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This paper presents an approach for designing a novel tooth profile of harmonic drives, which is composed of two pieces of curves, hypocycloid and epicycloid, generated by the rolling circles with appropriate radii. Compared with the conventional double-circular-arc or cycloidal tooth profile of harmonic drives, the tooth profile is characterized by full conjugation, more number of engaged teeth, and can be expressed analytically, etc. Firstly, the generation of the cycloids are briefly described, and then their conjugate criterion is investigated systematically based on Camus's theorem. Secondly, the tooth profile equations for the circular spline and flexspline are established and the deformed neutral curve equation is derived. Next, the contact properties among the tooth profiles, including the line of action, meshing angle, etc., are studied systematically. Finally, a finite element model and a physical prototype for the harmonic drive with the tooth profile are developed, respectively. The effectiveness of the design method is verified by the contact performances simulation. The research may provide a new thought for the innovative design of harmonic drives with full conjugate tooth profile. [ABSTRACT FROM AUTHOR]

This paper focuses on a novel harmonic movable tooth drive as an alternative of currently used harmonic gear drives. Different from the harmonic gear drives, the novel drive removes small module teeth from thin-walled flexible rim, instead, adopts several rigid movable teeth with logarithmic spiral tooth profile. Such tooth geometry makes almost surface contact possible under load condition, in comparison with the conventional involute tooth profile creating a linear contact. Aiming at the issue of cusp meshing between movable tooth and ring gear during the meshing process, this paper proposes a modification design method for the conjugate tooth profiles. First, the radial motion law of movable tooth is modified, in order to avoid rigid impacts at the exchange point of the rise travel and return travel. Then, the tooth profile of ring gear is generated by the envelope of the modified profile of movable tooth. Based on the formulated modification scheme, the equations of the conjugate tooth profiles are derived, and the influences of spiral angle and modification parameters on the meshing characteristics are systematically investigated. Finally, the wave generator cam profile and pivoted segment profile are established considering the strength consistency. The outcomes can provide significance guidance for the parametric design and optimization of this novel drive. [ABSTRACT FROM AUTHOR]

This paper presents a static model for a novel movable tooth drive with logarithmic spiral tooth profiles, to research contact force and load distribution during the meshing period. According to the geometric properties of the conjugate tooth profiles, their compatibility law considering the multi-tooth elastic meshing effect are investigated to reveal load distribution characteristic of the teeth. The static model of the mechanism is thus developed to systematically analyze variation in contact force during the rise travel. The results indicate that the contact force between the tooth and ring gear is proportional to the curvature radius of the contact point, and it increases exponentially and monotonically corresponding to the curvature radius of logarithmic spiral tooth profile; in the multi-tooth meshing condition, the load distribution of the teeth coincides with the ratio of the curvature radius of each contact point, and periodical pulsations of total contact force occur at the alternation of the teeth. Finally, the proposed model is validated by the FEM simulation of a prototype, and the influence of dimensional parameters is further discussed for the self-locking and force transmission characteristics of the tooth. The outcomes provide critical technical support for the static modelling and design of such transmission mechanism. [ABSTRACT FROM AUTHOR]

This paper presents a method for designing a novel type of movable tooth drive characterized by logarithmic spiral conjugated tooth profiles, which are in almost full surface contact owing to such innovative tooth geometry, in comparison with the conventional involute or cycloidal tooth profiles creating a linear contact. Firstly, the existence conditions of the conjugated curve of the logarithmic spiral are researched by establishing the meshing equation, and its geometric and kinematic properties are identified to design the conjugated tooth profiles of the movable tooth and ring gear. Then, wave generator profile, according to the requirement that it should be completely convex and smooth, is designed and modified to ensure the consistency with load capacity of the conjugated tooth profiles. On this basis, dimensional synthesis of the mechanism is performed following the influence analysis of main factors on the force/motion transmission characteristic of the whole machine. Finally, the virtual prototype is developed and the proposed design method is validated by relevant force performance simulation. The outcomes lay a significant foundation for the design of such logarithmic spiral tooth profile transmission. [ABSTRACT FROM AUTHOR]

Due to the influencing factors, such as irregularity of guide, piston wind excitation in the hoistway, and uncertain swinging of hoisting rope during the operation of high-speed traction elevator, car will produce dramatic horizontal vibration. With the purpose of suppressing this vibration effectively, the active car shock absorber is designed with linear motor, and a five-degrees-of-freedom space vibration model of the car is established and, subsequently, its state space equation is derived. For the uncertainty external excitation in the car system, the back propagation neural network proportional–integral–derivative controller with linear prediction model is designed for the intelligent active control of the vibration of the car, and simulation analysis is carried out with MATLAB/Simulink. The result shows that the active shock absorber designed in this study can effectively suppress the horizontal vibration of high-speed elevator car, better than traditional proportional–integral–derivative controller. This study has opened up a new idea of high-speed elevator vibration damping method, and is of important referential significance for the field of active control of car vibration. [ABSTRACT FROM AUTHOR]

For RV reducer widely used in robots, vibration significantly affects its performance. A lumped parameter model is developed to investigate free vibration characteristics without and with gyroscopic effects. The dynamic model considers key factors affecting vibration such as involute and cycloid gear mesh stiffness, crankshaft bending stiffness, and bearing stiffness. For both nongyroscopic and gyroscopic systems, free vibrations are examined and compared with each other. Results reveal the specific structure of vibration modes for both systems, which results from symmetry structure of RV reducer. According to vibration of the central components, vibration modes of two systems can be classified into three types, rotational, translational, and planetary component modes. Different from nongyroscopic system, the eigenvalues with gyroscopic effects are complex-valued and speed-dependent. The eigenvalue for a range of carrier speeds is obtained by numerical simulation. Divergence and flutter instability is observed at speeds adjacent to critical speeds. Furthermore, the work studies effects of key factors, which include crankshaft eccentricity and the number of pins, on eigenvalues. Finally, experiment is performed to verify the effectiveness of the dynamic model. The research of this paper is helpful for the analysis on free vibration and dynamic design of RV reducer. [ABSTRACT FROM AUTHOR]

Bearings with rolling elements are often used as revolute joints to connect mechanical components. Due to their complex structure (clearance, multipoint contacts, defects, etc.), rolling element bearing joints are regarded as non-ideal revolute joints. In this paper, a method is proposed for modeling a non-ideal rolling ball bearing joint with localized defects in multibody systems. The kinematic constraints of an ideal revolute joint in traditional multibody dynamics theory are released, and functions of the non-ideal bearing joint are built using the interactions due to contact forces. Localized defects with a certain arc length and depth are established for the bearing raceway surfaces. An approach for contact detection between localized defects and rolling balls in bearing joint is suggested. Finally, a slider-crank mechanism containing a deep-groove ball bearing with localized defects is chosen as an example to demonstrate application of the methodology. The variation in the bearing joint equivalent reaction force, crank moment, slider acceleration, and acceleration-velocity portrait phase of the slider is used to illustrate the dynamic performance of the mechanism when the effect of bearing localized defects is considered. [ABSTRACT FROM AUTHOR]