+++ title = "Design, modeling and control of nanopositioning systems" author = ["Thomas Dehaeze"] description = "Talks about various topics related to nano-positioning systems." keywords = ["Control", "Metrology", "Flexible Joints"] draft = false +++ Tags : [Piezoelectric Actuators]({{< relref "piezoelectric_actuators" >}}), [Flexible Joints]({{< relref "flexible_joints" >}}) Reference : ([Fleming and Leang 2014](#org9f0983e)) Author(s) : Fleming, A. J., & Leang, K. K. Year : 2014 ## Introduction {#introduction} ### Introduction to Nanotechnology {#introduction-to-nanotechnology} ### Introduction to Nanopositioning {#introduction-to-nanopositioning} ### Scanning Probe Microscopy {#scanning-probe-microscopy} ### Challenges with Nanopositioning Systems {#challenges-with-nanopositioning-systems} #### Hysteresis {#hysteresis} #### Creep {#creep} #### Thermal Drift {#thermal-drift} #### Mechanical Resonance {#mechanical-resonance} ### Control of Nanopositioning Systems {#control-of-nanopositioning-systems} #### Feedback Control {#feedback-control} #### Feedforward Control {#feedforward-control} ### Book Summary {#book-summary} #### Assumed Knowledge {#assumed-knowledge} #### Content Summary {#content-summary} ### References {#references} ## Piezoelectric Transducers {#piezoelectric-transducers} ### The Piezoelectric Effect {#the-piezoelectric-effect} ### Piezoelectric Compositions {#piezoelectric-compositions} ### Manufacturing Piezoelectric Ceramics {#manufacturing-piezoelectric-ceramics} ### Piezoelectric Transducers {#piezoelectric-transducers} ### Application Considerations {#application-considerations} ### Response of Piezoelectric Actuators {#response-of-piezoelectric-actuators} ### Modeling Creep and Vibration in Piezoelectric Actuators {#modeling-creep-and-vibration-in-piezoelectric-actuators} ### Chapter Summary {#chapter-summary} ### References {#references} ## Types of Nanopositioners {#types-of-nanopositioners} ### Piezoelectric Tube Nanopositioners {#piezoelectric-tube-nanopositioners} #### 63mm Piezoelectric Tube {#63mm-piezoelectric-tube} #### 40mm Piezoelectric Tube Nanopositioner {#40mm-piezoelectric-tube-nanopositioner} ### Piezoelectric Stack Nanopositioners {#piezoelectric-stack-nanopositioners} #### Phyisk Instrumente P-734 Nanopositioner {#phyisk-instrumente-p-734-nanopositioner} #### Phyisk Instrumente P-733.3DD Nanopositioner {#phyisk-instrumente-p-733-dot-3dd-nanopositioner} #### Vertical Nanopositioners {#vertical-nanopositioners} #### Rotational Nanopositioners {#rotational-nanopositioners} #### Low Temperature and UHV Nanopositioners {#low-temperature-and-uhv-nanopositioners} #### Tilting Nanopositioners {#tilting-nanopositioners} #### Optical Objective Nanopositioners {#optical-objective-nanopositioners} ### References {#references} ## Mechanical Design: Flexure-Based Nanopositioners {#mechanical-design-flexure-based-nanopositioners} ### Introduction {#introduction} ### Operating Environment {#operating-environment} ### Methods for Actuation {#methods-for-actuation} ### Flexure Hinges {#flexure-hinges} #### Introduction {#introduction} #### Types of Flexures {#types-of-flexures} #### Flexure Hinge Compliance Equations {#flexure-hinge-compliance-equations} #### Stiff Out-of-Plane Flexure Designs {#stiff-out-of-plane-flexure-designs} #### Failure Considerations {#failure-considerations} #### Finite Element Approach for Flexure Design {#finite-element-approach-for-flexure-design} ### Material Considerations {#material-considerations} #### Materials for