Propulsion Dynamic Requirements Analysis for Multi-Axle Skid-Steer Wheeled Vehicles

2020 ◽  
Author(s):  
Mostafa Yacoub ◽  
Ahmed Ali
Keyword(s):  
Experimental Validation ◽  
Worst Case ◽  
Wheeled Vehicle ◽  
Wheel Drive ◽  
System Requirements ◽  
Turning Radius ◽  
Four Wheel Drive ◽  
Driving Torque ◽  
Wheeled Vehicles ◽  
Selection Of

Abstract Multi-axle skid-steer wheeled vehicles have the advantages of simplicity and enhanced traction. That’s why they are used in off-road environments and also in mobile robots. In the present work, a dynamic analysis of the propulsion system requirements for multi-axle wheeled vehicles is investigated. As the multi-axle wheeled vehicle differentially steers at a smaller turning radius, the driving torque requirements approach their peak. The adhesion at each tire of the multi-axle vehicle and its relation to the contact patches are analyzed. The analysis presented starts with four wheel drive, six wheel drive and eight wheel drive vehicles, then it is widened to n-wheel drive vehicles. A generic formula for obtaining the propulsion torque requirements for multi-axle skid-steer wheeled vehicles is presented. The analysis is extended to include experimental validation of the obtained analytical results. The experimental work includes three small electrically driven skid-steer vehicles; four wheel drive vehicle, six wheel drive vehicle and eight wheel drive vehicle. The selection of the drive motors for each of those vehicles was based on the proposed formula. Each of the three vehicles was tested in the worst case adhesion torque requirement. The experimental results showed that the proposed formula is capable, to a great extent, to predict the torque requirements for the multi-axle skid-steer wheeled vehicles in the design phase.

PWM Control Accuracy for Scratch Drive Actuators

2010 ◽  
Author(s):  
Jenelle Armstrong Piepmeier ◽  
Samara L. Firebaugh
Keyword(s):  
Open Loop ◽  
Open Loop Control ◽  
Forward Motion ◽  
Loop Control ◽  
Wheeled Vehicle ◽  
Straight Line ◽  
Fixed Radius ◽  
Turning Radius ◽  
Wheeled Vehicles ◽  
Control Accuracy

In this paper we investigate the problem of controlling a scratch drive actuator that has two discrete modes of locomotion: forward motion in a straight line, and forward motion with fixed radius curvature. This type of device can be modeled as a two-wheeled vehicle (with the previously stated constraints). By alternating between these two modes of operation, the device can move along a variable-radius curved path. In practice, the robots do not move in a purely straight manner. This paper seeks to quantify the accuracy that can be achieved by switching between the two modes of locomotion. This type of low-level open-loop control facilitates the use of a higher level feedback controller designed for two-wheeled vehicles with a variable turning radius.

Optimization of the tractive performance of four-wheel-drive tractors: Theoretical analysis and experimental substantiation

1998 ◽  
Vol 212 (4) ◽  
pp. 285-297 ◽  
Author(s):  
J. Y. Wong ◽  
N. B. McLaughlin ◽  
Z Knezevic ◽  
S Burtt
Keyword(s):  
Theoretical Analysis ◽  
Field Test ◽  
Angular Speed ◽  
Speed Ratio ◽  
Torque Distribution ◽  
Wheel Drive ◽  
Four Wheel Drive ◽  
Tractive Efficiency ◽  
Driving Torque ◽  
Experimental Substantiation

The results of a theoretical analysis reveal that, for a four-wheel-drive tractor to achieve the optimum tractive performance under a given operating condition, the thrust (or driving torque) distribution between the front and rear axles should be such that the slips of the front and rear tyres are equal. For four-wheel-drive tractors with rigidly coupled front and rear drive axles, this can be achieved if the theoretical speed (the product of the angular speed and the free-rolling radius of the tyre) of the front and that of the rear wheels are equal or the theoretical speed ratio is equal to 1. Field test data confirm the theoretical findings that, when the theoretical speed ratio is equal to 1, the efficiency of slip and tractive efficiency reach their respective peaks, the fuel consumption per unit drawbar power reaches a minimum, and the overall tractive performance is at an optimum.

