. For the participant test, the absolute mean angle differences were 1.70° ± 0.23° for hip, 1.34° ± 0.27° for shoulder, and 11.18° ± 3.68° for arm abduction. Overall, the app obtained valid and reliable angle measurements for postural and ROM assessments using the smartphone’s front camera. Arm abduction results were affected by clothing movement that caused Vicon markers to move differently from AprilTag markers. Thus, with appropriate measurement methods, this real-time smartphone app is a viable tool to facilitate immediate clinical decision making based on human posture and ROM assessments.

3 citations

Proceedings ArticleDOI
01 Oct 2019
TL;DR: The experimental results show that the navigation accuracy of the proposed system with AprilTags2 auxiliary positioning is significantly improved, and the system uses the Robot Operating System (ROS) as a platform to develop AGV navigation functions.
Abstract: Aiming at the problems of poor flexibility, complicated path maintenance and poor positioning performance in the current guidance technology of AGV, this paper designs and implements a new navigation system of automated guided vehicle (AGV) based on AprilTags2 auxiliary positioning. The system uses the Robot Operating System (ROS) as a platform to develop AGV navigation functions. The navigation system comprises two parts: the hardware and software layers. Firstly, hardware selection is performed after considering the actual requirements, performance, cost, and other factors in the hardware layer. Simultaneously, the AGV chassis and single-steering wheel walking mechanism are built to provide a stable and flexible operating platform for the software layer. Secondly, the software layer design includes two parts, namely the ROS navigation planning end and AprilTags2 detection. The ROS planning navigation end performs the design of four functional modules (i.e., AGV map construction, autonomous positioning, path planning, and path tracking), while the AprilTags2 detection part obtains the visual positioning pose of AGV by setting the AprilTags2 on each site and using the Kinect1 camera to detect. A more accurate AGV pose can be obtained by merging the former pose with the kinematic estimated pose. Finally, the two groups of positioning errors of the system before and after adding the AprilTags2 auxiliary positioning are tested and compared. The experimental results show that the navigation accuracy of the proposed system with AprilTags2 auxiliary positioning is significantly improved.

1 citations

Proceedings ArticleDOI
01 Nov 2019
TL;DR: A new picture-based localization service PicPose is presented that relies on the feature points extracted from a camera-captured image and conducts feature point matching with the original wall picture to conduct pose calculation, which is impossible for ArPico and ArUco.
Abstract: Device self-localization is an important capability for many IoT applications that require mobility in service capabilities. In our previous work, we have designed the ArPico method for robot indoor localization. By placing and recognizing pre-installed pictures on walls, robots can use low-cost cameras to identify their positions by referencing to pictures' precise locations. However, using ArPico, all pictures need to have clear rectangular borders for the pose computation. But some real-world pictures does not have clear thick borders. Moreover, some pictures may have odd shapes or are only partially visible. To address these problems, a new picture-based localization service PicPose is presented. PicPose relies on the feature points extracted from a camera-captured image and conducts feature point matching with the original wall picture to conduct pose calculation. Using PicPose, even partially visible pictures can be used for localization, which is impossible for ArPico and ArUco. We present our implementation and experiment results in this paper.

1 citations

Journal ArticleDOI
TL;DR: An autonomous moving robot that can self-localize itself using its on-board camera and the PicPose technology is built and shows that the localization methods are practical, have very good accuracy, and can be used for real time robot navigation.
Abstract: Localization is an important technology for smart services like autonomous surveillance, disinfection or delivery robots in future distributed indoor IoT applications. Visual-based localization (VBL) is a promising self-localization approach that identifies a robot’s location in an indoor or underground 3D space by using its camera to scan and match the robot’s surrounding objects and scenes. In this study, we present a pictorial planar surface based 3D object localization framework. We have designed two object detection methods for localization, ArPico and PicPose. ArPico detects and recognizes framed pictures by converting them into binary marker codes for matching with known codes in the library. It then uses the corner points on a picture’s border to identify the camera’s pose in the 3D space. PicPose detects the pictorial planar surface of an object in a camera view and produces the pose output by matching the feature points in the view with that in the original picture and producing the homography to map the object’s actual location in the 3D real world map. We have built an autonomous moving robot that can self-localize itself using its on-board camera and the PicPose technology. The experiment study shows that our localization methods are practical, have very good accuracy, and can be used for real time robot navigation.

1 citations

References
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Journal ArticleDOI
TL;DR: The author was led to the study given in this paper from a consideration of large scale computing machines in which a large number of operations must be performed without a single error in the end result.
Abstract: The author was led to the study given in this paper from a consideration of large scale computing machines in which a large number of operations must be performed without a single error in the end result. This problem of “doing things right” on a large scale is not essentially new; in a telephone central office, for example, a very large number of operations are performed while the errors leading to wrong numbers are kept well under control, though they have not been completely eliminated. This has been achieved, in part, through the use of self-checking circuits. The occasional failure that escapes routine checking is still detected by the customer and will, if it persists, result in customer complaint, while if it is transient it will produce only occasional wrong numbers. At the same time the rest of the central office functions satisfactorily. In a digital computer, on the other hand, a single failure usually means the complete failure, in the sense that if it is detected no more computing can be done until the failure is located and corrected, while if it escapes detection then it invalidates all subsequent operations of the machine. Put in other words, in a telephone central office there are a number of parallel paths which are more or less independent of each other; in a digital machine there is usually a single long path which passes through the same piece of equipment many, many times before the answer is obtained.

5,408 citations


"Fiducial Marker Approach for Biomec..." refers background in this paper

  • ...The 2D planar marker system includes planar patterns and computer vision algorithms to identify markers in a given image [8,9]....

    [...]

