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Technical Paper
2014-04-01
Xinxin Shao
Abstract In this paper, a passive anti-pitch anti-roll hydraulically interconnected suspension is proposed for compromising the control between the pitch and roll mode of the sprung mass. It has the advantage in improving the directional stability and handling quality of vehicles during steering and braking manoeuvres. Frequency domain analysis of a 7-DOF full-car model with the proposed system is presented. The modeling of mechanical subsystem is established based on the Newton's second law. Then the mechanical-hydraulic system boundary conditions are developed by incorporating the hydraulic strut forces into the mechanical subsystem as externally applied forces. The hydraulic subsystem is modelled by using the impedance method, and each circuit are determined by the transfer matrix method. And then the modal analysis method is employed to perform the vibration analysis between the vehicle with the conventional suspension and the proposed HIS. Comparison analysis focuses on natural frequencies and modal shapes with identified eigenvalues and eigenvectors.
Technical Paper
2014-04-01
Dongmei Wu, Haitao Ding, Konghui Guo, Zhiqiang Wang
Abstract Pressure following control is the basic function of Electro-Hydraulic Braking system (EHB), which is also the key technology of stability control system and regenerative braking system for hybrid and electric vehicles. Experimental research is an important method for the control and application of EHB. This paper describes a method to test and control the EHB system through experiment on the Hardware-in-the-loop (HIL) test bench and wheel motor electric vehicle. First, the HIL test bench was established, in which the EHB was tested, including the characteristics of solenoid valves and motor. Then the wheel cylinder pressure was controlled to follow the specific signal input and the master cylinder pressure. Based on this, EHB and the pressure following control method were applied to the wheel motor electric vehicle. The results show that the braking pressure can follow the driver's braking intention to realize the conventional braking function of electric vehicles. This is the basis of stability control system and regenerative braking system for hybrid and electric vehicles.
Technical Paper
2014-04-01
Andrew Hall, John McPhee
Abstract Physical rig testing of a vehicle is often undertaken to obtain experimental data that can be used to ensure a mathematical model is an accurate representation of the vehicle under study. Kinematics and Compliance (K&C) testing is often used for this purpose. The relationship between the hard point locations and compliance parameters, and K&C characteristics of a suspension system is complex, and so automating the process to correlate the model to the test data can make the exercise easier, faster and more accurate than hand tuning the model. In this work, such a process is developed. First, the model parameters are adjusted, next a simulation is run, before the results are read and post processed. This automation processed is used in conjunction with an optimization procedure to carry out the K&C correlation. MATLAB scripts are created to modify the model parameters, run simulations and read the results so that MATLAB optimization algorithms can be used to identify the most appropriate suspension parameter values.
Technical Paper
2014-04-01
Daryl R. Poirier, Ravindra Patil, Robert Geisler, Joseph Schudt
Abstract The automotive industry is under great pressure to reduce vehicle mass for both cost and fuel economy gains. A significant contributor to body and suspension structure mass is peak vertical loads, primarily entering the body structure through the jounce bumper to body interface. This paper focuses on the successful development of “Loads Management Striker Caps” for the 2013 Cadillac ATS front and rear suspension. Component design and development of the striker caps was executed using explicit finite element analysis tools. Multi-body dynamics vehicle models were used to set component requirements and confirm striker cap performance for the vehicle during peak vertical events. The “Loads Management Striker Caps” ultimately reduced peak strut/shock tower loads by 40% in the front suspension and 25% in the rear suspension. This resulted in significant body and chassis mass savings, contributing to the Cadillac ATS's class leading curb weight.
Technical Paper
2014-04-01
Changxin Wang, Wenku Shi, Qinghua Zu
Abstract Aiming at the difficulty of sovling the stiffness calculation of taper-leaf spring with variable stiffness, a combined method was proposed, which combine superposition method and finite difference method. Then the calculation results of different differential segments were compared with experimental results. The compared results show that the proposed method is effective and simple. So it has some practical significance in designing the taper-leaf spring. In addition, based on the stiffness test of the taper-leaf spring, the proper adjustments to the correction factor of the single parabolic leaf spring stiffness formula was recommended(ξ =0.92-0.96).
