Roll Rate Research Articles

On the Skill of Balancing While Riding a Bicycle.

Humans have ridden bicycles for over 200 years, yet there are no continuous measures of how skill differs between novice and expert. To address this knowledge gap, we measured the dynamics of human bicycle riding in 14 subjects, half of whom were skilled and half were novice. Each subject rode an instrumented bicycle on training rollers at speeds ranging from 1 to 7 m/s. Steer angle and rate, steer torque, bicycle speed, and bicycle roll angle and rate were measured and steering power calculated. A force platform beneath the roller assembly measured the net force and moment that the bicycle, rider and rollers exerted on the floor, enabling calculations of the lateral positions of the system centers of mass and pressure. Balance performance was quantified by cross-correlating the lateral positions of the centers of mass and pressure. The results show that all riders exhibited similar balance performance at the slowest speed. However at higher speeds, the skilled riders achieved superior balance performance by employing more rider lean control (quantified by cross-correlating rider lean angle and bicycle roll angle) and less steer control (quantified by cross-correlating steer rate and bicycle roll rate) than did novice riders. Skilled riders also used smaller steering control input with less variation (measured by average positive steering power and standard deviations of steer angle and rate) and less rider lean angle variation (measured by the standard deviation of the rider lean angle) independent of speed. We conclude that the reduction in balance control input by skilled riders is not due to reduced balance demands but rather to more effective use of lean control to guide the center of mass via center of pressure movements.

High-Strength Carbon Nanotube Film from Improving Alignment and Densification.

A new method is reported for preparing carbon nanotube (CNT) films. This method involves the continuous production of a hollow cylindrical CNT assembly and its condensation on a winding drum. The alignment and densification of CNTs in the film are improved by controlling the winding rate and imposition of mechanical rolling, respectively. The prepared film has a strength of 9.6 GPa, which is well above those for all other man-made films and fibers.

Optimum rolling ratio for obtaining {001} recrystallization texture in Ti–Nb–Al biomedical shape memory alloy

The rolling rate (r) dependence of textures was investigated in the Ti–26Nb–3Al (mol%) alloy to reveal the conditions required to form the {001}<110> recrystallization texture, which is a desirable orientation for the β-titanium shape memory alloy. {001}<110> was the dominant cold-rolling texture when r=90% and it was transferred to the recrystallization texture without forming {112}<110>, which is detrimental for the isotropic mechanical properties of the rolled sheet. A further increase in r resulted in the formation of {112}<110> in both rolling and recrystallization textures. Therefore, r should be controlled to form only the {001}<110> rolling texture, because the {112}<110> texture can overwhelm the {001}<110> texture during recrystallization.

Lateral roll control of vehicle based on UKF and sliding model control

A 3-DOF dynamical model of vehicle is built in this paper by using MATLAB/Simulink. Considering nonlinear tyre performance, the magic formula tyre model is used to improve the accuracy of the model. For the difficulty of measuring the roll angle and roll rate, an observer for the roll angle and roll rate based on the dynamical model of vehicle and kinematic relations is designed in this paper, tracking the roll angle and roll rate in the process of driving based on the easily measured status parameters, using unscented Kalman filter. Then, this method is tested through experiments. Finally, based on the estimated roll angle and roll rate, a roll stability controller based on the sliding model variable structure control theory is designed.

Flight mechanics and control of escape manoeuvres in hummingbirds. I. Flight kinematics.

