Ray W. Murphy

Bio: Ray W. Murphy is an academic researcher from University of Michigan. The author has contributed to research in topics: Tractor & Truck. The author has an hindex of 1, co-authored 2 publications receiving 8 citations.

Directional performance issues in evaluation and design of articulated heavy vehicles

Abstract: This review of the dynamics of heavy road–vehicle systems emphasizes directional performance. The review presents information on the following topics: why are articulated vehicles used; units, hitches, and combination vehicles; multiple axle suspensions and steering systems; important performance issues; models and simulation tools; and controlling directional performance. The concluding section summarizes the material presented and provides ideas regarding the application of vehicle system dynamics concepts in developing controllers for road trains.

Impact of liquid load shift on the braking characteristics of partially filled tank vehicles.

Abstract: SUMMARY Braking characteristics of a tractor-tank-semitrailer vehicle is investigated by incorporating the influence of liquid load shift occurring within the partially filled tank. The tank vehicle model is developed by integrating a steady state model of a partially filled tank and a pitch plane model of the vehicle. The liquid load shift occurring in the pitch plane of the vehicle during a braking maneuver is characterized using the change in the gradient of the free surface of liquid and the corresponding shift in the center of gravity of the fluid bulk. The change in normal load on the various axles of the vehicle during the maneuver is then computed to analyze the braking behavior of the partially filled tank vehicle. The braking characteristics of the tank vehicle are then compared to those of an equivalent rigid cargo vehicle in order to study the impact of liquid load shift. Influence of various vehicle and tank design parameters on the braking behavior and wheel lock-up condition is also investi...

Design concept for an alternative heavy vehicle ABS system

Abstract: This paper investigates the use of slip control on heavy vehicles to reduce stopping distances and compressed air usage in an emergency stop. A hardware-in-the-loop (HiL) rig has been developed to investigate slip control. The hardware includes an air receiver, anti-lock braking system (ABS) or slip-control modulator, brake actuator and brake calliper. The braked wheel and vehicle dynamics are simulated on a micro-processor. A gain-scheduled slip controller using the same pneumatic actuation as used by conventional ABS is developed. The slip control strategy increases the mean fully developed deceleration by 6% and halves the air usage compared to the ABS strategy on the HiL rig. The transient performance of the slip controller is poor due to the sluggish response of the ABS valves, causing a 10% increase in stopping distance. A novel fast-acting brake actuator design is described. Simulations of the new actuator implementing slip control show an improvement of 10% in stopping distance performance and 30%...

Effects of operational and design parameters on the sequence of locking of the wheels of tractor-semitrailers

Abstract: SUMMARY It is known that loss of directional stability during braking occurs in many road accidents involving tractor-semitrailers. To minimize the undesired directional response, the correct order of locking of the wheels is of importance and should receive greater attention. This paper examines the effects of operational and design parameters on the sequence of locking of the wheels of tractor-semitrailers. The way in which the correct locking sequence may be achieved is also discussed in detail.