Robust Tracking in Underactuated Systems Using Flatness-Based ADRC With Cascade Observers

Abstract

In this work, the problem of trajectory tracking in uncertain underactuated systems is considered. To solve it, a combination of differential flatness and active disturbance rejection control (ADRC) is proposed. The controller design is synthesized in the absence of detailed knowledge of the system model and focuses on dealing with over-amplification of measurement noise, typically seen in conventional single high-gain observer-centered control approaches. The introduced solution is based on fully utilizing the information already available about the governed system, without the necessity for additional measurement devices. To be easily implementable, it is expressed in an industry familiar error-based form with a straightforward tuning method. Through experimental verification, the proposed approach is shown to enhance the disturbance-rejection capabilities of the standard ADRC structure and reduce its sensitivity to measurement noise, thus increasing its practical appeal.

Vibration Isolation With Passive Linkage Mechanisms

“…Thus, the equation of motion for the BIAVP-NI can be obtained as Substituting (15) to (18) into (14) then the equation of motion of the BIAVP-NI is…”

“…Active vibration control is extensively studied with advanced actuators and velocity or displacement feedback control schemes [13,14]. However, active approaches not only require excessive energy [15,16] but also significantly increase system complexity or maintenance cost [17,18]. Vibration suppression can also be done via design of active or passive inertia units [19,20].…”

Simplifying ADRC design with error-based framework: case study of a DC–DC buck power converter

“…Within some small neighborhood of the origin of the estimation error | | ≜ |e −ê| , a linear (n + m)th order ESO observer in form of (26), estimates state variables x 1 , … , x n , as well as the auxiliary state variables x n+1 , … , x n+m , as defined in (24). It is guaranteed by providing a set of design coefficients l 1 , … , l n+m , chosen so that the roots of a characteristic polynomial (27) are located (28)…”

“…The error-based ADRC has been successfully applied by now to a variety of control problems including mechanical vibration compensation [21,22], robotic manipulator control [23,24], observer design with suppression of sensor noise [25][26][27], position control of a telescope mount [28], UAV control [29,30], as well as power electronics control [31,32].…”

Active Disturbance Rejection Control for Reference Trajectory Tracking Tasks in the Pendubot System

“…Moreover, the tangent linearization lead to a cascade structure where the system can be represented in terms of a tandem set of second order systems connected by physically measurable signals (overcoming a main drawback of flatnessbased controllers). This structure allows simple solutions for trajectory tracking in a class of nonlinear underactuated systems but the locally of the solution needs to be overcome in order to find a suitable practical methodology [19], [20]. Other benefits of the cascade structure allows to enhance the high gain extended state observer based designs through lower gain tuning schemes (see [21])…”