Master-Slave Electrically-Driven Manipulator for Shielded Cells

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The master-slave electrically-driven manipulator is designed for the shielded cell that is part of the facility for crushing the VVER-1000 spent fuel assemblies at the Experimental Demonstration Center of the Mining and Chemical Combine in Zheleznogorsk.

When in operation, the spent fuel crusher feeds the crushed SFA fragments into the shielded cell for screening, from where they move for further reprocessing. The manipulator returns the large fragments that have not passed through the screen to the crushing area for re-chopping. The operator sets the manipulator in manual mode with the master arm or remote controls to grip a fragment. The manipulator arm can move to the crushing area and back either in manual or automatic modes as programmed.

The design features of the manipulator come from the complicated shape and limited volume of the shielded cell. The choice fell on the kinematic configuration to include a system of shafts with wave-type reduction gears. It has significantly increased a positioning accuracy of the gripper while retaining its high load capacity.

All actuators of the electromechanical arm have an out-of-cell layout to ensure their protection from ionizing radiation and facilitate access during maintenance and debugging operations.

The electromechanical arm comes with six degrees of freedom. Separate electrical actuators set all joints of the manipulator's arm in rotational motion to translate it through drive shafts, series of bevel and wave-type gears. The end-effector is a gripper. Separate drives are in charge of rotating and moving the gripper upward/downwards and opening/closing its jaws.

 

Master-slave manipulator

 

The information and control (I&C) system ensures monitoring and control of the manipulator in manual and automatic modes. The manual mode allows moving each joint separately in different directions. The automatic mode guides several joints at a time along a preplanned path.

The I&C functions are:

  • data acquisition, display, control, and logging for the conditions of the manipulator and the I&C components,
  • testing of the manipulator and the I&C components,
  • the operator's command input and processing,
  • the path-planning calculations for the end-effector,
  • the manipulator motion control to avoid collision with objects and shielded cell walls,
  • actuator speed/acceleration control and limitation.

The manipulator is controlled remotely from a control panel in the operator's room. The operator interface includes a master arm and a touchpad to set the options of the manipulator arm movement as follows:

  • joint by joint,
  • along the coordinate axes X, Y, Z,
  • along a preplanned path,
  • along a new estimated path,
  • along the master arm's path.

The manual control is implemented through:

1) the master arm,

2) the touchpad. The touchpad ensures either the joint-by-joint control by setting a position for each of the six arm joints with action buttons or control of the gripper movement along the coordinate axes X, Y, Z inside the modeled shielded cell with collision detection.

In automatic mode, the manipulator gripper follows one of the preplanned paths, including the automatic return to its start point. The process goes along with the collision detection, too.

Sosny engineers developed the I&C software.

 

Control panel and master arm

 

Specifications:

In-cell workspace (L x W x H)  940 х 750 х 1100 mm 
Operating medium  air 
Gamma radiation dose rate in the arm operation area  less than 2.5·104 rad/h 
Lifting capacity at maximum outreach 10 kg 
Quantity of axes/degrees of freedom 
Stroke along axis A1  200 mm 
Angle of rotation around axis A2  360 degrees 
Angle of rotation around axis A3  ±110 degrees 
Angle of rotation along axis A4  360 degrees 
Angle of rotation along axis A5  360 degrees 
Angle of rotation around axis A6  360 degrees 
Jaw opening  80 mm 
Time of automatic transfer movement  less than 30 s 
Positioning error  ± 5 mm 
Weight  700 kg 

 

 

 

Manipulator movement diagram 

 

 

Testing of the master-slave manipulator in the mockup shielded cell at Sosny's plant

 

 

The manipulator elements contacting the radioactive environment are made of corrosion-resistant steel and are decontaminable. Seals protect the manipulator's internal mechanisms from moisture and dust.

The design of the master-slave manipulator is adaptable to shielded cells of various configurations to handle different objects.

 

 

 

 

 

 

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