Redistribution of Link Masses to Reduce Shaking Effects in a Spatial Mechanism

Unbalanced mechanisms running at high speeds generate variable shaking forces and shaking moments on their foundations. The shaking forces and moments are unwanted in a machine because they cause serious problems (i.e. noise, vibrations, unnecessary wear). Hence, balancing the shaking forces and moments in high-speed mechanisms is a very important design objective. Besides balancing of shaking forces and the shaking moments, minimization of the generalized actuator force (input torque of force) fluctuations and joint reaction fluctuations are also important to have a machine working properly and smoothly. There exist many studies about balancing of the machines in the literature. In these studies, generally, balancing of the machines is realized by using counterweights, additional links, and cams; springs… etc. A machine may rest on the ground under its own weight, or may be rigidly connected to the ground via bolts. Forces transmitted to the frame from the machine excite vibrations and these forces are detrimental if they are cyclic in nature. Forces transmitted to the frame due to the inertial effects of moving members of the machine are cyclic and they are the primary contributors to vibration excitation. Since inertial effects depend on masses and mass distribution of moving members, shaking forces and shaking moments that excite vibrations can be controlled by providing a suitable mass distribution.