First Step to Human-Steering System Modelling and Control-Stretch Reflex Characteristic of Driver's Upper Limb Muscles

Stretch reflex is the basis of human activities. In this study, the moment of inertia, damping and stiffness of the human-machine system based on the least-squares method are used to characterize quantitatively the total stretch reflex intensity of the driver's upper limb. In order to study the influence of vehicle on driver in the human-machine co-drive system and the muscle mechanical characteristics during the driving operation, 12 drivers were invited to take part in the experiments and were divided into three groups according to their body fate rate. Through the step signal experiments under the same exciting torque, the equivalent static stiffness obtained from the steering angle is used to characterize the static stretch reflex intensity. And the stiffness ratio is proposed to characterize the dynamic stretch reflex intensity of the driver. Finally, the correlation between mechanical parameters and EMG (Electromyography) indices, steering efficiency and co-contraction, is analyzed. It was found that an increase in exciting torque or muscle tension will result in greater co-contraction and lower steering efficiency of the driver. And an increase of muscle tension will result in larger moment of inertia, damping and stiffness of the human-steering system. There is a significant positive correlation between co-contraction and the mechanical parameters, and a less significant negative correlation between steering efficiency and the mechanical parameters. This research will make contribution to human-steering modelling and further to the control strategy of the human-machine co-drive system.