Instantaneous Center Research Articles

An Exploratory Study of a Choreographic Approach to Golf Swing Dynamics: Bridging Biomechanics and Laban Movement Analysis

This study introduces an innovative integration of Laban Movement Analysis (LMA) with biomechanical principles to examine the golf swing dynamics from an ecological perspective. Traditionally, LMA focuses on the qualitative aspects of movement, often isolated from external influences. This research bridges that gap by investigating how golfers manage and adapt to the inertial forces of the club throughout the swing. Using motion tracking sensors and screw theory, we analyzed the spatial movement pattern in the Kinesphere (mapped as an icosahedron) and related it to force dynamics in the Effort Cube through the inertia tensor. The results showed significant differences between skilled and novice golfers in terms of how efficiently they align their movements with the club’s inertia. Skilled golfers demonstrated smoother Instantaneous Screw Axes (ISAs) and better synchronization with inertia forces, while novice golfers exhibited more abrupt deviations. These findings suggest that integrating qualitative movement descriptors with biomechanical models provides deeper insights into swing efficiency, performance improvement, and injury prevention. This combined framework offers a novel method to enhance both qualitative and quantitative analysis of golf swings.

Enhancing Maneuverability in a Variable Wheelbase Wheeled Mobile Robot Through Dynamic Steering Curvature Control

ABSTRACTVariable wheelbase wheeled mobile robot (VW‐WMR) is capable of maneuvering flexibly and traversing on rough and soil terrains within confined spaces. While the steering radius of the robot model can be robustly changed by the variable wheelbase length, a challenge is posed in accurately tracking a predefined trajectory through the alteration of wheelbase length. A dynamic steering curvature (DSC) control method is proposed in this work to overcome this challenge, which is achieved by two different approaches utilizing the variable wheelbase length and manipulating drifting motions. First, to enable flexible trajectory adjustments, a 3D Ackermann kinematics model, incorporating the lifting motion of the robot box, is developed to control steering curvature by the changes in wheelbase length. Second, to achieve flexible movement for the inner and outer curves of the originally planned curvilinear trajectory, Ackermann drift models are presented by the establishment of two sequence instantaneous centers. Furthermore, the control performance of DSC is validated through simulation experiments on the ROSTDyn Vortex platform, using a six‐wheeled VW‐WMR named HIT‐MRII robot. The effectiveness of DSC for strategically altering the robot's motion trajectory is demonstrated by the results, which show the relation between the changed trajectory position and the variation in wheelbase length, and the variation in the radii of the instantaneous centers (ICs) in the Ackermann drift model, respectively. In addition, the high maneuverability of the robot using the Ackermann model is proven by physical experiments during steering motions on soil terrain. A comprehensive advantage is demonstrated by the results via Ackermann models, which include shorter runtimes, moderate travel distances, and moderate variations in force on the wheels, compared to different velocity, crabbing motion, and equivalent bicycle models.

Trajectory tracking control of underwater tracked vehicle considering ICR longitudinal deviation compensation

During the operation of an underwater tracked vehicle on a soft substrate, the instantaneous center of rotation (ICR) no longer coincides with the geometric center after the longitudinal offset is accounted for by the external environment. Due to this, designing an underwater trajectory tracking system based on a kinematic model is a challenging task. In order to achieve the high-precision trajectory tracking control of underwater tracked vehicles, this paper proposes a trajectory tracking algorithm based on the kinematic model of tracked vehicles. First, an inverse tangent algorithm is proposed to address the problem that the front viewpoint of the Stanley algorithm may not be on the target path and cause deviation. Second, by using the inverse tangent algorithm to introduce the target bow angle, as well as combining the mechanisms by which biological endocrine hormones are regulated with the advantages of single-neuron proportional–integral–derivative (PID), a composite endocrine intelligent control law is proposed for the design of the lateral control law of an underwater tracked vehicle; a longitudinal control law is designed based on the longitudinal offset of the ICR obtained by the estimation of the unscented Kalman filter as a means of compensating for longitudinal errors. Finally, a kinematic model is used in order to determine the desired drive wheel speed of the underwater tracked vehicle. The method is compared with the method without longitudinal deviation compensation, then with the methods presented in related literature, and finally, a certain degree of experimental validation is carried out. These results validate the effectiveness of the proposed method.

