Modeling the Static Force of a Festo Pneumatic Muscle Actuator: A New Approach and a Comparison to Existing Models

Erratum published on 13 March 2018, see Actuators 2018, 7(1), 9. https://doi.org/10.3390/act7010009In this paper, a new approach for modeling the static force characteristic of Festo pneumatic muscle actuators (PMAs) will be presented. The model is physically motivated and therefore gives a deeper understanding of the Festo PMA. After introducing the new model, it will be validated through a comparison to a measured force map of a Festo DMSP-10-250 and a DMSP-20-300, respectively. It will be shown that the error between the new model and the measured data is below 4.4% for the DMSP-10-250 and below 2.35% for the DMSP-20-300. In addition, the quality of the presented model will be compared to the quality of existing models by comparing the maximum error. It can be seen that the newly introduced model is closer to the measured force characteristic of a Festo PMA than any existing model.BMWi, ZF4007503, Development of a PMA-driven Exoskeleton for the Upper Bod

A Novel Framework for a Systematic Integration of Pneumatic-Muscle-Actuator-Driven Joints into Robotic Systems Via a Torque Control Interface

In this paper, two different torque control approaches for PMA-driven (PMA = Pneumatic muscle actuator) revolute joints are presented and tested. In previous work controllers for PMA-driven robots are typically customized for the use on a specific robotic system. In contrast, the proposed controllers define a general control interface for every robot that is actuated by PMA-driven joints. It will be shown that controlling the torque of a PMA-driven joint enables the use of standard robotic motion control frameworks, because the torque represents the natural input of the robotic equation of motion. Therefore, both proposed torque control approaches are interconnecting PMAs and their challenging characteristics on the one hand and “conventional” motion control strategies for robots on the other hand. After a detailed discussion of two different torque control approaches, we show that a torque controller handles all characteristics and dynamics of a PMA-driven joint internally, which implies that only its bandwidth and its static torque characteristic must be taken into account for the design of the outer motion control loop. This feature simplifies the integration of PMA-driven joints in robotic systems enormously, as will be demonstrated by a design of a cascade-structured, flatness-based motion controller for an exemplary robot with one degree of freedom.BMWi, ZF4007503, Development of a PMA-driven Exoskeleton for the Upper Bod

A study of CP violation in B-+/- -> DK +/- and B-+/- -> D pi(+/-) decays with D -> (KSK +/-)-K-0 pi(-/+) final states

A first study of CP violation in the decay modes $B^\pm\to [K^0_{\rm S} K^\pm \pi^\mp]_D h^\pm$ and $B^\pm\to [K^0_{\rm S} K^\mp \pi^\pm]_D h^\pm$, where $h$ labels a $K$ or $\pi$ meson and $D$ labels a $D^0$ or $\overline{D}^0$ meson, is performed. The analysis uses the LHCb data set collected in $pp$ collisions, corresponding to an integrated luminosity of 3 fb$^{-1}$. The analysis is sensitive to the CP-violating CKM phase $\gamma$ through seven observables: one charge asymmetry in each of the four modes and three ratios of the charge-integrated yields. The results are consistent with measurements of $\gamma$ using other decay modes

Measurement of Upsilon production in collisions at root s=2.76 TeV

The production of $\Upsilon(1S)$, $\Upsilon(2S)$ and $\Upsilon(3S)$ mesons decaying into the dimuon final state is studied with the LHCb detector using a data sample corresponding to an integrated luminosity of 3.3 $pb^{-1}$ collected in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=2.76$ TeV. The differential production cross-sections times dimuon branching fractions are measured as functions of the $\Upsilon$ transverse momentum and rapidity, over the ranges $p_{\rm T} Upsilon(1S) X) x B(Upsilon(1S) -> mu+mu-) = 1.111 +/- 0.043 +/- 0.044 nb, sigma(pp -> Upsilon(2S) X) x B(Upsilon(2S) -> mu+mu-) = 0.264 +/- 0.023 +/- 0.011 nb, sigma(pp -> Upsilon(3S) X) x B(Upsilon(3S) -> mu+mu-) = 0.159 +/- 0.020 +/- 0.007 nb, where the first uncertainty is statistical and the second systematic

