Multipurpose Manipulator Research Articles

Properties of boron layers deposited during boronisations in W7-X

Boronisation was first used for wall conditioning in W7-X during the OP 1.2b operational period, which was characterized by the use of the fine-grain graphite Test Divertor Unit (TDU) and inertial cooling only. After this period, deposited layers were observed on all inner surfaces. Deposited layers were analyzed on 21 inner wall tiles using ion beam analysis methods, the deposited layers consisted mostly of boron with additional carbon and oxygen. During the operational period OP2.1 with an actively water cooled divertor made of carbon fiber reinforced carbon, different materials were exposed during two individual boronisations using the multi-purpose manipulator. Deposited boronisation layers on the samples were analyzed using nuclear reaction analysis. The deposited layer thicknesses showed some variation depending on substrate material and surface roughness, but a systematic dependence on material and/or roughness was not observed. Under the typical boronisation conditions at W7-X, one A × h (Ampere times hour) of boronisation results in a boronisation layer with a thickness of about 30 ± 15 × 1015B-atoms/cm2 (about 3 ± 1.5 nm) at the position of the multi-purpose manipulator. The oxygen gettering capacity of the layers is up to 0.5 – 0.9O/B.

Lightweight Multipurpose Three-Arm Aerial Manipulator Systems for UAV Adaptive Leveling after Landing and Overhead Docking

In aerial manipulation, the position and size of a manipulator attached to an aerial robot defines its workspace relative to the robot. However, the working region of a multipurpose robot is determined by its task and is not always predictable prior to deployment. In this paper, the development of a multipurpose manipulator design for a three-armed UAV with a large workspace around its airframe is proposed. The manipulator is designed to be lightweight and slim in order to not disrupt the UAV during in-flight manipulator movements. In the experiments, we demonstrate various advanced and critical tasks required of an aerial robot when deployed in a remote environment, focusing on the landing and docking tasks, which is accomplished using a single manipulator system.

Reciprocating probe measurements in the test divertor operation phase of Wendelstein 7-X

Reciprocating probes are a classic and widespread tool for the investigation of the edge and Scrape-Off Layer of magnetic fusion plasmas. In the Wendelstein 7-X (W7-X) stellarator, the Multi-Purpose Manipulator serves as a multi-user platform for probe measurements of various kinds. This paper presents a review on reciprocating probe operation during the first operation phase of W7-X with a test divertor (2017–2018). It gives an overview of the diverse zoo of probe heads and presents lessons learned about probe operation in complex magnetic geometries, operation safety, and probe head design. A few examples of probe measurements with a focus on unexpected observations are presented, e.g. indications for supra-thermal electrons and the propagation of plasma perturbations due to biased probes.

A multipurpose mobile manipulator for autonomous firefighting and construction of outdoor structures

This paper describes the implementation of a multipurpose, autonomous, mobile manipulator for building outdoor structures and for firefighting. Such a system finds applications in different industrial automation, manufacturing, and civil-construction scenarios as well as in search-and-rescue operations. This system was developed for the Mohamed Bin Zayed International Robotics Challenge (MBZIRC) 2020, showcasing once again the role of major scientific competitions in advancing the state of the art and exploring solutions to open problems. The paper presents in detail the hardware and software architectures of the developed mobile manipulator, while proposing methods for: a) Building outdoor structures consisting of heterogeneous brick patterns, and b) Entering buildings to locate and extinguish fires. Solutions were successfully deployed in the near-realistic arenas of the MBZIRC 2020 competition and resulted in the first-place award for the firefighting scenario.

Special Issue on New Technologies for Robotic Manipulators and Their Industrial Applications