Flexure and Platform Design {#materials-for-flexure-and-platform-design} #### Thermal Stability of Materials {#thermal-stability-of-materials} ### Manufacturing Techniques {#manufacturing-techniques} ### Design Example: A High-Speed Serial-Kinematic Nanopositioner {#design-example-a-high-speed-serial-kinematic-nanopositioner} #### State-of-the-Art Designs {#state-of-the-art-designs} #### Tradeoffs and Limitations in Speed {#tradeoffs-and-limitations-in-speed} #### Serial- Versus Parallel-Kinematic Configurations {#serial-versus-parallel-kinematic-configurations} #### Piezoactuator Considerations {#piezoactuator-considerations} #### Preloading Piezo-Stack Actuators {#preloading-piezo-stack-actuators} #### Flexure Design for Lateral Positioning {#flexure-design-for-lateral-positioning} #### Design of Vertical Stage {#design-of-vertical-stage} #### Fabrication and Assembly {#fabrication-and-assembly} #### Drive Electronics {#drive-electronics} \*\*\*\*0 Experimental Results ### Chapter Summary {#chapter-summary} ### References {#references} ## Position Sensors {#position-sensors} ### Introduction {#introduction} ### Sensor Characteristics {#sensor-characteristics} #### Calibration and Nonlinearity {#calibration-and-nonlinearity} #### Drift and Stability {#drift-and-stability} #### Bandwidth {#bandwidth} #### Noise {#noise} #### Resolution {#resolution} #### Combining Errors {#combining-errors} #### Metrological Traceability {#metrological-traceability} ### Nanometer Position Sensors {#nanometer-position-sensors} #### Resistive Strain Sensors {#resistive-strain-sensors} #### Piezoresistive Strain Sensors {#piezoresistive-strain-sensors} #### Piezoelectric Strain Sensors {#piezoelectric-strain-sensors} #### Capacitive Sensors {#capacitive-sensors} #### MEMs Capacitive and Thermal Sensors {#mems-capacitive-and-thermal-sensors} #### Eddy-Current Sensors {#eddy-current-sensors} #### Linear Variable Displacement Transformers {#linear-variable-displacement-transformers} #### Laser Interferometers {#laser-interferometers} #### Linear Encoders {#linear-encoders} ### Comparison and Summary {#comparison-and-summary} ### Outlook and Future Requirements {#outlook-and-future-requirements} ### References {#references} ## Shunt Control {#shunt-control} ### Introduction {#introduction} ### Shunt Circuit Modeling {#shunt-circuit-modeling} #### Open-Loop {#open-loop} #### Shunt Damping {#shunt-damping} ### Implementation {#implementation} ### Experimental Results {#experimental-results} #### Tube Dynamics {#tube-dynamics} #### Amplifier Performance {#amplifier-performance} #### Shunt Damping Performance {#shunt-damping-performance} ### Chapter Summary {#chapter-summary} ### References {#references} ## Feedback Control {#feedback-control} ### Introduction {#introduction} ### Experimental Setup {#experimental-setup} ### PI Control {#pi-control} ### PI Control with Notch Filters {#pi-control-with-notch-filters} ### PI Control with IRC Damping {#pi-control-with-irc-damping} ### Performance Comparison {#performance-comparison} ### Noise and Resolution {#noise-and-resolution} ### Analog Implementation {#analog-implementation} ### Application to AFM Imaging {#application-to-afm-imaging} \*\*\*0 Repetitive Control \*\*\*\*0.1 Introduction \*\*\*\*0.2 Repetitive Control Concept and Stability Considerations \*\*\*\*0.3 Dual-Stage Repetitive Control \*\*\*\*0.4 Handling Hysteresis \*\*\*\*0.5 Design and Implementation \*\*\*\*0.6 Experimental Results and Discussion \*\*\*1 Summary ### References {#references} ## Force Feedback Control {#force-feedback-control} ### Introduction {#introduction} ### Modeling {#modeling} #### Actuator Dynamics {#actuator-dynamics} #### Sensor Dynamics {#sensor-dynamics} #### Sensor Noise {#sensor-noise} #### Mechanical Dynamics {#mechanical-dynamics} #### System Properties {#system-properties} #### Example System {#example-system} ### Damping Control {#damping-control} ### Tracking Control {#tracking-control} #### Relationship Between Force and Displacement {#relationship-between-force-and-displacement} #### Integral Displacement Feedback {#integral-displacement-feedback} #### Direct Tracking Control {#direct-tracking-control} #### Dual Sensor Feedback {#dual-sensor-feedback} #### Low Frequency Bypass {#low-frequency-bypass} #### Feedforward Inputs {#feedforward-inputs} #### Higher-Order Modes {#higher-order-modes} ### Experimental Results {#experimental-results} #### Experimental Nanopositioner {#experimental-nanopositioner} #### Actuators and Force Sensors {#actuators-and-force-sensors} #### Control Design {#control-design} #### Noise Performance {#noise-performance} ### Chapter Summary {#chapter-summary} ### References {#references} ## Feedforward Control {#feedforward-control} ### Why Feedforward? {#why-feedforward} ### Modeling for Feedforward Control {#modeling-for-feedforward-control} ### Feedforward Control of Dynamics and Hysteresis {#feedforward-control-of-dynamics-and-hysteresis} #### Simple DC-Gain Feedforward Control {#simple-dc-gain-feedforward-control} #### An Inversion-Based Feedforward Approach for Linear Dynamics {#an-inversion-based-feedforward-approach-for-linear-dynamics} #### Frequency-Weighted Inversion: The Optimal Inverse {#frequency-weighted-inversion-the-optimal-inverse} #### Application to AFM Imaging {#application-to-afm-imaging} ### Feedforward and Feedback Control {#feedforward-and-feedback-control} #### Application to AFM Imaging {#application-to-afm-imaging} ### Iterative Feedforward Control {#iterative-feedforward-control} #### The ILC Problem {#the-ilc-problem} #### Model-Based ILC {#model-based-ilc} #### Nonlinear ILC {#nonlinear-ilc} #### Conclusions {#conclusions} ### References {#references} ## Command Shaping {#command-shaping} ### 10.1 Introduction {#10-dot-1-introduction} #### 10.1.1 Background {#10-dot-1-dot-1-background} #### 10.1.2 The Optimal Periodic Input {#10-dot-1-dot-2-the-optimal-periodic-input} ### 10.2 Signal Optimization {#10-dot-2-signal-optimization} ### 10.3 Frequency Domain Cost Functions {#10-dot-3-frequency-domain-cost-functions} #### 10.3.1 Background: Discrete Fourier Series {#10-dot-3-dot-1-background-discrete-fourier-series} #### 10.3.2 Minimizing Signal Power {#10-dot-3-dot-2-minimizing-signal-power} #### 10.3.3 Minimizing Frequency Weighted Power {#10-dot-3-dot-3-minimizing-frequency-weighted-power} #### 10.3.4 Minimizing Velocity and Acceleration {#10-dot-3-dot-4-minimizing-velocity-and-acceleration} #### 10.3.5 Single-Sided Frequency Domain Calculations {#10-dot-3-dot-5-single-sided-frequency-domain-calculations} ### 10.4 Time Domain Cost Function {#10-dot-4-time-domain-cost-function} #### 10.4.1 Minimum Velocity {#10-dot-4-dot-1-minimum-velocity} #### 10.4.2 Minimum Acceleration {#10-dot-4-dot-2-minimum-acceleration} #### 10.4.3 Frequency Weighted Objectives {#10-dot-4-dot-3-frequency-weighted-objectives} ### 10.5 Application to Scan Generation {#10-dot-5-application-to-scan-generation} #### 10.5.1 Choosing β and K {#10-dot-5-dot-1-choosing-β-and-k} #### 10.5.2 Improving