This article presents a metrology platform (MP) as high precision endeffector of a robot with a tailored disturbance rejection scheme in order to enable high-resolution measurements directly in a production line. The MP is installed on a gantry robot for in-plane positioning and has an electromagnetic actuator for vertically positioning its mover. It can mount a compact measurement tool for high precision topography measurements, which are typically sensitive to external vibrations, introducing relative motion between the measurement tool and the sample. To compensate these vibrations, the MP mover vertically tracks the sample by feedback control, maintaining a constant distance between sample and measurement tool. In order to reject broad-band floor vibrations as well as narrow-band vibrations, revealed by the analysis and introduced by the robots servo control, the designed high-bandwidth proportional-integral differential based controller is supplemented by peak filters tailored to the narrow-band vibration components. A method for designing these peak filters depending on the location of the narrow-band disturbance relative to the crossover frequency is presented. The resulting controller enables a tracking error as small as 15 nm (rms), which is 50% smaller than the error without the peak filters, demonstrating the effectiveness of the MP in enabling high-resolution inline measurements.

High precision inline measurement systems are considered one of the most important preconditions for future production, as they are a key technology to fulfill the increasing demands on quality, productivity and flexibility. To provide the required positioning uncertainty, which is typically limited by the precision of the industrial robot and external vibrations, a measurement platform for fine positioning of the tactile or optical sensing system is developed. Due to their non-contacting measurement principles, their high measurement rates and resolution, optical sensing principles are well suited for inline measurement applications. To advance single-point optical sensors to 3D measurement tools, fast steering mirrors (FSMs) are proposed to manipulate only the optical path of the sensor. This requires an integrated system design that considers all subsystems, components and the target application from the very beginning, in order to maximize system performance. In this contribution the integrated design approach is demonstrated along the FSM and controller design tailored for raster and Lissajous trajectories and their integration into a scanning optical sensor system.

Structural modes such as decoupling of a mechanical subsystem are in general unwanted effects in high precision positioning systems. This paper introduces intentional decoupling as a design choice by using a connecting flexure-damper configuration that allows high bandwidth control of a stiff first subsystem and lower bandwidth control of a bulky second subsystem at the same time. An experimental setup of a single degree of freedom system with one body intentionally decoupling above 190 Hz is developed and analyzed, showing good agreement with the analytical modeling. A model-based H$_\infty$-controller to actively control the position of the first body is designed and the damping in the system is revealed as an important design parameter to reduce the control effort around the decoupling frequency. It is demonstrated that with the derived controller, the first and the second body of the resulting prototype can simultaneously be controlled with bandwidths of 1.4 kHz and 180 Hz, respectively. When exposed to a disturbance profile with 12.4 $\mu$m root mean square (rms) value in the laboratory environment, the remaining rms positioning errors for the actively and passively controlled subsystems are as small as 0.12 $\mu$m and 0.81 $\mu$m, respectively.

Für effektive und adaptierbare Produktionssysteme der Zukunft stellen flexible roboterbasierte Messsysteme eine der wichtigsten Voraussetzungen dar, um die entsprechenden Anforderungen an Qualität, Produktivität und Flexibilität erfüllen zu können. Da Bewegungsunsicherheit industrieller Roboter und externe Vibrationen in Produktionsumgebungen Messungen im Mikro- bis Nanometerbereich beeinträchtigen, wird ein dual aktuierter Ansatz mit einer Messplattform, welche die Feinpositionierung des taktilen oder optischen Messsystems übernimmt, vorgeschlagen. Um Interaktionen von Messsystem und Objekt zu vermeiden, sind optische Sensoren aufgrund ihrer berührungslosen Messprinzipien sowie hohen Messraten und Auflösungen für In-Prozess-Messanwendungen besonders gut geeignet. Zur Erweiterung solcher punktweise messenden Sensoren zu echten 3D-Messsystemen werden diese mit opto-mechatronischen Kippspiegelsystemen kombiniert. Dabei wird ein integrierter Systementwurf verwendet, der alle Teilsysteme bis hin zu Ziel-Applikation von Anfang an berücksichtigt, um die Präzision und Messrate zu maximieren. Dieser Beitrag demonstriert einen solchen integrierten Ansatz am Beispiel von Kippspiegel- und Reglerentwürfen, zugeschnitten auf Raster- und Lissajous-Trajektorien, und deren Integration mit optischen Sensorsystemen.

Mechanical vibrations and precision of conventional positioning systems are limiting factors for using nano-metrology tools directly in production environments. Vibrations cause relative motion between workpiece and inspection tool, which distorts measurements at the nanometer level. To enable robot based in-line nano-metrology, this paper proposes a metrology platform that is mounted on a robot arm and maintains a constant and precise relative distance to the workpiece by means of a control loop. This paper presents the mechatronic system design of a 1 degree of freedom (DoF) metrology platform for tracking a vibrating sample in the sub-nanometer range. By incorporating control relevant requirements in the mechanical and electrical design, which is supported by a dynamic error budgeting analysis, the implementation of a high bandwidth feedback loop is enabled. The metrology platform consists of a 1 DoF Lorentz actuator with gravity compensator, a low stiffness flexure-based guiding mechanism and a moving mass of 4 kg with high structural resonance frequencies. A high-bandwidth PD based controller that utilizes the signal of an interferometer is implemented for feedback control. Experiments show a tracking error of 4 nm RMS when exposing the sample under test to on-site measured vibrations, which complies with the dynamic error budgeting analysis. This demonstrates viability of the implemented mechatronic design for in-line metrology applications requiring sub-nanometer precision. (C) 2017 Elsevier Ltd. All rights reserved.

