Advanced Synchronization Control of a Dual-Linear-Motor-Driven Gantry With Rotational Dynamics

Modern robots are increasingly being designed to collaborate with human, and the safety of human-robot interaction has become more significant than ever. Series elastic actuator (SEA) is a potential actuator system in force control for various robotic applications with inherent safe property. However, achieving the good performances of SEA torque control especially with unknown load-side dynamics is still challenging. In this article, a high performance decoupled torque controller is proposed to control the SEA as an ideal torque source that is suitable for various application scenarios. A more general decoupled dynamics of the SEA system is first established to fit the various scenarios by considering the large parametric uncertainties, nonlinearities, and unmodeled uncertainties. The adaptive robust control algorithm with an effective compensation mechanism is then developed to attenuate the uncertainties. Theoretically, the proposed approach guarantees the stability and high performance of the SEA system. Comparative experiments are carried out on a SEA testbed, and the experimental results demonstrate that the proposed approach has significant performance improvements over previous approaches.

This paper presents a sliding mode synchronization controller (SMSC) based on extended state observer (ESO) for the dual-drive system in gantry-type machine tools (GTMT). This controller achieves not only excellent tracking accuracy but also high synchronization performance. Firstly, a sliding mode synchronization controller is designed for the dual-drive system based on a simplified mode. Then, in order to handle the difficulties associated with the parameter uncertainties, external disturbances and coupling effects of the dual-drive system, a linear extended state observer (LESO) is designed. In this active disturbance rejection control (ADRC) technology, the total disturbances are treated as an extended state of the system and compensated with the disturbance observed value. Moreover, Rigorous theoretical analysis is performed to show that the proposed control method is able to achieve asymptotical tracking and synchronization performance for the dual-drive system in GTMT. Finally, Simulation studies are carried out and the results show that the proposed control strategy performs an improved tracking and synchronization motion control in comparison to the independent axis P-PI control approach.

Electro-hydraulic position servo system of valve-controlled symmetrical cylinder (EPSSVCS) is a very important and widely used electro-hydraulic servo system, the performance of which is often affected by friction nonlinearity and external random disturbances together with unmodeled dynamic factors such as parameter uncertainty in practical work. To improve the tracking performance of the system, a backstepping sliding mode control algorithm (BSMC) based on an extended state observer was presented in this paper. Firstly, a nonlinear mathematical model of the EPSSVCS was established which takes into account the composite disturbance induced by the systematic friction nonlinearity, external disturbances and unmodeled dynamic factors. Then, an extended state observer (ESO) was designed which can effectively estimate the velocity, acceleration, and composite disturbance of the valve-controlled cylinder online. Furthermore, a kind of BSMC was presented based on the online ESO estimates and the displacement feedback signals. The control law was given and the system stability was proved. The analysis results showed that the output signal of the system can effectively track the input signal under the influence of typical external disturbances and unmodeled dynamic factors, which illustrated the effectiveness of the established nonlinear mathematical model and the stability of the designed control system. Moreover, by taking the parameters of the electro-hydraulic servo system of a certain type of CNC machine tool as a real example, the proposed algorithm (BSMC) was compared with the conventional PID control algorithm, the backstepping sliding mode control algorithm (BSC), and the adaptive robust control algorithm (ARC), and the results verified the superiority of the BSMC. This work may provide a useful reference for the research in the field of related control systems.

