Effects of whole-body vertical shock-type vibration on human ability for fine manual control.

The effects of vertical (z-axis) whole-body shock-type vibration on the ability for fine manual control were examined. The amplitudes and frequency of the shocks was varied, but a constant frequency-weighted acceleration of 1.25 m/s2 r.m.s. was maintained. The examination of the shock's effects was carried out using an experimental system that simulated the actual workplace of earth-moving machinery. Control was measured using a first-order pursuit tracking-test, in which a seated subject was asked to use both hands to direct a cursor on a monitor using a steering wheel. Although the magnitude of shocks (peak amplitude of 6-10 m/s2) and the number of shocks per unit time (shock cycle of 10-40 s) were varied, and two types of shock (symmetric and asymmetric) used, no shock effect could be found by calculating an integrated square of tracking error during the whole exposure time. The tracking error only increased significantly during the moments that the subjects were exposed to a symmetrically shaped shock that reached the highest peak value (for the experiment) of 10 m/s2. The results suggested that shocks with peak amplitudes below defined value induce no evident effect on the steering of vehicles.     

Effects of gender differences on the subjective perceived intensity of steering wheel rotational vibration based on a multivariate regression model

The aims of this study were to determine equal sensation curves for hand–arm steering wheel rotational vibration and to investigate the effect of gender on the subjective perceived intensity of steering wheel hand–arm vibration. Psychophysical response tests of 40 participants (20 males and 20 females) were performed using a steering wheel rotational vibration simulator using the category-ratio Borg CR10 scale procedure for direct estimation of perceived intensity. The test stimuli were sinusoidal vibrations at 22 third octave band centre frequencies in the range from 3 to 400 Hz, with acceleration amplitudes in the range from 0.04 to 27 m/s² r.m.s. Multivariate regression procedures were applied to the experimentally acquired data in order to establish a regression model expressing the Borg CR10 perceived intensity values as a function of the two independent parameters of the frequency and amplitude of vibration. The equal sensation curves suggested a non-linear dependency of the subjective perceived intensity on both frequency and amplitude. Females were found to provide higher Borg CR10 perceived intensity values than males (p < 0.05), particularly at the higher intensity levels above approximately 1.0 m/s² r.m.s and at the higher frequencies above approximately 20 Hz.

Relevance to industry

For the manufacturers of steering systems and of other automobile components this study provides vibration perception curves and identifies the possible importance of gender towards the perception of vibration which arrives at the steering wheel.     

(Abstracts)Changing Industrial Demands

Abstract

The frequency dependence of discomfort caused by vertical mechanical shocks has been investigated with 20 seated males exposed to upward and downward shocks at 13 fundamental frequencies (1–16 Hz) and 18 magnitudes (±0.12 to ±8.3 ms^?2). The rate of growth of discomfort with increasing shock magnitude depended on the fundamental frequency of the shocks, so the frequency dependence of equivalent comfort contours (for both vertical acceleration and vertical force measured at the seat) varied with shock magnitude. The rate of growth of discomfort was similar for acceleration and force, upward and downward shocks, and lower and higher magnitude shocks. The frequency dependence of discomfort from shocks differs from that of sinusoidal vibrations having the same fundamental frequencies. This arises in part from the frequency content of the shock. Frequency weighting W_b in BS 6841:1987 and ISO 2631-1:1997 provided reasonable estimates of the discomfort caused by the shocks investigated in this study.

Practitioner Summary: No single frequency weighting can accurately predict the discomfort caused by mechanical shocks over wide ranges of shock magnitude, but vibration dose values with frequency weighting W_b provide reasonable estimates of discomfort caused by shocks similar to those investigated in this study with peak accelerations well below 1 g.     

The effects of horizontal load speed and lifting frequency on lifting technique and biomechanics

Lifting loads that have a horizontal velocity (e.g. lifting from a conveyor) is often seen in industry and it was hypothesised that the inertial characteristics of these loads may influence lifting technique and low back stress. Seventeen male participants were asked to perform lifting tasks under conditions of four horizontal load speeds (0 m/s, 0.7 m/s, 1.3 m/s and 2.4 m/s) and two lifting frequencies (10 and 20 lifts/min) while trunk motions and trunk muscle activation levels were monitored. Results revealed that increasing horizontal load speed from 0 m/s to 2.4 m/s resulted in an increase in peak sagittal angle (73° vs. 81°) but lower levels of peak sagittal plane angular acceleration (480°/s² vs. 4°/s²) and peak transverse plane angular acceleration (200°/s per s vs. 140°/s per s) and a consistent increase in trunk muscle co-activation. Participants used the inertia of the load to reduce the peak dynamics of the lifting motion at a cost of increased trunk flexion and higher muscle activity.

