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A dual-interferometer-based angular measurement system is proposed and studied, obtaining analytical expressions for the measured distance of each interferometric axis. The nonzero convexity of the characteristic curve during a rotation is proven to be an intrinsic characteristic of the setup. An absolute angle recovery method is proposed relying on the use of this characteristic curve as an absolute reference to overcome the limitation of the relative operation of conventional interferometric systems. The recovery method is evaluated by Monte Carlo simulations, studying the effect of the noise and the number of points on the performance of the recovery. Finally, the technique is successfully applied to a high-precision rotational stage, where an independent dual-interferometer system is used to experimentally evaluate the performance of the method. The results show an accuracy of $\pm 1.29~\mu $ rad ( $3\sigma $ ) in the recovery of the angle, which is in agreement with the Monte Carlo simulations.

Piezoelectric actuators are candidates for use in radioactive environments but specific radiation tests are necessary to understand the radiation effects on the whole actuator assembly. The results of three irradiation tests on a piezoelectric actuator used for Crystal Collimation are presented. The total ionising dose effects are studied with two Gamma (60Co) Tests up to 10 MGy and 1 MGy, whereas the displacement damage effects are studied in a Proton Test up to 2 MGy and 1.14 × 1016 p/cm2 fluence. The main results are summarised for each test, presenting a maximum impedance increase of less than 25% (Proton Test), a maximum free stroke reduction of less than 25% (Proton Test) and a variation in the shape of the hysteresis response of the actuator.

Planar channeling in bent crystals has been observed in LHC with multi-TeV proton beam in 2015. Two crystals, mounted on novel high-accuracy goniometers (one in the horizontal and one in the vertical plane), are integrated in the LHC collimation system, for studying the feasibility of the crystal-based collimation scheme. Using this experimental setup, tests with fully-stripped lead ion beams at both 450 Z and 6500 Z GeV were carried during dedicated LHC beam time. Planar channeling was observed for the first time with lead ions at these unprecedented energies surpassing by more than 1 order of magnitude the previous state-of-the-art for lead heavy ions and providing an important experimental basis for future applications of bent crystals in beam manipulations. The set of measurements performed to confirm this observation, as the local loss reduction in presence of channeling and the evidence of a deflected beam downstream of the crystal, are presented., peer-reviewed

Beam collimation in high-energy colliders is customarily carried out by means of massive amorphous absorbers surrounding the circulating beam. Several studies were performed in the last decades to establish an innovative collimation technique that relies on particle deflection by means of channeling between crystalline planes of a bent crystal. We report the operational use of crystal collimation in the Large Hadron Collider that was achieved during a special high-${\ensuremath{\beta}}^{\ensuremath{\ast}}$ physics run with low-intensity beams, representing a milestone for both accelerator and high-energy physics that could pave the way for new synergies in the near future. The deployment of this scheme was steered and motivated by machine-simulation studies, which were then confirmed experimentally using data provided by the experiments thanks to a sensitivity not accessible with the ring instrumentation. The evidence of beam-related experimental background reduction, improved data quality, and faster halo removal with respect to amorphous collimators is obtained using bent crystals as the primary collimation stage. A detailed description of preparatory studies and operational performance is reported, together with a comparison between experimental results and theoretical expectations.

The highly conserved, ubiquitous molecular chaperone Hsp90 is a key regulator of cellular proteostasis and environmental stress responses. In human pathogenic fungi, which kill more than 1.6 million patients each year worldwide, Hsp90 governs cellular morphogenesis, drug resistance, and virulence. Yet, our understanding of the regulatory mechanisms governing fungal Hsp90 function remains sparse. Post-translational modifications are powerful components of nature’s toolbox to regulate protein abundance and function. Phosphorylation in particular is critical in many cellular signaling pathways and errant phosphorylation can have dire consequences for the cell. In the case of Hsp90, phosphorylation affects its stability and governs its interactions with co-chaperones and clients. Thereby modulating the cell’s ability to cope with environmental stress. Candida albicans, one of the leading human fungal pathogens, causes ~750,000 life-threatening invasive infections worldwide with unacceptably high mortality rates. Yet, it remains unknown if and how Hsp90 phosphorylation affects C. albicans virulence traits. Here, we show that phosphorylation of Hsp90 is critical for expression of virulence traits. We combined proteomics, molecular evolution analyses and structural modeling with molecular biology to characterize the role of Hsp90 phosphorylation in this non-model pathogen. We demonstrated that phosphorylation negatively affects key virulence traits, such as the thermal stress response, morphogenesis, and drug susceptibility. Our results provide the first record of a specific Hsp90 phosphorylation site acting as modulator of fungal virulence. Post-translational modifications of Hsp90 could prove valuable in future exploitations as antifungal drug targets.

