Lateral Disturbance Research Articles

Using an inerter-based suspension to improve both passenger comfort and track wear in railway vehicles

ABSTRACTThere is an increasing desire in the railway industry to improve the longevity of wheels and rails without reducing performance in other ways (e.g. worsening passenger comfort). One way of reducing track and wheel wear is to reduce the primary yaw stiffness, significantly diminishing the costs associated with maintenance and emergency repairs, resulting however in reduced passenger comfort and high-speed stability. This paper, using a two-axle railway vehicle case study, demonstrates the potential of using passive, inerter-based suspensions to concurrently improve ride comfort and reduce track wear. The industrial parameter is used to quantify the frictional energy lost at the contact patch under curving conditions, and the lateral RMS carbody acceleration is used to quantify passenger comfort under straight running conditions, with lateral track disturbances taken from real track data. Optimisation results conclude that, with the default yaw stiffness value, compared with the default spring-damper configuration in the primary lateral suspension, employing beneficial inerter-based configurations can improve passenger comfort by up to 43%. If the yaw stiffness is reduced such that the track wear is improved, similar improvements in passenger comfort can still be achieved with lateral inerter-based suspensions; for example, an improvement of 33% can still be achieved with a 50% reduction in yaw stiffness. Furthermore, when an inerter-based lateral suspension is used together with a Hall-Bush longitudinal suspension, the passenger comfort rises to 40%, which relates to a 25% improvement when compared with a non-inerter lateral plus Hall-Bush longitudinal setup.

3D closed-loop swimming at low Reynolds numbers

In this paper, the mobility matrix of helical microswimmers is investigated to compute the magnetic torque as a function of the angular velocities of the helical robot to achieve a 3D path following in closed-loop. Thus, the helical swimmer kinematics are expressed in the Serret–Frenet frame considering the weight of the robot and lateral disturbances using the compensation inclination and direction angles, respectively. A new chained formulation is used to design a stable controller. The approach is simple and quite general and can be used for different non-holonomic autonomous systems. The 3D path following is validated by presenting experimental results using a scaled-up helical microswimmer actuated magnetically. Different trajectories were tested: a spatial straight line, a helix trajectory, and an inclined sinusoidal trajectory. Several conditions have been tested experimentally, namely: different velocity profiles, compensation inclination angles, liquid viscosities, control gains and boundary effects, and their impact on the performance of the path following. To illustrate the robustness and accuracy of the visual servo control to disturbances presenting in the environment such as the magnetic field gradient and boundary effects, it is compared with the open-loop control. The results show the robustness of the controller and a submillimetric accuracy during the path following.

Interactive Control Paradigm-Based Robust Lateral Stability Controller Design for Autonomous Automobile Path Tracking With Uncertain Disturbance: A Dynamic Game Approach

Stability as well as robustness is the major concerns in the design of a trajectory tracking controller for an autonomous vehicle. In this paper, a novel lateral stability controller design for vehicle path tracking is developed. First, using dynamic game theory as a general framework, vehicle lateral stability can be viewed as a dynamic difference game so that its two players, namely, the active front steering (AFS) system and active rear steering (ARS) system can work together to provide more stability for vehicle path tracking control. The interactive steering control strategies between AFS and ARS are obtained by noncooperative closed-loop feedback Stackelberg game theory to ensure optimal performance for vehicle path tracking. Then, based on the proposed path-following shared control paradigm, by applying the method of zero-sum game theory, a finite-time robust regulator is developed to make the interaction model more robust to uncertain lateral disturbances. Finally, double-lane change and serpentine driving condition with and without uncertain time-varying lateral disturbance are used to evaluate the proposed control algorithm. Simulation and hardware-in-loop implementation results show that the proposed shared control paradigm based robust path-tracking controller can robustly provide better lateral stability when time-varying lateral disturbances are bounded.

Underwater docking of an under-actuated autonomous underwater vehicle: system design and control implementation

Underwater docking greatly facilitates and extends operation of an autonomous underwater vehicle (AUV) without the support of a surface vessel. Robust and accurate control is critically important for docking an AUV into a small underwater funnel-type dock station. In this paper, a docking system with an under-actuated AUV is presented, with special attention paid to control algorithm design and implementation. For an under-actuated AUV, the cross-track error can be controlled only via vehicle heading modulation, so both the cross-track error and heading error have to be constrained to achieve successful docking operations, while the control problem can be even more complicated in practical scenarios with the presence of unknown ocean currents. To cope with the above issues, a control scheme of a three-hierarchy structure of control loops is developed, which has been embedded with online current estimator/compensator and effective control parameter tuning. The current estimator can evaluate both horizontal and vertical current velocity components, based only on the measurement of AUV’s velocity relative to the ground; in contrast, most existing methods use the measurements of both AUV’s velocities respectively relative to the ground and the water column. In addition to numerical simulation, the proposed docking scheme is fully implemented in a prototype AUV using MOOS-IvP architecture. Simulation results show that the current estimator/compensator works well even in the presence of lateral current disturbance. Finally, a series of sea trials are conducted to validate the current estimator/compensator and the whole docking system. The sea trial results show that our control methods can drive the AUV into the dock station effectively and robustly.

