At present, the uncertainty and randomness between equipment are not fully considered in the remaining useful life (RUL) prediction. In order to solve this problem, firstly, we use the Weibull distribution to describe the influence of various uncertain factors on the RUL of equipment, and introduce the Weibull Time-To-Event Recurrent Neural Network (WTTE-RNN) framework to transform the RUL of equipment from the prediction of single life value to the prediction of Weibull distribution parameters. Then, in view of the problem that RNN is prone to have low prediction accuracy due to the vanishing of gradient, considering the advantages of Long-Short Term memory (LSTM) in time series modeling, we replace RNN with LSTM to improve the model and construct WTTE- LSTM model. Furthermore, in order to further improve the model's ability to extract data features, Convolutional Neural Network (CNN) is added after the original data is normalized because of its excellent feature extraction ability, and the time series features extracted by CNN are used as the input of LSTM to construct the WTTE-CNN-LSTM model. Finally, the LSTM life prediction model, WTTE-LSTM model and WTTE-CNN-LSTM model are established by taking a data set from a core component of construction machinery as an example. The results demonstrate that the improved WTTE-CNN-LSTM model has the highest prediction accuracy and the smallest error.

To improve the machining efficiency of face gears, a novel efficient machining method referred to as power skiving is applied to the machining of face gears and is presented in this paper. The processing principle of machining face gears by power skiving and the relative motion between the cutting tool and the face gears is discussed. Then, the mathematical models of the power skiving cutter with a fillet angle and the machining process by power skiving are established. The tooth flank equation of the face gears using the new processing method is derived. To describe the tooth flank structure, the difference between the tooth flank of power skiving face gears and traditional face gears, in which the surface is obtained by involute cylindrical gears, is compared, and a tooth flank contact analysis is conducted. The feasibility of the new processing method and the correctness of the mathematical model are verified by a power skiving experiment conducted on the face gear drive of a six-axis machine tool. Finally, the influence rule of the skiving cutter parameters on the meshing performance is analyzed in the process of machining face gears, and guidance is provided for the parameter design of power skiving cutting tools for face gears.

To investigate the influence of the manufacturing parameters on mesh behaviors for harmonic gear drive, the mathematical model of slotting the circular spline was established using kinematic method based on the tooth profile of the circular spline. Considering the circular runout errors from the machine tool and slotting cutter, the influences of two kinds of circular runout errors on the transmission error for harmonic gear drive were analyzed. Then, the influences of the slotting cutter teeth number and the slotting cycles of the circular spline on the transmission error were discussed. Two circular splines were machined by two types of slotting cutters with different teeth number to verify the theoretical analysis. Results show that the influence of the machine tool's circular runout error on the transmission error is more significant than that of the slotting cutter's circular runout error. For the slotting of the circular spline with one circle, the transmission error is the smallest when the tooth number of the slotting cutter is one third of that of the circular spline. For the slotting of the circular spline with two or three circles, the transmission error is the smallest when the tooth number of the slotting cutter is two thirds of that of the circular spline. However, the transmission error of harmonic gear is the largest when the tooth number of the slotting cutter is half of that of the circular spline.

Efficient lubrication is the key to reducing tool friction and wear, decreasing cutting force and enhancing tool cutting performance. To find a more efficient way to improve the lubrication performance of the tools in high-speed cutting hard-cutting materials, YG6X cemented carbide milling inserts textured with micro-groove parallel to the main cutting edge and Fe₃O₄ nanofluids with a mass concentration of 0.5% were fabricated, the friction and wear tests and contact angle tests were carried out to investigate the coupling lubrication effects of micro-textures and nanofluids. Results obtained in this work indicated that the friction coefficient of micro-texture sample under nanofluids lubrication was reduced by 92.2% when compared with the un-textured sample under dry friction, and the contact angle of the nanofluids droplet on micro-texture surface was 72.1% lower than that of the emulsion droplet on un-textured surface. Based on the results, a series of experiments were further carried out on high-speed milling Ti6Al4V using micro-texture milling cutter under the nanofluids lubrication. The results showed that cutting forces of micro-texture milling cutters under nanofluids lubrication were reduced by 19.1%, 30.8%, 37.7% and 30.0% when compared with un-textured milling cutters under emulsion lubrication at the spindle speeds of 1000r/min, 2000r/min, 3000r/min and 4000r/min.

