Yaw Velocity Research Articles

Optimal setpoint chasing in dynamic positioning of deep‐water drilling and intervention vessels

Conventional controller designs for dynamic positioning of ships and floating marine structures have so far been based on the principle on automatic positioning in the horizontal-plane about desired position and heading co-ordinates defined by the operator. A three degrees-of-freedom multivariable controller either of linear or nonlinear type, normally with feedback signals from surge, sway and yaw position and velocities, has been regarded as adequate for the control objective. For floating structures with small waterplane area such as semi-submersibles, feedback from roll and pitch angular rotation velocity may also be included to avoid thrust-induced roll and pitch motions that are caused by the hydrodynamic and the geometrical couplings between the horizontal and vertical planes. However, for certain marine operations this control philosophy may not be the most appropriate approach ensuring safety and cost effectiveness. For drilling and work-over operations the main positioning objective is to minimize the bending stresses along the riser and the riser angle magnitudes at the well head on the subsea structure, and at the top joint as well. A positioning control strategy solely based on manual setting of the desired position co-ordinates may not be the most optimal solution for these applications. In this paper a new hybrid dynamic positioning controller, that also accounts for riser angle offsets and bending stresses is proposed. It is shown that a significant reduction in riser angle magnitude can be achieved. Simulations with a drilling semi-submersible demonstrate the effect of the proposed control strategy. Copyright © 2001 John Wiley & Sons, Ltd.

Dynamics of four-wheel-steering vehicles

In this paper we present an optimised 3 degrees-of-freedom non-linear dynamic model of a four-wheel-steering (4WS) vehicle. As variables, we retain the lateral velocity V, the rolling velocity p and yaw velocity r. The front steer angle δf and rear steer angle δr are considered to be linear functions of the steering wheel angle θs and of dθs/dt, the proportionality parameters being k1f, k2f for δf and k1r, k2r for δr. The parameters k1f, k2f, k1r, k2r are optimised by use of the BOX mathematical algorithm. In a first optimisation loop we minimise the sideslip angle β of the vehicle and in a second optimisation loop we assure, that the resultant (taken in the centre of gravity of the vehicle) of all the transversal forces Fy applied on the wheels of the vehicle (reaction forces contained in the road plane), give a component Fyx along the longitudinal axis of the vehicle, that takes a non negative value. This assures, that the motor of the vehicle will not waste fuel to overcome resistance forces originating from the steering system of the vehicle. A numerical application is also presented for a 4WS vehicle negotiating a curve at constant velocity. The results are compared to those obtained by two models frequently used in the literature. The comparison testifies on the superiority of our model for the application presented here.

Mechanical models for insect locomotion: stability and parameter studies

We extend the analysis of simple models for the dynamics of insect locomotion in the horizontal plane, developed in [Biol. Cybern. 83 (6) (2000) 501] and applied to cockroach running in [Biol. Cybern. 83 (6) (2000) 517]. The models consist of a rigid body with a pair of effective legs (each representing the insect’s support tripod) placed intermittently in ground contact. The forces generated may be prescribed as functions of time, or developed by compression of a passive leg spring. We find periodic gaits in both cases, and show that prescribed (sinusoidal) forces always produce unstable gaits, unless they are allowed to rotate with the body during stride, in which case a (small) range of physically unrealistic stable gaits does exist. Stability is much more robust in the passive spring case, in which angular momentum transfer at touchdown/liftoff can result in convergence to asymptotically straight motions with bounded yaw, fore-aft and lateral velocity oscillations. Using a non-dimensional formulation of the equations of motion, we also develop exact and approximate scaling relations that permit derivation of gait characteristics for a range of leg stiffnesses, lengths, touchdown angles, body masses and inertias, from a single gait family computed at ‘standard’ parameter values.

