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This paper employs the motion-mode energy method (MEM) to investigate the effects of a roll-plane hydraulically interconnected suspension (HIS) system on vehicle body-wheel motion-mode energy distribution. A roll-plane HIS system can directly provide stiffness and damping to vehicle roll motion-mode, in addition to spring and shock absorbers in each wheel station. A four degree-of-freedom (DOF) roll-plane half-car model is employed for this study, which contains four body-wheel motion-modes, including body bounce mode, body roll mode, wheel bounce mode and wheel roll mode. For a half-car model, its dynamic energy contained in the relative motions between its body and wheels is a sum of the energy of these four motion-modes. Numerical examples and full-car experiments are used to illustrate the concept of the effects of HIS on motion-mode energy distribution.

This paper presents the modeling and characteristic analysis of roll-plane and pitch-plane combined Hydraulically Interconnected Suspension (HIS) system. Vehicle dynamic analysis is carried out with four different configurations for comparison. They are: 1) vehicle with spring-damper only, 2) vehicle with roll-plane HIS, 3) vehicle with pitch-plane HIS and 4) vehicle with roll and pitch combined HIS. The modal analysis shows the unique modes-decoupling property of HIS system. The roll-plane HIS increases roll stiffness only without affecting other modes, and similarly pitch-plane HIS increases the pitch stiffness only with minimum influence on other modes. When roll and pitch plane HIS are integrated, the vehicle ride comfort and handling stability can be improved simultaneously without compromise. A detailed analysis and discussion of the results are provided to conclude the paper.

Regenerative braking has been widely accepted as a feasible option to extend the mileage of electric vehicles (EVs) by recapturing the vehicle’s kinetic energy instead of dissipating it as heat during braking. The regenerative braking force provided by a generator is applied to the wheels in an entirely different manner compared to the traditional hydraulic-friction brake system. Drag torque and efficiency loss may be generated by transmitting the braking force from the motor, axles, differential and, specifically in this paper, a two-speed dual clutch transmission (DCT) to wheels. Additionally, motors in most battery EVs (BEVs) and hybrid electric vehicle (HEVs) are only connected to front or rear axle. Consequently, conventional hydraulic brake system is still necessary, but dynamic and supplement to motor brake, to meet particular brake requirement and keep vehicle stable and steerable during braking.

This paper presents a robust controller design method for improving vehicle lateral stability and handling performance. In particular, the practical load variation will be taken into account in the controller synthesis process such that the controller can keep the vehicle lateral stability and handling performance regardless of the load variation. Based on a two-degree-of-freedom (2-DOF) lateral dynamics model, a model-based Takagi-Sugeno fuzzy control strategy is applied to design such a controller and the sufficient conditions for designing such a controller are given in terms of linear matrix inequalities (LMIs) which can be solved efficiently using currently available numerical software. Numerical simulations are used to validate the effectiveness of the proposed control approach.

Mainly motivated by developing cost-effective vehicle anti-roll systems, hydraulically interconnected suspension has been studied in the past decade to replace anti-roll bars. It has been proved theoretically and practically that hydraulic suspensions have superior anti-roll ability over anti-roll bars, and therefore they have achieved commercial success in racing cars and luxury sports utility vehicles (SUVs). However, since vehicle is a highly coupled complex system, it is necessary to investigate/evaluate the hydraulic-suspension-fitted-vehicle's dynamic performance in other aspects, apart from anti-roll ability, such as ride comfort, lateral stability, etc. This paper presents an experimental investigation of a SUV fitted with a hydraulically interconnected suspension under a severe steady steering maneuver; the result is compared with a same type vehicle fitted with anti-roll bars.

In order to make the active suspension more affordable, a novel low-cost active hydraulically interconnected suspension is developed, assembled and tested onto a sport utility vehicle. H∞ roll control strategy is employed to control vehicle body's roll motion. The hydraulic suspension model used for deriving the H∞ controller is estimated experimentally from the testing data. The active suspension model is then combined with the half-car model through their mechanical-hydraulic interface in the cylinders. The weighting function design of the H∞ control is provided. On a 4-post-test rig, the active suspension with H∞ control is validated with several road excitations. The test rig and experimental setup are explained and the obtained results are compared. The effectiveness of the designed H∞ controller is verified by the test data, with a considerable roll angle reduction in the three tests presented.