Spatially Dependent Transfer Functions for Web Lateral Dynamics in Roll-to-Roll Manufacturing

Spatially dependent transfer functions for web span lateral dynamics which provide web lateral position and slope as outputs at any location in the web span are derived in this paper. The proposed approach overcomes one of the key limitations of the existing methods which provide web lateral position only on the rollers. The approach relies on taking the Laplace transform with respect to the temporal variable of both the web span lateral governing equation and the boundary conditions on the rollers, and solving the resulting equations. A general web span lateral transfer function, which is an explicit function of the spatial position along the span, is obtained first followed by its application to common guide configurations. The approach also significantly simplifies the consideration of shear (relevant to short spans), in addition to bending, which has been found to be difficult to handle in past studies. We first develop spatially dependent lateral transfer functions by considering only bending which is relevant to most web handling situations, and then add shear to the formulation and develop spatially dependent lateral transfer functions that include both bending and shear. Results from model simulations and pertinent discussions are provided. The spatially dependent transfer functions derived in this paper are a significant improvement over existing lateral transfer functions and provide mechanisms to analyze web lateral behavior within spans, study propagation of lateral disturbances, and aid in the development of closed-loop lateral control systems in emerging applications that require precise lateral positioning of the web.

Lateral Collision Avoidance Robust Control of Electric Vehicles Combining a Lane-Changing Model Based on Vehicle Edge Turning Trajectory and a Vehicle Semi-Uncertainty Dynamic Model

This paper presents a new control scheme for lateral collision avoidance (CA) systems to improve the safety of four-in-wheel-motor-driven electric vehicles (FIWMD-EVs). There are two major contributions in the design of lateral CA systems. The first contribution is a new lane-changing model based on vehicle edge turning trajectory (VETT) to make vehicle adapt to different driving roads and conform to drivers’ characteristic, in addition to ensure vehicle steering safety. The second contribution is vehicle semi-uncertainty dynamic model (SUDM), which is SISO model. The problem of stability performance without the information on sideslip angle is solved by the proposed SUDM. Based on the proposed VETT and SUDM, the lateral CA system can be designed with H∞ robust controller to restrain the effect of uncertainties resulting from parameter perturbation and lateral wind disturbance. Single and mixed driving cycles simulation experiments are carried out with CarSim to demonstrate the effectiveness in control scheme, simplicity in structure for lateral CA system based on the proposed VETT and SUDM.

Nonlinear modelling and dynamic stability analysis of a flexible Cartesian robotic manipulator with base disturbance and terminal load

Abstract. The flexible Cartesian robotic manipulator (FCRM) is coming into widespread application in industry. Because of the feeble rigidity and heavy deflection, the dynamic characteristics of the FCRM are easily influenced by external disturbances which mainly concentrate in the driving end and the load end. Thus, with the influence of driving base disturbance and terminal load considered, the motion differential equations of the FCRM under the plane motion of the base are constructed, which contain the forced and non-linear parametric excitations originated from the disturbances of base lateral and axial motion respectively. Considering the relationship between the coefficients of the motion differential equations and the mode shapes of the flexible manipulator, the analytic expressions of the mode shapes with terminal load are deduced. Then, based on multiple scales method and rectangular coordinate transformation, the average equations of the FCRM are derived to analyze the influence mechanism of base disturbance and terminal load on the system parametric vibration stability. The results show that terminal load mainly affects the node locations of mode shapes and mode frequencies of the FCRM, and the axial motion disturbance of the driving base introduces parametric excitation while the lateral motion disturbance generates forced excitation for the transverse vibration model of the FCRM. Furthermore, with the increase of the base excitation acceleration and terminal load, the parametric vibration instability region of the FCRM increases significantly. This study will be helpful for the dynamic characteristics analysis and vibration control of the FCRM.