Hummingbirds are nature's masters of aerobatic manoeuvres. Previous research shows that hummingbirds and insects converged evolutionarily upon similar aerodynamic mechanisms and kinematics in hovering. Herein, we use three-dimensional kinematic data to begin to test for similar convergence of kinematics used for escape flight and to explore the effects of body size upon manoeuvring. We studied four hummingbird species in North America including two large species (magnificent hummingbird, Eugenes fulgens, 7.8 g, and blue-throated hummingbird, Lampornis clemenciae, 8.0 g) and two smaller species (broad-billed hummingbird, Cynanthus latirostris, 3.4 g, and black-chinned hummingbirds Archilochus alexandri, 3.1 g). Starting from a steady hover, hummingbirds consistently manoeuvred away from perceived threats using a drastic escape response that featured body pitch and roll rotations coupled with a large linear acceleration. Hummingbirds changed their flapping frequency and wing trajectory in all three degrees of freedom on a stroke-by-stroke basis, likely causing rapid and significant alteration of the magnitude and direction of aerodynamic forces. Thus it appears that the flight control of hummingbirds does not obey the 'helicopter model' that is valid for similar escape manoeuvres in fruit flies. Except for broad-billed hummingbirds, the hummingbirds had faster reaction times than those reported for visual feedback control in insects. The two larger hummingbird species performed pitch rotations and global-yaw turns with considerably larger magnitude than the smaller species, but roll rates and cumulative roll angles were similar among the four species.

A Simplified Adaptive Backstepping Control of Aircraft Lateral/Directional Dynamics

Abstract A simple approach is proposed in this paper to control lateral/directional dynamics of Unmanned Aerial Vehicles (UAVs). The approach uses backstepping technique to design a lateral/directional controller. As the aerodynamics coefficients are not accurately available for the whole flight regime, we propose an adaptive design to learn and control unknown dynamics. The proposed approach provides satisfactory performance in tracking reference in roll rate using aileron and in maintaining sideslip angle to zero value using rudder. The design is validated on the six degrees of freedom model with the effect of actuator saturation.

Attitude estimator for spinning aircraft using earth infrared radiation field

The continuous improvement in diversification, new-type orientation and low cost of navigation control system, the accurate measurement of the spinning aircraft flight attitude parameters has becomes a more and more urgent task. In view of the above problems, a novel attitude estimator for the spinning aircraft is proposed by using earth infrared radiation field. The attitude estimation system possesses several key advantages over the current designs in low cost, no need of moving parts, and being free from reliance on GPS or other state feedback. Firstly, the mechanism of earth infrared radiation field is described in detail, and an 8-14 m atmospheric window is selected as the study object. The land surface infrared radiation is calculated by the land surface temperature and emissivity. The sky infrared radiation is calculated through layered atmosphere by combing with the sky emissivity and infrared atmospheric transmittance. According to the calculations of land surface infrared radiation and sky infrared radiation, the mathematical model of earth infrared radiation field is established by combining with propagation law of infrared radiation in the atmosphere. Then the measurement model of thermopile sensors is derived, after analyzing the motion feature of spinning aircraft during the flight. The thermopile sensors convert the observed infrared radiation into an electrical signal well suited for onboard data acquisition. To explore the inner link between the thermopile sensor output and the spinning aircraft attitude information, the characteristics of the sensor output under different attitude angles and fields of view are studied. When the thermopile sensor characteristics are included, the fully developed model can be used to generate accurate sensor output as a function of attitude angle. Finally, the installation of the thermopile sensors on the spinning aircraft is designed, and the measurement model of onboard thermopile sensor is established. In order to improve the accuracy of attitude measurement, an extended Kalman filter is developed, which enables the estimating of real-time attitude angles and roll rate by using solely three-axis thermopile sensors as feedback. The result indicates that by using this high accurate algorithm, the pitch angle estimation error is within 0.02, the roll angle estimation error is within 0.1 and the roll rate estimation error is within 1 rad/s. The detection system is simple and practical, works stably, and can meet the requirements for spinning projectile attitude measurement. The attitude estimation system will provide a new method and theory for further developing the spinning aircraft state detection.