Statement of Relevance: Conveyors are ubiquitous in industry and understanding the effects of horizontal load speed on the lifting motions performed by workers lifting items from these conveyors may provide some insight into low back injury risk posed by these tasks.     

The effect of sinusoidal rolling ground motion on lifting biomechanics

The objective of this study was to quantify the effects of ground surface motion on the biomechanical responses of a person performing a lifting task. A boat motion simulator (BMS) was built to provide a sinusoidal ground motion (simultaneous vertical linear translation and a roll angular displacement) that simulates the deck motion on a small fishing boat. Sixteen participants performed lifting, lowering and static holding tasks under conditions of two levels of mass (5 and 10 kg) and five ground moving conditions. Each ground moving condition was specified by its ground angular displacement and instantaneous vertical acceleration: A): +6°, −0.54 m/s²; B): +3°, −0.27 m/s²; C): 0°, 0 m/s²; D): −3°, 0.27 m/s²; and E): −6°, 0.54 m/s². As they performed these tasks, trunk kinematics were captured using the lumbar motion monitor and trunk muscle activities were evaluated through surface electromyography. The results showed that peak sagittal plane angular acceleration was significantly higher in Condition A than in Conditions C, D and E (698°/s² vs. 612-617°/s²) while peak sagittal plane angular deceleration during lowering was significantly higher in moving conditions (conditions A and E) than in the stationary condition C (538-542°/s² vs. 487°/s²). The EMG results indicate that the boat motions tend to amplify the effects of the slant of the lifting surface and the external oblique musculature plays an important role in stabilizing the torso during these dynamic lifting tasks.     

The effect of sinusoidal rolling ground motion on lifting biomechanics

The objective of this study was to quantify the effects of ground surface motion on the biomechanical responses of a person performing a lifting task. A boat motion simulator (BMS) was built to provide a sinusoidal ground motion (simultaneous vertical linear translation and a roll angular displacement) that simulates the deck motion on a small fishing boat. Sixteen participants performed lifting, lowering and static holding tasks under conditions of two levels of mass (5 and 10 kg) and five ground moving conditions. Each ground moving condition was specified by its ground angular displacement and instantaneous vertical acceleration: A): +6°, −0.54 m/s²; B): +3°, −0.27 m/s²; C): 0°, 0 m/s²; D): −3°, 0.27 m/s²; and E): −6°, 0.54 m/s². As they performed these tasks, trunk kinematics were captured using the lumbar motion monitor and trunk muscle activities were evaluated through surface electromyography. The results showed that peak sagittal plane angular acceleration was significantly higher in Condition A than in Conditions C, D and E (698°/s² vs. 612–617°/s²) while peak sagittal plane angular deceleration during lowering was significantly higher in moving conditions (conditions A and E) than in the stationary condition C (538–542°/s² vs. 487°/s²). The EMG results indicate that the boat motions tend to amplify the effects of the slant of the lifting surface and the external oblique musculature plays an important role in stabilizing the torso during these dynamic lifting tasks.     

On the complexity of simulating space-bounded quantum computations

This paper studies the space-complexity of predicting the long-term behavior of a class of stochastic processes based on evolutions and measurements of quantum mechanical systems. These processes generalize a wide range of both quantum and classical space-bounded computations, including unbounded error computations given by machines having algebraic number transition amplitudes or probabilities. It is proved that any space s quantum stochastic process from this class can be simulated probabilistically with unbounded error in space O(s), and therefore deterministically in space O(s²).     

