Modeling and stability study of a Bell-bar
The Bell-bar is a mechanical device commonly found on the main rotor head of helicopters. Its purpose is to increase the aircraft stability by mean of a mechanical feedback. Its exact effect and way of operation is not obvious. The goal of this project is to study this mechanism by modelling its dynamics and to study it’s stabilisation effect through Lyapunov analysis. Secondly, a simplified approximate model will be developed to be included in a future complete simulator of a model helicopter.
Prerequisite: Interrest in nonlinear analysis and in modelling. MATLAB and/or Mathematiica.
Modeling and simulating a model helicopter
The aim of this project is to write down and implement a model for a small helicopter. In this simulation, head and tail rotors will be considered as simple rotating discs with forces and torques representing the swashplate (plateau cyclique) actions. If time permits, a realtime simulation with joystick control will be coded.
Prerequisite: Interrest in non-linear analysis and in modelling. MATLAB and/or Mathematiica (and C/C++).
Autumn 2009 projects
Control of an autonomous unicycle robot
The Laboratoire d’Automatique is developing an autonomous unicycle robot for educational purpose. The system is supposed to stay on vertical position on its single wheel and move along paths. Preliminary studies have been performed in previous projects both in simulation and on a first prototype.
The goal of this project is to improve the design for achieving full energetically autonomy and to implement a controller able to follow predefined paths.
Nonlinear controller for ball and plate system
This project is aimed at designing a control strategy for a ball and plate system. The system consists of a ball rolling on a plate actuated by pitch and yaw actuators. There are several possible actuator configurations for the plate, using either linear or rotary actuators. The plate could also be mounted at the end of a robotic arm. In all the cases, the resulting centrifugal forces, which represent the main nonlinearity, will be different. Linear models neglect this centrifugal term that is proportional to the square of the angular velocity. Controllers designed based on linear models are not valid for high angular velocities and for configurations where the centrifugal forces are not negligible.
The scope of the project is to model the system for a chosen configuration and design a nonlinear controller to bring the ball at the desired position from a given initial position.
Multivariable controller design for a dual-drive gantry system
A dual-drive gantry configuration is a mechanical solution which offers higher acceleration levels in positioning systems. In such systems, two parallel linear motors are derived with the same reference signal and their positions are controlled independently. However, because of the mechanical coupling between two drives, high performance can be achieved when two drives are perfectly synchronized. This can be achieved by a multivariable controller in which the off-diagonal controllers decouple the system outputs.
A solution to this problem based on the Causal Ordering Graph formalism is proposed in a PhD thesis in Laboratoire d’Electrotechnique et d’Electronique de Puissance de Lille (L2EP). The objective of this project is to propose another solution to this problem based on the identified nonparametric models of the multivariable system and design a multivariable decoupling controller using a new method developed in the Automatic Control Laboratory of EPFL.
The project is proposed in collaboration with the Swiss company, ETEL.
MER: Alireza Karimi
Type of project: Master
Student: Heloise Gremaud
Complete Analysis/Design/Implementation of a Test Suite for Indico Project
MER: Denis Gillet
Type of project: Master
Student: Jeremy Nguyen-Xuan
Robust controller design for an inverted pendulum
In this project, the robust control of an inverted pendulum is considered. This system is an unstable system which consists of a pivot point mounted on a cart that can be moved horizontally using a DC motor. The angle of the pivot is measured, and the goal is to maintain it in a vertical position. Different weights can be added in the top of the pivot to change the dynamics of the system.
Robust controllers are designed to stabilize and satisfy the performances for a set of models. This type of controllers can be applied to nonlinear systems linearized in different operating points, time-varying systems as well as systems with parametric uncertainty. An approach to robust control design is to cast the problem to a convex optimization problem which can be solved efficiently using the numerical methods.
The objective of this project is to design a robust controller which stabilizes all possible configurations of the unstable inverted pendulum and satisfies some robustness specifications (phase margin, modulus margin, gain margin etc) using a design method developed in LA. The method is based on open-loop shaping in the frequency domain using a set of non-parametric models that can deal with unstable systems.
First of all, the existing real time code in LabView should be adapted. Then, the analytical model of the system should be obtained from physical laws and linearized in the different operating points. Next, classical design methods will be used to design an initial controller. Then some nonparametric model of the system are identified in closed-loop operation. Finally, the proposed method will be used to design a controller and applied on the experimental setup.