Time-delay systems: an overview of some recent advances and open problems

Introduction to linear and nonlinear programming

Dynamic analysis of flexible manipulators, a literature review

This article considered the problem of designing joint-actuation mechanisms that can allow fast and accurate operation of a robot arm, while guaranteeing a suitably limited level of injury risk. Different approaches to the problem were presented, and a method of performance evaluation was proposed based on minimum-time optimal control with safety constraints. The variable stiffness transmission (VST) scheme was found to be one of a few different possible schemes that allows the most flexibility and potential performance. Some aspects related to the implementation of the mechanics and control of VST actuation were also reported.

Fast and "soft-arm" tactics [robot arm design]

Non-linear state estimation and some related topics like parametric estimation, fault diagnosis and perturbation attenuation are tackled here via a new methodology in numerical differentiation. The corresponding basic system theoretic definitions and properties are presented within the framework of differential algebra, which permits to handle system variables and their derivatives of any order. Several academic examples and their computer simulations, with online estimations, illustrate our viewpoint.

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Non-linear estimation is easy

An observer-based set-point controller for robot manipulators with flexible joints

Tomei (1991) presented a globally asymptotically stable PD regulator for robots with flexible joints. A drawback of this scheme is that, as is well known, noise in velocity measurements degrades performance, and numerical differentiation is inaccurate for low and high speeds. On the other hand, approximate differentiation, replacing the derivative operator p by the high pass filter (bp/p+a), is commonly used in applications since it yields good behavior for regulation tasks. In this paper, we show that velocity measurement in Tomei's scheme can be replaced by approximate differentiation preserving global asymptotic stability for all positive values of b and a. Simulations that illustrate our result are also presented. >

Global regulation of flexible joint robots using approximate differentiation

This note presents simple controllers for achieving asymptotic trajectory (set-point and time-varying) tracking under the conditions of restricted input in vertical takeoff and landing aircraft. Unlike previous studies that apply nonlinear combination of saturated functions for stabilizing the closed-loop system, the proposed controllers are based on smooth functions that can easily be implemented in real time applications.

Simple Tracking Controllers for Autonomous VTOL Aircraft With Bounded Inputs

This paper proposes control schemes for a group of nonholonomic kinematic mobile robots for maintaining a desired formation along a time-parameterized path. The control approach is based in particular on the flatness property and the concept of virtual vehicles. The control objective is twofold: to maintain the formation structure during motion along a desired geometric path, and to follow a timing law that dominates the rate of advancement of the group and the arrival times to assigned sites. This paper suggests, in particular, control strategies for convoy-like vehicles and for rigid formations. The leading vehicle governs the overall group motion. However, each member of the group can independently split or merge and maneuver to avoid collision (assuming that the relevant data are available by communication/sensing means) during the group motion.

Amit Ailon

Papers

An observer-based set-point controller for robot manipulators with flexible joints

Global regulation of flexible joint robots using approximate differentiation

Simple Tracking Controllers for Autonomous VTOL Aircraft With Bounded Inputs

Control Strategies for Driving a Group of Nonholonomic Kinematic Mobile Robots in Formation Along a Time-Parameterized Path

Brief On controllability and trajectory tracking of a kinematic vehicle model