Analytical calculation models for mesh stiffness and backlash of spur gears under temperature effects

The temperature has a great contribution to the mesh stiffness and backlash of the gear pair. Presence of thermal deformation caused by temperature will complicate the gear teeth interaction. In this paper, the thermal time-varying stiffness model and thermal time-varying backlash model are proposed with the consideration of tooth profile error and total thermo-elastic deformation consists of the teeth deformation, teeth contact deformation, and gear body-induced deformation. The key parameters of thermo-elastic coupling deformation affected by temperature are calculated. Based on the proposed models, the influencing mechanism of temperature on the tooth profile error, mesh stiffness, total deformation, and backlash are revealed. The effects of shaft radius and torque load on the thermal stiffness and thermal backlash are studied. The proposed thermal stiffness and backlash calculation model are proven to be more comprehensive and the correctness is validated.

Application of Multilayer Observer for a Drive System with Flexibility

This paper proposes a new estimation algorithm based on the Luenberger observer methodology and multilayer concept. The proposed multi-layer Luenberger observer (MLO) is implemented in the control structure designated for a two-mass system. Two types of aggregation mechanism are evaluated in the paper. The MLO ensures better estimation quality of the mechanical state variables: motor speed, shaft torque, load speed and load torque, as compared to the classical single observer. The more accurate estimated states, the more precise closed-loop control is guaranteed. MLO is designated for the system where initial conditions of the plant are not known or the state variables can change rapidly (load torque in the considered case). The estimation algorithm and control strategy is evaluated through simulation and experimental tests. The obtained results confirm efficiency of the proposed MLO.

Research on Loading Method of Tractor PTO Based on Dynamic Load Spectrum

The torque load spectrum is an important basis for the strength design and durability test verification of tractor power take-off (PTO), and the performance and reliability of tractor PTO directly affect the quality and efficiency of agricultural operations. In this paper, taking the PTO torque load as the object, a PTO loading method based on the dynamic load spectrum acquired in the actual field work was proposed in this paper. Based on the Peak Over Threshold model, the extrapolation of the PTO load spectrum was realized, and the load spectrum throughout the whole life cycle was obtained. On the basis of this, the mobile tractor PTO loading test bench and Fuzzy-Proportional-Integral-Derivative (Fuzzy-PID) controller were developed to achieve the dynamic loading of the PTO load spectrum, and the dynamic characteristics were analyzed and verified by the simulation and laboratory test. The results showed that with the time domain extrapolation method, the load extreme value was expanded from (63.24, 469.50) to (60.88, 475.18), and the coverage was expanded by 1.98%. By comparing with the fitting results, statistical characteristics and rain flow counting results, the load spectrum extrapolation method was effective. In addition, the response time of simulation and laboratory test were 0.05s and 0.75s, respectively; the maximum error was 1.77% and 4.03%, respectively; and the goodness of fit was 16.78 N·m, which indicated that the PTO loading test bench, can accurately restore the dynamic loading of the tractor and the Fuzzy-PID controller had better accuracy and stability. It would provide a reference for the practical application of PTO load spectrum of the tractors.

Development and Characterization of a Modular Soft Actuator Enabled Elbow Exoskeleton for Assistive Movements

Exoskeletons are poised to provide motion assistance to aid in rehabilitation and compensate for muscle weaknesses, augment human performance, and reduce repetitive stress injuries in healthcare, industry, and occupation settings, respectively. Soft actuator enabled systems are gaining widespread attention due to their mechanical simplicity, low weight, and compliance to the human body. Regardless of promises shown, the progress for these systems is slow due to a wide variety of actuator types and geometries, which complicate designs and model predictive performance to create application-specific systems. Learning from conventional hard robotic actuator approaches, this paper investigates a modular actuator concept that can be used for creating many exoskeletons and is easily customized for fitting different sized humans, joint types, and application scenarios. The preliminary investigation details the development of an elbow exoskeleton by implementing a modular corrugated diaphragm actuator arranged in a serial configuration. Numerical simulation and experimental evaluations were carried out to investigate the torque, load-bearing, and motion characteristics of the exoskeleton. Results confirmed the viability of the concept by showing that the exoskeleton can provide assistive motion to a forearm and hand of average weight. Additionally, the exoskeleton is able to apply continuous passive motion to an elbow joint, which can be used in rehabilitation settings.