Why trains stay on tracks

In this article, we give both qualitative and quantitative explanations of why a train stays on its track, in spite of perturbations that could cause it to derail. We show that train stability originates from the conical shape of the wheels, which gives rise to a restoring normal force in response to a lateral disturbance. We first demonstrate translational stabilization in a simple situation where the rails are assumed frictionless and the steering motion of the wheel is neglected. We then develop a more comprehensive model, taking friction and steering into account. We show that rolling friction couples the rotational motion to the translational motion, enhancing overall stability. Finally, we find approximate formulae for the parameters governing stability, and show good agreement with parameters of a real railway coach.

Nonlinear adaptive tracking for ground vehicles in the presence of lateral wind disturbance and parameter variations

In this paper we design a dynamic controller for the attitude control of a ground vehicle. This controller ensures the tracking of desired references, in the presence of uncertainties in the parameters describing the tire-road friction coefficient and the lateral tire stiffness, and in the presence of external perturbations, such as lateral wind. It incorporates some dynamics reconstructing the lateral vehicle velocity, often not directly measured. Finally, the proposed control scheme allows the identification of the unknown parameters and, at the same time, of the disturbance due to the lateral wind acting on the vehicle. The performance of the dynamic controller is evaluated making use of CarSim considering a challenging double steer maneuver.

Experimental study on heat transfer of upright pipes in cold regions

Laboratory experiments are conducted to investigate the heat transfer characteristics of upright pipes under periodic ambient temperatures. The results provide evidence to support the use of upright pipes in permafrost engineering. This paper presents two models with different inlet pipe diameters. The results indicate that the mean periodic temperatures at the bottom of the pipe and soil decrease with increasing freeze-thaw cycles and ultimately remain in a frozen state. Natural convection is the dominant mode of conducting heat exchange between the upright pipe and air. The inlet diameter greatly affects both the cold energy accumulation at the pipe bottom and the cooling efficiency. Furthermore, the lateral thermal disturbance distance of the upright pipe is approximately more than one fold of the inlet diameter. Therefore, the upright pipe enhances the cooling effect to the surrounding soil and is recommended for the cooling of permafrost foundations.

Validation of Vehicle Model Response with an Instrumented Experimental Vehicle

A steering aid system called active steering is evaluated by simulating different kinds of driving events. The main purpose of the steering system is to allow the driver control the vehicle independently. A full car vehicle model is simulated in Matlab/Simulink with 14 degree of freedom of equations which include the ride vehicle model and also the handling model. The steering angle is the input of the vehicle model that should be focused on. The angle of the steering system between the tires when turning the vehicle is taken in consideration. Simulations are made on different road conditions effect and also side wind disturbances. Different values are applied to the simulation to reduce the effect of the driving events. Therefore, these simulations results to provide a better improvement to the steering system. The aim for this work is to validate the vehicle response with an instrumented experiemental vehicle. Specific driving events in these simulations are the road adhesions and lateral side wind disturbances.

Optimal coupled and uncoupled fuzzy logic control for magneto-rheological damper-equipped plan-asymmetric structural systems considering structural nonlinearities

The main motivation of this paper is to examine the effect of structural nonlinearities on the engineering demand parameters (EDPs) of seismically excited controlled plan-asymmetric buildings equipped with magneto-rheological dampers. The development of a robust control algorithm for asymmetric buildings due to the randomness of ground excitations and their torsional response has always been a significantly challenging task in the vibrations control of structures. While the control algorithm in a simple approach could be designed ignoring the dependency of stiff and flexible edges of EDPs, the present research aimed also to develop a control strategy that mitigates simultaneously asymmetric edge responses of the structure using the multi-input multi-output ability of fuzzy logic control algorithms. In order to alleviate all difficulties to design an admissible control algorithm and attain the desired level of performance, the nondominated sorting genetic algorithm-II is applied. The effectiveness of the proposed controller on the inelastic seismic behavior of a controlled plan-asymmetric one-story structure is evaluated through a parametric study in which asymmetry is considered in the form of unidirectional mass eccentricity. To take the inelastic behavior of a controlled asymmetric building’s members into account, fiber elements modeling is employed. The model was subjected to a uniaxial lateral disturbance, including ordinary and strong ground motions exciting both lateral and torsional motions.