Dynamic model of single-DOF spherical mechanisms based on instantaneous pole axes and Eksergian's equation

Instantaneous pole axes (IPAs) fully describe instantaneous kinematics of spherical mechanisms. In single-degree-of-freedom (single-DOF) mechanisms, IPAs’ locations uniquely depend on the mechanism configuration. Such a property allows the deduction of instantaneous-motion characteristics by means of analytic techniques based on geometric features of the mechanism configuration. Moreover, these geometric/analytic approaches are extendable to mechanism's static analyses since the virtual work principle relates mechanism's statics to its instantaneous kinematics. Analytic approaches based on geometric reasoning are of interest in mechanism design and their further extension to dynamic analyses is appealing in that context. This work proposes a possible extension of IPA-based techniques to dynamic analyses of single-DOF spherical mechanisms by using Eksergian's equation. A novel general dynamic model for single-DOF spherical mechanisms is proposed, which is based on IPAs’ locations. Then, the effectiveness of the proposed model is applied to a relevant single-DOF spherical mechanism.

Experimental evaluation and design of fillet welds under in-plane eccentric loads

The principal objective of this investigation is to furnish equations to compute the design strength of fillet welds under in-plane eccentric loads suitable for load and resistance factor design (LRFD) applications. Over the years, experimental and analytical techniques have been used to arrive at safe estimates for the strength of such welds in common practical applications. The conventional elastic design (ED) method is very conservative and is not compatible with the LRFD design philosophy. In addition, the ED method neglects the weld group's ductility and strain compatibility. On the other hand, the instantaneous center of rotation (IC) method considers the above parameters but requires complex calculations. In the present study, a method for designing fillet welds under eccentric loading is introduced called the plastic design (PD) method. This method considers the inelastic properties of the welds in a simple manner while providing an accurate prediction of the weld group's capacity. The performance of the proposed PD method was compared with the IC method for several cases. The ultimate loads obtained were mostly within 10% difference on the conservative side and only marginally different for a few. Additionally, the fillet weld group's resistance under in-plane eccentric loads was evaluated experimentally using 12C-shaped specimens with the load applied at different angles of 0, 45, and 75°. The test results also confirmed the efficacy of the proposed PD method in evaluating the design strength of such weld groups.

Film thickness characterization in dual-axis spin coating of a sphere

The versatility of spin coating technology makes it a preferred method for producing the thin film layers used to manufacture products from solar panels and smartphones to sunglasses and CDs. However, the process requires a flat, rigid substrate to produce uniform films, which limits its use to planar devices. A novel multi-axis manipulator has been developed to extend the application of spin coating, enabling controlled thin film deposition onto curved surfaces. Various rotational schemes were studied to link the flow of a liquid film over a curved surface to forces induced by complex rotational dynamics. When the angular velocity exceeds a threshold, centrifugal force dominates the flow, pushing the fluid away from the instantaneous axis of rotation. This produces axisymmetric coating profiles when using consistent single or dual-axis rotation. Areas of near uniformity present around the spin axis poles for single-axis rotation and around the substrate’s equator for dual-axis schemes. Sensitivities between the spherical substrate dynamics and the evolving fluid flow were investigated, exploring the parameters that promoted the production of uniform curved film layers for microfabrication processes. This enabled the evolution of the spin coating technique to effectively form curved polymer coatings with improved thickness control. The presented research outlines the capabilities of a multi-axis spin coating machine when used to coat spherical substrates. Therefore, enabling the use of fluid mechanics models to identify the optimal motion kinematics required to create uniform curved films.

Design and optimization of lower limb exoskeleton based on multi-axis knee joint

PurposeThe purpose of this paper is to improve the problem of kinematics incompatibility of human–exoskeleton in the existing rigid lower-limb exoskeleton (LLE).Design/methodology/approachIn this paper, following an introduction, the motion characteristics of the human knee joint and the design method of the exoskeleton were introduced. A kinematics model of the LLE based on cross-four-bar linkage was obtained. The structural parameters of the LLE mechanism were optimized by the particle swarm optimization algorithm. The predefined trajectories used in the optimization process were derived from the ankle joint, not the instantaneous center of rotation of the knee joint. Finally, the motion deviation of the optimization result was simulated, and the human–exoskeleton coordination experiment was designed to compare with the traditional single-axis knee joint in terms of comfort and coordination.FindingsThe lower limb exoskeleton mechanism obtained in this paper has a good tracking effect on human movement and has been improved in terms of comfort and coordination compared with the traditional single-axis knee joint.Originality/valueThe customized exoskeleton design method introduced in this paper is relatively simple, and the obtained exoskeleton has better movement coordination than the traditional exoskeleton. It can provide a reference for the design of lower limb exoskeleton and lower limb orthosis.