Simulative investigation of wind turbine gearbox loads during power converter fault

Three phase short circuit power converter faults in wind turbines (WT) result in highly dynamic generator torque reversals, which lead to load reversals within the drivetrain. Dynamic load reversals in combination with changing rotational speeds are, for example, critical for smearing within roller bearings. Therefore, an investigation of the correlation between three phase short circuit converter faults and drivetrain component failures is necessary.Due to the risk of damage and the resulting costs, it is not economically feasible to extensively investigate three phase short circuit converter faults on test benches. Valid WT drivetrain models can be used instead. A WT drivetrain model, which has been developed and validated in a national project at the CWD, is used and a three phase short circuit converter fault is implemented. In this paper, the resulting torque load on the drivetrain for a three phase short circuit converter fault in rated power production is presented. This converter fault leads to a highly dynamic reversing electromagnetic torque which exceeds the rated torque by a factor of three. As a result the load on the rotor side high speed shaft (HSS) bearing oscillates and increases by around 15 per cent compared to rated power production. Simultaneously the rotational velocity of the HSS oscillates with an amplitude of 10 rpm. Therefore an increase in the risk of smearing is expected.

Strength Analysis Plastic Deformed Centrifugal Pumps

The G-3503 centrifugal pump functions to flow Diethanolamine fluid with a viscosity of 380 Cp which functions to reduce H2S and CO2 levels in natural gas. When operating, the pump shaft experiences a torque load which causes the shaft to be twisted by 80. From the exact and finite element analysis results, the shear stress that occurs on the shaft is greater than the shear stress of the shaft material. Thus, the shaft is deformed plastically. The shear stress that occurs is 164 MPa

The Spinebot—A Robotic Device to Intraoperatively Quantify Spinal Stiffness

Degenerative spine problems and spinal deformities have high socio-economic impacts. Current surgical treatment is based on bony fusion that can reduce mobility and function. Precise descriptions of the biomechanics of normal, deformed, and degenerated spinal segments under in vivo conditions are needed to develop new approaches that preserve spine function. This study developed a system that intraoperatively measures the three-dimensional segmental stiffness of patient's spine. SpineBot, a parallel kinematic robot, was developed to transmit loads to adjacent vertebrae. A force/torque load cell mounted on the SpineBot measured the moment applied to the spinal segment and calculated segmental stiffnesses. The accuracy of SpineBot was characterized ex vivo by comparing its stiffness measurement of five ovine specimens to measurements obtained with a reference spinal testing system. The SpineBot can apply torques up to 10 N·m along all anatomical axes with a total range of motion of about 11.5 deg ± 0.5 deg in lateral bending, 4.5 deg ± 0.3 deg in flexion/extension, and 2.6 deg ± 0.5 deg in axial rotation. SpineBot's measurements are noisier than the reference system, but the correlation between SpineBot and reference measurements was high (R2 > 0.8). In conclusion, SpineBot's accuracy is comparable to that of current reference systems but can take intraoperative measurements. SpineBot can improve our understanding of spinal biomechanics in patients who have the pathology of interest, and take these measurements in the natural physiological environment, giving us information essential to developing new “nonfusion” products.

Vibration characteristics of triple-gear-rotor system in compressed air energy storage under variable torque load

This paper focuses on the effects of the off-design operation of CAES on the dynamic characteristics of the triple-gear-rotor system. A finite element model of the system is set up with unbalanced excitations, torque load excitations, and backlash which lead to variations of tooth contact status. An experiment is carried out to verify the accuracy of the mathematical model. The results show that when the system is subjected to large-scale torque load lifting at a high rotating speed, it has two stages of relatively strong periodicity when the torque load is light, and of chaotic when the torque load is heavy, with the transition between the two states being relatively quick and violent. The analysis of the three-dimensional acceleration spectrum and the meshing force shows that the variation in the meshing state and the fluctuation of the meshing force is the basic reasons for the variation in the system response with the torque load. In addition, the three rotors in the triple-gear-rotor system studied show a strong similarity in the meshing states and meshing force fluctuations, which result in the similarity in the dynamic responses of the three rotors.

Load calculation and strength analysis of floating garbage cleaning equipment

In order to alleviate the problem that there is increasingly floating garbage pollution on the sea, this paper proposes a new design of floating garbage cleaning equipment. This equipment is a slender structure, and whether its structural strength can meet the design requirements requires special attention. In order to ensure the rationality and safety of the design, load calculation and strength analysis are carried out based on the design wave method. The calculation results show that the longitudinal torque load of this equipment is the largest, which is 2.5 times of the second largest vertical bending moment. At the same time, there are three large stress areas in the floating structure, which are the connection between the pontoon and the connecting buntons, the connecting buntons intersecting with the Y axis and the pontoons on both sides. For the abovementioned high-stress areas, a structural strengthening plan is proposed. After the improvement, the stress in the high-stress areas of the structure is significantly reduced, with a maximum reduction of 52%. The strength of the improved structure meets the design requirements. The research results of this paper can provide relevant references for the development of floating garbage cleaning equipment in the future.