Mauro Tognazzo’s research while affiliated with University of Padua and other places

The passive response of the rider's body to bicycle oscillations is experimentally studied by means of laboratory tests. Lumped element models of the rider's body are developed and the relevant stiffness and damping parameters are identified from experimental results. The biomechanical model of the rider is coupled with the benchmark model of the bicycle and open-loop stability analysis is carried out. Results show that the stiffness and damping parameters of the waist do not strongly affect bicycle stability. Uncontrolled arm stiffness has a very detrimental effect on stability and destroys the self-stabilization mechanism. Arm damping has a more complex effect and reduces the self-stability region.

In two-wheeled vehicles the mass of the rider is a significant part of the total mass of the system and the rider influences the dynamic behavior both by means of the voluntary control actions and by means of the passive response of his body to the oscillations of the vehicle. The passive response of the rider’s body has a particular influence on roll motion, which is typical of two-wheeled vehicles. Roll oscillations generate inertia forces on the rider’s body, which moves with respect to the vehicle. Forces and torques generated by the rider on the handlebars, saddle and foot rests are different from the ones that would be generated if the body was rigidly fixed to the vehicle. Therefore, advanced simulation of two wheeled vehicles requires passive biomechanical models of the rider. This paper proposes a novel approach for the study of the passive response of the rider’s body that is based on measurements in the laboratory of the interaction forces between the rider and the vehicle. A special motorcycle mock-up is developed, it is driven by a hydraulic shaker that generates roll excitation with variable frequency. A system of load cells measures the lateral force and torque between the rider and the motorcycle mock-up. The study is carried out in the frequency domain, the passive response of rider’s body is represented by means of three frequency response functions (FRFs): lateral force FRF and torque FRF are the ratios between the lateral force/torque and the roll input; motion FRF is the ratio between the roll motion of the rider’s trunk and the roll input. The biomechanical models of the rider’s body that are developed in this work are able to simulate its response both in terms of interaction forces and motion. These models are composed by some rigid bodies with lumped stiffness and damping parameters in the articulations and in this way they represent a good compromise between accuracy and complexity. The biomechanical parameters of the models are identified by means of a genetic algorithm that aims to minimize a penalty function based on the difference between the three FRFs predicted by the model and the measured FRFs. Results show that a 5 degree of freedom model of the rider is able to represent the measured behavior both in terms of interaction forces and trunk motion.

This paper deals with a research aimed to identify the biomechanical properties of the rider’s body from laboratory tests. Special test equipment has been developed; it is a motorcycle mock up driven by a hydraulic servo-actuator that generates oscillations in the range 0.5–10 Hz. When the rider rides the motorcycle mock up, a system of sensors measures the input motion and the response of the rider’s body. The response of the rider’s body is represented in the frequency domain by means of frequency response functions: the motion frequency response function describes the lean motion of the rider’s trunk, the torque frequency response function describes the torque applied by the rider on the handlebars. The measured frequency response functions are used for identifying the parameters of lumped mass biomechanical models, which are suited to integration with the multi-body model of the motorcycle. Many experimental results are presented and discussed. Various biomechanical models are evaluated in terms of capability of reproducing the measured frequency response function. A good fitting of the motion frequency response function is achieved by means of a three-degrees-of-freedom model of the rider’s trunk, whereas a good fitting of the torque frequency response function is achieved by means of a five-degrees-of-freedom model of trunk and arms.

Advanced simulation of the stability and handling properties of bicycles requires detailed road–tyre contact models. In order to develop these models, in this study, four bicycle tyres are tested by means of a rotating disc machine with the aim of measuring the components of tyre forces and torques that influence the safety and handling of bicycles. The effect of inflation pressure and tyre load is analysed. The measured properties of bicycle tyres are compared with those of motorcycle tyres.

In bicycles and motorcycles the mass of the rider is a relevant share of the total mass and the passive response of the rider’s body to vibrations influences the dynamics and stability of the whole system. Therefore advanced models of two-wheeled vehicles have to include a passive biomechanical model of the rider. This paper focuses on the development of biomechanical models able to simulate the response of the rider to yaw and steer oscillations and on the identification of the rider’s body mechanical properties. Rider models composed by some rigid bodies with lumped stiffness and damping elements in the articulations are developed. The inertial properties of the rider’s model are calculated from anthropometric data. The stiffness and damping properties are obtained from laboratory tests in which the rider rides a motorcycle mock-up driven by a hydraulic shaker generating yaw oscillations. The responses of the districts of the human body are measured by means of rate gyros and the frequency response functions (FRFs) between the measured angular velocity and the enforced angular velocity are calculated. The tests are carried out both with the hands on the handle-bar of the motorcycle mock-up and with the raised hands. Biomechanical parameters are identified by means of best fitting techniques. Experimental results relative to 5 riders are presented and the identified biomechanical parameters are discussed. The proposed biomechanical models make it possible to calculate the rider’s response to steer oscillations as well, some results are presented.

Motorcycle dynamics is characterised by the presence of modes of vibration that may become unstable and lead to dangerous conditions. In particular, the weave mode shows large yaw and roll oscillations of the rear frame and out of phase oscillations of the front frame about the steer axis. The presence of the rider influences the modes of vibration, since the mass, stiffness and damping of limbs modify the dynamic properties of the system; moreover, at low frequency the rider can control oscillations. There are few experimental results dealing with the response of the rider in the presence of large oscillations of the motorcycle. This lack is due to the difficulty of carrying out measurements on the road and of reproducing the phenomena in the laboratory. This paper deals with a research programme aimed at measuring the oscillations of the rider's body on a running motorcycle in the presence of weave. First, testing equipment is presented. It includes a special measurement device that is able to measure the relative motion between the rider and the motorcycle. Then the road tests carried out at increasing speeds (from 160 to 210 km/h) are described and discussed. Best-fitting methods are used for identifying the main features of measured vibrations in terms of natural frequencies, damping ratios and modal shapes. The last section deals with the comparison between measured and simulated response of the motorcycle–rider system in weave conditions; good agreement was found.