Advanced suspension system using magnetorheological technology for vehicle vibration control

In the past forty years, the concept of controllable vehicle suspension has attracted extensive attention. Since high price of an active suspension system and deficiencies on a passive suspension, researchers pay a lot attention to semi-active suspension. Magneto-rheological fluid (MRF) is always an ideal material of semi-active structure. Thanks to its outstanding features like large yield stress, fast response time, low energy consumption and significant rheological effect. MR damper gradually becomes a preferred component of semi-active suspension for improving the riding performance of vehicle. However, because of the inherent nonlinear nature of MR damper, one of the challenging aspects of utilizing MR dampers to achieve high levels of performance is the development of an appropriate control strategy that can take advantage of the unique characteristics of MR dampers. This is why this project has studied semi-active MR control technology of vehicle suspensions to improve their performance. Focusing on MR semi-active suspension, the aim of this thesis sought to develop system structure and semi-active control strategy to give a vehicle opportunity to have a better performance on riding comfort. The issues of vibration control of the vehicle suspension were systematically analysed in this project. As a part of this research, a quarter-car test rig was built; the models of suspension and MR damper were established; the optimization work of mechanical structure and controller parameters was conducted to further improve the system performance; an optimized MR damper (OMRD) for a vehicle suspension was designed, fabricated, and tested. To utilize OMRD to achieve higher level of performance, an appropriate semi-active control algorithm, state observer-based Takagi-Sugeno fuzzy controller (SOTSFC), was designed for the semi-active suspension system, and its feasibility was verified through an experiment. Several tests were conducted on the quarter-car suspension to investigate the real effect of this semiactive control by changing suspension damping. In order to further enhance the vibration reduction performance of the vehicle, a fullsize variable stiffness and variable damping (VSVD) suspension was further designed, fabricated, and tested in this project. The suspension can be easily installed into a vehicle suspension system without any change to the original configuration. A new 3- degree of freedom (DOF) phenomenological model to further accurately describe the dynamic characteristic of the VSVD suspension was also presented. Based on a simple on-off controller, the performance of the variable stiffness and damping suspension was verified numerically. In addition, an innovative TS fuzzy modelling based VSVD controller was designed. The TS fuzzy modelling controller includes a skyhook damping control module and a state observer based stiffness control module which considering road dominant frequency in real-time. The performance evaluation of the VSVD control algorithm was based on the quarter-car test rig which equipping the VSVD suspension. The experiment results showed that this strategy increases riding comfort effectively, especially under off-road working condition. The semi-active control system developed in this thesis can be adapted and used on a vehicle suspension in order to better control vibration

The 1975 Ride Quality Symposium

A compilation is presented of papers reported at the 1975 Ride Quality Symposium held in Williamsburg, Virginia, August 11-12, 1975. The symposium, jointly sponsored by NASA and the United States Department of Transportation, was held to provide a forum for determining the current state of the art relative to the technology base of ride quality information applicable to current and proposed transportation systems. Emphasis focused on passenger reactions to ride environment and on implications of these reactions to the design and operation of air, land, and water transportation systems acceptable to the traveling public. Papers are grouped in the following five categories: needs and uses for ride quality technology, vehicle environments and dynamics, investigative approaches and testing procedures, experimental ride quality studies, and ride quality modeling and criteria

Driver Steering Control and Full Vehicle Dynamics Study Based on a Nonlinear Three-Directional Coupled Heavy-Duty Vehicle Model

Under complicated driving situations, such as cornering brake, lane change, or barrier avoidance, the vertical, lateral, and longitudinal dynamics of a vehicle are coupled and interacted obviously. This work aims to propose the suitable vehicle and driver models for researching full vehicle dynamics in complicated conditions. A nonlinear three-directional coupled lumped parameters (TCLP) model of a heavy-duty vehicle considering the nonlinearity of suspension damping and tire stiffness is built firstly. Then a modified preview driver model with nonlinear time delay is proposed and connected to the TCLP model to form a driver-vehicle closed-loop system. The presented driver-vehicle closed-loop system is evaluated during a double-lane change and compared with test data, traditional handling stability vehicle model, linear full vehicle model, and other driver models. The results show that the new driver model has better lane keeping performances than the other two driver models. In addition, the effects of driver model parameters on lane keeping performances, handling stability, ride comfort, and roll stability are discussed. The models and results of this paper are useful to enhance understanding the effects of driver behaviour on full vehicle dynamics

