Tractor-semitrailer Combination Research Articles

Coordinated chassis control of a tractor-semitrailer combination operating at its handling limits using the MHA methodology

The performance benefits associated with coordinated control of a tractor-semitrailer combination are tested in this paper. More specifically, the paper evaluates performance as the number of available actuators is varied. Coordinating a large number of actuators to control articulated vehicles is a challenging task. To tackle this challenge effectively, a method that can be consistently applied across various levels of actuation is required. The modified Hamiltonian Algorithm (MHA) methodology is found to be suitable for the analysis. The method employs a multivariable nonlinear controller to provide steering and braking actuator inputs for simultaneous stability control and path following for articulated vehicles, even when operating in the nonlinear region of the tyres. This paper specifically investigates the potential performance benefits of using individual wheel braking compared to having limited control with regard to the semitrailer under challenging conditions. To achieve this, the original MHA technique is extended to be applicable to articulated vehicles. As a benchmark scenario, an autonomous safety-critical lane change manoeuvre on a low-friction road is performed by using a relatively simple steering controller. Simulation is conducted through co-simulation of Matlab/Simulink and TruckMaker. Results show that using individual wheel brake actuators for both units combined with automated steering can offer significant performance advantages compared to simpler chassis control strategies.

Safe operating envelope based on a single-track model for yaw instability avoidance of articulated heavy vehicles

The electrification of commercial vehicles has led to new wheel torque allocation options for propulsion and braking of articulated heavy vehicles. Each unit or axle can be individually braked or propelled whilst the other units or axles are excluded from such action. This may achieve the best energy efficiency. However, this can also lead to potential yaw stability problems such as jackknifing and trailer swing, especially under bad loading and weather conditions. This paper describes the above instabilities and introduces a nonlinear single-track model to study the vehicle dynamics of the tractor-semitrailer combination. The effects of different vehicle and environment parameters are analysed with this vehicle model. A safe operating envelope for limiting the wheel forces is obtained using this vehicle model. Since the vehicle model introduced in this paper is computationally effective, it can be run online in real vehicles, with an instantaneous safe operating envelope obtained for the momentary conditions. Thus, yaw instabilities such as jackknifing and trailer swing may be avoided.

Dual predictive model adaptive switching control for directional control of tractor semitrailer combinations

In order to ensure that safety and reliability of tractor semitrailer combinations (TSCs) on the road, the human drivers’ steering decisions need to comprehensively consider the trajectories and states of the tractor and semitrailer. For this purpose, a dual predictive model adaptive switching control decision for directional control is proposed. Firstly, a multi-point preview algorithm and a general regression neural network are designed to percept the current local target paths for the tractor and semitrailer. Then, a kinematic predictive model control algorithm for low-speed path tracking control and a dynamic predictive model control algorithm for high-speed path following and lateral stability control are established respectively. In addition, an S-type switching function is introduced to realize smooth switching between the two control algorithms. Finally, the directional control decision in this study is validated by the numerical simulations under different conditions and compared with single-point preview driver and the MPC driver without considering semitrailer. The results show that the proposed approach can accurately track the target path and effectively improve the high-speed lateral stability.

Camera-Based Articulation Angle Sensing for Heavy Goods Vehicles

Articulation angle sensing is an essential component of manoeuvrability and stability control systems for articulated heavy goods vehicles, particularly long combination vehicles. Existing solutions to this sensing task are limited by reliance on trailer modifications or information or by measurement accuracy, or both, restricting commercial adoption. In this paper we present a purely tractor-based sensor concept comprising a rear-facing camera and the parallel tracking and mapping (PTAM) image processing algorithm. The system requires no prior knowledge of or modifications to the trailer, is compatible with planar and non-planar trailer shapes, and with multiply-articulated vehicle combinations. The system is validated in full-scale vehicle tests on both a tractor semi-trailer combination and a truck and full-trailer combination, demonstrating robust performance in a number of conditions, including trailers with non-planar geometry and with minimal visual features. Average RMS measurement errors of 1.19, 1.03 and 1.53 degrees were demonstrated for the semi-trailer and full-trailer (drawbar and semi-trailer) respectively. This compares favourably with the state-of-the-art in the published literature. A number of improvements are proposed for future development based on the observations in this research.

