An Integration of Contact Force Models with Multibody Dynamics Analyses for Human Joint Mechanisms and Effects of Viscoelastic Ground Contact

In human movement and rehabilitation analyses, human joint dynamics is a key to consider the incorporation of spring-damper components, flexible bodies and contact forces analytically. In the present study, an analytical method for human gaits were introduced to integrate those essential elements, and viscoelastic properties of musculoskeletal system were modeled with the absolute nodal coordination formula (ANCF) method representing flexible body motions. A contact force model simulates interactions between different body segments and the environment. The proposed system is applied to a slider crank mechanism, demonstrating its capabilities in human joint motion analysis using integrated dynamic model within the framework of multi body dynamics (MBD), which realizes dynamic/inverse dynamics for human biomechanics. © The 2024 International Conference on Artificial Life and Robotics.The 2024 International Conference on Artificial Life and Robotics (ICAROB 2024), February 22-25, 2024, on line, Oita, Japanconference pape

A Comparative Analysis of Serial and Parallel Models in the Morphological Component Analysis-Based Structure Pattern Extraction for Aerial Image Edge Detections

A refinement process by human experts is still needed for areas/feature extractions of interest from aerial images in multiple map makers. The construction/road edge extraction is one of them which is highly important in the preprocessing stage for map-making, while it is difficult to isolate man-made structures from a natural landscape involving different size objects. In the present study, we focused on an actual procedure in the decomposition of the Morphological Component Analysis known as MCA to extract specific patterns as serial and parallel models. In our computer experiments, dictionaries of Curvelet and Local Discrete Cosine Transform known as LDCT were introduced for the MCA decomposition and then two models demonstrated a non-negligible difference in the feature extraction performance. This result may contribute to the extension of future possibilities of structural data analyses especially for buildings and roads from shapes in nature.journal articl

A MBD-Based Dynamic Analysis Framework with a Viscoelastic Contact Model and Flexible Elements Toward Human Power Assistive Devices

It is important for the analysis of human movement and rehabilitation to incorporate spring-damper components, flexible materials, and contact force into the joint model considering human dynamics. In this study, the absolute nodal coordination formula (ANCF) method is introduced to the analytical model for the viscoelastic properties of the musculoskeletal system which is essential for analyzing human walking motion, and the flexible characteristics of the human body is reproduced. The consideration of a contact force model makes it possible to simulate contact actions between elements of the human body and the interaction with the environment. The proposed integrated framework is applied to multibody dynamics (MBD) based slider-crank mechanisms to demonstrate the dynamics/inverse dynamics analysis of human joint biomechanics.journal articl

A Validation Analysis of the Submillimeter-Width Concrete Crack Detection Based on Morphological Component Analysis and Anisotropic Diffusion

Abnormality detection in an early stage is a crucial issue to maintain social concrete infrastructures. The submillimeter-width concrete crack detection is the inevitable mission to significantly reduce the human burden; however, conventional image processing methods do not reach the same level of human inspections in senses of coverage ratios and hit rates. In the present study, we hypothesized that a concrete crack detection based on the morphological component analysis (MCA) can be upgraded with after-treatments for contrast enhancements by using anisotropic diffusion and related techniques, to be able to detect cracks on images even for less than 10 pixels in width as a submillimeter range. The traditional MCA method was modified to decompose the image into its coarse and fine components and the coefficient of anisotropic diffusion was designed to find cracks in high gradient and low gray level regions. The modified MCA and anisotropic diffusion with the Sobel edge detector were embedded to a consistent workflow to detect submillimeter cracks in image. In the accuracy verification, comparisons among the proposed method, conventional methods and the human detection demonstrated that the proposed method had a noteworthy detection efficiency with high coverage ratios and hit rates over 60% in total. It can contribute to the actual field work of the concrete crack detection.journal articl

Determining the Elastic Properties of Flexible 3D Printed Beams with Variable Infill Densities and Patterns

Flexible non-linear 3D printed materials are rapidly gaining popularity in various engineering applications such as soft robotics, actuators, medical devices, etc. Due to their wide applicability, there is an increased research interest in characterization of their mechanical properties and performance. Unlike the conventional manufacturing processes, 3D printing has an additive character and allows for the geometry to be controlled from inside. The internal geometry and density corresponding to a given model can be tuned to a desired stiffness. In this study we investigate the effect of the infill percentage and infill geometry on the mechanical properties of 3D printed samples from flexible material by using a desktop type FDM 3D printer. The analyzed samples have the same shape and geometry – a beam with a square cross-section but the infill percentage is varied from 10 % to a 100 % with an increment of 15 %. The effects of three different types of infill geometries– rectangular, square and honeycomb have also been analytically determined. The approach for the analytical formulation adopts the methodology for calculating the in-plane properties and stiffnesses in cellular solids. The results for the mechanical properties for the different infill densities and infill geometries have been compared for all configurations. Despite the common external geometry of all beams, there is a significant change in their stiffness with the variation of the infill patterns and densities. Finally, a non-linear FEA study for the fully solid beam was conducted and compared with the analytical results. The method, used in this study can be applied for optimization of the stiffness to weight ratio during the design process of flexible 3D printed parts undergoing larger deformations.journal articl

