Design and motion analysis of reconfigurable wheel-legged mobile robot

An adaptive wheel-legged shape reconfigurable mobile robot,based on a scissor-like mechanism,is proposed for an obstacle detecting and surmounting robot,moving on complex terrain.The robot can dynamically adjust its own shape,according to the environment,realizing a transformation of wheel shape into leg shape and vice versa.Each wheel-legged mechanism has one degree of freedom,which means that only the relative motion of the inner and outer discs is needed to achieve the transformation of the shape into a wheel or a leg.First,the force analysis of the conversion process of the wheel-legged mechanism is carried out,while the relationship between the driving torque and the friction factor in the non-conversion trigger stage and in the conversion trigger stage is obtained.The results showed that the shape conversion can be better realized by increasing the friction factor of the trigger point.Next,the kinematics analysis of the robot,including climbing the obstacles,stairs and gully,is carried out.The motion of the spokes tip is obtained,in order to derive the folding ratio and the surmountable obstacle height of the wheel-legged mechanism.The parameters of the wheel-legged structure are optimized,to obtain better stability and obstacle climbing ability.Finally,a dynamic simulation model is established by ADAMS,to verify the obstacle climbing performance and gait rationality of the robot,in addition to a prototype experiment.The results showed that the surmountable obstacle height of the robot is about3.05 times the spoke radius.The robot has the stability of a traditional wheel mechanism and the obstacle surmount performance of a leg mechanism,making it more suitable for field reconnaissance and exploration missions.

Design and Analysis of a Multi-Legged Robot with Pitch Adjustive Units

The paper proposes a novel multi-legged robot with pitch adjustive units aiming at obstacle surmounting.With only 6 degrees of freedom,the robot with 16 mechanical legs walks steadily and surmounts the obstacles on the complex terrain.The leg unit with adjustive pitch provides a large workspace and empowers the legs to climb up obstacles in large sizes,which enhances the obstacle surmounting capability.The pitch adjustment in leg unit requires as few independent adjusting actuators as possible.Based on the kinematic analysis of the mechanical leg,the biped and quadruped leg units with adjustive pitch are analyzed and compared.The configuration of the robot is designed to obtain a compact structure and pragmatic performance.The uncertainty of the obstacle size and position in the surmounting process is taken into consideration and the parameters of the adjustments and the feasible strategies for obstacle surmounting are presented.Then the 3D virtual model and the robot prototype are built and the multi-body dynamic simulations and prototype experiments are carried out.The results from the simulations and the experiments show that the robot possesses good obstacle surmounting capabilities.

Performance analysis and test of a maize inter-row self-propelled thermal fogger chassis

In view of the difficulties in weeding and plant protection in the middle and late period of maize planting,this paper proposed a self-propelled thermal fogger chassis.According to the theoretical calculation and agronomic requirements for maize planting,the structure and working principles of the self-propelled thermal fogger chassis were introduced.On this basis,the multi-body dynamics model of chassis structure was established,and the chassis traction,steering and obstacle surmounting performances were also analyzed.Then the rationality and the feasibility of the design were verified through the furrow running test and test equipped with thermal fogger.Test results showed that,the traction performance improves with the decrease of soil deformation index and increase of cohesion,and when track pre-tensioning force was about 1000 N,the machine had a good traction performance;with the decrease of the soil deformation index and the increase of cohesive force,the stability of the single side brake turn of the chassis becomes better;on the contrary,with the increase of the tightness of the crawler,the steering radius turns smaller and the steering stability becomes worse.Under heavy clay,with the pre-tensioning of 1000 N,the machine has better steering stability and smaller turning radius.The obstacle-surmounting simulation result shows that on sandy soil road,the maximum climbing angle for the chassis is 42°,the height of vertical obstacle crossing is 170 mm and the trench width is 440 mm.The study provides a reference for the design of plant protection machinery in the middle and late stages of maize planting.

Acquired resistance to third-generation EGFR-TKIs and emerging next-generation EGFR inhibitors

The discovery that mutations in the EGFR gene are detected in up to 50%of lung adenocarcinoma patients,along with the development of highly efficacious epidermal growth factor receptor(EGFR)tyrosine kinase inhibitors(TKIs),has revolutionized the treatment of this frequently occurring lung malignancy.Indeed,the clinical success of these TKIs constitutes a critical milestone in targeted cancer therapy.Three generations of EGFR-TKIs are currently approved for the treatment of EGFR mutation-positive non-small cell lung cancer(NSCLC).The first-generation TKIs include erlotinib,gefitinib,lapatinib,and icotinib;the second-generation ErbB family blockers include afatinib,neratinib,and dacomitinib;whereas osimertinib,approved by the FDA on 2015,is a third-generation TKI targeting EGFR harboring specific mutations.Compared with the first-and second-generation TKIs,third-generation EGFR inhibitors display a significant advantage in terms of patient survival.For example,the median overall survival in NSCLC patients receiving osimertinib reached 38.6 months.Unfortunately,however,like other targeted therapies,new EGFR mutations,as well as additional drug-resistance mechanisms emerge rapidly after treatment,posing formidable obstacles to cancer therapeutics aimed at surmounting this chemoresistance.In this review,we summarize the molecular mechanisms underlying resistance to third-generation EGFR inhibitors and the ongoing efforts to address and overcome this chemoresistance.We also discuss the current status of fourthgeneration EGFR inhibitors,which are of great value in overcoming resistance to EGFR inhibitors that appear to have greater therapeutic benefits in the clinic.