Integrated Design and Control of Flexure-Based Nanopositioning Systems — Part I: Methodology

TLDR: In this article, the authors present an integrated design and control method for implementing flexure-based nanopositioning systems, where an automation engine generates a set of flexurebased design topologies and also controllers of varying order in the optimization.

About: This article is published in IFAC Proceedings Volumes.The article was published on 2011-01-01 and is currently open access. It has received 1 citations till now. The article focuses on the topics: Integrated design & Automation.

Figures

Table 1. All possible cases for integrated design and control.

Fig. 2. Design for control example from [35] modifying actuator design to eliminate translational loading in voice-coil motors. (a) In disk drives, the actuator for the read/write head is a typical lorentz-force voice coil motor that produces a force at an offset. The force also excites the translational mode of the bearing. (b) A novel design for the voice coil motor, based on a magnetic array called as Hallbach array, which is commonly found in linear motors, is used in a rotary configuration to produce a unidirectional magnetic field in the hub. (c) The resulting actuator is a pure torque motor that minimizes the effect of the translational mode of the bearing.

Fig. 1. Schematic diagram showing a positioning system example. The goal is to vary the gap z over a large range of motion and control bandwidth.

Fig. 2. Design for control example from [35] modifying actuator design to eliminate translational loading in voice-coil motors. (a) In disk drives, the actuator for the read/write head is a typical lorentz-force voice coil motor that produces a force at an offset. The force also excites the translational mode of the bearing. (b) A novel design for the voice coil motor, based on a magnetic array called as Hallbach array, which is commonly found in linear motors, is used in a rotary configuration to produce a unidirectional magnetic field in the hub. (c) The resulting actuator is a pure torque motor that minimizes the effect of the translational mode of the bearing.

Fig. 10. Lumped parameter model for depicting dynamic behavior of topology concepts using flexure-based mechanisms of Fig. 5(g)-(j) as pivots in the 1-DOF positioning system.

Fig. 4. Integrated design and control methodology for meeting performance requirements.

Frequently asked questions

Q1. What have the authors contributed in "Integrated design and control of flexure-based nanopositioning systems - part i: methodology" ?

In this paper, the authors present an integrated design and control method for implementing flexurebased nanopositioning systems. The authors discuss the need for varying design topology and order of a controller in design and control optimization. This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Research Laboratories, Inc. ; an acknowledgment of the authors and individual contributions to the work ; and all applicable portions of the copyright notice. 

Q2. What are the future works in "Integrated design and control of flexure-based nanopositioning systems - part i: methodology" ?

The details of the controller parameterization are not covered here and will be part of a future paper from their group. 

Q3. What is the main reason for the characterization of the design and control parameters?

Since unmodeled dynamics in the control bandwidth can adversely affect the performance, it is necessary to account for model-truncation errors in the design and control optimization. 

Q4. What is the way to generate a library of design topologies?

Once the building blocks are generated, a library of design topologies can be generated by using the building block as an implementation of the constraints (following a constraint-based synthesis approach [29]) for satisfying the necessary kinematics. 

Q5. What are the advantages of flexure-based mechanisms?

Flexure-based mechanisms are composed of slender beam-like spring elements in their mechanical design; they are close to being ideal motion bearings with minimal friction, backlash, and other uncertainties. 

Q6. What is the common type of damping in flexures?

Physical damping is low in flexures made from metals such as aluminium (used in development stages of the design process for ease of machining), or titanium (used in the implementation and testing phase because of its high fatigue strength and other material properties). 

Q7. What is the way to achieve the desired closed-loop control performance?

A common systems-based methodology can facilitate developing valuable synthesis tools for achieving the desired closed-loop control performance. 

Q8. What is the way to solve the varying design topology problem?

since the number of possible design configurations in typical nanopositioning system applications are finite, the varying design topology problem can be broken down into a number of fixed design (each tested with a controller of varying order) problems. 

Q9. What is the effect of moving the actuation point closer to the sensor?

With the actuation location moved closer to the end-point, the portion of the link from the new actuation point to the sensor location is shorter, and hence stiffer. 

Q10. What are some of the applications for nanopositioning?

Many applications for nanopositioning systems have emerged over the past few decades in various contexts, such as semiconductor manufacturing, metrology, x-ray crystallography, and biological imaging. 

Q11. What are the possible operations that can be used to generate a design library?

These operations could be, for example, a parallel or serial replication, or a geometrical transformation, or adding a redundant constraint that imparts symmetry. 

Q12. What is the effect of the change in the topology?

It is shown in [36] that, under certain geometry conditions, this topology change results in moving the zeros from the real-axis on to the imaginary axis, making the system minimum-phase. 

Q13. How can the actuation point be moved away from the motor?

In order to avoid the occurrence of the non-minimum phase zero, the actuation point shown in Fig. 1 (a) can be moved away from the motor closer to the end-point, as shown in Fig. 1(b). 

Q14. What is the simplest way to change the topology of a robot?

Without this topology change, with the actuator just as the motor and sensor at the end-point, the system would be non-minimum phase and pose critical control challenges.