Angular Velocity Measurements Research Articles

A Novel Attitude Angular Velocity Measurement Method Based on Mass Unbalance Vibration Suppression of Magnetic Bearing

In order to eliminate the influence of synchronous harmonic current caused by mass imbalance of magnetic bearing on attitude angular velocity measurement accuracy, a notch filter which can adjust the notch depth and center frequency is proposed. Firstly, the influence of synchronous harmonic current on the measurement accuracy of magnetically suspended control and sensitive gyroscope(MSCSG) is analyzed, and then a notch filter is designed which can adjust the notch depth and center frequency, and the measurement accuracy and stability of the system after eliminating synchronous harmonic current are analyzed. Simulation results show that the proposed method can effectively suppress the unbalance vibration torque and eliminate synchronous harmonic current. Finally, the correctness and effectiveness of the proposed method are verified by experiments. Experimental results show that the proposed method can reduce the vibration torque by 50% and improve the measurement accuracy of attitude angular velocity significantly.

Between/within-session reliability of spinal kinematic and lumbar muscle activity measures in patients with chronic low back pain and asymptomatic individuals

BackgroundLongitudinal research is required to better understand the role of spinal movement alterations in chronic low back pain (CLBP). To this end, it is critical to assess the between-session reliability of spinal movement measures. Research questionWhat is the within/between-session reliability of spinal movement measures in patients with CLBP and asymptomatic controls? MethodsSpinal movement was recorded prospectively during two sessions, a week apart, for 20 patients with CLBP (60% male; 40.0 ± 12.3 years old) and 20 asymptomatic individuals (55% male; 38.2 ± 10.9 years old). Sagittal-plane angular amplitude and angular velocity at the lower lumbar, upper lumbar, lower thoracic and upper thoracic joints, as well as maximal erector spinae activity were measured during five daily-activity tasks. In addition, task-independent measures were obtained by averaging the measures across tasks. The Intraclass Correlation Coefficient (ICC 2,1) and the minimal detectable change (MDC) were calculated. Pearson correlation was used to compare task-independent and task-specific measures. ResultsBetween-session ICCs in patients with CLBP were mostly moderate to good for maximal angular amplitude and erector spinae activity measures. Lower ICCs were observed for range of angular motion and angular velocity measures (42% of ICCs < 0.5). Median MDCs were 9.6°, 18.3°/s and 1.0% for angular amplitude, angular velocity and erector spinae activity measures, respectively. The reliability of task-independent and task-specific measures was strongly correlated (r = 0.91, p < 0.001). SignificanceSagittal-plane maximal angular amplitude and erector spinae activity measures during various daily-activity tasks demonstrated mostly moderate to good between-session ICCs. However, relatively large MDCs suggested that important changes are needed to be detectable. Task-independent measures reported similarly acceptable ICCs than task-specific measures, supporting their use to describe spinal movement.

Postfault Direct Field-Oriented Control of Induction Motor Drive Using Adaptive Virtual Current Sensor

Electric drives immune to failures of selected elements of the power system or measuring sensors have been the subject of research in recent years, due to the growing interest in systems with an increased level of safety. This article concerns the analysis of the direct field-oriented control induction motor drive after the failure of all stator current sensors. An adaptive virtual current sensor (AVCS) was used to estimate the stator current, based on the measurement of the motor angular velocity and the voltage in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{DC}\ (u_{\text{DC}})$</tex-math></inline-formula> of the voltage-source inverter. This article presents the possibility of improving the accuracy of stator current estimation using the original approximation of changes in rotor resistance depending on the drive operating point when the measurement information about the stator current has been lost. This approximation was determined experimentally during the normal operation of the drive using a rotor resistance estimator. The determined approximate lookup functions were used to adapt the rotor resistance in the AVCS during the drive system operation in a postfault mode. This approach has made it possible to significantly improve the accuracy of the stator current reconstruction, especially under low speeds and load torques, which was demonstrated in experimental studies <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.</b>

Characteristics of various sensor devices for a miniature resonant optical gyroscope

