Browse Topic: Active suspension systems
ABSTRACT Reconnaissance of distant targets with long reaching sensor technology demands a stable platform upon which to operate. Traditionally this requires vehicles deploying mast mounted sensors to remain stationary while collecting data. Pairing electronically controlled active Electromechanical Suspension System (EMS) technology developed by The University of Texas Center for Electromechanics (UT-CEM) with current reconnaissance vehicle platforms creates highly mobile intelligence gathering systems capable of operating on the move over rough and unimproved terrain. This report documents the establishment of criteria by which to judge sensor platform stabilizing performance of EMS and then uses these metrics to evaluate performance improvements over conventional passive vehicles. Based on this analysis it may be possible to operate effectively over cross-country terrains at speeds of 10 to 15 mph while collecting useful reconnaissance data
Abstract Active and semi-active suspension systems are mechatronic systems that require a disciplined approach to synergistically combine the traditional engineering fields of mechanical, electronic, controls, power, systems, automotive, and suspension. Integrating suspension design is particularly challenging because it strongly interfaces with safety issues and driver perceptions, which are not easily optimized. Since 1993, the University of Texas Center for Electromechanics (UT-CEM) has successfully developed high performance active suspension technology and systems for a wide range of military vehicles, including small tactical trucks (e.g., HMMWV), medium tactical trucks (e.g., LMTV), and hybrid electric tanks (e.g., BAE’s Lancer prototype). In addition to developing active suspension technology, UT-CEM has developed, refined, and validated an integrated simulation based design approach for controlled suspension systems that is the topic of this paper
Active suspensions can alter the dynamic behavior of a vehicle in real time to respond optimally to any given operating scenario. Today’s active suspension technologies such as hydraulics, rotary electromagnetics, and linear electromagnetics do offer performance gains but these gains are outweighed by important disadvantages including high power consumption, low quality of force, and high costs and weights. Controlled slippage magnetorheological (MR) actuators are an emerging alternative actuation technology that is light, compact, power dense, and produces a high-quality force, making it ideal for active suspension applications. This article conducts an in-depth experimental assessment of the potential of MR actuators to increase vehicle ride comfort quality when used as active suspensions. Four high power MR actuators are installed on a BMW 330Ci and tests are performed on a closed road. Results show that with an impedance controller, comfort is increased by 67% at 65 km/h and by 61
The objective of the present article is to design a nonlinear passive suspension system for an automobile subjected to random road excitation which generates a performance as close to a fully active suspension system as possible. Linear Quadratic Regulator (LQR) control is used to synthesize an active suspension system. The control forces corresponding to the nonlinear passive suspension and the active suspension are equated, and the parameters are optimized as the performance error between the two systems is reduced. The nonlinear equations of motion are reduced to equivalent linear equations, where the system states are a function of the vehicle response statistics, by using the equivalent linearization method. The performance of the optimized nonlinear model and the linear model are compared with the performance of the LQR control active suspension system. The nonlinear model performs better than the linear system with chosen parameters. The optimized system achieves almost an equal
The vehicle performance is examined based on its specific performance indices. These specific performance indices include stability, ride comfort, steering ability, etc. The vehicle ride comfort is an important factor of vehicle quality and receiving large attention. The majority of previous investigations are focused on vertical vibration analysis of the sprung mass of the vehicle subjected to vertical excitations from the road surface. This study evaluates the ride characteristics of a coupled vertical-lateral 13 degrees of freedom (DoF) full-car model of a light passenger four-wheel vehicle developed with the Lagrangian method. The random vertical and lateral undulations of the road surface have been accounted for in the analysis and represented by the Power Spectral Density (PSD) function. The vehicle ride is assessed based on the International Organization for Standardization (ISO) 2631-1 annexure and the vehicle overall ride index is determined. The vehicle’s vertical-lateral
Ride comfort assessment is undoubtedly related to the interaction between the vehicle tires and the road surface. Indeed, the road profile represents the typical input for tire vertical load estimation in durability analysis and for active/semi-active suspension controller design. However, the road profile evaluation through direct experimental measurements involves long test time and excessive cost required by professional instrumentations to detect the road irregularities with sufficient accuracy. An alternative is shifting attention towards efficient and robust algorithms for indirect road profile evaluation. The object of this work aims at providing road profile estimation starting from vehicle dynamics measurements, through accessible and traditional sensors, with the application of a linear Kalman filter algorithm. The filter is designed and tuned by considering the pitch/bounce half-car models for the prediction phase and by measuring vertical accelerations and angular speeds
