• The Journal of Korea Robotics Society
• /
• v.12 no.1
• /
• pp.11-18
• /
• 2017

Static balance of an articulated robot arm at various configurations requires a torque compensating for the gravitational torque of each joint due to the robot mass. Such compensation torque can be provided by a spring-based counterbalance mechanism. However, simple installation of a counterbalance mechanism at each pitch joint does not work because the gravitational torque at each joint is dependent on other joints. In this paper, a 6 DOF industrial robot arm based on the parallelogram for multi-DOF counterbalancing is proposed to cope with this problem. Two passive counterbalance mechanisms are applied to pitch joints, which reduces the required torque at each joint by compensating the gravitational torque. The performance of this mechanism is evaluated experimentally.

• The Journal of Korea Robotics Society
• /
• v.15 no.1
• /
• pp.48-54
• /
• 2020

Home robot arms require a payload of 2 kg to perform various household tasks; at the same time, they should be operated by low-capacity motors and low-cost speed reducers to ensure reasonable product cost. Furthermore, as robot arms on mobile platforms are battery-driven, their energy efficiency should be very high. To satisfy these requirements, we designed a lightweight counterbalance mechanism (CBM) based on a spring and a wire and developed a home robot arm with five degrees of freedom (DOF) based on this CBM. The CBM compensates for gravitational torques applied to the two pitch joints that are most affected by the robot's weight. The developed counterbalance robot adopts a belt-pulley based parallelogram mechanism for 2-DOF gravity compensation. Experiments using this robot demonstrate that the CBM allows the robot to meet the above-mentioned requirements, even with low-capacity motors and speed reducers.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.3
• /
• pp.289-294
• /
• 2014

Industrial manipulators are usually heavy given the payloads they carry. Therefore, they require high-capacity servomotors and speed reducers, which leads to high costs. However, if manipulator weight could be compensated for using a counterbalance mechanism, the motors' and speed reducers' capacities could be minimized substantially. However, it is usually difficult to assure durability and reliability with the conventional wire-based counterbalance mechanism. Therefore, a more robust gear- and roller-based counterbalance mechanism is proposed in this study. A manipulator was developed using this mechanism; this manipulator maintains its performance even when using motors and reducers of lower capacities. The results of various simulations and experiments verified that the proposed mechanism provides the torque required to compensate for gravitational torque in any configuration and minimizes the torque required for supporting a large payload.

• The Journal of Korea Robotics Society
• /
• v.11 no.4
• /
• pp.242-247
• /
• 2016

A robot manipulator handling a heavy weight requires high-capacity motors and speed reducers, which increases the cost of a robot and the risk of injury when a human worker is in collaboration with a robot. To cope with this problem, we propose a collaborative manipulator equipped with a counterbalance mechanism which compensates mechanically for a gravitational torque due to the robot mass. The prototype of the manipulator was designed on the basis of a four-bar linkage structure which contains active and passive pitch joints. Experimental performance evaluation shows that the proposed robot works effectively as a collaborative robot.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.21 no.8
• /
• pp.9-18
• /
• 2022

As the COVID-19 continues, the demand for robotic technology that can be applied in face-to-face tasks such as delivery and transportation, is increasing. Although these technologies have been developed and applied in various industries, the robots can only be operated in a tidy indoor environment and have limitations in terms of payload. To overcome these problems, we developed a 2 degree of freedom(DOF) environmental adaptive robot leg with a double 1-DOF counterbalance mechanism (CBM) based on wire roller. The double 1-DOF CBM is applied to the two revolute joints of the proposed robot leg to compensate for the weight of the mobile robot platform and part of the payload. In addition, the link of the robot leg is designed in a parallelogram structure based on a belt pulley to enable efficient control of the mobile platform. In this study, we propose the principle and structure of the CBM that is suitable for the robot leg, and design of the counterbalance robot leg module for the environment-adaptive control. Further, we verify the performance of the proposed counterbalance robot leg by using dynamic simulations and experiments.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.41 no.6
• /
• pp.469-475
• /
• 2017

Workers in industrial fields are highly exposed to accidents or injuries caused by long working hours. An exoskeleton that is able to support the arm muscles of the worker and thereby reduce the probability of an accident and enhance working efficiency could be a solution to this problem. However, existing exoskeletons demand the use of high-priced sensors and motors, which makes them difficult to use in industrial fields. To solve this problem, we developed an arm assisting exoskeleton that consists only of mechanical components without any electronic sensors or motors. The exoskeleton follows the movement of the human arm by shoulder joint and ankle joint. In addition, counterbalance mechanisms are installed on the exoskeleton to support arm strength. The experimental validation of the exoskeleton was conducted using an EMG sensor, confirming the performance of the exoskeleton.

• Structural Engineering and Mechanics
• /
• v.86 no.2
• /
• pp.261-276
• /
• 2023

The use of the ordinary double nut (i.e., ODN) composed of a master nut (i.e., M-nut) and a slave nut (i.e., S-nut) is a highly efficient method to prevent bolts loosening. A novel double nut (i.e., FODN) composed of a master nut (i.e., M-nut) and flat slave nut (i.e., FS-nut) is proposed to save raw materials. The bolt fastening tests with single nut, ODN and FODN are performed to investigate the preload and counterbalance forces. Corresponding finite element analysis (FEA) models are established and validated by comparing the preload with the experimental results. The load-bearing capacity, the extrusion effect, and the contact stress of each engaged thread for ODN and FODN are observed by FEA. The experimental and simulated results revealed that the bolt fastening with double-nut has different load-transferring mechanisms from single-nut. Nevertheless, for double-nut/bolt assemblies, the FS-nut can provide load transfer that is like that of the S-nut, and the FODN is a reasonable and reliable fastening method. Furthermore, based on the theory of Yamamoto, a formula considering the extrusion effect is proposed to calculate the preload distribution of the double-nut, which is applicable to varying thicknesses of slave-nuts in double-nut/bolt assemblies.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.1469-1474
• /
• 2007

In recent years, research to machine large-surface micro-features has become important because of the light guide panel of a large-scale liquid crystal display and the bipolar plate of a high-capacity proton exchange membrane fuel cell. In this study, in order to realize the systematic design technology and performance improvements of an ultra-precision machine for machining the large-surface micro-features, a structural characteristic analysis was performed using its virtual prototype. The prototype consisted of gantry-type frame, hydrostatic feed mechanisms, linear motors, brushless DC servo motor, counterbalance mechanism, and so on. The loop stiffness was estimated from the relative displacement between the tool post and C-axis table, which was caused by a cutting force. Especially, the causes of structural stiffness deterioration were identified through the structural deformation analysis of sub-models.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.12
• /
• pp.1173-1179
• /
• 2007

In recent years, research to machine large-surface micro-features has become important because of the light guide panel of a large-scale liquid crystal display and the bipolar plate of a high-capacity proton exchange membrane fuel cell. In this study, in order to realize the systematic design technology and performance improvements of an ultra-precision machine for machining the large-surface micro-features, a structural characteristic analysis was performed using its virtual prototype. The prototype consisted of gantry-type frame, hydrostatic feed mechanisms, linear motors, brushless DC servo motor, counterbalance mechanism, and so on. The loop stiffness was estimated from the relative displacement between the tool post and C-axis table, which was caused by a cutting force. Especially, the causes of structural stiffness deterioration were identified through the structural deformation analysis of sub-models.