Analytical Model for the Wide-Strip Rolling Mills Working Rolls Wear-Out Failures

The paper proposes a mathematical model for the gradual shape deterioration of wide-strip rolling mills working rolls active generatrixes subject to wear within the working zone during tandem rolling strips of a specified gauge. While modeling, the authors have determined the theoretical dependency needed to estimate the mean life of working rolls according to the transverse strip gauge interference criterion. Gauge interference of tandem-rolled strip transverse section shall be derived from the sum of the values of current shape of upper and lower working rolls active generatrixes, which are calculated based on strip width. In its turn, an active section of each roll shall be calculated for every following strip as a difference between the current roll radius values at the crown middle and that above/below the strip edge, while the shape deterioration rate of active roll generatrixes shall be defined by the difference between the roll wear rates in these sections. To estimate the rate of roll wear during rolling every following strip of the specified gauge, the base dependency of the structure-energy concept describing wear of stationary tribocouplings is used, which has been obtained by simultaneous solution of fundamental equations of molecule-mechanical and structure-energy friction theories. The moment of working roll failure (expected life) is determined based on the condition of achieving the nominal limit by gauge interference of a current strip.

Autonomous UAV controlled collision landing via eye-in-hand visual servoing

Catastrophic damage to fixed-wing unmanned aerial vehicles (UAV) is most likely to occur during the landing stage. Vision-based autonomous landing methods for small UAV have been proposed in literature to address the issue. This paper improves on previous work on vision-based landing via a controlled collision with a large inflatable airbag. In the proposed method the UAV steers towards a large, multi-coloured, dome-shaped airbag using visual feedback obtained from a UAV-mounted camera. A multi-colour airbag is proposed to facilitate a robust and efficient colour-based detection method for real-time detection of the dome in images. A proposed visual servoing controller translates the dome location into desired pitch and yaw rate commands to achieve an exponential decay of the image error. A model predictive UAV controller that achieves desired roll and yaw rates is designed and tested in simulations. The lateral and longitudinal UAV dynamics were decoupled and a linear discrete state space model of the dynamics was obtained via system identification. The proposed dome landing method has been implemented on the FlightGear flight simulator and has presented successful landings in simulations over multiple trials.

Simple Adaptive Delta Operator Aircraft Flight Control for Accommodation of Loss of Control Effectiveness

A new proof for stability of delta operator simple adaptive control is presented in terms of a set of Linear Matrix Inequalities (LMIs). The paper shows how to design a feedforward gain to satisfy the LMIs over a polytope of loss of control effectiveness failures. The MATLAB Robust Control Toolbox is used to find the feedforward gain with the smallest norm that satisfies the LMIs. Examples are presented of the F/A-18 aircraft and the Innovative Control Effectors (ICE) tailless aircraft that show the design of a feedforward gain for a loss of control effectiveness in any one control effector. The designs use a fixed eigenstructure assignment controller for an inner loop augmented with the simple adaptive controller. Simulations of both aircraft include simultaneous loss of control effectiveness failure and lateral wind gust. Simulation results for the F/A-18 aircraft show that the adaptive controller achieves almost perfect tracking whereas the nonadaptive controller cannot achieve a coordinated turn when an aileron failure occurs. The ICE tailless aircraft uses sideslip, washed-out stability axis yaw rate, and stability axis roll rate feedback for both the inner loop eigenstructure assignment controller and the simple adaptive controller. However, the adaptive controller also uses bank angle feedback. Simulation results for the ICE tailless aircraft show that the adaptive controller achieves almost perfect tracking whereas the nonadaptive controller diverges when an all moving tip failure occurs.

In-flight testing of loop thermosyphons for aircraft cooling

A novel design for a heat exchanger was experimentally evaluated in an Embraer test aircraft on the ground and in-flight conditions. The prototype was qualified for flight after constrained acceptance tests. The design consisted of two condensers, linked to one shared evaporator by two parallel loop thermosyphons. Water was used as the working fluid owing to its high figure of merit and because other fluids could represent a hazard in the case of leakage. During the flight, real tests conditions, which could not be set at laboratory, were evaluated. The air stream on the external side of the fuselage and the air conditioning system served as heat sinks. The tests were conducted at flight Mach numbers of around 0.78 and at altitudes of up to 40,000 ft. It was shown that the roll angle, angular velocities (pitch, yaw and roll rates) and aircraft accelerations did not affect the thermal performance of the prototype. The pitch angle, however, can affect the prototype performance by avoiding the contact between the working fluid and the heating element. Efficient performance of thermosyphon technology was also shown in freezing conditions. The heat exchanger system allows increasing aircraft refrigeration capacity during flight and on ground.