Mobile parallel mechanisms (MPMs), which are parallel mechanisms with moveable bases, have previously been proposed to resolve the limited workspace of conventional parallel mechanisms. However, most previous studies on the subject focused on the kinematic analysis of some specific MPMs and did not discuss a type synthesis method for MPMs. With this in mind, we propose a screw theory-based type synthesis method to find out possible 6-degrees-of-freedom (DOF) MPM structures. In our proposed method, the 6-DOF mobility is divided into 3-DOF planar motion and 3-DOF spatial motion, both of which are realized by the transmitted planar motions of the driving units. Separately, the type synthesis of the entire MPM is divided into that of the driving unit and connecting chain. To realize 3-DOF spatial motion, two methods, applying singularity configuration and adding an additional chain, are proposed as ways to restrict undesired motions for the synthesis of the connecting chain. The driving unit is synthesized via the same type-synthesis method as the connecting chain by considering the driving unit as a planar mechanism. The method used to integrate the driving unit and the connecting chain was constructed based on whether the end pair of the connecting chain should be connected with the driving unit directly or driven by it through an actuating mechanism. As a result, 284 possible types of MPM structure are suggested and four examples of MPMs with six DOFs were synthesized to verify the feasibility of the proposed method.

As one of the most common polymer materials, POM gear has been widely applied in automatic transmission boxes, intelligent house devices, etc. Though the mechanical properties of POM material have been extensively studied, the loading capacity and failure mechanism of POM gear still require to be explored. This paper experimentally investigates the loading capacity of medium-module POM gears based upon the durability test under various loading conditions. The POM gears are mated with 18CrNiMo7-6 steel pinions. The tooth wear, surface roughness, and tooth profile evolution are recorded. In the experimental results, the contact fatigue failure was observed in tooth flank of the POM gear with medium modulus under oil lubrication conditions, including tooth surface pitting and fatigue cracks. And according to the experimental durability life data, the contact fatigue S-N curve of POM gear is fitted.

In silk reeling machine, traverse mechanism is the actuator to wind the silk yarn and form a silk package. However, the current traverse mechanisms are poor in forming uniformity: they are difficult to realize winding with constant speed in axial direction for a long time, and guarantee constant forming angle and winding tension in circumferential direction. In order to improve the winding forming uniformity of silk reeling machine, a new traverse mechanism which consists of an axial forming system and a circumferential forming control system is constructed. The feature of axial forming system is that it’s driven by non-circular gear pair with free pitch curve. Through establishing axial ideal kinematic model of traverse rod and axial theoretical kinematic model of traverse rod, the pitch curve of non-circular gear pair is solved in reverse by using stepwise search method. In circumferential forming control system, the traverse rod, controlled by STM32, will move in radial direction with increase of package thickness. Based on tension analysis and wrapping angle analysis, the radial kinematic model of traverse rod is deduced by using stepwise search method as well. Finally, the silk winding experiment verifies that the new traverse mechanism can effectively improve the winding forming uniformity.

