Proceedings of the Institution of Mechanical Engineers,Part K: Journal of Multi-body Dynamics

Energy losses in the drivetrain are a steady topic within the automotive industry, be it to lower emissions and fulfill demands by legislation or to stay longer on the track with a single filling of the fuel tank as in motor sport applications. All of these reasons fuel the motivation to reduce these parasitic losses. In this paper, the major sources of the energy losses in a gearbox are discussed. After the discussion of the sources, the losses in a longitudinally installed manual gearbox are investigated by using both experimental measurements as well as simulation. For the simulation, convenient empirical formulas from literature are used to describe the individual loss processes and combined together to describe the friction power losses of the entire gearbox. The comparison between simulation and the extensive experimental data show good agreement.

In this paper, based on the existing manufacturing methods, the journal bearing with spherical surface texturing has been taken as the study object to establish a calculating model. With Matlab programming, effects of micro-spherical surface texturing on the performance of journal bearing have been investigated; the dynamic coefficients were obtained by solving the Reynolds equation and four Reynolds equations of perturbation pressure with the finite difference method; the influences of spherical texturing on the dynamic coefficients of journal bearing have been studied. Taking Jeffcott rotor supported by journal bearing as the research object, the influences of surface texturing on the rotor critical speed and the unbalance response have been discussed deeply. A series of performance curves were obtained and explained. The study shows that compared with smooth surface journal bearing, the load capacity of bearing with concave texturing decreases slightly and increases with convex texturing substantially. Convex and concave texturing will influence the dynamic performances of rotor, such as critical speed and unbalance respond. And such influences will change with the changing of texturing geometry parameters.

Two dynamic models are established to study the torsional vibration and noise characteristics of a power-split hybrid driveline. One is developed using mathematical rotational motion of the driveline components in matrix form. The other dynamic model of the hybrid driveline is built in the multi-body dynamic software ADAMS. The natural frequencies and vibration modes computed from the two methods show a remarkable agreement. Moreover, the noise source identification for the power-split hybrid driveline is also undertaken according to the acoustic measures on the test bench. This study can provide a valuable reference to the development of hybrid electric vehicle in the future.

Owing to orbital rotation of the rolling element complement and depending on the state of bearing preload, the dynamic stiffness of bearing alters. This causes a vibration at a frequency equivalent to the number of rolling elements multiplied by the cage speed named as variable compliance vibration, which could be much larger than the system nature frequencies. In this paper, the resonance effect induced by the variable compliance vibration of an elastic rotor is discussed. Simplified bearing and the Timoshenko elements are employed to model the system, and then cascade plots and frequency spectrums are mainly obtained as results with two types of resonance in low-speed region. Firstly, resonance of variable compliance frequency would occur while the variable compliance frequency meets the system nature frequencies, which are different in the horizontal and vertical directions. Secondly, resonance of sub-harmonic frequencies which are close to the system nature frequencies would occur while the variable compliance frequency meets the sum of system nature frequencies.

A rotor–cylindrical roller bearing system is investigated in this paper. The applied loads and moments acting on the bearings due to the bearing housing nonconcentricity are calculated by analyzing mechanics and deformation of the bearing. Taking the effect of nonconcentricity of bearing housings into consideration, an analytical vibration model for the rotor–bearing system is developed by modifying the transfer matrix method. Afterwards, this vibration model is applied in a rotor–bearing system example and the numerical solution of the model is carried out for analyzing the effects of nonconcentricity of the bearing housings on the system vibration characteristics. By simulation, some dynamic curves of the rotor–bearing system are obtained. It is found that the natural frequencies, the amplitude of unbalance response, and the position of the peak amplitude of the system vary with the increase of degree of misalignment between two bearing housings.

