This paper provides an overview of the latest advances in road vehicle suspension design, dynamics, and control, together with the authors' perspectives, in the context of vehicle ride, handling, and ...stability. The general aspects of road vehicle suspension dynamics and design are discussed, followed by descriptions of road-roughness excitations with a particular emphasis on road potholes. Passive suspension system designs and their effects on road vehicle dynamics and stability are presented in terms of in-plane and full-vehicle arrangements. Controlled suspensions are also reviewed and discussed. The paper concludes with some potential research topics, in particular those associated with the development of hybrid and electric vehicles.
This paper presents a novel control strategy for nonlinear uncertain vehicle active suspension systems without using any function approximators e.g., neural networks (NNs) or fuzzy logic systems ...(FLSs). Unlike previous results that neglect the effect of actuator dynamics, this paper incorporates the dynamics of a hydraulic actuator that is used to create the required active suspension forces into the controller design. To address the nonlinearities of this hydraulic system, an approximation-free control method is introduced. In this method, the widely used NNs and FLSs are not needed. This leads to reduced computational burden and complexity, and thus, it is more suited for practical applications. Moreover, by introducing a prescribed performance function and the associated error transform, the proposed controller can guarantee both the transient and steady-state suspension responses. The stability of the closed-loop system and the suspension performance requirements are rigorously proved. Finally, comparative simulations are conducted to validate the improved performance and robustness of the proposed method.
In this article, we propose learning and control strategies for a semiactive suspension system in a full car using soft actor-critic (SAC) models on real roads, where many road profiles with various ...power of disturbance exist (e.g., speed bumps and general roads). Therefore, a technique that enables deep reinforcement learning to cover different domains with largely different reward functions is proposed. This concept was first realized in a simulation environment. Our proposed switching learning system continuously identifies two different road disturbance profiles in real time such that the appropriately designed SAC model can be learned and applied accordingly. The results of the proposed switching SAC algorithm were compared against those of advanced and conventional benchmark suspension systems. Based on the results, the proposed algorithm showed smaller root-mean-square values of the <inline-formula><tex-math notation="LaTeX">z</tex-math></inline-formula>-directional acceleration and pitch at the center of the body mass. Finally, we also presented our successfully implemented SAC training system in a real car on real roads. The trained SAC model outperforms conventional controllers reducing the <inline-formula><tex-math notation="LaTeX">z</tex-math></inline-formula>-directional acceleration and pitch, similar to the simulation results, which is highly related to the riding comfort and vehicle maneuverability.
In the traditional bearingless switched reluctance motor (BSRM) system, the electromagnetic coupling between the torque system and suspension system is unavoidable. In this Letter, the present BSRM ...has the advantages of electromagnetic decouple with independent torque-suspension magnetic circuit design. However, the further in-depth study shows that the BSRM has an obvious suspension force fluctuation according to its asymmetry structure. Thus, it is necessary to build an accurate suspension force mathematical model considering commutation ripple. In this frame, a magnetic field segmentation method is proposed and the accurate suspension force model is built with Maxwell stress method and its reliability and precision are verified, modified based on finite element analysis.
Biased magnetic flux produced by a permanent magnet can reduce the power consumption of the suspension system in bearingless motors or magnetic bearings. However, the ability to generate suspension ...biased magnetic flux with a single permanent magnet tends to be saturated with the increase of the magnetising width. In order to solve the above problem, an axially superposed permanent magnet biased bearingless motor, which consists of a 12/8 reluctance motor for producing torque and two permanent magnets for producing desired biased magnetic flux density is present. The structure and working principle are introduced, and the electromagnetic characteristics are analysed by finite element analysis. The results verify that the proposed bearingless motor has the excellent merits of weak coupling between the torque system and suspension force and satisfactory suspension performance. Furthermore, much more biased permanent magnets could also be used for the suspension system of ultra-high speed, high power and slender bearingless motors such as flywheel energy storage systems.
This paper reviews the shear rheology of suspensions of microscopic particles. The nature of interparticle forces determines the microstructure, and hence the deformation and flow behavior of ...suspensions. Consequently, suspensions were classified according to the resulting microstructure: hard-spheres, stabilized, or aggregated particles. This study begins with the most simple case: flowing suspensions of inert, rigid, monomodal spherical particles (called hard-spheres), at low shear rates. Even for inert particles, we reviewed the effect of several factors that produce deviations from this ideal case, namely: shear rate, particle shape, particle size distribution, and particle deformability. Then we moved to suspensions of colloidal particles, where interparticle forces play a significant role. First we studied the case of dispersed or stabilized suspensions (colloidal dispersions), where long range repulsive forces keep particles separated, leading to a crystalline order. Second we studied the more common case of aggregated or flocculated suspensions, where net attractive forces lead to the formation of fractal clusters. Above the gelation concentration (which depends on the magnitude of the attractive forces), clusters are interconnected into a network, forming a gel. We differentiate between weak and strong aggregation, which may lead to weak or strong gels, respectively. Finally, we reviewed the case of filler/matrix composite suspensions or gels, where rigid or viscoelastic particles (fillers) are dispersed in a continuous viscoelastic material (matrix), usually a gel. For each type of suspension, predictive curves of fundamental rheological properties (viscosity, yield stress, elastic and complex moduli) vs. particle volume fraction and shear rate were obtained from theoretical or empirical models and sound experimental data, covering ranges of practical interest.