Technical Paper
2014-04-01
Diana Hernandez-Alcantara, Luis Amezquita-Brooks, Ruben Morales-Menendez
Abstract Semi-active suspension systems aim to improve the vehicle safety and comfort. For these systems control laws are required to achieve the desired performance improvements. On the other hand, the instrumentation of the vehicle suspension typically consists only in accelerometers, which are used to measure the vertical accelerations. However, velocities and/or displacements are required to implement the most common control algorithms for semi-active suspension systems. For instance, Skyhook and Groundhook controllers require the knowledge of the suspension vertical velocities. In this article several vertical velocities estimation approaches are studied and compared. In practical applications, it is common to use simple integrators to estimate these variables; nonetheless, it is well known that integrator-based estimations present errors due to drift. In applications where high performance is required, a better estimation of the state variables of the suspension system is essential.
Technical Paper
2014-04-01
Walid Oraby, Mahmoud Atef Aly, Samir El-demerdash, M. El-Nashar
Abstract Integral Control strategy for vehicle chassis systems had been of great interest for vehicle designers in the last decade. This paper represents the interaction of longitudinal control and lateral control. In other words the traction control system and handling control system. Definitely, tire properties are playing a vital role in such interaction as it is responsible for the generated forces in both directions. A seven degrees of freedom half vehicle model is derived and used to investigate this interaction. The vehicle body is represented as a rigid body with three degrees of freedom, lateral and longitudinal, and yaw motions. The other four degrees are the two rotation motion of the front wheel and the rear wheel. This two motions for each wheel are spin motion and the steering motion. The traction controller is designed to modulate engine torque through adjusting the throttle angle of the engine upon utilized adhesion condition at the driving road wheels. The active four steering (4WS) control system is designed to enhance vehicle lateral dynamics through controlling rear steer angle.
Technical Paper
2014-04-01
Yuhang Chen, Yunfeng Ji, Konghui Guo
Abstract In this paper, a sliding mode observer for estimating vehicle slip angle and tire forces is developed. Firstly, the sliding mode observer design approach is presented. A system damping is included in the sliding mode observer to speed the observer convergence and to decrease the observer chattering. Secondly, the sliding mode observer for vehicle states is developed based on a 7 DOF embedded vehicle model with a nonlinear tire model ‘UniTire’. In addition, since the tire lateral stiffness is sensitive to the vertical load, the load transfers are considered in the embedded model with a set of algebraic equations. Finally, a simulation evaluation of the proposed sliding mode observer is conducted on a validated 14 DOF vehicle model. The simulation results show the model outputs closely match the estimations by the proposed sliding mode observer.
Technical Paper
2014-04-01
Haizhen Liu, Weiwen Deng, Changfu Zong, Jian Wu
Abstract This paper first presents an algorithm to detect tire blowout based on wheel speed sensor signals, which either reduces the cost for a TPMS or provides a backup in case it fails, and a tire blowout model considering different tire pressure is also built based on the UniTire model. The vehicle dynamic model uses commercial software CarSim. After detecting tire blowout, the active braking control, based on a 2DOF reference model, determines an optimal correcting yaw moment and the braking forces that slow down and stop the vehicle, based on a linear quadratic regulator. Then the braking force commands are further translated into target pressure command for each wheel cylinder to ensure the target braking forces are generated. Some simulations are conducted to verify the active control strategy. From the simulation results, it is shown that this active brake control strategy can not only ensure the flat tire vehicle stability, but also slow down the vehicle with a safe speed and for a shorter distance.
