A Direct Drive θ‐Z Motor for Rotary and Linear Motion

The increasing evidence of rotational motions due to earthquakes is now motivating civil engineers to investigate the effects of rotational ground motions on structures. With the advancement in instrumentation techniques, rotational sensors have been developed in the past few years, which can measure three components of rotational waves in addition to the translational waves. Conventionally, buildings are designed to withstand horizontal and vertical translational ground motions to minimize the damage to human life and financial losses during an earthquake. Damage to the structure is identified at two levels; (i) structural and (ii) material. The structural damage in reinforced concrete buildings is visible in the form of cracks and spalling concrete, which reduces the overall load-carrying capacity of the building. The damage at the material level is not visible to the human eye. This damage can be identified using coda wave interferometry techniques. In this method, a high cross-correlation between the coda of two waves passing a point on different days of experiment indicates a negligible change in the shear wave velocity of the material. In comparison, a lower cross-correlation signifies considerable change in the material properties.    In order to understand how rotational motions affect reinforced concrete structures and how these can be simulated, the present work makes a novel attempt to use the newly developed rotation measuring sensors, BlueSeis 3A and IMU50, to understand the damage in a model concrete bridge structure (BLEIB). We employ advanced sensors in addition to conventional broadband and ultrasonic sensors on the 24m long two-span continuous reinforced concrete bridge equipped with various non-destructive sensing techniques and subjected to a variable pre-tension force of up to 450kN and various static loads. As an initial analysis, we first identify the bridge's first three fundamental frequencies and mode shapes from both recorded translational and rotational data. The analysis shows that the same fundamental frequencies are obtained from the recorded translational and rotational data. However, we expect to see a difference in the mode shapes. Theoretically, rotations are maximum at the bridge support and minimum at the centre of the bridge span. This behaviour is the reverse of what we observe from translational motions, where maximum translations are observed at the centre of the span while minimum at the supports. As the study plans to simulate rotational motions for reinforced concrete structures, a finite element model of the prototype bridge is also developed, and the fundamental frequencies and mode shapes of the model are validated with those obtained from the recorded data. This work shall be extended to applying coda wave interferometry to the rotational data recorded on the bridge to understanding the change observed in material properties when the bridge is subjected to active and passive forces.

Electromagnetic damper using brushless DC motor was developed. The damper has a ball screw mechanism, and a linear motion is converted into rotational motion. The blushless DC motor was installed in tip of the ball screw shaft, and electrical power was generated when the shaft was rotating. Electrical resistance was inserted into terminal of the motor as delta-connected winding, and capacitances were also inserted in parallel. Theory of the torque was introduced with current limit. Force and displacement curves were measured, and resisting force characteristics were confirmed. Dynamic propertied of the damper was investigated.

Precision measurement of segmental motion from flexion—extension radiographs of the lumbar spine

