Rozprawy doktorskie na temat „DOF QUARTER CAR MODEL”

This thesis deals by the design of 1/4 car model for testing vehicle dampers, which can be used to simulate the real suspension of a vehicle wheel (up to a maximum car weight of 1,970 kg) and the so-called linear wheel suspension. A linear mathematical 1/4 car model with 2 DOF (Degrees Of Freedom) and data from literature search are used to design and derive the basic parameters of the device. The thesis contains a description of the linear mathematical model and its outputs (acceleration of the sprung mass and forces acting on the sprung mass), description of designed device, descriptions of created simulations (static, modal and harmonic analysis in ANSYS Workbench 2020 R2) and conceptual design of the modifications this device for another possible use for testing of bicycles.

This thesis presents the study of a quarter car model which consists of a two-degree-of-freedom (2 DOF) with a linear spring and a nonlinear spring configuration. In this thesis, the use of non-linear vibration attachments is briefly explained, and a survey of the research done in this area is also discussed. The survey will show what have been done by the researches in this new field of nonlinear attachments. Also, it will be shown that this topic was not extensively researched and is a new type of research where no sufficient experimental work has been applied. As an application, a quarter car model was chosen to be investigated. The aim of the Thesis is to validate theoretically and experimentally the use of nonlinear springs in a quarter car model. Design the new type of suspension and insert it in the experimental set up, built from the ground up in the laboratory. A novel criterion for optimal ride comfort is the root mean square of the absolute acceleration specified by British standards ISO 2631-1997. A new way to reduce vibrations is to take advantage of nonlinear components. The mathematical model of the quarter-car is derived, and the dynamics are evaluated in terms of the main mass displacement and acceleration. The simulation of the car dynamics is performed using Matlab® and Simulink®. The realization of vibration reduction through one-way irreversible nonlinear energy localization which requires no pre-tuning in a quarter car model is studied for the first time. Results show that the addition of the nonlinear stiffness decreases the vibration of the sprung mass to meet optimal ride comfort standards. As the passenger is situated above the sprung mass, any reduction in the sprung mass dynamics will directly have the same effect on the passenger of the vehicle. The future is in the use of a nonlinear suspension that could provide improvement in performance over that realized by the passive, semi active and active suspension. The use of a quarter car model is simple compared to a half car model or a full car model, furthermore in the more complex models you can study the heave and the pitch of the vehicle. For the initial study of the nonlinear spring the quarter car model was sufficient enough to study the dynamics of the vehicle. Obtaining an optimum suspension system is of great importance for automotive and vibration engineer involved in the vehicle design process. The suspension affects an automobile’s comfort, performance, and safety. In this thesis, the optimization of suspension parameters which include the spring stiffness and damper coefficient is designed to compromise between the comfort and the road handling. Using Genetic algorithm an automated optimization of suspension parameters was executed to meet performance requirements specified. Results show that by optimizing the parameters the vibration in the system decreases immensely.

The design, fabrication, and testing of a quarter-car facility coupled with various control algorithms are presented in this thesis. An experimental linear tubular motor, capable of producing a 52-N force, provides control actuation to the model. Controllers consisting of two designs were implemented: a classical controller employing lead and lag networks and a state-space feedback design. Each design was extensively simulated to screen for receptiveness to actuation force limitations and robustness regarding the inexact tire modeling. The goal of each controller was to minimize the acceleration of the sprung mass in the presence of simulated road disturbances, modeled by both sinusoidal and step input excitation wheels. Different reference velocity inputs were applied to the control scheme. Responses to a zero reference were juxtaposed to those that resulted from tracking a reference built off a model that incorporated inertial-frame damping attached to the sprung mass. The outcome of this comparison was that low-frequency disturbances were attenuated better when tracking a zero reference, but the reference relaxation introduced by the inertialframe damping model allowed for better-attenuated high frequency signals. Employing an inertial-frame damping value of 250 N-s/m, the rejected frequency component of the system response synchronous with the disturbance input excitation of 40 rad/s bettered by 33% and 28% when feeding control force from the classical controller and state-space controller, respectively. The experimental analysis conducted on the classical and state-space controllers produced sinusoidal disturbance rejection of at worst 50% within their respective bandwidths. At 25 rad/s, the classical controller was able to remove 80% of the base component synchronous with the disturbance excitation frequency, while the state-space controller filtered out nearly 60%. Analysis on the system's ability to reject step disturbances was greatly confounded with the destructive lateral loading transferred during the excitation process. As a result, subjection to excitation could only occur up to 25 rad/s. At the 20 rad/s response synchronous to the disturbance excitation, the classical and state-space controllers removed 85% and 70% of the disturbance, respectively. Sharp spikes in timebased amplitude were present due to the binding that ensued during testing.

