Stability, control and steering responses of motorcycles

Following on from the author's reviews of the stability and control of moto rcycles in 1978 and 1985, the paper treats the earlier material in tutorial fashion and adds more recent information. Fixed and free control propertie s are compared and it is concluded essential to the operation of a motorcyc le that the steering system is free. Motorcycles typically possess lightly damped oscillatory modes and the properties of these modes are discussed. S mall perturbations from straight line motion and from cornering equilibrium states are treated. Steering control by handlebar torque and by rider uppe r body lean torque are compared. The behaviour of the rider as an extension of the structure of the machine and as a controller is also discussed. The oretical analysis, experimental measurements and general experience are lin ked as far as possible. More recent years have seen a strong movement towards the use of structural ly efficient frames for large motorcycles, in particular, and multibody dyn amics software for handling analysis. Theoretical predictions can be extend ed in ways hardly possible before automated multibody analysis became avail able. The state of the art is illustrated with a description of a contempor ary motorcycle/rider model and some results which are derived from it. Dire ctions for future work are indicated.