A rotatable-jaw collimator design was conceived as a solution to recover from catastrophic beam impacts which would damage a collimator at the Large Hadron Collider (LHC) or its High-Luminosity upgrade (HL-LHC). One such rotatable collimator prototype was designed and built at SLAC and delivered to CERN for tests with LHC-type circulating beams in the Super Proton Synchrotron (SPS). This was followed by destructive tests at the dedicated High Radiation to Materials (HiRadMat) facility to validate the design and rotation functionality. An overview of the collimator design, together with results from tests without and with beam are presented., peer-reviewed

In recent years the cost, size and complexity of use of interferometers have reduced to an extent where they are now more employable in industrial applications, where their high precision and contactless measurement benefits are needed. A limitation in many industrial interferometers, however, is the maximum target speed that can be tracked without loss of information. In this paper optical setups are proposed, analysed and compared. They allow the effective target speed seen by the interferometer to be reduced thereby extending their range of use.

Stepper motors are widely used in high precision positioning applications where reliability is an important factor. Field Oriented Control (FOC) can be used to damp the high-oscillatory dynamics of open-loop driven stepper motors and effectively reduce induced vibrations during motion. However, when it is required to hold a constant position, the induced vibrations can be higher in FOC than in open-loop control. To solve this, different techniques are proposed in this paper: i) a bump-less switch from FOC to open-loop control, ii) reducing the current reference to zero and iii) reducing the applied voltage to zero. Unlike other studies in vibration reduction techniques based on motion regimes and online feedback, the techniques presented here successfully reduce the vibrations in standstill and without the use of additional sensors. These methods are applied to a crystal collimator at CERN with good results and their performance is compared.

Beryllium is a material extensively used in various particle accelerator beam lines and target facilities, as beam windows and, to a lesser extent, as secondary particle production targets. With increasing beam intensities of future multimegawatt accelerator facilities, these components will have to withstand even greater thermal and mechanical loads during operation. As a result, it is critical to understand the beam-induced thermal shock limit of beryllium to help reliably operate these components without having to compromise particle production efficiency by limiting beam parameters. As part of the RaDIATE (radiation damage in accelerator target environments) Collaboration, an exploratory experiment to probe and investigate the thermomechanical response of several candidate beryllium grades was carried out at CERN’s HiRadMat facility, a user facility capable of delivering very-high-intensity proton beams to test accelerator components. Multiple arrays of thin beryllium disks of varying thicknesses and grades, as well as thicker cylinders, were exposed to increasing beam intensities to help identify any thermal shock failure threshold. Real-time experimental measurements and postirradiation examination studies provided data to compare the response of the various beryllium grades, as well as benchmark a recently developed beryllium Johnson-Cook strength model.

The HRMT27-RodTarg experiment employed the HiRadMat facility at CERN to impact intense 440 GeV proton beams onto thin rods 8 mm in diameter, 140 mm in length, and made of high-density materials such as Ir, W, Ta, Mo, and alloys. The purpose of the experiment was to reduce uncertainties on the CERN antiproton target material response and assess the material selection for its future redesign. The experiment was designed to recreate the extreme conditions reached in the production target, estimated in an increase of temperature above $2000\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ in less than $0.5\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$ and a subsequent compressive-to-tensile pressure wave of several gigapascals. The goals of the experiment were (i) to validate the hydrocode calculations used for the prediction of the antiproton target response and (ii) to identify limits and failure mechanisms of the materials of interest. In order to accomplish these objectives, the experiment relied on extensive instrumentation (pointing at the target rod surfaces). This paper presents a detailed description of the experiment as well as the recorded online results which showed that most of the investigated materials suffered internal damage from conditions 5--7 times below the ones present in the AD target. Tantalum, on the other hand, apparently withstood the most extreme conditions without presenting internal cracking.

The identification problem of the linear dynamic part of piezo based actuators is addressed in this paper, exploiting the use of binary signals, specifically the pseudo random binary sequences (PRBS). Due to the presence of nonlocal memory hysteretic behavior in piezoelectric active materials, the dependence of the identification results on this strongly nonlinear effect is analyzed and useful guidelines for the design of the PRBS stimulating signal are derived. Moreover, some properties of hysteresis like cancellation and congruency are experimentally analyzed and their effects on the identification process are discussed. Finally, the use of a hysteresis compensation strategy in the identification process is evaluated and discussed.