Effect of intercostobrachial nerve preserving in axillary lymph node dissection on sensory disturbance for breast cancer

Objective To explore the effect of preserving intercostobrachial nerve (ICBN) in axillary lymph node dissection on sensory disturbance for breast cancer. Methods Clinical data of 146 cases of stageⅠ, Ⅱ and Ⅲa breast cancer patients treated by modified radical mastectomy was analyzed. The patients were randomly divided into two groups. Retention group included 67 patients who were performed axillary lymph node dissection preserving ICBN, and 79 cases undergoing axillary lymph node dissection were taken as control group. Data of the two groups were assessed to compare the operation time, number of lymph nodes dissection and sensory abnormalities of upper arms. Results In the follow-up of 1, 3 and 6 months, the incidence rate of the lateral upper arm sensory disturbance were 17.9% and 74.9%, 11.9% and 60.7%, 7.4% and 59.5% respectively in the retention and control group, and the difference was statistically significant (χ2=46.78, P 0.05). No local recurrence after operation occurred in the follow-up of 8 months to 5 years. Conclusions For stage Ⅰ, Ⅱ and Ⅲa breast cancer patients undergoing axillary lymph node dissection, retaining ICBN can significantly reduce the chance of the postoperative medial upper arm sensory disturbance, improve the quality of life with no increase of local recurrence rate. Key words: Modified radical mastectomy of breast cancer; Axillary lymph node excision; Intercosto-brachial nerve

A Kind of Vibration Sensor and Testing System in Electromechanical Equipment Based on Fiber Bragg Grating

Mechanical vibration analysis is an important index to measure the running state of the electromechanical equipment. The vibration signals contain the information about the equipment running state. This paper studies and designs the vibration monitoring system based on fiber Bragg grating (FBG). Through the finite element analysis simulation, optimizes the sensor's structure, and uses the labview software to compile the corresponding vibration monitoring analysis software. Finally verifies the detection effect of the monitoring system, through the pulse signal and continuous signal dynamic experimental analysis. The result of the experimental analysis shows: this vibration monitoring system can monitor the vibration information and analyze vibration state effectively. It has the advantages of reducing the temperature interference and lateral disturbance, and detects the vibration of three direction at the same time. So it is feasible to monitor the electromechanical equipment.

Shock-Sensitivity in Shell-Like Structures: With Simulations of Spherical Shell Buckling

Under increasing compression, an unbuckled shell is in a metastable state which becomes increasingly precarious as the buckling load is approached. So to induce premature buckling, a lateral disturbance will have to overcome a decreasing energy barrier which reaches zero at buckling. Two archetypal problems that exhibit a severe form of this behavior are the axially-compressed cylindrical shell and the externally pressurized spherical shell. Focusing on the cylinder, a nondestructive technique was recently proposed to estimate the “shock-sensitivity” of a laboratory specimen using a lateral probe to measure the nonlinear load-deflection characteristic. If a symmetry-breaking bifurcation is encountered on the path, computer simulations showed how this can be suppressed by a controlled secondary probe. Here, we extend our understanding by assessing in general terms how a single control can capture remote saddle solutions: in particular, how a symmetric probe could locate an asymmetric solution. Then, more specifically, we analyze the spherical shell with point and ring probes, to test the procedure under challenging conditions to assess its range of applicability. Rather than a bifurcation, the spherical shell offers the challenge of a destabilizing fold (limit point) under the rigid control of the probe.

Nonlinear Observer-Based Ship Control and Disturbance Compensation

Abstract: In this paper, a gain-scheduled nonlinear control structure is proposed for a surface vessel, which takes advantage of extended linearisation techniques. Thereby, an accurate tracking of desired trajectories can be guaranteed that contributes to a safe and reliable water transport. The PI state feedback control is extended by a feedforward control based on an inverse system model. To achieve an accurate trajectory tracking, however, an observer-based disturbance compensation is necessary: external disturbances by cross currents or wind forces in lateral direction and wave-induced measurement disturbances are estimated by a nonlinear observer and used for a compensation. The efficiency and the achieved tracking performance are shown by simulation results using a validated model of the ship Korona at the HTWG Konstanz, Germany. Here, both tracking behaviour and rejection of disturbance forces in lateral direction are considered.

Lower-limb amputee ankle and hip kinetic response to an imposed error in mediolateral foot placement

Maintaining balance while walking is challenging for lower limb amputees. The effect of prosthetic foot stiffness on recovery kinetics from an error in foot placement may inform prescription practice and lead to new interventions designed to improve balance. Ten unilateral transtibial amputees were fit with two prosthetic feet with different stiffness properties in random order. After a 3-week acclimation period, they returned to the lab for testing before switching feet. Twelve non-amputees also participated in a single data collection. While walking on an instrumented treadmill, we imposed a repeatable, unexpected medial or lateral disturbance in foot placement by releasing a burst of air at the ankle just before heel strike. Three-dimensional motion capture, ground reaction force and center of pressure (COP) data were collected for two steps prior, the disturbed step and three steps after the disturbance. During undisturbed walking, coronal ankle impulse was lower by 42% for amputees wearing a stiff compared to a compliant foot (p=0.017); however, across steps, both prosthetic recovery patterns were similar compared to the sound limb and non-amputees. Peak coronal hip moment was 15–20% lower for both foot types during undisturbed walking (p<0.001), with less change in response to the medial disturbance (p<0.001) compared to the sound limb and non-amputees. Amputee prosthetic COP excursion was unaffected by the disturbance (2.4% change) compared to the sound limb (59% change; p<0.001) and non-amputees (55% change; p<0.001). These findings imply that a prosthetic foot–ankle system able to contribute to ankle kinetics may improve walking balance among amputees.

