322 research outputs found
Gain-scheduling LPV control for autonomous vehicles including friction force estimation and compensation mechanism
© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This study presents a solution for the integrated longitudinal and lateral control problem of urban autonomousvehicles. It is based on a gain-scheduling linear parameter-varying (LPV) control approach combined with the use of anUnknown Input Observer (UIO) for estimating the vehicle states and friction force. Two gain-scheduling LPV controllers are usedin cascade configuration that use the kinematic and dynamic vehicle models and the friction and observed states provided bythe Unknown Input Observer (UIO). The LPV–UIO is designed in an optimal manner by solving a set of linear matrix inequalities(LMIs). On the other hand, the design of the kinematic and dynamic controllers lead to solve separately two LPV–LinearQuadratic Regulator problems formulated also in LMI form. The UIO allows to improve the control response in disturbanceaffected scenarios by estimating and compensating the friction force. The proposed scheme has been integrated with atrajectory generation module and tested in a simulated scenario. A comparative study is also presented considering the casesthat the friction force estimation is used or not to show its usefulnessPeer ReviewedPostprint (author's final draft
Kinematic control design for wheeled mobile robots with longitudinal and lateral slip
The motion control of wheeled mobile robots at high speeds under adverse
ground conditions is a difficult task, since the robots' wheels may be subject
to different kinds of slip. This work introduces an adaptive kinematic
controller that is capable of solving the trajectory tracking problem of a
nonholonomic mobile robot under longitudinal and lateral slip. While the
controller can effectively compensate for the longitudinal slip, the lateral
slip is a more involved problem to deal with, since nonholonomic robots cannot
directly produce movement in the lateral direction. To show that the proposed
controller is still able to make the mobile robot follow a reference trajectory
under lateral and longitudinal time-varying slip, the solutions of the robot's
position and orientation error dynamics are shown to be uniformly ultimately
bounded. Numerical simulations are presented to illustrate the robot's
performance using the proposed adaptive control law
Control techniques for mechatronic assisted surgery
The treatment response for traumatic head injured patients can be improved by
using an autonomous robotic system to perform basic, time-critical emergency neurosurgery,
reducing costs and saving lives. In this thesis, a concept for a neurosurgical robotic system is proposed to perform three specific emergency neurosurgical procedures; they are the placement of an intracranial pressure monitor, external
ventricular drainage, and the evacuation of chronic subdural haematoma. The control
methods for this system are investigated following a curiosity led approach. Individual problems are interpreted in the widest sense and solutions posed that are general in nature. Three main contributions result from this approach: 1)
a clinical evidence based review of surgical robotics and a methodology to assist in their evaluation, 2) a new controller for soft-grasping of objects, and 3) new propositions and theorems for chatter suppression sliding mode controllers. These contributions directly assist in the design of the control system of the neurosurgical robot and, more broadly, impact other areas outside the narrow con nes of the target application. A methodology for applied research in surgical robotics is proposed. The methodology sets out a hierarchy of criteria consisting of three tiers, with the most important being the bottom tier and the least being the top tier. It is argued that
a robotic system must adhere to these criteria in order to achieve acceptability. Recent commercial systems are reviewed against these criteria, and are found to conform up to at least the bottom and intermediate tiers. However, the lack of
conformity to the criteria in the top tier, combined with the inability to conclusively
prove increased clinical benefit, particularly symptomatic benefit, is shown to be hampering the potential of surgical robotics in gaining wide establishment. A control scheme for soft-grasping objects is presented. Grasping a soft or fragile object requires the use of minimum contact force to prevent damage or deformation. Without precise knowledge of object parameters, real-time feedback
control must be used to regulate the contact force and prevent slip. Moreover, the controller must be designed to have good performance characteristics to rapidly modulate the fingertip contact force in response to a slip event. A fuzzy sliding mode controller combined with a disturbance observer is proposed for contact force control and slip prevention. The robustness of the controller is evaluated through
both simulation and experiment. The control scheme was found to be effective and robust to parameter uncertainty. When tested on a real system, however, chattering phenomena, well known to sliding mode research, was induced by the
unmodelled suboptimal components of the system (filtering, backlash, and time delays). This reduced the controller performance. The problem of chattering and potential solutions are explored. Real systems using sliding mode controllers, such as the control scheme for soft-grasping, have a tendency to chatter at high frequencies. This is caused by the sliding mode
controller interacting with un-modelled parasitic dynamics at the actuator-input
and sensor-output of the plant. As a result, new chatter-suppression sliding mode controllers have been developed, which introduce new parameters into the system. However, the effect any particular choice of parameters has on system performance
is unclear, and this can make tuning the parameters to meet a set of performance
criteria di cult. In this thesis, common chatter-suppression sliding mode control
strategies are surveyed and simple design and estimation methods are proposed.
The estimation methods predict convergence, chattering amplitude, settling time,
and maximum output bounds (overshoot) using harmonic linearizations and invariant
ellipsoid sets
Active disturbance rejection control for unmanned tracked vehicles in leader-follower scenarios: discrete-time implementation and field test validation
This paper presents a systematic design of an active disturbance rejection
control (ADRC) system for unmanned tracked vehicles (UTVs) in leader-follow
formation. Two ADRC controllers are designed for the lateral and the
longitudinal channels of the UTV based on control errors in the cross-track and
the along-track directions. Through simulations, the proposed ADRC approach is
first shown to outperform the conventional PI/PID controllers in scenarios
involving sudden changes in the leader motion dynamics, slippage disturbances,
and measurement noise. Then, a comprehensive experimental validation of the
proposed leader-follower control is performed using a laboratory UTV equipped
with a camera and laser sensors (to enable the calculation of error signals).
In order to provide more effective interaction between the human (leader) and
the UTV (follower) during the leader-follower task, a camera-based subsystem
for human pose recognition is developed and deployed. Finally, the experimental
results obtained outdoors demonstrate that the proposed ADRC-based
leader-follower UTV control system achieves high tracking capabilities,
robustness against slippage disturbances, and adaptability to changing
environmental conditions
A CENTER MANIFOLD THEORY-BASED APPROACH TO THE STABILITY ANALYSIS OF STATE FEEDBACK TAKAGI-SUGENO-KANG FUZZY CONTROL SYSTEMS
The aim of this paper is to propose a stability analysis approach based on the application of the center manifold theory and applied to state feedback Takagi-Sugeno-Kang fuzzy control systems. The approach is built upon a similar approach developed for Mamdani fuzzy controllers. It starts with a linearized mathematical model of the process that is accepted to belong to the family of single input second-order nonlinear systems which are linear with respect to the control signal. In addition, smooth right-hand terms of the state-space equations that model the processes are assumed. The paper includes the validation of the approach by application to stable state feedback Takagi-Sugeno-Kang fuzzy control system for the position control of an electro-hydraulic servo-system
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