Computational assessment of carbon fabric reinforced polymer made prosthetic knee: Mechanics, finite element simulations and experimental evaluation.

A prosthetic knee is designed to replace the functionality of an anatomical knee in transfemoral amputees. The purpose of a prosthetic knee is to restore mobility and compensate amputees for their impairment. In the present research numerical modelling and simulation of a carbon fabric reinforced polymer made polycentric prosthetic knee with four-bar mechanism was performed. Virtual prototyping with computer-aided design and computer-aided engineering software ensured geometric and structural stability of the knee design. The linkage mechanism, instantaneous centre's location and trajectory were investigated using multibody dynamics and analytical formulations. Computational simulations with a non-linear finite element model were employed with joints, contact formulations and an orthotropic material model to predict the displacement, stress formulated and life of the knee prosthesis under static and cyclic loading conditions. Finite element analysis assessed the strength and durability of knee in accordance to standards. Maximum Principal stress of 155 MPa and life expectancy of 3.1 × 106 cycles were determined for the composite knee through numerical simulations ensuring a safe design. Experimental testing was also conducted as per standards and the percentage error was estimated to be 2.52%, thereby establishing the validity of the finite element model deployed. This type of simulation-based approach can be implemented to efficiently and affordably design and prototype a prosthetic knee with desired functioning criteria.

A study of the instantaneous centers of velocity for 1-dof and 2-dof planar linkages

This paper presents a detailed study of the instantaneous centers of velocity (henceforth referred to as instant centers) and the lines containing the instant centers for one-degree-of-freedom (1-dof) and two-degree-of-freedom (2-dof) planar linkages with up to 11 links. The focus is on graphical methods to locate secondary instant centers (that is, instant centers which are unknown from inspection and require graphical construction) or the lines containing secondary instant centers. The secondary instant center for a pair of links with one relative degree of freedom is a unique point, and for a pair of links with two relative degrees of freedom the secondary instant center must lie on a unique line. For a 2-dof linkage, the problem of finding the unique locations of the secondary instant centers on these lines is not addressed in this paper (this would correspond to knowing the ratio of the two input velocities). The paper reviews known graphical methods for the 4-bar, 5-bar, 6-bar, and 7-bar linkages and then presents original graphical methods to locate the secondary instant centers for the 1-dof 8-bar and 10-bar linkages, and the lines containing the secondary instant centers for the 2-dof 9-bar and 11-bar linkages.

The effect of different mechanism combinations on sliding between brace and lower limb during walking and leg-raising.

Knee braces are commonly used to support the knee joint and improve function. However, brace sliding caused by the misalignment between brace and knee during motion is a common problem, which reduces the therapeutic effect and leads to brace abandonment. To investigate the effect of mechanism combinations on sliding, an experimental brace was designed to isolate the mechanism as the sole variable. Ten healthy participants were recruited, each of whom worn four combinations of lateral/medial mechanisms: lateral and medial single-axis (SA), lateral super gear (SG) and medial non-circular gear (NCG), lateral four-bar linkage (FL) and medial SG, and lateral FL and medial NCG. The knee flexion angle was collected using inertial measurement units, and brace sliding was measured by 3D motion capture system. All combinations had significant changes in peak sliding of thigh and shank compared to the SA combination (p < 0.05), but lateral FL and medial NCG combination had the lowest peak and final sliding during walking and leg-raising, with significant reductions of 40.7 and 85.3% in peak sliding of thigh, and significant reductions of 56.3 and 72.0% in peak sliding of shank, respectively (p < 0.05). Moreover, the mechanism combination did not significantly impact the knee range of motion (p > 0.05). The mechanism combination that fit the instantaneous center of rotation of lateral/medial condyle of knee joint demonstrates a significant reduction in brace sliding. Additionally, the peak sliding during motion is significantly higher than the final sliding.