This study has proposed a new roll-resistant hydraulically interconnected suspension (HIS) system for a tri-axle straight truck with rear tandem axle bogie suspension to suppress the roll motion of truck body. The equations of motion of the mechanical and hydraulic coupling system are established by incorporating the hydraulic forces as external forces into the mechanical subsystem, in which the hydraulic forces are derived using impedance transfer matrix method and related to the state vectors of mechanical subsystem at the boundaries. Based on the derived equations of the coupling system, modal analysis method is employed to investigate the dynamic characteristics, including natural frequencies, mode shapes and dynamic responses. The results indicate that the proposed HIS system can effectively enhance the natural frequencies of truck body pitch and roll modes, and significantly increase the mode damping. The mode shapes of truck body are also changed.

A robust controller design method for vehicle roll control with variable speed and actuator delay is presented. Based on a three-degree-of-freedom (3DOF) yaw-roll model, the H∞ performance from the steering input to the vehicle body roll angle is considered. The design approach is formulated in terms of the feasibility of delay-dependent matrix inequalities. By combining the random search of genetic algorithms (GAs) and the efficient solution of linear matrix inequalities (LMIs), the state feedback controllers can be obtained. The approach is validated by simulations showing that the designed controllers can achieve good performance in roll control.

This paper introduces a vehicle model in CarSim, and replaces a portion of its standard suspension system with an HIS model built in an external software to implement co-simulations. The maneuver we employ to characterize the HIS vehicle is a constant radius method, i.e. observing the vehicle’s steering wheel angle by fixing its cornering radius and gradually increasing its longitudinal speed. The principles of the influence of HIS systems on cornering mainly focus on two factors: lateral load transfer and roll steer effect. The concept of the front lateral load transfer occupancy ratio (FLTOR) is proposed to evaluate the proportions of lateral load transfer at front and rear axles. The relationship between toe and suspension compression is dismissed firstly to demonstrate the effects of lateral load transfer and then introduced to illustrate the effects of roll motion on cornering.

Rollover prevention is one of the prominent priorities in vehicle safety and handling control. A promising alternative for roll angle cancellation is the active hydraulically interconnected suspension. This paper represents the analytical model of a closed circuit active hydraulically interconnected suspension system followed by the simulation. Passive hydraulically interconnected suspension systems have been widely discussed and studied up to now. This work specifically focuses on the active hydraulically interconnected suspension system. Equations of motion of the system are formalized first. The system consists of two separate subsystems that can be modeled independently and further combined for simulation. One of the two subsystems is 4 degrees of freedom half-car model which simulates vehicle lateral dynamics and vehicle roll angle response to lateral acceleration in particular.

Driven by stricter mandatory regulations on fuel economy improvement and emissions reduction, market penetration of electrified vehicles will increase in the next ten years. Within this growth, mild hybrid vehicles will become a leading sector. The high cost of hybrid electric vehicles (HEV) has somewhat limited their widespread adoption, especially in developing countries. Conversely, it is these countries that would benefit most from the environmental benefits of HEV technology. Compared to a full hybrid, plug-in hybrid, or electric vehicle, a mild hybrid system stands out due to its maximum benefit/cost ratio. As part of our ongoing project to develop a mild hybrid system for developing markets, we have previously investigated improvements in drive performance and efficiency using optimal gearshift strategies, as well as the incorporation of high power density supercapacitors.

In this paper, a new roll-plane hydraulically interconnected suspension (HIS) system is proposed to enhance the roll and lateral dynamics of a two-axle bus. It is well-known that the suspension tuning is of great importance in the design process and has also been explored in a number of studies, while only minimal efforts have been made for suspension tuning for the newly proposed HIS system especially considering lateral stability. This study aims to explore lateral dynamics and suspension tuning of a two-axle bus with HIS system, which could also provide valuable information for roll dynamics analysis. Based on a ten-DOFs lumped-mass full-car model of a bus either integrating transient mechanical-hydraulic model for HIS or the traditional suspension components, three newly promoted parameters of HIS system are defined and analyzed-namely the total roll stiffness (TRS), roll stiffness distribution ratio (RSDR) and roll-plane damping (RPD).

The vibration and instability experienced in an ambulance can lead to secondary injury to a patient and discourage a paramedic from emergency care. This paper presents a hydraulically interconnected suspension (HIS) system which can achieve enhanced cooperative control of roll, pitch and bounce motion modes to improve the ambulance's ride comfort and handling performance. A lumped-mass model integrated with a mechanical and hydraulic coupled system is developed by using free-body diagram and transfer matrix methods. The mechanical-fluid boundary condition in the double-acting cylinders is modelled as an external force on the mechanical system and a moving boundary on the fluid system. A special modal analysis method is employed to reveal the vibration characteristics of the ambulance with the HIS.