Search for CP violation using T-odd correlations in D-0 -> K+K-pi(+)pi(-) decays

A search for $CP$ violation using $T$-odd correlations is performed using the four-body $D^0 \to K^+K^-\pi^+\pi^-$ decay, selected from semileptonic $B$ decays. The data sample corresponds to integrated luminosities of $1.0\,\text{fb}^{-1}$ and $2.0\,\text{fb}^{-1}$ recorded at the centre-of-mass energies of 7 TeV and 8 TeV, respectively. The $CP$-violating asymmetry $a_{CP}^{T\text{-odd}}$ is measured to be $(0.18\pm 0.29\text{(stat)}\pm 0.04\text{(syst)})\%$. Searches for $CP$ violation in different regions of phase space of the four-body decay, and as a function of the $D^0$ decay time, are also presented. No significant deviation from the $CP$ conservation hypothesis is found

Measurement of CP asymmetry in B-s(0) -> D-s(-/+) K--/+ decays

We report on measurements of the time-dependent CP violating observables in $B^0_s\rightarrow D^{\mp}_s K^{\pm}$ decays using a dataset corresponding to 1.0 fb$^{-1}$ of pp collisions recorded with the LHCb detector. We find the CP violating observables $C_f=0.53\pm0.25\pm0.04$, $A^{\Delta\Gamma}_f=0.37\pm0.42\pm0.20$, $A^{\Delta\Gamma}_{\bar{f}}=0.20\pm0.41\pm0.20$, $S_f=-1.09\pm0.33\pm0.08$, $S_{\bar{f}}=-0.36\pm0.34\pm0.08$, where the uncertainties are statistical and systematic, respectively. We use these observables to make the first measurement of the CKM angle $\gamma$ in $B^0_s\rightarrow D^{\mp}_s K^{\pm}$ decays, finding $\gamma$ = (115$_{-43}^{+28}$)$^\circ$ modulo 180$^\circ$ at 68% CL, where the error contains both statistical and systematic uncertainties.We report on measurements of the time-dependent CP violating observables in B$_{s}^{0}$  → D$_{s}^{∓}$ K$^{±}$ decays using a dataset corresponding to 1.0 fb$^{−1}$ of pp collisions recorded with the LHCb detector. We find the CP violating observables C$_{f}$ = 0.53±0.25±0.04, A$_{f}^{ΔΓ}$  = 0.37 ± 0.42 ± 0.20, ${A}_{\overline{f}}^{\varDelta \varGamma }=0.20\pm 0.41\pm 0.20$ , S$_{f}$ = −1.09±0.33±0.08, ${S}_{\overline{f}}=-0.36\pm 0.34\pm 0.08$ , where the uncertainties are statistical and systematic, respectively. Using these observables together with a recent measurement of the B$_{s}^{0}$ mixing phase −2β$_{s}$ leads to the first extraction of the CKM angle γ from B$_{s}^{0}$  → D$_{s}^{∓}$ K$^{±}$ decays, finding γ = (115$_{− 43}^{+ 28}$ )° modulo 180° at 68% CL, where the error contains both statistical and systematic uncertainties.We report on measurements of the time-dependent CP violating observables in $B^0_s\rightarrow D^{\mp}_s K^{\pm}$ decays using a dataset corresponding to 1.0 fb$^{-1}$ of pp collisions recorded with the LHCb detector. We find the CP violating observables $C_f=0.53\pm0.25\pm0.04$, $A^{\Delta\Gamma}_f=0.37\pm0.42\pm0.20$, $A^{\Delta\Gamma}_{\bar{f}}=0.20\pm0.41\pm0.20$, $S_f=-1.09\pm0.33\pm0.08$, $S_{\bar{f}}=-0.36\pm0.34\pm0.08$, where the uncertainties are statistical and systematic, respectively. Using these observables together with a recent measurement of the $B^0_s$ mixing phase $-2\beta_s$ leads to the first extraction of the CKM angle $\gamma$ from $B^0_s \rightarrow D^{\mp}_s K^{\pm}$ decays, finding $\gamma$ = (115$_{-43}^{+28}$)$^\circ$ modulo 180$^\circ$ at 68% CL, where the error contains both statistical and systematic uncertainties