Feedback and Feedforward Controllers {#10-dot-5-dot-2-improving-feedback-and-feedforward-controllers} ### 10.6 Comparison to Other Techniques {#10-dot-6-comparison-to-other-techniques} ### 10.7 Experimental Application {#10-dot-7-experimental-application} ### 10.8 Chapter Summary {#10-dot-8-chapter-summary} ### References {#references} ## Hysteresis Modeling and Control {#hysteresis-modeling-and-control} ### 11.1 Introduction {#11-dot-1-introduction} ### 11.2 Modeling Hysteresis {#11-dot-2-modeling-hysteresis} #### 11.2.1 Simple Polynomial Model {#11-dot-2-dot-1-simple-polynomial-model} #### 11.2.2 Maxwell Slip Model {#11-dot-2-dot-2-maxwell-slip-model} #### 11.2.3 Duhem Model {#11-dot-2-dot-3-duhem-model} #### 11.2.4 Preisach Model {#11-dot-2-dot-4-preisach-model} #### 11.2.5 Classical Prandlt-Ishlinksii Model {#11-dot-2-dot-5-classical-prandlt-ishlinksii-model} ### 11.3 Feedforward Hysteresis Compensation {#11-dot-3-feedforward-hysteresis-compensation} #### 11.3.1 Feedforward Control Using the Presiach Model {#11-dot-3-dot-1-feedforward-control-using-the-presiach-model} #### 11.3.2 Feedforward Control Using the Prandlt-Ishlinksii Model {#11-dot-3-dot-2-feedforward-control-using-the-prandlt-ishlinksii-model} ### 11.4 Chapter Summary {#11-dot-4-chapter-summary} ### References {#references} ## Charge Drives {#charge-drives} ### 12.1 Introduction {#12-dot-1-introduction} ### 12.2 Charge Drives {#12-dot-2-charge-drives} ### 12.3 Application to Piezoelectric Stack Nanopositioners {#12-dot-3-application-to-piezoelectric-stack-nanopositioners} ### 12.4 Application to Piezoelectric Tube Nanopositioners {#12-dot-4-application-to-piezoelectric-tube-nanopositioners} ### 12.5 Alternative Electrode Configurations {#12-dot-5-alternative-electrode-configurations} #### 12.5.1 Grounded Internal Electrode {#12-dot-5-dot-1-grounded-internal-electrode} #### 12.5.2 Quartered Internal Electrode {#12-dot-5-dot-2-quartered-internal-electrode} ### 12.6 Charge Versus Voltage {#12-dot-6-charge-versus-voltage} #### 12.6.1 Advantages {#12-dot-6-dot-1-advantages} #### 12.6.2 Disadvantages {#12-dot-6-dot-2-disadvantages} ### 12.7 Impact on Closed-Loop Control {#12-dot-7-impact-on-closed-loop-control} ### 12.8 Chapter Summary {#12-dot-8-chapter-summary} ### References {#references} ## Noise in Nanopositioning Systems {#noise-in-nanopositioning-systems} ### 13.1 Introduction {#13-dot-1-introduction} ### 13.2 Review of Random Processes {#13-dot-2-review-of-random-processes} #### 13.2.1 Probability Distributions {#13-dot-2-dot-1-probability-distributions} #### 13.2.2 Expected Value, Moments, Variance, and RMS {#13-dot-2-dot-2-expected-value-moments-variance-and-rms} #### 13.2.3 Gaussian Random Variables {#13-dot-2-dot-3-gaussian-random-variables} #### 13.2.4 Continuous Random Processes {#13-dot-2-dot-4-continuous-random-processes} #### 13.2.5 Joint Density Functions and Stationarity {#13-dot-2-dot-5-joint-density-functions-and-stationarity} #### 13.2.6 Correlation Functions {#13-dot-2-dot-6-correlation-functions} #### 13.2.7 Gaussian Random Processes {#13-dot-2-dot-7-gaussian-random-processes} #### 13.2.8 Power Spectral Density {#13-dot-2-dot-8-power-spectral-density} #### 13.2.9 Filtered Random Processes {#13-dot-2-dot-9-filtered-random-processes} #### 13.2.10 White Noise {#13-dot-2-dot-10-white-noise} #### 13.2.11 Spectral Density in V/sqrtHz {#13-dot-2-dot-11-spectral-density-in-v-sqrthz} #### 13.2.12 Single- and Double-Sided Spectra {#13-dot-2-dot-12-single-and-double-sided-spectra} ### 13.3 Resolution