Technical Paper
2014-04-01
Takamasa Shimodaira
Abstract The aim discussed in this paper is to show a technique to predict loads input to the wheels, essential to determining input conditions for evaluation of suspension durability, by means of full vehicle simulations using multi body analysis software Adams/Car. In this process, model environments were built to enable reproduction of driving modes, and a method of reproducing the set-up conditions of a durability test vehicle was developed. As the result of verification of the accuracy of the simulations in the target driving modes, good correlation for waveforms can be confirmed. And also confirm a good correlation in relation to changes of input load due to changes in suspension specifications.
Technical Paper
2014-04-01
Mustafa Ali Arat, Saied Taheri
Abstract A vehicle's response is predominately defined by the tire characteristics as they constitute the only contact between the vehicle and the road; and the surface friction condition is the primary attribute that determines these characteristics. The friction coefficient is not directly measurable through any sensor attachments in production-line vehicles. Therefore, current chassis control systems make use of various estimation methods to approximate a value. However a significant challenge is that these schemes require a certain level of perturbation (i.e. excitation by means of braking or traction) from the initial conditions to converge to the expected values; which might not be the case all the time during a regular drive. This study proposes an observer scheme that utilizes an instrumented tire (i.e. smart tire) as an additional sensor input and develops a sliding-mode observer based on tire force feedback to provide the estimated friction coefficient irrespective of the available excitation.
Technical Paper
2014-04-01
Wenku Shi, Changxin Wang
Abstract In order to reasonably match the variable stiffness suspension and optimize the ride comfort and stability of a light bus, a virtual prototype model of the light bus was established in Adams-Car. Before the optimization, the tyre mechanical characteristics were tested by using a plate-type tyre tester, then the magic formula model of the tyre (Pac2002) was obtained by means of the global parameter identification method. The vertical vibration of the virtual model was simulated with the simulated B-class road profile, and its handling stability performance was also studied by simulation of the pylon course slalom test and steady static circular test. After that, an optimal method of the variable stiffness suspension was put forward. In the proposed method, the two-level stiffness (k1, k2) and the damping of the rear suspension and the torsional stiffness of the pre and post stabilizer bars were taken as the optimal variables. The Z-direction acceleration RMS of the bus frame, the yaw rate and the roll angle of the bus body were selected as the optimal target.
Technical Paper
2014-04-01
Barys Shyrokau, Dzmitry Savitski, Danwei Wang
Abstract Nowadays there is a tendency to implement various active vehicle subsystems in a modern vehicle to improve its stability of motion, handling, comfort and other operation characteristics. Since each vehicle subsystem has own limits to generate supporting demand, their potential impact on vehicle dynamics should be analyzed for steady-state and transient vehicle behavior. Moreover, the additional research issue is the assessment of total energy consumption and energy losses, because a stand-alone operation of each vehicle subsystem will provide different impact on vehicle dynamics and they have own energy demands. The vehicle configuration includes (i) friction brake system, (ii) individual-wheel drive electric motors, (iii) wheel steer actuators, (iv) camber angle actuators, (v) dynamic tire pressure system and (vi) actuators generating additional normal forces through external spring, damping and stabilizer forces. A passenger car is investigated using commercial software. The actuator models are defined using experimental test results and technical literature information.
Technical Paper
2014-04-01
Edoardo Sabbioni, Federico Cheli, Matteo Riva, Andrea Zorzutti
Abstract For passenger cars, individual tyre model parameters, used in vehicle models able to simulate vehicle handling behavior, are traditionally derived from expensive component indoor laboratory tests as a result of an identification procedure minimizing the error with respect to force and slip measurements. Indoor experiments on agricultural tyres are instead more challenging and thus generally not performed due to tyre size and applied forces. However, the knowledge of their handling characteristics is becoming more and more important since in the next few years, all agricultural vehicles are expected to run on ordinary asphalt roads at a speed of 80km/h. The present paper presents a methodology to identify agricultural tyres' handling characteristics based only on the measurements carried out on board vehicle (vehicle sideslip angle, yaw rate, lateral acceleration, speed and steer angle) during standard handling maneuvers (step-steers, J-turns, etc.), instead than during indoor tests.
