Reaction Force Compensation Mechanism Research Articles

A Passive RFC (Reaction Force Compensation) Mechanism Using Adjustable Piecewise Linear Stiffness of Pre-Compressed Springs

Nonlinear elements are used when a mechanical system has different performance requirements according to its positions. Piecewise linear system is widely used to investigate and to approximate nonlinear elements. So far, just springs with constant stiffness were used for passive, active or semi-active RFC (reaction force compensation) systems. In this paper, we developed an adjustable passive RFC mechanism for a linear motor motion stage using pre-compressed springs with piecewise linear stiffness. First, principle and related theory of the passive RFC mechanism using pre-compressed springs was introduced. Then, we modified a linear motor motion stage to install pre-compressed springs and the effect of a pre-compression of springs on the RFC performance was studied by free vibration test. Finally, the effectiveness of the adjustable passive RFC mechanism using pre-compressed springs was verified with simulation and experiment.

Input-Shaping Methods for a Linear Motor Motion Stage with a Passive RFC(Reaction Force Compensation) Mechanism

The residual vibration during the high acceleration and deceleration of a motion stage degrades the manufacturingsystem productivity and lifespan. Although a passive RFC mechanism with a movable magnet track reduces the residual vibration of the system base, a magnet track resonance may occur according to the motion profile, and the mover inposition error increases due to the residual vibration of the magnet track. We investigated input-shaping methods for a linear motor motion stage with a passive RFC mechanism. An air-bearing linear motor motion stage with the passive RFC mechanism is built, and the dynamic characteristic of the passive RFC mechanism is identified using a freevibration test. Then, mover velocity profiles are generated using various input-shaping methods. Further, the effects of the input-shaping methods on the air-bearing linear motor motion stage are investigated by comparing the magnet track oscillation, settling time, and mover in-position error. Finally, several input-shaping methods are applied to reduce the mover rise-time delay for the proposed linear motor motion stage. A properly shaped input motion profile removes the residual vibration of the passive RFC mechanism without any additional devices, as well as reducing the transmitted reaction force and the in-position error.

Both energy and cost-effective semi-active RFC (reaction force compensation) method for linear motor motion stage

Residual vibration of the system base due to the rapid acceleration of a motion stage may significantly reduce life span and productivity of the manufacturing equipment. Although a passive reaction force compensation (RFC) mechanism was developed to reduce the residual vibration of a linear motor motion stage, the passive RFC cannot adjust its dynamic characteristic against the motion profile variation. An active RFC mechanism using an additional coil can tune spring and damping of the RFC system according to the motion profile of the mover, but both cost and energy consumption of the active RFC are very high and it is not suitable for green manufacturing. In this paper, we develop a semi-active RFC method by switching an extra coil for a linear motor motion stage to tune damping of the RFC system against the motion profile variations. First, we investigate the effect of switching the extra coil with free vibration test of the magnet track, which shows that the damping of the RFC can be adjusted by the open-close ratio of the extra coil. In addition, two kinds of motion profiles such as long and short stroke motions are used to confirm the semi-active RFC by switching the extra coil. The effectiveness of the semi-active RFC method was verified with simulations and experiments.

Semi-active reaction force compensation for a linear motor motion stage

Acceleration and deceleration of a mover excite unwanted vibration to the system base, causing a significant reduction of life and productivity to manufacturing equipment. The system base vibration of a linear motor motion stage can be reduced with a passive reaction force compensation (RFC) mechanism. However, the passive RFC mechanism cannot provide the capability to adjust its stiffness and damping coefficient in real-time. Therefore, resonance may occur if the frequency of the passive RFC mechanism accidentally matches with the frequency components of applied motion profile. This paper presents a semi-active RFC method for a linear motor motion stage using an additional fixed coil. The semi-active RFC mechanism can adjust damping coefficient by changing the resistor load or switching the period of the additional fixed coil. The semi-active RFC mechanism also does not require an additional amplifier or control axis. Mathematical analysis of the semi-active RFC is presented to demonstrate the adjustable damping capability by changing the load resistor. Finally, the effectiveness of the proposed semi-active RFC mechanism is verified via simulations and experiments.

Eddy current damper type reaction force compensation mechanism for linear motor motion stage

The base vibration of a linear motor motion stage has been reduced with a passive reaction force compensation (RFC) mechanism based on a movable magnet track and springs. This paper presents the design procedure of an eddy-current damper (ECD) type RFC mechanism for a linear motor motion stage. The RFC mechanism with a movable magnet track and an ECD can overcome the disadvantages of the spring based RFC mechanism such as resonance and difficulty of assembly due to springs. A lumped parameter model for the ECD type RFC mechanism is derived considering sinusoidal magnetic flux density and the effective width of the ECD according to magnet track motion. Then, an iterative design procedure for ECD type RFC mechanisms is proposed to meet system requirements such as the transmission ratio of the reaction force and the maximum magnet track motion. Finally, a design example illustrates the effectiveness of the proposed design procedure for an ECD type RFC mechanism.

