Active Oscillation Damping Research Articles

Active damping of automotive powertrain oscillations by a partial torque compensator

This paper deals with the problem of active damping of driveline oscillations in order to improve driveability and passenger comfort. Specifically, longitudinal vibrations which occur during transient changes in driver demand may affect driveability in a negative way. A robust and efficient controller is proposed, driving the engine in order to actively damp the driveline oscillations. The methodology considered is based on the prediction and compensation of the shaft torque at relevant frequencies. Contrary to previous work, it leads to a controller having only a few tuning parameters, with a clear meaning and can be adjusted directly on the vehicle. The whole design is described, including robustness analysis ( μ analysis), backlash sensitivity, and discretization in a way that is compatible with the engine controller unit that works at a varying sampling rate. Finally, the results obtained with two different test cars are shown. They illustrate the efficiency of the proposed approach that allows reducing significantly the development time.

AN ENERGETIC COMPARISON BETWEEN VALVELESS AND VALVE CONTROLLED ACTIVE VIBRATION DAMPING FOR OFF-ROAD VEHICLES

This paper presents a comparison of the energetic consumption of a valveless and a valve controlled active oscillation damping system for off-road machinery. Today only passive oscillation damping systems are subject to off-road machine series production. These systems offer the advantage of no additional primary energy use for damping. However, the disadvantages are the high costs and no adaptation possibility to the operating parameters. The recent developments where valve controlled linear actuators have been used for active damping had to face several problems with too low dynamics of today’s implemented control valves and the high additional energy need. These disadvantages can be avoided by using valveless linear actuators for working functions and for active damping. In fact, throttling losses are omitted and, energy recovery is possible. It will be shown based on measurement and simulation results that a suitable damping quality can be achieved with valveless linear actuators. Therefore, some aspects of the controller design will be given. Hereby, a simple acceleration sensor and standard control hardware are used. The main part will describe the energetic modelling, whereby especially precise pump loss models have been developed. The energy consumption of both systems performing active damping is compared in detail.

An Overview about Active Oscillation Damping of Mobile Machine Structure

One main current demand for mobile machinery development is the improvement of operator comfort and productivity in order to be competitive on the global market in the future. Actual trends towards cost effective actuator systems in offroad vehicles and thereby the use of electrohydraulic actuators reflects also the task of active oscillation damping of the machine structure. In the past several concepts, which differ in hydraulic system, control and sensor strategy, have been developed. However, the practical use is still minor as in most cases passive oscillation systems, which base upon high pressure hydro-pneumatic accumulators, are widely used although the component costs and frequent check intervals are problematic for this technology. This paper presents an overview of research work done in the area of active oscillation damping technologies for offroad vehicles.

An H-infinity-based control design methodology dedicated to the active control of vehicle longitudinal oscillations

This paper deals with the problem of active damping of vehicle oscillations. A complete methodology based on an H/spl infin/ optimization is presented. Several dedicated analysis tools are used in order to analyze the behavior of the closed-loop system. Two tuning parameters allow the design of a controller managing the compromise between performance (in terms of oscillation attenuation and limit cycles) and robustness. Finally, a feedforward component is designed in order to improve the performance without changing the robustness properties or the controller complexity. Simulation results obtained with an experimentally validated model show the efficiency of the resulting controller.

Active damping of capillary oscillations on liquid columns

Active control of acoustic radiation pressure and of electrostatic stresses on liquid columns has been demonstrated to overcome the Rayleigh–Plateau instability that normally causes long liquid columns to break [M. J. Marr-Lyon et al., J. Fluid Mech. 351, 345 (1997); Phys. Fluids 12, 986–995 (2000)]. Though originally demonstrated for liquid–liquid systems in plateau tanks, the electrostatic method also works on columns in air in reduced gravity [D. B. Thiessen, M. J. Marr-Lyon, and P. L. Marston, ‘‘Active electrostatic stabilization of liquid bridges in low gravity,’’ J. Fluid Mech. (in press)]. In new research, the electrostatic stresses are applied in proportion to the velocity of the surface of the column so as to actively dampen capillary oscillations of the surface. The mode amplitude is optically sensed and the rate-of-change is electronically determined. Plateau tank measurements and theory both show that the change in damping rate is proportional to the feedback gain. The results suggest that either active control of electrostatic stresses or of acoustic radiation stresses can be used to suppress the response of interfaces to vibration. [Work supported by NASA.]