Technical Paper
2014-04-01
Jonathan M. S. Mattson, Michael Mangus, Christopher Depcik
Abstract A timing sweep to correlate the location of Maximum Brake Torque (MBT) was completed on a single-cylinder, direct injected compression ignition engine that was recently upgraded to a high-pressure rail injection system for better engine control. This sweep included emissions monitoring for carbon dioxide, carbon monoxide, particulate matter, hydrocarbons, and oxides of nitrogen for the calibration of a heat release model, as well as the opportunity to relate MBT timing to brake-specific emissions production. The result of this timing sweep was a relatively linear correlation between injection delay and peak pressure timing. In addition, a number of other MBT timing methodologies were tested indicating their applicability for immediate feedback upon engine testing, particularly mass fraction burned correlations. Emissions were either strongly correlated to MBT timing (with emissions being minimized in the vicinity of MBT), or were completely independent of MBT. In addition, the end of the MBT timing envelope was linked to increased fuel consumption, as well as a rise in aromatic hydrocarbon emissions.
Technical Paper
2014-04-01
Yuan Qu, Wang Hongbin, Dechao Zhang, Linbo Zhang, Shen Wu
Abstract The understeer of vehicle is desired for the vehicle's handling performance, and the roll rate of rear suspension is one of the key characteristics to achieve the understeer performance. A proper roll rate of the rear suspension is required to assure a certain level of understeer. Generally, in the vehicle dynamic tuning process, several methods are available for improving understeer performance, e.g., changing the hard-points of suspensions, adjusting stiffness of bushings, etc. On the other hand, structure optimization of components can be used in some case to improve the performance. In this paper, the optimization method is applied to the twist beam of rear suspension. The change in local geometry by optimized design leads to appropriate adjustment of the roll rate. Finally the vehicle understeer performance reaches design target.
Technical Paper
2014-04-01
Yong-Sub Yi, Joonhong Park, Kyung-Jin Hong
Abstract In the early stage of vehicle development process, it is customary to establish a set of goals for each kinematic and compliance (K&C) characteristic and try to find out design variables such as the location of hard points and bushing stiffness which can achieve these goals. However, since it is very difficult to find out adequate set of design variables which satisfy all the goals, many engineers should rely on their own experiences and intuitions, or repeat trial and error to design a new suspension and improve old one. In this research, we develop a suspension design process by which suspension K&C characteristic targets can be achieved systemically and automatically. For this purpose, design optimization schemes such as design of experiments (DoE) and gradient-based local optimization algorithm are adopted. Firstly, sensitivity analysis is carried out using DoE and then, according to the analysis results, the whole problem is divided into two partial problems which are independent of each other.
Technical Paper
2014-04-01
Tae-Sang Park, Sungho Jin, Jeon IL Moon, Seung-Han Yang
Abstract As is well known, the brake systems of vehicles are used in order to decelerate or stop the vehicle while the driving. The operational principle of the brake is the conversion of kinetic energy into thermal energy. In this case, the thermal energy is released to the atmosphere. Recently, electromechanical brakes (EMB) were developed in order to replace hydraulic brake calipers. Such brake-by- wire systems are composed of an electronic pedal, electronic control unit (ECU), wire, and an electromechanical caliper. A typical electromechanical brake is similar to existing floating brakes. In other words, an inner pad pushes out one side of a disc driven by the energy of a motor; by means of a screw-thread gear. Then, the caliper slides in the opposite direction by reaction force and moves the outer pad toward the other side of the disc. Then pads clamp both sides of the rotating disc and stop the wheel. While effective, this design has the problem that there is a difference in the wear of the inner and outer pads.
Technical Paper
2014-04-01
Jakub Zebala, Wojciech Wach
Abstract The objective of the paper is to present the results of an investigation of the effect of reduced tire pressure on car lateral dynamics in lane change maneuver. The intended aim was attained by performing bench and road tests. The aim of the bench tests was parameterization of the mathematical model of the tested car. The road tests covered the vehicle motion with reduced and no tire pressure on a curvilinear track adequate for bypassing an unexpected appearing obstacle. Next, simulations in PC-Crash were performed, and the results were compared with those obtained in experiments.