Braking of the tractor-semi-trailer set in a rectilinear motion

Because of the increasing share of cargo movement using road transport, the issue of safety hazards related to the movement of trucks and road sets remains an essential element of the overall road safety system. Braking is the primary defensive maneuver in accident situations. The main purpose of this work is to present a simulation method for assessing potential hazards occurring during the braking of an articulated vehicle (tractor-semitrailer combination). A relatively simple, quasistatic mathematical model of road vehicle set braking was presented. Several qualitative and quantitative criteria for safety evaluation were proposed, and a series of exemplary calculations illustrated with time characteristics of the quantities describing the road vehicle set movement. These calculations show that the proposed method may be helpful for the assessment of braking safety depending on the selected factors relating to the operational condition (the way the trailer is loaded, failure of the brake system, road surface condition).

A new approach in modelling of hitch joint of a tractor semi-trailer using virtual Pacejka tyre model

In this study, a new approach in modelling of hitch joint of a tractor semi-trailer is proposed by adopting virtual Pacejka tyre model. The virtual Pacejka tyre model is connected with a 16 DOF tractor semi-trailer combinations in Matlab-Simulink software and verified using validated software known as TruckSim. Two sets of simulations are conducted in the verification process which involves a double lane change (DLC) and steep steer cornering (SSC) test. It is observed from the results that by modelling hitch joint as a virtual Pacejka tyre model, the behaviour of the developed model closely follows the behaviour of the validated TruckSim model.

Energy Conservation Measures in Heavy Trucks Freight Transport

Since the independence of South Sudan, Sudan lost 75% of its oil reserves, this led to major fuel shortages country wide, the fuel shortage raised the fuel prices and the overall transport prices. Scarcity led to black market trade of fuel specially in states away from the Capital City (Khartoum). Managing the available stock comes first before increasing the supply amount in order to solve the problem, one of the major fuel consumers to be managed is the transport sector specially the long haulage freight transport. Moving freight in Sudan is constrained by inadequate infrastructure and high costs. This paper covers specifically the long haulage freight transport between Khartoum State and Western side of the country (Darfur Region), Contributing to manage fuel consumption for trucks, taking into account trucks types used, roads, environmental impacts and mitigation measures applicable to save fuel . The results showed that the primary reason for the excessive fuel consumption is the usage of the rigid trucks (lorries) for transport specially the Hino700 series, this truck type, overload and absence of weight stations and control policies contributed significantly to deterioration of roads and transport efficiency decreasing. First step towards the solution would be in upgrading roads infrastructure assuring high quality along with enforced weight regulations and weight stations to protect roads from damages. High quality roads shall ease the usage of different truck types with different configurations. Then stablish a policy to force replacement of the low efficiency lorry truck types with high quality tractor semi-trailer combinations.

Fuel economy improvement by means of two European tractor semi-trailer combinations in a platooning formation

Two track tests were performed using European cab over vehicles in a two vehicle platoon to determine the aerodynamic benefits of driving in a platoon. The first test, performed in January tested following distances of 10, 20, 30, 40 & 50 m. As the adaptive cruise control was inoperative, the distance was measured using radar, and manually controlled. Weather conditions were wintery and wind speeds were above average, leading to yaw angles of 5°. Fuel measurements using CAN bus data showed that the leading vehicle experienced no savings for following distances other than 10 m. For the following vehicle, at the largest distance of 50 m savings of 9.0 ± 2.8% were achieved. Decreasing the distance to 40, 30 and 20 m did not yield any significant savings over a following distance of 50 m. At a separation distance of 10 m the savings increased somewhat to 10.6 ± 3.1%.The second experiment was conducted during August, with more stable conditions. Wind speeds were low, and the resulting experienced yaw angles were below 2°. During the second test, the adaptive cruise control was used to maintain the distance. The distances of the first test were repeated with an additional distance of 70 m. The results showed similar results for the Leading vehicle, no significant savings for any of the separation distances except the 10 m separation distance, which resulted in a saving of 4.0 ± 0.7%. The savings achieved with the following vehicle were generally higher than those achieved in the first test. For 50, 40, 30 and 20 m the results were around 1.5% higher than in Test 1. For 10 m separation distance, the result achieved (10.1 ± 0.9%) was lower than the result at 20 m distance, and similar to the value achieved in Test 1. The authors suggest that the difference results between the two tests can be attributed to the difference in wind conditions, and the resulting difference in yaw angles. As there were significant differences between the two tests in weather and road conditions and setup, such as different tractor and trailers, distance control method, the authors cannot determine a single cause. The results achieved with the leading vehicle match the results of literature well. For the following vehicle there is more spread in the existing work, and the data matches the lower end of the spread well. The authors conclude that for the range of separation distances tested the leading vehicle gains from the closer following distances, but that for the following vehicle close proximity platooning has a limited potential for improving fuel consumption over current day legal platooning distances.