BackgroundDuring prostate stereotactic body radiation therapy (SBRT), prostate tumor translational motion may deteriorate the planned dose distribution. Most of the major advances in motion management to date have focused on correcting this one aspect of the tumor motion, translation. However, large prostate rotation up to 30° has been measured. As the technological innovation evolves toward delivering increasingly precise radiotherapy, it is important to quantify the clinical benefit of translational and rotational motion correction over translational motion correction alone.PurposeThe purpose of this work was to quantify the dosimetric impact of intrafractional dynamic rotation of the prostate measured with a six degrees‐of‐freedom tumor motion monitoring technology.MethodsThe delivered dose was reconstructed including (a) translational and rotational motion and (b) only translational motion of the tumor for 32 prostate cancer patients recruited on a 5‐fraction prostate SBRT clinical trial. Patients on the trial received 7.25 Gy in a treatment fraction. A 5 mm clinical target volume (CTV) to planning target volume (PTV) margin was applied in all directions except the posterior direction where a 3 mm expansion was used. Prostate intrafractional translational motion was managed using a gating strategy, and any translation above the gating threshold was corrected by applying an equivalent couch shift. The residual translational motion is denoted as Tres. Prostate intrafractional rotational motion Runcorr was recorded but not corrected. The dose differences from the planned dose due to Tres + Runcorr, ΔD(Tres + Runcorr) and due to Tres alone, ΔD(Tres), were then determined for CTV D98, PTV D95, bladder V6Gy, and rectum V6Gy. The residual dose error due to uncorrected rotation, Runcorr was then quantified: ΔDResidual = ΔD(Tres + Runcorr) ‐ ΔD(Tres).ResultsFractional data analysis shows that the dose differences from the plan (both ΔD(Tres + Runcorr) and ΔD(Tres)) for CTV D98 was less than 5% in all treatment fractions. ΔD(Tres + Runcorr) was larger than 5% in one fraction for PTV D95, in one fraction for bladder V6Gy, and in five fractions for rectum V6Gy. Uncorrected rotation, Runcorr induced residual dose error, ΔDResidual, resulted in less dose to CTV and PTV in 43% and 59% treatment fractions, respectively, and more dose to bladder and rectum in 51% and 53% treatment fractions, respectively. The cumulative dose over five fractions, ∑D(Tres + Runcorr) and ∑D(Tres), was always within 5% of the planned dose for all four structures for every patient.ConclusionsThe dosimetric impact of tumor rotation on a large prostate cancer patient cohort was quantified in this study. These results suggest that the standard 3–5 mm CTV‐PTV margin was sufficient to account for the intrafraction prostate rotation observed for this cohort of patients, provided an appropriate gating threshold was applied to correct for translational motion. Residual dose errors due to uncorrected prostate rotation were small in magnitude, which may be corrected using different treatment adaptation strategies to further improve the dosimetric accuracy.

When whole-body is exposed to vertical vibration, asymmetry shape of human body affects the response on the translational(fore-aft, lateral, vertical) and rotational(roll, pitch, yaw) motion. While the translational motion has been studied with various titles, it has been rare to study the rotational motion of human body exposed to vertical excitation because of lack of experimental equipment. This study was performed by using a 6-axis force plate installing strain gage type sensors for the rotational response. Sixteen male subjects were exposed to vertical vibration on rigid seat in order to investigate apparent mass of three translational motion and apparent eccentric mass of three rotational motion. Random signal was generated to make excitation vibration which was on an effective frequency range of 3~40 Hz, and magnitude of 0.224 m/<TEX>$s^2$</TEX> r.m.s. The frequency range and magnitude used was selected for the vibration of passenger vehicle on idling condition. As the result, cross-axis apparent masses of fore-and-aft and lateral direction were not significant showing 20 % and 3 % of vertical apparent mass relatively. And apparent eccentric mass of pitch motion was dominant when compared to that of roll and yaw motion, which is reasoned by asymmetry direction of human body sitting on a seat.

Cable driven parallel robot (CDPR) possesses large workspace, outstanding dynamic performance and high load capacity. However, due to the actuation method of CDPR, only limited motion modes can be achieved, and its rotational and translational motions are usually coupled. This letter presents a novel design of CDPR, through applying winch-integrated driving method and wrapping driving cables around the moving platform, the positions of driving cables' attach points on moving platform adaptively vary with the movement. The proposed CDPR design naturally enables a novel planar one-translational and one-rotational (1R1T) motion mode with decoupled control of translation and rotation. The performance of the design is validated through simulation and experiment, confirming that there are no other motions generated and the translational and rotational motions can be controlled independently. The proposed configuration further expands the motion mode as well as operational capabilities of CDPR.

A video containing multiple objects undergoing independent translational and rotational motions is analyzed through a combination of spatial- and frequency-domain representations. The Fourier transform of the sequence is used to estimate the multiple translations and rotations in a computationally efficient manner, which is also robust to local inaccuracies and global illumination changes. A novel algorithm is presented for the simultaneous extraction of all objects undergoing translation and the background via a least squares technique that takes place entirely in the Fourier domain. Spatial information is combined with the frequency domain object extraction results, to further refine them. For the case of rotational or combined, rotational and translational motions, the moving objects are segmented using purely spatial information. We show that the combined analysis takes advantage of the strengths of both representations, by providing reliable and computationally efficient motion estimates and object segmentation. The proposed algorithm is shown to be robust to local noise and occlusion, because of its global nature. Experiments are performed on synthetic and real video sequences to demonstrate the capabilities of our approach.