Piezoelectrics are the most commonly used of the multifunctional smart materials in industrial applications, because of their relatively low cost and ease of use in electric and electronic oriented applications. Nevertheless, while datasheets usually give just small signal quasi-static parameters, their full potential can only be exploited only if a full characterization is available because the maximum stroke or the higher piezo coupling coefficients are available at different electro-mechanical biases, where often small signal analysis is not valid. In this paper a method to get the quasi-static fully coupled characterization is presented. The method is tested on a commercial piezo actuator but can be extended to similar devices.

This study presents a further step within the ongoing R&D activities for the redesign of the CERN's Antiproton Decelerator Production Target (AD-Target). A first scaled target prototype, constituted of a sliced core made of ten Ta rods -8 mm diameter, 16 mm length- embedded in a compressed expanded graphite (EG) matrix, inserted in a 44 mm diameter Ti-6Al-4V container, has been built and tested under proton beam impacts at the CERN's HiRadMat facility, in the so called HRMT-42 experiment. This prototype has been designed following the lessons learned from previous numerical and experimental works (HRMT-27 experiment) aiming at answering the open questions left in these studies. Velocity data recorded on-line at the target periphery during the HRMT-42 experiment is presented, showing features of its dynamic response to proton beam impacts. Furthermore, x-ray and neutron tomographies of the target prototype after irradiation have been performed. These non-destructive techniques show the extensive plastic deformation of the Ta core, but suggest that the EG matrix can adapt to such deformation, which is a positive result. The neutron tomography successfully revealed the internal state of the tantalum core, showing the appearance of voids of several hundreds of micrometers, in particular in the downstream rods of the core. The possible origin of such voids is discussed while future microstructure analysis after the target opening will try to clarify their nature., 11 Pages, 12 figures

A new absolute angle recovery method for dual-interferometer-based rotational stages is presented. The high resolution of laser interferometers makes this sensor particularly suitable for high-precision rotational stages (comprising two parallel interferometer heads separated by a fixed distance). However the incremental operation of the sensor results in relative angle reference. The proposed method establishes an absolute angle reference system based on the characteristic movement of the rotational stage throughout the full angular range. The method is successfully applied in a high-precision rotational stage and its performance is evaluated with an external dual-interferometer system showing an accuracy of ±1.65μrad (3σ).

International audience; The ordered positions of atoms in crystals give a reason to study multiple Coulomb scattering of high energy charged particles within them. In addition, the accurate representation of multiple scattering of high energy protons in a bent crystal is important for studies of crystal assisted collimation at the SPS and the LHC. Multiple scattering of 400 GeV/c protons in bent silicon crystals was measured for orientations far from the directions of main crystallographic planes and axes in conditions excluding channeling of protons. The observed RMS widths of the angular distributions are a little larger than those obtained from the Moliere theory. Simulation of multiple scattering in a model of binary collisions with the crystal atoms shows about 3.5% decrease of the RMS deflection with respect to the model of a sequence of random collisions. We consider this as a possible indication of a reduction of multiple scattering of protons in a crystal in comparison with its amorphous state.

The effect of multiple volume reflections in one crystal was observed in each of several bent silicon strips for 400 GeV/c protons. This considerably increased the particle deflections. Some particles were also deflected due to channeling in one of the subsequent strips. As a result, the incident beam was strongly spread because of opposite directions of the deflections. A modified multi-strip deflector produced by periodic grooves on the surface of a thick silicon plate was used for these measurements. This technique provides perfect mutual alignment between crystal strips. Such multi-strip deflector may be effective for collider beam halo collimation and a study is planned at the CERN SPS circulating beam.

Channeling is the confinement of the trajectory of a charged particle in a crystalline solid. Positively charged particles channeled between crystal planes oscillate with a certain oscillation length , which depends on particle energy. A crystal whose thickness is half the oscillation length for planar channeling may act as a mirror for charged particles. If the incident angle of the particle trajectory with the crystal plane is less than the critical angle for channeling, under-barrier particles undergo half an oscillation and exit the crystal with the reversal of their transverse momentum, i.e., the particles are “mirrored” by the crystal planes. Unlike the traditional scheme relying on millimeter-long curved crystals, particle mirroring enables beam steering in high-energy accelerators via interactions with micrometer-thin straight crystal. The main advantage of mirroring is the interaction with a minimal amount of material along the beam, thereby decreasing unwanted incoherent nuclear interactions. The effectiveness of the mirror effect for ultrarelativistic positive particles has been experimentally proven at external lines of CERN-SPS. The mirroring effect in a 26.5-μm-thick Si crystal has been studied in the experiment with a narrow beam of 400 GeV/ c protons at the CERN-SPS. The reflection efficiency for a quasi-parallel beam is larger than 80%.

