Aah Ad Damen

Model-Based Commutation of a Long-Stroke Magnetically Levitated Linear Actuator

This paper concerns a commutation and switching algorithm for multi-degree-of-freedom moving-magnet actuators with permanent magnets and integrated active magnetic bearing. Because of the integration of long-stroke actuation and an active magnetic bearing, DQ-decomposition cannot be applied. Therefore, these actuators are a special class of synchronous machines. A newly developed model-based commutation algorithm for linear and planar actuators enables long-stroke motion by switching between different sets of coils. Moreover, the ohmic losses in the coils are minimized. Three different versions of the algorithm are compared and successfully implemented on a 3-DOF magnetically levitated linear actuator

Control of multi-degree-of-freedom planar actuators

This paper concerns a control-oriented analysis of a new commutation strategy which overcomes the limitations of dq0-decomposition for ironless multi-DOF planar actuators with integrated magnetic bearings. The new strategy minimizes the losses and allows for smooth switching of active coils while maintaining the decoupling of all degrees of freedom. Moreover, the method can also include the edge effects of the magnet-array which is not possible with dq0-transformation. The proposed controller has been implemented on a 3-DOF actuator which elucidates the good performance. When adding constraints to the new algorithm, multi-phase behavior can be achieved, which is suitable for multi-phase amplifiers

Vibration isolation of an electromagnetic actuatorwith passive gravity compensation

A control strategy of combining H∞ control and feedback linearization was applied to the model of a highly nonlinear, three Degrees-Of-Freedom (DOF) electromagnetic actuator, which was recently designed for non-contact suspension of a large payload. The new electromagnetic actuator has the advantage of passive gravity compensation based on permanent magnets with low stiffness and high force density. But the nonlinearity is so high that the stability status along each DOF changes while the translator is traveling within the working range. Feedback linearization method was used to compensate the nonlinearity, a stabilizing controller was employed to eliminate the slow-varying calculation error of the passive force, and an H∞ controller was designed for vibration isolation. Simulation results show that the proposed control strategy has robust vibration isolation performance within a working range in which the relation between the magnetic force and the relative position is highly nonlinear.

Backstepping control for lateral guidance of all-wheel steered multiple articulated vehicles

This paper describes the design of a backstepping controller for lateral guidance of all-wheel steered, multiple articulated vehicles. The design of the controller is based on a nonlinear dynamic vehicle model that describes all the degrees of freedom of the vehicle in the horizontal plane. The lateral and yaw dynamics are extracted from this model in order to design the controller. Simulation results are shown for a double articulated vehicle entering curves with different radii and at different speeds and for a double articulate vehicle subjected to a disturbance force due to wind. For these simulations, it was assumed that all vehicle parameters were known exactly.

Modeling and control of a 6-DOF contactless electromagnetic suspension system with passive gravity compensation

A contactless Electro-Magnetic Isolator (EMI) is designed for gravity compensation of a heavy payload by passive Permanent Magnetic (PM) force and control by active Lorentz force. The theoretically calculated PM force and torque produced by this EMI are presented. To characterize the EMI and to evaluate the vibration isolation performance, the Single EMI System (SEMIS) is designed by adding three horizontal and three vertical Lorentz actuators for control. It is a six Degrees-of-Freedom (DOF) contactless electromagnetic suspension system possessing the properties of inherent instability, nonlinearity, no mechanical contact, passive gravity compensation. The physical SEMIS model is developed based on reasonable assumptions and approximations. It is subsequently linearized for control design. The vibration isolation performance of the two control strategies, decoupled control and decentralized control, are simulated and compared. The results show that decentralized control has more significant coupling than the decoupled control for only two DOF-pairs.

Stabilization and vibration isolation of a contactless Electromagnetic Isolator: A Frequency-Shaped Sliding Surface Control approach

A Frequency-Shaped Sliding Surface Control (FSSSC) approach is applied to an unstable model of a candidate Electro-Magnetic Isolator (EMI) design which has three Degrees Of Freedom (DOF). The EMI is designed to achieve contactless passive gravity compensation for heavy load by permanent magnets. The 3-DOF model can be regarded as three exactly the same double-integrators disturbed by the nonlinear and coupled passive force which results in its inherent instability. The sliding surface is designed based on relative displacement and payload acceleration feedback to achieve low-frequency vibration isolation. To avoid the algebraic control loop, a linear converging controller is designed instead of the conventional switching control. Regardless of the plant uncertainties, the closed-loop transmissibility converges to the designed transmissibility with increasing open-loop gain. A sufficient condition for the closed-loop stability is developed. Both time domain and frequency domain performance of the designed controller is evaluated by simulation. It shows that robust vibration isolation performance is achieved despite of the nonlinear and coupled passive force.

Robust vibration isolation by Frequency-Shaped Sliding Surface Control with geophone dynamics

The Frequency-Shaped Sliding Surface Control (FSSSC) has been recently applied to the Active Vibration Isolation System (AVIS) and the robust skyhook performance is experimentally validated. However, the performance of this approach is theoretically limited by the sensor dynamics. This paper generalizes the FSSSC approach as a two-step AVIS control design method. The first step is to design the sliding surface which determines the designed performances. The second step is to design the regulator which guarantees the convergence of the system dynamics. As long as this convergence is guaranteed, the designed performances would be realized. The vibration isolation of the original plant is therefore transformed to the regulation of a new system which is composed of the original plant and the sliding surface. As the regulator design has been well studied in the literature, this paper focuses on the sliding surface design. An example sliding surface design to achieve low-frequency vibration isolation is provided. The FSSSC of an example 1-DOF plant using both original and the improved sliding surface are compared. Theoretical calculations show that the improved sliding surface has no theoretical performance limit and achieves robust vibration isolation at much lower frequencies than the original design.

On-line identification of vehicle fuel consumption for energy and emission management: An LTP system analysis

An Energy Management (EM) system traditionally relies on (quasi) static maps offering efficiency parameters of the vehicle powertrain. During a vehicles life span, these maps lose validity, so optimal performance for EM is not assured. This paper presents a proof-of-concept for a novel measurement system, estimating important engine and generator characteristics on-line during driving. The generator applies a small excitation signal to the combustion engine and by means of correlation techniques and feedback control, the incremental fuel cost for generating electric power is estimated. This information is very relevant for EM in Hybrid Electric Vehicles. No additional sensors (e.g. torque estimators) are needed. Under mild assumptions it is shown that the measurement system satisfies a Linear Time Periodic (LTP) System. Harmonic analysis as well as Floquet Theory are used to analyze performance and stability criteria. Simulation results support this analysis and demonstrate good noise rejection of the system.

Modeling and Identification of a 3-DOF Planar Actuator with Manipulator

The goal of this paper is to describe the identification and modeling of a 3-degree-of-freedom (DOF) platform with a manipulator on top of it, which is magnetically levitated by 9 voice-coil actuators. This 3-DOF experimental setup is a pre-prototype of a 6-DOF magnetically levitated platform with manipulator in order to study combined control of both the platform and manipulator.

Average H2 control by randomized algorithms

In this paper the problem of average H 2 control design will be studied. It is well known that this problem in its general form cannot be solved analytically or even numerically in an efficient way. We will employ so called randomized algorithms in order to solve the controller synthesis problem. The method of controller design wil be llustrated in an example of an active suspension system.