3 research outputs found
Beyond the Waterbed Effect: Development of Fractional Order CRONE Control with Non-Linear Reset
In this paper a novel reset control synthesis method is proposed: CRONE reset
control, combining a robust fractional CRONE controller with non-linear reset
control to overcome waterbed effect. In CRONE control, robustness is achieved
by creation of constant phase behaviour around bandwidth with the use of
fractional operators, also allowing more freedom in shaping the open-loop
frequency response. However, being a linear controller it suffers from the
inevitable trade-off between robustness and performance as a result of the
waterbed effect. Here reset control is introduced in the CRONE design to
overcome the fundamental limitations. In the new controller design, reset phase
advantage is approximated using describing function analysis and used to
achieve better open-loop shape. Sufficient quadratic stability conditions are
shown for the designed CRONE reset controllers and the control design is
validated on a Lorentz-actuated nanometre precision stage. It is shown that for
similar phase margin, better performance in terms of reference-tracking and
noise attenuation can be achieved.Comment: American Control Conference 201
'Constant in gain Lead in phase' element - Application in precision motion control
This work presents a novel 'Constant in gain Lead in phase' (CgLp) element
using nonlinear reset technique. PID is the industrial workhorse even to this
day in high-tech precision positioning applications. However, Bode's gain phase
relationship and waterbed effect fundamentally limit performance of PID and
other linear controllers. This paper presents CgLp as a controlled nonlinear
element which can be introduced within the framework of PID allowing for wide
applicability and overcoming linear control limitations. Design of CgLp with
generalized first order reset element (GFORE) and generalized second order
reset element (GSORE) (introduced in this work) is presented using describing
function analysis. A more detailed analysis of reset elements in frequency
domain compared to existing literature is first carried out for this purpose.
Finally, CgLp is integrated with PID and tested on one of the DOFs of a planar
precision positioning stage. Performance improvement is shown in terms of
tracking, steady-state precision and bandwidth