While conventional Single Particle Tracking (SPT) techniques acquire 2D or 3D trajectories of particle probes, we have developed Single Particle Orientation and Rotational Tracking (SPORT) techniques to extract orientation and rotational information. Combined with DIC microscopy, the SPORT technique has been applied in biophysical studies, including membrane diffusion and intracellular transport. The rotational dynamics of nanoparticle vectors on live cell membranes was recorded and its influence on the fate of these nanoparticle vectors was elucidated. The rotational motions of gold nanorods with various surface modifiers were tracked continuously at a temporal resolution of 5 ms under a DIC microscope. We found that the rotational behaviors of gold nanorod vectors are strongly related to their surface charge, specific surface functional groups, and the availability of receptors on cell membranes. The study of rotational Brownian motion of nanoparticles on cell membranes will lead to a better understanding of the mechanisms of drug delivery and provide guidance in designing surface modification strategies for drug delivery vectors under various circumstances. To characterize the rotation mode of surface functionalized gold nanorods on cell membranes, the SPORT technique is combined with the correlation analysis of the bright and dark DIC intensities. The unique capabilities of visualizing and understanding rotational motions of functionalized nanoparticles on live cell membranes allow us to correlate rotational and translational dynamics in unprecedented detail and provide new insights for complex membrane processes, including electrostatic interactions, ligand-receptor binding, and lateral (confined and hopping) diffusion of membrane receptors. Surface-functionalized nanoparticles interact with the membrane in fundamentally different ways and exhibit distinct rotational modes. The early events of particle-membrane approach and attachment are directly visualized for the first time. The rotational dynamics of cargos in both active directional transport and pausing stages of axonal transport was also visualized using high-speed SPORT with a temporal resolution of 2 ms. Both long and short pauses are imaged, and the correlations between the pause duration, the rotational behaviour of the cargo at the pause, and the moving direction after the pause are established. Furthermore, the rotational dynamics leading to switching tracks are visualized in detail. These first-time observations of cargo's rotational dynamics provide new insights on how kinesin and dynein motors take the cargo through the alternating stages of active directional transport and pause. To improve the localization precision of the SPT technique with DIC microscopy, a precise three-dimensional (3D) localization method of spherical gold nanoparticle probes using model-based correlation coefficient mapping was introduced. To accomplish this, a stack of sample images at different z-positions are acquired, and a 3D intensity profile of the probe serving as the model is used to map out the positions of nanoparticles in the sample. By using this model-based correlation imaging method, precise localization can be achieved in imaging techniques with complicated point spread functions (PSF) such as differential interference contrast (DIC) microscopy. The 3D superlocalization method was applied to tracking gold nanospheres during live endocytosis events. Finally, a novel dual-modality imaging technique has been developed to super-localize a single gold nanorod while providing its orientation and rotational information. The super-localization of the gold nanorod can be accomplished by curve fitting the modified bright-field images generated by one of the two beams laterally shifted by the first Nomarski prism in a DIC microscope. The orientation and rotational information is derived from the DIC images of gold nanorods. The new imaging setup has been applied to study the steric hindrance induced by relatively large cargos in the microtubule gliding assay and to track nanocargos in the crowded cellular environment.

Purpose: Proposed small animal irradiation devices are typically isocentric gantry systems. Multi‐axis gantry systems require significant resources to develop and maintain. A static gantry system could provide the functionality of a multi‐axis gantry via subject rotation if subject motion could be minimized. In this study, we evaluated internal organ motion of mice within a prototype immobilization device during rotation. Method and Materials: Mice were anesthetized and immobilized in a prototype device designed to rigidly support animal positioning during rotation along the cranio‐caudal axis. The head and tail of the mouse were allowed to extend beyond the immobilization device as an internal control. Validation of internal and external immobilization was assessed using computed tomography imaging at multiple rotation angles. CT images were co‐registered (translated/rotated) using our research treatment planning system (CERR) into a common reference frame. Internal organ motion was assessed qualitatively by examination of internal anatomy in overlaid multiplane CT images. Quantitative evaluation of organ motion was assessed by delineating organ structures in CERR and comparing relative organ volumes and centers of mass. Results: CT imaging demonstrated minimal exterior contour changes (<1mm) in the immobilized regions during rotation. Un‐immobilized regions demonstrated the expected gravitational positional changes. Internal organs demonstrated sub‐millimeter changes in organ centers of mass (heart and lung) and small (<5 mm3) changes in volume during rotation. These variations were similar to the differences when the same CT was re‐contoured multiple times by the same operator and likely represent intra‐observer contouring variations. Conclusion: A microRT device with a stationary irradiator, collimator, tomographic imaging system, and rotating subject would reduce the overall cost and complexity of the unit. This study demonstrates rotational immobilization of small animals is feasible.This work supported in part by NIH R21 CA108677 and by a grant Varian, Inc.

