Control of Automotive Semi-Active MR Suspensions for In-Wheel Electric Vehicles

In this work, four different semi-active controllers for a quarter of vehicle and full vehicles are evaluated and compared when used in internal combustion engine (ICE) vehicles vs electric vehicles (EVs) with in-wheel motor configuration as a way to explore the use of semi-active suspension systems in this kind of EVs. First, the quarter of vehicle vertical dynamics is analyzed and then a full vehicle approach explores the effectiveness of the control strategies and the effects of the traction in the vertical Control performances. Aspects like the relation between traction and suspension performances, and the resonance frequencies are also discussed.

On the Progressive VZN Shock Absorber Performances and Dissipated Energy

The VZN shock absorber concept granted with European Patent EP 1 190 184 is characterized by damping coefficients self according with road and load conditions.The simulations made on vehicles equipped with new VZN shock absorbers concept relative to standard one, indicates better behavior concerning stability, comfort and reduced dissipated energy, with fuel consumption and pollution reducing effect.Starting on these remarks the paper evaluates the influence of the damping characteristic in suspension performances and dissipated energy, based a simulation on a Californian road realized with Matlab Simulink software.Since year 2006 simulations on model ¼ cars demonstrates the VZN damper concept give skyhook behavior, decrease squat, vertical acceleration, the number and intensity of stopper bumper collision, the adherence, increasing thus the vehicle stability, comfort and reliability.Tests on models ½ car, show the VZN concept increases stability at pitch and roll and confirm the previous results obtained on ¼ models.The current work completed previous research with one demonstrating other VZN qualities e.g. its capacity to manage damping coefficient, no more and no less, assuring high performances and thus reducing the dissipated energy, with favorable effect for reducing fuel consumption and pollution.The comparison between the behaviors of the VZN shock absorber relative to the standard shock absorber has been realized for body displacement, squat, acceleration and dissipated energy.The VZN progressive damper concept gives better behavior comparative to standard one, 6% at car body bounce, 37 % for RMS acceleration and 28.4 % for dissipated energy, these means it confer better body-ground clearance, comfort and fuel consumption and pollution.The VZN damping coefficients accorded with the vehicles load and with road unevenness confer a soft response at low excitation and strong reactions at high excitations, dissipating energy function of the needs, assuring thus comfort at small and medium excitation and protecting the axles and body at hard conditions.

Mixed Sky-Hook and ADD: Approaching the Filtering Limits of a Semi-Active Suspension

The problem considered in this paper is the design and analysis of control strategies for semiactive suspensions in road vehicles. The most commonly used control algorithm is the well-known sky-hook (SH) damping. Recently, a new control approach named acceleration driven damping (ADD) has been developed, using optimal-control theory. It has been shown that SH and ADD have complementary characteristics: SH provides large benefits around the body resonance; otherwise performs similarly to a passive suspension; instead, ADD provides large benefits beyond the body resonance. The first goal of this paper is to show that—in their specific frequency domains—SH and ADD provide quasi-optimal performances, namely, that it is impossible to achieve (with the same semi-active shock-absorber) better performances. This result has been obtained using the framework of the optimal predictive control, assuming full knowledge of the disturbance. This result is very interesting since it provides a lower-bound to semi-active suspension performances. The second goal of the paper is to develop a control algorithm which is able to mix the SH and ADD performances. This algorithm is surprisingly simple and provides quasi-optimal performances.