Movable Teeth Research Articles

Natural Frequency and Modes for a Sine Movable Tooth Drive

The sine movable tooth drive has the smallest radial size, and it is suitable for oil drilling machine and robot arm, etc. In this paper, the authors proposed a vibration analysis model of the sine movable tooth drive system. Using the model, the free vibration performance of the sine movable tooth drive was investigated. Two types of vibrating modes for the sine movable tooth drive were found. Based on this, the effects of the drive parameters on the natural frequencies were analyzed. Results show that vibration modes for the sine movable tooth drive can be classified as two types. One type is the modes for simultaneous vibrations of the total elements, and another is the modes for vibrations of only movable teeth. The research is useful for dynamics design of the drive system.

Vibration Analysis of a Two‐Step Sine Movable Tooth Drive

In this study, a 3D model of a two‐step sine movable tooth drive is developed in the UG software. The finite element model (FEM) analysis package, ANSYS, is used to calculate the natural frequencies and vibration modes of the drive system. The results show that the first twenty natural frequencies can be classified into five families, including the total system vibration mode, single‐element vibration mode, two‐element vibration mode, three‐element vibration mode, and four‐element vibration mode. The effects of the system parameters on the natural frequencies and the vibration modes are investigated. The track amplitude, the movable tooth radius, the radius of the movable tooth rotation, and the number of movable teeth affect the natural frequencies and vibration modes of the drive system.

Transmission and Tooth Profile Equation of Swing Output Movable Teeth Cam Mechanism

Transmission and Tooth Profile Equation of Swing Output Movable Teeth Cam Mechanism

Serotonin Drives Predatory Feeding Behavior via Synchronous Feeding Rhythms in the Nematode Pristionchus pacificus

Feeding behaviors in a wide range of animals are regulated by the neurotransmitter serotonin, although the exact neural circuits and associated mechanism are often unknown. The nematode Pristionchus pacificus can kill other nematodes by opening prey cuticles with movable teeth. Previous studies showed that exogenous serotonin treatment induces a predatory-like tooth movement and slower pharyngeal pumping in the absence of prey; however, physiological functions of serotonin during predation and other behaviors in P. pacificus remained completely unknown. Here, we investigate the roles of serotonin by generating mutations in Ppa-tph-1 and Ppa-bas-1, two key serotonin biosynthesis enzymes, and by genetic ablation of pharynx-associated serotonergic neurons. Mutations in Ppa-tph-1 reduced the pharyngeal pumping rate during bacterial feeding compared with wild-type. Moreover, the loss of serotonin or a subset of serotonergic neurons decreased the success of predation, but did not abolish the predatory feeding behavior completely. Detailed analysis using a high-speed camera revealed that the elimination of serotonin or the serotonergic neurons disrupted the timing and coordination of predatory tooth movement and pharyngeal pumping. This loss of synchrony significantly reduced the efficiency of successful predation events. These results suggest that serotonin has a conserved role in bacterial feeding and in addition drives the feeding rhythm of predatory behavior in Pristionchus.

Quasi-static analysis of forces and stress for a novel two-step movable tooth drive

ABSTRACTFor sine movable tooth drive, the movable tooth number must be increased to obtain large speed ratio of the drive which increases largely radial size of the drive. Here, a novel two-step movable tooth drive is proposed. The drive can realize small size and large speed ratio simultaneously. For the two-step movable tooth drive, 3D design was done; the forces and the contact stress in the drive system were investigated; results show that the maximum force on the second step drive depends on radius of the movable teeth, size parameters of the second step drive, and radius of the sine ball track in the first step drive; the contact stresses between the meshing elements change periodically, the contact stress between the movable teeth and cap end is the maximum which can be taken as design factor for the load-carrying ability of the drive system.

Two-step sine movable tooth drive

For sine movable tooth drive, the movable tooth number must be increased to obtain large speed ratio of the drive which increases largely radial size of the drive. Here, a two-step sine movable too...

Numerical Analysis on Chaotic Vibration of Drive System for a Movable Tooth Piezoelectric Motor

The nonlinear dynamic equations of the drive system for movable tooth piezoelectric motor are established. Using these equations, the chaotic vibrations of the system are investigated. The results show that chaotic vibrations occur in the movable tooth drive system under some parameters. The average mesh stiffness, theoretical radius, and wave generator offset significantly influence the nonlinear chaotic vibrations of the drive system of the movable tooth piezoelectric motor. The ranges for the system parameters that lead to a motor with bad dynamics are shown. The results can be used to predict the dynamic load and optimize power density of the proposed piezoelectric motor.

Stomatal Dimorphism of Neodiplogaster acaloleptae (Diplogastromorpha: Diplogastridae).