scholarly journals Outlier Detection at the Parcel-Level in Wheat and Rapeseed Crops Using Multispectral and SAR Time Series

2021 ◽  
Vol 13 (5) ◽  
pp. 956
Author(s):  
Florian Mouret ◽  
Mohanad Albughdadi ◽  
Sylvie Duthoit ◽  
Denis Kouamé ◽  
Guillaume Rieu ◽  
...  
Keyword(s):  
Outlier Detection ◽  
Experimental Validation ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Multispectral Images ◽  
Vegetation Indexes ◽  
Crop Development ◽  
Different Types ◽  
Selection Of ◽  
Sentinel 2

This paper studies the detection of anomalous crop development at the parcel-level based on an unsupervised outlier detection technique. The experimental validation is conducted on rapeseed and wheat parcels located in Beauce (France). The proposed methodology consists of four sequential steps: (1) preprocessing of synthetic aperture radar (SAR) and multispectral images acquired using Sentinel-1 and Sentinel-2 satellites, (2) extraction of SAR and multispectral pixel-level features, (3) computation of parcel-level features using zonal statistics and (4) outlier detection. The different types of anomalies that can affect the studied crops are analyzed and described. The different factors that can influence the outlier detection results are investigated with a particular attention devoted to the synergy between Sentinel-1 and Sentinel-2 data. Overall, the best performance is obtained when using jointly a selection of Sentinel-1 and Sentinel-2 features with the isolation forest algorithm. The selected features are co-polarized (VV) and cross-polarized (VH) backscattering coefficients for Sentinel-1 and five Vegetation Indexes for Sentinel-2 (among us, the Normalized Difference Vegetation Index and two variants of the Normalized Difference Water). When using these features with an outlier ratio of 10%, the percentage of detected true positives (i.e., crop anomalies) is equal to 94.1% for rapeseed parcels and 95.5% for wheat parcels.

scholarly journals Selection of Optimal Magnets for Traction Motors to Prevent Demagnetization

Machines ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 124
Author(s):  
Dantam Rao ◽  
Madhan Bagianathan
Keyword(s):  
Flux Density ◽  
Electric Vehicles ◽  
Parallel Line ◽  
Low Grade ◽  
Lower Grade ◽  
Worst Case ◽  
Traction Motors ◽  
Knee Point ◽  
Point Of Intersection ◽  
Selection Of

Currently, permanent-magnet-type traction motors drive most electric vehicles. However, the potential demagnetization of magnets in these motors limits the performance of an electric vehicle. It is well known that during severe duty, the magnets are demagnetized if they operate beyond a ‘knee point’ in the B(H) curve. We show herein that the classic knee point definition can degrade a magnet by up to 4 grades. To prevent consequent excessive loss in performance, this paper defines the knee point k as the point of intersection of the B(H) curve and a parallel line that limits the reduction in its residual flux density to 1%. We show that operating above such a knee point will not be demagnetizing the magnets. It will also prevent a magnet from degenerating to a lower grade. The flux density at such a knee point, termed demag flux density, characterizes the onset of demagnetization. It rightly reflects the value of a magnet, so can be used as a basis to price the magnets. Including such knee points in the purchase specifications also helps avoid the penalty of getting the performance of a low-grade magnet out of a high-grade magnet. It also facilitates an accurate demagnetization analysis of traction motors in the worst-case conditions.

Factors contributing to the amount of vehicular damage resulting from collisions between four-wheel drive vehicles and passenger cars

2001 ◽  
Vol 33 (5) ◽  
pp. 673-678 ◽  
Author(s):  
Robert W. Broyles ◽  
S.Ross Clarke ◽  
Lutchmie Narine ◽  
Daryl R. Baker
Keyword(s):  
Passenger Cars ◽  
Wheel Drive ◽  
Four Wheel Drive
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