Technical Paper
2014-04-01
Gary A. Davis
Abstract The critical speed method uses measurements of the radii of yawmarks left by vehicles, together with values for centripetal acceleration, to estimate the speeds of the vehicles when the yawmarks were made. Several field studies have indicated that equating the centripetal force with braking friction produced biased estimates, but that the biases tended to be small (e.g. within 10%-15% on average) and led to underestimates, suggesting that the method can be useful for forensic purposes. Other studies, however, have challenged this conclusion. The critical speed method has also seen use in safety-related research, where it is important to have a reliable assessment of the uncertainty associated with a speed estimate. This paper describes a variant of the critical speed method, where data from field tests lead to an informative prior probability distribution for the centripetal acceleration. Using Bayes theorem, this distribution is combined with the measured radius to produce a posterior probability distribution for the desired speed.
Technical Paper
2014-04-01
Renaud Deborne, Skárlet Khouri Silva, Andras Kemeny
Abstract By the action on the steering wheel, the driver has the capability to control the trajectory of its vehicle. Nevertheless, the steering wheel has also the role of information provider to the driver. In particular, the torque level at the steering wheel informs the driver about the interaction between the vehicle and the road. This information flow is natural due to the mechanical chain between the road and the steering wheel. Many studies have shown that steering wheel torque feedback is crucial to ensure the control of the vehicle. In the context of uncoupled steering (steer-by-wire vehicle or driving simulators), the torque rendering on the steering wheel is a major challenge. In addition, of the trajectory control, the quality of this torque is a key for the immersion of drivers in virtual environment such as in driving simulators. The torque-rendering loop is composed of different steps. At first, a vehicle dynamics model computes the torque level at the steering wheel regarding the vehicle state (steering wheel position, vehicle speed, etc.).
Technical Paper
2014-04-01
Flaura Winston, Catherine McDonald, Venk Kandadai, Zachary Winston, Thomas Seacrist
Abstract Driving simulators offer a safe alternative to on-road driving for the evaluation of performance. In addition, simulated drives allow for controlled manipulations of traffic situations producing a more consistent and objective assessment experience and outcome measure of crash risk. Yet, few simulator protocols have been validated for their ability to assess driving performance under conditions that result in actual collisions. This paper presents results from a new Simulated Driving Assessment (SDA), a 35- to-40-minute simulated assessment delivered on a Real-Time® simulator. The SDA was developed to represent typical scenarios in which teens crash, based on analyses from the National Motor Vehicle Crash Causation Survey (NMVCCS). A new metric, failure to brake, was calculated for the 7 potential rear-end scenarios included in the SDA and examined according two constructs: experience and skill. The study included an inexperienced group (n=21): 16-17 year olds with 90 days or fewer of provisional licensure, and an experienced group (n=17): 25-50 year olds with at least 5 years of PA licensure, at least 100 miles driven per week and no self-reported collisions in the previous 3 years.
Technical Paper
2014-04-01
Chi Jin, Lu Xiong, Zhuoping Yu, Yuan Feng
Abstract In this paper we present a path following control design for a six-wheel skid-steering vehicle. Contrary to the common approaches that impose non-holonomic constraints, a dynamic vehicle model is established based on a pseudo-static tire model, which uses tire slip to determine tire forces. Our control system admits a modular structure, where a motion controller computes the reference vehicle yaw rate and reference vehicle speed and a dynamics controller tracks these signals. A robust nonlinear control law is designed to track the reference wheel speeds determined by the dynamics controller with proved stability properties. Saturated control techniques are employed in designing the reference yaw rate, which ensures the magnitude of the reference yaw rate does not violate the constraint from the ground-tire adhesion. The simulation results demonstrate the effectiveness of the proposed path following control design.
