The Virtual Decomposition And Mode Switching Control Of Nuclear Power Disaster Relief Manipulator

Due to the existence of high temperature,water vapor,smoke and strong electromagnetic interference of special environment,the requirements of the driving system,sensor system and control system of the manipulator are more severe.A case study of manipulator operation in nuclear power disaster relief environment,typical operating conditions include opening door of the main control room,entering the control room to shut down the nuclear reactor,rotating the valve to close the toxic material pipeline based on the protection of the drive system and sensor system.Four steps: arrival,grasping,rotation and release,are needed to be done to achieve the conditions of opening the door or unscrewing the valve.Under the nuclear power disaster environment,the manipulator operation of opening the door or rotating the valve needs to be considered precision,dexterity,maneuverability and compliance at the same time.According to the requirements of national basic research program-Basic Scientific Research of Emergency Rescue Robot in Nuclear Power Plant,the aim of the study is to open the door and rotating the valve with the consideration of the accuracy,dexterity,maneuverability and compliance of the manipulator.Specifically,this paper concerns the mainly resear ches as following:Focusing on the 6 DOF manipulator with the difficulties of traditional methods modeling problems,manipulator is decoupled into independent link and joint based on the the virtual decomposition theory.Meanwhile,the flexibility of the j oint is caused by a short harmonic reducer,so based on traditional spring damping model,an analytical model is further applied to the virtual decomposition of manipulator.So,the dynamic model of 6 DOF manipulator systems with joint flexibility is established.The model provides the basis for the accuracy control and compliance control of the manipulator.In this method,the coupling between joints is realized by means of the virtual energy flow(virtual force).The virtual force does not depend on the torque sensor,and can be obtained by data fusion.Compared with the traditional Lagrange method or Newton Euler method,it has higher calculation precision and less computation.In order to solve the contradiction in the process of accuracy and compliance based on considering the requirements of nuclear power disaster relief environment for sensor system,active mode controller and passive mode controller are designed respectively to realize manipulator position control and force control.According to the theory of model switching control,the design of the corresponding switching factor observer and the corresponding switching algorithm make the process of opening door and rotating valve,joint can respectively work in different modes,and switch on the basis of the actual force in different modes.In the process of reaching and grasping,the manipulator is the active control mode,and the position control is realized.In the process of rotation and release,the manipulator will automatically switch to the passive control mode because of the internal force.In order to verify that the switching control strategy is effective in the process of operation,the M2 SCDyn dynamics simulation platform is built under the Vortex engine,and based on the system simulation platform,the simulation results show that the switching control strategy can solve the contradiction of the operation process the accuracy and compliance.Considering the influence of the nuclear environment on the sensor,in order to solve the problem of joint flexibility,which is used to solve the problem of maneuverability of the manipulator,this paper adds a link-side rotary transformer between the flexible joint reducer output and the connecting rod,then according to motor encoder information and link-side rotary transformer information,position and speed information identification algorithm are designed.At the same time,this paper proposes a joint torque measurement algorithm without force sensor,which makes the use of motor current,motor encoder information,link-side rotary transformer information fitting joint torque identification algorithm.Based on the embedded joint controller,one can achieve the corresponding algorithm.Compared with the traditional measurement method,this method is more accurate for the joint position and velocity feedback,and the torque measurement does not need a torque sensor to meet the requirements of the nuclear power disaster relief environment.According to the need of online or offline identification of un known parameters of geometric constraint object,while the traditional vision sensors at the scene may be invalidation,and special protective lens precision,it is difficult to be used for parameter identification,this paper puts forward a visual guide a nd manipulator attitude information identification method.Through the visual feedback,one can make the basic judgment on the job object,remote the end of arm pointing to several special points on it,and then use these special points to make information fusion to get the operation parameters of the object.On the basis of the system experiment platform RCAMA-1,the experiments are carried out to simulate the task of disaster relief,and the experiments are carried out under the condition of unknown constraints based on the virtual decomposition and mode switching control.The results of the system test show that the compliance control strategy of the manipulator based on virtual decomposition and modal transition has good effects on the control precision and compliance.