This paper describes the development of a new aircraft tyre model applied using a co-simulation approach for the multibody dynamic simulation of helicopter ground vehicle dynamics. The new tyre model is presented using a point follower approach that makes a novel contribution to this area by uniquely combining elements of two existing tyre models used by the aircraft industry, namely the NASA R64 model developed by Smiley and Horne and the Engineering Sciences Data Unit (ESDU) Mitchell tyre model. Before the tyre model was used with a full helicopter model, a virtual tyre test rig was used to examine the tyre and to predict the tyre forces and moments for a range of tyre states. The paper concludes by describing the successful application of the new tyre model with a full helicopter model and the simulation of representative landing, take-off and runway taxiing manoeuvres. The predictive capability of the model is demonstrated to show the open-loop ground vehicle dynamics response of the helicopter and also the ground load predictive capability for the distribution of loads through the tyres, wheels and landing gears.

Although significant attempts have been made to automate the manipulation of biological cells with atomic force microscopy, these efforts have faced many limitations and restrictions. Researchers have recently tried to measure the interacting forces in order to improve the reliability of manipulation operations with atomic force microscopy. By manipulation of micro/nanoparticles of different materials and shapes, as the target particles, in different biological environments, the interacting forces existing between these micro/nanoparticles and the biological environment will be different from those in the air medium. Therefore, in this paper, first, a general overview and simulation of the important forces acting in the biological environment was presented, and forces such as the adhesion force, hydration force and the electrostatic double-layer force were modeled and simulated in different environments (e.g. water, alcohol and blood plasma). After different biological environments (in comparison with the air medium) were explored and modeled, the manipulation operations with atomic force microscopy were simulated for different micro/nanoparticles such as gold, DNA and yeast by considering the forces existing in various biological environments. The results of manipulation in this paper indicate that in the air and liquid environments, the biological particles (DNA and yeast) will start to move after a longer time and by a higher magnitude force relative to the gold particles. This outcome is predictable, given the properties and stickiness of the biological particles. Also by comparing the obtained results, it is found that the critical force and critical time of manipulation with atomic force microscopy for gold nanoparticles slightly increase in water relative to air, which can be due to the properties of water and the existing forces in water that resist against the movement of nanoparticles. Finally, the obtained results were compared with the available empirical results. It can be seen that the obtained simulation values have a good correlation with the empirical results. The closeness of these two values confirms the validity of the performed simulation.

In this paper, an optimal path-planning method is proposed for autonomous ground vehicles in case of overtaking a moving obstacle by the application of a two-phase optimal-control problem. When the autonomous vehicle detects a moving vehicle in a proper speed and distance ahead, it decides to overtake the obstacle by executing a double-lane change manoeuvre. The path for the overtaking manoeuvre is generated by a two-phase optimal path-planning problem. The cost function of the first phase is defined in such a way that the vehicle approaches the obstacle as close as possible. In the second phase, the cost function is defined as sum of the vehicle lateral deviation from the reference path and the rate of steering angle. At the same time, the lateral acceleration of the vehicle must not exceed a specified limit. The radio pseudo-spectral method, which is a method for direct trajectory optimization using global collocation at Legendre–Gauss–Radau points, is applied for solving the two-phase nonlinear optimal-control problem. A full nonlinear vehicle model in CarSim software is used for path-tracking simulation by importing path data from a MATLAB code. The simulation results show that the generated path for the autonomous vehicle satisfies all vehicle-dynamics constraints and hence is applicable for a real autonomous vehicle.

In this paper, a type of planetary gear system in the wind turbine was studied by taking into account the actual conditions where the planetary gear system works. A nonlinear multi-gap planetary gear system finite element method model was established, and the engagement stress, the displacement, and the velocity curve with time of nodes of the planetary gear system were obtained by using explicit dynamic solution method. Under different speeds and different load, the variation of planetary gear system dynamic transmission error was then studied combined with the theory of gearing. The results showed that it is different from the dynamic transmission error of planetary gear system and planetary gear. Time-varying mesh stiffness of sun gear and the ring gear are also different along with their speed change. There are some correlation among time-varying mesh stiffness, meshing impact stress, and dynamic transmission errors. Therefore, it is suggested that the meshing stiffness and impact stress effect on the dynamic transmission error should be considered in the study of transmission error of wind turbine planetary gear system.