The article examines quarter-car dynamics with the possible separation of its tire from the road. A set of nondimensionalized differential equations has been proposed to minimize the involved parameters. Time and frequency response investigation of the system has been analyzed insightfully considering tire-road separation. To measure the separation of the tire, a time fraction index is defined, indicating the fraction of separation time in a cycle at steady-state conditions. Minimizing the index is assumed as the objective of the optimized system. An actuator is applied to the vehicle suspension in parallel with the mainspring and damper of the suspension. Particle Swarm Optimization (PSO) is used to properly tune a Proportional-Integral-Derivative (PID) controller for the active suspension system excited by a harmonic excitation. To verify the effectiveness of the control proposed, the controlled result compared with a passive suspension system illustrates the design, achieving a more
1 Rear wheel drive vehicles have a long driveline using a propeller shaft with two universal joints. Consequently, in this design usage of universal joints within vehicle driveline is inevitable. However, the angularity of the driveshaft resulting from vertical oscillations of the rear axle causes many torsional and bending fluctuations of the driveline. Unfortunately, most of the previously published research work in this area assume the propeller inclination angle is constant under all operating conditions. As a matter of fact, this assumption is not accurate due to the vehicle body attitudes either in pitch or bounce motions. Where the vehicle vibration due to the suspension flexibility, either passive or active type, exists. Moreover, the relative motion between the body and the wheel make this virtualization is so far from the realty in real ground vehicles In this research work, the hydro-pneumatic limited bandwidth active suspension system with wheelbase preview control is
The main objective of this work is to enhance the occupant ride comfort. Ride comfort is quantified in terms of measuring distinct accelerations like sprung mass, seat and occupant head. For this theoretical evaluation, a 7- degrees of freedom (DOF) human-vehicle-road model was established and the system investigation was limited to vertical motion. Besides, this work also focused to guarantee other vehicle performance indices like suspension working space and tire deflection. A proportional-integral-derivative (PID) controller was introduced in the vehicle model and optimized with the aid of the genetic algorithm (GA). Actuator dynamics is incorporated into the system. The objective function for PID optimization was carried out using root mean square error (RMSE) concept. The severity of various suspension indices and biomechanics responses of the developed model under proposed approach were theoretically analyzed using various road profiles and compared with conventional passive
Advanced passenger vehicles are complex dynamic systems that are equipped with several actuators, possibly including differential braking, active steering, and semi-active or active suspensions. The simultaneous use of several actuators for integrated vehicle motion control has been a topic of great interest in literature. To facilitate this, a technique known as control allocation (CA) has been employed. CA is a technique that enables the coordination of various actuators of a system. One of the main challenges in the study of CA has been the representation of actuator dynamics in the optimal CA problem (OCAP). Using model predictive control allocation (MPCA), this problem has been addressed. Furthermore, the actual dynamics of actuators may vary over the lifespan of the system due to factors such as wear, lack of maintenance, etc. Therefore, it is further required to compensate for any mismatches between the actual actuator parameters and those used in the OCAP. This is done by
A hybrid fuzzy and proportional-integral-derivative (PID) controller is proposed for roll angle handling of a three-axle truck with an active air suspension system. The conventional truck suspension system has four air springs for the rear wheels and two leaf springs for the front wheels, which cannot properly control the pitch angle, and here in this study is upgraded into front air springs. Therefore in the full air suspension system, the pitch angle is controlled by the active suspension system. Roll reduction of a heavy vehicle can improve the ride comfort and rollover tendency of the truck, simultaneously. The relation of air spring pressures and vehicle dynamics is developed in a simple and accurate model. Using this comprehensive model, it is possible to control the variables of vehicle dynamics such as roll, pitch, and height of the truck. The truck air suspension system is examined in step steering, fishhook, and asymmetric rough road (types E and G power spectral density [PSD
The main aim of the current research work is to investigate the behavior of passenger and driver biomechanics when the vehicle is excited under road irregularities. For this purpose, a 14-degrees of freedom (DOF) human-vehicle-road model was proposed. In addition to that, the ride comfort of the occupant with the aid of active suspension and its influence on other performance indices like suspension working space and road holding were also investigated. Besides sprung mass acceleration, the ride comfort was evaluated with pitching acceleration and occupant’s head acceleration representation. Active suspension based on Proportional Integral Derivative (PID) controller with hydraulic actuator was implemented. Then, the parameters of the PID controller are optimally tuned by adopting genetic algorithm (GA) with the assist of integral time absolute error (ITAE) method. The objective function was obtained by combining the ITAE of tire deflection, suspension deflection and sprung mass motion