The rotational Brownian motion of colloidal spheres in dense suspensions reflects local hydrodynamics and friction, both key to non-linear rheological phenomena such as shear-thickening and jamming, and transport in crowded environments, including intracellular migration and blood flow. To fully elucidate the role of rotational dynamics experimentally, it is crucial to measure the translational and rotational motion of all spheres simultaneously. Here, we develop compositionally uniform colloidal spheres with an off-centre, fully embedded core with a different fluorophore to the particle body, allowing access to rotational motion for all particles at the single-particle level. We reveal interparticle hydrodynamic rotational coupling in charged colloidal crystals. We also find that higher local crystallinity in denser crystals enhances rotational diffusivity, and that nearly arrested particles exhibit a stick-slip rotational motion due to frictional coupling. Our method sheds new light on the largely-unexplored local rotational dynamics of spherical particles in dense colloidal materials.

The electrohydraulic (EH) synchronized motion of two linear ram type hydraulic actuators is considered in this paper. Load and hydraulic component uncertainties are limiting the synchronization performance of open-loop type control approaches. A synchronizing adaptive robust control (ARC) algorithm is proposed to improve synchronization performance. Simulation results verified the effectiveness of the proposed ARC method as compared to the deterministic robust control (DRC) method.

The method of dynamic sliding variable structure control has been applied to the synchronization control of non-axis sheet lose machine. The current loop, velocity loop and location loop constructed the cascade tricyclic structure, and the current loop using the PI control while the velocity loop and location loop using the dynamic sliding variable structure control. The simulation results show that the synchronous controller good control performance to meet the system response speed and precision control requirements.

Through an appropriate change of reference frame and rescalings of the variables and the parameters introduced, the Hamiltonian of the three-body problem is written as a perturbed Kepler problem. In this system, new Delaunay variables are defined and a suitable configuration of the phase space and the mass parameters is chosen. In such a system, wide regions of librational and rotational motions where orbits are regular and stable are found. Close to the separatrix of these regions, the existence of chaotic motions presenting a double rotational and librational dynamics is proved, numerically, through Poincaré sections and the use of FLI.

In order to improve the quality of wireless English multimedia communication, according to the characteristics of space multimedia communication environment and communication equipment, this paper proposes a wireless English synchronous QoS control algorithm with low complexity and easy implementation. Using RTCPSRRTP timestamp and NTP absolute timestamp, the wireless English RTP timestamp is mapped to the same absolute reference clock (sender system time) respectively, and the wireless English synchronization detection decision rule is established according to the synchronization QoS performance requirements between wireless English media. Wireless English synchronization control system model at the receiver. At the receiving end, the wireless English stream is the main media stream and the video stream is the slave media stream. The synchronization detection and judgment is implemented in real time before the video frame is played. The synchronization between audio and video media is realized by corresponding synchronization control of wireless English playback. State space model reflects all the information of system dynamic behavior and is a complete description of system behavior. The state space model has a wide range of applications. It is not only suitable for SISO linear constant systems, but also suitable for nonlinear systems, time-varying systems, MIMO systems and stochastic systems. The more outstanding advantage is that the state space model adopts local calculation and uses the state variables inside the system to describe its dynamic characteristics. This property of local calculation not only greatly simplifies the mathematical expression of multi-dimensional system, but also facilitates the analysis and research of the system. The air link rate of the wireless transceiver is set to 512Kbps. The video is encoded based on H.264 and the audio is encoded based on G.729 Speech coding standard. Compared with the wireless English media synchronization control algorithm based on RTP / RTCP, the results show that the RMSE value after adopting the synchronization algorithm in this paper is reduced by 60.09% and 77.69% at most; Compared with the wireless English media synchronization control algorithm based on RTP / RTCP, the synchronization performance of this algorithm is better than the wireless English media synchronization control algorithm. The RMSE value is reduced by 2% on average and 5.2% at most. In addition, the synchronization control algorithm between wireless English media performs synchronization control by losing frames or pausing decoding before video decoding at the receiver, which affects the quality of wireless English video decoding and reconstruction.

