Steering dynamics of tracked vehicles


Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Graduate School of Natural and Applied Sciences, Graduate School of Natural and Applied Sciences, Turkey

Approval Date: 2016

Student: MEHMET NURİ ÖZDEMİR

Supervisor: YAVUZ SAMİM ÜNLÜSOY

Abstract:

The main objective of this thesis study is the development of a general transient steering model for tracked vehicles which is simple, accurate, and simulation results are in agreement with test results to a satisfactory level. For modeling Matlab/Simulink platform is utilized. The model represents a general tracked vehicle having rear or front sprockets, with variable centre of gravity and wheel positions, and number of wheels. The vehicle hull is modelled as a rigid body having 3 degree of freedom; translation in the longitudinal and lateral directions, and yaw rotation. The terrain is modelled as flat non-deformable terrain. The model involves the calculation of contact forces between the track and the terrain, and calculation of longitudinal and lateral forces acting on the hull. Contact forces between the track elements and the terrain are calculated for each wheel taking the track tension into account. The effects of lateral accelerations during steering, and longitudinal accelerations in traction or braking are included in contact force calculations. To be able to calculate longitudinal and lateral forces, a transient shear model is used. The shear model utilizes determination of slip velocities, slip displacements, the shear stress on the track pad surface under each road wheel, and the resulting shear forces. Shear stress is assumed to be a function of shear displacement. The inputs to the vehicle model are left and right sprocket speeds and the outputs are vehicle position, velocity, and acceleration in the longitudinal, lateral, and yaw directions, and side slip angle. A comprehensive program of road tests has been performed. The results from the model study and the road test program involving various steering scenarios show that the agreement between them is satisfactory both in the steady state and transient steering simulations.