Research On Compliant Control Of Heavy Duty Hexapod Robot Based On Impedance Control

As the improvement of science technology and people’s needs, it’s a new developing direction to use the heavy duty robot to replace the vehicle in th e complex terrain. Hexapod robots with terrain adaptability and high bearing capacity are the preferred target of this research direction. Compared to the vehicle, the hexapod robot has a high degree of freedom, and the operation is complicated for drivers. There is no relevant research about how to operate the hexapod robot in real time to adapt to the complex terrain. On the other hand, the weight and stiffness of the heavy legged robot is too large to produce deformation, which make the robot can’t be treated as a rigid body, and there is also no relevant research at present. Therefore, this paper focuses on the problem of compliant control of a heavy hexapod robot, which is controlled by drivers in complex terrain.Firstly, according to the characteristics of the hexapod robot, a terrain fitting method based on the discrete foot off points is established. According to the operating habits of the drivers, three degrees of freedom of the body are constrained by the fitted terrain, which simplifies the opera tion of the driver. We can calculate the motion speed and trajectory of the body on the basis of the motion parameters and geometry parameters given by operators, then we can utilize the result to solve the trajectory of the foot. In a word, the robot moti on planning problem is completed in the complex terrain, and the compliant motion can be achieved in a certain degree.Secondly, the paper takes the deformation of the robot as the breakthrough point, and the leg spring-damping model is set up. The paper propose a coordinated constraint force distribution method based on deformation, and analysis the foot force distribution solutions. Actual force of the feet can dynamically track target force on the basis of impedance control. According to the calculation of force of the feet and leg spring model, the deformation of the legs can be calculated and compensated, which can adjust the posture of the body based on the feedforward control. In the light of the difference between the target position and the actual position, the position and attitude of the body can be adjusted by the suspension model.Finally, the virtual prototype model of the heavy hexapod robot is established. The force of the robot is analyzed and a simplified model of the robot is established. Different terrains including flat horizontal surface, rough horizontal surface, complex terrain, flexible ground are established in Adams and simulation experiments are performed respectively in these terrains. The paper compares parameters in two different situations, one of which adds posture control and force control to the model but another don’t.