The use of microcontrollers and digital signal processors for the standalone control of stepper motors is nowadays widespread. At the same time, more complex and intelligent algorithms are being used and developed for real-time control and observation. These algorithms often require a precise model of the motor, but the standard electrical model used for hybrid stepper motors is frequently not capable of giving an accurate enough representation of the real system. In this paper, new model extensions are proposed in order to have a more precise model of the motor, while maintaining a low computational cost. It is shown that a significant improvement in the model fit is achieved with these extensions, and their computational performance is compared to study the cost of model improvement versus computation cost. The applicability of the proposed model extensions is demonstrated via their use in an extended Kalman filter running in real time for closed-loop current control and mechanical state estimation.

3D Carbon/Carbon (3D CC) is a well‐known industrial composite material for high‐temperature applications. One of its main advantages resides in its ability to maintain good material characteristics at elevated temperatures (higher than 2700°C), which makes it potentially interesting for beam interaction applications where high strength at high temperature is required. The ability of beam intercepting devices to withstand direct impacts of high‐energy proton beams is essential for the operation of the Large Hadron Collider (LHC) at the European Laboratory for Particle Physics (CERN). Following successful beam impact tests at CERN, as well as positive vacuum acceptance and metrology tests, several collimators and beam extraction absorbers are currently being equipped with 3D CC composite, as part of the LHC Injector Upgrade (LIU) and High Luminosity LHC (HL‐LHC) projects.

In this paper, the real-time architecture of a Digital Signal Processor based sensorless stepping motor driver, capable of driving a motor through long power cables and estimating its position and load torque, is described. The testbench developed in order to test its performance when driving an axis of a Large Hadron Collider collimator is presented, along with the results achieved. It is shown that the proposed driver is capable of achieving position and load torque estimates which allow step loss to be detected and mechanical degradation to be evaluated without the need for physical sensors.

Stepper motors are often used as actuators in harsh environments such as nuclear power plants or particle accelerators due to their high reliability and relatively precise open loop positioning. Their significant disadvantage, however, is their jerky motion profile, caused by the stepping action and introducing vibrations to the actuated system. These vibrations can reduce the lifetime of the mechanics when compared to the smooth motion profile that can be achieved using closed-loop position control. In order to have the reliability of open-loop control, but the smoother motion of closed-loop control, real-time position sensor fault detection can allow sensors to be used in normal operation and, if a fault is detected, switch to open-loop. In this paper, sensor fault detection for stepper motors using the Extended Kalman Filter is studied. A novel method to detect a sensor fault is proposed and compared to a standard one.

A deflection efficiency of about 61 % was observed for 400 GeV/c protons due to channeling, most strongly along the 〈110〉 axis of a bent silicon crystal. It is comparable with the deflection efficiency in planar channeling and considerably larger than in the case of the 〈111〉 axis. The measured probability of inelastic nuclear interactions of protons in channeling along the 〈110〉 axis is only about 10 % of its amorphous level whereas in channeling along the (110) planes it is about 25 % . High efficiency deflection and small beam losses make this axial orientation of a silicon crystal a useful tool for the beam steering of high energy charged particles.

Two high-accuracy goniometers equipped with two bent silicon crystals were installed in the betatron cleaning insertion of the CERN Large Hadron Collider (LHC) during its long shutdown. First beam tests were recently performed at the LHC with 450 GeV/c and 6500 GeV/c stored proton beams to investigate the feasibility of beam halo collimation assisted by bent crystals. For the first time channeling of 6500 GeV/c protons was observed in a particle accelerator. A strong reduction of beam losses due to nuclear inelastic interactions in the aligned crystal in comparison with its amorphous orientation was detected. The loss reduction value was about 24. Thus, the results show that deflection of particles by a bent crystal due to channeling is effective for this record particle energy., peer-reviewed

In this paper, an approach is proposed for the application of an extended Kalman filter (EKF) to a sensorless stepper motor drive, when the motor is separated from its drive by long cables. When the long cables and high-frequency pulsewidth-modulated control voltage signals are used together, the electrical signals differ greatly between the motor and drive sides of the cable. Since we consider the case where only drive-side data are available, it is therefore necessary to estimate the motor-side signals. Modeling the entire cable and motor system in an EKF is too computationally intensive for standard embedded real-time platforms. It is, therefore, proposed to divide the problem into an EKF, based only on the motor model, and separate motor-side signal estimators, the combination of which is less computationally demanding. The proposed approach's effectiveness is demonstrated in simulation.