Optimal setpoint chasing in dynamic positioning of deep‐water drilling and intervention vessels

AbstractConventional controller designs for dynamic positioning of ships and floating marine structures have so far been based on the principle on automatic positioning in the horizontal‐plane about desired position and heading co‐ordinates defined by the operator. A three degrees‐of‐freedom multivariable controller either of linear or nonlinear type, normally with feedback signals from surge, sway and yaw position and velocities, has been regarded as adequate for the control objective. For floating structures with small waterplane area such as semi‐submersibles, feedback from roll and pitch angular rotation velocity may also be included to avoid thrust‐induced roll and pitch motions that are caused by the hydrodynamic and the geometrical couplings between the horizontal and vertical planes. However, for certain marine operations this control philosophy may not be the most appropriate approach ensuring safety and cost effectiveness. For drilling and work‐over operations the main positioning objective is to minimize the bending stresses along the riser and the riser angle magnitudes at the well head on the subsea structure, and at the top joint as well. A positioning control strategy solely based on manual setting of the desired position co‐ordinates may not be the most optimal solution for these applications. In this paper a new hybrid dynamic positioning controller, that also accounts for riser angle offsets and bending stresses is proposed. It is shown that a significant reduction in riser angle magnitude can be achieved. Simulations with a drilling semi‐submersible demonstrate the effect of the proposed control strategy. Copyright © 2001 John Wiley & Sons, Ltd.

Improvement of Road Vehicle Handling by Mechatronic Systems

Starting with ABS (Antilock Brake System) which was introduced on the automotive market in 1978 the initial step towards mechatronic systems dealing with vehicle dynamics was taken. Other systems like suspension control and four wheel steering control to improve vehicle handling followed in the early part ofthe 1980 decade. These systems were initially designed as open loop controllers for the lateral vehicle motion. A frrst approach towards closed loop control of the lateral vehicle motion was in combination with four wheel steering using a yaw velocity sensor in the frrst halve of the 1990 decade. Other closed loop systems like ESP (Electronic Stability Program) and DYC (Direct Yaw Control) followed in 1995 and 1997 respectively. ESP has become very popular since 1998 because of its low cost and high efficiency in limit handling maneuvers.

Modelling and Control of Riser Angles and Stresses in Dynamic Positioning

Conventional controller designs for dynamic positioning of ships and floating marine structures have so far been based on the principle on automatic positioning in the horizontal-plane about some desired position and heading co-ordinates. A three degrees of freedom multivariable controller either of linear or nonlinear type, normally with feedback signals from surge, sway and yaw position and velocities, has been regarded as adequate for the control objective. For semi-submersibles feedback from roll and pitch angular rotation velocity may also be included. However, for certain marine operations this control philosophy may not be the most appropriate approach ensuring a safe and cost effective operation. For drilling and work over operations the main positioning objective is to minimise the bending stresses along the riser and the riser angle magnitudes at the well head on the subsea structure and at the top joint as well. A positioning strategy solely based on position and velocity feedback may not be the most optimal solution for these applications. In this paper a new hybrid dynamic positioning controller, that also accounts for riser angle offsets and bending stresses is proposed. It is shown that a significant reduction in riser angle magnitude can be achieved. Simulations with a drilling semi-submersible demonstrate the effect of the proposed control strategy.

Improvement of vehicle directional stability in cornering based on yaw moment control

In this research any abnormal motion of a vehicle is detected by utilizing the difference between the reference and actual yaw velocities as sell as the information on vehicle slip angle and slip angular velocity. This information is then used as a criterion for execution of the yaw moment control. A yaw moment control algorithm based on the brake control is proposed for improving the directional stability of the vehicle. The controller executes brake controls to provide each wheel with adequate brake pressures, which generate the needed yaw moment. It is shown that the proposed yaw moment control logic can provide excellent cornering capabilities even on low friction roads. This active control scheme can prevent a vehicle from behaving abnormally, and can assist normal drivers in coping with dangerous situations as well as experienced drivers.

Measurement method of normalized cornering stiffness

This paper presents a measurement method of the normalized equivalent cornering stiffness (normalized C p ), which dominates a vehicle's steering responses. First, the method measures rear normalized C p from the velocity at which the sign of vehicle slip angle is reversed in steady-state turning. The method is accurate because the velocity is independent of the errors of measuring instruments. Second, the method measures front normalized C p from yaw velocity gain. Last, the measured normalized C p 's of various vehicles are plotted on a distribution map, which indicates steering responses of each vehicle.

