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There is an increased interest in the use of cellulose nanocrystal (CNC) films and coatings for a range of functional applications in the fields of material science, biomedical engineering, and pharmaceutical sciences. Most of these applications have been demonstrated on films and coatings produced using laboratory-scale batch processes, such as solvent casting, dip coating, or spin coating. For successful coating application of CNC suspensions using a high throughput process, several challenges need to be addressed: relatively high viscosity at low solids content, coating brittleness, and potentially poor adhesion to the substrate. This work aims to address these problems. The impact of plasticizer on suspension rheology, coating adhesion, and barrier properties was quantified, and the effect of different pre-coatings on the wettability and adhesion of CNC coatings to paperboard substrates was explored. CNC suspensions were coated onto pre-coated paperboard in a roll-to-roll process using a custom-built slot die. The addition of sorbitol reduced the brittleness of the CNC coatings, and a thin cationic starch pre-coating improved their adhesion to the paperboard. The final coat weight, dry coating thickness, and coating line speed were varied between 1–11 g/m 2 , 900 nm–7 µm, and 2.5–10 m/min, respectively. The barrier properties, adhesive strength, coating coverage, and smoothness of the CNC coatings were characterized. SEM images show full coating coverage at coat weights as low as 1.5 g/m 2 . With sorbitol as plasticizer and at coat weights above 3.5 g/m 2 , heptane vapor and water vapor transmission rates were reduced by as much as 99% and 75% respectively. Compared to other film casting techniques, the process employed in this work deposits a relatively thick coating in significantly less time, and may therefore pave the way toward various functional applications based on CNCs. Graphical abstract

This paper presents a method to design a robust controller for rollover prevention. Several types of controllers for rollover prevention have been proposed in such a way to minimize the lateral acceleration and the roll angle. The rollover prevention capability of these controllers can be enhanced if the controlled vehicle system is robust to the variation of the height of the center of gravity (C.G.) and the speed of the vehicle. With this idea, a robust controller is designed with linear quadratic static output feedback and parameter sensitivity reduction scheme. Differential braking and an active suspension system are adopted as actuators that generate yaw and roll moments, respectively. The proposed method is shown to be effective in preventing rollover through simulations on the nonlinear multi-body dynamic simulation software, CarSim®.

Abstract Tubular-type torsion beam rear-suspension systems are widely used in small passenger cars owing to their compactness, light weight, and cost efficiency. It is already known that the roll behaviour of a torsion beam suspension system can be approximated to that of a semitrailing arm suspension system. By this kinematic assumption, analytical equations to obtain the roll centre height, roll steer, and roll camber have already been developed in terms of geometry points. Therefore, this paper proposes an analytical method to calculate the torsional stiffness of a tubular beam from its cross-section area based on the assumption that a tubular beam is a series connection of finite lengths with a constant cross-section. In addition, a potential energy method is proposed to calculate the roll stiffness of a tubular torsion beam suspension system based on considering the bushing stiffness and torsional stiffness of the tubular beam without the use of any commercial computer-aided engineering (CAE) software. The torsional stiffness and roll stiffness predicted using the proposed method showed errors of about 4 per cent and 3.3 per cent respectively, when compared with results from commercial CAE software.

Abstract The use of anti-roll bars to provide additional roll stiffness and therefore to reduce the trade-off between ride and rollover performance has previously been studied. However, little work has been carried out to investigate the benefits of a switchable roll stiffness. Such a semi-active anti-roll system has the ability to have a low roll stiffness during straight-ahead driving for improved ride performance and high roll stiffness during cornering for improved roll performance. Modelling of such a system is conducted and the model is validated against a semi-active anti-roll system fitted to an experimental vehicle. Experimental and theoretical investigations are used to investigate the performance of such a system with several different strategies employed to switch to the high-stiffness state. The use of an air suspension on the vehicle to roll into corners is also investigated, as is the possibility of exploiting the road layout by allowing the vehicle to be in a low-roll-stiffness configuration during a corner, and then to switch to the high-roll-stiffness configuration midcorner, hence ‘locking in’ a roll angle. The best rollover performance improvement that was achieved was 12.5 per cent.

Abstract A yaw moment control system is developed for a front-wheel-drive vehicle utilizing two brushless d.c. electric motors embedded in the rear wheels. An optimal linear quadratic regulator (LQR) controller is employed by using a four-degrees-of-freedom (4DOF) linear vehicle model. The objective is to include important effects of roll and steering into the controller design. A two-degrees-of-freedom (2DOF) optimal LQR model is also used for comparison purposes. For the simulation of system at different conditions, a non-linear eight-degrees-of-freedom vehicle model is used. The performances of the controlled vehicle have been compared with those of the uncontrolled vehicle in order to investigate the effectiveness of the proposed controllers. Simulation results indicate that, in normal situations where the uncontrolled vehicle becomes unstable, the controlled vehicles with both 2DOF and 4DOF controllers show stable responses. In severe conditions, however, even the 2DOF controller fails to stabilize the vehicle, whereas the 4DOF controller is successful in maintaining the stability of vehicle.

