Robust loop-shaping control for a nano-positioning stage

Chen

2015 IEEE/SICE International Symposium on System Integration (SII)

2015

This paper applies a combined stage for fabricating Fresnel zone plane (FZP). The combined stage integrates piezoelectric transducers (PZT) and stepper motors, to achieve precise positioning over large strokes. Because PZT s non-linearities and system uncertainties might degrade system performance, we design robust controllers to cope with these obstacles for precision positioning. Then we integrate the stepper-motor stage for long-stroke movements. We implement the designed controllers to the combined stage, and apply it to fabricate the FZP by two photon polymerization (TPP) techniques. Last, the quality of FZP can be revealed by image tests.

Section: Introductionmentioning

confidence: 99%

“…apply H loop-shaping techniques[1], [11], to improve system performance. We adjust the weighting functions by experiments and select the following weighting function for the PZT stage:…”

mentioning

confidence: 99%

Robust control of a long-stroke precision stage: With applications to fresnel zone plane fabrication

Chen

2015 IEEE/SICE International Symposium on System Integration (SII)

2015

Journal of Vibration and Control

“…The positioning performance is further degraded because of hysteresis Wang et al (2014) and creep effects Mazlan & Ripin (2017) arising from the piezoelectric actuators popularly employed in nanopositioners. This is due to their desirable properties, such as high-bandwidth, ease of actuation and system integration, repeatability, nearly atomic-level resolution, frictionless and stictionless motion etc, Gu et al (2016).…”

Section: Introductionmentioning

confidence: 99%

A dual-loop tracking control approach to precise nanopositioning

Altaher

Russell

Aphale

2018

Nanopositioners are mechanical devices that can accurately move with a resolution in the nanometre scale. Due to their mechanical construction and the piezoelectric actuators popularly employed in nanopositioners, these devices have severe performance limitations due to resonance, hysteresis and creep. A number of techniques to control nanopositioners, both in open-loop and closed-loop, have been reported in literature. Closed-loop techniques clearly outperform open-loop techniques due to several desirable characteristics, such as robustness, high-bandwidth, absence of the need for tuning and high stability along with others. The most popular closed-loop control technique reported is one where a damping controller is first employed in an inner loop to damp the mechanical resonance of the nanopositioner, thereby increasing achievable bandwidth. Consequently, a tracking controller, typically an Integral controller or a Proportional-Integral controller, is implemented in the outer loop to enforce tracking of the reference signal, thereby reducing the positioning errors due to hysteresis and creep dynamics of the employed actuator. The most popular trajectory a nanopositioner is forced to track is a raster scan, which is generated by making one axis of the nanopositioner follow a triangular trajectory and the other follow a slow ramp or staircase. It is quite clear that a triangle wave (a finite velocity, zero acceleration signal) cannot be perfectly tracked by a first-order integrator and a double integrator is necessary to deliver error-free tracking. However, due to the phase profile of the damped closed-loop system, implementing a double integrator is difficult. This paper proposes a method by which to implement two integrators focused on the tracking performance.The criteria for gain selection, stability analysis, error analysis, simulations and experimental results are provided. These demonstrate a reduction in positioning error by 50%, when compared to the traditional damping plus first-order integral tracking approach.

“…Helfrich et al 13 combined iterative learning control and robust control to obtain an RMSE of less than 40 nm on three axes. Wang et al 14 applied robust loop-shaping techniques to PZT to achieve an RMSE of 5.4 nm for a travel of 1000 nm. Other robust control techniques can also be considered.…”

Section: Introductionmentioning

confidence: 99%

Impacts of sensor layouts on the performance of a long-stroke nano-positioning stage

Advances in Mechanical Engineering

Chen

et al. 2016

Self Cite

This article develops a long-stroke nano-positioning stage and discusses the impacts of sensor layouts on the positioning performance. The stage consists of a piezoelectric-transducer stage and a motor stage. First, we obtain the transfer functions of the two stages by experiments and design robust loop-shaping controllers to improve their performance. Second, we integrate the two stages and designed two sensor layouts, a local sensor layout using encoders and a global sensor layout using laser interferometers, to achieve precision positioning for large travels. Finally, we implement the designed controllers and sensor layouts for experimental verification. Based on the results, the proposed combined stage is deemed effective in accomplishing nano-positioning for long displacements. In addition, the local sensor layout can achieve high precision but with global misalignments, while the global sensor layout can eliminate the global misalignments but suffer large sensor noises. Therefore, we further constructed a modified sensor layout that can combine the merits and achieve precision positioning with a root-mean-square error of 5 nm and a misalignment error of 16 nm for a 10-cm travel.