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► We reviewed the shear rheology of suspensions of microscopic particles. ► We classified them as hard-sphere, stabilized, and aggregated suspensions. ► We also studied filler-matrix composite suspensions. ► We discussed the main rheological models of each type of suspension. ► For each case, we plotted predictive curves of fundamental rheological parameters.
► Solid–liquid suspensions in stirred tank are investigated by experiments and CFD. ► Both partial and complete suspension regimes are investigated. ► An original criterion to identify via CFD the ...unsuspended particles is proposed. ► For the first time, suspension curves are predicted via CFD.
Mixing of solid particles into liquids within contactors mechanically agitated by stirrers is a topic of primary importance for several industrial applications. A great research effort has been devoted to the assessment of the minimum impeller speed (
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) able to guarantee the suspension of all particles. Conversely, only little attention has been paid so far to the evaluation of the amount of solid particles that are suspended at impeller speeds lower than
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. In some cases the loss in available interfacial area between particles and liquid could be reasonably counterbalanced by a decreased mechanical power, making it of interest to evaluate the percentage of suspended solids at different impeller speeds <
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in order to quantify the possible economical advantage of adopting an incomplete suspension (filleting) regime inside the stirred tank. The present work deals with computational fluid dynamics simulations of dense solid–liquid partial suspensions in baffled stirred tanks and particularly focuses on the prediction of the amount of suspended particles at agitation speeds encompassing both the filleting and the complete suspension regime. An Eulerian–Eulerian Multi Fluid Model coupled with a standard
k–
ɛ turbulence model for the continuous (liquid) phase only was adopted for CFD simulations. Both the Sliding Grid (SG) and the Multiple Reference Frame (MRF) approaches were employed to simulate the impeller-tank relative rotation. Different turbulence corrections to the fluid-particle drag correlation were considered. Experimental evidence was used for validation purposes: data collected by using the Pressure Gauge Technique (PGT)
1 and snapshots of the simulated tank. Comparison between CFD predictions and all experimental data showed a satisfactory agreement; for large particle diameters the drag coefficient correlation due to Pinelli et al.
2 gave the best results. The influence of the impeller motion treatment was found to be negligible.
In this paper, an output feedback finite-time control method is investigated for stabilizing the perturbed vehicle active suspension system to improve the suspension performance. Since physical ...suspension systems always exist in the phenomenon of uncertainty or external disturbance, a novel disturbance compensator with finite-time convergence performance is proposed for efficiently compensating the unknown external disturbance. Moreover, the presented compensator is advantageous over the existing ones since it is continuous and can completely remove the matched disturbance. From the viewpoint of practical implementation, continuous control law will not lead to chattering, which is desirable for electrical and mechanical systems. For the nominal suspension system without disturbance, a homogeneous controller with a simple filter is constructed to achieve a finite-time convergence property, where the filter is applied to obtain the unknown velocity signal. Thus, the nominal controller combines a disturbance compensator into an overall continuous control law, which provides two independent parts with a separate design unit and a high flexibility for selecting the control gains. According to the geometric homogeneity and finite-time separation principle, it can be shown that the active suspension is finite-time stabilized. A designed example is given to illustrate the effectiveness of the presented controller for improving the vehicle ride performance.
Scalable and efficient expansion of cell cultures are an important need for pluripotent stem cell (PSC)-derived allogeneic cell therapies. The large-scale production of high-quality PSCs can be ...achieved by three-dimensional (3D) suspension culture, wherein PSCs are cultured as aggregates or spheroids. However, adoption of 3D PSC suspension culture in clinical workflows is limited by the lack of commercial options for PSC suspension culture media. To address this, we developed the new GMP manufactured Gibco™ Cell Therapy Systems (CTS) StemScale™ PSC Suspension Medium to support PSC-based clinical manufacturing workflows. CTS StemScale is xeno-free and enables single cells to self-aggregate into 3D spheroids for efficient cell expansion.
CTS StemScale supports both induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs), with cell line-dependent growth in the range of 5X – 10X expansion per passage. When cultured over multiple consecutive passages, these spheroids have been demonstrated to maintain pluripotency, genomic stability, and trilineage differentiation potential. This suspension culture approach enables easy scale-up in various cell culture vessel sizes, from small-scale (<100 mL) culture vessels to large-scale (>1L) culture systems inclusive of bioreactors. Notably, 450 million cells were expanded to 5 billion cells in 5 days by using this PSC culture medium to grow spheroids within a bioreactor. To better enable future scale-up or other downstream applications, we also cryopreserved these cells at high densities which would minimize the number of cryovials required to thaw. Cells thawed from these vials showed high viability and were able to form spheroids which were capable of expanding at normal rates. Ultimately, cells grown in CTS StemScale have the flexibility to differentiate as 3D spheroids, dissociate into single cells and be utilized in downstream applications, or be cryopreserved as single cells for future use.
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