Steering Stiffness Research Articles

Analysis and optimization of vehicle transient characteristics under sine-swept steering input with considering steering system stiffness and damping

This study focuses on the influence of steering system stiffness and damping on the vehicle transient characteristics at two different types of handling frequencies, and optimizes the vehicle transient characteristics with steering system stiffness and damping as optimization variables at both handling frequencies. The kinematic relationship between wheel angle and steering wheel angle is derived as well as a detailed analysis of the forces on the steering linkage. The differential equations of vehicle dynamics are developed to explain the influence of steering system stiffness and damping on the vehicle transient characteristics theoretically. The stiffness and damping, which have a significant influence on the vehicle transient characteristics, are selected by sensitivity analysis and used as variables for simulation verification. Simulation results show that the influence of steering system stiffness and damping on vehicle transient characteristics is different at high handling frequencies and low handling frequencies. The stiffness and damping are used as optimization variables and the objective evaluation indexes of vehicle transient characteristics at high handling frequencies and low handling frequencies are used as optimization targets for multi-objective optimization by the NSGA-II optimization algorithm. The optimization results show that: The yaw rate gain relative to steering wheel angle and the delay time of lateral acceleration relative to steering wheel angle are improved at both low and high frequencies.

A study on body sway of car-trailer combinations considering dry friction in steering subsystem

Considering the stability of vehicle system, static instability and dynamic instability are two different instability problems. Because of the dynamic coupling between car and trailer, the problem of dynamic stability of car-trailer combination (CTC) is more obvious. This instability is called body sway or flutter in engineering, its boundary is often described by dynamic critical speed ( vcrit). It has been proved by experiments that the steering system characteristics have an important impact on the dynamic stability of CTC, but the specific mechanism is not clear. In this paper, the characteristic and influence of steering subsystem are studied for the first time. Firstly, a 6-DOF nonlinear dynamic model of CTC is established by Lagrange equation. The steering subsystem characteristics, incl. stiffness, damping, rotational inertia, and dry friction, are considered in theoretical modeling. On this basis, the influences of steering characteristics, especially the dry friction, on vcrit and axle cornering stiffness of CTC are analyzed. Simulation results show that the vcrit can increase by 16% and 23.2% respectively via adjusting the steering stiffness and the sliding friction factor. Therefore, a fine selection of steering subsystem characteristics can effectively improve the dynamic stability and safety of CTC. The research results of this paper can provide reference for the design of steering system considering dynamic stability.

Musculoskeletal Driver Model for the Steering Feedback Controller

This paper aims to find a mathematical justification for the non-linear steady state steering haptic response as a function of driver arm posture. Experiments show that different arm postures, that is, same hands location on the steering wheel but at different initial steering angles, result in a change in maximum driver arm stiffness. This implies the need for different steering torque response as a function of steering angle, which is under investigation. A quasi-static musculoskeletal driver model considering elbow and shoulder joints is developed for posture analysis. The torque acting in the shoulder joint is higher than in the elbow. The relationship between the joint torque and joint angle is linear in the shoulder, whereas the non-linearity occurs in the elbow joint. The simulation results qualitatively indicate a similar pattern as compared to the experimental muscle activity results. Due to increasing muscle non-linearity at high steering angles, the arm stiffness decreases and then the hypothesis suggests that the effective steering stiffness is intentionally reduced for a consistent on-center haptic response.

