My advisor, Nancy S. Pollard, is a collaborator on all projects. This research is supported by the National Science Foundation (CCF-0343161, IIS-0326322, ECS-0325383, CNS-0423546, and CCF-0702443). I also received support from a National Science Foundation Graduate Research Fellowship and a NASA Harriet G. Jenkins Pre-Doctoral Fellowship.
Pre-grasp interaction adjusts object placement in the environment instead of directly grasping from its presented position. Humans use this strategy naturally to dexterously manipulate objects in their environment. I believe humans expect similar dexterity from intelligent robots and convincing animated characters or virtual avatars.
Perception of manipulation actions.In current work, I am investigating how human observers respond to manipulation actions in other agents.
Planning pre-grasp manipulation for transport tasks.Our human studies and initial robot demonstration suggest the advantages of pre-grasp interaction in task robustness and dexterous appearance. However, automation of the this technique is difficult due to practical challenges in manipulation planning. I develop a method for planning complete manipulation tasks that include pre-grasp interaction, based on a technique similar to posture-based models of human motor behavior.
CitationLillian Y. Chang, Siddhartha S. Srinivasa, and Nancy S. Pollard. Planning pre-grasp manipulation for transport tasks. IEEE International Conference on Robotics and Automation (ICRA 2010), in press, May 2010.
Selection criteria for preparatory object rotation in manual lifting actions.
We investigate what factors change the human performance of pre-grasp interaction. We found that this strategy is most relevant to difficult tasks involving heavy objects or high precision constraints. In addition, the amount of pre-grasp rotation correlated with the resulting change in lifting capability at the grasping posture. Our results suggest that pre-grasp interaction is more robust for new and repeated tasks compared to direct grasping.
CitationLillian Y. Chang, Roberta L. Klatzky, and Nancy S. Pollard. Selection criteria for preparatory object rotation in manual lifting actions. Journal of Motor Behavior, in press, July 2009.
Pre-grasp interactions in natural manipulation actions
Pre-grasp rotation is only one example of a pre-grasp interaction strategy. In this video survey of human hand activity, we filmed people performing manipulation tasks in the home and workplace. We found that there is indeed a broad class of pre-grasp interactions used naturally by humans. Our framework describes the survey examples according to two main aspects of object re-configuration and underlying purpose of the adjustment.
CitationLillian Y. Chang and Nancy S. Pollard. Video survey of pre-grasp interactions in natural hand activities. Robotics: Science and Systems (RSS) 2009 Workshop: Understanding the Human Hand for Advancing Robotic Manipulation, University of Washington, Seattle, USA, June 28 2009.
Grasping with an anthropomorphic robot manipulator
We demonstrate how pre-grasp interaction can improve robot manipulation. Taking advantage of object movability can make good grasps possible for more task conditions and reduce the expense of programming a complex mechanism. Our empirical evaluation in this example showed that a simple open-loop pre-grasp rotation can increase the grasping success from 45-degree to 360-degree of input object orientations. This was achieved without programming new actions for each different input condition.
CitationLillian Y. Chang, Garth J. Zeglin, and Nancy S. Pollard. Preparatory object rotation as a human-inspired grasping strategy. IEEE International Conference on Humanoid Robots (Humanoids 2008), December 2008. 527-534.
Human lifting strategies under task constraints
In our first study of human pre-grasp interaction, we asked whether pre-rotation was a prevalent strategy performed naturally by humans under certain task constraints. We found that, when grasping heavy objects with one hand, humans naturally re-oriented the object handle to a preferred configuration prior to lifting the object from the surface. Interestingly, this pre-grasp rotation was not absolutely necessary, because the subjects could still complete the task even when rotation was not permitted. Our analysis suggests that the preference to use pre-grasp interaction may be due to the more natural body postures due to lower joint torques or increased stance and grasp stability.
CitationLillian Y. Chang, Garth J. Zeglin, and Nancy S. Pollard. Preparatory object rotation as a human-inspired grasping strategy. To appear at IEEE International Conference on Humanoid Robots (Humanoids 2008), Daejeon, Korea, December 2008.
Lillian Y. Chang and Nancy S. Pollard. On preparatory object rotation to adjust handle orientation for grasping Tech. Report CMU-RI-TR-08-10, Robotics Institute, Carnegie Mellon University, April, 2008.
Tool acquistion from a work surface
Direct whole-hand grasps of tools from a work surface are not possible because the object first needs to be lifted before the fingers can envelope the handle. In this exploratory project, we measured the complex manipulation humans use to pick up tools from a surface. Our observations of the hand interaction inspired our investigation of pre-grasp interaction in human manipulation.