Control of Unicycle-Type Robots in the Presence of Sliding Effects with Only Absolute Longitudinal and Yaw Velocities Measurements

In this paper we are concerned with the control of unicycle-type wheeled mobile robots in presence of sliding effects measurements. The slipping and skidding effects are known to be very noisy so we want to elaborate a control law which solves the velocity tracking problem by using only absolute longitudinal and yaw velocities. First, we choose to simplify the problem by taking into account only the more important component of the slip with respect to the trajectory. In a turn, we modelize the skidding effects, however we introduce the longitudinal slip in a straight line. Then, we got our inspiration from the approach used in these particular cases to elaborate a global control law which makes the lateral, longitudinal and yaw velocities tend to zero. This control law does not need sliding effects measurements but depends on the slip and cornering stiffness coefficients.

Independent Suspension, Self Steered Axle, and 4WS for Busses

The dynamic behavior of commercial vehicles fitted with differentr types of suspension mechanisms and steering devices is investigated in this paper. Six vehicle models have been constructed: 2WS-SA is a standard two wheel steering bus with solid axles; 2WS-DW is a 2WSA vehicle with independent double wishbone suspension in front and rear axles; SSA-SA is a 2WS system with solid axles, the rear one being mounted on a self steered mechanism; SSA-DW is a vehicle with independent double wishbone suspension in the front axle, and a solid self steered rear axle; 4WS-SA has four wheel steering with solid axles; and 4WS-DW is a 4WS vehicle with independent double wishbone suspension in front and rear axles. The dynamic response of these models has been assessed in terms of lateral acceleration, yaw velocity, tire forces, tire force reserves, and slip angles. The expected advantages of a 4WS system (higher acceleration rates and lower slip angles) will be corroborated but, at the same time, it will be shown that they are obtained at the cost of lower force reserves. Self steered mechanisms produce smaller body slip angles, but it will be shown that they give rise to larger yaw velocity overshootings. The particular independent suspension analyzed does not show significant improvements with respect to the solid axle counterpart.

Parametric identification of manoeuvring models for ships

Time domain simulation techniques are becoming a widely accepted tool for the evaluation of controllability and manoeuvring performance of conventional surface ships. Different simulation packages are available on a commercial basis. The accuracy of predictions obtained using these models are largely dependent on the level of accuracy in estimating the values of the parameters used in these models. Several methods are available for the determination of the values of these hydrodynamic parameters. However, each one of these existing methods has its own shortcomings. In this paper a new predictive method is outlined for the estimation of the hydrodynamic characteristics for a ship performing certain standard manoeuvres. The method uses neural networks technique to predict the hydrodynamic parameters of the ship. Parameters normally measured during standard manoeuvre e.g. surge, sway and yaw velocities and rudder angle, will be used as input to the predictive model. The first author has successfully used the same technique in predicting the transverse stability ofa ship at sea.

On The Dynamics of Actively Steered Railway Vehicles

Two active steering systems and an active guidance system for a vehicle with two wheel-pairs are described and analysed. A wheel-pair has independently rotating wheels pin-jointed to a carrying frame. The wheels are mounted on stub-axles and have hub-mounted traction motors. Differential torques are applied to the wheels to generate a steering input. The equations defining the systems are presented The two active steering systems use either the body yaw velocity and train speed or knowledge of the route data and position to steer the wheels to be radial on a curve. The active guidance system uses a lateral displacement transducer to measure the lateral position of the wheels in the track to generate an error signal. All the controllers perform well on the steady curve. On the “virtual” transition into the curve, the active guidance controller performs much better than the steering controllers, benefitting from preview of the track.