Subject of study. Using a ring resonator as an example, this paper describes the general operating principle for optical resonators, the characteristics of such resonators, and the relationship between resonator quality factor Q and gyroscope sensitivity. Several sensor devices (optical resonators) were compared for use in the development of a miniature resonant optical gyroscope. These optical resonators were of three different types: a fiber-optic resonator, a whispering gallery mode resonator, and an integrated optical resonator ring. Methodology. The fiber-optic resonator consists of two fiber-optic splitters spliced together, the whispering gallery mode resonator consists of a three-dimensional dielectric structure in which whispering gallery modes are excited, and the integrated optical resonator ring consists of an optical waveguide and closed loop mounted on a common substrate. The characteristics of the high-Q(Q=106−109) whispering gallery mode resonators and fiber-optic resonators were measured using a narrow-band scanning laser and an oscillograph. A simpler approach, with a broadband laser source and an optical spectrum analyzer, was used for the low-Q(Q&lt;106) integrated optical resonators. Main results. Values of Q=5.2×108, Q=4.3×106, and Q=1.1×104 were obtained for a MgF2 disk resonator, fiber-optic disk resonator, and integrated optical resonator, respectively. Practical significance. The whispering gallery mode resonator turns out to be the most promising of these sensor devices since it has the highest Q and the highest accuracy for angular velocity measurements. Fiber optic resonators are competitive but are more sensitive to temperature and external mechanical effects. Integrated optical resonators have the advantage of miniaturization and the ability to include temperature stabilization components and components that provide resistance to mechanical effects.

Vision‐based tracking control of quadrotor for a moving target with nonlinear angular velocity observer

AbstractIn this article, an automatic tracking process for unmanned aerial vehicle (UAV) system to follow the target with maneuverability is developed, and a vision‐based control method is proposed. At first, the image‐based visual servoing (IBVS) position control technology is applied without any prior target information for the algorithm practicability. Besides, consider the situation with unavailable angular velocity measurement, a thorough nonlinear attitude controller with an observer based on contraction is proposed. Finally, the whole UAV system stability is demonstrated to be uniformly ultimately bounded, and the bound can be arbitrarily small. Simulation and experiment results are presented to show effectiveness of the designed controller.

Geometric Formation Tracking of Quadrotor UAVs Using Pose-Only Measurements

In this brief, the problem of formation control of a swarm of quadrotor UAVs with a group leader using only position and attitude measurements is addressed. A distributed formation controller is proposed for the quadrotor team, which consists of an outer-loop position controller to achieve the desired formation without linear velocity measurements, and an inner-loop attitude controller to regulate the attitudes without angular velocity measurements. Two auxiliary dynamic systems driven by proper inputs respectively are designed to overcome the lack of linear and angular velocities. The position controller derived from the intermediary translational control inputs guarantees the boundedness of the actual thrust force inputs. The attitude controller is developed directly using rotation matrices to avoid the singularities of Euler-angles and the ambiguity of quaternions. The stability analysis is presented using Lyapunov stability theory on cascade systems, and the effectiveness of the proposed control strategy is demonstrated through numerical simulations.

Three-Dimensional Velocity Measurement Using a Dual Axis Millimeter-Wave Interferometric Radar

In this work, a method for directly measuring target velocity in three dimensions using a dual axis correlation interferometric radar is presented. Recent advances have shown that the measurement of a target's angular velocity is possible by correlating the signals measured at spatially diverse aperture locations. By utilizing multiple orthogonal baselines and using conventional Doppler velocity methods to obtain radial velocity, a full three-dimensional velocity vector can be obtained using only three receive antennas and a single transmitter, without the need for tracking. A $\text{41.8 GHz}$ dual axis interferometric radar with a $7.26\lambda$ antenna baseline is presented along with measurements of a target moving parallel to the plane of the radar array, and of a target moving with components of both radial and tangential velocity. These experiments achieved total velocity root-mean-square errors of $\text{41.01 mm}\cdot\text{s}^{-1}$ ($10.5\%$) for a target moving along a plane parallel to the array, and $\text{45.07 mm}\cdot\text{s}^{-1}$ ($13.5\%$) for a target moving with components of radial and tangential motion relative to the array; estimated trajectory angle RMSEs of $10.42^\circ$ and $5.11^\circ$ were achieved for each experiment respectively.

