Multibody Dynamic Methods for Vehicle Powertrain Analysis

The study detailed in this paper focuses on simulating vehicle powertrains using a recursive formulation of the rigid body equations of motion. The formulation is based on a minimal set of joint-relative coordinates to spatially represent the bodies of the powertrain system. The engine, torque converter, and transmission components are modeled as force elements, contained within rigid body casings. The formulations of two important joint types; the constant-velocity joint and tripod joint, are developed. Equations describing both the internal motions of the powertrain components and the rigid body elements are then combined and solved simultaneously. The vehicle model is also simulated using a similar, compatible multibody formulation. Connections between the powertrain and vehicle systems are made using either rigid, kinematic constraints, or zero-free-length spring-damper elements, decoupling the solution of the powertrain system from that of the vehicle. Results of the study show the capability of simulating a vehicle, its powertrain, and the interaction of the powertrain with the vehicle’s suspension and steering system linkages. An example system, highlighting the capabilities of the formulation, analyzes the effects of torque-steer on a front-wheel-drive vehicle.