Several genera belonging to the nematode family Diplogastridae show characteristic dimorphism in their feeding structures; specifically, they have microbial feeding stenostomatous and predatory eurystomatous morphs. A diplogastrid satellite model species, Pristionchus pacificus, and its close relatives have become a model system for studying this phenotypic plasticity, with intensive physiological and structural studies having been undertaken. However, the many other species that are morphologically and phylogenetically divergent from P. pacificus have not been examined to date. In the present study, the detailed stomatal structure and induction of dimorphism in Neodiplogaster acaloleptae were examined. N. acaloleptae has a fungal feeding stenostomatous morph and a predatory eurystomatous morph. The predatory morph was induced by starvation, high population density, and co-culturing with its potential prey, Caenorhabditis elegans. The feeding behavior of the stenostomatous and eurystomatous morphs of N. acaloleptae was confirmed, demonstrating that 1) the stomatal and pharyngeal movements of the two morphs were basically identical, and 2) the stomatal elements were protracted to cut open the hyphae and/or prey to feed when a N. acaloleptae flips its dorsal movable tooth dorsally and tilts its subventral stegostomatal cylinder ventrally, forming a pair of scissors to cut the food source. The stoma morphology of N. acaloleptae with a single movable tooth and a long stoma is markedly different from that of Pristionchus, which has two movable teeth and a short stoma. It is, however, similar to that of Mononchoides, tentatively a sister to Neodiplogaster.

Torque for an electromagnetic harmonic movable tooth drive system

The output torque of the mechanical harmonic drive is large but the teeth should be produced on the flexible ring which is a difficult task. To overcome the difficulty, the authors proposed an electromagnetic harmonic movable tooth drive system in which a large output torque can be obtained meanwhile the teeth are removed from the flexible ring. Here, the operating principle of the electromagnetic harmonic movable tooth drive system is illustrated. The forces on the flexible ring and the movable teeth are analyzed. The equation of the output torque for the drive system is developed. Using the equation, the output torque of the drive system and its changes along with the system parameters are investigated. The results show that large coil current, large speed ratio, large flexible ring radius and small flexible ring length, small gas gap should be selected to obtain a large output torque. The results are useful for the further study and application of the drive system.

Tooth Profile Design and Meshing Characteristics Analysis of Any Tooth-difference Pure Rolling Movable Tooth Transmission

Tooth Profile Design and Meshing Characteristics Analysis of Any Tooth-difference Pure Rolling Movable Tooth Transmission

Forced Response of an Electromagnetic Harmonic Movable Tooth Drive System to Current Excitation

In this study, the authors proposed an electromagnetic harmonic movable tooth drive system. , The forced response equation of the drive system to exciting currents was developed. Using this equation, the forced responses of the drive system to exciting currents were investigated. The results show that the forced responses of the drive system to the exciting currents were affected by mechanical and electric parameters. To reduce the vibrating amplitudes, smaller coil current, flexible ring radius, and average static displacement of the flexible ring, increased thickness of the flexible ring, clearance between the flexible ring and coils, and coil pole pair number should be taken into account. The results can be used for designing the system and further study of the dynamics performance of the drive system.

Free Vibration for an Electromagnetic Harmonic Movable Tooth Drive System

The authors proposed an electromagnetic harmonic movable tooth drive system which is an electromechanical coupled system where the coupled dynamics controls its overall operating behavior. However, the coupled dynamics of such a system was not found in the literature. In this paper, an electromechanical coupled dynamics equation of the flexible ring subjected to electromagnetic force is presented. Using the equation, the natural frequencies and vibration modes of the flexible ring are investigated. The results show that the natural frequency of the drive system is affected by mechanical and electrical parameters among which, the coil current, the average static displacement of the flexible ring and the air gap have more obvious influence on the natural frequencies. The results are useful for the design and further study of the dynamics performance for the drive system.

Research on the Temperature Characteristics of Movable Tooth Transmission Motor of Electromagnetic Harmonic

Based on the heat transfer characteristics of electromagnetic harmonic movable tooth transmission motor, this paper adopted the finite element method to establish a three-dimensional temperature field model for numerical calcula- tion on the basis of four basic assumptions. It analyzed the heat loss and gave out the functional to calculate the tempera- ture field within each medium and obtain the temperature distributing curves. Then taking the prototype as an example, it calculated the steady-state temperature field of the system under different loading. The comparison between the results and measured values has verified the reasonableness of the established model and calculation method employed. The re- sults could provide a theoretical basis for the optimized design of electromagnetic harmonic tooth transmission system.

Influence of Structural Parameters of Electromagnetic Harmonic Movable Teeth Transmission on System Loss

In view of the characteristics of electromagnetic harmonic movable teeth transmission system, the heat loss has been analyzed in this paper based on basic assumptions. At the same time, the calculation methods of electromagnetic loss and mechanical loss in system have been also discussed. Moreover, the influence of changes of system parameters on electromagnetic loss and mechanical loss has been analyzed through employing the field-circuit coupling finite element method. According to the analysis results, the numerical calculation model of the three-dimensional temperature field of system can be established. And the theoretical basis can be provided for the optimization design of electromagnetic harmonic movable teeth transmission system and the improvement of transmission efficiency of transmission system.

