Cycle‐by‐Cycle Adaptive Force Compensation for the Soft‐Landing Control of an Electro‐Mechanical Engine Valve Actuator

Electro‐mechanical valve actuators (EMVA) are a solution for implementing variable valve actuation in internal combustion engines. Their use can increase engine power, reduce fuel consumption and pollutant emissions, while significantly improving engine efficiency. The control of this actuator is a complex task since non‐smooth nonlinearities, parameter variations and external forces strongly affect plant dynamics. In addition, the impact of the valve at its end‐strokes translates into mechanical wear and unacceptable noise, and in the worst case the electromagnet may also fail to catch the valve, causing system failure. The design of effective control strategies to ensure valve capture with low impact velocities is therefore essential for the correct functioning of such a mechatronic device. In this paper, the control problem of reducing the impact velocity at “landing” known in the literature as soft landing control, is tackled via novel cycle‐by‐cycle adaptive force compensation control algorithms. Two schemes are presented: a discrete adaptive proportional integral controller to regulate landing velocity to a preassigned set‐point, and a gradient descent method based controller to automatically achieve the minimum admissible impact velocity. The effectiveness of both methods in limiting landing velocities is shown numerically using a high predictive simulator of the EMVA system, when considering unknown varying environmental conditions, such as internal friction and external gas pressure forces.     

Corrosion Resistance of 2014 Aluminium Matrix Composites Reinforced with Atomised Ni3Al

The corrosion resistance of 2014 aluminium matrix composites has been evaluated. The base alloy was manufactured through mechanical alloying, and reinforced with Ni₃Al (manufactured through atomisation). Composite materials were manufactured according to the following procedure: mixing, cold uniaxial compacting, and hot extrusion. All materials were tested as extruded and heat treated (T6 condition). Corrosion tests were carried out following ASTM standard methods G69 (measurement of corrosion potentials) and G110 (evaluation of intergranular corrosion). The influence that the intermetallic and T6 heat treatment have on the corrosion resistance of 2014 aluminium alloy has been studied. Results show that atomised Ni₃Al improves the intergranular corrosion resistance of base aluminium by a mechanism of cathodic protection. T6 heat treatment is also favourable.     

Structure and properties of polypropylene/hydrotalcite nanocomposites

This article presents the study of the modification of the particle/matrix interface region and its effects on the structure and dynamic mechanical behavior of polypropylene (PP)/hydrotalcite nanocomposites prepared by melt extrusion. The interface modification was promoted by combinying the organophillization of the hydrotalcite particles with blending the PP with a maleic anhydride‐grafted‐PP (PP‐g‐MAH) or a maleic anhydride‐grafted‐poly(styrene‐co‐ethylenebutylene‐co‐styrene) (SEBS‐g‐MAH). Sodium dodecyl sulphate was used to promote the organophillization of the hydrotalcite particles. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) showed a partially exfoliated hydrotalcite structure, with an increasing exfoliation being achieved by adding a compatibilizer and organo‐modifying the particles. Values of the Young's modulus (E), storage modulus (E′), maximum tensile strength (σ_max), neck propagation strength (σ_neck), and elongation at break (ε_b) were found to depend both on the nature of the particle matrix interface as well as on the type of compatibilizer. Also, nanocomposites prepared with the organophillized particles showed lower T_g and loss factor values. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers