Search Results

The present study introduces a novel approach for achieving path tracking of an unmanned bicycle in its local body-fixed coordinate frame. A bicycle is generally recognized as a multibody system consisting of four distinct rigid bodies, namely the front wheel, the front fork, the body frame, and the rear wheel. In contrast to most previous studies, the relationship between a tire and the road is now considered in terms of tire forces rather than nonholonomic constraints. The body frame has six degrees of freedom, while the rear wheel and front fork each have one degree of freedom relative to the body frame. The front wheel exhibits a single degree of freedom relative to the front fork. A bicycle has a total of nine degrees of freedom.

A multibody model for riderless bicycle dynamics considering tire characteristics is presented. A riderless bicycle is regarded as a multibody system consisting of four rigid bodies: rear wheel, frame, front fork, and front wheel. Every two bodies are connected with a revolute joint. The mass center coordinates and Euler angles of the rigid bodies are used as the generalized coordinates to describe their positions and orientations. The system equations of motion are obtained using Lagrange equations of the first kind. Due to the existence of the three revolute constraints and the use of dependent generalized coordinates, the Lagrange multipliers are employed to account for revolute reaction forces. As for the contact between the wheel and the ground, many studies regarded the wheel as a rigid body with a knife edge, which lead to the nonholonomic constraints between the wheel and the ground.

Due to the elimination of the mechanical connection between the steering column and steering gear in the Steer-by-Wire (SBW) system, the road-feeling simulation is mainly supplied by the road-feeling motor which loads a drag torque on the steering wheel rather than the actual torque transmitted from the road. To obtain more realistic steering wheel torque, a novel feedback torque of the road-feeling motor fusion estimation method based on the Kalman filter is presented in this paper. Firstly, the model-based estimation method is utilized to estimate the aligning torque between tires and ground which is converted into the rack force through the steering system. Then the estimated rack force is used as the observed data for the Kalman Filter of the sensor-based method and the Kalman Filter-based fusion estimation method is resulted, through which the more realistic feedback torque of the road-feeling motor can be obtained.

Electric vehicles driven by in-wheel-motor have the advantages of compact structure and high transmission efficiency, which is one of the most ideal energy-saving, environmentally friendly, and safe driving forms in the future. However, the addition of the in-wheel-motor significantly increases the unsprung mass of the vehicle, resulting in a decrease in the mass ratio of the vehicle body to the wheel, which will deteriorate the ride comfort and safety of the vehicle. To improve the vibration performance of in-wheel-motor driven vehicles, a semi-active inerter-spring-damper (ISD) suspension with in-wheel-motor (IWM) dynamic vibration absorber (DVA) of the electric wheel is proposed in this paper. Firstly, a structure of in-wheel-motor DVA is proposed, which converts the motor into a dynamic vibration absorber of the wheel to suppress the vibration of the unsprung mass.

The rubber bushing is the key component to suppress vibration in the suspension system, an accurate constitutive model of rubber bushing should capture the amplitude and frequency dependency. Based on the lumped parameter model, three types of rubber bushing models are applied and compared, including the common Kelvin-Voigt model. To evaluate the model parameter and suitable frequency range, the quasi-static and dynamic tests have been performed. Comparing with the testing result, the fractional Kelvin-Voigt model combined with Berg’s friction has the minimum relative error of dynamic stiffness on the whole. Finally, two examples of chassis bushing under different loading conditions are presented. The rubber force and deflection are analyzed in both the time domain and the frequency domain, and the results show the difference of stiffness and hysteresis loop relative to frequency.

In the petroleum and gas industry, cargo truck is one of the most important ways to transfer the skid-mounting from the manufacturer to the job location. Under the condition of bumpy road surface, the random vibration from the ground can easily cause the resonance of the internal equipment components of the skid-mounting, produce large deformation in the pipeline and equipment connection, and even the equipment will be damaged. In this paper, the finite element analysis model and dynamic rigid flexible coupling model of a TEG (Triethyleneglycol) dehydration unit regeneration skid-mounting are established by using the finite element analysis and multi-body dynamics software. The modal analysis of the skid and the vibration of the whole vehicle under different road excitation and driving conditions are carried out. Two solutions are proposed to improve the anti-vibration ability of the skid, and comparative analysis is made.

Increased focus on vehicle comfort and ride has led the automotive industry to look into low vibration, noise and hardness alternative designs for powertrain system components. In this paper, the vibration theory and dynamic vibration absorber (DVA) theory is presented. The modal analysis of propeller shaft assembly has been accomplished. Based on dynamic vibration absorber principle, performance parameters of dynamic vibration absorber are matched and structure is also designed. LMS equipment is applied to verify the natural frequency of absorber samples. The matching of stiffness and damping of DVA is presented. The dynamic response of drive shaft system based on the mass ratio of DVA is researched in this paper. Results from simulations and tests indicates that the amplitude of propeller shaft resonance can be effectively reduced by attaching a DVA to the long propeller shaft.

