Mass Center of Planar Mechanisms Using Auxiliary Parallelograms

Abstract

Listen

Translate article

Abstract Center of mass is an important characteristic of a mechanism during motion. In some studies of biomechanics, it is necessary to monitor the motion of this point. The physical location of the center of mass during motion may have importance in the development of gravity compensated exercise machines. Also, a mechanism with the center of mass constrained to be inertially fixed has the same motion as if it was in zero gravity. This property may be exploited to develop test beds on earth that mimic the behavior of systems in space. In this paper, a method is described to augment planar mechanisms with auxiliary parallelograms in order to identify a physical point on the augmented mechanism which is the center of mass of the original mechanism. The original and the augmented mechanisms have the same degrees-of-freedom. If the links of the augmented mechanism are massless, the original and augmented mechanisms have the same motion. During motion, the center of mass is a physical point on the mechanism which can be monitored or used for other purposes motivated from the application. In practice, however, if such an augmented mechanism is constructed, its links will have finite masses. As a result, under the same inputs, the motion of the original and augmented mechanisms will be different. In this paper, the effects of finite masses of the additional links on the original mechanism are also discussed.