Adaptive value of a predatory mouth-form in a dimorphic nematode.

Polyphenisms can be adaptations to environments that are heterogeneous in space and time, but to persist they require conditional-specific advantages. The nematode Pristionchus pacificus is a facultative predator that displays an evolutionarily conserved polyphenism of its mouthparts. During development, P. pacificus irreversibly executes either a eurystomatous (Eu) or stenostomatous (St) mouth-form, which differ in the shape and number of movable teeth. The Eu form, which has an additional tooth, is more complex than the St form and is thus more highly derived relative to species lacking teeth. Here, we investigate a putative fitness trade-off for the alternative feeding-structures of P. pacificus. We show that the complex Eu form confers a greater ability to kill prey. When adults were provided with a prey diet, Eu nematodes exhibited greater fitness than St nematodes by several measures, including longevity, offspring survival and fecundity when followed by bacterial feeding. However, the two mouth-forms had similar fecundity when fed ad libitum on bacteria, a condition that would confer benefit on the more rapidly developing St form. Thus, the two forms show conditional fitness advantages in different environments. This study provides, to our knowledge, the first functional context for dimorphism in a model for the genetics of plasticity.

Dynamics for an electromechanical integrated harmonic piezodrive system

The Authors propose an electromechanical integrated harmonic piezodrive system. The dynamics behavior of the movable tooth drive has important effects on its operating performance. Here, the dynamic equations of the movable tooth drive for the drive system are presented. Using the equations, the natural frequencies and vibrating modes of the movable tooth drive are investigated. Results show that five vibrating modes occur for the movable tooth drive which include system modes, static crown gear modes, movable tooth modes, translating rotor modes and translating crown gear modes. Eccentric center, thickness and length of the flexible ring, diameter of the movable tooth and speed ratio have significant effects on the natural frequencies of the movable tooth drive and should be selected properly.

Study on Virtual Prototype Modeling of Swing Movable Teeth Transmission

As a new type planetary gear device, swing movable teeth transmission is used to transmit rotary motion and power between two shafts with same axis. It has compact structure, a large range of transmission ratio, strong carrying capacity and widely used. According to the principle of gear meshing, it was analyzed the principle and characteristics of the swing movable teeth transmission. Based on the structure was designed, after the entity modeling of the parts and the virtual assembly of the transmission are established, the virtual prototype modeling of swing movable teeth transmission was carried out by Solid Edge software. Virtual prototype modeling of transmission would provide the necessary for the force analysis and performance simulation.

An Electromechanical Integrated Harmonic Piezodrive System

An electromechanical integrated harmonic piezodrive system is proposed. The key of the proposed piezodrive system is the integration of the piezodrive principle with the harmonic drive and the movable tooth drive principles, which changes the sliding friction between the rotor and the vibrator into a rolling mesh. It can substantially increase the system's output torque, operating life, and efficiency. In this paper, the design of the drive system and its operating principles are presented. Under piezoelectric excitation, the deformation energy of the flexible ring was analyzed and the output torque of the drive system was calculated, revealing that the drive system produces a higher output torque than does a normal bar-type ultrasonic motor.

Transmission Theory and Typical Structure of Nonuniform Mechanism with Movable Teeth

Thanks to characteristics of compact structure, high load strength and good manufacture technics, the movable teeth transmission is expanded to the nonuniform transmission filed. The basic structure of nonconstant mechanism with movable rods is introduced. The profile formula of inner ring is constructed by simple cosine function and the outer is built under given transmission ratio. The continuous rotation condition, the transmission efficiency and the pressure angle among the rods, inner and outer rings of movable teeth device are discussed, which could provide theory base for its design. In addition, according to the initial position of movable rods, the mechanism is divided to two basic types. Ten different results are developed by fixing the rods, inner ring and outer ring separately. A movable teeth device with kinematic feature of elliptical gears is designed. An analysis of ten motion types of the mechanism is made under a set of same geometric datum. The simulation states that the nonuniform mechanism with movable teeth has bright application prospects by means of simple manufacturing process and transmission diversity.

Study on Dynamical Simulation of Swing Movable Teeth Reducer

Swing movable teeth reducer is a new type of small teeth difference planetary gear transmission. As a new product development technology, virtual prototype technology is a digital design method based on the product simulation model. It is important to carry on the performance simulation of the reducer and seek the optimization design of the products on virtual prototype technology. Based on the study on the principle and structure of the swing movable teeth transmission, it analyzed the motion of the system, carried on the dynamical simulation of the swing movable teeth reducer, which is established on the virtual prototype. At the same time, the paper analyzed the dynamical simulation on the rotational speed and force of the mainly parts.