Sliding mode control with a disturbance observer (SMC-DO) is proposed for suppressing the sprung mass vibration in a quarter-car with double-wishbone active suspension system (ASS), which contains the geometry structure of the upper and lower control arms. The governing equations of double-wishbone ASS are obtained by the balance-force analysis of the sprung mass in ASS. Considering uncertainties in damping, stiffness, and external disturbance acting on the sprung mass, we design a disturbance observer based on a sliding mode control (SMC) to estimate these uncertainties under the unknown road excitation. By the Lyapunov minimax approach, the uniform boundedness and the uniform ultimate boundedness of ASS with the proposed control are rigorously proved. Through co-simulation of ADAMS software and MATLAB/Simulink software, the sprung mass acceleration of ASS can be obtained with and without the proposed control. The results show that ASS with the proposed control can yield better riding
This article presents a robustness analysis study for the model reference controller (“MRC”) of active suspension system. The MRC employs both suspension look-ahead preview and wheelbase preview concepts. The methodology of the MRC is based on the ideal hybrid skyhook-groundhook scheme. A 13 degree of freedom full vehicle model is developed and validated. The engine mass, driver seat, and anti-roll bar are considered in the model. The MRC strategy uses eight proportional-integral-derivative (PID) controllers for both body and wheel control. A gradient based on optimization algorithm is applied to obtain the controller parameters using a cost function including both ride comfort and road holding performance. The robustness analysis of the controller is performed by evaluating the MRC controller performance under different driving conditions, including different road profiles, different vehicle speeds, and different vehicle loading. Furthermore, the effect of the variable design
An effective damper is among the most important components of the suspension system. It ensures the right amount of damping force is acting on the suspension system to provide comfort to the passengers and proper road holding to tires. Unfortunately, the energy absorbed by the dampers from the suspension system gets wasted in the form of heat. In this article, it is proposed to use innovative electromagnetic damper (EMD) with a crank-lever mechanism to recover energy from the suspension system. The goal is to develop a lightweight design of EMD that can recover a high amount of power. For the design, an off-road vehicle is used since in off-road vehicles the amount of power wasted in the suspension system is high. Three different design approaches are used, which include single-stage gearbox type, two-stage gearbox type, and three-stage gearbox type of CLEMD. Out of them, the best design, i.e. three-stage gearbox type of CLEMD is selected because of minimum weight and inertia of the
This paper introduces an optimum design for a feedback controller of a fully active vehicle suspension system using the combined multi-objective particle swarm optimization (CMOPSO) in order to minimize the actuator power consumption while enhancing the ride comfort. The proposed CMOPSO algorithm aims to minimize both the vertical body acceleration and the actuator power consumption by searching about the optimum feedback controller gains. A mathematical model and the equations of motion of the quarter-car active suspension system are considered and simulated using Matlab/Simulink software. The proposed active suspension is compared with both active suspension system controlled using the linear quadratic regulator (LQR) and the passive suspension systems. Suspension performance is evaluated in time and frequency domains to verify the success of the proposed control technique. The simulated results reveal that the proposed controller using CMOPSO grants a significant enhancement of ride
The objective of this paper is to study the influence of a suspension system on the human body with the effect of the controller behavior. For this work, 2-Degree of Freedom (DoF) quarter car suspension system with 4 DoF seated human body is modeled. The mathematical equation is developed by using a lumped mass parameter method. Governing equations of motions are generated by Newton’s Law of motion. Random road profile is also considered for this study. MATLAB/SIMULINK software is used to simulate the system results and system analysis is limited to a Proportional Integral Derivative (PID) controller with hydraulic actuator. Seat to Head transmissibility ratio of the active suspension system is analyzed and compared with the passive suspension system. Finally, to illustrate the effectiveness of the proposed active system, simulated results are compared with ISO 2631 comfort curves. Therefore the result shows that the PID based active suspension system improves the ride comfort of the
Active suspension control for in-wheel switched reluctance motor (SRM) driven electric vehicle with dynamic vibration absorber (DVA) based on robust H∞ control method is presented. The mounting of the electric drives on the wheels, known as in-wheel motor (IWM), results in an increase in the unsprung mass of the vehicle and a significant drop in the suspension ride performance and road holding stability. Structures with suspended shaftless direct drive motors have the potential to improve the road holding capability and ride performance. The quarter car active suspension model equipped with in-wheel SRM is established, in which the SRM stator serves as a dynamic vibration absorber. The in-wheel SRM is modelled using an analytical Fourier fitting method. The SRM airgap eccentricity is influenced by the road excitation and becomes time-varying such that a residual unbalanced radial force is induced. This is one of the major causes of SRM vibration. Current chopping control (CCC) and
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