Synthesis of Inherently Moment Balanced Robotic Manipulators
G.D. Becht (TU Delft - Mechanical Engineering)
V. van der Wijk – Mentor (TU Delft - Mechatronic Systems Design)
J. L. Herder – Graduation committee member (TU Delft - Precision and Microsystems Engineering)
AL Schwab – Graduation committee member (TU Delft - Biomechatronics & Human-Machine Control)
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Abstract
In robotics, machine elements are accelerated in order for the machine to perform certain tasks, such as picking and placing objects. These accelerations result in inertia forces and inertia torques on the machine elements and on the base of the machine. These reaction forces and reaction torques on the base are called shaking forces and shaking moments. Shaking forces and shaking moments result in noise, vibration, wear and fatigue problems. Dynamic balancing eliminates shaking forces and shaking moments on the base, which results in low cycle times and high accuracy. However, the process of balancing a mechanism generally increases the masses, the moments of inertia, and the complexity of the mechanism.
The method of inherent dynamic balance aims at minimizing these drawbacks by considering the balancing prior to the kinematic synthesis. With the method of principal vectors, a large number of inherently shaking force balanced mechanisms has been found. However, the options for shaking moment balanced mechanisms are still limited.
In this thesis, an overview of current dynamic balancing methods is presented, along with a new method for the synthesis of inherently moment balanced mechanisms. This new method is used for the synthesis of inherently dynamically balanced 1-DoF pantographic linkages, where the desired motion of the end-effector is selected by the designer. This motion is defined as a set of precision positions. For this new method, the known method for RR chain synthesis from Burmester’s theory is combined with the shaking moment balancing condition. For the special case where the relationship between link angular velocities is linear, the shaking moment balancing condition is substituted into the RR chain design equation. For the general case where the relation between link angular velocities is non-linear, the equation of motion is numerically solved for a range of possible solutions in order to find the solution which reproduces the desired motion.