In cycling, pedaling is a combination of two pedal strokes by the left and right legs with different power. The pedaling power is transmitted from the human leg to the bike through the sprocket mechanism. However, research on sprocket design that considers the combination of two pedal strokes is limited. This paper proposes a CAD method to design a bi-ellipse sprocket that combines half different ellipses. The ellipses combination is used to accommodate the different torque between two pedals. Here, we built a sprocket prototype by adjusting the two vertical axes ratio on the bi-ellipse sprocket to be equal to the maximum torque ratio on the left and right crank. Then, we performed a pedaling comparison test between the circular sprocket and bi-ellipse sprocket prototype at the same rear-wheel rotational speed using a mountain bicycle mounted on an indoor bike trainer. In the test, the bi-ellipse prototype was also set up in eight different positions to the crank. Crank meter systems were installed on the bike to obtain the pedaling torque data and the pedaling power data on the left and right crank every 0.005 seconds. The result showed that the comparison parameter related to crank torque and power had smaller values on the bi-ellipse prototype than pedaling on the circular sprocket. Moreover, the asymmetry index of maximum torque in a specific position on the crank was lower than the circular sprocket. It can be concluded that using the bi-ellipse sprocket prototype makes pedaling more efficient, lighter, and safer to use. The proposed method can also be used as a guidance procedure to make countless bi-ellipse sprocket models.

As an advanced plastic-forming method, counter-roller spinning (CRS) is mainly applied to process large-sized, thin-walled cylinder for aerospace rocket engine. Medium carbon quenched and tempered steel 30CrMnSiA is a typical material for solid rocket motor due to its high strength, high toughness and good fatigue resistance. The determination of complex process parameters and the detection of multiple forming indexes are necessary for the study of CRS. In this paper, a finite element (FE) model for CRS of 30CrMnSiA cylinder with a diameter of 2.25 m was established and verified according to the experimental data. The effects of multiple process parameters on the forming results were studied and analyzed by orthogonal experiment. Results reveal that the thinning ratio is the most important process parameter for all the forming results. Larger thinning rate can improve production efficiency but reduce forming accuracy and require equipment to provide greater spinning force. The influence laws of process parameters on the forming accuracy and spinning force of the outside of the cylindrical parts are similar to that of the inside of the cylindrical parts. In addition, the forming accuracy error and spinning force of the inside of the cylindrical parts are smaller than that of the outside of the cylindrical parts. Thus, the forming force and positioning accuracy of the outer roller holder can be given priority when developing the CRS equipment. Based on the ANOVA results, a multivariate nonlinear regression analysis was performed on the forming results by selecting significant process parameters as independent variables. The optimal range of process parameters for obtaining good forming results was obtained by processing the regression equation.

Previously, we proposed a self-powered vibration-based structural health monitoring system for diagnosing the structural soundness of entire bridges to screen bridges requiring detailed inspection. The core part of the system is the vibration-sensing device that is in the developing phase. This part relies on the Villari effect of magnetostrictive materials. In particular, the vibration-sensing device is a dual-use device that can serve as a vibration sensor and a power generator. This paper describes the design and evaluation results of the device’s performance. Galfenol, a typical magnetostrictive material, was used. Therefore, we first investigate the relationship between the magnetic flux density variation and the compression stress with different bias magnetic fields applied to the Galfenol rod. Moreover, an adequate range of the bias magnetic field was determined to maximize the power-generation performance and sensitivity of vibration. Subsequently, the prototype of the vibration-sensing device was designed and built, and a field test was conducted. The experimental results confirmed that the device works as a vibration sensor with high resolution. The device accurately detected the natural frequency of a bridge, even when subjected to the intermittent load of passing cars. The device generated 30.3 mJ in an hour even though it is a small-sized non-resonant power generator. With such generated energy, diagnosing the structural health at least once every two days can be executed with the developed device.

Since the helical surface of the toroidal worm is a complex space surface with variable-lead, the design method and high-efficiency machining method for the consistency rough machining allowance of the toroidal worm are not perfect, which is not conducive to improving the grinding efficiency and quality of the toroidal worm. Aiming at the design and processing of the toroidal worm roughing allowance, this paper studies the design method of the toroidal worm roughing allowance surface, and proposes a machining method of the allowance surface used in an ordinary CNC lathe. First, according to the forming principle of the dual-cone enveloping toroidal worm, the helical surfaces of the multi-thread toroidal worm with a given throat tooth thickness are established. Then, each point on the helical surface is rotated by an allowance angle around the axis of the worm, and the mathematical model of the roughing allowance surface is established by setting the arc length of each point rotation equally. The designed allowance surface is discretized into a series of helical lines, and a series of helical lines are discretized into points. The cone helical line interpolation is used between two adjacent points for turning the allowance surface based on an ordinary CNC lathe. Based on the axial indexing method, different helical lines can be machined by adjusting the starting points X and Z of the tool when processing helical surfaces at different positions. Through research, the allowance equalization and rough machining of the variable-lead enveloping helical surface are realized, which provides a new method for the processing of complex and special-shaped helical surfaces.

