When imparting a large force to the environment, a human will utilize his entire body to develop a mechanical advantage. For pushing, pulling or wielding a heavy object or tool, a
Master of Science Thesis Jijju Thomas
2 Introduction
stable stance is found with all the points of contact considered. When producing a pushing force, a human’s stance often consists of either one foot or both feet displaced some distance from the object being pushed. The two stances are called the ‘feet-apart’ pose and the ‘feet- together’ pose as shown in Figure 1-1. An angled-body posture, by displacing the center of mass both forward and downward, can help reduce the amount of torque that the pushing ankle needs to counteract. The statically displaced center …show more content…
Rancourt and Hogan (2001), rather than studying just the maximum force exerted in a given stance, studied the ability to modulate force at the hands [1]. The effects of body angle, hand torque, vertical hand force and the lifting of a leg to raise ones center of mass were calculated and shown to allow for small variations in force exerted. The effect of a feet-together versus a feet-apart pose was also explored. It was evaluated that with just one foot displaced back and the other left up front, pushing forces were an order of magnitude higher than those exerted in an upright and statically stable pose. Further, while allowing the center of mass to be displaced more drastically while maintaining stability, the force at the hands could be varied between zero and some maximum force without changing the stance or the locations of the feet. Irrespective of the posture considered by the human prior to pushing and while pushing, the mathematical model can be abstracted by an n-link closed chain manipulator. Additionally, the movement of the center of mass to exert a desired force at the end effector can be acheived by a workspace controller, thereby bringing us closer to mimicking human beings in the particular task of pushing
Master of Science Thesis Jijju Thomas
2 Introduction
stable stance is found with all the points of contact considered. When producing a pushing force, a human’s stance often consists of either one foot or both feet displaced some distance from the object being pushed. The two stances are called the ‘feet-apart’ pose and the ‘feet- together’ pose as shown in Figure 1-1. An angled-body posture, by displacing the center of mass both forward and downward, can help reduce the amount of torque that the pushing ankle needs to counteract. The statically displaced center …show more content…
Rancourt and Hogan (2001), rather than studying just the maximum force exerted in a given stance, studied the ability to modulate force at the hands [1]. The effects of body angle, hand torque, vertical hand force and the lifting of a leg to raise ones center of mass were calculated and shown to allow for small variations in force exerted. The effect of a feet-together versus a feet-apart pose was also explored. It was evaluated that with just one foot displaced back and the other left up front, pushing forces were an order of magnitude higher than those exerted in an upright and statically stable pose. Further, while allowing the center of mass to be displaced more drastically while maintaining stability, the force at the hands could be varied between zero and some maximum force without changing the stance or the locations of the feet. Irrespective of the posture considered by the human prior to pushing and while pushing, the mathematical model can be abstracted by an n-link closed chain manipulator. Additionally, the movement of the center of mass to exert a desired force at the end effector can be acheived by a workspace controller, thereby bringing us closer to mimicking human beings in the particular task of pushing