This paper proposes an approach to optimize the economy performance of a two-speed electric vehicle (EV) by combining gear shifting schedule design and gear ratios selection. Mathematic models for the two-speed EV subsystems are developed, including those of the battery module, electric machine, the driver, transmission and vehicle. Then a procedure for obtaining the optimal gear ratio pairs and corresponding shift schedule for the two-speed EV is presented in detail. The optimized EV powertrain parameters can not only ensure that basic requirements in dynamic performance are achieved, but realize the optimal economic performance of the EV as well. In order to investigate the effectiveness of the proposed method for EV design, simulations based on the developed powertrain model is conducted using different test driving cycles, including NEDC and constant speed. Results of these simulations validate the effectiveness of the proposed optimization method.

A detailed experimental study to quantitatively compare a roll-plane hydraulically interconnected suspension with anti-roll bar in articulation (warp) mode is presented in this paper. Anti-roll bar as part of conventional vehicle suspension system is a standard configuration widely used in road vehicles to provide the essential roll-stiffness to enhance vehicle handling and safety during fast cornering. However the drawback of anti-roll bar is apparent that they limit the wheels' travel on uneven road surface and weaken the wheel/ground holding ability, particularly in articulation mode. Roll-plane Hydraulically Interconnected Suspension (HIS) system, as a potential replacement of anti-roll bar, could effectively increase vehicle roll-stiffness and provide the tunable damping effect, without compromising vehicle's flexibility in articulation mode.

This paper presents a study on the dynamics and stability of a conventional powertrain with a Halt Toroidal (HT) type Continuously Variable Unit (CVU). A mathematic system model of the powertrain is assembled from parametric finite elemens that are formulated from lumped mass, torsional stiffness and damping and varying gear rations. Simulations have been carried out to investigate the transient behaviour of the powertrain. The damping within the system has been varied to investigate its effect on the dynamic stability of the powertrain. The obtained results show that transient responses of input and output rollers of the HT-CVU exist when clutch changes during vehicle acceleration period starting from stand-still condition. Sever or even unstable responses of HT-CVU take place if the damping is insufficient in HT-CVU and typres not only in the initial acceleration period but also in later period after the clutch change.

This paper presents a study on the dynamics and stability of a conventional powertrain with a Half Toroidal (HT) type Continuously Variable Unit (CVU). A mathematic system model of the powertrain is assembled from parametric finite elements that are formulated from lumped mass, torsional stiffness and damping and varying gear ratios. Simulations have been carried out to investigate the transient behaviour of the powertrain. The damping within the system has been varied to investigate its effect on the dynamic stability of the powertrain. The obtained results show that transient responses of input and output rollers of the HT-CVU exist when clutch changes during vehicle acceleration period starting from standstill condition. Severe or even unstable responses of HT-CVU take place if the damping is insufficient in HT-CVU and tyres not only in the initial acceleration period but also in later period after the clutch change.

The purpose of this paper is to present a concept of Hydro-Pneumatic Interconnected Suspension (HPIS) and investigate the unique property of the zero warp suspension stiffness. Due to the decoupling of warp mode from other modes, the road holding ability of the vehicle is maximized meanwhile the roll stability and ride comfort can be tuned independently and optimally without compromise. Ride comfort can be improved with reduced bounce stiffness and the progressive air spring rate can reduce the requirement of suspension deflection space. The roll stability can also be improved by increased roll stiffness. Vehicle suspension system modelling and modal analysis are carried out and compared with conventional suspension. The frequency response of tyres' dynamic load reveals that the proposed zero-warp-stiffness suspension enables the free articulation of front and rear axles at low frequency.

This paper presents a smart electric scooter system consisting of a microprocessor based vehicle controller (integrating an embedded regenerative braking controller), a 300W Permanent Magnet (PM) DC motor, two low-power DC-DC converters to form a higher power DC-DC converter pack, a motor controller, a supercapacitor bank and a capacitor cell balancing sub-system.

Electric vehicles (EV) are considered a practical alternative to conventional and hybrid electric passenger vehicles, with higher overall powertrain efficiencies by omitting the internal combustion engine. As a consequence of lower energy density in the battery energy storage as compared to fossil fuels powered vehicles, EVs have limited driving range, leading to a range phobia and limited consumer acceptance. Particularly for larger luxury EVs, electric motors with a single reduction gear typically do not achieve the diverse range of function needs that are present in multi-speed conventional vehicles, most notably acceleration performance and top speed requirements. Subsequently, multi-speed EV powertrains have been suggested for these applications. Through the utilization of multiple gear ratios a more diverse range of functional needs can be realized without increasing the practical size of the electric motor.