Looking at the future trends of the road traffic, one will recognize that the commercial vehicle participation will not decrease, although it is required from the environmental and social viewpoints. The reason is that the other means of freight transport (water, railway, air) do not provide the same flexibility as the road transport, and direct business interest of those companies, who are using this transport form is larger than the eventual loss caused by the penalties to be paid (taxes, compensation of higher axle load). This conflict is hard to solve, but the effect can be minimized. The commercial vehicle industry attempts to introduce systems to the vehicles, which are targeting on reduction of the environmental impacts caused by heavy vehicles. These systems, which are named generally as “intelligent chassis systems”, electronically control the operation of the chassis subsystems (engine, transmission, brake, suspension) and co-ordinate their operation on a higher level (vehicle controller, intell...

Intelligent Electronic Systems in Commercial Vehicles for Enhanced Traffic Safety

Highway safety and vehicle performance are two important considerations in the design of a heavy vehicle combination. In this paper a performance measure called the 'rearward amplification' (RWA) is used as a control criterion in the design of a vehicle-handling controller. This approach is different to conventional control techniques. The RWA is defined as the ratio of the peak lateral acceleration at the rearmost trailer's centre of gravity (CG) to that of the lead unit during a lane-change manoeuvre. The vehicle under consideration is a six-axle truck/full trailer, which usually exhibits a high level of RWA leading to roll-over during obstacle avoidance manoeuvres. In this study, several control strategies are examined, namely active yaw control at the truck CG, active yaw control at the dolly CG and active yaw control at the trailer CG. These could be employed individually or in combination. The effect of an active control torque applied to various vehicle units is examined by using an optimal linear quadratic regulator approach combined with a simplified four degrees-of-freedom linear vehicle model. The controller performance index parameters are determined for the vehicle based on acceptable RWA target values. The sensitivity of the controller to tyre cornering stiffness variation is further evaluated. Simulation results indicate that the RWA can be reduced without significant change of the uncontrolled vehicle trajectory when active yaw torque is applied to the dolly. The controller can be more effective in improving the dynamic performance and roll stability of this type of commercial vehicle, if applied to the lead unit (truck) or to the last unit (trailer). However, the path of the vehicle will be strongly influenced and driving difficulties can be experienced. For active yaw control at the dolly CG, the optimal controller is found to be most sensitive to the dolly's tyres' cornering stiffness variations and least sensitive to steering axle from the RWA point of view. It is also found that the controller is most sensitive to steering axle parameter variations for path following. (A)

Sensitivity of rearward amplication control of a truck/full trailer to tyre cornering stiffness variations

This paper presents the results of a parametric sensitivity analysis of a five-axle tractor-semitrailer vehicle combination using 3-DOF linear yaw/plane model. The first order logarithmic sensitivity functions are derived with respect to several vehicle design parameters. For stabilization of the vehicle's directional behaviour a fairly new control concept called "Active Unilateral Braking Control (AUBC)" acting on the tractor rear wheel's in order to produce a stabilizing yaw torque is investigated. The AUBC system improves not only the directional stability, but also affects the roll dynamics of the vehicle. The sensitivity of the controlled vehicle system with linear quadratic controller (LQR) is also examined, a robust controller design procedure is proposed as a result of the sensitivity analysis. The robustness of this controller in the presence of both internal (including parametric uncertainties, non-linear dynamics) and external disturbances (such as road irregularities and side wind) allows its implementation with confidence with a non-linear vehicle model. The applicability of this control system to a non-linear vehicle model is tested using a 34 DOF, non-linear vehicle model of the tractor-semitrailer combination. (A)

Design of an active unilateral brake control system for five-axle tractor-semitrailer based on sensitivity analysis

Heavy vehicles play an economically important role in the transportation process, and their numbers have been increasing for several decades. The active safety of the highway system is an important consideration in the design of a heavy vehicle combination. In this paper, the handling characteristics of a 5-axle tractor-semitrailer is examined and used to test for the desired features of the vehicle's handling and stability. Using these results the optimal control criterion is derived for the vehicle. Four different control strategies are examined by using the Linear Quadratic Regulator (LQR) approach. These are, active steering of the rear wheels of the tractor; active steering of the wheels of the trailer; active torque control in the fifth-wheel joint; and active yaw torque acting on the tractor. These controllers are designed and examined using a simplified linear vehicle model. In addition to discussing the above-mentioned approaches, this paper discusses a method of modifying the slip angles at the tractor's rear (driven) axles, however the yaw torque at the tractor cg also can be controlled using what is called unilateral braking. As well, the replacement of the active torque control at the fifth wheel joint, by a control strategy based on the usage of controllable dampers at the fifth-wheel joint, will also be examined. In this case, a nonlinear mathematical model of the vehicle is used and a modified control strategy called the RLQR/H∞ approach is used to ensure the vehicle's performance in the presence of parametric uncertainties. The examination of these control strategies is conducted by using a sophisticated non-linear vehicle model, and the influence of these control strategies on the vehicle's directional and roll stability during severe path-follow lane-change manoeuvre is discussed.

Examination of Different Control Strategies of Heavy-Vehicle Performance

This paper presents a new approach for autonomous reversing of a tractor-semitrailer vehicle called minimum swept path control (MSPC). MSPC improves the performance of previous path following control (PFC) strategies, by minimizing the maximum excursion of the vehicle, while guaranteeing acceptable path following accuracy. A linear controller is devised, combining state feedback control with an optimized preview distance. A relationship between the maximum lateral offsets of the front axle of the tractor unit and the rear axle of the last trailer and the corresponding weights in the control cost function is established, and the controller is tuned to provide the best performance compromise. Several simulations of a tractor-semitrailer case are run, and the results show that the overall swept path width is reduced by more than 40% when compared with PFC methods.

Minimum Swept-Path Control for Autonomous Reversing of a Tractor Semi-Trailer

SUMMARY This paper describes the stabilization of articulated vehicles at high speeds by a steering system set up on the trailer. First, the equations of motion of the articulated vehicles with a steering system on the trailer were obtained. Furthermore, the steering angle of the trailer in the presence of disturbances was studied by solving these equations through the application of modern control theory. From such analysis, the magnitude of the optimal feedback coefficients of each state variable was obtained. It was found that the stability of articulated vehicles at high speeds was significantly improved by the active control method for the trailer steering system. However, the active control system needs a power supply, and it is difficult to apply it to articulated vehicles at present, especially for passenger car-trailer combinations. Thus, a new trailer steering system with viscous coupling arms to be set between the tractor and trailer was proposed. Furthermore, the semi-active control method whi...

Stabilization of articulated vehicles by semi-active control method

SUMMARY This study deals with the establishment of a theory of backward motion of multi-articulated vehicles and their control. First, a theory of backward motion of multi-articulated vehicles was studied under geometrical motion, and verified by experiments. Then, the conditions which design specifications had to satisfy were given from controllability, and control limits from the maximum steering angle. Using the optimal control theory, the maneuverability of multi-articulated vehicles was discussed, and the difficulty of backward maneuverability with an increase in the number of articulated vehicles was shown. On the basis of these study results, the effectiveness of an auxiliary operation system was suggested.

Yasushi Saito

Papers

Stabilization of articulated vehicles by semi-active control method

On the Backward Maneuverability of Articulated Vehicles