Two-axle vehicles without trailer Low speed or kinematic steering is, as already stated, defined as the motion of a wheeled vehicle determined by pure rolling1 of the wheels. The velocities of the centres of all the wheels lie in their midplane, that is the sideslip angles αi are vanishingly small. In these conditions, the wheels cannot exert any cornering force to balance the centrifugal force due to the curvature of the path. Kinematic steering is possible only if the velocity is vanishingly small. Kinematic steering of two-axle vehicles without trailer was dealt with in detail in Chapter 4 (Section ) | 25 HANDLING PERFORMANCE LOW SPEED OR KINEMATIC STEERING Two-axle vehicles without trailer Low speed or kinematic steering is as already stated defined as the motion of a wheeled vehicle determined by pure rolling1 of the wheels. The velocities of the centres of all the wheels lie in their midplane that is the sideslip angles ai are vanishingly small. In these conditions the wheels cannot exert any cornering force to balance the centrifugal force due to the curvature of the path. Kinematic steering is possible only if the velocity is vanishingly small. Kinematic steering of two-axle vehicles without trailer was dealt with in detail in Chapter 4 Section . Here only the value of the path curvature gain needs be recalled 11 RS 1 5. Remark The path curvature gain is a linearized value holding only if the radius of curvature of the path R is much larger than the wheelbase. It is independent of the steering angle and of the curvature of the path. 1The term pure rolling is often used to indicate rolling without slip. Free rolling as opposed to tractive rolling is used to indicate rolling without exerting tangential forces . Johnson Contact Mechanics Cambridge University Press Cambridge 1985 . Here the two terms are considered as equivalent because a tire must operate in slip longitudinal or side slip conditions to produce a tangential force. G. Genta L. Morello The Automotive Chassis Volume 2 System Design 247 Mechanical Engineering Series Springer Science Business Media . 2009 248 25. HANDLING PERFORMANCE Another important transfer function of the vehicle is ratio 3 6 usually referred to as sideslip angle gain. The sideslip angle of the vehicle referred to the centre of mass may be expressed as a function of the radius of the path R as 3 arctan - VR2 b2 J By linearizing Eq. and introducing the expression linking R to 6 it follows 3_ b z2531 6 l As seen in Chapter 6 the optimal condition for kinematic steering of a 4 wheel .