How the free limbs are used by elite high jumpers in generating vertical velocity

The aim of this study was to quantify how elite high jumpers used their free limbs in a competitive high jump and to estimate the contribution that these made to vertical take-off velocity. This was achieved by analysing the competitive performances of six elite male high jumpers using 3D motion analysis and assessing limb function using the relative momentum method. The mean peak relative momentum of the arm nearest to the bar at take-off was 9.4 kg m s^-1, while that of the arm furthest away from the bar was 11.3 kg m s^-1 and these did not differ significantly. The free (lead) leg reached a mean peak relative momentum of 20.9 kg m s^-1. At touch-down the free leg had a large positive relative momentum that was offset by the negative relative momentum of the arms, although their combined value still remained positive. The mean combined free limbs' relative momentum at touch-down was 13.8 kg m s^-1 and reached a peak of 37.6 kg m s^-1. The difference between these two values amounted to 7.1% of whole-body momentum, which was judged to be the amount by which the free limbs contributed to performance. The arms had a greater influence on performance than had the lead leg. This was because the lead leg increased its relative momentum little during the contact period while the arms had an initial negative value that increased markedly after touch-down. The compressive force exerted by the motion of the free limbs, estimated by the change in the combined free limbs' relative momentum, reached a mean peak of 366 N and was greatest at 37% of the contact period. It was concluded that to maximize the contribution the free limbs can make to performance, given the restraints imposed on technique by other performance requirements, the arms should have a vigorous downward motion at touch-down to make the most use of the high (but little changing) relative momentum of the lead leg.     

Whole body vibration exposure patterns in Canadian prairie farmers

Abstract

Whole body vibration is a significant physical risk factor associated with low back pain. This study assessed farmers’ exposure to whole body vibration on the Canadian prairies according to ISO 2631-1. Eighty-seven vibration measurements were collected with a triaxial accelerometer embedded in a rubber seat pad at the operator-seat interface of agricultural machinery, including tractors, combines, pickup trucks, grain trucks, sprayers, swathers, all-terrain vehicles, and skid steers. Whole body vibration was highest in the vertical axis, with a mean (range) frequency-weighted root mean squared acceleration of 0.43 m/s² (0.19?1.06 m/s²). Mean crest factors exceeded 9 in all 3 axes, indicating high mechanical shock content. The vertical axis vibration dose value was 7.55 m/s^1.75 (2.18?37.59 m/s^1.75), with 41.4% of measurements within or above the health guidance caution zone. These high exposures in addition to an ageing agricultural workforce may increase health risks even further, particularly for the low back.

Practitioner Summary: Agricultural workers are frequently exposed to whole body vibration while operating farm equipment, presenting a substantial risk to musculoskeletal health including the low back. Assessing vibration exposure is critical in promoting a safe occupational environment, and may inform interventions to reduce farmer’s exposure to vibration.     

Frequency-dependence of discomfort caused by vibration and mechanical shocks

The frequency content of a mechanical shock is not confined to its fundamental frequency, so it was hypothesised that the frequency-dependence of discomfort caused by shocks with defined fundamental frequencies will differ from the frequency-dependence of sinusoidal vibration. Subjects experienced vertical vibration and vertical shocks with fundamental frequencies from 0.5 to 16 Hz and magnitudes from ±0.7 to ±9.5 ms^–2. The rate of growth of discomfort with increasing magnitude of motion decreased with increasing frequency of both motions, so the frequency-dependence of discomfort varied with the magnitudes of both motions and no single frequency weighting will be ideal for all magnitudes. At the frequencies of sinusoidal vibration producing greatest discomfort (4–16 Hz), shocks produced less discomfort than vibration with same peak acceleration or unweighted vibration dose value. Frequency-weighted vibration dose values provided the best predictions of the discomfort caused by different frequencies and magnitudes of vibration and shock.

Practitioner Summary: Human responses to vibration and shock vary according to the frequency content of the motion. The ideal frequency weighting depends on the magnitude of the motion. Standardised frequency-weighted vibration dose values estimate discomfort caused by vibration and shock but for motions containing very low frequencies the filtering is not optimum.     

The accuracy of conventional 2D video for quantifying upper limb kinematics in repetitive motion occupational tasks

Marker-less 2D video tracking was studied as a practical means to measure upper limb kinematics for ergonomics evaluations. Hand activity level (HAL) can be estimated from speed and duty cycle. Accuracy was measured using a cross-correlation template-matching algorithm for tracking a region of interest on the upper extremities. Ten participants performed a paced load transfer task while varying HAL (2, 4, and 5) and load (2.2 N, 8.9 N and 17.8 N). Speed and acceleration measured from 2D video were compared against ground truth measurements using 3D infrared motion capture. The median absolute difference between 2D video and 3D motion capture was 86.5 mm/s for speed, and 591 mm/s² for acceleration, and less than 93 mm/s for speed and 656 mm/s² for acceleration when camera pan and tilt were within ± 30 degrees. Single-camera 2D video had sufficient accuracy ( < 100 mm/s) for evaluating HAL.