A unified analytical disk cam profile generation methodology using the Instantaneous Center of Rotation for educational purpose

Cam design is a fundamental part of the Mechanism and Machine Theory (MMT) and is included in the vast majority of MMT books. Cam profile design is usually determined with graphical and analytical methods. Graphical methods are didactically very successful to introduce the theory of cam profile generation in a simple way. In turn, analytical methods allow computer implementations of cam profile generation in order to reproduce it accurately. Most modern MMT books describe analytical methods using geometric equations and envelope theory. However, the analytical profile definition depends on the specific type of follower and there is a lack of a general formulation. This work presents a unified and general analytical formulation for the disk cam profile determination. Based on the Instantaneous Center of Rotation and the kinematic inversion, the formulation provides analytical expressions of the cam profile and is applicable to any type of follower. Thus, the unified formulation can be used in forthcoming books on this discipline.

A physics-guided machine learning framework for real-time dynamic wake prediction of wind turbines

Efficient and accurate prediction of the wind turbine dynamic wake is crucial for active wake control and load assessment in wind farms. This paper proposes a real-time dynamic wake prediction model for wind turbines based on a physics-guided neural network. The model can predict the instantaneous dynamic wake field under various operating conditions using only the inflow wind speed as input. The model utilizes Taylor's frozen-flow hypothesis and a steady-state wake model to convert instantaneous inflow wind speed and turbine parameters into neural network input features. A deep convolutional neural network then maps these features to desired wake field snapshots, enabling dynamic wake predictions for wind turbines. To train the model, we generated approximately 255 000 instantaneous flow field snapshots of single-turbine wakes using the large eddy simulation, covering different thrust coefficients and yaw angles. The model was trained using the supervised learning method and verified on the test set. The results indicate that the model can effectively predict the dynamic wake characteristics, including the dynamic wake meandering and the wake deflection of the yawed turbines. The model can also assess both the instantaneous wake velocity and the instantaneous wake center of a wind turbine. At a thrust coefficient of 0.75, the root mean square error for the predicted instantaneous wake velocity is around 6.53%, while the Pearson correlation coefficient for the predicted instantaneous wake center can reach 0.624. Furthermore, once the model is trained, its prediction accuracy does not decrease with the increase in the time span.

The influence of rotator cuff tear type and weight bearing on shoulder biomechanics in an ex vivo simulator experiment

Glenohumeral biomechanics after rotator cuff (RC) tears have not been fully elucidated. This study aimed to investigate the muscle compensatory mechanism in weight-bearing shoulders with RC tears and asses the induced pathomechanics (i.e., glenohumeral translation, joint instability, center of force (CoF), joint reaction force).An experimental, glenohumeral simulator with muscle-mimicking cable system was used to simulate 30° scaption motion. Eight fresh-frozen shoulders were prepared and mounted in the simulator. Specimen-specific scapular anthropometry was used to test six RC tear types, with intact RC serving as the control, and three weight-bearing loads, with the non-weight-bearing condition serving as the control. Glenohumeral translation was calculated using instantaneous helical axis. CoF, muscle forces, and joint reaction forces were measured using force sensors integrated into the simulator. Linear mixed effects models (RC tear type and weight-bearing) with random effects (specimen and sex) were used to assess differences in glenohumeral biomechanics.RC tears did not change the glenohumeral translation (p > 0.05) but shifted the CoF superiorly (p ≤ 0.005). Glenohumeral translation and joint reaction forces increased with increasing weight bearing (p < 0.001). RC and deltoid muscle forces increased with the presence of RC tears (p ≤ 0.046) and increased weight bearing (p ≤ 0.042).The synergistic muscles compensated for the torn RC tendons, and the glenohumeral translation remained comparable to that for the intact RC tendons. However, in RC tears, the more superior CoF was close to where glenoid erosion occurs in RC tear patients with secondary osteoarthritis. These findings underscore the importance of early detection and precise management of RC tears.

Prevertebral Anchored Kevlar Band to Recover Intact Spine Movement Ranges in Lumbar Disc Arthroplasty

Anterior longitudinal ligament and annulus fibrosus removal in total disc replacement induces excessive spinal mobility with zygapophyseal joint overload and osteoarthritic changes causing chronic back pain. To control disc arthroplasty-induced hypermobility with a Kevlar® band. A 3 × 3 cm Kevlar® band implanted in twelve human lumbar cadaveric spines substituted the anterior longitudinal ligament and annulus in disc arthroplasty. Biomechanical studies compared the intact spine, after discectomy, post-disc arthroplasty, and with the Kevlar® band inserted. The Kevlar® band recovered the extension and axial rotation movement ranges without regaining the intact status. Improvement was moderate in lateral bending. The Instantaneous Axis of Rotation improved the discectomy and total disc prosthesis conditions without recovering the initial state. The disc above the operated one also showed increased mobility, particularly in extension and axial rotation, improved by Kevlar® band insertion without recovering the intact spine values. The Kevlar® band improves excess mobility ranges induced by anterior longitudinal ligament and anterior annulus removal in disc arthroplasty in the operated and supra-adjacent discs without recovering the baseline status.

