On The Position Control Method And Experiment Of The 3R Underactuated Robot

The underactuated robot is a kind of mechanical system which has less input thanthe DOF of system. This means that there are one or more joints without drivers. So ithas the merits of light weight, compact configuration, low energy consumption and soon. The study of underactuated robot is great value for theory and wide application infuture. However, the underactuated robot has the character of second ordernonholonomic constraint; the control method is more difficult than the full-actuacterobot. Nowadays, research on the control technology of underactuated robot has gotconsiderable attentions and it becomes the advanced topics in robotic research.In this study, a 3R horizontal robot with a fully-free passive joint is introduced.Through a numerical simulation and experiment of 3R underactuated robot forposition control, the PTP control of this robot is achieved in operational space.Firstly, the dynamic model in joint space of the underactuated 3R horizontal robotis established with Lagrange equation. The joint friction is considered and the weightof joint is seemed as centralization weight in equantion. Base on the dynamic model,the simulation of 3R underactuated robot is achieved with the combination inhierarchical fuzzy control and genetic algorithm.Secondly, the simulation on the simultaneous start and simultaneous motion withsimple fuzzy control rulers are accomplished, respectively. The endpoint positioncontrol of this underacturated system can be regarded as the motion with folding orunfolding of the passive joint and rotating of active joint. The control torque of theactive joint is determined by the weighted sum of the control parameters, this controlmethod has the virtues of less calculation and easily to adjust the control parameters.Thirdly, the experiment platform of underactuated robot is developed and thisplatform mainly consists of the four links and electrical control system. Theincremental encoder is equipted on each joint to measure the joint position. Theexperiment control interface is exploited which can be used to set up the controlparameters and display the position information real-time. This experiment systemprovides a platform for the futher study on underacutated robot.Finally, the position control corresponding to the two kinds of motion(simultaneous start and simultaneous motion) base on the formermentioned methodare carried out, the results shown that two kinds of motion can achieve the expectedposition control. The feasibility and validity of prosposed method is verified throuththe analysis of the simulation results and experiment results.The proposed methodsand experiment results in this study has the great instruction to the further study of theunderactuated robot.