This diploma thesis studies the use of air springs for race car, precisely Formula Student race car. Research part of the thesis deals with choosing suitable air spring for given application. In practical part, there is computation of parameters for appropriate setting of air spring, so it will comply with the rules of Formula Student. There is also simulation of air spring functionality in real use.

The diploma thesis deals with the analysis of the effects of shock absorber wear on the driving dynamics of the vehicle. Furthermore, a quarter model of the car was created in the Simulink software, where a procedure for evaluating the condition of the shock absorber while driving the vehicle was created. This procedure was subsequently validated on real measured data from the Hummer H3 car.

With the development of the embedded application and driving assistance systems, it becomes relevant to develop parallel mechanisms in order to check and to diagnose these new systems. In this thesis we focus our research on one of this type of parallel mechanisms and analytical redundancy for fault diagnosis of an automotive suspension system. We have considered a quarter model car passive suspension model and used a parameter estimation, ARX model, method to detect the fault happening in the damper and spring of system. Moreover, afterward we have deployed a neural network classifier to isolate the faults and identifies where the fault is happening. Then in this regard, the safety measurements and redundancies can take into the effect to prevent failure in the system. It is shown that The ARX estimator could quickly detect the fault online using the vertical acceleration and displacement sensor data which are common sensors in nowadays vehicles. Hence, the clear divergence is the ARX response make it easy to deploy a threshold to give alarm to the intelligent system of vehicle and the neural classifier can quickly show the place of fault occurrence.

The aim of this master’s thesis is to evaluate the effect of shock absorber on vehicle limits. At the beginning of the thesis, shock absorber properties were described. Then computational model was created and manoeuvres for shock absorber behaviour were defined. Created mathematical model is based on quarter model of a car and excitation in form of road with a random profile is an essential part of the model. This model was used for evaluation of heave. After heave analysis, shock absorber behaviour during drive was investigated. Drive conditions were defined as set of handling manoeuvres. For the drive investigation, complete multibody virtual model of racing car was used. Based on drive investigation analysis, optimal damping characteristics for each manoeuvre were found. Furthermore, each optimal characteristic was compared for different manoeuvres. Obtained results were compared. As a conclusion, compromise damping characteristic was suggested with the aim to fit the combination of all defined drive conditions. Final part of the thesis was aimed at validation of the computational model. Data measured during real drive were used as an input for this validation.

The diploma thesis focuses especially on a design of a way for evaluating roughness in road profile, which affects driving characteristics of a car and a ride. In the theoretical part of the thesis are mentioned the most used methods and tools for road roughness analysis in the world. For the purposes of this thesis an experimental measuring were undertaken in order to obtain data for the own design of a road profile analysing system.

The object of this master thesis is testing of vehicle using four post rig. The main goal is to make a research about testing and tuning vehicle characteristics on four post rig in order to implement them for testing of TU Brno Racing’s Formula Student racecar. The main method of testing, input signals and measurement description are presented in this thesis. The different methods of analysis of testing data to find best tuning of damper and spring stiffness for different race disciplines are described. In the last part of this work, quarter car model and multibody model in MSC Adams Car is created. Input parameters of model are based on measurements from real car/ component testing, including damper characteristics and static tire radial stiffness for best fit with the characteristics of real vehicle. The measurements themselves were also described in separate chapter of this thesis. The last but not the least goal was to compare these simulations with measurements, made od real four post rig in order to decide whether car model is suitable for racecar development.

The master thesis deals with design, manufacturing and testing of a prototype magnetorheological damper developed for Formula Student vehicle. The aim was to design and test the damper with similar damping properties to the vehicle as a conventional damper has. Target force-velocity curves were set using quarter car model and evaluated comparing minimal contact force of a tyre for conventional and newly developed damper characteristics. Structural analysis of designed parts, hydraulic and static magnetic analysis were performed. Manufacturing of a specific part magnetorheological damper part was described – piston. Manufactured prototype damper characteristics were evaluated.

