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This paper discusses the evolution of skid steer systems, and takes a new look at the advantages and implications of designing future ground combat vehicles with all non-steerable wheels. The traditional “skid steer” designation of such vehicles is dropped in favor of the more descriptive phrase “differential torque steer” vehicle. The possible advantages of such systems for combat vehicle application are presented along with a synopsis of various past modeling, simulation, and vehicle hardware efforts to evaluate skid steer systems. A comprehensive vehicle modeling effort for a differential torque steer system is then presented. Two independent implementations of the model are presented along with model verification and validation results. Finally the model is used to evaluate potential turning performance for a 4×4 vehicle with differential torque steer.

The U.S. Army initiated program to assess the performance potential of a semiactive advanced suspension system for its combat vehicles is addressed. This paper is a continuation of SAE paper 970386, “Semiactive Suspension: A Mobility Case Study”, Saxon, N.L. and Meldrum, W.R. Jr. This year's paper addresses actual field testing of the semiactive hydropneumatic suspension versus a standard torsion bar passive suspension on two similarly weighted Bradley Fighting Vehicles. The hardware discussed will include semiactive external in-arm hydropneumatic suspension, computer controller, and dynamic track tensioner. The relative mobility of the two systems, passive and semiactive, is evaluated through various field tests such as ride, shock, slalom, and traverse testing.

The U.S. Army has initiated a program to assess the performance potential of a semiactive advanced suspension system for its combat vehicles. The program utilizes the Bradley Fighting Vehicle as a test bed for a semiactive external in-arm hydropneumatic suspension. The system hardware includes the suspension and associated plumbing, computer controller, and dynamic track tensioner. This paper describes the comparable benefits of the semiactive suspension over the passive suspension through both laboratory testing and simulation results. Transmissibility analysis of the laboratory data document far less hull motion in the semiactive case. Simulated vehicle mobility again shows less vehicle motion and superior ride quality using the semiactive suspension.