A Model That Relates Canal-Ocular to Otolith-Ocular Responses

Rotation about the vertical stimulates primarily the horizontal semicircular canals and produces compensatory horizontal nystagmus whose slow component velocity response during constant velocity can be approximated as having a simple exponential decay time constant, Tvor. Constant velocity yaw rotation about a horizontal axis stimulates both the horizontal canals and the otolith organs, producing two additional nystagmus components thought to be of otolithic origin: a steady component called bias and a periodic component known as modulation. We tested a group of 7 human subjects using rotation about each of these axes. We found a strong, negative correlation (r = 0.956) between these individuals' dominant time constants, Tvor, and the magnitude of their modulation components. Canal and otolith signals originate from different parts of the same endorgan and travel separately to the vestibular nucleus. The reflexive eye movements in response to these inputs are thought to be the result of additional processing by the central vestibular and ocular motor systems. Thus, the source of these strongly correlated otolith-ocular and canal-ocular reflex components could logically be due to common factors affecting peripheral transduction or to a subsequent common central processing step. Using anatomical measurements of human vestibular end organs, biophysical endorgan models, and models of central vestibular processes, we examined the alternatives to determine which was the most likely. Correlations were not found between Tvor and the anatomical data or between the Tvor and the biophysical model elements. However, modifications of the velocity storage integrator of Raphan to incorporate either a highpass filter (HPF) or a lowpass filter input for otolith modulation signals allowed for the desired strong negative correlation between Tvor and modulation. We argue in favor of the HPF configuration because it better explains the tendency for the modulation component to increase in amplitude as the modulation frequency is increased. In the above mentioned representation of the central processing of vestibular afferent inputs, we conclude that the modulation component input to the vestibuloocular reflex is within the indirect pathway, but it is "down stream" from the velocity storage integrator.

Development of an electronically controlled four wheel drive system for FR vehicle with AT

A high-performance electronically controlled four wheel drive system was developed for a Front engine Rear drive (FR) vehicle with automatic transmission. This system consists of a center differential (torque split ratio is front: rear = 30:70 ), a linear solenoid valve, a hydraulic multi-disk clutch and a hydraulic control circuit. By regulating the hydraulic pressure on the clutch, the driving force distribution can be continously varied to the optimum ratio for the running condition of the vehicle, which is determined by wheel speed, yaw velocity and the steering wheel angle.

Estimation of vehicle side slip angle with artificial neural network

The side slip angle provides a key state value that defines the yawing and lateral motion of a vehicle. Accordingly, would it be possible to detect or estimate the side slip angle of a real vehicle with higher precision, the vehicle could be properly controlled with a more ideal state feedback control. There are two methods of measuring side slip angles. One is a direct method that measures the longitudinal and lateral velocity respectively, using optical speed sensors. The other is an indirect method that integrates the difference between the lateral acceleration/vehicle speed and the yaw velocity. These methods have been generally used for measurements of vehicle dynamics. Although, the only representative method for estimation would be the application of a linear vehicle model, like an observer, precision and reliability are not sufficient in various conditions of production cars. The objective of this paper is to estimate side slip angles with higher precision using an artificial neural network, without using optical speed sensors or an integral calculation method. The description is devoted to a settlement of basic system performance using simulation and to a verification of test results using actual vehicles.

The Selection Of Optimum Vehicle Parameters Based On The Pilot-Vehicle Directional Stability

In this paper, a parametric study of the pilot-vehicle closed-loop system is presented. The study is based on the heading and lateral stability region using a lead-lag compensator to represent the human driver. A two degrees of freedom model is used to describe the yaw and lateral velocity of the vehicle. The effects of the vehicle moment of inertia, C.G location and cornering stiffnesses on the maximum crossover frequencies of the system are investigated. The relationship between these parameters and the maximum crossover frequency is obtained using a multi-nonlinear regression analysis from which the optimum problem is formulated and solved using Lagrange multipliers. The optimum values are used to form hypothetical vehicle models which are compared with the typical vehicles. The obtained results suggest some fundamental changes in the tire cornering stiffnesses, C.G location and mass moment of inertia. Simulation results in the frequency and time domains illustrate the effectiveness and capabilities of the proposed vehicles over the typical ones. (A) For the covering abstract see IRRD 864807.