Numerical analysis of flow separation and side loads of a conical nozzle during staging

The objective of this effort is to numerically investigate the effect of the fire-in-the-hole staging event on the start-up flow separation and side loads of a conical nozzle during flight. The axisymmetric transient flow structure in nozzle was examined by time-accurate numerical method with time-varying chamber pressure and separation gap width. Three-dimensional time-accurate computations to examine the side loads due to non-nominal staging movement were conducted for two particular cases: misalignment between two stages and the angle of the nozzle thrust vector direction. Each asymmetry case comprised several specific staging state points which determined the corresponding chamber pressure and staging gap width. As presented by the simulation results, the flow separation in nozzle is significantly prolonged and intensified by the obstruction of the lower stage dome. When the flow separation location moves close to the nozzle exit, a strenuously axial oscillation of the separation shock appears and lasts for a period of time. In the three-dimensional asymmetric computations, in spite of strenuous oscillation, the time-average of nozzle side loads indicate that the asymmetric staging situation could lead to large sustained lateral disturbance forces. An essential ingredient driving the flow unsteadiness and asymmetry is related to the deflected and reversed supersonic flow by the dome and interstage wall corner of lower stage.

Lateral thermal disturbance of embankments in the permafrost regions of the Qinghai-Tibet Engineering Corridor

Numerous engineering projects have been completed on the Qinghai-Tibet Plateau, and with continued economic growth, additional important engineering projects are being planned. Major transportation construction is largely restricted to the Qinghai-Tibet Engineering Corridor, which is as narrow as a few hundred meters in some places. In this narrow corridor, projects such as the Qinghai-Tibet Railway and the Qinghai-Tibet Highway can influence the stability of the permafrost. We use a numerical model to investigate the individual thermal disturbance caused by the Qinghai-Tibet Railway, the Qinghai-Tibet Highway, and the planned Qinghai-Tibet Expressway. To simulate an upper limit of disturbance under current climate we use the most unfavorable combination of engineering design practices, with unprotected embankments, a traditional ballast embankment for the Qinghai-Tibet Railway, and traditional asphalt pavement embankments for the Qinghai-Tibet Highway and the Qinghai-Tibet Expressway. The lateral thermal disturbance extent of the three projects increases linearly with embankment height. Under the same embankment heights, the lateral extent of thermal disturbance is smallest for the Qinghai-Tibet Railway and is largest for the full Qinghai-Tibet Expressway. The model results provide guidance for minimum distances between the transportation projects to prevent thermal interaction, as a function of embankment height and design. In future research it is important to evaluate the thermal disturbance scopes of other engineering structures, such as tunnels, bridges, and oil pipelines, and to evaluate the thermal interaction and cumulative impact of multiple structures under current and future climate scenarios.

Combining Coordination of Motion Actuators with Driver Steering Interaction

Objective: A new method is suggested for coordination of vehicle motion actuators; where driver feedback and capabilities become natural elements in the prioritization.Methods: The method is using a weighted least squares control allocation formulation, where driver characteristics can be added as virtual force constraints. The approach is in particular suitable for heavy commercial vehicles that in general are over actuated. The method is applied, in a specific use case, by running a simulation of a truck applying automatic braking on a split friction surface. Here the required driver steering angle, to maintain the intended direction, is limited by a constant threshold. This constant is automatically accounted for when balancing actuator usage in the method.Results: Simulation results show that the actual required driver steering angle can be expected to match the set constant well. Furthermore, the stopping distance is very much affected by this set capability of the driver to handle the lateral disturbance, as expected.Conclusion: In general the capability of the driver to handle disturbances should be estimated in real-time, considering driver mental state. By using the method it will then be possible to estimate e.g. stopping distance implied from this. The setup has the potential of even shortening the stopping distance, when the driver is estimated as active, this compared to currently available systems. The approach is feasible for real-time applications and requires only measurable vehicle quantities for parameterization. Examples of other suitable applications in scope of the method would be electronic stability control, lateral stability control at launch and optimal cornering arbitration.