Semitrailer Steering Control for Improved Articulated Vehicle Manoeuvrability and Stability

Abstract Articulated heavy vehicles have some specific performance limitations and safety risks due to their special dynamic characteristics. They show poor manoeuvrability at low speeds and may lose their stability in different manners at high speeds. In this study, the potential of active steering control of the semitrailer on manoeuvrability and stability of tractor-semitrailer combinations is investigated. A linear bicycle model and a nonlinear version are used for controller design and vehicle dynamic simulation in MATLAB environment. The Linear Quadratic Regulator optimal state feedback control is used to minimise the tracking error at low-speed, and regulate Rearward Amplification ratio and roll at high-speed. Quantum Particle Swarm Optimisation is used for optimising the weighting factors. Three different control algorithms are introduced and it is demonstrated through simulations that the vehicle with the proposed steering control exhibits desirable improvements compared to the baseline vehicle.

Modelling and verification of tractor ride model

This project focuses on the modelling and verification of a tractor ride model as a part of tractor semi-trailer combination ride model development. The tractor ride model is established based on the three-axle tractor. The tractor ride model equations of motion, which consist of three degrees of freedom (DOF) of body motions and six DOF of unsprung mass motions are derived. The developed tractor ride model is simulated in Matlab-Simulink software. TruckSim software is used to verify the developed ride model by conducting the simulation on flat road condition. The vehicle model is simulated to travel at 90 km/h and hits 10 cm bump. The results of the study show that the dynamic behavior of the developed tractor ride model is closely followed the TruckSim tractor ride dynamic behavior. The percentage differences of RMS values between the developed and TruckSim model for all investigated parameters are less than 5%. It provides the confidence of utilizing the developed model established in this study for the purpose of developing the tractor semi-trailer combination model.

Assessing the influence of the road-tire friction coefficient on the yaw and roll stability of articulated vehicles

This article addresses the yaw stability of articulated vehicles by assessing the influence of the road-tire friction coefficient on the convergence region of a particular equilibrium condition. In addition, the boundaries of this region are compared to the boundaries of the non-jackknife and non-rollover regions to distinguish the instability phenomenon, jackknife or roll-over, responsible for this delimitation. The vehicle configuration considered in this analysis is composed by one tractor unit and one towed unit connected through an articulation point, for instance, a tractor-semitrailer combination. A nonlinear articulated bicycle model with four degrees of freedom is used together with a nonlinear lateral force tire model. To estimate the convergence region, the phase trajectory method is used. The equations of motion of the mathematical model are numerically integrated for different initial conditions in the phase plane, and the state orbits are monitored in order to verify the convergence point and the occurrence of instability events. In all cases, the longitudinal force on each tire, such as traction and braking, is not considered. The results show the existence of convergence regions delimited only by jackknife events, for low values of the friction coefficient, and only by rollover events, for high values of the friction coefficient. Moreover, the transition between these two conditions as the friction coefficient is changed is graphically presented. The main contributions of this article are the identification of the abrupt reduction of the convergence region as the value of the friction coefficient increases and the distinction of the instability events, jackknife or rollover, that define the boundaries of the convergence region.

The effect of steering-system linearity, simulator motion, and truck driving experience on steering of an articulated tractor-semitrailer combination

Steering systems of trucks consist of many linkages, which introduce nonlinearities that may negatively affect steering performance. Nowadays, it is possible to equip steering systems with actuators that provide artificial steering characteristics. However, before new steering systems are deployed in real vehicles, evaluation in a safe and controlled simulator environment is recommended. A much-debated question is whether experiments need to be performed in a motion-base simulator or whether a fixed-base simulator suffices. Furthermore, it is unknown whether simulator-based tests can be validly conducted with a convenience sample of university participants who have not driven a truck before. We investigated the effect of steering characteristic (i.e., nonlinear vs. linear) on drivers' subjective opinions about the ride and the steering system, and on their objective driving performance in an articulated tractor-semitrailer combination. Thirty-two participants (12 truck drivers and 20 university drivers) each completed eight 5.5-min drives in which the simulator's motion system was either turned on or off and the steering model either resembled a linear (i.e., artificial) or nonlinear (i.e., realistic) system. Per drive, participants performed a lane-keeping task, merged onto the highway, and completed four overtaking manoeuvers. Results showed that the linear steering system yielded less subjective and objective steering effort, and better lane-keeping performance, than the nonlinear system. Consistent with prior research, participants drove a wider path through curves when motion was on compared to when motion was off. Truck drivers exhibited higher steering activity than university drivers, but there were no significant differences between the two groups in lane keeping performance and steering effort. We conclude that for future truck steering systems, a linear system may be valuable for improving performance. Furthermore, the results suggest that on-centre evaluations of steering systems do not require a motion base, and should not be performed using a convenience sample of university students.