The imbalance of propeller shaft is an excitation to the vehicle structure and causes noise and vibration. This paper presents an experimental study of effects of propeller shaft imbalance on vehicle vibration characteristics. A two-piece propeller shaft with unbalance is used in real vehicle test. The vehicle vibration is characterized by accelerations of the cabin floor and of the bearing which supports the propeller shaft. Through the experiment, some interesting phenomena are observed.

This paper focuses on dynamic analysis and frame optimization of a FSAE racing car frame. Firstly, a Multi-Body Dynamic (MBD) model of the racing car is established using ADAMS/Car. The forces and torques of the mechanical joints between the frame and suspensions are calculated in various extreme working conditions. Secondly, the strength, stiffness and free vibration modes of the frame are analyzed using Finite Element Analysis (FEA). The extracted forces and torques in the first step are used as boundary conditions in FEA. The FEA results suggest that the size of the frame may be not reasonable. Thirdly, the size of the frame is optimized to achieve minimized weight. Meanwhile the strength and stiffness of the frame are constrained. The optimization results reveal that the optimization methodology is powerful in lightweight design of the frame.

The sewing machine has been widely used in various aspects of life and it is essential to study its kinematic and dynamic characteristics. A dynamic model of flexible multi-link mechanism for sewing machine including joints with clearance is established to analysis its dynamic response in the present work. The configuration of the sewing machine mainly included five subsystems, feeding mechanism, needle bar mechanism, looper mechanism, shearing mechanism and adjusting mechanism. Since the sewing machine mainly consist of linkage mechanisms that are connected by revolute joints and translational joints, the existence of clearances in the joints and the flexibility of crankshafts and linkage are important factors that affect the dynamic performance. Even little clearance can lead to vibration and fatigue phenomena, lack of precision or even make overall behavior as random.

The powertrain mounting system (PMS) plays an important role in improving the NVH (Noise, Vibration, Harshness) quality of the vehicle. In all running conditions of a vehicle, the displacements of the powertrain C.G. should be controlled in a prescribed range to avoid interference with other components in the vehicle. The conventional model of PMS is based on vibration theory, considering the rotation angles are small, ignoring the sequence of the rotations. However, the motion of PMS is in 3D space with 3 translational degrees of freedom and 3 rotational degrees of freedom, when the rotation angles are not small, the conventional model of PMS will cause errors. The errors are likely to make powertrain interfering with other components. This paper proposes a rigid body mechanics model of the powertrain mounting system. When the powertrain undergoes a large rotational motion, the rigid body mechanics model can provide more accurate calculation results.

Interval inverse problems can be defined as problems to estimate input through given output, where the input and output are interval numbers. Many problems in engineering can be formulated as inverse problems like vehicle suspension design. Interval metrics, instead of deterministic metrics, are used for the suspension design of a vehicle vibration model with five degrees of freedom. The vibration properties of a vehicle vibration model are described by reasonable intervals and the suspension interval parameters are to be solved. A new interval inverse analysis method, which is a combination of Chebyshev inclusion function and optimization algorithm such as multi-island genetic algorithm, is presented and used for the suspension design of a vehicle vibration model with six conflicting objective functions. The interval design of suspension using such an interval inverse analysis method is shown and validated, and some useful conclusions are reached.

Nowadays, studying the human body response in a seated position has attracted a lot of attention as environmental vibrations are transferred to the human body through floor and seat. This research has constructed a multi-body biodynamic human model with 17 degrees of freedom (DOF), including the backrest support and the interaction between feet and ground. Three types of human biodynamic models are taken into consideration: the first model doesn't include the interaction between the feet and floor, the second considers the feet and floor interaction by using a high stiffness spring, the third one includes the interaction by using a soft spring. Based on the whole vehicle model, the excitation to human body through feet and back can be obtained by ride simulation. The simulation results indicate that the interaction between feet and ground exerts non-negligible effect upon the performance of the whole body vibration by comparing the three cases.

The main purpose of this research is to investigate the optimal design of pipeline diameter in an air brake system in order to reduce the response time for driving safety using DOE (Design of Experiment) method. To achieve this purpose, this paper presents the development and validation of a computer-aided analytical dynamic model of a pneumatic brake system in commercial vehicles. The brake system includes the subsystems for brake pedal, treadle valve, quick release valve, load sensing proportional valve and brake chamber, and the simulation models for individual components of the brake system are established within the multi-domain physical modeling software- AMESim based on the logic structure. An experimental test bench was set up by connecting each component with the nylon pipelines based on the actual layout of the 4×2 commercial vehicle air brake system.