In this paper the controller design for a high precision rotational stage based on a piezoelectric actuator is presented. As for almost all the structures based on the smart materials, this task is complicated by the presence of hysteresis and mechanical resonances. Moreover, when the structure is meant to operate in noisy environments, also the external disturbance rejection becomes a priority. To accomplish the aim of having high resolution also in the presence of strong external disturbances, a control strategy to obtain a high external disturbance rejection is designed, exploiting the high gain of the system resonance itself. Closed loop experimental results are shown in order to verify the tracking and disturbance rejection capabilities of the proposed controller.

W. Scandale a,b,e, F. Andrisani a, G. Arduini a, M. Butcher a, F. Cerutti a, M. Garattini a, S. Gilardoni a, A. Lechner a, R. Losito a, A. Masi a, A. Mereghetti a, E. Metral a, D. Mirarchi a,j, S. Montesano a, S. Redaelli a, R. Rossi a,e, P. Schoofs a, G. Smirnov a, E. Bagli c, L. Bandiera c, S. Baricordi c, P. Dalpiaz c, G. Germogli c, V. Guidi c, A. Mazzolari c, D. Vincenzi c, G. Claps d, S. Dabagov d,k,l, D. Hampai d, F. Murtas d, G. Cavoto e, F. Iacoangeli e, L. Ludovici e, R. Santacesaria e, P. Valente e, F. Galluccio f, A.G. Afonin g, Yu.A. Chesnokov g, A.A. Durumg, V.A. Maisheev g, Yu.E. Sandomirskiy g, A.A. Yanovich g, A.D. Kovalenko h, A.M. Taratin h,∗, Yu.A. Gavrikov i, Yu.M. Ivanov i, L.P. Lapina i, J. Fulcher j, G. Hall j, M. Pesaresi j, M. Raymond j

In ideal two-stage collimation systems, the secondary collimator–absorber should have its length sufficient to exclude practically the exit of halo particles with large impact parameters. In the UA9 experiments on the crystal assisted collimation of the SPS beam a 60 cm long tungsten bar is used as a secondary collimator–absorber which is insufficient for the full absorption of the halo protons. Multi-turn simulation studies of the collimation allowed to select the position for the beam loss monitor downstream the collimation area where the contribution of particles deflected by the crystal in channeling regime but emerging from the secondary collimator–absorber is considerably reduced. This allowed observation of a strong leakage reduction of halo protons from the SPS beam collimation area, thereby approaching the case with an ideal absorber.

Stepper motors are widely used in open-loop positioning applications. They are the choice of actuation for the collimators in the Large Hadron Collider, the largest particle accelerator at CERN. In this case the combination of precise positioning requirements and the highly radioactive operating environment is unique. The latter forces both the use of long cables to connect the motors to the drives and also prevents the use of standard position sensors. However, reliable and precise operation of the collimators is critical for the machine. A problem arises however from the use of stepper motors in open-loop. The mechanics of the collimators can wear due to the abrupt motion and torque profiles that are applied by the motors. Closed-loop position control allows smoother movements to be applied but it requires position feedback. The use of sensors in radioactive environments is very limited for reliability reasons. In order to allow the use of position sensors without reducing the long term reliability of the whole system, the possibility to switch online from closed to open loop is proposed and validated in this paper. It allows the use of closed-loop control when the position sensors function correctly and to switch online to open-loop when there is a sensor failure, without the need to stop the machine.

Bent silicon crystals in channeling mode are already used for beam extraction and collimation in particle accelerators. Volume reflection of beam particles is more efficient than beam channeling; however, the mean deflection angle is rather small. An experiment on the deflection of a 400 GeV/c proton beam and a 150 GeV/c π− beam at CERN using a multi-strip silicon deflector in reflection mode is described. The mean deflection angle of beam particles has been considerably increased due to sequential volume reflections realized in the deflector. This gives possibility for a successful usage of the multi-strip deflectors for beam collimation in high-energy accelerators.

