International Journal of Vehicle Performance (9 papers in press)
Numerical modelling of explosively formed projectiles compared with experiments and results of a numerical sensitivity study
by Morten Rikard Jensen, Phillip Mulligan
Abstract: The research covered in this paper is related to the numerical modelling of explosively formed projectiles (EFP). In-depth literature reviews on both the physical characteristics and simulation of this weapon are given. Results from a numerical model of an EFP are compared with experimental data showing good correlation. All models ran successfully to normal termination. They showed how numerical tools can be used to describe and investigate these very complicated events involving large deformation and extremely high strain rates. Further, a sensitivity study is carried out on the location of the detonation point, the number of smoothed particle hydrodynamics (SPH) particles, type of high explosive (HE) as well as a test case where the casing is not modelled.
Keywords: EFP; explosively formed projectiles; SPH; sensitivity study; explicit finite element; numerical modelling; high explosive.
Special Issue on: Recent Advancements in Commercial Vehicle Roll Dynamics Studies
Active Trailer Braking Control for Car-Trailer Combination Based on Multi-objective Fuzzy Algorithm
by Pengwei Su, Xing Xu, Feng Wang, Bin Wang, Jie Mi
Abstract: In order to improve the braking stability and path following performance of trailer under steering and braking conditions, a differential braking control method is proposed. Considering the electromechanical coupling characteristic of electromagnetic brake, a 6-DOF car-trailer (CT) combination dynamics model is established. A hierarchical control frame is proposed, the upper controller determines the additional yaw moment based on multi-objective fuzzy (MOF) control algorithm with yaw rate and hinge angle as control objects. The lower braking force distribution controller is designed with the rules to determine left and right braking torque, the electromagnetic brake gets the corresponding current to realize differential brake. A joint simulating model with TruckSim and Simulink is built, the simulation results show that the control strategy proposed in this paper effectively improves the braking stability of trailer. Compared with no differential braking control, the yaw rate and lateral acceleration are reduced, the hinge angle is closer to the ideal target under MOF control. Finally, real CT test is put forward to verify the accuracy of the model and the effectiveness of the control strategy.
Keywords: car-trailer; differential braking; yaw rate; hinge angle; multi-objective fuzzy algorithm; braking force distribution controller.
Effect of Off-centered Loading on Roll Stability of Multi-trailer Trucks
by Yang Chen, Xiaohan Zheng, Zichen Zhang, Mehdi Ahmadian
Abstract: The effect of partial loading on the wheel tip-up and rollover stability of 28-ft A-double tractor-trailers that are logistically attractive to the U.S. package carriers is studied using TruckSim
Keywords: off-centered loading; 28-ft A-double; commercial vehicle; roll stability; rollover; tip-up; J-turn; load transfer ratio; critical rollover speed; static stability factor.
GA Tuned H Infinity Roll Acceleration Controller Based on Series Active Variable Geometry Suspension on Rough Roads
by Shayan Nazemi, Masoud Masih-Tehrani, Morteza Mollajafari
Abstract: In this paper, a type of vehicle variable-geometry suspension, named, Series Active Variable Geometry Suspension is used on a GT car under turning event with crosswind forces on random Rough Road classes D and C in order to keep control of the vehicle\'s Roll Angle and Roll Angle Acceleration to prevent the car from transferring too much force into the passengers and the car\'s suspension links, also, to keep the tires Road Holding and not to let them leave the ground and prevent rollover accidents. To do so, first, the vehicle goes under modelling. The vehicle\'s full car dynamics are modeled. A Genetic Algorithm H? control synthesis would be applied to the system which goal objective is to control the vehicle\'s roll angle acceleration motion. Then, the maneuver fit for the goals is designed, which is turning with the forward speed of 100 km/h and an additional crosswind with the speed of 150 km/h that produces a maximum lateral acceleration of 0.4 m/s which is transferred to the vehicle\'s model. After that, the simulation is thoroughly discussed, it will be shown that the roads are generated using ISO8608, and random road classes D and C are produced. For comparison purposes, a Genetic Algorithm PID controller is designed so that the performance of the H? control synthesis would be better judged. The H? control synthesis succeeded in improving the vehicle\'s roll angle and rollover index up to 85% and the vehicle\'s roll angle acceleration up to 13% in comparison with the PID controller.
Keywords: H? Controller; Series Active Variable Geometry Suspension; SAVGS; Genetic Algorithm; Full-Car Modelling; Rollover Control; Random Rough Road.
Roll stability enhancement in a full dynamic ground-tour vehicle model based on series active variable-geometry suspension
by Amin Najafi, Masoud Masih-Tehrani
Abstract: Today, given the importance of vehicle rollover event and the high number of accidents in this area, in this paper, an attempt is made in the field of rollover prevention of the ground tour (GT) road vehicle equipped with a series of active variable-geometry suspension (SAVGS) system using a PID, Fuzzy PID and LQR controller. Previous works have used mostly skyhook and PID controllers. In this paper, the choice of these three controllers to achieve two advantages are to be robust and optimal. The complex has been evaluated in several different ways, taking into account the specific road conditions. In the present study, unlike previous works, an attempt has been made to use a full-dynamic vehicle model. This choice will make the study more comprehensive and accurate than the dynamic behavior of the vehicle. This will be due to the simulation results approaching the actual test values. Basics of controller design are reducing vertical body acceleration and, more importantly, for lowering the vehicle roll angle and overall angular accelerations to increase vehicle roll stability. The main differences and innovations made in the control strategy, in addition to choosing type of the controllers, are emphasis on the resistance of the controllers and use of a combination of the control methods to achieve the desired result. To achieve these aims, modeling of the full vehicle's dynamic parameters along with considering the actual test conditions is highly required, which in the present work, most of the above are covered. In summary, this work, while improving the control purposes such as roll prevention over to the expected parameters of vehicle suspension, such as separating vibrations and ride comfort, reduces overall energy consumption by selecting type of the suspension used.
