Dynamic Analysis of a Pendulum Dynamic Automatic Balancer

Sohn, Jin Seung; Lee, Jin Woo; Cho, Eun Hyoung; Park, No Cheol; Park, Young Pil

doi:10.1155/2007/452357

Cited by 5 publications

(2 citation statements)

References 7 publications

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“…In addition, it is not available for standing type drives and can cause squealing noise from the friction between the balls and turntable. Other studies have been devoted to other types of auto balancers such as the pendulum-type auto balancer (Sohn et al 2007) and flexible auto balancer (Cheng et al 2008). The flexible auto balancer is capable of operation at wideband rotational speed, and dynamic stability is guaranteed regardless the initial position of the auto balancer.…”

Section: Introductionmentioning

confidence: 99%

Flexible auto balancer design for the reduction of optical disk drive vibration

et al. 2011

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This study investigates the design of a flexible auto balancer (FAB) for the compensation of disk eccentricity. The FAB has various advantages over a conventional auto ball balancer, such as low cost, ease of implementation, lack of noise and applicability to standingtype drives. For the FAB design, a finite element model is developed considering the prestress effect and spin-softening effect caused by rotation. The structure is optimized and fabricated based on finite element model verification via modal testing. In addition, the dynamic behavior of the FAB is recorded by high-speed photography, and the vibration transmission to the base deck is measured.

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Section: Introductionmentioning

confidence: 99%

Flexible auto balancer design for the reduction of optical disk drive vibration

et al. 2011

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“…Sohn et al studied the stability behavior of a pendulum balancer (Sohn et al 2007). Hwang and Chung studied a horizontally oriented ball balancer with two raceways to reduce the occurrence of collisions (Hwang and Chung 1999).…”

Section: B Literature Overviewmentioning

confidence: 99%

The effects of ball interactions on the dynamic behavior of a ball balancer rotating at speeds above the translational resonant frequency of the system.

Dedow¹

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Dedow, Gregory A., "The effects of ball interactions on the dynamic behavior of a ball balancer rotating at speeds above the translational resonant frequency of the system." (2016 Many applications are inherently rotational in nature. These applications range from industrial products to consumer products. As seen in a traditional frequency response plot, the motion of a rotating imbalance does not approach zero as the forcing frequency is increased. Unlike a traditional forced mass spring oscillator, the motion of the rotating imbalance approaches some non-zero value. To account for this residual motion, some systems utilize a balancing device to reduce this motion. These balancing devices can be passive or active, depending on the design considerations. This paper will focus on the traditional, passive ball-type balancer due to its simplicity and extensive use in application. This paper derives the equations of motion for a vertically oriented ball-type balancing system. Due to the high non-linearity of these equations, a fourth order Runge-Kutta numerical integration method is used. The ball balancer equations of motion contain the proper physics needed for full operation such that the ball balancer can translate horizontally, vertically and rotate angularly in the presence of gravity. Acceleration terms are included such that a wide range of operating conditions can be tested. Additionally, n number of balls are present, which are affected by rolling friction and viscous fluid drag.Unlike many numerical models published in the past, the ball-to-ball interactions are not neglected within this model. These interactions include collisions, and train formations and separations. An application of the method presented by (Henon 1982) is utilized where the equations of motion are altered such that an exact integration step can be solved. This is based on the need for a displacement step (collision) or a force step (separation).Although the model presented can accommodate n number of balls, only a maximum ball count of two is considered. It is shown how the behavior of the balls affect the motion response of the ball balancer at rotational velocities above the translational resonance of the system. It is seen that a critical transition is reached; the operating point at which the ball balancer becomes effective at offsetting an eccentric mass. It is also seen that ball balancer displacement decreases until a point of saturation, after which ball balancer displacement increases. Also for the two iv ball case, it is shown that the spatial characteristics of the balls do affect steady state motion.The angle that separates two contacting balls alters the center of gravity of the train of balls such that the balancing capacity of the system is reduced. Although this effect is shown to be small for a two ball case, the balancing capacity is further reduced as the angle between two contacting balls becomes larger.

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Automatic Balancing of Twin Co-Planar Rotors

DeSmidt

Jung

2011

Journal of Vibration and Acoustics

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This paper explores the dynamics and stability of a twin rotor system fitted with passive automatic balancing devices (ABD). Essentially, autobalancers consist of several freely moving eccentric balancing masses. At certain speeds, the stable equilibrium position of the balancer masses is such that they naturally adjust to cancel the rotor imbalance. This “automatic balancing” phenomena occurs as a result of nonlinear dynamic interactions between the balancer masses and the rotor vibrations. Previous studies have explored automatic balancing of single rotors. In particular, ABDs are widely utilized for imbalance correction in computer optical disk and hard-drive applications. For such systems, automatic balancing occurs at supercritical operating speeds. While automatic balancing of single rotors is generally well understood, there has been only limited work on the topic of multirotor system automatic balancing. Therefore, this investigation considers a twin co-planar rotor system consisting of two symmetrically situated rotors mounted on a common flexible foundation structure. Both rotors are fitted with ABDs and the simultaneous autobalancing behavior of both rotors is investigated. Here, the nonlinear equations-of-motion of the twin-rotor/ABD system are derived and the asymptotic stability about the balanced condition is determined via a perturbation and floquet analysis. It is found that for the case of co-rotating rotors, automatic balancing is only achievable at supercritical speeds relative to the system torsional and lateral modes. However, for counter-rotating rotors, automatic balancing occurs at both subcritical and supercritical speeds relative to the foundation torsional mode. In this investigation, a dimensionless parameter study conducted to explore the effects of rotation speed, torsion and lateral mode placement, twin-rotor imbalance phasing, autobalancer mass, and damping for both the co- and counter-rotating cases. By considering the dynamic interactions between two rotor/ABD sub-systems, it is hoped that this study will provide valuable insight into the use of ABDs in multirotor system applications.

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Dynamic Analysis of a Pendulum Dynamic Automatic Balancer

Cited by 5 publications

References 7 publications

Flexible auto balancer design for the reduction of optical disk drive vibration

Flexible auto balancer design for the reduction of optical disk drive vibration

The effects of ball interactions on the dynamic behavior of a ball balancer rotating at speeds above the translational resonant frequency of the system.

Automatic Balancing of Twin Co-Planar Rotors

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