Harmonic reducer is a transmission device with high transmission ratio and high accuracy, which is widely used in robotics and other instruments. Backlash reflects the positioning accuracy of harmonic drive, which is one of the key performances of harmonic reducer. Because the flexible bearing is a wave generator of harmonic reducer, its clearance has a great influence on the accuracy of harmonic drive. To obtain the influence of clearance on the backlash of harmonic reducer, the clearance of flexible bearing is equivalent to the backlash of gear teeth to carry out the theoretical value of the backlash of harmonic reducer. Then a new measuring instrument was set up to measure the backlash of harmonic reducer. The results show that the test value is larger than the theoretical value. The research finds that the torsional stiffness of the harmonic drive has non-linear characteristics. Then the hysteresis curve of the flexible bearing is drawn, and the four-segment stiffness values of the flexible bearing under different clearances are analyzed. Finally, the vibration equation is established based on the time-varying stiffness, and the calculation shows that the clearance also has influence on the natural frequency of the flexible bearing system and test results show that the rotation position has a great influence on the natural frequency.

In the automobile industry, bending and hemming processes are normally used to supplement car body panels. However, the Forming Limit Curve (FLC) inappropriately induces to predict the bendability in hemming process as it has a different failure mechanism and deformed sheet metals can undergo greater bending than predicted by the FLC. In this work, the newly developed Bending Limit Curve (BLC) based on strain and stress were experimentally and numerically proposed for bendability prediction tools of hemming process in assembling automotive body panels. For the experimental procedures, the BLC based on strain of dual phase steel grade DP590 with a thickness of 1.0 mm was experimentally determined by simulative tests. Firstly, the various steel sample geometries were pre-stretched using the modified Marciniak in-plane stretch-forming tests for realistic reflection with the stamping processes before hemming process. Afterwards, to establish the BLC, the pre-stretched samples were experimentally conducted on a three-point bending test. Moreover, the influence of different bending radius of 0.4 and 2.0 mm on BLC was investigated both of BLCs and Bending Limit Stress Curves (BLSCs). The obtained BLSCs were plastically calculated by using the experimental BLC data corresponding with punch plate radii, which were coupled with anisotropic yield criteria namely, Hill’48 and Yld2000-2d and the Swift hardening model. It was found that the developed BLC exhibited greater strain level than the FLC. Obviously, the higher punch radius established lower strain and stress level of BLC and BLSC, respectively. The experimental BLSCs have the similar trend of their curves which used same yield criterion. In conclusion, the BLCs and BLSCs were completely accomplished to realistically predict the bending and hemming process. The calculated BLSCs are not sensitive with non-linear strain paths which establishes before hemming process.

This study aims to develop a vision-based measurement method for machine tool vibrations and dynamic motion errors. In this study, the potential of the vision-based method in high resolution measurement is evaluated. A model fitting method is considered for the image processing that is appropriate for mechanical vibration measurement. The influence of lighting on the measurement resolution is also evaluated. In the method, the displacement of the marker attached to the object is obtained through a video captured by using a high-speed camera. To obtain the marker displacement, the center position of the marker is tracked by fitting a quadratic function to the intensity distribution of the marker. Experiments are conducted to evaluate the measurement resolution of the model fitting method. The vibration displacement of a cantilever with various amplitudes was measured using the vision based method under different lighting conditions. The measured displacement is analyzed in the frequency domain to determine the measurement resolution and noise level. In addition to the model fitting method, an edge detection method and a threshold detection method are used for the marker position detection and compared with the model fitting method. The experiment results indicate that the model fitting method has the ability to detect the minimum amplitude of 1/53 pixels that corresponds to a 3.8 μm resolution in 120 × 160 mm range.