State transformation-based dynamic visual servoing for an unmanned aerial vehicle

abstractIn this paper, we propose a visual servoing control for a quadrotor unmanned aerial vehicle (UAV) which is based on a state transformation technique. The UAV is equipped with a single downwards facing camera, and the motion control objective is the regulation of relative displacement and yaw to a stationary visual target located on the ground. The state transformation is defined by a system of partial differential equations (PDEs) which eliminate roll and pitch rate dependence in the transformed image feature kinematics. A method for computing the general solutions of these PDEs is given, and we show a particular solution reduces to an established virtual camera approach. We treat point and line cases and introduce image moment features defined in the virtual camera image plane. Robustness of the control design is improved by accounting for attitude measurement bias, and uncertainty in thrust gain, mass, and image feature depth. The asymptotic stability of the closed-loop is proven. The method is based on a simple proportional-integral-derivative (PID) structure which can be readily implemented on-board. Experimental results show improved performance relative to previous work.

Model-Based Estimation for Vehicle Dynamics States at the Limit Handling

This technical brief proposes a new model-based estimation method for the vehicle sideslip angle, yaw rate, roll angle, and roll rate using unscented Kalman filter (UKF). Since a vehicle wheel could potentially lift off the ground during the limit handling, a switched vehicle roll dynamics model (wheel lift and no wheel lift) is developed and integrated within the proposed model-based estimation approach considering the availability of wheel speed sensor. The simulation results and analyses demonstrate the performance enhancement of the proposed estimation method over the method not considering wheel lift during the limit handling.

The Electoral Costs of Party Agenda Setting: Why the Hastert Rule Leads to Defeat

This study demonstrates that unconditional blocking of bills opposed by a majority of the majority party—as implied by the party cartel model and advocated by former Speaker Dennis Hastert—can produce conditions in which the majority party loses popular support and loses elections. The theoretical analysis and empirical results imply that the use of negative agenda power to block bills is circumscribed by this risk of electoral defeat. As a result, the opportunity for effective negative agenda control is conditional on majority party issue advantage, party polarization, and the distribution of status quo locations. In particular, majority party roll rates should sometimes be nonzero, blocking increases the odds of majority party defeat in House of Representatives elections, and policy change is most likely on issues with status quo that the model suggests are the riskiest to block.

Inflation with a constant rate of roll

We consider an inflationary scenario where the rate of inflaton roll defined by ̈ϕ/H ϕ̇ remains constant. The rate of roll is small for slow-roll inflation, while a generic rate of roll leads to the interesting case of ‘constant-roll’ inflation. We find a general exact solution for the inflaton potential required for such inflaton behaviour. In this model, due to non-slow evolution of background, the would-be decaying mode of linear scalar (curvature) perturbations may not be neglected. It can even grow for some values of the model parameter, while the other mode always remains constant. However, this always occurs for unstable solutions which are not attractors for the given potential. The most interesting particular cases of constant-roll inflation remaining viable with the most recent observational data are quadratic hilltop inflation (with cutoff) and natural inflation (with an additional negative cosmological constant). In these cases even-order slow-roll parameters approach non-negligible constants while the odd ones are asymptotically vanishing in the quasi-de Sitter regime.

Design of Linear Kalman Filter Based Parameter Estimator for a Micro Air Vehicle

This paper presents a design of parameter estimator for a Micro Air Vehicle (MAV) named Sarika-1. Estimator is needed in applications where all parameters cannot be measured directly due to various reasons. In this work, suitable linear Kalman filter estimator is designed for the longitudinal and lateral dynamics of Sarika-1.The Linear Discrete Kalman filter is designed to estimate its longitudinal state variables viz. angle of attack, forward velocity, pitch rate and pitch angle and the lateral state variables viz. Side slip angle, roll rate, yaw rate, and bank angle. Filter is designed in MATLAB and is verified using its offline simulation. For the simulation, the measurement data of pitch rate and normal acceleration collected at the time of real flight are used for longitudinal dynamics and lateral acceleration, roll rate and yaw rate collected at the time of real flight are used for lateral dynamics. It is found that the estimated values of the state variables matches well with the corresponding actual values.