Study of forward Z + jet production in pp collisions at √s=7 TeV

A measurement of the $Z(\rightarrow\mu^+\mu^-)$+jet production cross-section in $pp$ collisions at a centre-of-mass energy $\sqrt{s} = 7$ TeV is presented. The analysis is based on an integrated luminosity of $1.0\,\text{fb}^{-1}$ recorded by the LHCb experiment. Results are shown with two jet transverse momentum thresholds, 10 and 20 GeV, for both the overall cross-section within the fiducial volume, and for six differential cross-section measurements. The fiducial volume requires that both the jet and the muons from the Z boson decay are produced in the forward direction ($2.0<\eta<4.5$). The results show good agreement with theoretical predictions at the second-order expansion in the coupling of the strong interaction.A measurement of the $Z(\rightarrow\mu^+\mu^-)$+jet production cross-section in $pp$ collisions at a centre-of-mass energy $\sqrt{s} = 7$ TeV is presented. The analysis is based on an integrated luminosity of $1.0\,\text{fb}^{-1}$ recorded by the LHCb experiment. Results are shown with two jet transverse momentum thresholds, 10 and 20 GeV, for both the overall cross-section within the fiducial volume, and for six differential cross-section measurements. The fiducial volume requires that both the jet and the muons from the Z boson decay are produced in the forward direction ($2.0<\eta<4.5$). The results show good agreement with theoretical predictions at the second-order expansion in the coupling of the strong interaction

Regelung von pneumatisch-muskel-aktuierten Gelenken in robotischen Anwendungen : pneumatische Muskeln und Roboter mittels einer Momentenregler-Schnittstelle verbinden

