Francisco J. Ruiz-Sanchez

2D automated visual inspection system for the remote quality control of SMD assembly

In this paper, we present a general description of a new automated visual inspection system designed with a mechatronic approach, to address the problem of quality control in a SMT assembly process line. The system provides hardware and software facilities to be used as a test bench for new algorithms related to inspection and decision making, and it allows for remote access. We include a description of our first application to detect presence/absence or misplace of surface mounted devices using 2D analysis and 3D reconstruction. Also, we describe the remote access package developed with Jini/spl trade/ technologies to integrate our system to the Jini/spl trade/ Virtual Manufacturing Lab. This AVI system was created as a part of the Mexico-USA project in manufacturing research, MANET.

Integration of force-position control and haptic interface facilities for a virtual excavator simulator

In this paper we present the advances in the design and develop of a system used to simplify the excavator digging tasks based in a dynamical model of an excavator an anthropomorphic auto-balanced haptic interface and a force-position control law. The objective of this system is to reduce the training period and simplify the execution of digging tasks. This system makes possible the kinesthetic coupling between the operator and the machine providing information to the operator about the interaction forces between the excavator and the soil. The dynamical models of the excavator and the haptic devise were calculated employing the Euler-Lagrange formalism. With this formalism we obtain a new general dynamical model of an excavator including the dynamical effects of the hydraulic actuators. We present simulation results of the closed loop system considering the interaction between the haptic devise and the excavator

An adaptive neural network controller for visual tracking of constrained robot manipulators

Diverse image-based tracking schemes of robot moving in free motion have been proposed, and experimentally validated, whose position and velocity image tracking errors converge to zero. However, visual servoing for constrained motion robot tasks has not been addressed so as to provide control schemes that guarantee simultaneous tracking of position, velocity and contact force trajectories for dynamic robot models. The main difficulty lies from the fact that camera information cannot be used to drive force trajectories. Recognizing this fact, in this paper a unique error manifold that includes position-velocity errors and force errors in orthogonal complements is proposed under the framework of passivity, to yield a synergetic scheme that fuses camera, encoder and force sensor signals. This seemingly fusion of all tracking errors into a unique error variable allows to propose a new control system which guarantees local exponential tracking of all error trajectories. A neural network, driven by an orthogonalized second order sliding mode surface is derived to compensate approximately for nonlinear robot dynamics. Residual errors that arise because of the finite size of the neural network are finally eliminated via two sliding modes. Simulations results are presented and discussed.

Dynamic response of BLDC-thruster for small scale Quadrotors under aerodynamic load torque

In multi-rotor UAVs, a controlled Thrust is a main factor to achieve a safe and stable flight. Thrust is the result of a coordinated action of a set of symmetrically distributed thrusters whose single contribution is usually described as a square function of its rotor speed; however, aerodynamic forces induce a load torque on the rotor that disturb its expected speed response, thus its effective Thrust, affecting the whole performance of the aircraft. In this paper, we analyse and quantify the effects of the aerodynamic load torque induced on the spinning propeller of a BLDC thruster used in small scale Quadrotors and present some experimental validation. We describe the model of a 3-phase thruster with a two blade propeller of fixed pitch angle, we analyse its numerical simulation to determine the effects of the induced load torque on the dynamic response of the rotor, and we experimentally verify the results assuming ideal conditions of hover flight. Finally we illustrate the convenience of using feedback control to reduce the sensibility of thrusters face to non modelled dynamics applying a PD controller and we discuss about the importance of an accurate dynamic model of the thruster for control purposes.

Modeling and simulation of a propeller-engine system for Unmanned Aerial Vehicles

In this paper we present a model of a Propeller-Engine system and a simulation analysis of its dynamics in order to estimate the total load torque produced by the aerodynamic effects of a spinning propeller attached to its rotor when it is used as a thruster in small scale Unmanned Aerial Vehicles. The contribution is twofold: first, we obtain the model of a composed propeller-engine system introducing the mechanical load of a turning propeller to the electro-mechanical properties of a Brushless Direct Current motor, to determine the total thrust and the load torque with respect to its angular velocity, and then, we present the results of a numerical simulation of its dynamical behavior under hovering conditions. The aim of this work is to establish the basis for new developments in the area of control to improve the stability of flight in Unmanned Aerial Vehicles avoiding drifting.