Effect of Variable Wheelset Steering Stiffness and Yaw Damper Damping on Hunting Stability

Due to the track curvature and irregularities difference, a high-speed dedicated railway vehicle running on a high-speed railway cannot achieve a good dynamics performance when it is operated on an existing railway for conventional low-speed railway vehicle. Then an adaptive bogie which can adjust its suspension parameters, like the steering stiffness of wheelset and the damping of yaw damper, is regarded as a solution to make the high-speed train be operated on an existing railways. In this investigation, a highly nonlinear dynamics model of the adaptive bogie vehicle multi-body system is built to study the effects of wheelset steering stiffness and yaw damper damping on the vehicle dynamics. Both a straight track passing and curved tracks negotiating scenarios are considered to examine the expected range of stiffness and damping when the bogie was operated those two kinds of railways. It shows that reducing the steering stiffness of wheelset leads to a significant decrease in the critical speed of vehicle, and the critical speed of vehicle decreases significantly when the yaw damper damping is less than 500 kN⋅s/m. In case of wheel wear, the smaller the wheelset steering stiffness or the yaw damper damping is, the lower the critical speed of vehicle is. Through the analysis, the limit values of wheelset steering stiffness and yaw damper damping are proposed. When the adaptive bogie vehicle operates on the existing track, the lower limit values of wheelset steering stiffness and yaw damper damping are 12 MN/m and 200 kN⋅s/m respectively.

Simulation Research on the Driving Stability of Articulated Vehicle Based on ADAMS

The vehicle dynamical model was established by taking the articulated vehicle driven electrically as the research object, and the vehicle dynamical simulation was carried out by using ADAMS. The effects of different center of mass position, steering parameters, mass, lateral stiffness of tire, suspension stiffness and damping on the driving stability of articulated vehicle were analyzed. The simulation results showed that the driving stability of the articulated vehicle was improved by factors such as the position of the center of mass closing to the hinged point, increasing the steering stiffness and damping, reducing the lateral stiffness of the tire, increasing the suspension stiffness and damping, appropriately increasing the rear body mass, etc. This study provided a reference for the design and improvement of the vehicle.

Effect of Wheelset Steering Stiffness Difference on the Dynamics Performance of a High-speed Railway Vehicle

In order to study the influence of steering difference of wheelsets among one bogie on the dynamics performance of vehicle, a highly nonlinear dynamics model of the high-speed railway vehicle multi-body system is built. In numerical simulations, the combined condition of taking the upper and lower limits of the steering stiffness of wheelset is investigated, respectively. It shows that the effect of wheelset steering stiffness on the dynamic performance is not significant. Its influence on the lateral vibration of bogie frame, hunting stability of vehicle, operation safety when negotiating curved tracks and wheel wear is generally within 5%. Its influence on the maximum lateral and vertical acceleration of carbody is generally within 10% and the influence range of specific cases is within 20%. For all the numerical cases, the vehicle dynamics indexes all meet the required limit.

Dynamic behavior of a vehicle with rear axle compliance steering

Rear axle compliance steering (RACS) is a technology of passive four-wheel steering, which is designed to improve the vehicle handling and stability at medium or high speed. This paper focuses on the dynamic behavior of the vehicle with RACS. Firstly, the compliance steering principle for different rear suspensions is illustrated. Then, the viscoelastic members with fractional order derivative properties are introduced into RACS, and the fractional order model of RACS is formulated. Next, the dynamic model of the vehicle with RACS is established, the adjusting rules for the compliance steering stiffness are derived, and the vehicle stability is investigated. Finally, numerical experiments are performed to illustrate the effects on the vehicle dynamic behavior caused by the compliance steering stiffness, the viscoelastic members and the vehicle longitudinal velocity. Research results show that, the vehicle with RACS has better dynamic characteristics than that without RACS at medium or high speed; and the compliance steering stiffness, the viscoelastic members and the vehicle longitudinal velocity have different impacts on the vehicle lateral dynamic behavior.