Vibration Effect Produced by Raised Pavement Markers on the Exit Ramp of an Expressway

Driving over raised pavement markers (RPMs) spaced at different spacing, the human body will experience different vibrations. To explore whether RPMs situated at the exit ramp of an expressway induce a good vibration warning effect, this paper determines the spacing of RPMs situated along a deceleration lane and curved ramp. Models of roads, vehicles, and RPMs are first established in the ADAMS software, after which an integrated human-chair model constructed in SolidWorks is imported into ADAMS, and then the complete model is formed so that vibration simulations of different types of vehicle at different spacing and speeds can be carried out. The results show that the vibration warning effects of the spacing proposed by the existing Chinese specifications and this paper are basically between level III and level IV, the driver’s subjective feeling is between less comfortable and uncomfortable, and both induce a good vibration warning effect. For a linear deceleration lane, when considering traffic safety, a spacing of 3 m is recommended; when considering the economy, a spacing of 6 m is recommended. For a curved deceleration lane and curved ramp, according to the actual curve radius, the spacing of RPMs can refer to the spacing recommended in the paper. In addition, the vibration warning effect for cars and semi-trailer trucks initially increases with an increase in the speed; then, after reaching a certain peak speed, the effect decreases with an increase in the speed, and finally, it tends to become gentle at speeds exceeding 100 km/h. The vibration warning effect for a semi-trailer truck is better than that for a car under the same spacing and speed. Document type: Articl

Investigation of the Dynamic Interaction between the Human Body and Car Seat Using a Unique Simulation Technique

Numerical simulations and mathematical models have been developed over last many years on the certain portions of human body, car seat or automobile to characterise, monitor and assess the level of vibration and its effects on the human occupant inside the automotive. Though, the numerical simulations can define the level and nature of vibration and its transmissibility up to a certain stage, vibration measurement techniques have also been gaining importance for last several years to fill the limitations of the theoretical models. Efforts have also been made to carry out vibration related investigations using combined numerical simulation and measurement procedure for the car seat and the seated human body inside car, though the numbers of case studies carried out with the combination of simulation and measurement procedure are very less. Some technologies have been achieved to judge the level of vibration inside the car seat and its human occupant, though those technologies cover only effects of vibration, dynamics or measurement techniques on specific portions of the car or the human body without considering all the real life factors, e.g., human gender, shape of the human portions, size specific stiffness properties, in-vehicle operating conditions and damping factors. Approaches to provide a comprehensive solution to estimate the level of vibration without real life testing have not been carried out by the existing technologies very well. More than that the existing technologies investigate only particular modules of the entire human-car dynamic systems, e.g., a specific human part, seat and human interaction, vibration transmission from seat to human body or the vibration measurement technique. So, there is enormous scope of further improvement and the aim of this research work is to provide a unique simulated system considering all the critical real life factors. Outcome of this simulation study will evaluate the vibration levels inside the segments of seated human body inside a car and car seat omitting the necessity of real-life practical testing and provide the solution by linking module-wise investigations of human body and car seat. Initiative has been taken to fill up the gaps in the existing technologies and offer a novel study on the comprehensive simulation model of the combined human body and car seat bio-dynamic system to optimize the health, safety and comfort levels of the car seated human body. Present research work covered the tasks of establishing the simulations for non-linear bio-dynamic model of the seated human body, feasibility and behaviour inspection of polyurethane foam cushions, contact mechanism assignment between the human body and the car seat and establishing the simulation of car seated human occupant under the real life environment. Vertical displacements, vertical accelerations and frequencies at designated points of human body and car seat have been extracted from the simulation outcome and the obtained results have been validated though real-life vibration testing data. This unique simulation methodology can successfully be implemented to predict the final vibration levels inside the car seat and the car seated human body to optimize the health, safety and comfort of the human-car seat system. The outlined novel technique contributed knowledge to the entire human body and car seat dynamic system rather than focusing only on a very specific portion of the system. An industrial guideline has been presented to implement this unique simulation methodology in similar sectors, which will lead various industries to avoid time consuming and expensive bio-dynamic vibration testing methods and help to understand the impact of vibration on the in-vehicle human body in a better way