and Noise {#13-dot-3-resolution-and-noise} ### 13.4 Sources of Nanopositioning Noise {#13-dot-4-sources-of-nanopositioning-noise} #### 13.4.1 Sensor Noise {#13-dot-4-dot-1-sensor-noise} #### 13.4.2 External Noise {#13-dot-4-dot-2-external-noise} #### 13.4.3 Amplifier Noise {#13-dot-4-dot-3-amplifier-noise} ### 13.5 Closed-Loop Position Noise {#13-dot-5-closed-loop-position-noise} #### 13.5.1 Noise Sensitivity Functions {#13-dot-5-dot-1-noise-sensitivity-functions} #### 13.5.2 Closed-Loop Position Noise Spectral Density {#13-dot-5-dot-2-closed-loop-position-noise-spectral-density} #### 13.5.3 Closed-Loop Noise Approximations with Integral Control {#13-dot-5-dot-3-closed-loop-noise-approximations-with-integral-control} #### 13.5.4 Closed-Loop Position Noise Variance {#13-dot-5-dot-4-closed-loop-position-noise-variance} #### 13.5.5 A Note on Units {#13-dot-5-dot-5-a-note-on-units} ### 13.6 Simulation Examples {#13-dot-6-simulation-examples} #### 13.6.1 Integral Controller Noise Simulation {#13-dot-6-dot-1-integral-controller-noise-simulation} #### 13.6.2 Noise Simulation with Inverse Model Controller {#13-dot-6-dot-2-noise-simulation-with-inverse-model-controller} #### 13.6.3 Feedback Versus Feedforward Control {#13-dot-6-dot-3-feedback-versus-feedforward-control} ### 13.7 Practical Frequency Domain Noise Measurements {#13-dot-7-practical-frequency-domain-noise-measurements} #### 13.7.1 Preamplification {#13-dot-7-dot-1-preamplification} #### 13.7.2 Spectrum Estimation {#13-dot-7-dot-2-spectrum-estimation} #### 13.7.3 Direct Measurement of Position Noise {#13-dot-7-dot-3-direct-measurement-of-position-noise} #### 13.7.4 Measurement of the External Disturbance {#13-dot-7-dot-4-measurement-of-the-external-disturbance} ### 13.8 Experimental Demonstration {#13-dot-8-experimental-demonstration} ### 13.9 Time-Domain Noise Measurements {#13-dot-9-time-domain-noise-measurements} #### 13.9.1 Total Integrated Noise {#13-dot-9-dot-1-total-integrated-noise} #### 13.9.2 Estimating the Position Noise {#13-dot-9-dot-2-estimating-the-position-noise} #### 13.9.3 Practical Considerations {#13-dot-9-dot-3-practical-considerations} #### 13.9.4 Experimental Demonstration {#13-dot-9-dot-4-experimental-demonstration} ### 13.10 A Simple Method for Measuring the Resolution of Nanopositioning Systems {#13-dot-10-a-simple-method-for-measuring-the-resolution-of-nanopositioning-systems} ### 13.11 Techniques for Improving Resolution {#13-dot-11-techniques-for-improving-resolution} ### 13.12 Chapter Summary {#13-dot-12-chapter-summary} ### References {#references} ## Electrical Considerations {#electrical-considerations} ### Amplifier and Piezo electrical models {#amplifier-and-piezo-electrical-models} {{< figure src="/ox-hugo/fleming14_amplifier_model.png" caption="Figure 1: A voltage source \\(V\_s\\) driving a piezoelectric load. The actuator is modeled by a capacitance \\(C\_p\\) and strain-dependent voltage source \\(V\_p\\). The resistance \\(R\_s\\) is the output impedance and \\(L\\) the cable inductance." >}} Consider the electrical circuit shown in Figure [1](#orgc11b95b) where a voltage source is connected to a piezoelectric actuator. The actuator is modeled as a capacitance \\(C\_p\\) in series with a strain-dependent voltage source \\(V\_p\\). The resistance \\(R\_s\\) and inductance \\(L\\) are the source impedance and the cable inductance respectively.
Typical inductance of standard RG-58 coaxial cable is \\(250 nH/m\\). Typical value of \\(R\_s\\) is between \\(10\\) and \\(100 \Omega\\).