Practitioner Summary: This study demonstrated that 2D video tracking had sufficient accuracy to measure HAL for ascertaining the American Conference of Government Industrial Hygienists Threshold Limit Value^® for repetitive motion when the camera is located within ± 30 degrees off the plane of motion when compared against 3D motion capture for a simulated repetitive motion task.     

An algorithm for the retrieval of sea surface wind fields using X-band TerraSAR-X data

TerraSAR-X (TS-X) is a new, fully polarized X-band synthetic aperture radar (SAR) satellite, which is a successor of the Spaceborne Imaging Radar X-band Synthetic Aperture Radar (SIR-X-SAR) and the SRTM. TS-X has provided high-quality image products over land and oceans for scientific and commercial users since its launch in June 2007. In this article, a new geophysical model function (GMF) is presented to retrieve sea surface wind speeds at a height of 10 m (U ₁₀) based on TS-X data obtained with VV polarization in the ScanSAR, StripMap and Spotlight modes. The X-band GMF was validated by comparing the retrieved wind speeds from the TS-X data with in situ observations, the high-resolution limited area model (HIRLAM) and QuikSCAT scatterometer measurements. The bias and root mean square (RMS) values were 0.03 and 2.33 m s^?1, respectively, when compared with the co-located wind measurements derived from QuikSCAT. To apply the newly developed GMF to the TS-X data obtained in HH polarization, we analysed the C-band SAR polarization models and extended them to the X-band SAR data. The sea surface wind speeds were retrieved using the X-band GMF from pairs of TS-X images obtained in dual-polarization mode (i.e. VV and HH). The retrieved results were also validated by comparing with QuikSCAT measurements and the results of the German Weather Service (DWD) atmospheric model. The obtained RMS was 2.50 m s^?1 when compared with the co-located wind measurements derived from the QuikSCAT, and the absolute error was 2.24 m s^?1 when compared with DWD results.     

Vibration and shock exposure of maintenance-of-way vehicles in the railroad industry

The aim of this study is to investigate and compare vibration and shock measurements of maintenance-of-way vehicles used in the railroad industry for track maintenance and construction. Following international standards (i.e., ISO 2631-1: 1997) and professional guidelines the frequency weighted root-mean-square (r.m.s.) acceleration for each measurement axis, the vector sum, the seat effective amplitude transmissibility (SEAT), the crest factor (CF), the maximum transient vibration value (MTVV), the vibration dose value (VDV), the ratio and the newly proposed shock risk estimation factor ‘R’ for spinal injury according to ISO 2631-5:2004 were measured and calculated for seven different maintenance-of-way vehicles during revenue service. Furthermore, a proposed alternative spinal injury prediction method, the VibRisk model, which incorporates different typical driver postures and operator physical characteristics was included for comparison with the ISO 2631-5 risk prediction. The results of the vibration exposure measurements depended on vehicle type, track/surface conditions and seat properties, with the tamper and bulldozer showing the highest r.m.s. vibration values. The vector sum (a_v) results ranged from 0.37 to 0.99 (m/s²). Five of seven track maintenance vehicles would exceed the current Whole-body Vibration ACGIH-TLV^® guideline for an 8 h exposure duration in the vertical axis recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). The measured CF, MTVV/a_w and VDV/(a_w·T^1/4) ratios were at or above the critical ratios in the majority of measurements given by the ISO 2631-1 (1997) and American industry guidelines by the American Conference of Governmental Industrial Hygienists (ACGIH-TLV). Comparing both prediction models for vibration shock risk for parts of the lumbar spine, different risk predictions and inconsistencies were found. The VibRisk model generally suggests different and higher risk of vertebral endplate failure for individual lumbar levels, whereas the ISO 2631-5 model indicated generally lower risks and did not differentiate between different disk levels and driver posture. Epidemiological studies validating the different shock risk models are lacking. Work modifications and adequate suspension seats would be beneficial for prevention of harmful exposure to vibration and shocks.     