Keywords: series active variable-geometry suspension; roll stability; Fuzzy-PID controller; linear quadratic regulator controller.
A Light-Duty Truck Model for the Analysis of On-center Handling Characteristics
by Yupeng Duan, Yunqing Zhang, Yan Wang, Jiongli Zeng, Peijun Xu
Abstract: For commercial vehicles, on-center handling characteristics deeply influences the driving safety and drivers feeling about the vehicle, since it represents steering feel and vehicle response on the highway. This research focuses on the on-center handling performance of light-duty trucks. A vehicle model was built to conduct the simulation of the on-center handling test. The model consists of a power steering system, non-independent front/rear suspensions, the powertrain system, and a mounted cab. Nonlinear properties of the power steering system, the friction hysteretic characteristic in the steering system, suspension system with leaf springs and tires are considered so as to reflect the complicated on-center handling characteristics. We conducted constant radius cornering tests, return-release tests, and high speed weave tests on a target vehicle. By comparing the test and simulation results, adjustments were made to the model parameters to improve simulation accuracy. A number of variables were altered to show its influence on the steering feel and vehicle response. The results show that the tires lateral force characteristics strongly affect the vehicle response. Steering gear ratio, steering system clearance, and caster angle strongly affect the steering feel.
Keywords: Light-duty trucks; On-center handling; Dynamic model; Parameter sensitivity analysis.
Roll Dynamics of Long Combination Semi-Trailers with Steerable Axles
by Borna Moghaddam, Wei Huang, Luke Steiginga, Gordon Poole, Robin Chhabra
Abstract: An assessment of the dynamic performance of Long Combination Vehicles (LCV) with steerable axle systems on their trailers was undertaken by National Research Council Canada in order to facilitate the regulation of LCVs for wider use on Canadian roads. A base dry box van A-train LCV combination and four steered combinations are modeled using TruckSim, each outfitted with a different steerable axle mechanism on the trailer. TruckSims driver logic is augmented through an optimized controller in Simulink to more accurately capture the drivers decision-making in response to the LCV dynamics and the steering mechanisms. Anti-lock Braking System (ABS) and traction control mechanisms are added to compensate for the reduced stability caused by improving the maneuverability. The modeled LCVs are run through high-speed lane change and high-speed turn simulations, the primary maneuvers that enable assessment of the roll dynamics of the truck combinations. The five configurations are compared in terms of standard performance parameters: static roll threshold, Rearward Amplification (RWA), Load Transfer Ration (LTR) , high-speed off-tracking and transient off-tracking. This study demonstrates that all of the proposed mechanisms are able to satisfy standard stability requirements.
Keywords: long combination vehicles; trailer steerable axles; roll stability; standard performance measures.
Mathematical model for farm tractors towing single axle trailer rollover prediction
by Giorgio Previati, Gianpiero Mastinu, Massimiliano Gobbi
Abstract: The paper deals with the estimation of the rollover limit of farms tractorrntowing a single axle trailer. Rollover is studied by considering the static stability on sloped surfaces. The relatively simple model is derived to understand the rollover mechanism basic features. Rollover phenomenon is quite complex and different instabilities can arise. In particular, depending on the actual available friction, the system can slide along the slope before reaching the rollover condition. The presence of trailer brakes plays a non negligible role. Different steering angles of the trailer with respect to the tractor are investigated. The derived model can predict the (static) rollover or sliding limit of farm tractor-single axle trailer systems for any orientation with respect to the slope and any tractor/trailer relative angle.
Keywords: rollover; tractor and trailer system; longitudinal and lateralrnslope; analytical models.
Analytical and Experimental Investigation of Roll Stability of a Truck Towing a Special Purpose Trailer with no Suspension
by Luke Steiginga, Wei Huang, Gordon Poole
Abstract: The purpose of this study was to compare the roll stability of three truck and trailer combinations. The special-purpose trailer was of particular interest because it had no suspension system. Multibody dynamics models of the vehicles were built to simulate vehicle performance on high-speed turns and lane changes. Physical testing was undertaken at a test track in order to tune and validate the numerical models. Roll stability was assessed by comparing static roll threshold and load transfer ratio values. All of the vehicles were shown to meet performance standards on a smooth surface, but introduction of surface roughness was shown to significantly decrease the roll stability of the trailer due to the lack of suspension.
Keywords: multibody dynamics; simulation; roll dynamics; TruckSim; roughness index; truck and trailer; model validation; static roll threshold; load transfer ratio; suspensionless trailer; roll stability.