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The Study Of Control For Robots With Underactuated Joint

Posted on:2003-07-18Degree:DoctorType:Dissertation
Country:ChinaCandidate:Q D ZhuFull Text:PDF
GTID:1118360092966278Subject:Control theory and control engineering
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Underactuated manimulator is a kind of manipulator with one or more joint is underactuated which can be called passive joint or free joint. The major character is that the dimension of input space is less than dimension of output space.We can see that the constraint of the system is un-integrable.It is called nonholonomic constraint.All of these feature make the control prolem has a number of additional difficulties.But there are many merit of this kind of manipulator,for example,underactuated manipulator maybe useful in particular instances to reduce weight,cost or energy consumption,while still maintaining an adequate degree of dexterity.So It is benefit to research the method of control problem,and it becomes one of the major topics of the field of robotics recently.The problem of position control is studied in this paper,and the results of my work are as follow:In first the dynamic model of underactuated manipulator is established,the non-holonomic characters of the constraint is analysed,and then the judgement method that if constraint is integrable is gived. So it is proved that the constraint of the manipulator in the paper is un-integrable,and the dynamic system is nonholonomic.Then the behavior of the free joint when we bring the periodic perturbation through controlling the actuated joint is analysed,We can find in the result that the behavior of the free joint in the phase plane follows an ordered closed trajectory with the center equilibrium point +2 in the case where the amplitude of the input is small,We can define a weakening factor to make the position of the free joint reach the center equilibrium point +2 .Based on the result above,the open loop control strategy is bringed forward in the paper. We use the function approximation property of neural network to obtain the function through studying using neural network method.And then realize the position control.We have simplified the model through obtaining the average system of theunderactuated robot using averaging method which is efficient to deal with nonlinear system. The simulation results show that the real system and the average system have the same trajectory in the phase plane under the disturbance of periodic input of the actuated joint of the robot.Finally,the closed loop control strategy through nonlinear states feedback is designed by a Lyapunov function for the averaged system and realize the position control of the non-holonomic robot.The simulation results show that the open-loop control method based on neural network and the feedback control method of the position are effective.
Keywords/Search Tags:robot, underactuated joint, nonholonomic constrain, neural network, averaging method, Lyapunov function
PDF Full Text Request
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