Design of an adaptive state feedback controller for a magnetic levitation system

This paper presents designing an adaptive state feedback controller (ASFC) for a magnetic levitation system (MLS), which is an unstable system and has high nonlinearity and represents a challenging control problem. First, a nonadaptive state feedback controller (SFC) is designed by linearization about a selected equilibrium point and designing a SFC by pole-placement method to achieve maximum overshoot of 1.5% and settling time of 1s (5% criterion). When the operating point changes, the designed controller can no longer achieve the design specifications, since it is designed based on a linearization about a different operating point. This gives rise to utilizing the adaptive control scheme to parameterize the state feedback controller in terms of the operating point. The results of the simulation show that the operating point has significant effect on the performance of nonadaptive SFC, and this performance may degrade as the operating point deviates from the equilibrium point, while the ASFC achieves the required design specification for any operating point and outperforms the state feedback controller from this point of view

Design, Optimization, and Experimental Characterization of a Novel Magnetically Actuated Finger Micromanipulator

The ability of external magnetic fields to precisely control micromanipulator systems has received a great deal of attention from researchers in recent years due to its off-board power source. As these micromanipulators provide frictionless motion, and precise motion control, they have promising potential applications in many fields. Conversely, major drawbacks of electromagnetic micromanipulators, include a limited motion range compared to the micromanipulator volume, the inability to handle heavy payloads, and the need for a large drive unit compared to the size of the levitated object, and finally, a low ratio of the generated magnetic force to the micromanipulator weight. To overcome these limitations, we designed a novel electromagnetic finger micromanipulator that was adapted from the well-known spherical robot. The design and optimization procedures for building a three Degree of Freedoms (DOF) electromagnetic finger micromanipulator are firstly introduced. This finger micromanipulator has many potential applications, such as cell manipulation, and pick and place operations. The system consists of two main subsystems: a magnetic actuator, and an electromagnetic end-effector that is connected to the magnetic actuator by a needle. The magnetic actuator consists of four permanent magnets and four electromagnetic coils that work together to guide the micromanipulator finger in the xz plane. The electromagnetic end-effector consists of a rod shape permanent magnet that is aligned along the y axis and surrounded by an electromagnetic coil. The optimal configuration that maximizes the micromanipulator actuation force, and a closed form solution for micromanipulator magnetic actuation force are presented. The model is verified by measuring the interaction force between an electromagnet and a permanent magnet experimentally, and using Finite Element Methods (FEM) analysis. The results show an agreement between the model, the experiment, and the FEM results. The error difference between the FEM, experimental, and model data was 0.05 N. The micromanipulator can be remotely operated by transferring magnetic energy from outside, which means there is no mechanical contact between the actuator and the micromanipulator. Moreover, three control algorithms are designed in order to compute control input currents that are able to control the position of the end-effector in the x, y, and z axes. The proposed controllers are: PID controller, state-feedback controller, and adaptive controller. The experimental results show that the micromanipulator is able to track the desired trajectory with a steady-state error less than 10 µm for a payload free condition. Finally, the ability of the micromanipulator to pick-and-place unknown payloads is demonstrated. To achieve this objective, a robust model reference adaptive controller (MRAC) using the MIT rule for an adaptive mechanism to guide the micromanipulator in the workspace is implemented. The performance of the MRAC is compared with a standard PID controller and state-feedback controller. For the payload free condition, the experimental results show the ability of the micromanipulator to follow a desired motion trajectory in all control strategies with a root mean square error less than 0.2 mm. However, while there is payload variation, the PID controller response yields a non smooth motion with a large overshoot and undershoot. Similarly, the state-feedback controller suffers from variability of dynamics and disturbances due to the payload variation, which yields to non-smooth motion and large overshoot. The micromanipulator motion under the MRAC control scheme conversely follows the desired motion trajectory with the same accuracy. It is found that the micromanipulator can handle payloads up to 75 grams and it has a motion range of ∓ 15 mm in all axes

Control of a single-link flexible manipulator

RESUMEN: En aplicaciones de robótica es común utilizar elementos mecánicos y eslabones rígidos. Esto se realiza así especialmente porque simplifica enormemente el modelado matemático, así como la obtención de controladores dinámicos y cinemáticos. Todo esto conlleva el poder obtener manipuladores que permiten una elevada precisión en el movimiento y en el posicionamiento. Sin embargo, cada día es más frecuente que los robots interaccionen con los operadores humanos en diferentes tareas. Ejemplos de esto pueden encontrarse en las aplicaciones industriales donde los robots colaborativos tienen mucho éxito, pero también en aplicaciones médicas y de servicio a personas discapacitadas, donde un robot puede hacer tareas de atención que conlleven una interacción con la persona. Es en estos campos de interacción con las personas donde un robot que incorpore segmentos mecánicos flexibles, tales que el contacto con las personas sea totalmente inocuo, presenta un futuro de interés (además de las aplicaciones espaciales). En el presente trabajo se analizarán y diseñarán distintos controladores basados en redes neuronales, lógica difusa y control GPI con el objetivo de evaluar su funcionamiento en un sistema que incluya eslabones mecánicos flexibles.ABSTRACT: In robotics applications it is common to use mechanical elements and rigid links. This is done especially because it greatly simplifies mathematical modeling, as well as obtaining dynamic and kinematic controllers. All this leads to manipulators that allow high precision in movement and positioning. However, it is becoming increasingly common for robots to interact with human operators in different tasks. Examples of this can be found in industrial applications where collaborative robots are very successful, but also in medical and service applications for disabled people, where a robot can perform care tasks that involve interaction with the person. It is in these fields of interaction with people that a robot incorporating flexible mechanical segments, such that contact with people is completely harmless, presents a future of interest (in addition to space applications). In this work, different controllers based on neural networks, fuzzy logic and GPI control will be analyzed and designed in order to evaluate their performance in a system including flexible mechanical links.Grado en Ingeniería en Electrónica Industrial y Automátic