Lane R. Miller

An Adaptive Semiactive Control Algorithm for Magnetorheological Suspension Systems

In this paper, we will present a nonlinear-model-based adaptive semiactive control algorithm developed for magnetorheological (MR) suspension systems exposed to broadband nonstationary random vibration sources that are assumed to be unknown or not measurable. If there exist unknown and/or varying parameters of the dynamic system such as mass and stiffness, then the adaptive algorithm can include on-line system identification such as a recursive least-squares method. Based on a nonparametric MR damper model, the adaptive system stability is proved by converting the hysteresis inherent with MR dampers to a memoryless nonlinearity with sector conditions. The convergence of the adaptive system, however, is investigated through a linearization approach including further numerical illustration of specific cases. Finally the simulation results for a magnetorheological seat suspension system with the suggested adaptive control are presented. The results are compared with low-damping and high-damping cases, and such comparison further shows the effectiveness of the proposed nonlinear model-based adaptive control algorithm for damping tuning.

Tuning passive, semi-active, and fully active suspension systems

A quarter car model is used to investigate the tuning of the damping for passive, on/off semiactive, continuously variable semiactive, and fully active suspensions. For the semiactive and fully active suspensions, the control algorithms are limited to feedback schemes based on absolute and relative velocity measurements. Ride comfort, road holding, and suspension travel are investigated with random input velocity to simulate road roughness. The application of a disturbance force to the sprung mass is used to investigate body control.<<ETX>>

Modelling and Performance of an Experimental Active Vibration Isolator

The performance of an active vibration isolator consisting of a fluid mount and an electromagnetic actuator is discussed. The electromagnetic actuator augments the inertia effects of the fluid mount to reduce the dynamic stiffness of the mount at the vibrational disturbance frequencies of the engine. The active isolator is modeled using bond graphs. Dynamic stiffness, blocked force, and free displacement transfer functions are developed from the bond graph model to gain insight into the active mount’s performance. A mount effectiveness analysis shows that reducing the mount’s dynamic stiffness results in better dynamic isolation. Numerical simulations along with laboratory testing of the active isolator are used to evaluate the performance of the mount. A simple laboratory experiment shows that an active mount can be controlled to have a dynamic stiffness that is 100 times (40 dB) lower than a passive mount, without sacrificing static stiffness.

Multidimensional mount effectiveness for vibration isolation

A method is presented for predicting the performance of multiple mount passive isolation systems. Performance is expressed in terms of a mount effectiveness matrix which relates the structure vibration in an isolated system to the structure vibration in an unisolated, or hard mounted system. Frequency response functions of the engine, isolator, and structure are used to construct the effectiveness matrix at each frequency of interest. Effectiveness matrix expresions are derived for a mounting system connected at multiple points by massless isolators. Isolator design guidelines are developed for the single and multiple isolator mounting systems

Simulation Study of Adaptive Magneto-Rheological Seat Suspension

This paper describes the details of the simulation analysis of a nonlinear model-based adaptive suspension control system[1, 2]. The numerical aspect of the simulation study of a seat suspension with application of magneto-rheological dampers will be presented. Magneto-rheological (MR) dampers have strong nonlinearities such as bi-linearity, hysteresis, and saturation related to magnetism, which can be represented by appropriate mathematic functions, respectively. Thus the model-based adaptive algorithm becomes complicated because of involvement of MR damper models. One objective of this study is to investigate the effect of MR damper model simplifications on the adaptive suspension performance. Furthermore, simulation is also applied to do parametric study of adaptive algorithm parameters such as filtering and step size. The simulation results compare the proposed adaptive controller with passive dampers to validate not only its effectiveness but also obtain some guidance information for its experimental implementation.Copyright

Superharmonics-Free Adaptive Semiactive Magneto-Rheological Suspension

This paper focuses on laboratory implementation of a semiactive seat suspension with application of magneto-rheological (MR) dampers. We firstly introduce the nonlinear dynamics phenomena induced with the skyhook control that is now widely applied from structural vibration suppression to commercialized vehicle suspensions. However, superharmonic dynamics has not been clearly addressed in such vibration control systems. This paper tries to explain how superharmonics are created with skyhook controls through testing data analysis. Furthermore, in order to avoid this dynamics issue, this study implements a nonlinear model-based adaptive control into this MR damper based seat suspension. Based on a nonparametric MR damper model, the adaptive algorithm is expanded mathematically, and the system stability is discussed. Then in the following sections, this paper describes implementation procedures such as modeling simplification and validation, and testing results. Through the laboratory testing, the adaptive suspension is compared to two passive suspensions: hard-damping (stiff) suspension with max current of 1A to the MR damper, and low-damping (soft) suspension with minimum of 0A, while broadband random excitations are applied with respect to the seat suspension resonant frequency in order to test the adaptability of the adaptive control. Furthermore, mass and spring rate are assumed known and unknown for this adaptive controller to investigate the capability of this algorithm with the simplified model, respectively. Finally the comparison of testing results is presented to show the effectiveness and feasibility of the proposed adaptive algorithm to eliminate the superharmonics from the MR seat suspension.Copyright

Commercial active noise control solutions for aircraft—A variety of approaches

Today’s aerospace market is placing increasing emphasis on reducing noise and vibration to enhance passenger comfort. Lord offers high‐performance active solutions for aircraft noise problems with its NVX active systems. There are currently over 50 Lord NVXTM Active Systems flying on a variety of aircraft around the world. These systems include active isolations sytems for the Cessna Citation X business jet, a pylon active structural control system for DC9 aircraft, and speaker‐based active noise control systems for corporate turboprops. While the systems share many commonalties, they represent a variety of different approaches to the individual noise problems of these aircraft. Each of these problems requires a solution optimally designed for the application. During the presentation, the system components and general operation will be discussed. The benefits and limitations of these approaches will also be covered. How each system was optimized for its specific application will also be discussed. Numerou...