Scissor lift with real-time self-adjustment ability based on variable gravity compensation mechanism

Most robots involved in vertical movement against gravitation require actuators large enough to support their own weight. To improve the inherent safety of such robots against the large actuators and reduce their energy consumption, numerous gravity compensation mechanisms (GCMs) have been proposed. Our previous study proposed a variable GCM (VGCM) that uses two types of springs and can adjust the compensation force. In this paper, a VGCM-based scissor lift (pantograph lift) that uses three springs and a smaller actuator is proposed. A prototype is designed and fabricated, and the performance of the prototype is evaluated experimentally. The results demonstrate that the developed scissor lift meets the design specifications. In addition, a load estimator is established based on the dynamic model of the scissor lift. A real-time self-adjustment method that automatically changes the compensation force is proposed, and its effectiveness is verified

Stiffness modeling of robotic manipulator with gravity compensator

The paper focuses on the stiffness modeling of robotic manipulators with gravity compensators. The main attention is paid to the development of the stiffness model of a spring-based compensator located between sequential links of a serial structure. The derived model allows us to describe the compensator as an equivalent non-linear virtual spring integrated in the corresponding actuated joint. The obtained results have been efficiently applied to the stiffness modeling of a heavy industrial robot of the Kuka family

Modelling of the gravity compensators in robotic manufacturing cells

The paper deals with the modeling and identification of the gravity compensators used in heavy industrial robots. The main attention is paid to the geometrical parameters identification and calibration accuracy. To reduce impact of the measurement errors, the design of calibration experiments is used. The advantages of the developed technique are illustrated by experimental result

Identification of geometrical and elastostatic parameters of heavy industrial robots

The paper focuses on the stiffness modeling of heavy industrial robots with gravity compensators. The main attention is paid to the identification of geometrical and elastostatic parameters and calibration accuracy. To reduce impact of the measurement errors, the set of manipulator configurations for calibration experiments is optimized with respect to the proposed performance measure related to the end-effector position accuracy. Experimental results are presented that illustrate the advantages of the developed technique.Comment: arXiv admin note: substantial text overlap with arXiv:1311.667

Passive Gravity Balancing with a Self-Regulating Mechanism for Variable Payload

Gravity balancing techniques allow for the reduction of energy consumptions in robotic systems. With the appropriate arrangements, often including springs, the overall potential energy of a manipulator can be made configuration-independent, achieving an indifferent equilibrium for any position. On the other hand, such arrangements lose their effectiveness when some of the system parameters change, including the mass. This paper proposes a method to accommodate different payloads for a mechanism with a single degree-of-freedom (DOF). By means of an auxiliary mechanism including a slider, pulleys and a counterweight, the attachment point of a spring is automatically regulated so as to maintain the system in indifferent equilibrium regardless of the position, even when the overall mass of the system varies. Practical implications for the design of the mechanism are also discussed. Simulation results confirm the effectiveness of the proposed approach

非線形弾性要素による内部力補償に基づく無段階変位–力変換機構の創生 ― 微小操作力で強大な磁気力・把持力・制動力・張力を制御可能とするロボット要素 ―

Tohoku University博士（情報科学）thesi

人と共存するロボットのためのアーム機構と安全性評価手法の研究

芝浦工業大学2017年

Design and prototype of Variable Gravity Compensation Mechanism (VGCM)

A machine moving vertically requires strong gravitational resistance. Gravity compensation mechanisms devised to reduce actuator force mostly compensate for constant weight, but practical use requires that the mechanism compensate for weight variations. This paper presents a Variable Gravity Compensation Mechanism (VGCM) that uses two types of linear springs and changes the equilibrium position of one. The mechanism principle is described and the prototype is designed. Performance is experimentally confirmed