A new wind retrieval algorithm for Jason-1 at high wind speeds

The altimeter wind speed algorithm at high wind speeds remains unsolved because of lack of observed data. In this study data at high wind speeds were generated using Yin's typhoon model, which consists of the Rankine vortex model and the angular momentum model with typhoon parameters, provided by the Joint Typhoon Warning Centre (JTWC). The accuracy of Yin's typhoon model can be validated by comparing it with recorded data from a weather station. By comparing the normalized radar backscatter cross‐section (NRCS) detected by the Jason‐1 altimeter with wind speed data inferred by Yin's typhoon model, an empirical algorithm valid for a range of wind speeds between 10 and 40 m s^–1 is developed and proposed. The proposed algorithm is compared with the Jason‐1 operational algorithm and Young's altimeter wind retrieval algorithm. The study shows that, for the proposed algorithm and the operational algorithm for Jason‐1, the root mean square (RMS) errors are 3.38 and 3.60 m s^–1, respectively, and the average relative errors are 18% and 19%, respectively, for wind speeds less than 27 m s^–1. Hence, the proposed algorithm is in agreement with the operational algorithm for the Jason‐1 altimeter for wind speeds in the range 10–27 m s^–1. However, the Jason‐1 operational algorithm is inaccurate for wind speeds above 27 m s^–1 because the wind speeds used in the algorithm training process came from scatterometer wind products, and are significantly lower than those in strong wind and heavy rain conditions. Comparison of the proposed algorithm and Young's algorithm shows that the RMS errors are 6.27 and 15.18 m s^–1, respectively, and the average relative errors are 16% and 59%, respectively, for wind speeds greater than 20 m s^–1. The Holland typhoon model cannot accurately determine the outer wind field of typhoons since it extends cyclonic wind speeds to infinity. Young's altimeter wind retrieval algorithm depends on the Holland typhoon model, and the latter results in some errors. Compared with Young's altimeter wind retrieval algorithm, the proposed algorithm retrieves wind speeds with better accuracy. Therefore, the proposed algorithm, suitable for retrieving sea surface wind speeds in typhoons and other strong wind conditions, can be considered as supplementary to the Jason‐1 operational algorithm.     

An improved look-up table technique for geophysical parameters from SSM/I

An improved look-up table technique is developed to calculate meteorological parameters from Special Sensor Microwave/Imager (SSM/I) measurements. The method, which is based on a look-up table and an extrapolation and interpolation technique used in the weather prediction model, gives results comparable to or better than the regression method for the total precipitable water (TPW), surface wind speed (V), and cloud liquid water path (LWP). Applied to a noise-free data set (dependent test) TPW, V and LWP are retrieved with a rms. accuracy of 0.26 kg m^-2, 0.28 m s^-1 and 0.002 kg m^-2, respectively. If the random noise of the SSM/I radiometer is taken into account in the retrieval, the r.m.s. increases to 0.84 kg m^-2, 1.08 m s^-1 and 0.013 kg m^-2, respectively. The method is applied to a set of over 520 SSM/I measurements from the DMSP-F8 satellite for which collocated radiosondes launched from ships are available. The rms. (bias) of TPW and V was 2.91 (-0.61) kg m^-2 and 2.75 (-0.13) m s^-1, respectively. We use the improved look-up table technique to calculate the monthly mean global distribution of surface wind for August 1989 and compare the results with the Comprehensive Ocean-Atmosphere Data Set (COADS) for the same month. The rms. error and mean differences for the monthly mean values of sea surface wind speed between the retrievals and COADS data are 1.01 m s^-1 and 0.03 m s^-1, respectively. We also calculate LWP for October 1987 and compare it with the LWP derived from cloud optical thicknesses of International Satellite Cloud Climatology Project (ISCCP) dataset. Good agreement is obtained. The extension of the method to calculate cloud water and water vapour profiles is discussed.     

Power hand tool vibration effects on grip exertions

Operation of vibrating power hand tools can result in excessive grip force, which may increase the risk of cumulative trauma disorders in the upper extremities. An experiment was performed to study grip force exerted by 14 subjects operating a simulated hand tool vibrating at 9.8 m/s² and 49 m/s² acceleration magnitudes, at 40 Hz and 160 Hz frequencies, with vibration delivered in three orthogonal directions, and with 1.5kg and 3.0kg load weights. Average grip force increased from 25.3 N without vibration to 32.1 N (27%) for vibration at 40 Hz, and to 27.1N (7%) for vibration at 160 Hz. Average grip force also increased from 27.4 N at 9.8 m/s² acceleration to 31.8 N (16%) at 49m/s². Significant interactions between acceleration x frequency, and frequency x direction were also found. The largest average grip force increase was from 25.3N without vibration to 35.8N (42%) for 40 Hz and 49 m/s² vibration. The magnitude of this increase was of the same order as for a two-fold increase in load weight, where average grip force increased from 22.5N to 35.0N (56%). A second experiment studied hand flexor and extensor muscle responses using electromyography for five subjects holding a handle vibrating at 8 m/s² using ISO weighted acceleration, with frequencies of 20 Hz, 40 Hz, 80 Hz and 160 Hz, and grip forces of 5%, 10% and 15% of maximum voluntary contraction. Muscle responses were greatest at frequencies where grip force was affected, indicating that the tonic vibration reflex was the likely cause of increased grip exertions.     

