66,777 research outputs found
'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
Complex order control for improved loop-shaping in precision positioning
This paper presents a complex order filter developed and subsequently
integrated into a PID-based controller design. The nonlinear filter is designed
with reset elements to have describing function based frequency response
similar to that of a linear (practically non-implementable) complex order
filter. This allows for a design which has a negative gain slope and a
corresponding positive phase slope as desired from a loop-shaping
controller-design perspective. This approach enables improvement in precision
tracking without compromising the bandwidth or stability requirements. The
proposed designs are tested on a planar precision positioning stage and
performance compared with PID and other state-of-the-art reset based
controllers to showcase the advantages of this filter
No More Differentiator in PID:Development of Nonlinear Lead for Precision Mechatronics
Industrial PID consists of three elements: Lag (integrator), Lead
(Differentiator) and Low Pass Filters (LPF). PID being a linear control method
is inherently bounded by the waterbed effect due to which there exists a
trade-off between precision \& tracking, provided by Lag and LPF on one side
and stability \& robustness, provided by Lead on the other side. Nonlinear
reset strategies applied in Lag and LPF elements have been very effective in
reducing this trade-off. However, there is lack of study in developing a reset
Lead element. In this paper, we develop a novel lead element which provides
higher precision and stability compared to the linear lead filter and can be
used as a replacement for the same. The concept is presented and validated on a
Lorentz-actuated nanometer precision stage. Improvements in precision, tracking
and bandwidth are shown through two separate designs. Performance is validated
in both time and frequency domain to ensure that phase margin achieved on the
practical setup matches design theories.Comment: European Control Conference 201
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
Static inverters which sum a plurality of waves Patent
Describing static inverter with single or multiple phase outpu
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