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Design, analysis and controlling of an offshore load transfer system Dimuthu Dharshana


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MAS501 Control Theory2-Autumn 2013 Design, analysis and controlling of an offshore load transfer system Dimuthu Dharshana

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Design, analysis and controlling of an offshore load transfer system Dimuthu Dharshana

  1. 1. Design, Analysis and Control of an Offshore Load Transfer System MAS501 Control Theory2- Autumn 2013 University of Agder Grimstad Norway Oreste Niyonsaba Haocheng Su Dimuthu Dharshana Arachchige Bernard Sisara Gunawardana Subodha Tharangi Ireshika Jagath Sri Lal Senanayaka
  2. 2. Presentation Outline  Introduction and methodology  Crane kinematics  Control architecture in Labview  HIL Setup  Control architecture in Step 7  Results  Discussion and Conclusion
  3. 3. Introduction and methodology  Cranes are used in different Engineering activities including offshore operations for transportation of loads and personnel.  Control design needs improvement to meet some of the main criteria such as automatic tool tip tracking among others  Control system is aimed at maintaining the position of the tool tip within one meter by one meter square relative to an inertial frame of measurement is developed  Firstly, the desired tool path is achieved in Labview, then the control architecture is programmed in Siemens Step7 TIA environment integrated with Siemens ET200 PLC.
  4. 4. Introduction and methodology  Control Architecture is plugged with crane boom to achieve the desired movement  A DLL file is created by modeling HMF crane in SimulationX in order to use it in Labview software as shown if the figure below
  5. 5. Introduction and methodology  The desire is to implement the control architecture with two P and PI controllers for controlling the tool tip position
  6. 6. Crane kinematics from matlab  Kinematics plays a significient role to establish the traslational relastionships between global coordinate system and the coordinate system of crane components.  Devided in to Forward kinematics, Inverse kinematics, Forward Jacobian, Inverse Jacobian and Actuator kinematics
  7. 7. Forward Kinematics  Utilized to find the change of tool tip position when the angular positions are given  Necessary to develop DH (Denavit-Hartenberg) table
  8. 8. Inverse Kinematics  Utilized to sketch the angular position(q2,q3) when the tool tip position (x,z)is known.
  9. 9. Forward Jacobian  Utilized to skecth the velocities of the actucators when the angular velocities are known.  Maple was used to find the parameters in the jacobian matrix.
  10. 10. Inverse Jacobian  Angular velociteis when the toll tip velocities are known.  It is obtained by differentiating the inverse kinematics.  This part is also implemented in both matlab and labview.  Inverse kinematics and inverse Jacobian are crucial to convert the reference positions and velocities of the desired tool path into reference angular positions and angular velocities of two actuator joints.
  11. 11. Actuator kinematics Used to derive relationships between angular movement of the actuators and linear movements of the cylinders. Actuator Kinematics 2 Actuator Kinematics 1 L3 L2 Law of Cosine Analytical procedures are difficult
  12. 12. Polynomail Curve Fitting: ‘Polyfit’ Returns coefficients of the polynomial in descending powers. L2 and Q2 Relation L3 and Q3 Relation 140 40 120 20 100 0 80 -20 60 -40 40 -60 20 -80 0 -100 -20 -120 -40 -140 -60 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 -160 1.1 Root mean square error Third order polynomial Fifth order polynomial 1.2 1.3 1.4 1.5 1.6 0.0067 0.0037 1.7 1.8 1.9 2 2.1
  13. 13. Tool path in Labview Operated in two segments The path length (L) between the two locations and angular position of the velocity vector are geometrically found in order to guide the tool tip along the shortest possible path 1. Initial position and target point 2. Reference square path
  14. 14. Tool point along the reference square path Total Length of path s=3.914 m s<L1 % First stretch xDot=v; zDot=0; s<L1+L2 % First corner x=R+L1+R*cos(q-pi/2); z=R+R*sin(q-pi/2); xDot=v*cos(q); zDot=v*sin(q); s<2*L1+L2) % Second stretch s<2*L1+2*L2) % Second corner s<3*L1+2*L2) % Third stretch s<3*L1+3*L2) % Third corner s<4*L1+3*L2) % Fourth stretch s<4*L1+4*L2) % Fourth corner Reference values for tool tip position and velocities are fed to inverse Jacobian and inverse kinematics to configure the joint angular movements .
  15. 15. Implementation of controllers in Labview P_L2 PI_L2 P_L3 PI_L3 Propotional Gain (P) Integral Gain (I) P_L2 & P_L3 50 - PI_L2 & PI_L3 0.05 0.001
  16. 16. Harware-In-Loop;Labview,PLC & Real Time Target TCP/IP configuration Data Communication
  17. 17. Communication between Step7 and Labview
  18. 18. Configuration of the PLC Siemens ET200S PLC
  19. 19. Configuration of the PLC