Abstract Reducing the vibration of an automotive magnetorheological (MR) suspension system can contribute greatly to enhancing vehicle performance. However, it is difficult to design a control system that depends on a complicated whole-vehicle vibration model. This paper proposes a hierarchical controller that consists of a control level and a coordination level for heave, roll, and pitch vibration control of a vehicle with an MR suspension system. On the control level, a local fuzzy controller is designed for each quarter-vehicle MR suspension system, based on a hybrid control strategy of skyhook control and groundhook control. On the coordination level, a coordination controller is designed to tune four local independent fuzzy controllers by adjusting their output parameters on the basis of system feedback. A test and control system for MR suspensions is set up and implemented on a minibus equipped with four controllable MR dampers. The results on random rough roads confirm that the hierarchical controller can reduce automotive vertical vibration, roll motion, and pitch motion more effectively than a passive suspension or an MR suspension using a hybrid control strategy. It achieves better ride comfort and automobile handling stability, although data for bump input indicate that the hierarchical controller does not decrease automotive vertical vibration more effectively than hybrid control or a passive system. However, it yields better results in decreasing pitch and roll motions.

A new experimental articulated vehicle with computer-controlled suspensions is used to investigate the benefits of active roll control for heavy vehicles. The mechanical hardware, the instrumentation, and the distributed control architecture are detailed. A simple roll-plane model is developed and validated against experimental data, and used to design a controller based on lateral acceleration feedback. The controller is implemented and tested on the experimental vehicle. By tilting both the tractor drive axle and the trailer inwards, substantial reductions in normalized lateral load transfer are obtained, both in steady state and transient conditions. Power requirements are also considered.

Abstract A general purpose numerical model, suitable for simulating the yaw—roll behaviour of torsionally flexible heavy goods vehicles with an arbitrary arrangement of vehicle units, is presented. A controllability analysis is then performed to examine the fundamental limitations in achievable roll stability of heavy vehicles with active roll control systems. It is established that it is not possible to control simultaneously and independently all axle load transfers and body roll angles. The best achievable control objective for maximizing roll stability is shown to be setting the normalized load transfers at all critical axles to be equal, while taking the largest inward suspension roll angle to the maximum allowable angle. The results of a simulation of a tractor—semitrailer vehicle with a full—state feedback active roll control system are presented. It is shown that the roll stability of the vehicle can be increased by 30-40 per cent for steady state and transient manoeuvres and that the handling performance improves significantly.

Abstract The rollover stability of tank vehicles depends on a number of factors that result in a lateral shift of the centre of gravity, which influences roll dynamics in cornering. The most important factors are the height of the centre of gravity, the track width, the axle roll stiffness, suspension and tyre compliance, and suspension roll stiffness. A tilt table test and, alternatively, a calculation method are suggested for implementation by United Nations Economic Commission for Europe (UNECE) Regulation 111. In Greece, no available approved testing rig is available to carry out the required tests for the conformity of those vehicles with Regulation 111 and, consequently, the calculation method is almost exclusively adopted. However, the calculation method for Regulation 111 still remains a theoretical way to check the vehicle behaviour owing to the large number of non-validated physical parameters involved. Thus, there is a lack of reliability between results obtained by the calculation method from different inspection bodies for similar vehicles. A combined experimental and calculation method that determines the overall torsion-angular displacement relation for a vehicle on an inclined level under its own weight is discussed, and results of the application of this method in a large series of various types of road tanker are presented in this paper.

This paper presents the development of a prediction method for vehicle dynamic behaviour characteristics using screw axis theory. A vehicle model is developed for quasi-static analysis which is applied to vehicles of three different suspension configurations under cornering conditions in which a specific lateral force acts. A finite screw axis is determined using quasi-static analysis based on a rigid body displacement of the vehicle model with respect to the ground. The fixed screw axis surface formed by the migration of the finite screw axis is also determined. The shape of the fixed screw surface shows that the fundamental characteristics of vehicle roll behaviour is determined not by suspension tuning element but by suspension geometry. The gradients of screw parameters with respect to lateral force when the vehicle model behaves in an initial cornering state are proposed as prediction parameters of vehicle dynamic motion. The dynamic analysis result shows that vehicle dynamic motion characteristics can be successfully predicted by the proposed parameters.