The results of observation and studies of focusing of 400 GeV/ c proton beam with the help of bent single crystals are presented. Two silicon crystals have been used in the measurements. The focal length of the first and second crystals is found to be 1.48 m and 0.68 m, respectively. The mean square size of the horizontal profile in the focus was 3.1 and 4.3 times as small as at the exit of the crystals.

In this paper we provide an experimental characterization of creep and hysteresis in a multi-layer piezoelectric actuator (PEA), taking into account their relationships in terms of memory structure. We fit the well-known log-t model to the response of the PEA when driven by piecewise-constant signals, and find that both the instantaneous and the delayed response of the PEA display hysteretic dependence on the voltage level. We investigate experimentally the dependence of the creep coefficient on the input history, by driving the PEA along first-order reversal curves and congruent minor loops, and find that it displays peculiar features like strict congruence of the minor loops and discontinuities. We finally explain the observed experimental behaviors in terms of a slow relaxation of the staircase interface line in the Preisach plane.

The possibility for optimization of crystal assisted collimation has been studied at the CERN SPS for stored beams of protons and Pb ions with 270 GeV/ c per unit charge. A bent silicon crystal used as a primary collimator deflects halo particles in the channeling regime, directing them into a tungsten absorber. In channeling conditions a strong reduction of off-momentum particle numbers produced in the crystal and absorber, which form collimation leakage, has been observed in the first high dispersion (HD) area downstream. The present study shows that the collimation leakage is minimal for some values of the absorber offset relative to the crystal. The optimal offset value is larger for Pb ions because of their considerably larger ionization losses in the crystal, which cause large increases of particle betatron oscillation amplitudes. The optimal absorber offset allows obtaining maximal efficiency of crystal-assisted collimation.

The observation that juvenile chronic myelogenous leukemia (JCML) and childhood bone marrow monosomy 7 syndrome (Mo 7) are similar in many clinical and epidemiologic respects suggests a shared pathogenic basis and raises the possibility that the bone marrows of patients with JCML might lose chromosome 7 alleles by mechanisms that do not result in detectable cytogenetic deletions. We used a series of polymorphic markers mapped to chromosome 7 to test this hypothesis in 22 children with MPS and MDS, including 19 with JCML. All MPS and MDS samples demonstrated allelic heterozygosity with at least one chromosome 7 marker; 16 were heterozygous with probes from both 7p and 7q. Furthermore, the percentage of patient bone marrow samples heterozygous at each locus tested was similar to the frequency observed in the normal population. Whereas these data demonstrate that submicroscopic loss of large segments of chromosome 7 alleles is uncommon in children with MPS and MDS who do not have Mo 7, they do not exclude small deletions around an uncharacterized tumor-suppressor locus. Our results suggest that a number of distinct molecular events contribute to leukemogenesis, and we propose a multistep model to explain the similarities and differences between the major subtypes of childhood MPS and MDS.

In this paper the important practical issues of tuning and implementation of an Extended Kalman Filter for a sensorless hybrid stepper motor drive working with long cables is considered. A method to tune the filter using one set of data acquired from the real system is proposed. From this dataset, the system parameters and the Extended Kalman Filter's covariance matrices are estimated. The hardware and software implementation of the Extended Kalman Filter in the drive is also described, with specific emphasis on the code optimisation steps that are necessary to execute the filter at the desired sampling rate. Moreover, the developed drive's data acquisition capabilities and the experimental testbench used in the tuning and validation of the filter are discussed. Experimental results prove the effectiveness of the tuning method and implementation.

Switched mode stepper motor drives tend to have poor performance or even fail completely when the motor is fed through a long cable, as can be required in harsh environments. In this paper the design of a stepper motor output filter which solves this problem is presented. Output filters are used in induction motor applications, however their use with stepper motors and long cables has not been reported. A two stage filter, one devoted to dealing with the differential mode and the other with the common mode, is designed and validated experimentally. With this filter the drive performance is greatly improved, achieving a positioning repeatability even better than with the drive working without a long cable, the radiated emissions are reduced and the overvoltages at the motor terminals are eliminated.

Hybrid stepper motor drives are becoming increasingly sophisticated with complex control and observation real-time algorithms. Many of these algorithms, such as sensorless position detection, require precise motor models. The standard model normally used in real-time algorithms is not always able to model hybrid stepper motors sufficiently precisely. In this paper new extensions are made to the electrical model to improve its performance whilst maintaining relatively low computational complexity.