When considering the effects of both output impedance and cable inductance, the transfer function from source voltage \\(V\_s\\) to load voltage \\(V\_L\\) is second-order low pass filter: \begin{equation} \frac{V\_L(s)}{V\_s(s)} = \frac{1}{\frac{s^2}{\omega\_r^2} + 2 \xi \frac{s}{\omega\_r} + 1} \end{equation} with: - \\(\omega\_r = \frac{1}{\sqrt{L C\_p}}\\) - \\(\xi = \frac{R\_s \sqrt{L C\_p}}{2 L}\\) ### Amplifier small-signal Bandwidth {#amplifier-small-signal-bandwidth} The most obvious bandwidth limitation is the small-signal bandwidth of the amplifier. If the inductance \\(L\\) is neglected, the transfer function from source voltage \\(V\_s\\) to load voltage \\(V\_L\\) forms a first order filter with a cut-off frequency \begin{equation} \omega\_c = \frac{1}{R\_s C\_p} \end{equation} This is thus highly dependent of the load. The high capacitive impedance nature of piezoelectric loads introduces phase-lag into the feedback path. A rule of thumb is that closed-loop bandwidth cannot exceed one-tenth the cut-off frequency of the pole formed by the amplifier output impedance \\(R\_s\\) and load capacitance \\(C\_p\\) (see Table [1](#table--tab:piezo-limitation-Rs) for values).
Table 1: Bandwidth limitation due to \(R_s\)
| | Cp = 100 nF | Cp = 1 uF | Cp = 10 uF | |--------------|-------------|-----------|------------| | Rs = 1 Ohm | 1.6 MHz | 160 kHz | 16 kHz | | Rs = 10 Ohm | 160 kHz | 16 kHz | 1.6 kHz | | Rs = 100 Ohm | 16 kHz | 1.6 kHz | 160 Hz | The inductance \\(L\\) does also play a role in the amplifier bandwidth as it changes the resonance frequency. Ideally, low inductance cables should be used. It is however usually quite high compare to \\(\omega\_c\\) as shown in Table [2](#table--tab:piezo-limitation-L).
Table 2: Bandwidth limitation due to \(R_s\)
| | Cp = 100 nF | Cp = 1 uF | Cp = 10 uF | |-------------|-------------|-----------|------------| | L = 25 nH | 3.2 MHz | 1 MHz | 320 kHz | | L = 250 nH | 1 MHz | 320 kHz | 100 kHz | | L = 2500 nH | 320 kHz | 100 kHz | 32 kHz | ### Amplifier maximum slew rate {#amplifier-maximum-slew-rate} Further bandwidth restrictions are imposed by the maximum **slew rate** of the amplifier. This is the maximum rate at which the output voltage can change and is usually expressed in \\(V/\mu s\\). For sinusoidal signals, the amplifiers slew rate must exceed: \\[ SR\_{\text{sin}} > V\_{p-p} \pi f \\] where \\(V\_{p-p}\\) is the peak to peak voltage and \\(f\\) is the frequency.
If a 300kHz sine wave is to be reproduced with an amplitude of 10V, the required slew rate is \\(\approx 20 V/\mu s\\).
When dealing with capacitive loads, **the current limit is usually exceed well before the slew rate limit**. ### Current and Power Limitations {#current-and-power-limitations} When driving the actuator off-resonance, the current delivered to a piezoelectric actuator is approximately: \\[ I\_L(s) = V\_L(s) C\_p s \\] For sinusoidal signals, the maximum positive and negative current is equal to: \\[ I\_L^\text{max} = V\_{p-p} \pi f C\_p \\]
Table 3: Minimum current requirements for a 10V sinusoid
| | Cp = 100 nF | Cp = 1 uF | Cp = 10 uF | |-------------|-------------|-----------|------------| | f = 30 Hz | 0.19 mA | 1.9 mA | 19 mA | | f = 3 kHz | 19 mA | 190 mA | 1.9 A | | f = 300 kHz | 1.9 A | 19 A | 190 A | ### Chapter Summary {#chapter-summary} The bandwidth limitations of standard piezoelectric drives were identified as: - High output impedance - The presence of a ple in the voltage-feedback loop due to output impedance and load capacitance - Insufficient current capacity due to power dissipation - High cable and connector inductance ### References {#references} ## Bibliography {#bibliography} Fleming, Andrew J., and Kam K. Leang. 2014. _Design, Modeling and Control of Nanopositioning Systems_. Advances in Industrial Control. Springer International Publishing. .