In this thesis, the feasibility to integrate an brake disc and electric machine is investigated. In wheel motors (IWMs) have several advantages, such as saving space in the vehicle, individual and direct control at the wheels and the absence of a mechanical transmission. However, today’s IWMs are heavy and, thus, negatively affect the driving performance of the vehicle due to the increase of the unsprung mass. By integrating an already existing part in the wheel, this increase of the unsprung mass can be minimized. The brake disc manages high temperatures, a significant wear in rough environ-ment, which puts high demands on the rotor. The second part of the machine, the stator, will be significantly affected by the high temperatures of the rotor. The temperatures of the stator are transferred by convection, conduction and radiation from the rotor or brake disc. Liquid cooling of the stator back is analyzed as a potential solution for handling the high temperatures. In order to analyze the feasibility of the concept, thermal, electric and mechanical modelling has been used. The evaluation whether it is possible or not to integrate the brake disc has been with regard to the results of weight, cost, thermal tolerance and electric performance.
I detta arbete undersöks möjligheten att integrera en bromsskiva med elmaskin. Hjul-motorer har flera fördelar, bland annat sparas utrymme i själva bilen, individuell kontroll samt drivning av hjulen utan mekaniska transmissioner. Men hjulmotorer som kan användas idag väger oftast så pass mycket att den odämpade massan ökar kritiskt och köregenskaper av fordonet då blir lidande. Genom att integrera en befintlig del i hjulet kan ¨okningen av odämpade massan minskas. Att använda bromsskivan som rotor, kräver att denna tål temperaturer ¨over 500◦C samt påfrestningar och slitage som en vanlig mekanisk friktionsbroms måste uthärda. Den andra delen av maskinen, statorn kommer även denna att påverkas av de höga temperaturerna av bromsskivan som kommer ledas via konvektion, konduktion och strålning. Möjligheten att kyla statorn med vätska och om detta är tillräckligt undersöks. För att analyserna genomförbarheten av projektet har termiska, elektriska och mekaniska modeller använts. Resultaten har analyserats där maskinens vikt, kostnad, termisk tålighet och elektrisk prestanda har legat till grund för bedömningen om lösningen; att integrera en broms-skiva med elmaskin är rimlig eller ej.

Suspension system plays most significant role in supporting the vehicle weight and isolating vehicle body from road shocks and vibrations. The aim of suspension system is to suppress uncomforting situations from road unevenness to driver and passengers and to provide road handling and stability of vehicles. The aim of this research work is to design different types of active controller for active suspension system. By using mathematical modelling 2 DOF and 3 DOF quarter car model are designed. The objective is to determine a control strategy to achieve better road quality and ride comfort by delivering better performance with respect to seat acceleration, seat displacement, suspension deflection, sprung mass displacement, tire deflection in terms of peak overshoot, settling time etc. Four different active controllers are designed using 2 DOF quarter car model as well as 3 DOF quarter car model to compare the performance of Four controllers with the passive suspension system. The Four controllers designed are PID, Fuzzy logic controller ,Fuzzy PID controller and Linear Quadratic Controller (LQR). Three different road profiles such as Step, Sine and Band limited white noise are taken as input disturbances. In this work, MATLAB/SIMULINK software is used for simulation purpose and simulation result demonstrate that active suspension system shows better results in comparison to passive suspension system with reference to body acceleration, suspension deflection, tire deflection. Also the result of comparison shows that Fuzzy PID controller based active suspension system gives better result and stability as compared to other active controllers and passive model.

碩士
龍華科技大學
工程技術研究所
102
This thesis aimed to design and control of a novel active vehicle suspension for a quarter-car model. The test bench mainly consists of two MacPherson suspension components, one pneumatic cylinder, and one pneumatic muscle based active suspension. The pneumatic cylinder is used to produce the desired simulation of bumpy road surfaces. This thesis used the PID(Proportional Integral Differential) model system, to design an PID mode controller of the pneumatic-muscle active vehicle suspension system. The controller design was practically applied to the system. To provide the better riding comfort and driving controllability. The experimental results indicated that under the compensation of the PID mode controller, the active vehicle suspension system showed good results in vibration reduction and vibration inhibition on different bumpy road surfaces.

