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The influence of inflation pressure on cross-country performance
Journal of Terramechanics, 1974, Vol. 11, Nos. 3 & 4, pp. 5 to 10. Pergamon Press Printed in Great Britain.
SUMMARIES The Influence of Inflation Pressure on Cross-Country Performance by T. F. CZAgO. This paper presents the most important results of the mobility testing conducted with a 6 × 6, 2'5-ton, X157 truck equipped with central tire inflation/deflation system and comparative evaluation against an M35A2 current production military truck. A short historical review of the central tire inflation system development and the main details of the system are presented. Conclusions are drawn as to the usefulness and applicability of the system. Dynamic Analysis of a Four-Wheel Off-the-Road Vehicle by R. STAPLETON. Dynamic analysis of a four-wheel off-the-road vehicle has been completed. The work was performed to predict tire and suspension loads caused by tire impact with lunar surface obstacles. This paper presents the significant features of the project. A unicycle model, a 7 degree of freedom small-angle model, and a 14 degree of freedom finite-angle model were defined. The theory was verified by comparison of the response of a prototype test vehicle with model predictions. Results show that: (1) A unicycle model with a multiple-spring wheel can be used to define peak tire and suspension loads for a four-wheel vehicle. (2) A single-spring wheel which runs over the actual ground is not adequate. (3) Soil characteristics significantly affect vehicle response and loads. (4) Wheel mass cannot be ignored in the mathematical model. (5) Peak loads are invariant with respect to conceptual changes in the multiple-spring wheel model. On the Control of a Four-Vehicle Train of Surface Effect Vehicles by V. COHEN and D. ROTHSCHILD. This paper describes an investigation of a train of four surface effect vehicles moving over a fiat terrain with prescribed motion of the lead vehicle. The motion is composed of arcs of constant radius of curvature that includes as a special case the straight-line motion. The objective of the investigation was to ascertain the stability and controllability of this type of configuration and to generate easily implementable schemes to control the remaining vehicles such that they return to the nominal trajectory generated by the lead vehicle. Modern control theory was the basis for generating various linear optimal control laws for the linearized system about the nominal trajectories for various allowable feedback measurements and control configured vehicles. The results, briefly, indicate that the minimum number of controls for this four-vehicle train on a curve of finite radius is at least one of either the lateral, longitudinal or moment control on the last vehicle, implying that the second and third vehicles are trailered. This single control is a function of the relative angles and rates between all of the vehicles--this is termed "complete state feedback control". In the special case of lead vehicle straight-line motion (infinite radius of curvature), necessary and sufficient conditions for SEV-train control with complete state feedback are that the last vehicle must have either a lateral or moment controller and at least one other lateral or moment controller must be present on either the second or third vehicle. Thus, there is, at most, only one trailered vehicle in this mode of operation. The results of experimenting with various combinations of controllers and their effects on the dynamic behavior of the vehicle are presented. These include the time history of the relative angles between the vehicles, their I0 per cent settling times, the peak angular and angular rate deviation from the nominal along with the peak control power requirement. Examination of these results indicates that when more than one controller is employed, both smaller peak angular deviations of all the vehicles from the nominal and smaller individual peak magnitude of control force result, as might be expected. Integration of the complete SEV nonlinear equations of motion was carried out for several configurations, using the linear optimal controllers to compare actual closed-loop behaviour with that of the linearized system. Incorporating identical linear feedback gains in both sets of equations with the same initial conditions yielded surprisingly close agreement for a wide range of initial angular offsets, justifying the validity of the linear model approach for many situations. Recent Developments in Soil Yield Criteria and Numerical Applications by T. J. CHUNG and J. K. LEE. A new definition of loading and unloading along the yield surface of Roscoe and Burland is introduced. A strain-hardening parameter is identified in the plastic potential function deduced from 5
SUMMARIES The Influence of Inflation Pressure on Cross-Country Performance by T. F. CZAgO. This paper presents the most important results of the mobility testing conducted with a 6 × 6, 2'5-ton, X157 truck equipped with central tire inflation/deflation system and comparative evaluation against an M35A2 current production military truck. A short historical review of the central tire inflation system development and the main details of the system are presented. Conclusions are drawn as to the usefulness and applicability of the system. Dynamic Analysis of a Four-Wheel Off-the-Road Vehicle by R. STAPLETON. Dynamic analysis of a four-wheel off-the-road vehicle has been completed. The work was performed to predict tire and suspension loads caused by tire impact with lunar surface obstacles. This paper presents the significant features of the project. A unicycle model, a 7 degree of freedom small-angle model, and a 14 degree of freedom finite-angle model were defined. The theory was verified by comparison of the response of a prototype test vehicle with model predictions. Results show that: (1) A unicycle model with a multiple-spring wheel can be used to define peak tire and suspension loads for a four-wheel vehicle. (2) A single-spring wheel which runs over the actual ground is not adequate. (3) Soil characteristics significantly affect vehicle response and loads. (4) Wheel mass cannot be ignored in the mathematical model. (5) Peak loads are invariant with respect to conceptual changes in the multiple-spring wheel model. On the Control of a Four-Vehicle Train of Surface Effect Vehicles by V. COHEN and D. ROTHSCHILD. This paper describes an investigation of a train of four surface effect vehicles moving over a fiat terrain with prescribed motion of the lead vehicle. The motion is composed of arcs of constant radius of curvature that includes as a special case the straight-line motion. The objective of the investigation was to ascertain the stability and controllability of this type of configuration and to generate easily implementable schemes to control the remaining vehicles such that they return to the nominal trajectory generated by the lead vehicle. Modern control theory was the basis for generating various linear optimal control laws for the linearized system about the nominal trajectories for various allowable feedback measurements and control configured vehicles. The results, briefly, indicate that the minimum number of controls for this four-vehicle train on a curve of finite radius is at least one of either the lateral, longitudinal or moment control on the last vehicle, implying that the second and third vehicles are trailered. This single control is a function of the relative angles and rates between all of the vehicles--this is termed "complete state feedback control". In the special case of lead vehicle straight-line motion (infinite radius of curvature), necessary and sufficient conditions for SEV-train control with complete state feedback are that the last vehicle must have either a lateral or moment controller and at least one other lateral or moment controller must be present on either the second or third vehicle. Thus, there is, at most, only one trailered vehicle in this mode of operation. The results of experimenting with various combinations of controllers and their effects on the dynamic behavior of the vehicle are presented. These include the time history of the relative angles between the vehicles, their I0 per cent settling times, the peak angular and angular rate deviation from the nominal along with the peak control power requirement. Examination of these results indicates that when more than one controller is employed, both smaller peak angular deviations of all the vehicles from the nominal and smaller individual peak magnitude of control force result, as might be expected. Integration of the complete SEV nonlinear equations of motion was carried out for several configurations, using the linear optimal controllers to compare actual closed-loop behaviour with that of the linearized system. Incorporating identical linear feedback gains in both sets of equations with the same initial conditions yielded surprisingly close agreement for a wide range of initial angular offsets, justifying the validity of the linear model approach for many situations. Recent Developments in Soil Yield Criteria and Numerical Applications by T. J. CHUNG and J. K. LEE. A new definition of loading and unloading along the yield surface of Roscoe and Burland is introduced. A strain-hardening parameter is identified in the plastic potential function deduced from 5