Proceedings ArticleDOI
20 Oct 1999
TL;DR: An augmented reality conferencing system which uses the overlay of virtual images on the real world using fast and accurate computer vision techniques and head mounted display (HMD) calibration is described.
Abstract: We describe an augmented reality conferencing system which uses the overlay of virtual images on the real world. Remote collaborators are represented on virtual monitors which can be freely positioned about a user in space. Users can collaboratively view and interact with virtual objects using a shared virtual whiteboard. This is possible through precise virtual image registration using fast and accurate computer vision techniques and head mounted display (HMD) calibration. We propose a method for tracking fiducial markers and a calibration method for optical see-through HMD based on the marker tracking.

2,496 citations


"Fiducial Marker Approach for Biomec..." refers background in this paper

  • ...The 2D planar marker system includes planar patterns and computer vision algorithms to identify markers in a given image [8,9]....

    [...]

Proceedings ArticleDOI
09 May 2011
TL;DR: This work describes a new visual fiducial system that uses a 2D bar code style “tag”, allowing full 6 DOF localization of features from a single image, incorporating a fast and robust line detection system, a stronger digital coding system, and greater robustness to occlusion, warping, and lens distortion.
Abstract: While the use of naturally-occurring features is a central focus of machine perception, artificial features (fiducials) play an important role in creating controllable experiments, ground truthing, and in simplifying the development of systems where perception is not the central objective. We describe a new visual fiducial system that uses a 2D bar code style “tag”, allowing full 6 DOF localization of features from a single image. Our system improves upon previous systems, incorporating a fast and robust line detection system, a stronger digital coding system, and greater robustness to occlusion, warping, and lens distortion. While similar in concept to the ARTag system, our method is fully open and the algorithms are documented in detail.

1,334 citations


"Fiducial Marker Approach for Biomec..." refers background or methods in this paper

  • ...Olson claimed that AprilTags are resilient against false positive only in natural environments [10]....

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  • ...AprilTag calculates a specific identity, orientation, and position of a marker relative to the camera [10,18,19]....

    [...]

  • ...Additional findings demonstrated that the tags’ lexicodebased generation process reduces false positive rates without hindering location accuracy [10,19]....

    [...]

  • ...Based on earlier fiducial markers such as ARToolkit and ARTag, Edwin Olson developed a new system called AprilTags, a black and white square tag encoded with a binary payload [10]....

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  • ...Unlike other marker systems, AprilTag2 encodes only 4-36 bits of data, thus enabling accurate and quick tag detection [10]....

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Proceedings ArticleDOI
20 Jun 2005
TL;DR: This proposed new marker system, ARTag has very low and numerically quantifiable error rates, does not require a grey scale threshold as does other marker systems, and can encode up to 2002 different unique ID's with no need to store patterns.
Abstract: Fiducial marker systems consist of patterns that are mounted in the environment and automatically detected in digital camera images using an accompanying detection algorithm. They are useful for augmented reality (AR), robot navigation, and general applications where the relative pose between a camera and object is required. Important parameters for such marker systems is their false detection rate (false positive rate), their inter-marker confusion rate, minimal detection size (in pixels) and immunity to lighting variation. ARTag is a marker system that uses digital coding theory to get a very low false positive and inter-marker confusion rate with a small required marker size, employing an edge linking method to give robust lighting variation immunity. ARTag markers are bi-tonal planar patterns containing a unique ID number encoded with robust digital techniques of checksums and forward error correction (FEC). This proposed new system, ARTag has very low and numerically quantifiable error rates, does not require a grey scale threshold as does other marker systems, and can encode up to 2002 different unique ID's with no need to store patterns. Experimental results are shown validating this system.

909 citations


"Fiducial Marker Approach for Biomec..." refers background or methods in this paper

  • ...Other evaluation metrics include minimal marker size for reliable detection, detection jitter, and immunity to lighting [1,2]....

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  • ...Of these metrics, the false negative rate is deemed the least serious since a fiducial marker is present within the image yet never reported [1]....

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  • ...Inter-marker confusion rate occurs when a fiducial marker is detected yet incorrectly identified [1]....

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  • ...ARToolKit was initially used in scientific and industrial research [1,6,7]....

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  • ...One method (ARToolKit) uses arbitrary image patterns embedded inside a square, which are matched to a database of known patterns for identification [1,3]....

    [...]

Proceedings ArticleDOI
01 Oct 2016
TL;DR: This work describes AprilTag 2, a completely redesigned tag detector that improves robustness and efficiency compared to the original AprilTag system, and improves performance with higher detection rates, fewer false positives, and lower computational time.
Abstract: AprilTags and other passive fiducial markers require specialized algorithms to detect markers among other features in a natural scene. The vision processing steps generally dominate the computation time of a tag detection pipeline, so even small improvements in marker detection can translate to a faster tag detection system. We incorporated lessons learned from implementing and supporting the AprilTag system into this improved system. This work describes AprilTag 2, a completely redesigned tag detector that improves robustness and efficiency compared to the original AprilTag system. The tag coding scheme is unchanged, retaining the same robustness to false positives inherent to the coding system. The new detector improves performance with higher detection rates, fewer false positives, and lower computational time. Improved performance on small images allows the use of decimated input images, resulting in dramatic gains in detection speed.

543 citations


"Fiducial Marker Approach for Biomec..." refers background in this paper

  • ...AprilTag calculates a specific identity, orientation, and position of a marker relative to the camera [10,18,19]....

    [...]

  • ...AprilTag 2 remained robust to false positives [19,20]....

    [...]

  • ...Additional findings demonstrated that the tags’ lexicodebased generation process reduces false positive rates without hindering location accuracy [10,19]....

    [...]