Tristan Braun

New results for position estimation in electro-magnetic actuators using a modified discrete time class A/B model reference approach

In this paper, a number of new results are presented that have been achieved with a previously suggested approach for estimating the armature position of electro-magnetic actuators. With the assumption that only current and voltage measurements are available, a discrete time model reference adaptive system (MRAS) is used. It is shown that by identification of the parameters of the electrical subsystem, an accurate estimate for the armature position can be obtained. A combination of two discrete time MRAS methods is proposed in order to take advantage of their complementary properties. It is shown in practical experiments that with this approach robust and fast estimation of the electrical parameters is achieved and the position estimation can thus be solved in real world applications. Moreover, the dependencies of the electrical parameters on the magnetic hysteresis are shown.

Position estimation in electro-magnetic actuators using a modified discrete time class A/B model reference approach

In this paper, the use of a discrete time model reference adaptive approach is proposed for estimating the armature position of electro-magnetic actuators. It is assumed that current and voltage measurements are available, only. It is shown that by identification of the parameters of the electrical subsystem, a unique and accurate estimate for the armature position can be obtained. To this end two discrete time MRAS methods are combined in order to take advantage of complementary properties. It is shown in practical experiments that with this approach robust and fast estimation of the electrical parameters is achieved and the position estimation can thus be solved in real world environments.

State estimation for fast-switching solenoid valves — A Nonlinear sliding-mode-observer approach

This paper studies state estimation for a dual coil solenoid valve, based on a nonlinear Sliding-Mode-Observer (NLSMO). A simple model of the solenoid is presented that might be applied for different types of electromagnetic actuators. Solely current and voltage measurement is used to observe the position trajectory of the moving armature. By simulation, it is shown that the states can be reconstructed even under parameter and modeling uncertainties. Experimental results on a lab test rig validate the robust behavior of the proposed observer, and are thoroughly discussed.

A distributed parameter approach for dual solenoid valve control with experimental validation

This paper studies the problem of computing feedforward control input signals for a solenoid actuator based on a distributed parameter model. The solution is expressed as a power series, and a backward/forward procedure is suggested to verify the approach and to investigate the effect of simplifications. Experimental results from a lab test rig are provided to show that this approach can provide feed-forward control signals which are able to steer the system along the desired trajectory.

Sliding Mode Observation with Iterative Parameter Adaption for Fast-Switching Solenoid Valves

Control of the armature motion of fast-switching solenoid valves is highly desired to reduce noise emission and wear of material. For feedback control, information of the current position and velocity of the armature are necessary. In mass production applications, however, position sensors are unavailable due to cost and fabrication reasons. Thus, position estimation by measuring merely electrical quantities is a key enabler for advanced control, and, hence, for efficient and robust operation of digital valves in advanced hydraulic applications. The work presented here addresses the problem of state estimation, i.e., position and velocity of the armature, by sole use of electrical measurements. The considered devices typically exhibit nonlinear and very fast dynamics, which makes observer design a challenging task. In view of the presence of parameter uncertainty and possible modeling inaccuracy, the robustness properties of sliding mode observation techniques are deployed here. The focus is on error convergence in the presence of several sources for modeling uncertainty and inaccuracy. Furthermore, the cyclic operation of switching solenoids is exploited to iteratively correct a critical parameter by taking into account the norm of the observation error of past switching cycles of the process. A thorough discussion on real-world experimental results highlights the usefulness of the proposed state observation approach.

State estimation for fast-switching solenoid valves: A study on practical nonlinear observers and new experimental results

Knowing the position of the spool in a solenoid valve, without using costly position sensors, is of considerable interest in a lot of industrial applications. In this paper, the problem of position estimation based on state observers for fast-switching solenoids, with sole use of simple voltage and current measurements, is investigated. Due to the short spool traveling time in fast-switching valves, convergence of the observer errors has to be achieved very fast. Moreover, the observer has to be robust against modeling uncertainties and parameter variations. Therefore, different state observer approaches are investigated, and compared to each other regarding possible uncertainties. The investigation covers a High-Gain-Observer approach, a combined High-Gain Sliding-Mode-Observer approach, both based on extended linearization, and a nonlinear Sliding-Mode-Observer based on equivalent output injection. The results are discussed by means of numerical simulations for all approaches, and finally physical experiments on a valve-mock-up are thoroughly discussed for the nonlinear Sliding-Mode-Observer.

A semilinear distributed parameter approach for solenoid valve control including saturation effects

In this paper a semilinear parabolic PDE for the control of solenoid valves is presented. The distributed parameter model of the cylinder becomes nonlinear by the inclusion of saturation effects due to the materials B/H-curve. A flatness based solution of the semilinear PDE is shown as well as a convergence proof of its series solution. By numerical simulation results the adaptability of the approach is demonstrated, and differences between the linear and the nonlinear case are discussed. The major contribution of this paper is the inclusion of saturation effects into the magnetic field governing linear diffusion equation, and the development of a flatness based solution for the resulting semilinear PDE as an extension of previous works [1] and [2].

Sensorlose Positionsregelung eines hydraulischen Proportional-Wegeventils mittels Signalinjektion

Zusammenfassung Es wird eine Methode zur sensorlosen Positionsbestimmung bei elektromagnetisch betätigten Aktoren vorgestellt. Dabei werden basierend auf einer Signalinjektion die positionsabhängigen Parameter bei der injizierten Frequenz bestimmt und daraus über ein geeignetes Modell die Position des Magnetankers ermittelt. Die Eignung des Verfahrens zur sensorlosen Positionsregelung wird an einem bidirektionalen Proportionalventil anhand praktischer Versuche demonstriert.

Nonlinear Voltage Control for Motion State Detection in Solenoid Valves: A Lyapunov Approach

In this paper, a control strategy that enables a reliable dip detection for solenoid valves is presented. For this purpose, the power electronics components are temporarily switched into a linear mode, using a power MOSFET as a voltage controlled resistor. The voltage is stabilized via a nonlinear controller that has been designed using Lyapunovs direct method. The stability region is determined and theoretical investigations are conducted in order to find appropriate controller parameters. The usefulness of the method is demonstrated by several experiments deploying an FPGA based hardware platform.