A Linear-Time Algorithm to Form a Core Convex Shape from an Arbitrary Non-Convex for Automated Fulfillment in Robotic Manipulation Tasks

In the field of robotic manipulation, a fully automatic object fulfillment is an important issue in applications not only for high-density warehouse optimization but also for agricultural automation. In the present study, a formulation of the fulfillment of the maximum object into a given non-convex area was proposed. For minimizing redundant space inside a container during a packing task, the optimization problem is inevitable. Even edges of the target area are clearly detected, the best scenario to fill candidate objects sequentially is not apparently calculated. To deal with this problem, the proposed method is composed of two processes as decomposition of the original non-convex shape and reconstruction of a convex shape, based on theories of computational geometry. For example, it is difficult to judge a point either inside or outside of the area if it is non-convex, while it is easy to judge if the area is convex in the sense of the theorem of computational geometry. The proposed method is initiated by a recursive procedure proposed to decompose non-convex parts until it forms a remaining part to be a convex shape, and then it shifts to the reconstruction of a developing convex shape by adding decomposed parts in the first process, which it will be convex with the maximum size to be a subset of the original non-convex shape. It finally provides the right answer to be a filling area for candidate objects. Since the decomposition and reconstruction will be done in the circulation of removal and attachment of decomposed triangle parts, which takes computational costs of N (the number of nodes) steps as maximum in rotation as a linear-time algorithm. Theoretically, a simple detection algorithm of the maximum fulfillment area can be derived from an arbitrary combination of nodes as 2N. In the computer experiment, the reduction of the computational cost was clearly demonstrated in the comparison of the proposed method and the combinatory method. It contributes to the enhancement of the potential of computational geometry in an effective design of optimization units for robotics working in unstable and dynamic environments.journal articl

An Analytical Method for Human Gait Analysis and Exoskeletal Design Optimization Using Flexible Multibody Dynamics with ANCF

Understanding human joint dynamics is paramount in order to apply this understanding of how muscles regulate human movement and gait to rehabilitation. Coupling with spring-damper components, flexible bodies, and contact forces analytically improves the reliability of biomechanical models. Our research presents step-by-step analytics that integrate human criticality. The Absolute Nodal Coordinate Formulation (ANCF) is precisely designed to express the viscoelasticity and flexible movement of the human body. In addition, the contact force model simulates the contact between different body segments. Our research method is used in Multibody Dynamics (MBD) human joint motion analysis and application to the sliding crank mechanism. Flexible Multibody Dynamic (fMBD) with ANCF aims to support exoskeleton performance through nonlinear viscoelastic force analysis of Carbon Fiber Reinforced Plastic (CFRP) joint in humans. Our real experimental result showed that the compressive force value increases to 1.4-newton force value as maximum value as the reference value for the computer simulation.journal articl

A Comparative Study of Vector and Raster Spatial Data for Image Segmentation Focusing on the Position Estimation Accuracy of Vertices to Form Polygonal Shapes

In the field of image processing, raster data is frequently used for image segmentation and shape estimations for general purposes. On the other hand, in the medical field, which aims to help doctors in surgical operations, semi-automatic robotic manipulations such as the da Vinci Surgical Systemto minimize the necessary area to open for the living body. In the present study, a computational geometry-based method was proposed for vector data to treat the rearrangement of extracted points as candidates for edges of the target shape. On the other hand, the Harris-Stephens algorithm was introduced as a well-known method to detect vertices to form polygonal shapes in raster data as the counterpart in the comparative study. Typically, such a raster data method is not robust to perform in noisy conditions without appropriate filtering in the pre-processing. In the Harris-Stephens algorithm, the adding noises were detected as new vertices to form shapes in the area, which is inevitable in the condition without any semantic information about the shape. Since the proposed computational geometry-based method contains geometrical properties in its computation, it can be enhanced to be robust against noisy data. In the sense of designing a part of the system to be a surgical robot, which requires high accuracy of the position estimation of the target, a maximization of extractions of geometrical properties provides a significant benefit for accurate manipulation of robotic arms. It contributes not only to surgical robots but also to the solver of 2D replacement puzzles known as tangram puzzles to be a general scheme for robots in all fields behaving in dynamic environments.journal articl

An Adaptive Control Method for a Knee-Joint Prosthetic Leg Toward Dynamic Stability and Gait Optimization

This paper presents a hybrid control strategy that combines Model Predictive Control (MPC) and Linear Quadratic Regulator (LQR) to achieve robust and stable tracking of human knee joint motion. The state-space model of the system is discretized to facilitate real-time implementation. MPC is employed to track the knee joint trajectory during dynamic motion, while the LQR controller is activated at critical points, particularly when the joint angle approaches zero, to stabilize the system and ensure safety.conference pape

Analyzing Eye-Tracking Data to Detect Joint Attention in Hexgame Experiments

This study aims to explore the mechanisms of joint attention in a strategic game experiment by analyzing Tobii eyetracking data. In this experiment, two participants play Hexgame, during which the gaze direction is tracked and projected onto the game's board plane through perspective geometry, in order to track attention sharing correlates at particular stages of the game from behavioral data. The primary focus of this study is the analysis of eye-tracking data to identify attention coordination between players during the progression of the game. Future work will expand this framework to assess win probabilities and predict subsequent moves, providing deeper insights into strategic decisionmaking.conference pape