Motion Control Reasearch Of A Hexadpod Robot Under Complex Environment

Robot technology has been developing all the time,and legged robot is a hotspot of modern robot research field.Compared with wheeled robots and robotic crawler,legged robots have flexible movements,and they can make use of bionic knowledge to simulate the way multi-legged insects and reptiles moves in order to design the appropriate gaits.Besides,in the desert,grassland,pebble road or other complex unstructured environment,legged robots have disperse supporting points on the plane,which makes they can always find footholds in rugged road,hold steady progress,keep moving with better environment adaptability.For this reason,we hope that we can design a hexapod robot and do some research on this robot,which combines with mechanical,electrical and motion control technology,under the principle of bionics.This paper starts from the mechanical structure,motion structure,control system and power supply system,and then introduced the design principle and basis,and each module of the equipment in detail.The body of the robot is constructed as a frame type for the reduction of weight.The feet of the robot are designed with brushless DC motors and corresponding gearbox.EtherCAT protocol and corresponding drivers are selected due to it's characteristic of real-time,high accuracy and the application background.The motor control system contains double motor encoders,which can directly get the rotating angle of the foot precisely.At last,software kit based on TCP/IP is developed to send control command to the robot and get the state of the robot and information from the sensors located in the robot.This paper raises tripod gait,tetrapod gait and wave gait for the hexapod robot through bionic research of the insects,and implements the gaits based on proportional control and central pattern generator(CPG).Meanwhile,this paper introduces the oscillator model of CPG,and analyze the stability of the oscillator.Simulations are performed to inspect the influence of parameters of the oscillator.First-order low pass filter are introduced to generate the required phase lag,which is necessary to different gaits.In order to inspect the stability of the robot when it runs,force-angle stability measure criterion is raised to calculate the stability margin of the robot when running with different gaits.Experiments are performed to analyze the change of stability during a cycle of the gait,then compare the motion performance and stability of different gaits.Adaptability to different environments is also very important for legged robots because robots should have autonomous ability like human.So the hexapod robot should have the ability to identify different terrain and resort to different gaits,which have better performance on specified environment.For this reason,probability neural network(PNN)and naive Bayes is introduced.Data information from the IMU sensor is gathered and imported into the PNN,and then classification and identification is performed.Experiments are performed to validate the theory and improve the adaptability to environment of the robot.Conclusion of the research and future works are mentioned in the last paragraph.Reliable mechanical structure,more gaits and better algorithm are required in future research.