The industrial robot is more precisely an “automatically controlled, reprogrammable, multipurpose manipulator, programmable in three or more axes, which can be either fixed in place or mobile” (ISO 8373:2012). According to the International Federation of Robotics, by 2018, more than 400,000 new units were being installed annually, and the global average robot density in the manufacturing industry was 99 robots per 10,000 employees. More than 30% of all installed robots were in the automotive industry, the biggest customer for robots. Research on measuring and calibrating, modeling, programming and controlling, and integrating systems has been conducted to give robotic manipulators a wider variety of industrial applications. This special issue covers technical and academic efforts related to new technologies that improve the accuracy and facilitate the implementation of robotic manipulators in industrial applications. The first paper, by Ibaraki et al., outlines technical issues and future research directions for the implementation of model-based numerical compensation schemes for industrial robots. The random forest method is used by Kato et al. to construct a calibration model for positioning errors and identify industrial robots’ positioning errors. A procedure for the quasi-static compliance calibration of serial articulated industrial manipulators is proposed by Theissen et al. A review of the kinematic modeling theory and a derived algorithm to identify error sources for a six-axis industrial robot are presented by Alam et al. Nagao et al. derive a forward kinematics model and identify the kinematics parameters for the calibration of a robot-type machine tool. A novel trajectory generation algorithm, including a corner smoothing method for high-speed and high-accuracy machining by industrial robots, is proposed by Tajima et al. Sato et al. study the vibration characteristics of an industrial robot and derive a mathematical model that represents the dynamic behavior of the system. In the context of smart manufacturing, a multilayer quality inspection framework including a measurement instrument and a robot manipulator is introduced by Azamfirei et al. To support mass customization and the development of reconfigurable manufacturing systems, Inoue et al. propose an autonomous mobile robotic manipulator. Yonemoto and Suwa present an adaptive manipulation procedure to establish an automated scheduling technique that flexibly responds to unforeseen events, such as machine failures. Sasatake et al. introduce a learning system that is based on a method for calculating the similarity between tools, and they test it on a robot system for doing housework. Finally, for better knowledge of the key challenges that manufacturers experience in implementing collaborative industrial robots, an industrial survey is conducted by Andersson et al. The editors sincerely appreciate the contributions of all the authors as well as the work of the reviewers. We are confident that this special issue will further encourage research and engineering work to increase our understanding and knowledge of robotic manipulators and their industrial applications.

Effectiveness of local methane and hydrogen injection into the scrape-off layer of W7-X by means of the multi-purpose manipulator

The Multi-Purpose-Manipulator (MPM) situated at the outboard mid-plane is a versatile carrier system for diagnostic probes at Wendelstein 7-X (W7-X). It is able to probe into the last scrape-off (SOL) layer close to the last closed flux surface. The manipulator is also has the capability to puff gas for well-localized fueling/impurity seeding into the SOL. In the previous operational campaign of OP 1.2a and 1.2b both hydrogen and methane were injected from the manipulator mounted probes. The effect of hydrogen puffing on the main plasma was observed to be much stronger than that of the methane puffing. This difference is related to the difference in ionization lengths between the two gas species. To support this assumption a puffing of a similar amount of methane and hydrogen was modelled with ERO.

Dynamics and dependencies of the configuration-dependent 1–2 kHz fluctuation in W7-X

• A 1–2 kHz fluctuation observed in W7-X is studied using cameras, probes, and magnetic coils. • The fluctuation appears to rotate poloidally in the E × B direction between 1 and 10 km/s. • The strength of the fluctuation depends on several plasma and machine parameters. A 1–2 kHz electromagnetic mode is present in a large fraction of W7-X discharges in the standard magnetic field configurations with 5/5 edge island structure. The power in the mode is significantly reduced in other magnetic configurations. The mode can appear spontaneously and persist for the full duration of a discharge. Its full width at half maximum is typically 100–300 Hz. The 1–2 kHz mode was first observed in visible light emissions from the divertor [1] . Matching spectral peaks were found in measurements of both global and edge plasma parameters, including line-integrated density, diamagnetic energy, and edge floating potential and ion saturation current [2] . An infrared camera recording shows a temperature modulation of ~ 2.5 K due to this mode on a divertor tile where the average temperature was 600 °C. Separate correlation analyses of the high-speed camera recordings, Langmuir probe signals, and Mirnov coil signals all indicate a poloidal velocity of 0.5–10 km/s and m = 2 as a likely poloidal mode number. Langmuir probes mounted on the Multi-Purpose Manipulator show that the fluctuation is present in one of the magnetic islands over a radial distance of at least 5 mm. A database of various diagnostic measurements and dB/dt signals from a Mirnov coil was created using a majority of the discharges from the 2018 campaign on W7-X, in order to shed light on the plasma parameters that are correlated with the existence of the 1–2 kHz mode. The power in the mode is positively correlated to the toroidal current, total external heating power, and core electron temperature. It is negatively correlated with plasma density.