TRAJECTORY CONTROL OF CRANE LOAD POSITION AND INCLINATION

A gain-scheduled trajectory control is exemplary presented for two of six available axes of an overhead crane that allows for positioning and inclining the crane load according to specified trajectories. Besides its tracking capabilities, the proposed control provides an active oscillation damping. The overall control structure consists of independent axis controllers, which are adapted to measurements of varying system parameters. These axis controllers take advantage of combined feedforward and feedback control as well as observer based disturbance rejection. The achieved control performance is shown by selected experimental results from an implementation on a 5 t - bridge crane.

Control of switched reluctance drives for electric vehicle applications

Dynamic controllers of switched reluctance drives adjust at least three variables, i.e., current amplitude, turn-on, and turn-off angles. In electric vehicle (EV) applications high efficiency of the drive over a wide speed range, wide torque bandwidth, and low torque ripple under varying DC-bus voltage conditions are important design goals. Hence, controllers of switched reluctance drives for EVs usually have a complex structure. In this paper, the demands on control accuracy of switched reluctance machine traction drives and the traction controller sampling frequency, which are necessary to take advantage of the switched reluctance machine dynamic capabilities, are discussed. To integrate the traction drive, the control commands need to be actualized with a sampling frequency of at least 100 Hz to meet the high-dynamic requirements of modern vehicle control systems, e.g., active cruise control, antislip control, and active damping of mechanical drivetrain oscillations. It is found that the switching angles have to be adjusted within one-tenth of a mechanical degree. This study shows that switched reluctance drives can fulfill all requirements needed for electric propulsion using standard microcontrollers or digital signal processors.

MECHATRONICAL DESIGNED CONTROL OF FIRE-RESCUE TURNTABLE-LADDERS AS FLEXIBLE LINK ROBOTS

Turntable ladders with a maximum ladder length of up to 30 m can be assumed as 3-axes flexible link robots. For operation at maximum velocity which is an important factor for turntable ladders as fire rescue vehicles, and to realize an automated teach-in operation mode, a trajectory tracking control based on a decentralized control approach has been developed by a mechatronical design. The implementation guarantees active oscillation damping of all ladder movements. The recently presented active control system will be in future a standard equipment for the new generation of fire turntable ladders of the cooperation partner IVECO Magirus company.

Input filter stability of drives fed from voltage inverters controlled by direct flux and torque control methods

Problems of stability of input filters of drives controlled by direct torque and flux control methods are studied. Two direct methods for AC drive control, Depenbrock's (DSC) and Takahashi's, are based on two-level hysteresis control of torque and flux. The objective of the paper is to show that in the case of inverter drives controlled by these methods and fed from a DC source through an LC input filter instabilities of this filter can often occur. The case is different from studies published by Lipo and Krause (1969) and Ahmed et al. (1986) as it includes closed loops for torque and flux control. These fast nonlinear control loops mean that during input filter voltage and current oscillations the main state variables (flux and torque) do not oscillate. The basic difficulty in the analysis of stability of multidimensional variable-structure systems is the complexity of available methods. In the paper a state-averaging model of a drive controlled by two-level hysteresis controllers is proposed. Application of this model significantly simplifies the stability analysis. The analysis has been done by plotting the migration of eigenvalues of the linearised state matrix. A new strategy of active damping of input filter oscillations is proposed and its influence on the drive behaviour during transients is shown. Theoretical considerations are supported by results of simulation of the 2.6 MW inverter-fed drive.