CONVENIENT – Complete Vehicle Energy Saving Technologies for Heavy Trucks

This article presents an overview of the interim results achieved in the FP7 project CONVENIENT “Complete Vehicle Energy Saving Technologies for Heavy Trucks” (No.312314) which started in November 2012 and concludes April 2016.From the customer viewpoint, fuel efficiency is top priority because of its significant impact in terms of cost (in the EU, fuel represents about 30% of the Total Operating Costs for a 40-ton tractor-semitrailer combination). Correspondingly, the CONVENIENT project targets a 30% reduction of fuel consumption in vehicles for long-distance freight transport by developing innovative heavy-trucks featuring a suite of innovative energy-saving technologies and solutions by adopting a holistic approach to on-board energy management, considering the tractor, semi-trailer, driver and the mission as a whole.The objective has been to achieve complete vehicle energy management by proposing highly innovative solutions for improved efficiency and enhanced integration of components currently designed independently, integrated and evaluated directly on validator vehicles including energy efficient sub-systems, energy harvesting and active/passive aerodynamics devices.The CONVENIENT Consortium comprises three major EU truck manufacturers, ten Tier 1/2 suppliers, and a network of nine research centres and Universities, representing European excellence in the field of long distance transport R&D.

Simulation of a partly filled tank vehicle combination in TruckSim and tank design optimisation

A simulation platform is developed for analysis of directional dynamics of partly filled tank vehicle combinations by integrating a steady-state fluid slosh model of the partly filled tank to TruckSim software. A modified Reuleux-triangle tank cross-section with a curved bottom is further proposed to achieve reduction in mass centre height and to adapt to current designs of saddle mounts. The coupled tank-vehicle simulation platform is used to evaluate roll dynamic performance of a six-axle tractor-semitrailer combination with the proposed tank cross-section considering different cargo fill volumes. The roll performances, evaluated in terms of steady rollover threshold, lateral load transfer and peak directional responses, are further compared with those of currently used tank cross-sections. The comparisons suggested that the modified Reuleux-triangle tank can yield improved roll performance. Furthermore, the coupled tank-vehicle simulation platform could serve as an effective virtual design and simulation tool for parametric design of partly filled tank trucks.

Heavy Truck Driver Workload Investigation

ABSTRACT Driver workload is of growing interest in the automotive society, since the number of in-vehicle technologies and vehicles on the road grows. Operational and environmental factors impact the driver's ability to negotiate a chosen course and place heavy demands on the driver in terms of mental and physical capacity. A key component of the driver's operating environment is the vehicle. In this research, the impact of various tire configurations, for example, dual and wide based, for a Class 8 tractor–semitrailer combination vehicle on driver workload performance is presented. Driver workload performance is assessed during four maneuvers: 60 m radius steady state circle, 120 m radius steady state circle, road course, and North Atlantic Treaty Organization emergency lane change maneuver. Surface electromyography (sEMG) electrodes were placed on the left and right wrist flexors (flexor carpi ulnaris) and right wrist extensors (extensor carpi ulnaris) in order to capture muscle activity during all maneuvers. Peak and integrated values of sEMG are calculated to obtain metrics of driver workload. Results of the study show distinct separation of muscle activity for each tire configuration. Differences in driving techniques were also identified based on the dominant hand of the driver and orientation of the maneuver, that is, clockwise or counterclockwise.

An improvement in rollover detection of articulated vehicles using the grey system theory

A Rollover Index combined with the grey system theory, called a Grey Rollover Index (GRI), is proposed to assess the rollover threat for articulated vehicles with a tractor–semitrailer combination. This index can predict future trends of vehicle dynamics based on current vehicle motion; thus, it is suitable for vehicle-rollover detection. Two difficulties are encountered when applying the GRI for rollover detection. The first difficulty is effectively predicting the rollover threat of the vehicles, and the second difficulty is achieving a definite definition of the real rollover timing of a vehicle. The following methods are used to resolve these problems. First, a nonlinear mathematical model is constructed to accurately describe the vehicle dynamics of articulated vehicles. This model is combined with the GRI to predict rollover propensity. Finally, TruckSim™ software is used to determine the real rollover timing and facilitate the accurate supply of information to the rollover detection system through the GRI. This index is used to verify the simulation based on the common manoeuvres that cause rollover accidents to reduce the occurrence of false signals and effectively increase the efficiency of the rollover detection system.