Study on the characteristics of a photonic crystal sensor with rectangular lattice based on bound states in the continuum

In this paper, a sensor model of a photonic crystal with a rectangular lattice is proposed and its sensing characteristics based on bound states in the continuum are studied using the finite element method. Using the different resonances of the rectangular lattice in two axes, the resonance line-width can be adjusted by the polarization direction of incident light. This structure can achieve a sensitivity of 148 nm RIU−1 and the figure of merit above 821 RIU−1, which shows a great potential in high-quality sensors, filter, laser line-width modulation as well as measurement of angle and angular velocity.

Fast-Exponential Sliding Mode Control of Robotic Manipulator With Super-Twisting Method

This brief addresses the trajectory tracking problem for robotic manipulators without angular velocity measurements in the presence of parameter perturbation and torque disturbance. A novel fast terminal sliding mode surface is developed to ensure global strong robustness and fast error convergence. Then, a high-order sliding mode observer (HOSMO) is constructed to estimate unknown joints’ angular velocities and the system lumped disturbance in a finite time. Chattering avoidance can be realized via the continuous control strategy based on super-twisting method. The finite-time arrival of sliding mode surface and fast-exponential convergence of the tracking error are strictly proved based on the Lyapunov stability theory. Finally, an example of a two-link robotic manipulator is provided. From the comparison with other control strategies, the advantages of proposed method are fully demonstrated.

Distributed Adaptive Attitude Synchronization of Multiple Spacecraft With Event-Triggered Communication

This article investigates the distributed adaptive attitude synchronization problem for multiple rigid spacecraft with unknown inertial matrices and event-triggered communication. Under a directed topology condition, two distributed event-based adaptive attitude synchronization schemes are proposed. By introducing a reference system for each spacecraft, a distributed adaptive control algorithm is first developed, based on which a group of rigid spacecraft can be synchronized at a common attitude with zero angular velocity. Then, the case without angular velocity measurements is considered. By redesigning the reference system and resorting to a pseudovelocity filter, an event-based adaptive output feedback attitude synchronization algorithm is presented. It is shown that with the proposed control schemes, all the closed-loop signals are uniformly bounded and the attitude synchronization can be achieved, while Zeno behavior in each spacecraft can be excluded. Simulation results are provided to illustrate the effectiveness of the proposed control schemes.

Angular velocity measurement with wide range based on dual-comb Sagnac interferometer.

Interferometric fiber optic gyroscopes are widely used in spacecraft, navigation, and autopilot and missile systems due to their high accuracy and fast speed. However, the dynamic measurement range is generally limited to a small value. In this paper, an angular velocity measurement system based on a dual-comb Sagnac interferometer is proposed. The theoretical dynamic range can reach the order of 108 deg/s, which is remarkably superior to that of the conventional fiber optic gyroscopes. To the best of our knowledge, this is the first demonstration of a dual-comb-based passive fiber optic gyroscope system, offering an attractive tool for measuring angular velocity with large dynamic range.

Dynamical Modelling and Vibration Analysis of the Non-coplanarity of the Orthogonal Support of Gyrowheel

In the engineering implementation of gyrowheel, the influence of orthogonal support non-coplanar is inevitable. However, when the gyrowheel is used for satellite inertial angular velocity measurement, this non-ideal factor will inevitably have an adverse impact on the accuracy of angular velocity measurement. Therefore, the dynamic model of gyrowheel with non-coplanar orthogonal support is established, and the influence of the non-coplanarity support on the vibration frequency is analysed. Finally, the correctness of this research is verified by simulation.

