Effect of Flexible Spine Motion on Energy Efficiency in Quadruped Running

Energy efficiency is important in the performance of quadruped robots and mammals. Flexible spine motion generally exists in quadruped mammals. This paper mainly explores the effect of flexible spinal motion on energy efficiency. Firstly, a planar simplified model of the quadruped robot with flexible spine motion is introduced and two simulation experiments are carried out. The results of simulation experiments demonstrate that both spine motion and spinal flexibility can indeed increase energy efficiency, and the curve of energy efficiency change along with spinal stiffness is acquired. So, in order to obtain higher energy efficiency, quadruped robots should have flexible spine motion. In a certain speed, there is an optimal spinal stiffness which can make energy efficiency to be the best. Secondly, a planar quadruped robot with flexible spine motion is designed and the conclusions drawn in the two simulation experiments are verified. Lastly, the third simulation experiment is carried out to explore the relationship between the optimal spinal stiffness, speed and total mass. The optimal spinal stiffness increases with both speed and total mass, which has important guiding significance for adjusting the spinal stiffness of quadruped robots to make them reach the best energy efficiency.

Study on the musculoskeletal body for quadruped robots with spinning gait

The walking creatures' athletic ability is related to their body' s musculoskeletal system.A kind of musculoskeletal body for quadruped robots is developed,which will be used to assist the leg mechanism to achieve spinning gait in order to improve the robot mobility in unstructured environment.A bionic-flexible-spine model driven by pneumatic artificial muscles(PAMs) is proposed.Because the body has the flexible property,the robot can achieve spinning gait quickly,which is similar to walking creatures by coordinated movement between body bending and legs side-swing.The kinematics of the bending of the musculoskeletal body and side-swing of leg mechanism of quadruped robot for spinning gait are studied.According to the stability analysis of spinning gait,the relationship between body bending angle and leg swing angle can be determined.The PID controller is designed to conduct the bending experiment,and the bending characteristic of the musculoskeletal body is studied.Experimental results show that the biggest bending angle of the musculoskeletal body can reach 30°.

A novel classification method for mild adolescent idiopathic scoliosis using 3D ultrasound imaging

Mild adolescent idiopathic scoliosis(AIS),with Cobb<20°,was hypothesized as the right stage to intervene to prevent progression.AIS curve can be categorized into either structural or non-structural depending on the spine morphology(flexibility).Using X-ray to characterize AIS curves remains the clinical gold standard whilecompromising the risks of radiation exposure.In previous works,3D ultrasound imaging had proved the reli-ability of the coronal spinal curvature measurement This research aimed at developing a mild AIs clasificationscheme through examining spine flexibility using 3D ultrasound imaging.For the preliminary study,90 mild AIS subjects(21 M and 69 F;Age:14.5±1.7 years old;Cobb:18.2±6.4°)underwent both 3D ultrasound and X-ray scanning on the same day.For each case,a clinician measured Cobbs and denoted major curve as ground truth.Bending Asymmetry Index(BAl)was developed to indicate the presence of a possible structural curve.The curve classification was coded to a modfied Lenke classification for mild cases(m-Lenke).The results of 3D ultrasound classification were evaluated with the X-ray.It was shown that 70.1%of the subjects had identical curve clssification results and 72.0%had the correct major curve detection.Lumbar-dominated curves had distinctive performance(p=0.91,r=0.91)against others.The study demonstrated the possibility of a 3D ultrasound-based method for mild AIS curve classification.Thediscrepancies could be partially explained by the limitations of the ultrasound scanning in proximal thoracicreg ion.Subsequent studies will validate the proposed method with a larger cohort.