A Fuzzy-P controller of an active reaction force compensation (RFC) mechanism for a linear motor motion stage

Residual vibration of system base due to high-speed motion of a stage may significantly reduce life span and productivity of the manufacturing equipment. Although a passive reaction force compensation (RFC) mechanism was developed to reduce residual vibration of a linear motor motion stage, the passive RFC mechanism should be redesigned according to variation of motion profiles. In this paper, we develop a fuzzy-P (proportional) controller of an active RFC mechanism to automatically tune the gain according to variation of motion profiles. First, frequency components of motion profiles for a linear motion stage are analyzed and performances of the passive RFC mechanism are approximately evaluated using a motion profile analysis. An active RFC mechanism with an additional control coil is introduced to overcome limitation of the passive RFC mechanism and a fuzzy rule is proposed to automatically tune the P controller of the active RFC mechanism according to variations of motion profiles. Simulations and experiments are performed to show effectiveness of the proposed fuzzy rule for tuning the P control gain of the active RFC mechanism.

Dynamic analysis and iterative design of a passive reaction force compensation device for a linear motor motion stage

Acceleration and deceleration of a mover excites vibration of the system base so as to reduce life as well as productivity of manufacturing equipment. Vibration of the system base of a linear motor motion stage can be significantly reduced with reaction force compensation (RFC) mechanisms. However, transmitted force to the system base is minimized without considering dynamics of the system base in the previous research. In this paper, dynamic analysis of the RFC system with a movable magnet track is performed considering dynamics of its system base. Furthermore, we propose an iterative design procedure for the linear motor motion stage to minimize the vibration of the system base. First, a 5 DOF dynamic model of RFC mechanism including the system base and the mover is derived and its dynamic characteristic is investigated. In addition, dynamic responses of the linear motor motion stage to both long and short stroke motions are analyzed with simulations. Secondly, an iterative design procedure of the RFC mechanism for given input motion profiles is proposed to minimize the vibration of the system base. The proposed design procedure consists of two main steps: RFC design and the system base design. Finally, effectiveness of the proposed design is verified with simulations.

추가 이동 질량을 이용한 선형 모터용 반발력 보상 기구

Reaction force compensation (RFC) mechanism can relieve the vibration of base system caused by acceleration and deceleration of mover. In this paper, we propose a new passive RFC mechanism with a movable additional mass to reduce vibration of the system base as well as displacement of the magnet track. First, equation of motion for the new passive RFC mechanism is derived and simulated to tune design parameters such as masses and spring coefficients. Simulation results show that the vibration of the system base of the stage with the new RFC mechanism.

A passive reaction force compensation (RFC) mechanism for a linear motor motion stage

Vibration of the system base due to reaction force of rapid acceleration or deceleration motion of a stage is one of main causes for reducing life and productivity of the manufacturing equipment. This paper presents a passive RFC (reaction force compensation) mechanism for a linear motor motion stage. A systematic design process of the RFC system is developed based on a simple mathematical model of the RFC system. In addition, two ways are introduced to reduce the resonance vibration of the magnet track. Finally, a XY linear motion stage with the RFC mechanism is built, and the performance of the system is verified experimentally: In case of acceleration and deceleration of 10 m/s2, around 60% of residual vibration of the system base is reduced with the RFC mechanism.

2A36 Back EMF compensation of a linear motor stage with a passive RFC mechanism(The 12th International Conference on Motion and Vibration Control)

The vibration of system base in a linear motor motion stage has been reduced with passive reaction force compensation (RFC) mechanism of movable magnet track type. However, the reaction force of the mover makes the magnet track oscillate so that the settling time of the mover may be increased due to induced back EMF of the mover coil. This paper presents a back EMF compensation of a linear motor stage with a movable magnet track using RBF (radial basis function) neural network. The linear motor stage with the passive RFC mechanism is mathematically modeled and the effect of the back EMF of the mover coil is investigated with simulations. A RBF neural network control is applied to compensate the back EMF of the mover coil and uncertain friction effect of the motion stage. Finally, the effectiveness of the back EMF compensation method is verified by both simulations and experiments of a linear motor stage with the RFC mechanism.

Multi-Physical Analysis of Eddy Current Damper (ECD) for Reaction Force Compensation Device

This paper present multi-physical transient analysis of eddy current damper (ECD) for reaction force compensation device. A reaction force compensation mechanism with a movable magnet track and an ECD (or conductor plate) is developed. Lumped model of the ECD is derived and effects of both the location and width of the conductor plate are discussed. Multi-physical transient analysis of ECD is analyzed using commercial finite element software, which is compared with the lumped parameter analysis.