Attitude Control for a Rigid-Body With Dynamic Disturbance Based on Angular Velocity Observer

In this paper, we propose a geometric control law for attitude robust control problem of a rigid body system without angular velocity measurement. We suppose there is a disturbance related to angular velocity and attitude in the system. Under appropriate controllers, the estimated values of attitude and angular velocity obtained by an angular velocity observer can converge to the true values exponentially by the Lyapunov stability theorem. Furthermore, by modifying an adaptive law for the inertia matrix, the exponential stabilization of the system can still be guaranteed without the knowledge of the true inertia matrix with the same way. The angular velocity observer we designed ensures the global exponential stability in the system. Finally, the proposed theoretical results are verified by our simulation examples.

Sensor Fusion Based on Embedded Measurements for Real-Time Three-DOF Orientation Motion Estimation of a Weight-Compensated Spherical Motor

This paper presents a sensor fusion method to estimate the three degrees-of-freedom (3-DOF) orientation of a ball-joint-like permanent-magnet spherical motor (PMSM) and its angular velocity using embedded sensors that simultaneously measure the existing magnetic flux density (MFD) field and the back-electromotive-force (back-emf), which serve as inputs to a Kalman filter (KF) based sensor fusion system for full state estimation of 3-DOF angular displacement and velocity in real-time. Formulated in quaternion representation, the effectiveness and accuracy of the sensor fusion system consisting of an artificial neural network (ANN) that determines the 3-DOF orientation from measured MFD and an emf-velocity model, has been experimentally evaluated on an additive manufactured prototype PMSM- Weight Compensating Regulator (WCR) by comparing the estimated orientation and angular-velocity with that measured by two most used methods, optical laser-beam system, and inertial measurement unit (IMU). The experimental findings demonstrate that the KF-based sensor fusion effectively overcomes the MFD sensor noise and IMU drift problems and is capable of simultaneous measurements of 3-DOF angular displacement and velocity with improved accuracy relative to the popular IMU measurements.

Optical flow-based angular rate sensor fault detection on UAVs*

The paper first extends the previous work of the authors dealing with optical flow-based angular rate estimation. Extension means consideration of camera position and orientation relative to the UAV body system (non-aligned camera). After the extension the proposed method is evaluated with virtual reality (Unreal-Carla) image sequences considering simulated aircraft flight trajectories and different frames per second (fps) rates. Based-on the results showing high fps requirements for agile flight scenarios a reversed method is proposed for angular rate sensor fault detection considering the integration of system dynamics based-on angular rate and velocity measurements and comparing the predicted image feature positions with the measured ones. The feature position differences are the error measures completed with up-down counters. The results are promising however, only basic evaluation of the proposed methods is done paving the way for detailed evaluation and development outlined in the conclusion.

Optimization of a Suspension of a Micromechanical Accelerometer in an Angular Velocity Measurement Unit

Optimization of the suspension of the micromechanical accelerometer, which is a part of an angular velocity measurement unit, was considered. This problem was faced because of the need to improve the design of the existing device to meet new technical requirements. Shock loads up to 1 000 g exceed ultimate loads for micromechanical accelerometers by several orders of magnitude. During the study, it turned out that the measurement unit shell works as a resonator, so the shock loads on the micromechanical accelerometer can even exceed 1 000g. In this case, suspensions of the micromechanical accelerometer are deformed in the plane of the accelerometer, which causes their destruction. The solution to this problem was hampered by the strict limits on the overall dimensions of the device. The existing shock dampers that could absorb such shock loads simply did not fit into the attachment points. Therefore, an original spring was designed and manufactured for this purpose. At the final stage, an additional system of passive heat outlets from the accelerometer to the device shell was designed and installed.

Reliability and validity of expert assessments of hand-wrist physical exposures.

