Posturing for Autonomous Digital Human Model
Selvan, Eazhil K
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Digital Human Models (DHMs) are representations of humans in virtual environments that have applications in diverse disciplines. In the context of engineering design, DHMs are used to assess if a proposed design satisfies ergonomics requirements. This is done by inserting a DHM into the CAD environment and making it interact with the virtual prototype of the system being designed. The main challenge in this process is the difficulty in controlling the DHM for simulating the interaction. The DHM systems that are currently in use have low autonomy, meaning controlling the DHM requires the designer to spend significant amounts of time and effort, as well as possess considerable expertise in the domain. This thesis endeavours to enhance the autonomy of DHM systems, so that task simulations can be performed quickly and easily, even by users with less or no expertise. While a full-fledged autonomous DHM system would have numerous components, the current work focuses on the aspect of automating the process of generating postures. This thesis presents a computational framework that takes high-level commands as input and automatically generates physically valid postures and motions of human performing manual tasks. The first part of the thesis focuses on synthesising static postures and the later part builds on the developments of the first part for generating body-motions. Firstly, an optimisation-based computational framework is developed to simulate functional reach postures that account for factors of stability and biomechanical effort. With this framework, simulation of reach postures and generation of reach-envelopes for extreme reach-tasks in various standing postures are demonstrated. The capability to simulate functional reach is then extended to simulation of postures that take supports from the environment. Here, along with the computation of postures, the optimal location for support-contact and reaction forces at the support-contact are also computed through optimisation. In addition to that, a novel support-taking behaviour is introduced, which enables the DHM to automatically choose supporting surfaces that are suitable for the task to be performed. Based on the facility to generate static postures, the problem of simulating posture-transition tasks is then addressed. Posture-transition deals with generation of body-motion connecting the given initial and final postures of the human, placed anywhere in the environment. Here, an approach for automatically generating and composing primitive motions that executes the posture-transition is developed. The posture-transition facility is demonstrated with the simulations of tasks such as walking, stair-climbing and vehicle ingress/egress. After this, tasks involving manipulation of objects are characterised and methods for generating manipulation motions are developed. Finally, the methods to simulate manipulation and posture-transition tasks are combined to develop the capability to simulate long and complex operations in a fully autonomous mode. This unique feature is demonstrated with a simulation of a manual-assembly process. The theories and methods developed in this thesis were implemented in the form of a software application called Maya-Manav. The details of the computer implementation of Maya Manav tool are presented at the end. In summary, this thesis presents a generic and practical posture-generation framework that can be seen as a low-level infrastructure or a platform on which highly autonomous DHM simulation systems can be built.