Kinematic and dynamic analysis of a heavy truck with individual front suspension

The main focus of this work is on the characteristics of a commercial vehicle with individual front suspension (IFS). Both kinematic and dynamic properties of the vehicle are investigated through simulations and analytical expressions. Moreover, employing the model of the tractor semitrailer combination, the study presents the results of comparison between the trucks with IFS and rigid front axle with respect to comfort and handling. This is done by analysing the responses of the vehicles to different road and steering inputs. The obtained results show enhanced comfort and steering feeling for the truck with IFS.

Directional stability of tractor-semitrailers versus truck-full trailers

Recently the road transport in Egypt has been subjected to an intensive debate concerning the heavy vehicle’s safety predominantly due to the arising rates of their fatal accidents. Numerous aspects are involved such as the driver, the infrastructure of the national roads and the wide diversity of heavy vehicle configurations. This controversy has been given up recommending the deterrence of the truck full-trailer and stimulating the dependency of heavy transportation on tractor semi-trailer combinations. This paper presents a technical comparison of the dynamic performance of both combinations during different standard manoeuvres and loading scenarios. Furthermore, the international standards to measure and assess the heavy vehicle performance are outlined. The paper exemplifies a scientific algorithm to examine the heavy vehicle design against the requirements of the international standards by means of computer simulation modelling. The directional stability of such combinations has been numerically simulated using the validated yaw/roll model. The finding of the paper complies with the governmental trend to stop the use of full-trailers due to their poor directional stability.

Wind tunnel tests on heavy road vehicles: Cross wind induced loads—Part 1

In the recent years, rollover has become an important safety issue for a large class of vehicles. Even though rollovers constitute a small percentage of all accidents, they have unproportionally large contribution to severe and fatal injuries. Under this point of view, rollover of heavy vehicles is particularly critical being associated with large traffic disruption, economic loss and risks connected to the transported goods. One of the main causes for heavy vehicles rollover is recognised to be cross wind. In order to determine which parameters (geometry and vehicle type, infrastructure scenario, turbulence conditions, etc.) most affect the aerodynamic loads acting on heavy vehicles, a comprehensive experimental campaign has been carried out in the Politecnico di Milano wind tunnel. The overall activity is presented in 2 papers. In this first paper attention is focused on a high-sided lorry in flat ground scenario. Mean aerodynamic forces and moments have been measured by means of a six-components dynamometric balance for different yaw angles and turbulence conditions. Moreover, in order to gain an insight of the flow pattern around the vehicle, pressure distribution on the vehicle surface has been measured. Finally, the vehicle aerodynamic admittance function has been assessed, for high turbulence conditions, to investigate the unsteady force/moment component. The second paper deals with the effect of infrastructure scenario (flat ground, embankment, double and single viaduct), of position (vehicle placed upwind or downwind) and of vehicle geometry/type (high-sided lorry with and without a trailed unit, tractor-semitrailer combination and tank truck) on the aerodynamic forces and moments, including both steady and unsteady components.

Wind tunnel tests on heavy road vehicles: Cross wind induced loads—Part 2

The sensitivity of heavy road vehicle aerodynamic coefficients to different testing parameters (scenario, vehicle type and turbulence intensity) is experimentally evaluated in this paper through wind tunnel experiments. The first part of the paper has investigated the aerodynamic loads (both stationary and non-stationary) acting on a high-sided lorry (VAN) in a flat ground scenario. The mean aerodynamic coefficients, the flow pattern around the vehicle and the aerodynamic admittance function have been assessed and compared for different wind turbulence conditions (boundary layer simulations). The present paper instead investigates the influence of the infrastructure scenario (flat ground, embankment, single and double viaduct), of the exposition (upwind or downwind) and of a trailed unit on the aerodynamic loads acting on the vehicle. Moreover, the mean aerodynamic coefficients and the aerodynamic admittance function of the high-sided lorry considered in the first part are compared with the ones of other heavy vehicles (tank truck, tractor–semitrailer combination and tractor–trailer combination) to assess the influence of the vehicle geometry.