Effect of forward kinematics on the motion-trajectory oscillations and inertia forces

In vehicle-motion scenarios, non-negligible centrifugal-force component that cannot be balanced by the gravity force may develop, leading to increase in wheel-contact forces. This inertia-force component, which depends on vehicle forward velocity and oscillation amplitude, can arise when the vehicle negotiates straight road or railroad track. An approach based on the Frenet geometry and recorded motion trajectory (RMT) is introduced in this investigation to examine forward-kinematics effect on the motion geometry and inertia forces and to obtain general expression of the ratio between the amplitudes of the centrifugal and gravity forces. While the two three-dimensional vectors of applied and constraint forces define Frenet osculating plane of mass-center trajectories; for non-centroidal points, the osculating plane is defined by two vectors; the resultant of the applied and constraint forces and an inertia-force vector that depends on the angular velocity and angular acceleration. The concepts of instantaneous motion plane (IMP) and instantaneous zero-force axis (IZFA) are used to convert three-dimensional Cartesian forces into two-dimensional Frenet forces, based on the Frenet-Newton equations. Because contact forces can be formulated using two fundamentally different approaches; constraint contact formulation (CCF) and elastic contact formulation (ECF), the effect of the contact formulation on the IMP and IZFA orientation is examined. The results obtained, using railroad suspended wheelset example, demonstrate the following: (1) limitations of roller rigs that do not properly account for forward-velocity effect on the inertia forces; (2) difference between IMP and intermediate wheelset plane defined by wheelset lateral axis and global vertical axis; (3) non-negligible inertia centrifugal-force component in the absence of physical curvature; and (4) need to distinguish between physical and motion geometries; the latter is one that directly enters into the definition of the inertia forces. Trajectories with oscillation frequency independent of the oscillation amplitude for a given forward velocity are also identified.

Realization and Control of Robotic Injection Prototype With Instantaneous Remote Center of Motion Mechanism.

Although there have been studies conducted on the instantaneous remote center of motion (RCM) mechanism, the general closed-loop control method has not been studied. Thus, this article fills that gap and employs the advantages of this mechanism to develop a novel injection system. The injection prototype involves the instantaneous RCM mechanism, insertion unit and injection unit. The RCM system is investigated in the presence of time-varying axial stiffness of the screw drive and underactuated case. For safe interaction, compliance control is designed in the insertion system. The stability of all separate systems is investigated with the bounded parameter variation rate. The injection prototype and a robot end-effector were then combined to perform injection. Our RCM prototype can achieve a large workspace, and its control effectiveness was verified by multiple frameworks and comparison with previous studies. Compliance-controlled insertion can achieve accurate depth regulation and zero-impedance control for manually operating the needle. With the help of three-dimensional reconstruction and hand/eye calibration, the manipulator can guide the injection prototype to a proper pose for injection of a face model. The injection prototype was successfully designed. The effectiveness of the whole control system was verified by simulations and experiments. The particular robotic injection task can be performed by the prototype. This article provides alternative schemes for developing an instantaneous RCM system, screw drive-based surgical tool, and robotic insertion with small needles.

Effect of center of rotation of angulation-based levelling osteotomy on instantaneous center of rotation ex vivo