General population job-exposure matrices (JEMs) based on expert assessments of physical exposures may be valuable tools for studying occupation-related musculoskeletal disorders. Wrist-hand JEMs are few and the reliability and validity of expert assessments of wrist-hand exposures is uncertain. We examined intra- and inter-rater reliability of ratings of five experts of hand-wrist repetition, deviation, force, vibration, and computer work in 33 jobs selected to represent a large exposure variation. The validity of ratings of hand-wrist repetition was examined by comparison with electro-goniometer measurements of wrist angular velocity and mean power frequency (MPF), and the validity of hand-wrist deviation by comparison with goniometer measurements of range of motion (ROM). Intra-rater test-retest and inter-rater Spearman correlation coefficients controlling for rater effects, varied between 0.70 and 0.87. Corresponding kappa statistics of overall agreement showed similar high values, except for wrist deviation (kappa = 0.50). Regression analyses showed strong positive associations between expert assessments of repetition and goniometer measurements of wrist angular velocity (R2 = 0.56, p < 0.0001) and MPF (R2 = 0.37, p < 0.0003), while expert ratings of wrist deviation showed a weak statistically nonsignificant association with goniometer measurements of ROM (R2 = 0.032, p = 0.34). The reliability of expert assessments of wrist-hand physical exposures was high. Compared to goniometer measurements, the validity of assessments of wrist-hand repetition was also high, but it was low for assessments of wrist-hand deviation. The results are encouraging for establishing a hand-wrist JEM, but the results for wrist deviation emphasize that expert assessments should be validated against objective measurements.

Remote angular velocity measurement by the cascaded rotational Doppler effect.

The rotational Doppler effect has attracted extensive attention, caused by the angular momentum and energy exchange between rotating objects and waves. However, most previous works used a simple rotation frame, which made use of only a single-round angular momentum and energy exchange. We propose and demonstrate a frame containing a spiral phase plate cascaded with rotating targets to make an amplification of the traditional Doppler shift, and reduce the diffusion of orbital angular momentum modes by half, which means the distance of practical application is doubled theoretically. To this end, an experiment is carried out to verify the frame. It shows a more practical, convenient, and non-destructive method to measure the rotational speed of a remote target.

A phase-to-intensity strategy of angular velocity measurement based on photonic orbital angular momentum

Abstract Recently, orbital angular momentum (OAM) has been adopted to measure the shape of static objects and the translation motion of moving objects in optical remote sensing. Most of these studies rely on measuring the intensity variation of OAM beams. However, the OAM intensity does not change with the rotation of the spinning object, but its phase changes. The phase variation is proved to be proportional to the object’s angular velocity. Since a rotating object will cause the OAM phase dependent on time, the OAM phase needs to be measured instantaneously, to support the OAM-based angular velocity measurement. In this work, we report a scheme to measure the angular velocity of a spinning object using a photonic OAM phase spectrum. A phase-to-intensity strategy is implemented to enable the real-time multi-OAM phase measurement, in which the phase can be determined with the intensities of four focal spots in a two-dimensional array generated by a phase-only spatial light modulator. The experimental results show that the average error of the measured angular velocity could be under 2.45% by detecting the phase of two OAM modes. This OAM-based angular velocity detection method provides a complementary approach to characterize the rotational Doppler effect, especially for slow angular motion.

Dual Quaternion Particle Filtering for Pose Estimation

This article presents a particle filter for pose estimation using unit dual quaternion kinematics. The eight-parameter unit dual quaternion is used for global representation of the pose, whereas the six parameters of the dual modified Rodrigues parameters (MRPs) are used for local pose representation in the state-space model. The dual MRPs enable estimates of the mean and the covariance to be calculated from the particles without violating the algebraic constraint of the unit dual quaternion. For verification of the filter and comparison with state of the art, we consider pose measurements available in the form of unit dual quaternions. Angular velocity and specific force measurements from a body-mounted inertial measurement unit are also considered in the filtering. We show through simulations that the suggested particle filter has comparable accuracy with a previously proposed unscented Kalman filter based on unit dual quaternions. We also consider a practical application where the pose of an arbitrary rigid object is estimated using a sequence of point clouds from a 3-D camera. A model point cloud of the object is displaced with the unit dual quaternion associated with each particle, and a fitting score is calculated between the displaced model point cloud and the measured point cloud from the 3-D camera. The likelihoods of the fitting scores are calculated from an exponential distribution and are used to update the weights of the particles. The system was verified in an experiment where the motion of a swinging payload hanging from a crane was estimated using a 3-D camera.