Dynamic vehicle model for handling performance using experimental data

An analytical vehicle model is essential for the development of vehicle design and performance. Various vehicle models have different complexities, assumptions and limitations depending on the type of vehicle analysis. An accurate full vehicle model is essential in representing the behaviour of the vehicle in order to estimate vehicle dynamic system performance such as ride comfort and handling. An experimental vehicle model is developed in this article, which employs experimental kinematic and compliance data measured between the wheel and chassis. From these data, a vehicle model, which includes dynamic effects due to vehicle geometry changes, has been developed. The experimental vehicle model was validated using an instrumented experimental vehicle and data such as a step change steering input. This article shows a process to develop and validate an experimental vehicle model to enhance the accuracy of handling performance, which comes from precise suspension model measured by experimental data of a vehicle. The experimental force data obtained from a suspension parameter measuring device are employed for a precise modelling of the steering and handling response. The steering system is modelled by a lumped model, with stiffness coefficients defined and identified by comparing steering stiffness obtained by the measured data. The outputs, specifically the yaw rate and lateral acceleration of the vehicle, are verified by experimental results.

Research on Steering Characteristics of Multi-Axles Steering Vehicle

A 3-DOF multi-axle steering vehicle model were established using Lagrangian analysis method, including steering system stiffness, cornering stiffness and power steering system. The vehicle model is verified correctly and universally by using front wheels steering vehicle model. Based on the vehicle model, the steady circling parameters of multi-axle steering vehicle are presented. The effects of vehicle physical parameters on the steering characteristics of multi-axle steering vehicle are analyzed. To further demonstrate the correctness of multi-axle steering vehicle model, a three-axle steering vehicle model were built by ADAMS software. It is a theoretical basis for the design of multi-axle steering vehicle and the evaluation of steering characteristics.

Steerable Mechanical Joint for High Load Transmission in Minimally Invasive Instruments

As minimally invasive operations are performed through small portals, the limited manipulation capability of straight surgical instruments is an issue. Access to the pathology site can be challenging, especially in confined anatomic areas with few available portals, such as the knee joint. The goal in this paper is to present and evaluate a new sideways-steerable instrument joint that fits within a small diameter and enables transmission of relative high forces (e.g., for cutting of tough tissue). Meniscectomy was selected as a target procedure for which quantitative design criteria were formulated. The steering mechanism consists of a crossed configuration of a compliant rolling-contact element that forms the instrument joint, which is rotated by flexural steering beams that are configured in a parallelogram mechanism. The actuation of cutting is performed by steel wire that runs through the center of rotation of the instrument joint. A prototype of the concept was fabricated and evaluated technically. The prototype demonstrated a range of motion between −22° and 25° with a steering stiffness of 17.6 Nmm/rad (min 16.9 – max 18.2 Nmm/rad). Mechanical tests confirmed that the prototype can transmit an axial load of 200 N on the tip with a maximum parasitic deflection of 4.4°. A new sideways steerable mechanical instrument joint was designed to improve sideways range of motion while enabling the cutting of strong tissues in a minimally invasive procedure. Proof of principle was achieved for the main criteria, which encourages the future development of a complete instrument.

1114 大型車の直進性に与える操舵系の影響に関する研究 : 第2報:車両運動に与える操舵系剛性の影響(OS2-2 自動車・二輪車のダイナミクス,OS2 交通・物流システムのダイナミクス,オーガナイズド・セッション(OS))

The characteristic of on-centered steering stability is important to contract a control system for autonomous vehicle, and we need to investigate the systematic treatment. As a first stage of this research, we have constructed a steering model with circumstantial stiffness of on-centered steering which is decreased at neutral region. In this study, using full vehicle model and steering model of on-centered steering stiffness, it is shown that this model has good expression for the vehicle behavior of heavy duty vehicles.

Design of a Compliant Steerable Arthroscopic Punch

Meniscectomy is a medical procedure where ruptured meniscal tissue is removed within the knee joint. The conventional cutters fail to reach the entire meniscus. Therefore, the focus of this study is to create a steerable joint, which allows sideway steering of the tip to increase the reachability within the knee joint. Additionally, the steerable joint is required to be robust to transmit a cutting force of up to 190 N. The mechanism design is divided into the functions: steering and actuating cutting mechanism. The most promising solution of these functions was combined and resulted in the use of a crossed configuration of a compliant rolling-contact element for the instrument joint. Flexural steering beams actuate the rotation of the joint using the principle of a parallelogram mechanism. The prototype has a range of motion of +25 deg and −22 deg with a steering stiffness at the handle side of 33 N mm/rad. An axial load of 200 N on the tip corresponded with a parasitic deflection of 4 deg. This unique type of steerable instrument shows potential to be functional in meniscectomy due to the great robustness of the joint.