Technical Paper
2014-04-01
Zhiting Zhu, Lu Xiong, Chi Jin
Abstract The control in transient conditions when hydraulic brake and regenerative brake switch mutually is the key technical issue about electric vehicle hybrid brake system, which has a direct influence on the braking feel of driver and vehicle braking comfort. A coordination control system has been proposed, including brake force distribution correction module and motor force compensation module. Brake force distribution correction module has fixed the distribution results in hydraulic brake force intervention condition, hydraulic brake force evacuation condition and regenerative brake force low speed evacuation condition. Motor compensation module has compensated hydraulic system with motor system, which has fast and accurate response, thus the response of whole hybrid system has been improved. Simulation results in transient conditions show that the coordination control strategy can effectively reduce the fluctuations and deviations of total brake force, and improve braking feel of driver and vehicle braking comfort.
Technical Paper
2014-04-01
Hu Zhang, JianWei Zhang, Konghui Guo
Abstract Whether high-precision torque control or motor condition monitoring need accurate motor parameters. For the three parameters of surface-mounted permanent magnet synchronous motor (SPMSM), the voltage equation is rank-deficient. To solve this problem, some scholars proposed methods that build full rank equations with signal injection, but this will produce motor torque ripple, which is not suitable for application to the EPS. Therefore, this paper proposes a method based on MRAS to identify motor parameters step by step. The proposed two steps identification method can make the reference model full rank in every step, but the total decoupling between parameters identification processes cannot be realized for the assumption that the prior step result is the real value. It was found in experiment that this effect varies with the motor operating conditions. Therefore, this paper analyzes the sensitivity of the motor parameters and proposes a method to improve the accuracy of identification results by changing the weight of identification results according to the operating conditions.
Technical Paper
2014-04-01
Suhas Kangde, Vishal Shitole, Ashish Kumar Sahu
Abstract Automotive Suspension is one of the critical system in load transfer from road to Chassis or BIW. Using flex bodies in Multi body simulations helps to extract dynamic strain variation. This paper highlights how the MBD and FE integration helped for accurate strain prediction on suspension components. Overall method was validated through testing. Good strain correlation was observed in dynamic strains of constant amplitude in different loading conditions. Combination of different direction loading was also tested and correlated. Method developed can be used in the initial phase of the vehicle development program for suspension strength evaluation. Suspension is one of the important system in vehicle which is subjected to very high loading in all the directions. To predict the dynamic stresses coming on the suspension system due to transient loads, faster and accurate method is required. To accelerate the suspension design process it become necessary to get good accuracy in the results.
WIP Standard
2014-04-01
This SAE Standard applies to the usage of tires of the same nominal size and tread type, but with different outside diameter for articulated front-end loaders. Articulated four-wheel-drive front-end loader performance and component life can be affected by excessive differences in the tire outside circumference and/or diameter. The purpose is to provide specific guidelines for the usage of tires with different outside circumference and/or diameter on articulated front-end loaders.
Collection
2014-04-01
This technical paper collection focuses on new theory, formulation and modeling of amplitude-, frequency- and temperature-dependent nonlinear components/systems such as rubber and hydraulic mounts or bushings, shock absorbers, and any joint friction/damping; dynamic characterization through lab and field testing; Linearization methodology; Model validation, application, and sensitivity analysis in vehicle system/subsystem simulations; Nonlinear system identification, modeling, and application in testing accuracy improvement, etc.
Collection
2014-04-01
This technical paper collection is focused on vehicle dynamics and controls using modeling and simulation, and experimental analysis of passenger cars, heavy trucks, and wheeled military vehicles. The papers address active and passive safety systems to mitigate rollover, yaw instability and braking issues; driving simulators and hardware-in-the-loop systems; suspension kinematics and compliance, steering dynamics, advanced active suspension technologies; and tire force and moment mechanics.
Collection
2014-04-01
This technical paper collection presents papers on steering and suspension related topics as it applies to ground vehicles. Papers for this session address new approaches as well as advances in application of steering, suspension related technologies.
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