| Quadruped robots,compared with other types of mobile robots,have more excellent motion ability and environmental adaptability.They have broad application prospects in disaster search and rescue,military operations,scientific research and education,which become a research hotspot in the field of robotics.However,quadruped robots have not been widely used at present,because they are still unable to cope with many tasks.In order to improve their comprehensive performance,a quadruped robot's leg mechanism optimization method was proposed.And bionic locomotion control,based on central pattern generator method,was studied.Besides,a quadruped robot prototype was developed,and the coordinated locomotion control experiment was carried out.According to the load and locomotion,the leg mechanism was optimized.After the analyzing and comparing existing quadruped robots,the five-bar mechanism was determined as the leg mechanism.The kinematics and statics of the leg mechanism were studied.Comprehensively considering the load and locomotion of the leg mechanism,functional relationships between leg link length and the joint torque,joint speed were constructed.In order to improve the performances of the leg mechanism and make the required torque,speed and mass of the leg mechanism as small as possible under the same conditions,genetic algorithm was used to solve this multi-objective optimization problem.Compared with original design,the optimal leg mechanism has reduced the required torque by 14.4%,the required speed by 10.6%,and the mass of the leg mechanism by7.8%.All performance indicators have been significantly improved.Based on animals' locomotion control mechanism of the central pattern generator(CPG),a coordinated locomotion control method was put forward for quadruped robots.The Hopf oscillator was used as a single neuron of the CPG control network and its characteristics were explored.Four Hopf oscillators were phase-coupled to form a CPG control network,which realizes the coordinated control of the quadruped robot's feet.According to quadruped animals' locomotion mechanism,the CPG control network's outputs were adjusted to realize the coordinated control of the joints in the foot.Changing parameters of CPG control network can realize the flexible adjustment of the gait,stride,step height,speed and so on.The output control signals are coordinated,stable,smooth and continuous,which can be widely used.Adams-Simulink co-simulation experiments were carried out and results were analyzed to provide references for the subsequent prototype development.The quadruped robot's virtual prototype was built in Adams,and CPG control network model was built in Simulink.The simulation results show that the quadruped robot has the phenomenon of hind legs dragging ground.Through analysis and research,it's found that the robot has a backward overturning moment when moving forward.Its center of gravity was moved forward by reasonable arrangement so that the phenomenon of hind legs dragging ground was eliminated successfully.The differential turning mechanism of the eight-degree-offreedom quadruped robot was studied.And the radius formula of the differential turning was deduced,which was verified in the simulation experiments.The leg experimental platform and the quadruped robot were developed.Corresponding experiments were carried out.The leg's experimental platform was designed.And key parts' mechanical check was carried out by finite element method.Furthermore,single leg's locomotion experiments were completed.It's proved that the CPG control method can achieve coordinated control of the joints in the feet.The whole machine parts selection and prototype development were completed.The quadruped robot's locomotion experiments were run to verify that the CPG control method can stably realize the coordinated control of all the feet. |
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