In this paper, a new computational method is provided to identify the uncertain parameters of Load Sensing Proportional Valve (LSPV) in a heavy truck brake system by using the polynomial chaos theory. The simulation model of LSPV is built in the software AMESim depending on structure of the valve, and the estimation process is implemented relying on the experimental measurements by pneumatic bench test. With the polynomial chaos expansion carried out by collocation method, the output observation function of the nonlinear pneumatic model can be transformed into a linear and time-invariant form, and the general recursive functions based on Newton method can therefore be reformulated to fit for the computer programming and calculation. To improve the estimation accuracy, the Newton method is modified with reference to Simulated Annealing algorithm by introducing the Metropolis Principle to control the fluctuation during the estimation process and escape from the local minima.

This paper presents the dynamic and analysis models of a typical synchronizer, which are mainly used to analyze the sensitivity of parameters of synchronizer on the gear shift performance. Because there are so many parameters namely coefficient of friction, cone angle, mean radius, blocker angle, etc, affected the synchronizer performance, which the times of experience will increase in a geometrical ratio if tested them one by one, it is almost impossible to evaluate all parameters by experience alone. Due to virtual prototype technology, the synchronizer parameterized virtual models can be built for the synchronizer studies. The parameterized virtual models of the typical synchronizers are developed with ADAMS. Then the gear shift process is simulated and analyzed for the given input parameters respectively. The models also predict the shift time and the peak of the shift force, and the model is validated by the good correlation between simulation results and test data.

In the present study, the research of the exhaust system is performed in three steps. In the first step, the average driving degree of freedom displacement (ADDOFD) is calculated by the free modal analysis of the exhaust system. It is easy to find the reasonable location of the hanger according to the value of the ADDOFD, since it represents the relative size of some DOF's response displacement at excitation state. The second of which is to analyse the vibration isolation performance of the exhaust system based on the first step. The dynamic analysis of the exhaust system together with the powertrain is studied, by which way the unit sinusoidal excitation is applied at the powertrain's mass centre, so that the response force at the hanger can be obtained. Finally, the relationship between the constrained model of the exhaust system and the stiffness of the hanger is investigated, which is significant in engineering.

As there are a variety of uncertainty contained in dynamic systems, this paper presents a method to identify the uncertain parameters of Load Sensing Proportional Valve in a heavy truck brake system. This method is derived from polynomial chaos theory and uses the maximum likelihood approach to estimate the most likely value of uncertain parameters, such as equivalent bearing area diameter of the diaphragm, preload of return spring and so on. The maximum likelihood estimates are obtained through minimizing the cost function derived from the prior probability for the measurement noise. Direct stochastic collocation has been shown to be more efficient than Galerkin approach in the simulation of systems with large number of uncertain parameters. The simulation model of Load Sensing Proportional Valve is built in software AMESim based on logic structure of the valve. The uncertain parameters are estimated through the simulation results which are treated as measurements.

This paper deals with the robust design of the Load Sensing Proportional Valve (LSPV). To find out the parameters which have main effect on the performance of the LSPV, the DOE based on orthogonal experiment is carried out utilizing the LSPV model built in AMESim environment. In order to save computation expense, the RSM technique is used to approximate the optimal objectives and constraints. Then a robust design methodology using multi-objective evolutionary algorithm (MOEA) is performed and a set of non-dominated solutions are therefore obtained. With specified assessments, feasible solutions can therefore be selected from the entire field of the Pareto optimal solutions. The validation is made by Monte Carlo Simulation Technique in terms of the robustness of the feasible solutions.

The automatic mechanical transmission (AMT) was designed by automobile manufacturers to provide a better driving experience, especially in cities where congestion frequently causes stop-and-go traffic patterns. It uses electronic sensors, processors, hydraulic or pneumatic actuators execute clutch actuation and gear shifts on the command of the driver. Such systems coupled with various physical domains have great influence on the dynamic behavior of the vehicle, such as shift quality, driveability, acceleration, etc. This paper presents a detailed AMT model composed of various components from multi-domains like mechanical systems (clutch, gear pair, synchronizer, etc.), pneumatic actuator systems (clutch actuation system, gear select actuation system, gear shift actuation system, etc.). Various components and subsystem models, such as the vehicle, engine, AMT, wheels, etc., are integrated into an overall vehicle system model according to the transmission power flow and control logic.