Parametric uncertainties and uncertain nonlinearities always exist in mechatronics servo system and degrade their tracking accuracy. In this paper, adaptive robust control with fraction-order disturbance observer is synthesized for high accuracy motion control of a AC motor. The global stability was proved via Lyapunov Theorem. The proposed controller accounts for not only the parameter deviation (e.g., unknown inertia load), but also the uncertain nonlinearities (coming from modeling errors and external disturbances). In the resulting controller, parameter adaptation was used to reduce the parameter uncertainties, the fractional-order disturbance observer was used to estimate the modeling errors and external disturbances. To attenuate the uncompensated disturbances and errors, the robust controller was designed. The comparative simulation results show that the proposed controller guarantees a prescribed tracking performance.

Rotational dynamics in a simulated supercooled network-forming liquid

Binalarda burulma olması durumunda yapıya ilave deprem kuvvetleri etkimekte ve iç kuvvetler ve yer değiştirmeler artmaktadır. Bu nedenle düşey taşıyıcı sistemlerin planda mümkün olduğunca burulma etkisini azaltıcı şekilde yerleştirilmesi önemlidir. Burulma etkilerini en aza indirmek için rijitlik merkezi ile ağırlık merkezinin mümkün olduğunca yakın olması gerekmektedir. Her ne kadar mevcut deprem yönetmeliklerinin birçoğunda analiz aşamasında rijitlik merkezinin belirlenmesine ihtiyaç duyulmasa da özellikle burulma etkilerinin azaltılması açısından rijitlik merkezinin yerinin bilinmesi önemlidir. Uygulamada rijitlik merkezi ve kayma merkezi kavramları zaman zaman karıştırılmakta ve yanlış olarak bulunabilmektedir. Perde-çerçeve sistemlerde perde ve çerçevede hâkim davranışın farklı olması nedeniyle, perde ve çerçevelerin boyutlarının yapı yüksekliği boyunca sabit olması durumunda bile rijitlik merkezi kattan kata değişmektedir. Rijitlik merkezi bu tür yapılarda bazı katlarda plan dışına bile çıkabilmektedir. Bu çalışmada öncelikle rijitlik merkezi ve kayma merkezi kavramları kısaca açıklanmıştır. Daha sonra rijitlik merkezi ve kayma merkezinin bulunması için bir yaklaşım önerilmiştir. Sunulan yaklaşım literatürden alınan iki örnek üzerinde uygulanarak elde edilen sonuçlar literatür ve ETABS yazılımı ile karşılaştırılmış ve sunulan yöntemin uygunluğu gösterilmiştir.

Cogging force is an important source of disturbances for linear-motor-driven systems. To obtain a higher level of contouring motion control performance for multiaxis mechanical systems subject to significant nonlinear cogging forces, both the coordinated control of multiaxis motions and the effective compensation of cogging forces are necessary. In addition, the effect of unavoidable velocity measurement noises needs to be sufficiently attenuated. This paper presents a discontinuous-projection-based desired compensation adaptive robust contouring controller to address these control issues all at once. Specifically, the presented approach explicitly takes into account the specific characteristics of cogging forces in the controller designs and employs the task coordinate formulation for coordinated motion controls. Theoretically, the resulting controller achieves a guaranteed transient performance and a steady-state contouring accuracy even in the presence of both parametric uncertainties and uncertain nonlinearities. In addition, the controller also achieves asymptotic output tracking when there are parametric uncertainties only. Comparative experimental results obtained on a high-speed Anorad industrial biaxial precision gantry are presented to verify the excellent contouring performance of the proposed control scheme and the effectiveness of the cogging force compensations.

A DC/DC boost converter exhibits highly nonlinear properties and subjects to certain uncertainties, like load change, input voltage variation, and parametric uncertainties. This paper first presents an improved accurate model of the converters, including the parasitic elements and model uncertainties, which are usually existed in actual systems but not (or not sufficiently) considered in most of the literatures. In view of the non-minimum phase nature of boost converter, a new indirect control scheme is proposed, in which the output voltage is indirectly controlled by tracking a corresponding inductor reference current. An integrated direct/indirect adaptive robust controller (DIARC) is presented to achieve both accurate parameter estimation and perfect current tracking in the presence of both parametric uncertainties and uncertain nonlinearities. With an accurate parameter estimation, the corresponding inductor reference current can be precisely calculated. A rigorous theoretical proving is given and simulation results shows the effectiveness of the proposed controller and control scheme.