The recognition of machining features has been considered an important technology in the development of computer-aided process planning (CAPP) systems. Various machining feature recognition methods have been devised that use the geometric information of a target shape and/or the removal volume. However, in the previous studies, geometric dimensioning and tolerancing (GD&T) data are not considered for the recognition. Model-based definition (MBD) is attracting attention as a potential solution to this problem. In MBD, GD&T data as well as notes are referred to as product and manufacturing information (PMI) and directly integrated into a CAD model as 3D annotations. This study aims to propose a machining feature recognition method that reflects PMI for CAPP, based on MBD. In this method, in addition to the previously proposed machining features, dedicated machining features are introduced to deal with a finishing operation. Reference faces to reflect the PMI are then detected from the removal volume, and the PMI is transferred from the target shape to the reference faces. When a finishing operation is required to satisfy PMI, two types of machining features are recognized corresponding to a roughing or finishing operation, respectively. The removal volume obtained from a target shape is also changed to be shifted to practically meet the PMI without modifying the target shape. It also becomes possible to refer to the PMI in operation planning because the recognized machining feature has the PMI. The results of the present case study confirm that PMI can be effectively reflected by the proposed feature recognition method for CAPP.

Humans establish embodied interactions, such as bows and handshakes, when they first greet one another and display a feeling of rapport. It is believed that humans construct a relationship that is emotionally acceptable to each other by the synchronization of their embodied rhythms through their embodied interactions. Hug behaviors are expected to synchronize embodied rhythms effectively as they are an embodied interaction where whole bodies are in contact with each other. In hug behaviors between humans and robots, the same efficiency is expected. Furthermore, when a human approaches a robot, the robot should generate a hug request motion to promote embodied interactions. Therefore, in this study, a hug robot system for the generation of hug behavior with approaching humans is developed. The hug robot system that employs a hug behavior request model generates request motion of a hug when a human approaches the robot. Furthermore, a switching hug control was developed by combining the proposed hug behavior request model with the hug behavior response model. In the switching hug control, when an approaching human requests a hug, the robot generates a response motion. However, if the approaching human does not request a hug, the robot will request one to the human. Then, in hug behaviors between a human and a robot, the motion characteristics of the robot that are preferred by majority of research participants are analyzed using the developed hug robot system.

This paper proposes a calculation method for the contact ratio of internal beveloid gear pairs with small tooth number difference (IBGPSTND) based on the finite element method (FEM). The mathematical model and finite element model of the IBGPSTND are established. The influence of the design parameters of the IBGPSTND on the contact ratio is studied. The difference between the contact ratio calculated by the analytical method and the FEM is analyzed. The results show that the number of teeth difference, the addendum coefficient, and the pitch cone angle have a greater influence on the contact ratio. Under the influence of the multi-tooth elastic meshing effect, the contact ratio of IBGPSTND calculated by the analytical method and the FEM is significantly different. The increase of the load torque will aggravate the effect of the multi-tooth elastic meshing effect and increase the contact ratio, and a larger contact ratio can effectively reduce the maximum Mises stress and increase gear meshing stiffness.

The grey relational theory is introduced into the reliability analysis of the modular pod, and the grey relational degree mathematical model is established. The module is divided according to the category of the reliability index of the pod, and the reliability parameter index of each module is evaluated. The correlation analysis of the evaluation indicators of the pod reliability module was carried out, and the correlation between the sample data line and the design standard line was explained from the perspective of proximity, and the modular reliability analysis of the pod product was realized. This research provides an economical optimal modular design scheme, which is of great significance for shortening the development cycle of pod products and improving product reliability.