Amos Patrick

Towards a new generation of virtual humans

This paper presents work from an ongoing project towards developing a new generation of virtual human models that are highly realistic in appearance, movement, and feedback. Santos™, an anatomically correct human model with more than 100 degrees of freedom, is an avatar that exhibits extensive modelling and simulation capabilities, resides in a virtual environment, and conducts human-factors analysis. The paper presents an optimisation-based approach to posture and motion prediction that allows the avatar to operate with autonomy rather than depending on stored animations and data or being restricted by inverse kinematics. It also presents approaches to determining reach envelopes and workspace zone differentiation, and discusses methods for evaluating the physiological status of the virtual human as it completes tasks. Muscle modelling including muscle wrapping, muscle force and stress determination is also discussed. Finally, the process of building a 25-DOF hand model is described. The result is an exciting step towards a virtual human that is more extensive and complete than any other.

A physics-based digital human model

This paper presents a comprehensive human modelling and simulation environment. This environment, called Santos™, is a new generation of digital human simulation systems that allows a user to interact with a digital character with full and accurate biomechanics and a complete muscular system, subject to the laws of physics. Major results in the areas of dynamic motion prediction, advanced posture prediction and comfort level assessment, physiology model, modelling of clothing and muscle wrapping and force assessment will be presented. This paper will feature the various modules that comprise the Santos environment.

Santos: A Physics-Based Digital Human Simulation Environment:

This paper presents a comprehensive human modeling and simulation environment under development by the University of Iowa Virtual Soldier Research (VSR) program. This environment, called SantosTM, is a new generation of digital human simulation systems that allows for a user to interact with a digital character with full and accurate biomechanics and a complete muscular system, subject to the laws of physics. Highlighting major results in the areas of dynamic motion prediction, modeling of clothing, modeling of muscle activation and loading, and the Santos intuitive interface will be presented. This paper will feature the various modules that comprise the Santos environment.

Efficient zmp formulation and effective whole-body motion generation for a human-like mechanism

An approach of generating dynamic biped motions of a human-like mechanism is proposed. An alternative and efficient formulation of the Zero-Moment Point for dynamic balance and the approximated ground reaction forces/moments are derived from the resultant reaction loads, which includes the gravity, the externally applied loads, and the inertia. The optimization problem is formulated to address the redundancy of the human task, where the general biped and task-specific constraints are imposed depending on the task requirements. The proposed method is fully predictive and generates physically feasible human-like motions from scratch; it does not require any input reference from motion capture or animation. The resulting generated motions demonstrate how a human-like mechanism reacts effectively to different external load conditions in performing a given task by showing realistic features of cause and effect. In addition, the energy-optimality of the upright standing posture is numerically verified among infinite feasible static biped postures without self contact. The proposed formulation is beneficial to motion planning, control, and physics-based simulation of humanoids and human models.Copyright

Dynamic optimization of human stair-climbing motion

Abstract : The objective of this paper is to present our method of predicting and simulating visually realistic and dynamically consistent human stair-climbing motion. The digital human is modeled as a 55-degrees of freedom branched mechanical system with associated human anthropometry-based link lengths, mass moments of inertia, and centers of gravity. The joint angle profiles are determined using a B-spline-based parametric optimization technique subject to different physics-based, task-based, and environment-based constraints. The formulation offers the ability to study effects of the magnitude and location of external forces on the resulting joint angle profiles and joint torque profiles. Several virtual experiments are conducted using this optimization-based approach and results are presented.

A Musculoskeletal Model of the Upper Limb for Real Time Interaction

With the ever-increasing power of real time graphics and computational ability of desktop computers, the desire for a real-time simulation of the musculoskeletal system has become more pronounced. It is important that this simulation is realistic, interactive, runs in real time, and looks realistic, especially in our climate of Hollywood special-effects and stunning video games. An effective simulation of the musculoskeletal system hinges on three key features: accurate modeling of kinematic movement, realistic modeling of the muscle attachment points, and determining the direction of the forces applied at the points. By taking known information about the musculoskeletal system and applying it in a real time environment, we have created such a model of the human arm. This model includes realistic constraints on the joints and real-time wrapping algorithms for muscle action lines. Preliminary evaluation shows that the moment arms calculated by our model are similar to those shown in the literature. Furthermore, by coupling our model with known optimization algorithms, muscle activation levels for prescribed joint torques can be calculated in real time.

Newly Developed Functionalities for the Virtual Human Santos

This paper presents newly developed capabilities for the virtual human Santos. Santos is an avatar that has extensive modeling and simulation features. It is a digital human with 109 degrees of freedom (DOF), an optimization-based method, predictive dynamics, and realistic human appearance. The new capabilities include (1) significant progress in predictive dynamics (walking and running), (2) advanced clothing modeling and simulation, (3) muscle wrapping and sliding, and (4) hand biomechanics. With these newly developed functionalities, Santos can simulate various dynamic tasks such as walking and running, investigate clothing restrictions to motion such as joint limits and torques, simulate the musculoskeletal system in real time, predict hand injury by monitoring the joint torques, and facilitate vehicle interior design. Finally, additional on-going projects are summarized.

General Biped Motion and Balance of a Human Model

ABSTRACT We propose an algorithm of predicting dynamic biped motions of Santos TM human model. An alternative and efficient formulation of the Zero-Moment Point (ZMP) for dynamic balance and the approximated ground reaction forces/moments are derived from the resultant reaction loads, which includes the gravity, the externally applied loads, and the inertia. The optimization problem is formulated to address the redundancy of the human task, where the general biped and the task-specific constraints are imposed depending on the task requirements. The proposed method is fully predictive and generates physically feasible human-like motions from scratch without any input reference from motion capture or animation. The resulting generated motions demonstrate how a human reacts effectively to different external load conditions in performing a given task by showing realistic features of cause and effect. Key words : human motion generation, Lagrangian dynamics, optimization, Zero-Moment Point.