Suspension systems and wheels play a critical role in vehicle dynamics performance of a car in areas such as ride comfort and handling. Lumped parameter models (LPMs) are commonly used for assessing the performance of vehicle suspension systems. However, there is a lack of clarity with regard to the relative capabilities of different LPM configurations. A comprehensive comparative study of three most commonly used LPMs of increasing complexity has been carried out in the current work. The study reported here has yielded insights into the capabilities of the considered LPMs in predicting response time histories which may be used for assessing ride comfort. A shortcoming of available suspension system models appears to be in representation of harsh situations such as jounce movement which cause full compression of springs leading to ‘jerks’ manifested as high values of rate of change of acceleration of sprung mass riding on a wheel. In the current research work, a modified nonlinear quarter-car model is proposed to account for the contact force that results in jerk-type response. The numerical solution algorithm is validated through the simulation of an impact test on a car McPherson strut in a Drop Weight Impact Testing Tower developed in CAR Laboratory, CPDM. This is followed by a detailed comparison of HCM and QCM to examine their suitability for such analysis. For decades, wheel bearings in vehicles have been designed using simplified analytical approaches based on Hertz contact theory and test data. In the present work, a hybrid approach has been developed for assessing the load bearing capacity of a wheel ball bearing set. According to this approach, the amplitude of dynamic wheel load can be obtained from a lumped parameter analysis of a suspension system, which can then be used for detailed static finite element analysis of a wheel bearing system. The finite element modelling approach has been validated by successfully predicting the load bearing capacity of an SKF ball bearing set for an acceptable fatigue life. For the first time, using a powerful commercial explicit finite element analysis tool, a detailed dynamic analysis has been carried of a deep groove ball bearing with a rotating inner race. The analysis has led to a consistent representation of complex motions consisting of rotations and revolutions of rolling elements, and generated insights into the stresses developed in the various components such as balls and races. In conclusion, a simple yet effective fuzzy logic-based yaw control algorithm has been presented in the current research. According to this algorithm, two inputs i.e. a yaw rate error and a driver steering angle are used for generating an output in the form of an additive steering angle which potentially can aid a driver in avoiding straying from an intended path.

Suspension systems and wheels play a critical role in vehicle dynamics performance of a car in areas such as ride comfort and handling. Lumped parameter models (LPMs) are commonly used for assessing the performance of vehicle suspension systems. However, there is a lack of clarity with regard to the relative capabilities of different LPM configurations. A comprehensive comparative study of three most commonly used LPMs of increasing complexity has been carried out in the current work. The study reported here has yielded insights into the capabilities of the considered LPMs in predicting response time histories which may be used for assessing ride comfort. A shortcoming of available suspension system models appears to be in representation of harsh situations such as jounce movement which cause full compression of springs leading to ‘jerks’ manifested as high values of rate of change of acceleration of sprung mass riding on a wheel. In the current research work, a modified nonlinear quarter-car model is proposed to account for the contact force that results in jerk-type response. The numerical solution algorithm is validated through the simulation of an impact test on a car McPherson strut in a Drop Weight Impact Testing Tower developed in CAR Laboratory, CPDM. This is followed by a detailed comparison of HCM and QCM to examine their suitability for such analysis. For decades, wheel bearings in vehicles have been designed using simplified analytical approaches based on Hertz contact theory and test data. In the present work, a hybrid approach has been developed for assessing the load bearing capacity of a wheel ball bearing set. According to this approach, the amplitude of dynamic wheel load can be obtained from a lumped parameter analysis of a suspension system, which can then be used for detailed static finite element analysis of a wheel bearing system. The finite element modelling approach has been validated by successfully predicting the load bearing capacity of an SKF ball bearing set for an acceptable fatigue life. For the first time, using a powerful commercial explicit finite element analysis tool, a detailed dynamic analysis has been carried of a deep groove ball bearing with a rotating inner race. The analysis has led to a consistent representation of complex motions consisting of rotations and revolutions of rolling elements, and generated insights into the stresses developed in the various components such as balls and races. In conclusion, a simple yet effective fuzzy logic-based yaw control algorithm has been presented in the current research. According to this algorithm, two inputs i.e. a yaw rate error and a driver steering angle are used for generating an output in the form of an additive steering angle which potentially can aid a driver in avoiding straying from an intended path.