Many robotic systems can be improved by novel, lightweight, and elastic actuators. While smaller weight reduces the kinetic energy of the system, elasticity offers the potential to absorb and release potential energy. Thus, the safety of the robot can be increased only by the use of light and elastic actuators, so that there is less energy transmitted in the case of collisions and damages or injuries would therefore be milder. In addition, stored potential energy can be used to perform motion sequences with increased energy efficiency. One type of these actuators are pneumatic-muscle-actuator-driven joints – a combination of two pneumatic-muscle-actuators (PMAs) and a pulley –, as they provide a high torque-to-weight ratio with an adjustable stiffness. Analogously to biological muscle pairs, PMA-driven joints also yield the opportunity to change their stiffness via co-contraction and, due to this, to adapt to the demands of varying tasks. The investigation of the properties of PMA-driven joints and their integration into robotic systems form the core of this dissertation. Since PMA-driven joints consist essentially of two pneumatic muscle actuators, there is an initial chapter devoted to force modeling of pneumatic muscles in addition to the study of PMA-driven joints. It compares existing force models based on a new quality measure and introduces a new model with higher accuracy. Although there were numerous publications on robots with PMA-driven joints prior to this work, little attention has been given to their properties in general. It remains mostly unclear why a specific robot with PMA-driven joints is able to fulfill its task and how this depends on the characteristics of the chosen PMA-driven joints. Motivated by this, the present thesis provides a general discussion on the characteristics of PMA-driven joints, like their static torque range, their joint stiffness and the bandwidth of their joint torque. All results are discussed with the goal to drive a robotic system with PMA-driven joints and all essential information will be provided within this thesis. With this information at hand it will be demonstrated how to use this information to drive three different robotic systems with PMA-driven joints, successfully. Unlike most other publications on robots with PMA-driven joints, the focus of this work is less on the issue of controlling a particular robot but rather on discussing, developing and proposing a general framework for successful control of any robot with PMA-driven joints. Depending on the robot and its task, joint torques must be provided at an adequate height and speed, and only if these specifications can be met by the actuators, the robot can fulfill its task. As an interface between the robot on the one side and the actuators on the other side, a torque controller for PMA-driven joints will be developed and employed for different applications in this thesis. With this torque controller in place, the complex PMA-driven joint dynamics can be reduced to only the static torque characteristic and the bandwidth of the controller. Since these properties of PMA-driven joints are examined in detail in this dissertation, this thesis forms the necessary basis for the successful application of PMA-driven joints in robotic systems. The simplicity of integrating PMA-driven joints under torque control into robots will be demonstrated by using three different robots. Firstly, a robot with one degree of freedom is positioned with PMA-driven joints, and secondly, the same is demonstrated for a robot with two degrees of freedom. Lastly, a rehabilitation robot with a PMA-driven joint is realized which facilitates a controlled-active-motion therapy, as used after cruciate ligament rupture.Viele Robotersysteme können durch neuartige, leichte und elastische Aktoren verbessert werden. Während ein geringeres Gewicht die kinetische Energie des Systems ver­ ringert, bietet Elastizität die Möglichkeit, potentielle Energie aufzunehmen und wieder abzugeben. Somit erhöht sich, allein durch den Einsatz leichter und elastischer Aktoren, die Sicherheit des Roboters, da im Falle einer Kollision weniger Energie übertragen wird und somit Schäden oder Verletzungen milder ausfallen. Darüber hinaus kann gespeicherte potentielle Energie dazu genutzt werden, Bewegungsabläufe mit erhöhter Energieeffizienz auszuführen. Aktoren mit variabler Elastizität und einem besonders ho­ hen Kraft-zu-Eigengewicht-Verhältnis sind pneumatisch-muskel-aktuierte (PM-aktuierte) Gelenke. Analog zu biologischen Muskelpaaren haben auch PM-aktuierte Gelenke die Möglichkeit, ihre Steifigkeit durch Kokontraktion zu ändern und sich so an die Ansprüche variierender Aufgaben anzupassen. Die Untersuchung der Eigenschaften dieser Aktoren und deren Integration in Robotersysteme bilden den Kern der vorliegenden Arbeit. Obwohl es bereits vor dieser Arbeit zahlreiche Publikationen zu Robotern mit PM-ak­ tuierten Gelenken gab, wurden deren Eigenschaften nicht ausreichend diskutiert. In dieser Dissertation wird die Diskussion über die Charakteristiken von PM-aktuierten Gelenken bereitgestellt. Im Gegensatz zu anderen Publikationen über Roboter mit PM-aktuierten Gelenken steht weniger die Frage nach der Regelung eines bestimmten Roboters im Vordergrund, sondern vielmehr die Grundlage für eine erfolgreiche Regelung eines beliebigen Roboters mit PM-aktuierten Gelenken. Je nach Roboter und dessen Aufgabe müssen Gelenkmomente in adäquater Höhe und Geschwindigkeit bereitgestellt werden, und nur falls diese Vorgaben von den Aktoren eingehalten werden können, kann der Roboter seine Aufgabe erfüllen. Die Schnittstellenkommunikation zwischen dem Roboter und den Aktoren übernimmt ein in dieser Arbeit entwickelter Momentenregler. Mit diesem Momentenregler kann das PM-aktuierte Gelenk ausschließlich anhand seiner statischen Momentencharakteristik und der Bandbreite des Reglers beschrieben werden. Da die Eigenschaften PM-aktuierter Gelenke in dieser Dissertation vordergründig unter­ sucht werden, bildet die vorliegende Arbeit die nötige Grundlage für einen erfolgreichen Einsatz PM-aktuierter Gelenke in Robotern. Die Einfachheit, PM-aktuierte Gelenke mit Momentenregler in Roboter zu integrieren, wird anhand dreier verschiedener Roboter gezeigt. Dabei werden jeweils ein Roboter mit einem Freiheitsgrad und ein Roboter mit zwei Freiheitsgraden in der Position geregelt sowie ein Rehabilitationsroboter, der die Möglichkeit bietet, eine Widerstandsmomententrajektorie beliebig vorzugeben. Da PM-aktuierte Gelenke im Wesentlichen aus zwei pneumatischen Muskelaktoren bestehen, ist neben der Untersuchung von PM-aktuierten Gelenken ein Kapitel dieser Dissertation zunächst der Kraftmodellierung pneumatischer Muskeln gewidmet. In diesem werden bestehende Kraftmodelle anhand eines neuen Gütemaßes miteinander verglichen und ein neues Model mit höherer Genauigkeit eingeführt