Katsu Yamane

Synthesizing animations of human manipulation tasks

Even such simple tasks as placing a box on a shelf are difficult to animate, because the animator must carefully position the character to satisfy geometric and balance constraints while creating motion to perform the task with a natural-looking style. In this paper, we explore an approach for animating characters manipulating objects that combines the power of path planning with the domain knowledge inherent in data-driven, constraint-based inverse kinematics. A path planner is used to find a motion for the object such that the corresponding poses of the character satisfy geometric, kinematic, and posture constraints. The inverse kinematics computation of the characters pose resolves redundancy by biasing the solution toward natural-looking poses extracted from a database of captured motions. Having this database greatly helps to increase the quality of the output motion. The computed path is converted to a motion trajectory using a model of the velocity profile. We demonstrate the effectiveness of the algorithm by generating animations across a wide range of scenarios that cover variations in the geometric, kinematic, and dynamic models of the character, the manipulated object, and obstacles in the scene.

Natural motion animation through constraining and deconstraining at will

This paper presents a computational technique for creating whole-body motions of human and animal characters without reference motion. Our work enables animators to generate a natural motion by dragging a link to an arbitrary position with any number of links pinned in the global frame, as well as other constraints such as desired joint angles and joint motion ranges. The method leads to an intuitive pin-and-drag interface where the user can generate whole-body motions by simply switching on or off or strengthening or weakening the constraints. This work is based on a new interactive inverse kinematics technique that allows more flexible attachment of pins and various types of constraints. Editing or retargeting captured motion requires only a small modification to the original method, although it can also create natural motions from scratch. We demonstrate the usefulness and advantage of our method with a number of example motion clips.

Somatosensory computation for man-machine interface from motion-capture data and musculoskeletal human model

We discuss the computation of somatosensory information from motion-capture data. The efficient computational algorithms previously developed by the authors for multibody systems, such as humanoid robots, are applied to a musculoskeletal model of the human body. The somatosensory information includes tension, length, and velocity of the muscles, tension of the tendons and ligaments, pressure of the cartilages, and stress of the bones. The inverse dynamics of the musculoskeletal human model is formulated as an optimization problem subject to equality and inequality conditions. We analyzed the solutions obtained by linear and quadratic programming methods, and showed that linear programming has better performance. The technological development aims to define a higher dimensional man-machine interface and to open the door to the cognitive-level communication of humans and machines.

Dynamics computation of structure-varying kinematic chains and its application to human figures

This paper discusses the dynamics computation of structure-varying kinematic chains which imply mechanical link systems whose structure may change from open kinematic chain to closed one and vice versa. The proposed algorithm can handle and compute the dynamics and motions of any rigid link systems in a seamless manner without switching among algorithms. The computation is developed on the foundation of the dynamics computation algorithms established in robotics, which is superior in efficiency due to explicit use of the generalized coordinates to those used in the general-purpose motion analysis softwares. Although the structure-varying kinematic chains are commonly found in computing human and animal motions, the computation of their dynamics has not been discussed in literature. The developed computation will provide a general algorithm for the computation of motion and control of humanoid robots and computer graphics human figures.

Virtual humanoid robot platform to develop controllers of real humanoid robots without porting

This paper presents a virtual humanoid robot platform (V-HRP for short) on which we can develop the identical controller for a virtual humanoid robot and its real counterpart. The unification of the controllers for the virtual and real robot has been realized by introducing software adapters for two robots respectively and employing ART-Linux on which real-time processing is available at the user level. Thanks to the unification, the controllers can share softwares with the dynamics simulator of V-HRP, including the parameter parser, kinematics and dynamics computations and the collision detector. This feature can make the development of the controllers more efficient and the developed controllers more reliable.

Open architecture humanoid robotics platform

This paper introduces an open architecture humanoid robotics platform (OpenHRP) on which various building blocks of humanoid robotics can be investigated. OpenHRP is a virtual humanoid robot platform with a compatible humanoid robot, and consists of a simulator of humanoid robots and motion control library for them which can also be applied to a compatible humanoid robot as it is. OpenHRP is expected to initiate the exploration of humanoid robotics on an open architecture software and hardware, due to the unification of the controllers and the examined consistency between the simulator and a real humanoid robot.

Kinetic chain of overarm throwing in terms of joint rotations revealed by induced acceleration analysis

This study investigated how baseball players generate large angular velocity at each joint by coordinating the joint torque and velocity-dependent torque during overarm throwing. Using a four-segment model (i.e., trunk, upper arm, forearm, and hand) that has 13 degrees of freedom, we conducted the induced acceleration analysis to determine the accelerations induced by these torques by multiplying the inverse of the system inertia matrix to the torque vectors. We found that the proximal joint motions (i.e., trunk forward motion, trunk leftward rotation, and shoulder internal rotation) were mainly accelerated by the joint torques at their own joints, whereas the distal joint motions (i.e., elbow extension and wrist flexion) were mainly accelerated by the velocity-dependent torques. We further examined which segment motion is the source of the velocity-dependent torque acting on the elbow and wrist accelerations. The results showed that the angular velocities of the trunk and upper arm produced the velocity-dependent torque for initial elbow extension acceleration. As a result, the elbow joint angular velocity increased, and concurrently, the forearm angular velocity relative to the ground also increased. The forearm angular velocity subsequently accelerated the elbow extension and wrist flexion. It also accelerated the shoulder internal rotation during the short period around the ball-release time. These results indicate that baseball players accelerate the distal elbow and wrist joint rotations by utilizing the velocity-dependent torque that is originally produced by the proximal trunk and shoulder joint torques in the early phase.

Optical motion capture system with pan-tilt camera tracking and real time data processing

This paper presents the real time processing of optical motion capture with pan-tilt camera tracking. Pan-tilt camera tracking expands the range of capturing field dynamically. The asymmetrical marker distribution and polyhedra search algorithm realize robust labeling against missing markers. The algorithm is developed for parallel cluster computation and enables real time data processing. Experimental results demonstrate the effectiveness of the system.

Simultaneous tracking and balancing of humanoid robots for imitating human motion capture data

This paper presents a control framework for humanoid robots that uses all joints simultaneously to track motion capture data and maintain balance. The controller comprises two main components: a balance controller and a tracking controller. The balance controller uses a regulator designed for a simplified humanoid model to obtain the desired input to keep balance based on the current state of the robot. The simplified model is chosen so that a regulator can be designed systematically using, for example, optimal control. An example of such controller is a linear quadratic regulator designed for an inverted pendulum model. The desired inputs are typically the center of pressure and/or torques of some representative joints. The tracking controller then computes the joint torques that minimize the difference from desired inputs as well as the error from desired joint accelerations to track the motion capture data, considering exact full-body dynamics. We demonstrate that the proposed controller effectively reproduces different styles of storytelling motion using dynamics simulation considering limitations in hardware.

Animating non-humanoid characters with human motion data

This paper presents a method for generating animations of non-humanoid characters from human motion capture data. Characters considered in this work have proportion and/or topology significantly different from humans, but are expected to convey expressions and emotions through body language that are understandable to human viewers. Keyframing is most commonly used to animate such characters. Our method provides an alternative for animating non-humanoid characters that leverages motion data from a human subject performing in the style of the target character. The method consists of a statistical mapping function learned from a small set of corresponding key poses, and a physics-based optimization process to improve the physical realism. We demonstrate our approach on three characters and a variety of motions with emotional expressions.