Modular Platform for Haptic Guidance in Paediatric Rehabilitation of Upper Limb Neuromuscular Disabilities

In this paper, we present a haptic guidance platform to support physical rehabilitation of neuromuscular disabilities, providing a solution to the problem of the increasing demand of neuromuscular therapy in overcrowded facilities with deficit of rehabilitation professionals. The platform, characterized by a portable modular architecture, can be configured according to the treatment suggested by the physician, for instance, a Local Haptic Guidance configuration for patients requiring a continuous repetition of coordinated movements to recover, or improve, motor skills, and, a Remotely- Assisted Haptic Guidance for a direct intervention of the therapist, evaluating and stimulating, simultaneously, the neuromuscular condition of the patient. We also include some preliminary results when it is applied to treat two paediatric cases of congenital disease: Hemiparesis and Myelomeningocele.

IDENTIFICATION OF THE HUMAN BEHAVIOR IN VIRTUAL ENVIRONMENT TASKS AS A NON-LINEAR CONTROL BLOCK

Abstract First results on characterizing the human action as a controller are presented. The corresponding model of the human behavior as a control block is obtained by means of experimentation, and statistically validated. The identified human control mode corresponds to a nonlinear PID model. Using the methodology presented in this paper, it is possible to forecast parameter magnitude and therefore to implement a predictive system of the human behavior. The experimental platform consists of a 3D virtual space and a PHANToM haptic interface. A dual AMD Athlon-MP processor computer is used as real-time processing unit. RTLinux 3.1 operating system and PHANToM driver written by Zdenek Kabelac are used in order to achieve timing restrictions.

Passive Velocity Field Control for contour tracking of robots with model-free controller

A simple, fast and robust Passive Velocity Field Control (PVFC) scheme for contour tracking in 2D and 3D is presented. A model-free and chattering-free second order sliding mode controller is proposed, which enforces an invariant manifold for all time such that the generalized velocity tracks the spatial velocity field. A constructive simple and intuitive method to design this velocity field is built upon a fuzzy aggregation of orthogonal vectors to guide the end-effector subject to a dissipative map. Stability properties in the sense of Lyapunov establish the fast and yet smooth tracking with typical robustness of sliding modes. In this way, the closed-loop system exhibits the mildness of PVFC but it evades the subtle complexities of the original approach PVFC. A simulation study is discussed, and experimental results highlight the characteristics of the proposed approach.

Visual control for trajectory tracking of Quadrotors and real-time analysis on an emulated environment

Quadrotor are non-inertial systems with inherent nonlinear, very fast and very unstable dynamics where measurements of their state variables in an absolute frame of reference are very complex in GPS denied environments, such as indoors. In order to design control strategies for Quadrotors, we solve problems of imprecisely known models and noisily, or unavailable, position and speed measurements, and requirements of a safety test-bench for the first stages of design. In this paper, we face the problem of control of a Quadrotor using visual information and of a safe virtual Real-Time test of the controlled system. The contribution is twofold; first we present a model-free control law for tracking non-inertial robots, using as a case of study a Quadrotor, and we propose a Real-Time analysis of the dynamical behavior of the closed-loop system based on experimental data obtained using an emulation-based implementation architecture where the environment is a numerical emulation of the real one. The control of attitude and position are designed based on a Second Order Sliding Mode and PD like approaches, respectively, and the feedback state is obtained visually using an easy to program and portable Particle Filter for positions and a Second Order Differentiator for time derivatives. We describe the numerical simulation test bench and include some results obtained in Real- Time on an emulated environment.

Cartesian sliding PD force-position control for constrained robots under Jacobian uncertainty

Abstract Joint control requires to map, using ill-posed inverse kinematics, desired cartesian tasks into desired joint tasks, then it codes them into desired joint trajectories. To avoid this, cartesian control directly codes the cartesian task in cartesian coordinates, avoiding in this way any computation of inverse kinematics, which is relevant in particular for force control since the force task is always given in operational (cartesian) space. In this paper, a local cartesian exponential tracking control for constrained motion without using inverse kinematics is proposed. The novelty lies, besides its nontrivial extension from ODE (position) robots to DAE (force) robots, in the fact that fast cartesian tracking is obtained without using the model of the robot nor exact knowledge of inverse jacobian. The scheme shows a smooth control input. Simulations results shows the expected tracking performance.