Energy-and-pitch-angle-resolved escaping beam ion measurements by Faraday-cup-based fast-ion loss detector in Wendelstein 7-X

With the objective of understanding the energetic-particle loss mechanism in three-dimensional plasmas, a Faraday-cup-based fast-ion loss detector (FILD) was developed and installed in OP1.2b in Wendelstein 7-X (W7-X) as a collaboration between the National Institute for Fusion Science and Max-Planck-Institute for Plasma Physics. The FILD, which consists of double apertures and thin aluminum foils, was based on a magnetic spectrometer using the magnetic field of the fusion device. The double aperture limits the thermal ion, but allows the energetic ion to enter the FILD box. The thin aluminum foils serve as the ion collector. Orbit-following calculations were performed in order to find a suitable position for the FILD. The results indicated that barely co- and counter-going transit ions reached the FILD position mounted on the multi-purpose manipulator installed on W7-X. Moreover, because the injection angle of neutral beams injector installed on W7-X was relatively perpendicular, the target range of pitch angle was set to from 91 degrees to 150 degrees. An energy-and-pitch-angle map was created using a grid calculation code in order to decide on the position/size of aperture and aluminum foil. The grid calculation code indicates the position where the energetic ion would strike on the aluminum foil. Here, the map was used as the basis for designing an aluminum foil pattern with two energies and four pitch angle ranges. Also, note that the lower energy range was designed so that it accommodates a neutral beam injection energy of 55 kV. Measurements of beam ion losses were performed in neutral beam (NB) blip experiments, where concurrent increases and decreases of barely co-going transit beam ion losses due to NB injections were observed. Furthermore, this study validated that the FILD installed on a midplane manipulator probe is capable of probing a range of radii spanning 1.0–1.5 cm, over which the beam ion loss current would vary significantly.

Operation of probe heads on the Multi-Purpose-Manipulator at W7-X in OP 1.2a

The Multi-Purpose-Manipulator (MPM) has been operated, as a versatile carrier system for probes, since the first campaign OP. 1.1 in 2015 at Wendelstein 7X. The MPM is mounted at the outboard midplane and is able to perform fast plunges through the entire scrape off layer up to the last closed flux surface. In addition, a system for gas injection was commissioned that allowed the use of a dedicated probe head and a port on the existing probes for fueling and impurity seeding experiments. A combined probe, a combination of Langmuir, Mach and magnetic probes, was used. For the second campaign OP. 1.2a in 2017, with an island divertor, an upgraded combined probe, a fluctuation probe, a retarding field analyzer, a Mach probe array, a laser blow off target and a material probe holder were added to the range of plasma edge diagnostics. The new diagnostic probe heads were designed to address specific tasks, such as measuring the edge fluctuations, the ion temperature and the radial Mach number profiles. However, all fast plunging probes were designed such that they provide the most important quantities for SOL characterization (electron temperature, density, radial electric field).

A new multi-channel Mach probe measuring the radial ion flow velocity profile in the boundary plasma of the W7-X stellarator.

Ion flow velocity measurement in the edge and scraper-off layer region is beneficial to understand the confinement related phenomenon in fusion devices such as impurity transport and plays an important role in impurity control. During the Wendelstein 7-X (W7-X) operation phase 1.2a, a multi-channel (MC) Mach probe mounted on the multi-purpose manipulator has been used to measure radial profiles of edge ion flow velocity. This MC-Mach probe consists of two polar and two radial arrays of directional Langmuir pins (28 pins in total) serving for different aims, of which the polar arrays could obtain a polar distribution of ion saturation current, while the radial arrays can be used to study the dynamic process of a radially propagated event. In this paper, we report the observation of the radially outward propagation of a low frequency mode with a speed of around 200 m/s. The first measurement of the radial ion flow velocity profile using the MC-Mach probe in the boundary plasma of the W7-X with an island divertor will also be presented.

A horizontal powder injector for W7-X

Injection of low-Z powders into fusion plasma has been used to improve wall conditions, similar to the standard boronization process using diborane. Powder injection has the advantage of being much simpler, non-toxic, and efficient. The W7-X stellarator is planning on utilizing powder injection in long pulse discharges; a proof-of-principle test for horizontal injection into the plasma was conceived, a Probe Mounted Particle Injector (PMPI). The PMPI concept is developed using a polyetheretherketone (PEEK) paddle wheel hub that is driven by a piezo motor, due to the high magnetic fields, that rotates at 100 deg/s. This small PMPI fits into an envelope of 120 mm diameter × 150 mm long, a standard size for Multi-Purpose Manipulator (MPM). The device is housed in a carbon cup mounted on a retractable probe that can be placed near the plasma edge, enabling powder injection ˜4–8 cm radially into the boundary plasma. The feed for the paddle is via piezo electric actuator that vibrates a funnel filled with powder into a trough for the paddle to push. The 8 paddle arms, 35 mm long and 10 mm wide, are made from 0.38 mm thick PEEK which drag slightly along the powder-filled trough bottom, becoming a spring-loaded paddle which accelerates the powder upon release. Design challenges are the high ambient magnetic field, vacuum compatible materials, high temperature environment, limited rotary-drive options, and compact space. The design and testing of this new device will be presented.