Enstrophy budget in decaying compressible turbulence

The interaction of vorticity and shock waves in decaying compressible turbulence is investigated by direct numerical simulation of the Navier-Stokes equation using a spectral method with 64³ collocation points. The Taylor microscale Reynolds number decreases from 36 to 17 and the rms Mach number from 0.8 to 0.4 during the decay. It is observed that vorticity is created inside curved shocks through baroclinic interaction and intensified by the compression of fluid elements. Vortex stretching is, on the other hand, dominant outside shocks and is responsible for enhancing the strength of vorticity. A dipole of vorticity is typically created at the vertex of curved shocks, the structure of which is explained in terms of jump relations of velocity derivatives across a curved shock.     

Variations of surface boundary layer parameters associated with Cyclone Gonu over the Arabian Sea using QuikSCAT data

This study attempted to quantify the variations of the surface marine atmospheric boundary layer (MABL) parameters associated with the tropical Cyclone Gonu formed over the Arabian Sea during 30 May–7 June 2007 (just after the monsoon onset). These characteristics were evaluated in terms of surface wind, drag coefficient, wind stress, horizontal divergence, and frictional velocity using 0.5° × 0.5° resolution Quick Scatterometer (QuikSCAT) wind products. The variation of these different surface boundary layer parameters was studied for three defined cyclone life stages: prior to the formation, during, and after the cyclone passage. Drastic variations of the MABL parameters during the passage of the cyclone were observed. The wind strength increased from 12 to 22 m s^?1 in association with different stages of Gonu. Frictional velocity increased from a value of 0.1–0.6 m s^?1 during the formative stage of the system to a high value of 0.3–1.4 m s^?1 during the mature stage. Drag coefficient varied from 1.5 × 10^?3 to 2.5 × 10^?3 during the occurrence of Gonu. Wind stress values varied from 0.4 to 1.1 N m^?2. Wind stress curl values varied from 10 × 10^?7 to 45 × 10^?7 N m^?3. Generally, convergent winds prevailed with the numerical value of divergence varying from 0 to –4 × 10^?5 s^?1. Maximum variations of the wind parameters were found in the wall cloud region of the cyclone. The parameters returned to normally observed values in 1–3 days after the cyclone passage.     

四轮转向车辆转向解耦的双点跟踪控制

针对四轮转向(4WS)无人车辆路径跟踪中的过约束问题, 本文提出一种前后轮转向解耦的双点跟踪控制策略. 建立4WS车辆单轨运动学模型, 约束前后轮转向角速度, 规划曲率连续的回旋曲线参考位姿序列, 将其解耦为前后轴中心的双点参考轨迹; 以前后轮中心点为控制点, 采用非线性反馈控制的预瞄方法分别获得转向控制率, 双点跟踪误差指数收敛于0. 仿真和实车验证结果表明, 所提出的双点跟踪控制策略横向误差标准差减少0.2 m, 横摆角误差标准差减小3.0?, 具有更大的前后轮转角控制域和较高的跟踪精度     

Numerical comparison of steering geometries for robotic vehicles by modeling positioning error

This paper describes an analytical method for modeling the positioning error of a robotic vehicle and examines how the metric of this error can be used to compare the geometries of various steering configuration. Positioning error can be caused by many factors stemming from the robot’s hardware and software configurations and the interaction between the robot and its environment. A slip motion model that captures the effects of key factors that contribute to positioning error is presented. Robot kinematic models with and without slippage are reformulated and used to perform an in-depth assessment and characterization of positioning error. The method is applied to three characteristic advance and steering configurations: Ackermann, articulated, and explicitly steered. This analysis serves as a quantitative evaluation of the properties of the steering geometries for path tracking under identical slippage conditions. The method can also be used as a tool for comparing robot configurations to make trade-off decisions early in the design process, as it allows for derivation of predicted performance values of alternative steering geometries.