Proceedings of the ASME 2021International Mechanical Engineering Congress &amp; ExpositionIMECE2021 
November 1 – 4, 2021, Virtual, OnlineIMECE2021-XXXXX&nbsp;GRAVITY BALANCING DESIGN OF A 3-DOF HYBRID ROBOTIC MANIPULATOR WITH VARIABLE PAYLOADS&nbsp;&nbsp;Vu Linh NguyenDepartment of Mechanical EngineeringNational Chin-Yi University of Technology 
No. 57, Section 2, Zhongshan Road, Taiping District, Taichung City, Taiwanvlnguyen@ncut.edu.tw&nbsp;AbstractThis paper presents a design method to compensate for (statically balance) the gravity effect of a hybrid robotic manipulator with variable payloads. The hybrid manipulator is constructed by a two degrees-of-freedom (2-DOF) parallel mechanism combined with a 1-DOF serial mechanism. The balancing design is realized by attaching two spring mechanisms, each consists of a virtual gear-slider mechanism with an extension spring, to the manipulator. The design parameters of the spring mechanisms for gravity balancing are analytically derived from the static equilibrium of the manipulator. When the payload is varied, the articulated points of the springs can be relevantly adjusted to maintain the balancing condition of the manipulator. A design example is then given to illustrate the effectiveness of the proposed gravity balancing method. Besides, the method is also validated by a simulation-based analysis. These studies showed that, by using the proposed gravity balancing design, the total motor torque of the manipulator could be reduced by more than ninety percent, even when the payload is changed.IntroductionGravity balancing or compensation for robotic manipulators is considered a design technique that implements passive energy elements (mainly counterweights and mechanical springs) to the manipulator for compensating the gravity effect on its weight [1]. Gravity compensation has the great benefit of reducing the driving torque of actuators, leading to lessening the actuator size of the robot and energy consumption. The robot accuracy and safety are also improved with gravity compensation techniques [2]. The counterweight method (i.e., the method using counterweights for gravity compensation) is well-known and achieved by using additional masses (i.e., counterweights) to the robot system to relocate its equivalent center of mass to a stationary position [3]. The main disadvantage of this method is that the supplementary masses can increase the total weight and inertia of the system significantly. The spring method is usually considered an attractive solution to solve the mass-increased issue because it uses the elastic energy of the springs with small additional masses for gravity compensation [3]. However, the structural complexity, including the spring implementation, is considered the main issue of the spring method [4].&nbsp;

Gravity Balancing Design of a 3-DOF Hybrid Robotic Manipulator With Variable Payloads

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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