Realization of Davidovits theory on pyramid construction using mobile laser robot

The truth behind the approach of building the Giza pyramids (Egypt) is still unknown. Many postulates were proposed. The theory of Professor Joseph Davidovits indicating that the pyramids were “assembled” in place by heating the mud is noted in the past years. This was proven by the identified amount of water found in the test of the nanoparticles. The advantage of such approach is bypassing the mobility and weight issues of the stones. In this paper we offer a simulation of the construction process using multipurpose robotic manipulators. The role of this mechanism is to inject mud and heat it using LASER technology

Plasma exposures of a high-conductivity graphitic foam for plasma facing components

The plasma-surface interactions from samples of high-conductivity graphitic foam biased to 120 V and placed in 6–8 eV deuterium plasmas with densities as high as 1019 m−3 were investigated at the PSI-2 linear plasma device in Jülich. Graphitic foam-plasma interactions were also studied at the Wendelstein 7-X (W7-X) stellarator in Greifswald by exposure to hydrogen and helium plasmas using the Jülich multi-purpose manipulator. The purpose was to explore the possibility of using the material in a plasma facing component, and initial results were encouraging. In W7-X, no measurable erosion or cracking was observed. The PSI-2 samples received a deuterium fluence of 5 × 1025 m−2 resulting in an average erosion of 43 µm or about 5 mg per sample. Residual gas analysis (RGA) data were acquired to monitor sample outgassing. Laser-induced Breakdown Spectroscopy (LIBS) was used to measure deuterium retention in the porous foam. After exposure, the surfaces were characterized with scanning electron microscopy, energy dispersive x-ray analysis and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The graphitic foam has a thermal conductivity as high as 287 W/mK and is considered as a replacement to more exotic carbon fiber composites such as SepCarb NB31 or isotropic graphites like ATJ that are no longer produced but used in present-day tokamak experiments. Actively cooled monoblocks were made from the foam and underwent extensive materials characterization including infrared response studies at Oak Ridge National Laboratory. This material is under consideration for the proposed actively-cooled W7-X divertor scraper element.

Characteristics of the SOL turbulence structure in the first experimental campaign on W7-X with limiter configuration

In the first experimental campaign of Wendelstein 7-X (W7-X), a combined probe head mounted on the multi-purpose manipulator has been used to measure the scrape-off layer (SOL) turbulence characteristics. The preliminary experimental results are summarized to illustrate the SOL turbulence properties in the limiter configuration on W7-X. In a standard limiter configuration, significant electrostatic fluctuations can be found in the near SOL, and the dominant frequency of fluctuation power is below 100 kHz. The auto-correlation spectrum power law decay factor is α ≈ −1 below 40 kHz and α ≈ –2 between 50 and 200 kHz. A broadband spectrum appears between 240 and 380 kHz with a low spectral power density, but a high cross-correlation coefficient. The statistical characteristics of turbulence are calculated by the two-point cross-correlation technique. A clear poloidal dispersion relation is found in the spectrum S(kθ, f), propagating along the ion diamagnetic drift direction with a group velocity (below 100 kHz) about 0.56 km/s in the near SOL in the laboratory frame. The poloidal correlation length is around 5–10 mm in SOL. The turbulence phase velocity is about 0.5–1 km/s when close to the last closed flux surface, which is comparable with the poloidal E × B drift speed.

Design of a High Resolution Probe Head for Electromagnetic Turbulence Investigations in W7-X

An insertable probe head called high resolution probe (HRP) has been developed at Consorzio reversed field experiment in the framework of the EUROfusion S1 work program and in collaboration with IPP Greifswald, to study the electrostatic and electromagnetic features of turbulence in the edge region of Wendelstein 7-X using the multipurpose manipulator. This paper reports the design development of the HRP diagnostic head, from the choice of the sensors to the engineering design. The assumptions and evaluations supporting the main design choices, together with the R&D tests carried out to check the most critical parts, are described in detail.

Observations of the effects of magnetic topology on the SOL characteristics of an electromagnetic coherent mode in the first experimental campaign of W7-X

Turbulence is considered to play an important role in the edge cross field heat and particle transport in fusion devices. Scrape-off layer (SOL) turbulence characteristics were measured by the combined probe mounted on the multi-purpose manipulator during the first experimental campaign of W7-X. An electromagnetic coherent mode (EMCM) at 7 kHz has been observed by multiple diagnostics in both the plasma core and the SOL and exhibits a strong dependence of the magnetic topology. As demonstrated by the measurements of the combined probe, the EMCM starts to appear at a radius of R = 6.15 m along the path of probe measurement and this location is shifted inwards in higher iota configurations. It propagates along the direction of electron diamagnetic drift in the far SOL with a poloidal velocity about 0.6 km s−1 while it turns to the opposite direction gradually in the near SOL in the laboratory frame, but keeps a velocity of about 0.6–0.7 km s−1 along the direction of electron diamagnetic drift in the plasma frame. This mode can be induced by raising the ECRH heating power in similar discharge conditions, which is probably linked to the gradient of electron temperature and pressure. The EMCM is enhanced significantly in the edge magnetic island with long connection length where the EMCM can grow up due to the long particle confinement time.