Development of a model to predict discomfort in a vehicle due to vibration

Human exposure to vehicular vibration can cause sensations (e.g. physical discomfort or annoyance), health issues and safety problems. In industry, several measurement methods have been proposed to improve ride quality and increase the drivers’ or passengers’ expectations in terms of comfort. The measurement and evaluation methods of quantifying whole-body vibration exposure in relation to human comfort and vibration perception are defined by the International Standard ISO 2631-1. This is the most used standard which provides Health guidance caution zones for risk assessment. The human discomfort threshold limits are not given in this standard. Human discomfort, in general, is defined by measurements based on a shaker table and seat combination. These results when used for “in vehicle situations” may not accurately indicate the level of human discomfort in a vehicle. In this thesis, a seated human’s discomfort is quantified in heave, pitch and roll motions using a four-post rig simulator in order to determine a comfort metric. The quantifying and assessment of discomfort are studied in two categories, which are vehicle dynamics with road inputs, and the human response with human perception to vibration. Comfort/discomfort is a subjective variable; therefore the in-situ experiments were performed based on an objective measurement method with a subjective judgement method. The main novel contribution of this thesis is that subjective and dynamic responses of twenty four seated subjects, in a car on the four post rig excitation, exposed to vertical sinusoidal vibration at five magnitudes in heave, pitch and roll motions were taken at Oxford Brookes University. The physical properties of participants such as age, height, and weight were recorded because human sensitivity, perception and threshold levels may be person dependent. The subjective assessment data was developed based on the response of twenty-four seated subjects to vibration in a car on the four post rig which makes this thesis unique in terms of quantifying of human feeling. From the experimental data (RMS acceleration and subjective assessment), a discomfort metric was developed in terms of the cause-effect relations between the road and the human body. Based on the analysis and results, it was observed that the sensitivity to acceleration decreased with decreasing amplitude and increasing frequency. This discomfort metric was applied to a developed analytical model to predict the vibration response. A predictive integrated vehicle-seat-human model was developed to characterize the biodynamic response behaviour of a seated human subject and analyse the influence of vibration transmitted on the human body segments. The transmissibility results from an integrated model and in-situ discomfort curve measurements were combined to develop a human body discomfort model in a car. The discomfort index curves were predicted by combining the modelling study and the experimental results for heave, pitch and roll modes

Lane Change Strategy for Autonomous Vehicle

Recently, people’s demand for smart vehicles continues to improve. As the core of smart driving, driverless vehicle becomes the most concerned technology. Lane change, the most common behavior in driverless situation, greatly affect the road efficiency. Fast and safe lane change operations have very practical significance in reducing traffic accidents. This paper uses driverless vehicle as research object, and the pathing planning and pathing tracking for lane change situation are studied. An efficient path planning method and trajectory tracking controller are designed and simulated. The main content contains the three following aspects: (1) A set of comprehensive lane change strategy is designed for different working conditions. Then path planning for lane change is researched based on mass point model and an efficient path planning method based on polynomial is proposed and optimized. (2) Kinematic model and 3 DOFs dynamic model of driverless vehicle based on magic tire model are established using SIMULINK. Several simulation and test are done to verify the rationality of the model. (3) The trajectory -tracking control system based on PID controller is designed. Then run simulation based on the model established and according to the results, the trajectory -tracking control system can track the lane-changing path accurately and analysis is made. Key word: Driverless vehicle, Lane change, Path planning, Trajectory tracking contro

Truck seating comfort: objectify and subjectify measurement approach

Technology has changed trucks significantly over the years. Truck companies are getting interested in comfortable equipment for their employees in order to create a healthy and stimulating working environment. Due to this reason, truck manufacturers recognize comfort as one of the major selling point, as it is thought to play an important role for the buyer as well. Seat is one of the most important components of truck and they are the place where professional driver spend most of their time. The aim of the paper is to describe the measurement methods that used to improve the physiological comfort of truck driver’s seat. There will be three sections in the paper. First, the paper describes the nature of sitting comfort and discomfort. Secondly, it describes the subjective and objective measurement methods that are used to evaluate the truck seat. Thirdly, the paper proposes a methodology for the development of comfortable truck driver’s seats