We study the Stokes-Einstein (SE) and the Stokes-Einstein-Debye (SED) relations, Dt=kBT/6pietaR and Dr=kBT/8pietaR3, where Dt and Dr are the translational and rotational diffusivity, respectively, T is the temperature, eta the viscosity, kB the Boltzmann constant, and R the "molecular" radius. Our results are based on molecular dynamics simulations of the extended simple point charge model of water. We find that both the SE and SED relations break down at low temperature. To explore the relationship between these breakdowns and dynamical heterogeneities (DHs), we also calculate the SE and SED relations for subsets of the 7% "fastest" and 7% "slowest" molecules. We find that the SE and SED relations break down in both subsets, and that the breakdowns occur on all scales of mobility. Thus these breakdowns appear to be generalized phenomena, in contrast with a view where only the most mobile molecules are the origin of the breakdown of the SE and SED relations, embedded in an inactive background where these relations hold. At low temperature, the SE and SED relations in both subsets of molecules are replaced with "fractional" SE and SED relations, Dt approximately (tau/T)-xit and Dr approximately (tau/T)-xir, where xit approximately 0.84(<1) and xir approximately 0.75(<1). We also find that there is a decoupling between rotational and translational motion, and that this decoupling occurs in both the fastest and slowest subsets of molecules. Further, we find that, the decoupling increases upon cooling, but that the probability of a molecule being classified as both translationally and rotationally fastest also increases. To study the effect of time scale for SE and SED breakdown and decoupling, we introduce a time-dependent version of the SE and SED relations, and a time-dependent function that measures the extent of decoupling. Our results suggest that both the decoupling and SE and SED breakdowns originate at a time scale corresponding to the end of the cage regime, when diffusion starts. This is also the time scale when the DHs are more relevant. Our work also demonstrates that selecting DHs on the basis of translational or rotational motion more strongly biases the calculation of diffusion constants than other dynamical properties such as relaxation times.

Molecular dynamics studies of two generalized forms of the rough sphere model are reported. The generalization permits us to vary the coupling between rotational and translational motion through a stick parameter λ. The autocorrelation functions show deviations from the Enskog theory for all values of λ studied—indicating that collective effects are involved. It appears that the angular velocity correlation function is the sum of two exponentials. A simulation of a mixture of disparate sized rough spheres was also performed. It is found that the rotational motion of the small particle is not significantly altered upon introduction of the large particles, but the linear velocity correlation function of the small particle differes considerably from that of the neat fluid (in the time regime from 5–15 mean collision time units).

In this work, it was studied the process of interaction between the Apocynin Dimer (DiApocynin -DiApo) and , or Cyclodextrin (CD). All processes were described considering the translational and rotational movements. The translational movement was considered along the z-axis followed by simultaneous rotational (circular) movements (from 0 to 360 o in intervals of 1.0 o ) of the Apocynin Dimer around its center of mass. It were generated molecular stru tures i these pro esses a d the al ulatio s o er i g the o for atio al a al sis of , and -CD DiApo were carried out using the PM3 semiempirical methodology. To the most sta le ole ular stru tures to , , -CD, a ordi g to statisti al ther od a i a al sis, were obtained the interaction energies of -5,251; -63,012 e -65,637 kJ.mol -at ONIOM2(B3LYP/6-31G(d):PM3) level of theory, respectively.

Traditional research-grade three-component seismic sensors are inherently sensitive to both translational ground motion and rotational (tilt) motion, particularly on the horizontal components. The outputs of traditional seismometers represent a sum of rotation and displacement information. As a result, recorded signals represent a superposition of displacement and rotation, even though most processing and interpretation workflows assume purely translational motion. This limitation becomes increasingly important for applications involving near-field ground motion, ground-structure interaction, and structural response monitoring, where rotational effects can significantly influence observed building and infrastructure dynamics. Recent advances in sensor technology are now allowing accurate and precise discrimination between translational and rotational motion. Stratis is the world’s first integrated seismic sensor to provide simultaneous, co-located measurements of all six degrees of freedom, delivering concurrent velocity (m/s) and rotational velocity (rad/s) outputs in the Z, N, and E directions. By measuring all six degrees of freedom at a single point, Stratis avoids the spatial differencing and approximation errors associated with multi-instrument rotational estimates. The availability of co-located rotational measurements enables correction for tilt-induced contamination in translational records, supporting the derivation of rotation-corrected displacement signals and improving the fidelity of ground motion and structural response observations. By integrating rotational and translational sensing into a single compact instrument, the installation process is also greatly simplified, thereby enabling wider access to rotational seismic data. This supports interdisciplinary applications spanning seismology, structural engineering, and seismic risk mitigation, including post-event damage assessment, long-term monitoring of structural health, and improved characterization of earthquake ground motion relevant to robust infrastructure design.

