Lars Christian Henriksen

Nonlinear Model Predictive Control of a Simplified Wind Turbine

Abstract This paper discusses the implications of formulating a single control law governing the entire wind speed range of operation for a wind turbine. Furthermore, the knowledge of future wind speeds provided by e.g. LIDARs is included in the controller framework. This is possible as the presented controller is based on nonlinear model predictive control and includes the knowledge of the future wind speed in the prediction horizon of the controller. The potential benefits of exploiting the knowledge provided by LIDARs is demonstrated in simulations with a simplified 1 degree-of-freedom nonlinear wind turbine model.

Visual Positioning and Docking of Non-holonomic Vehicles

The paper describes the benefits and drawbacks of different strategies for docking and positioning of autonomous vehicles based on visual feedback. Three algorithms are described in detail, and extensive experiments with an implementation of the algorithms on our test-bed Autonomous Guided Vehicle are documented.

Effects of gain-scheduling methods in a classical wind turbine controller on wind turbine aero-servo-elastic modes and loads

aeroservoelastic modes and loads DTU Orbit (03/11/2019) Effects of gain-scheduling methods in a classical wind turbine controller on wind turbine aeroservoelastic modes and loads The eects of dierent gain-scheduling methods for a classical wind turbine controller, operating in full load region, on the wind turbine aeroservoelastic modes and loads are investigated in this work. The dierent techniques are derived looking at the physical problem to take into account the changes in the aerodynamic characteristics as a function of the wind speed. The modal analysis is performed with a high-order linear aeroservoelastic model computed with the frequency based stability tool HAWCStab2. The time series of the wind turbines loads are computed with the non-linear time domain tool HAWC2. Results show changes in the natural frequency and in the damping ratio of the speed regulator mode and of the tower longitudinal mode when using the dierent gain-scheduling schemes.

Constraint handling within a multi-blade coordinate framework of a wind turbine

In this paper the control of a horizontal axis pitch controlled wind turbine using Model Predictive Control is presented. The multi-blade coordinate transformation is utilized to turn the rotating frame time-varying system description into a time-invariant fixed frame system description. Constraints in the rotating frame of reference are not easily described in the fixed frame and a Model Predictive Control formulation accommodating this problem is presented. The presented method is tested with satisfactory results in a numerical simulation.

Optimal tuning for a classical wind turbine controller

Fine tuning of controllers for pitch-torque regulated wind turbines is an opportunity to improve the wind turbine performances and reduce the cost of energy without applying any changes to the design. For this purpose, a method for automatically tune a classical controller based on numerical optimization is developed and tested. To have a better understanding of the problem a parametric analysis of the wind turbine performances due to changes in the controller parameters is first performed. Thereafter results obtained with the automatic tuning show that is possible to identify a finer controller tuning that improves the wind turbine performances. For the case study selected in this work, a 2% cost function reduction is achieved with seven iterations.

Design of Navigation and Control for an AGV

Abstract The paper describes the design of the methods for relative position and orientation estimation for AGV’s using monocular vision and guidemarks. An analysis of the performance and accuracy is presented. A simulation environment developed to make testing of new algorithms easier is presented. The environment is written in MATLAB and uses the MATLAB GUI. Simulated results as well as results from real experiments is presented and compared guidemarksA local navigation algorithm for docking a stationary recharging station and driving through an open door is evaluated and from accuracy requirements for docking an improved beacon navigation algorithm is found. Results from real experiments are presented.

Diagnosis of wind turbine rotor system

This paper describes a model free method for monitoring and fault diagnosis of the elements in a rotor system for a wind turbine. The diagnosis as well as the monitoring is done without using any model of the wind turbine and the applied controller or a description of the wind profile. The method is based on available standard sensors on wind turbines. The method can be used both on-line as well as off-line. Faults or changes in the rotor system will result in asymmetries, which can be monitored and diagnosed. This can be done by using the multi-blade coordinate transformation. Changes in the rotor system that can be diagnosed and monitored are: actuator faults, sensor faults and internal blade changes as e.g. change in mass of a blade.

Monitoring of a Wind Turbine Rotor using a Multi-blade Coordinate Framework*

Abstract In this paper a method to detect asymmetric faults in a wind turbine rotor is presented. The paper describes how fault diagnosis using an observer-based residual generator approach is able to distinguish between the nominal and faulty case by the injection of e.g. a sinusoidal excitation signal into the system. In the case of a wind turbine, an excitation signal is automatically generated by the rotation of the rotor in a turbulent wind field. Using the multi-blade coordinate transformation, the detection of asymmetries in the rotor of the wind turbine is greatly improved.

Autonomous Vehicle Interaction with In-door Environments

The paper describes the possibilities of enhancing the performance of autonomous vehicles by interacting with the surrounding environment. Benefits and drawbacks of the use of different sensors and strategies for integrating the acquired knowledge are examined in an example case of a ‘through partly closed door’ navigation task for an AGV. This illustrates the increased ability of sensors to acquire knowledge by actively doing explorative actions. A combined mechanical actuation and probing device accentuates the sense-act paradigm.