Visualizing human fatigue at joint level with the half-joint pair concept

We present a model to predict and represent human fatigue in a 3D interactive system. A fatigue model has been developed for the fatigue assessment of several joints of the human body within the static case hypothesis. The model incorporates normalized torques, joint strength and maximum holding time as parameters. Fatigue evolution is predicted taking into account how these variables evolve over time. The fatigue model is embedded within an Inverse Kinematics engine that tries to achieve user-defined goals. During the animation, the predicted fatigue level is given to the graphical system in order to visualize it around its associated joint. The current fatigue value is exploited by the fatigue model to perform a new iteration towards the goal. The traditional joint model is broken down into two half-joints that better represents the anatomic organization of motion production through two independent muscle groups. Based on this organization, we can calculate and visualize independent fatigue variables for each antagonist muscle group. This type of visualization gives an intuitive and clear feedback. Each half-joint maintains its own fatigue model and variable. The two fatigue variables are represented by means of dynamic semicircles. Visual guides as semicircle's length and gradual color indicates fatigue evolution along tim

A Model to Assess Fatigue at Joint-Level Using the Half-Joint Concept

this paper we focus on the modeling and evaluation of performance factors as human fatigue at joint level. We introduce the concept of half-joint pair to calculate fatigue at joint level, that is, at muscle groups level. The fatigue model is designed to enable to a posture optimization algorithm to adapt the human posture so that when fatigue appears it can be reduced. An Inverse Kinematics solver gets values of joints fatigue and evaluates whether it is necessary to minimize fatigue values. We use an activation/deactivation pattern for each half-joint to set/unset a fatigue reduction constraint when fatigue value reaches an established threshold. We make a comparison between experiments performed using several male and female and simulations generated by our animation environmen

Reaching volumes generated by means of octal trees and Cartesian constraints

We present a system to analyze the reachability of the human body. The inverse kinematics technique is employed to find which regions of space are reachable using a certain reach strategy. This information is stored in a data structure called volume approximation tree (VATree). This tree has proven itself to be an appropriate data structure for two reasons: it provides an efficient representation of the reachable volumes and it reduces the number of inverse kinematics simulations necessary for its construction. Once the VATrees are constructed for the different reach strategies, that information can be used to determine in real time which strategy is most suitable for a given reach tas

Approximating Human Reaching Volumes Using Inverse Kinematics

This paper presents a system to analyse the reaching capabilities of the human body. Our research is motivated by the need for a system which helps the user to manage data relative to the most frequent tasks involved in human activity: reaching tasks. Depending on the type of reaching that we are dealing with we establish a set of constraints that characterise the reaching task. We have designed a data structure that let us approximate reachable volumes. A set of reaching strategies is defined, and reachable volumes are generated and stored for each of these strategies. In addition, an automatic strategyselection process decides, in real time, which strategy is the most suitable for a certain reaching task. To demonstrate the usefulness of our system, we show how it can be applied to a study of seated reaching

Bringing the Human Arm Reachable Space to a Virtual Environment For its Analysis

Human reaching in a 3D environment is an interesting matter of research due to its application to workplace or vehicle-interior design. We introduce a 3D environment where a virtual human performs reaching tasks over 3D objects in the world. This environment also provides tools to generate and visualize reachable volumes. Reachable spaces are approximated using adjacent box-shaped voxels. We define several strategies in order to model different types of reaching, and we employ our system to construct and analyze reachable spaces for these strategies. In general, different strategies will have reachable spaces that share a common region of intersection. Therefore, goals will exist that can be reached using two or more strategies. For those goals, a high-level layer is responsible for selecting the most appropriate given a certain reaching task. As a practical application, this paper presents a comparison of two usual strategies to model standing and seated reaching. The generated reach spaces show that, for each of them, a strategy is clearly more adequate than the other

Bringing the human arm reachable space to a virtual environment for its analysis

Human reaching in a 3D environment is an interesting matter of research due to its application to workplace or vehicle-interior design. We introduce a 3D environment where a virtual human performs reaching tasks over 3D objects in the world. This environment also provides tools to generate and visualize reachable volumes. Reachable spaces are approximated using adjacent box-shaped voxels. We define several strategies in order to model different types of reaching, and we employ our system to construct and analyze reachable spaces for these strategies. In general, different strategies do have reachable spaces that share a common region of intersection. Therefore, goals exists that can be reached using two or more strategies. For those goals, a high-level layer is responsible for selecting the most appropriate given a certain reaching task. As a practical application, this paper presents a comparison of two usual strategies to model standing and seated reaching. The generated reach spaces show that, for each of them, a strategy is clearly more adequate than the othe