Measurement of the plasma edge profiles using the combined probe on W7-X

Wendelstein 7-X (W7-X), started operation in December 2015 with a limiter configuration. In conjunction with the multi-purpose manipulator, a carrier for fast reciprocating probe systems, the combined probe has been installed. This combined probe is able to measure the local electron temperatures and densities, magnetic field, the electric field and the plasma flow. These parameters are very useful in ascertaining the edge plasma perfomance. In addition, the field line tracing feature of the W7-X webservices was used to calculate the connection length along the path of the probe, for each configuration.

A PCS7-based control and safety system for operation of the W7-X Multi-Purpose Manipulator facility

The Multi-Purpose Manipulator (MPM) for Wendelstein 7-X, at the Max-Planck-Institute for Plasma Physics in Greifswald (MPIPP), is used to transport electrical probes and targets to the edge of the inner vessel. It is a lock system, which is attached to the outer port in the equatorial plane of the cryostat vessel. At the parking position, the tip of the probe coincides with the inner vessel wall; a fully controlled movement into the edge plasma for all magnetic field configurations is feasible. The whole functionality of the MPM system is maintained by a distributed control system (DCS) based on Siemens PCS7, which is the recommended standard for machine and diagnostic control at W7-X. Beside standard scenarios like target exchange and generation of ultra-high vacuum conditions a high variety of parameter selections for stroke depth, velocity or acceleration is selectable in the sequence control system within safety limits. A sophisticated error handling facilitates a reliable remotely controlled operation without manual access over longer periods.

Diagnostic set-up and modelling for investigation of synergy between 3D edge physics and plasma-wall interactions on Wendelstein 7-X

A group of edge diagnostics and modelling has been developed for investigation of synergy between 3D edge physics and plasma-wall interactions on Wendelstein 7-X (W7-X). Two endoscopes have been designed for visible and ultraviolet spectroscopy and tomography of the plasma edge, along with infrared thermography of the divertor tiles. 2D profiles of impurities (e.g. helium, carbon) will be measured by two endoscopes viewing the island divertor region in the plasma edge with a spatial resolution of <2 mm. A multipurpose manipulator, which is used as the carrier either of the probe head for measuring the plasma edge profiles or of samples for plasma exposure studies, was installed at the outside mid-plane on W7-X in 2015. A poloidal correlation reflectometer has also been installed at W7-X. The system consists of an antenna array observing the propagation of turbulent phenomena in the mid-plane. The EMC3-EIRENE code package has been adapted for plasma edge transport in helium plasma at W7-X using a hybrid fluid–kinetic approach by enabling EMC3 to treat non-hydrogen isotopes and extending the usage of EIRENE features within EMC3-EIRENE.

A multi-purpose manipulator system for W7-X as user facility for plasma edge investigation

The investigation of edge plasmas at the stellarator W7-X requires a flexible tool for integration of a variety of different diagnostics as e.g. electrical probes, probing magnetic coils, material collection, or material exposition probes, and gas injection. A multi-purpose manipulator (MPM) system has been developed and attached to the W7-X vessel before the operational phase 1.1. The system was designed as user facility for many diagnostics, which can be mounted on a unique interface without breaking the W7-X vacuum. The manipulator system, located in the equatorial plane, transports the inserted diagnostic probe to the edge of the inner vacuum vessel. From there, the probe can be moved over a maximum distance of 350mm to different positions inside the plasma with a maximum acceleration and deceleration of 30m/s2. Acceleration, speed, and stroke depth are individually adjustable and programmable by a PLC system within predetermined limits. The MPM system can be equipped with multifunctional probes and is prepared for cooling/heating of the probe head, gas injection, and a flexible setting of the electrical diagnostic. In the paper, the MPM components, their functionalities, and the interface to the probe head are described. The scope of physical parameters is presented for the development of diagnostic probes applicable in the MPM user facility. This also includes the operational parameters for the movements and the electrical environment for measurements. The operation of the MPM during the OP1.1 is demonstrated on the application of a multipurpose probe head, including electric, magnetic, and thermal probes.