  20. 20. Tasks of digital switches in PLC Switch Addre Task ss in PLC Manual(Man_Sw) I3.0 Tool tip is moved to any location in the xz plane with respect to the actuator velocities given by analog inputs Point(Point_Sw) I3.2 Tool tip is moved through the shortest path from current location to any given target location by changing the velocity given by analog input 1 Auto(Auto_Sw) I3.1 It is required to enable the point switch before enabling the auto switch. Due to the limitation in actuator lengths, it is not possible to run the given reference path starting from any arbitrary location in the xz plane. Hence, the tool tip is firstly moved to a defined point (2.0, 1.5) which is within the scope of controlling the actuator lengths. Thereafter, the tool tip is moved along the reference tool tip path by enabling auto switch. Velocity of the tool tip can be controlled by changing the analog input 1.
  21. 21. Digital switch configuration Manual Auto Point Output 1 1 1 No operation 1 1 0 No operation 1 0 1 No operation 1 0 0 0 1 1 Manual switch is enabled No operation 0 1 0 Auto switch is enabled 0 0 1 Point switch is enabled 0 0 0 No operation
  22. 22. Digital switch configuration in main controller block with SCL Manual-1 Auto-1 Point-1 Manual-1 Auto-1 Point-0 Manual-1 Auto-0 Point-1 Manual-1 Auto-0 Point-0 Manual-0 Auto-1 Point-1 Manual-0 Auto-1 Point-0 Manual-0 Auto-0 Point-1 Manual-0 Auto-0 Point-0
  23. 23. Implementation of the point switch in Step 7  In order to achieve the task of the point switch, point initializer block and the respective SCL code is developed  The Initial Integrator block is used to calculate the distance ‘ss’, travelled by tool tip along the linear reference path from stating point to target point
  24. 24. Implementation of auto switch in Step 7  ‘path’ function is defined to configure the reference tool tip position and reference velocity.  The reference tool path is implemented in Step 7 in SCL language  An integrator is used to calculate the distance travelled by tool tip along the reference path, ‘s’.
  25. 25. Crane kinematics and PID controllers in Step 7  Inverse kinematics, Inverse jacobian and actuator kinematics are developed in Step seven as FC blocks and the same programs used in labview were implemented in SCL language.  Two P controllers and two PI controllers were implemented with CONT_C block and parameters were tuned accordingly. Controller P_L2 P_L3 PI_L2Dot PI_L3Dot 400 400 0.05 0.05 Tuned values P I 0 0 0.01 0.01
  26. 26. LabView Results: Path  Test was sucessful  Maximum +/- 10 cm deviation form expected path Reference Path Actual Path
  27. 27. LabView Results: Controllers Operation Actuator L2 position and velocity controllers Actuator L3 position and velocity controllers
  28. 28. HiL Test Results: Expected Path
  29. 29. HiL Test Results : Manual and Start Point Initialization Operations  Manual and tip point initialize(shortest path finder) control functions to make the system operation more robust and safe. Manual Mode Operation Start Point Initialization Operations
  30. 30. HiL Test Results: Path  HiL test was very sucessful  Maximum +/-5 cm deviation form expected path( only in two edges). Start Point Initialization Operations Auto mode Actual Path
  31. 31. Real HMF Crane Test Results: Path  Real crane test was very sucessful  Maximum +/- 5 cm error in expected path  Approximate 35 cm offset in x direction. HiL Test Actual Path Real Test Actual Path
  32. 32. Why 35 cm Offset ? There is 34.3 cm offset in x direction of the coordinate systems used in dll file and real crane.
  33. 33. Discussion and Conclusions  Lab view results were observed with +/- 5-10 cm deviation.  Possible resons could be computer programs were not used dedicated hardware to run controllers and DLL model.  Modelling errors in DLL file and our sysem model  With HIL test we used dedicated hardware to run the controllers and realtime tartget(DLL model). Maximum +/-5 cm deviation form expected path( only in two edges) was observed. HiL Test was very sucessful.  Modelling errors in DLL file and our sysem model  With real experiment it was observed Maximum +/- 5 cm error in expected path and 35 cm offset in x direction. Test was very successful.  Modelling errors in our system model.  There seems 35 cm offset in x direction of DLL model output than real crane. We could solve this problem with little modification in system.
  34. 34. Discussion and Conclusions (Cont.) Solution to the offshore load transfer system  2D -> 3D Solution  Reference target is required to get from sensors of floating platform Tool tip target tracking operation
  35. 35. Discussion and Conclusions (Cont..) A real engineering experience with 3 steps.. 1) Numarial Modeling/Simulation :  Make the system with more software models(Lab view, dll model)  Less acuarate but easy to change and think. 2) HiL Method:  Make the sysem with more real equipments (PLC and switches) and improved model sysems (DLL model run on real time labview, Simulink model)  More acurate results and closer to reality.  It is cost saving safe method, befoure doing the actual task.  sucess of this method highly depend on acuracy of real system model. Here the given DLL model was acurate as the real machine works accordingly. 3) Real world test with actual devices (PLC, HMF real crane and real switches)  Solve the real world problem of offshore load transfer system
  36. 36. Thank You..!!