Experimental research on steering stiffness of SBW

The steering wheel of a steer-by-wire (SBW) vehicle is free from road-disturbance because of the lack of mechanical connection. There is less need for disturbance attenuation and the SBW actuator can be mounted rigidly on the vehicle chassis. A bench test using actual SBW system demonstrates that the steering stiffness becomes larger than the electronic-power-steering (EPS) stiffness. A driving experiment and a closed-loop simulation show that the increase of this stiffness plays a crucial role in reducing work load for the SBW driver.

Tire Lateral Force Modeling and the Bushing Analogy Tire Model

Abstract The Bushing Analogy Tire (BAT) model has been studied for tire dynamics modeling in vertical and lateral directions. It was shown that the vibration characteristics included in the BAT model in the vertical and lateral directions cover the tire modes in those directions up to about 100 Hz. This capability of the BAT model is suitable for vehicle ride simulations. However, in vehicle handling situations such as accident avoidance, the tire is subjected to sudden steering motions that are not included in the vertical and lateral dynamics. The steering generates tire slip angle and, hence, the lateral forces for vehicle direction change. The tire steering motion also generates the aligning torque, which modifies the slip angle of the tire with respect to the wheel input steering angle. The tire steering compliance is therefore important for the dynamic responses during the vehicle handling maneuvers. In this paper, tire compliance in the steering direction is studied by treating the steering motion as an independent motion of the 3-dimentional tires. In this paper, the steering stiffness (or compliance) of a tire is first derived from the analysis results of a tire Finite Element (FE) model. Comparing the steering direction vibration modes using the BAT model with the FE model extracted modes further validates the steering stiffness. The coupling of tire steering stiffness with the vertical forces is also studied. Then, the effects of the tire steering direction stiffness are used to study a data set of flat-track generated tire lateral force and moment. The procedure of generating required coefficients of a handling tire model coupled with tire dynamic features of the BAT model were also investigated.

A Qualitative Analysis of the Dynamics of Self-Steering Locomotive Trucks

The primary purpose of this study is to provide a qualitative analysis of the dynamics of the self-steering trucks that are commonly used for freight locomotives – namely, EMD's Radial Truck and GE's Steerable Truck – on improving curving performance and increasing adhesion in curves. Although there exists a number of anecdotal statements on the ability of steerable trucks to reduce curving forces and increase adhesion in curves, to the best of our knowledge, there exists no study that provides a qualitative or quantitative analysis of these features of steerable trucks. Two aspects of locomotive trucks are essential for their ability to deliver small curving forces and high adhesion in curves. First, the ability to allow the axles to yaw sufficiently relative to the truck frames, such that they can hold a small angle of attack with the rail. Second, providing sufficiently large longitudinal stiffness between the end axles and the axles and truck frame, to accommodate high adhesions. An equivalent stiffness analysis is used to show that the two steerable trucks that are considered for this study are far superior to conventional, three-axle, straight trucks in providing both a smaller angle of attack and a higher longitudinal stiffness for better curving and adhesion characteristics. The qualitative analysis of this study agrees with the experience the railroads have had with their self-steering trucks. The findings of this study indicate that self-steering trucks can result in lower lateral forces, accommodate tighter curves, and deliver higher adhesion in curves; without lowering the critical hunting speed of the locomotive. The results further show that the steering mechanism stiffness can have a large effect on the lateral, longitudinal, and yaw stiffness between the end axles; therefore, significantly lowering curving forces, and increasing adhesion and critical hunting speed of the truck.