We report on novel 3D tunable Fabry-Perot etalons fabricated by surface micromachining technique. The Fabry-Perot etalons are tuned by rotation or translation movements. For the Fabry-Perot etalon tuned by rotational movement, the Fabry-Perot etalon is integrated with a rotational stage and the effective light path distance is adjusted by rotating the stage. The transmission peak wavelength shift (Delta) (lambda) p of 32 nm has been observed for tuning angle (Delta) (Theta) equal to 70 degrees. For the Fabry-Perot etalon tuned by linear translation, two mirrors consitituting the etalon are integrated with translational stages. The stage consists of a slider constrained by flanges along the two edges so that only translational movement along the optical axis is allowed. By changing the distance between two mirrors for 2.25 micrometers , a transmission peak wavelength shift (Delta) (lambda) p of 103 nm has been achieved. The 3D Fabry-Perot etalons can be easily extended to integrate with other micro- optical elements fabricated in a similar way. Furthermore, fiber-to-fiber coupling will be easy with this 3D approach. The 3D tunable Fabry-Perot etalon is another successful demonstration of the free-space micro-optical bench (FS-MOB) technology we have proposed previously.

Self-motion perception relies on the central integration of vestibular, visual and proprioceptive sensory inputs into a coherent percept of self-motion. To better understand the central integration of linear and rotational stimuli, we examined rotational and translational movements in the horizontal plane in healthy subjects (HS) and in patients with unilateral vestibular hypofunction (pwUVH). We established a novel heading discrimination paradigm using a motion platform to examine heading direction perception for translational movements with additional yaw rotations of − 1°, 0°, or 1°. We examined 26 HS and 26 pwUVH. Heading direction perception in HS and pwUVH was strongly driven by rotational stimuli. Among HS, adding 1° of yaw rotation to a translational movement resulted in an average shift of perceived straight-ahead translations to the opposite side of 2.15° (yaw to the right) and 2.30° (yaw to the left) respectively. pwUVH showed significantly higher discrimination thresholds (right UVH +3.3°, left UVH +6.4°) across all conditions than HS. We show that vestibular guided self-motion perception is strongly influenced by rotational movements, supporting central canal-otolith integration hypothesis. Self-motion perception is significantly impaired towards both sides in patients with unilateral vestibular hypofunction.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-25342-4.

Impairments of the upper limbs have significant impact on patients with neuromotor disease and require physical rehabilitation to reduce their effects. A RFID (Radio Frequency IDentification) system has been adapted to the use in occupational therapy aimed at improving the performance of Activities of Daily Living (ADLs). This system could be used to drive and monitor the performance of the patient during specific exercises by computing kinematic variables leveraging on the available RF parameters. In order to ascertain the feasibility of the project, we have developed and tested a method to estimate the length of the path covered by a moving RFID antenna, representing the patient’s hand, with respect to a fixed RFID tag, representing the target to be reached. Simple rotational and translational movements of the RFID antenna were performed and recorded with a movement analysis system. Simultaneously, the RSSI and phase signals were acquired from the RFID system. The phase variations were used to compute the variations of the antenna-tag distance and the path length. The measures obtained from the two systems were compared. The results show that the measure of the path length was reliable in translational movements when there was no relative antenna-tag angle, and in rotational movements. In case of translational movements with relative antenna-tag angle, inaccurate measurements are obtained.

Simulations of low-frequency vibration pattern at the inner ear for activation of the vestibular system.