ABSTRACT
A foot trajectory control method is proposed for biomimetic robot.Compared with traditional methods,the method uses a single CPG neuron to directly apply the foot trajectory generated by the oscillator to the hexapod robot.The joint angles is solved reversely for realizing the rhythmic foot swing,thereby achieving lateral walking.The step distance and step amplitude in foot trajectory,and the forward and backward swing trajectories during the swing phase can be adjusted by setting the load factor,period,amplitude and other parameters in the CPG oscillator.The feasibility of applying the improved Hopf model to foot trajectory is verified through the joint simulation using Matlab and Coppeliasim.Compared with traditional methods,the improved model has high flexibility in parameter adjustment and performs well in concurrency processing.
ABSTRACT
Epimedin B(EB)is one of the main flavonoid ingredients present in Epimedium brevicornum Maxim.,a traditional herb widely used in China.Our previous study showed that EB was a stronger inducer of melanogenesis and an activator of tyrosinase(TYR).However,the role of EB in melanogenesis and the mechanism underlying the regulation remain unclear.Herein,as an extension to our previous investi-gation,we provide comprehensive evidence of EB-induced pigmentation in vivo and in vitro and eluci-date the melanogenesis mechanism by assessing its effects on the TYR family of proteins(TYRs)in terms of expression,activity,and stability.The results showed that EB increased TYRs expression through microphthalmia-associated transcription factor-mediated p-Akt(referred to as protein kinase B(PKB))/glycogen synthase kinase 3β(GSK3β)/β-catenin,p-p70 S6 kinase cascades,and protein 38(p38)/mitogen-activated protein(MAP)kinase(MAPK)and extracellular regulated protein kinases(ERK)/MAPK pathways,after which EB increased the number of melanosomes and promoted their maturation for melanogenesis in melanoma cells and human primary melanocytes/skin tissues.Furthermore,EB exerted repigmentation by stimulating TYR activity in hydroquinone-and N-phenylthiourea-induced TYR inhibitive models,including melanoma cells,zebrafish,and mice.Finally,EB ameliorated monobenzone-induced depigmentation in vitro and in vivo through the enhancement of TYRs stability by inhibiting TYR misfolding,TYR-related protein 1 formation,and retention in the endoplasmic reticulum and then by downregulating the ubiquitination and proteolysis processes.These data conclude that EB can target TYRs and alter their expression,activity,and stability,thus stimulating their pigmentation function,which might provide a novel rational strategy for hypopigmentation treatment in the pharmaceutical and cosmetic industries.
ABSTRACT
Biological central pattern generator(CPG)is of great research significance to the gait control for hexapod robot.Therefore,a Kimura neural oscillator based CPG gait control strategy for hexapod robot is proposed.The mechanical structure of hexapod robot is designed with the spider as the bionic object,and its kinematics is solved.An oscillator model is established based on Kimura neural oscillator,and its parameters are adjusted.The CPG network model is designed according to the phase relation of the 6 legs of the robot.Gait experiments are conducted with computer simulation tools and prototypes.The results demonstrate that the output signal amplitude and phase difference of the CPG network model generated based on Kimura neural oscillator are stable,meeting the gait control requirements of hexapod robot.The study provides a feasible gait control strategy for hexapod robot.