A six degree of freedom, magnetically levitated metrology platform is proposed and implemented to enable nano-scale measurements directly in a production environment by providing vibration isolation. The metrology platform maintains a constant distance between sample and nano-metrology tool, forming a nano-scale laboratory environment directly in the production line. This paper presents the design of the proposed metrology platform. Tracking of the sample is achieved by using six position sensors, a six degree of freedom actuator and feedback control. Experimental results demonstrate positioning of the platform in six degrees of freedom at a bandwidth of 35 Hz in the translational directions and at a bandwidth of more than 15 Hz in the rotational directions, respectively. This results in a tracking error that is smaller than 50 nm rms. This paper denotes the first successful attempt for six degree of freedom vibration isolation to enable in-line nano-metrology.

Measuring properties at the nanometre scale such as topography, morphology and roughness within a production line becomes increasingly important for quality control and process monitoring tasks. In a production line, ground vibrations are transmitted to the sample and the inspection tool, corrupting nanoscale measurements by affecting the distance between inspection tool and sample. To enable nanometre scale measurements a mechanism is needed that keeps this distance constant. This paper describes the concept and experimental results of a metrology platform that tracks the sample for nanoscale inspection. The nano inspection tool is carried by the metrology platform and is artificially coupled to the movement of the sample by using a feedback controller. A one degree of freedom experimental setup was built for demonstrating tracking performance. The implemented closed loop control achieves disturbance rejection with a bandwidth of 410 Hz and reduces emulated on-site vibrations from ±500 nm down to ±9 nm, showing significant reduction of external vibrations. Active vibration isolation, Nanometrology, Mechatronic system design, High precision measurement

Structural modes as for example decoupling of a mechanical subsystem are in general unwanted effects in high precision positioning systems. This paper proposes a well designed decoupling mechanism as a design choice to improve the energy efficiency of an active vibration isolation system that needs to position a structure comprising a high and low precision subsystem. Experimental setups of a single DoF system with a rigid and a decoupling mechanical system structure are developed and analyzed. PD and a PID controllers are designed for the rigid and the equivalent decoupling structure, respectively, resulting in the same disturbance rejection performance for the high precision subsystem. Experiments demonstrate that disturbances of 12.4 µm rms amplitude are reduced to below 118 nm rms for both systems and that the rms energy consumption of the decoupling structure can be reduced by 68% as compared to the rigid system structure.

Mechanical vibrations occuring in a production environment cause a relative motion between the sample and inspection tool that distorts measurements at the nanometcr level. To overcome this problem, this paper proposes a metrology platform that maintains a constant relative distance to the sample by means of an Hoofeedback controller. Experiments in one degree of freedom show that the metrology platform can reduce vibrations as they occur in a production environment by one order of magnitude. Therefore, it enables in-line surface metrology at the nanometcr level.

Zusammenfassung In einer Produktionsumgebung beeinflussen mechanische Vibrationen den Relativabstand zwischen Inspektionsgerät und Werkstück, was für Messungen im Nanometerbereich hinderlich ist. Dieser Beitrag stellt eine Metrologieplattform zur Montage eines Inspektionsgerätes vor, die mittels eines H∞-Reglers den Relativabstand zum Werkstück konstant hält. Ein Laboraufbau mit einem Freiheitsgrad zeigt, dass in der Produktionsumgebung vorkommende Vibrationen um eine Größenordnung reduziert werden können, was eine Oberflächencharakterisierung im Nanometerbereich direkt in der Produktion ermöglicht.

Precise distance measurement is crucial for the high-precision industry as the semiconductor manufacturing is one. Measurement devices based on the concept of a Michelson interferometer are widely used to implement a very accurate and non-contact distance measurement with nanometer resolution. Interferometers are often applied in environments where the optical path is uncovered and influenceable by air turbulences such as caused by fast moving targets. Air turbulences cause aberrations in the wavefront, deteriorate the interference pattern and lead to a smaller peak-to-valley intensity signal which cause problems in the determination of the traveling distance. To determine as well as to compensate for aberrated wavefronts this thesis investigates the integration of an adaptive optics system into a Michelson interferometer. The aberrated wavefront is measured with a Shack-Hartmann wavefront sensor and compensated by a deformable mirror. A feedback controller is implemented that computes the signals for the deformable mirror. The proposed setup comprises off-the-shelf products for the interferometer and the adaptive optics setup. The implemented system is capable of compensating low order aberrations, resulting in an average improvement of 5, 7 of the peak-to-valley signal.

Wavefront sensing is important in various optical measurement systems, particularly in the field of adaptive optics (AO). For AO systems, the sampling rate, as well as the latency time, of the wavefront sensors (WFSs) imposes a restriction on the overall achievable temporal resolution. In this paper, we propose a versatile Shack-Hartmann WFS based on an industrial smart camera for high-performance measurements of wavefront deformations, using a low-cost field-programmable gate array as the parallel processing platform. The proposed wavefront reconstruction adds a processing latency of only 740 ns for calculating wavefront characteristics from the pixel stream of the image sensor, providing great potential for demanding AO system designs.

Wavefront sensing is important in many optical measurement systems and adaptive optics. The speed of the wavefront sensor determines the achievable temporal resolution of dynamic measurements and the bandwidth of adaptive optics systems. In this paper we propose a versatile high-speed Shack-Hartmann wavefront sensor based on an industrial smart camera. The sensor uses a parallel processing scheme for high-speed measurement of wavefront deformations and offers runtime reconfiguration. An FPGA based centroid detection is presented, adding an overall time delay of only 380ns. The wavefront estimation is demonstrated on an external PC using zonal and modal reconstruction.