Balloting motion of SLEKE launch packages in EM railguns

The author reports some balloting motion computational results of the SLEKE (sabot launched electric-gun kinetic energy) launch packages, which are in their early stage of development. The computation model considers the effects of the electromagnetic (Lorentz) propulsion force, friction air resistance, gravity, elastic forces, and clearance between the launch package and the barrel. Computed are: the axial, normal, and yaw displacement, velocity, and acceleration; friction; and deformations and forces at the interfacing points. The results of this study indicate that the balloting force for the SLEKE launch packages is on the order of the air drag force and that a uniformly distributed power source would be more desirable than sharp pulse current for electromagnetic railguns.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Yaw Velocity Feedback Control of Four-Wheel Steering Car by Neural Network.

Recently many kinds of four-wheel steering (4WS) systems have been proposed and studied. Design of these control systems is based mainly on the two-degrees-of-freedom model. However, vehicle motion is influenced by various nonlinear factors, for example tire characteristics and road conditions. Thus, it is difficult to express the vehicle motion perfectly with the two-degrees-of-freedom model. In this paper, a new 4WS control system with application of the neural network theory is presented. The design of the controller consists of two learning procedures for identification of the system and synthesis of the controller. In order to investigate the effectiveness of the proposed method, computer simulations and control experiments were carried out. As a result it was demonstrated that application of the neural network for motion control in 4WS systems is useful.

Optimal Control of Four Wheel Steering Vehicle

SUMMARY This paper derives a method of controlling four wheel steering using optimal control theory. The purpose of control is to minimize the sideslip angle at the center of gravity. The control method feeds forward the steering wheel angle and feeds back the yaw velocity and the sideslip angle to the front and rear wheel angles. Theoretical studies show that the sideslip angle is reduced to zero even in the transient state, and that the understeer characteristic and frequency response can be changed regardless of the vehicle static margin. This Paper also examines various characteristics of the influence of the side force nonlinearities of tires and crosswinds.

Spatial orientation of the vestibular system: dependence of optokinetic after-nystagmus on gravity

1. Monkeys received optokinetic stimulation at 60 degrees/s about their yaw (animal vertical) and pitch (animal horizontal) axes, as well as about other head-centered axes in the coronal plane. The animals were upright or tilted in right-side-down positions with regard to gravity. The stimuli induced horizontal, vertical, and oblique optokinetic nystagmus (OKN). OKN was followed by optokinetic after-nystagmus (OKAN), which was recorded in darkness. 2. When monkeys were tilted, stimulation that generated horizontal or yaw axis eye velocity during OKN induced a vertical or pitch component of slow phase velocity during OKAN. This has been designated as "cross-coupling" of OKAN. Eigenvalues and eigenvectors associated with the system generating OKAN were found as a function of tilt. They were determined by use of the Levenberg-Marquardt algorithm to minimize the mean square error between the output of a model of OKAN and the data. 3. The eigenvector associated with yaw OKAN (yaw axis eigenvector) was maintained close to the spatial vertical regardless of the angle of tilt. The eigenvector associated with pitch OKAN (pitch axis eigenvector) was always aligned with the body axis. The data indicate that velocity storage can be modeled by a piecewise linear system, the structure of which is dependent on gravity and the yaw axis eigenvector, which tends to align with gravity. 4. Yaw axis eigenvectors were also determined by giving optokinetic stimulation about head-centered axes in the coronal plane with the animal in various angles of tilt. A technique using a spectral analysis of residuals was developed to estimate whether yaw and pitch OKAN slow phase velocities decayed concurrently at the same relative rate and over the same time course. The eigenvectors determined by this method were in agreement with those obtained by analyzing OKAN elicited by yaw OKN. 5. During yaw OKN with the animal in tilted positions, the mean vector of the ensuing nystagmus was closer to the body axis than to the spatial vertical. This suggests that there is suppression of the cross-coupled pitch component during OKN. The direction of the stimulus may be utilized to suppress components of velocity storage not coincident with the direction of stimulus motion. 6. There were similarities between the monkey eigenvectors and human perception of the spatial vertical, and the mean of eigenvectors for upward and downward eye velocities overlay human 1-g perceptual data.(ABSTRACT TRUNCATED AT 400 WORDS)