Roll angle measurement system based on triaxial magneto-resistive sensor

Aiming at large error when inertial devices measure the roll angle under high overload conditions,the article designs one kind of roll angle measurement system based on magneto-resistive sensor which calculates the roll angle by micro controller STM32.Experiment results of a triaxial turntable show that using magneto-resistive sensor to measure roll angle is feasible and of high accuracy,and it can calculate the roll angle of the conventional projectile with the error in 1°.

The influence of roll angles on unsteady aerodynamics in a canard-configured missile

During the initial stage of vertical launch,a missile may exhibit an uncertain roll angle(φ)and a high angle of attack(α).This study focuses on examining the impact of roll angle variations on the flow field and the unsteady aerodynamics of a canard-configured missile atα=75°.Simulations were performed using the validated k-ωSST turbulence model.The analysis encompasses the temporal development of vortices,the oscillatory characteristics of the lateral force,and the fluctuation of kinetic energy distribution within the framework of proper orthogonal decomposition(POD).The results indicate that the flow field surrounding the canardconfigured missile is characterized by inconsistent shedding cycles of Kármán-like and canard-separated vortices.A distinct transition zone is identified between these vortices,where vortex tearing and reconnection phenomena occur.With increasing roll angles from 0°to 45°,there is an observed shift in the dominant frequency of the lateral force from the higher frequency associated with Kármán-like vortex shedding to the lower frequency of canard vortex shedding.The shedding frequency of Kármán-like vortices corresponds to the harmonics of the canard vortex shedding frequency,indicative of a higher-order harmonic resonance.The frequency of the lateral force is observed to decrease with an increase in roll angle,except in configurations lacking distinct canard-separated vortices,which are characterized by a“+”shape.The POD analysis reveals that the majority of the fluctuation energy is concentrated in the oscillations and shedding of the canard-separated vortices,leading to pressure fluctuations that are primarily observed on the canard and the downstream region of the canard.

Remote Absolute Roll-Angle Measurement in Range of 180°Based on Polarization Modulation

Remote measurement of object orientation is often required in many applications.Out of the six degrees of freedom(DoF)that determine object orientation in space,the roll angle is the most difficult to measure using optical methods.In this letter,we propose a remote Stokes roll-angle sensor that measures roll angles from the detected Stokes vectors of modulated polarized light retroreflected from a sensing unit comprised simply of a retarder and a planar reflection mirror.Experimental results have shown that the proposed sensor can realize absolute roll angle measurement in an unprecedented range of 180°with a maximum absolute error of less than 0.25°and a measurement resolution of better than 0.01°.The proposed sensor adopts a coaxial design and takes the advantages of compactness,simplicity and low cost,and moreover,can be further expanded to a three-DoF angle sensor due to the sensitivity of the sensing unit to other two kinds of angles(pitch and yaw).

The effect of track alignment irregularity on wheel-rail contact geometry relationship in a turnout zone

The irregularity is a key factor affecting the wheel-rail contact geometry relationship. In this paper, we calculated the wheel-rail contact points at typical sections and obtained the longitudinal variation of the wheel-rail geometry relationship with the trace line method. The profile of the key rail sections was matched by cubic spline curve, and the shape interpolation was realized in non-controlling sections. The results show that the roll angles at each typical section increases gradually with the enlargement of track alignment irregularity. When the flange contact occurs, the roll angle increases dramatically. Proper track alignment irregularity towards the switch rail improves the structure irregularity of the turnout.

Estimating the Baseline Error of Wide-Swath Altimeters Using Nadir Altimeters via Numerical Simulation

The baseline roll and length errors for wide-swath altimeters are major error sources in sea surface measurements that exhibit strong spatial characteristics in the cross-track direction.These errors can be identified and estimated in accordance with height differences at crossover points generated with nadir altimeters after excluding the interference from other error sources.Most of the wide-swath altimeter baseline estimation methods considered only the roll error in previous studies.A numerical simulation was conducted in this study using nadir altimeters to estimate the roll and length errors simultaneously to provide a selectable scheme for baseline error estimation and correction for future wide-swath altimeters.Results based on the parameters of the surface water and ocean topography mission and Sentinel-3A show that the correlation coefficient of the roll error between the estimated and simulated values is 0.89,while the correlation coefficient of the length error is 0.85.The sea surface height root mean square error(RMSE)can be reduced from 12.18 cm to 6.45 cm based on the two estimated results.The estimation effect can be increased by using multiple nadir altimeters to form an observation constellation.The numerical simulation of the five nadir altimeter constellation shows that the correlation coefficients of the roll and length errors would increase to 0.97,which reduces the sea surface height RMSE to 2.88 cm.In addition,the stability of this method is indicated in simulation experiments,which introduce different degrees of sea state errors.

