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The University of Texas at Austin Center for Electromechanics (UT-CEM) has been developing advanced suspension technology for high-speed off-road applications since 1993. During the course of the program, advanced simulation techniques, verified by hardware demonstrations, were developed and refined. Based on this experience, UT-CEM conducted a detailed simulation-based comparison of passive, semi-active, and full-active suspension systems for an 18,000 kg (20 ton) 8 x 8 vehicle. Performance metrics are proposed to compare crew comfort, crew effectiveness, on-board equipment effectiveness, and power/energy consumption. This paper presents the methodology and rationale for metrics used in the study, simulation results, and data from this trade study. Results indicate significant advantages offered by well-designed active systems compared to both passive and semi-active, in all metrics.

The University of Texas Center for Electromechanics (UT-CEM) has been developing active suspension technology for off-road vehicles since 1993. The UT-CEM approach employs fully controlled electromechanical actuators to control vehicle dynamics and passive springs to efficiently support vehicle static weight. The project described in this paper is one of a succession of projects toward the development of effective active suspension systems, primarily for heavy off-road vehicles. Earlier projects targeted the development of suitable electromechanical actuators. Others contributed to effective control electronics and associated software. Another project integrated a complete system including actuators, power electronics and control system onto a HMMWV and was demonstrated at Yuma Proving Grounds in Arizona.

The University of Texas at Austin Center for Electromechanics (UT-CEM) has conducted a set of simulations and full-scale experiments to determine suitable shock load design requirements for in-hub (wheel) propulsion motors for hybrid and all-electric combat vehicles. The characterization of these design parameters is required due to recent advancements in suspension technology that have made it feasible to greatly increase the tempo of battle. These suspension technologies allow vehicles to traverse off-road terrains with large rms values at greater speeds. As a result, design improvements for survivability of in-hub motors must be considered. Defining the design requirements for the improved survivability of in-hub motors is the driving factor for this research. Both modeling and experimental results demonstrate several realistic scenarios in which wheel hubs experience accelerations greater than 100g, sometimes at very low vehicle speeds.

Lower battery voltage enhances electric vehicle safety. A homopolar traction motor operates at low voltage because of its low internal impedance, and delivers torque independent of speed. A 48 VDC multi-pass, iron core homopolar traction motor was designed, fabricated, and tested in the laboratory. A MOSFET pulse width modulated controller was also designed and tested. The motor weighed 227 kg and used solid copper-graphite brushes. Laboratory testing of the motor verified the current-torque characteristic, but high brush wear prevented full speed and power demonstration. System studies show that a hybrid Ward-Leonard drive using a similar motor could yield significant cost and weight savings and improved fault tolerance over a traditional EV architecture.

The University of Texas at Austin Center for Electromechanics has developed an active suspension system that recovers, stores, and manages energy while actively controlling vehicle suspension activity. Tests described in this paper quantify increases in rolling resistance from flat to rough terrain, and demonstrate that active suspension systems can limit this increase to 50% of that experienced by passive suspension systems.

The use of a fuzzy logic controller for an active suspension system on a wheeled vehicle is investigated. Addressing the opposing goals of ride quality and bump stop avoidance are integrated into one control algorithm. Construction of the fuzzy rules base will be discussed comprehensively along with the membership function setup for both the input and output variables. Numerous quarter-car simulation comparisons will be performed of the fuzzy controller versus the standard skyhook damper controller. The comparisons will include a variety of terrain inputs. Laboratory testing of the fuzzy controller on a single wheel station system is also included.

The University of Texas Center for Electro-mechanics (UT-CEM) has been developing active suspension technology for high-speed off-road applications since 1993. The UT-CEM system uses controlled electromechanical actuators to control vehicle dynamics with passive springs to support vehicle static weight. The program is currently in a full vehicle demonstration phase on a military high mobility multipurpose wheeled vehicle (HMMWV). This paper presents detailed test results for this demonstration vehicle, compared to the conventional passive HMMWV, in a series of tests conducted by the U.S. Army at Yuma Proving Grounds. Extensive data in plotted form are discussed, including accelerometer readings from 6 vehicle mounted accelerometers, corner displacement transducers, and current and power plots for the actuators.

The University of Texas Center for Electromechanics (UT-CEM) has been developing active suspension technology for off-road and on-road vehicles since 1993. The UT-CEM approach employs fully controlled electromechanical (EM) actuators to control vehicle dynamics and passive springs to efficiently support vehicle static weight. The program has completed three phases (full scale proof-of-principle demonstration on a quarter-car test rig; algorithm development on a four-corner test rig; and advanced EM linear actuator development) and is engaged in a full vehicle demonstration phase. Two full vehicle demonstrations are in progress: an off-road demonstration on a high mobility multiwheeled vehicle (HMMWV) and an on-road demonstration on a transit bus. HMMWV test results are indicating significant reductions in vehicle sprung mass accelerations with simultaneous increases in cross-country speed when compared to conventional passive suspension systems.

Through the support of the United States Tank and Automotive Command (TACOM), The University of Texas at Austin Center for Electromechanics (UT-CEM) has developed a prototype electromagnetic (EM) linear actuator suitable for vehicle active suspensions. The prototype actuator built was designed to be used in conjunction with a supplemental air spring. It is capable of producing 8,896 N (2,000 lb) of force with a 12.7 cm (5 in.) stroke and up to 1 m/s (40 in./s) velocity. The actuator was designed as a retrofit for military high mobility multi-wheeled vehicles (HMMWV). The design also focused on capability of being retrofit on a 18.1 kg (20-ton) metropolitan advanced technology transit bus (ATTB).

In March of 1995, the University of Texas at Austin Center for Electromechanics (UT-CEM) began work on developing active suspension control algorithms for four-wheeled, off-road, rough terrain, vehicles. To serve as a test platform to validate simulations, a four corner test-rig, representing a military HMMWV at one third scale, was designed and fabricated. Multiwheel control algorithms were developed, based on single wheel concepts previously described in SAE publications. The four-wheel test-rig performance compared well with single wheel test-rig performance, showing that the active suspension concepts developed by UT-CEM, which do not require advanced terrain knowledge (i.e., no “look-ahead”), are compatible with full vehicle control.

Researchers at The University of Texas Center for Electromechanics recently completed design, fabrication, and preliminary testing of an Electromagnetic Active Suspension System (EMASS). The EMASS program was sponsored by the United States Army Tank Automotive and Armaments Command Center (TACOM) and the Defense Advanced Research Projects Agency (DARPA). A full scale, single wheel mockup of an M1 tank suspension was chosen for evaluating the EMASS concept. The specific goal of the program was to increase suspension performance so that cross-country terrain could be negotiated at speeds up to 17.9 m/s (40 mph) without subjecting vehicle occupants to greater than 0.5 gee rms. This paper is a companion paper to a previous SAE publication [1] that developed suspension theory and control approaches. This paper focuses on hardware implementation, software implementation, and experimental results.

The use of electromechanical actuators for an active suspension on a main battle tank is investigated. A novel approach to the development of the active suspension control algorithms is presented along with simulation results to evaluate the electromechanical design requirements. The optimal electromechanical actuator design is described along with simulated performance results for a one roadwheel station electromechanical active suspension. Follow-up plans for the laboratory testing of a single wheel station system are also included.