Research On The Neuromuscular Mechanical Characteristics Of Driver's Upper Limbs Based On The EMG Signals

Steering system is one of the main mediums of human-vehicle tactile interaction.The driver's steering actuator is the nerves and muscles of the upper limbs,and the quantitative study of the muscular mechanical characteristics of the driver's upper limbs is very important for the evaluation of steering comfort,the anthropomorphic driving of intelligent cars,and the research on human-machine sharing control strategy of human-machine co-driving cars,etc.So far,subjective method,which is time-consuming,expensive and easily influenced by individual differences,has been widely used for the evaluation of the state of the driver's muscle strength.In this article,by collecting and analyzing the electromyogram(EMG)signal during the driver's steering operation,two evaluation indices of the muscle strength,steering efficiency and co-contraction,are proposed,and their relationship with steering resistance is discussed,which provides a theoretical basis for studying the neuromuscular mechanical characteristics of the driver's upper limbs from the perspective of the law of muscle force.With the aim to research the influence of driver's upper limb muscle force on the mechanical parameters(inertia,damping and stiffness)of the steering system,14 drivers were selected to take part in the steering experiment with their upper limbs passively holding the steering wheel.By collecting the EMG signals of the driver's upper limb muscles,co-contraction and steering efficiency reflecting the strength of the muscle force were calculated;By collecting the C-EPS motor current,the recursive least-squares method with a forgetting factor was applied to identify the mechanical parameters of the human-machine system.Finally,the correlation between the EMG indices and the driver's upper limb mechanical parameters was analyzed.This experiment will lay a theoretical and experimental foundation to studying the neuromuscular mechanical characteristics of the driver's upper limbs from the perspective of the driver's influence on the parameters and performance of the steering system.Stretch reflex is the physiological basis of human activities.In order to separately study the effects of the static stretch reflex associated with maintaining limb postures and the dynamic stretch reflex associated with resistance to the limb when it is being pulled,12 drivers participated in the experiment and were divided into three groups according to their body type.Firstly,the upper limb parameter identification experiment under the sinusoidal signal was performed on the steering test bench,and then the step signal experiment was performed under the same motor torque.The steering angle measured in the step signal experiment could be used to calculate the ‘equivalent static stiffness' which was used to characterize the static stretch reflex intensity.Calculating the ‘stiffness ratio' using the stiffness obtained from the above two experiments could be used to characterize the driver's dynamic stretch reflex intensity.Finally,the correlation between all mechanical parameters(inertia,damping,stiffness,stiffness ratio,etc.)and EMG indices(steering efficiency and co-contraction)was analyzed,which obtains the functional regulations of the dynamic stretch reflex of the driver's upper limbs.This study focuses on the impact of the neuromuscular mechanical characteristics of the driver's upper limbs on the parameters and performance of the vehicle steering system,and lays a foundation for the control strategy of the human-machine co-driving system.