Competing Agendas in Theories of Congress: Assessing Agenda Control Using Counterfactual Data

In legislative studies, a “roll rate” refers to the proportion of votes where a member or group of members is “rolled”—voting no on a measure that passes. Roll rates analysis is a potentially useful tool for evaluating arguments that the majority party in the House exercises influence by controlling what does and does not make it onto the agenda. Despite its promise, so far the use of roll rates to test these arguments has faced the problem of observational equivalence—that the predictions of partisan theories of agenda control are indistinguishable from those of arguments that have no place for parties. I address this problem by calculating party-less and partisan counterfactual roll rates data to pin down the predictions of these theories. This offers a powerful research design to evaluate observed roll rates from sample Congresses. The results provide intriguing evidence for partisan theories of the House agenda.

Integrated Line of Sight and Model Predictive Control for Path Following and Roll Motion Control Using Rudder

Roll motion control and path following are two representative marine control problems that have been traditionally treated separately. However, these two problems are closely coupled, as roll motion could cause negative effects on marine surface vessels during path following in seaways and path following actions could cause undesirable roll motion. In this article, an optimal controller is proposed for the integrated path following and roll motion control problem. The rudder, whose actuation amplitude and rate are both limited, is the only control input, while the cross-track error, heading angle, roll rate, and roll angle are the outputs that collectively define the performance of the system. This leads to a classic underactuated problem. Model predictive control is the natural choice for the solution, given its capability in dealing with constraints and multi-input‐multi-output system, and its design will be pursued in this article. Line of sight technique is used to extend the straight-line path following to arbitrary path following. A four degrees of freedom high-fidelity model is implemented as the simulation model, and the simulation results verify the effectiveness of the proposed controller. The influences of the control design parameters on system performance are investigated and the trade-offs between two key attributes, namely, the roll reduction and path following, are explored.

Integrated Line of Sight and Model Predictive Control for Path Following and Roll Motion Control Using Rudder

Roll motion control and path following are two representative marine control problems that have been traditionally treated separately. However, these two problems are closely coupled, as roll motion could cause negative effects on marine surface vessels during path following in seaways and path following actions could cause undesirable roll motion. In this article, an optimal controller is proposed for the integrated path following and roll motion control problem. The rudder, whose actuation amplitude and rate are both limited, is the only control input, while the cross-track error, heading angle, roll rate, and roll angle are the outputs that collectively define the performance of the system. This leads to a classic underactuated problem. Model predictive control is the natural choice for the solution, given its capability in dealing with constraints and multi-input-multi-output system, and its design will be pursued in this article. Line of sight technique is used to extend the straight-line path following to arbitrary path following. A four degrees of freedom high-fidelity model is implemented as the simulation model, and the simulation results verify the effectiveness of the proposed controller. The influences of the control design parameters on system performance are investigated and the trade-offs between two key attributes, namely, the roll reduction and path following, are explored.

Evaluation of Aircraft Sensor Failures Effects Using the Artificial Immune System Paradigm

This paper presents the development of simple models for the assessment of flight envelope reduction under aircraft sensor failures within the artificial immune system paradigm. The proposed methodology is expected to facilitate the design of on-board augmentation systems increasing aircraft survivability and improving operation safety. It demonstrates and exploits the capability of the artificial immune system to not only detect and identify aircraft subsystem abnormal conditions but also evaluate their impact and consequences. An artificial immune system built through simulation for a fighter aircraft is used in conjunction with a hierarchical multi-self strategy for estimating ranges of flight envelope relevant variables at post-failure conditions affecting angular rate sensors that are needed within the control augmentation system. Failure-specific algorithms correlated with the characteristics and dimensionality of self projections are developed for roll, pitch, and yaw rate sensors affected by bias. Metrics for the performance evaluation of the proposed approach are defined and used for successful demonstration in a motion-based flight simulator.