Cranial cruciate ligament rupture is a common cause of femorotibial instability in dogs. Despite numerous techniques being described for achieving joint stabilization, no consensus exists on the optimal management strategy. This ex vivo study utilized the path of the instantaneous center of rotation (ICR) to compare normal, pathological and treated joints. Fluoroscopic recordings of seven limbs from a previous study of canine stifle joint stability following center of rotation of angulation-based levelling osteotomy (CBLO) with and without hamstring loading were analyzed using least-squares approximation of the ICR and estimation of percentage gliding (vs. rolling) to determine if alterations in ICR path and gliding caused by CCL transection and following meniscal release could be normalized by CBLO. In intact joints, the ICR path was located mid-condyle, but this shifted significantly proximally and caudally following CCL transection and medial meniscal release (p < 0.007, p < 0.04). Hamstring loading resulted in qualitative and some quantitative improvements in joint movement based on percentage gliding movement analysis. The ICR path after CBLO remained significantly different to the intact location with or without a hamstring load (p < 0.02, p < 0.04), potentially consistent with CBLO aims of mild residual instability. CBLO resulted in percentage gliding characteristics not significantly different to intact joints (p > 0.08). Qualitative improvements in ICR path and percentage gliding quantities and variability suggest that hamstring loading positively influences joint biomechanics and that further investigation of this role ex vivo and clinically is warranted.

An interaction model for predicting brace migration and validation through walking experiment

Brace migration undermines therapeutic efficacy, which is traditionally evaluated through walking experiments. This study developed an interaction model that considered the instantaneous center of rotation (ICR) misalignment to predict migration. The model was validated by walking experiment. Results show a strong positive correlation for four-linkage (FL) (r = 0.952, p < 0.01, root mean squared error (RMSE) = 0.53 mm) and spur gear (SG) (r = 0.898, p < 0.01, RMSE = 1.35 mm) mechanisms. The FL exhibits lower migration than SG (p < 0.05). In conclusion, the interaction model accurately predicts migration, emphasizing the influence of mechanism on migration.

Cadaveric biomechanical studies of ADDISC total lumbar disc prosthesis

BackgroundMost total disc replacements provide excessive mobility and not reproduce spinal kinematics, inducing zygapophyseal joint arthritic changes and chronic back pain. In cadaveric lumbosacral spines, we studied if a new lumbar disc prosthesis kinematics mimics the intact intervertebral disc. MethodsIn eight cold preserved cadaveric lumbosacral spines, we registered the movement ranges in flexion, extension, right and left lateral bending, and rotation in the intact status, post-discectomy, and after our prosthesis implantation, comparing them for each specimen. FindingsComparing the intact lumbosacral spine with the L4-L5 prosthesis implanted specimens, we saw statistically significant differences in lateral bending and right rotation but not in the full range of rotation. Analyzing segments, we also noticed statistically significant differences at L4-L5 in flexion-extension and rotation. On the other hand, the L4-L5 discectomy, compared to the baseline spine condition, showed a statistically significant mobility increase in flexion, extension, lateral bending, and axial rotation, with an abnormal instantaneous center of rotation, which destabilizes the segment partly due to anterior annulus surgical removal. Disc prosthesis implantation reversed these changes in instantaneous center of rotation, but the prosthesis failed to restore the initial range of motion due to the destabilization of the ligaments in the operated disc. InterpretationThe ADDISC total disc replacement reproduces the intact disc kinematics and Instantaneous Center of Rotation, but the prosthesis fails to restore the initial range of motion due to ligament destabilization. More studies will be necessary to define a technique that restores the damaged ligaments when implanting the prosthesis.

An estimation method for dynamic vehicle turn center

The instantaneous vehicle turn center is of great significance in the design and analysis of vehicle steering and handling. Due to the influences of vehicle flexible components, the vehicle turn center is not intersected at one point and the traditional determination method for vehicle turn center is not applicable for multi-axle vehicles. In this paper, a novel instantaneous tire turn center (TTC) method is proposed to estimate the instantaneous vehicle turn center to provide a guidance for the design of vehicle steering and analysis of handling. The motivation of the tire turn center concept is introduced and the calculation method is developed. The instantaneous vehicle turn center is estimated based on the calculation of instantaneous TTC. The estimation results of the vehicle turn center of a two-axle vehicle and a three-axle off-road vehicle under different vehicle velocities and lateral accelerations during steering are presented based on the vehicle dynamics models built by ADAMS software. Since there is no simplifications of the vehicle in the proposed estimation method, the determined instantaneous vehicle turn center is more accurate and can reflect the actual vehicle motion better as compared to the traditional vehicle turn center in transient motion process. The estimated instantaneous vehicle turn center provides a guidance for design and optimization of vehicle steering as well as steering angles control strategies to make all tire turn centers controlled at the instantaneous vehicle turn center, thus reducing tire wears and improving the whole vehicle steering coordination performance.