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One-Piece Gravity Compensation Mechanism Using Cam Mechanism and Compression Spring

  • Giuk Lee
  • Donggun Lee
  • Yonghwan Oh
Regular Paper
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Abstract

In this paper, we propose a one-piece gravity compensation mechanism (OGCM), which improves energy efficiency by compensating for the gravity torque of the target structure using a combination of a cam mechanism and a compression spring. First, the gravity compensation methodology of the OGCM is explained. Next, an analysis of how to design cam mechanisms as a function of the design variables of other mechanical parts is presented. Finally, the gravity compensation performance of the OGCM is verified through experiments by comparing the designed and actual gravity compensation torques. In addition, we simply evaluate the gravity compensation performance of the OGCM visually by testing it on an actual target structure. Both the verification tests show that the OGCM provides decent performance as a gravity compensation mechanism. The proposed OGCM has many advantages. Because it can be constructed as an independent one-piece structure, it can be easily installed on the target platform without many modifications. Moreover, because of its compactness, the size and inertia of the target platform do not increase considerably after installation. The OGCM can also be operated in the entire 360° range, so it does not interfere with the existing workspace of the target platform after installation. Because of these advantages, the OGCM can be used effectively on a variety of platforms and structures.

Keywords

Gravity compensation Counterbalancing Cam mechanism Compression spring 

Nomenclature

DoF

Degree of freedom

CoM

Center of mass

CoR

Center of rotation

m

Weight of target structure

h

Distance between CoR and CoM of target structure

θ

Rotation angle of target structure from horizontal basement

S

Total length of compression spring

s1

Length of compression spring between CoR of one-piece gravity compensation mechanism (OGCM) and fixed end at stator

s2

Length of compression spring between CoR of OGCM and fixed end at cam follower

r

Radius of cam follower

k

Stiffness of compression spring

Vtarget

Gravitational potential energy of target structure

VOGCM

Elastic potential energy of OGCM

Vtotal

Sum of total potential energy of Vtarget and VOGCM

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Copyright information

© Korean Society for Precision Engineering 2018

Authors and Affiliations

  1. 1.Mechanical Engineering DepartmentChung-Ang UniversitySeoulRepublic of Korea
  2. 2.Center for Robotics ResearchKorea Institute of Science and Technology, 5SeoulRepublic of Korea
  3. 3.Mechanical Engineering DepartmentUniversity of CaliforniaBerkeleyUSA

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