Photoelectric detection technology of laser seeker signals

The measurement of the rolling angle of the projectile is one of the key technologies for the terminal correction projectile.To improve the resolution accuracy of the rolling angle in the laser seeker weapon system, the imaging model of the detector, calculation model of the position and the signal-to-noise ratio(SNR) model of the circuit are built to derive both the correlation between the resolution error of the rolling angle and the spot position, and the relation between the position resolution error and the SNR. Then the influence of each parameter on the SNR is analyzed at large,and the parameters of the circuit are determined. Meanwhile, the SNR and noise voltage of the circuit are calculated according to the SNR model and the decay model of the laser energy. Finally,the actual photoelectric detection circuit is built, whose SNR is measured to be up to 53 d B. It can fully meet the requirement of0.5° for the resolution error of the rolling angle, thereby realizing the analysis of critical technology for photoelectric detection of laser seeker signals.

Time-Coordinated Path Following for Multiple Agile Fixed-Wing UAVs with End-Roll Expectations

This paper presents a control strategy for multiple unmanned aerial vehicle systems(multi-UAVs)time-coordinated path following with desired endpoint roll attitudes.It utilizes the strong maneuvering capabilities of agile fixed-wing UAVs and incorporates an end-roll expectation.The strategy consists of four steps:time-coordinated control,position control,roll angle planning and attitude control.The position and attitude controllers exhibit Lyapunov exponential stability.The time-coordinated controller addresses the synchronization problem by adjusting the speed based on the coordinated state to achieve progress adjustment.The position controller operates based on the cross-track error and altitude error in the Gravity-Referenced Moving frame.By employing an optimization approach and designing a penalty function,the roll angle sequence is computed.The attitude inner-loop control operates in the SO(3)space and allows for control of large deviations.High-fidelity simulation validates the effectiveness of the proposed method,with normalized coordination error and following error controlled within 2%and 1.2m.

Springback behavior of tailor rolled blank in U-shape forming

The springback of tailor rolled blanks with quenching and partitioning steels was investigated.In order to find out the springback behavior and related influence factors for the novel sheets,both experimental and simulation methods have been used to compare and analyze the springback characteristics of equal thickness blanks and tailor rolled blanks in U-channel forming.From the results,the overall springback angles of tailor rolled blanks at thin and thick sides are respectively 106.79° and 99.705°,which are both lower than those of the corresponding equal thickness blanks.Due to the existence of the thickness transition zone,the stress distribution in thin and thick sides of blanks is changed.The location of dangerous region in thin side of tailor rolled blanks is closer to the end of side,and the thick side moved to the middle of straight wall,which are different with the equal thickness blanks.Afterwards,the released quantitles of tangential stress and strain per unit section of blank are adopted to calculate relative springback angles and give novel evaluation criteria for qualitatively analyzing the amount of springback angles.By comparing the results,it shows that the tangential strain method is more suitable for the actual situation.

Robust multi-objective optimization of rolling schedule for tandem cold rolling based on evolutionary direction differential evolution algorithm

According to the actual requirements,profile and rolling energy consumption are selected as objective functions of rolling schedule optimization for tandem cold rolling.Because of mechanical wear,roll diameter has some uncertainty during the rolling process,ignoring which will cause poor robustness of rolling schedule.In order to solve this problem,a robust multi-objective optimization model of rolling schedule for tandem cold rolling was established.A differential evolution algorithm based on the evolutionary direction was proposed.The algorithm calculated the horizontal angle of the vector,which was used to choose mutation vector.The chosen vector contained converging direction and it changed the random mutation operation in differential evolution algorithm.Efficiency of the proposed algorithm was verified by two benchmarks.Meanwhile,in order to ensure that delivery thicknesses have descending order like actual rolling schedule during evolution,a modified Latin Hypercube Sampling process was proposed.Finally,the proposed algorithm was applied to the model above.Results showed that profile was improved and rolling energy consumption was reduced compared with the actual rolling schedule.Meanwhile,robustness of solutions was ensured.