Robotic system for servicing the heat exchanger tubes of a nuclear steam generator

A robotic arm system for maintaining a tool in a desired orientation while moving it along a trajectory having components in all three dimensions, comprising:

• a base assembly for cantileverly supporting a robotic arm;
• at least first, second and third arm segments for forming an articulated robotic arm,
• at least first and second motorized joint assemblies rotatably connecting said base assembly to said first arm segment, and said first and second arm segments, respectively, and including motor mechanisms for driving said assemblies, wherein said first and second joint assemblies are rotatable only around substantially vertical axes to prevent the application of cantileverly-induced torque on the motor mechanisms driving said assemblies, and
• a coupler means for detachably mounting one portion of the robotic arm of the system to the other portion to facilitate the installation of said arm in an area accessible only through a relatively narrow accessway, wherein said robotic arm has an even number of motorized joint assemblies, and said coupler means divides the robotic arm into two portions, each of which has the same number of joint assemblies.

A robotic arm system for maintaining a tool in a desired orientation while moving it along a trajectory having components in all three dimensions comprising:

• a base assembly for cantileverly supporting a robotic arm;
• wherein said base assembly includes locking means for detachably mounting said arm to the underside of a tubesheet having at least one vacant tube, including a plurality of radially extendible fingers for grippingly engaging the inner surface of said tube, wherein said fingers engage at least 40 percent of the circumference of the tube inner surface;
• at least first, second and third arm segments for forming an articulated robotic arm, and
• at least first and second motorized joint assemblies rotatably connecting said base assembly to said first arm segment, and said first and second arm segments, respectively, and including motor mechanisms for driving said assemblies, wherein said first and second joint assemblies are rotatable only around substantially vertical axes to prevent the application of cantileverly-induced torque on the motor mechanisms driving said assemblies.

A robotic arm system for moving an end effector in a desired orientation while moving it along a trajectory having components in all three dimensions within a radioactive channel head of a nuclear steam generator having a tubesheet, and a manway for affording access to said channel head, comprising:

• a base assembly for cantileverly supporting a robotic arm;
• at least first, second and third arm segments for forming an articulated robotic arm, and
• at least first and second motorized joint assemblies rotatably connecting said base assembly to said first arm segment, and said first and second arm segments, respectively, and including motor mechanisms for driving said assemblies;
• wherein said first and second joint assemblies are rotatable only in a plane parallel to the tubesheet both to prevent the application of cantileverly induced torque on said first and second motor mechanisms, and to minimize opportunities for mechanical interference between said arm and the walls of said channel head.

A robotic arm system for moving an end effector along a desired trajectory within a contained area of radioactivity comprising:

• an articulated robotic arm having a plurality of rotatable joint assemblies for rotating said joints a desired angle, each assembly including a motor mechanism having an electric motor means having a drive shaft, and a drive train having input and output shafts connected to said motor drive shaft and one of said joints, respectively;
• a control means for generating a signal for controlling the amount of electric power conducted to the electric motor means of each of said assemblies to control the angle of movement of said joints, and
• first and second resolver means having mechanical inputs connected to said motor drive shaft and said drive train output shaft, respectively, for providing separate feedback signals to said control means indicative of the angular position of said drive and output shafts, respectively,
• wherein the control means uses the feedback signal from the motor drive shaft to modulate the amount of power conducted to the electric motor of the assembly to avoid the superimposition of noise on the power control signal generated by the control means, and periodically compares the feedback signals of both resolvers to determine the integrity of the mechanical linkage between said motor and said drive train.

A method for controlling an articulated robotic arm having at least one rotatable joint assembly that includes a drive train having an output shaft for moving said arm, and a motor means having a drive shaft for driving said drive train, comprising the steps of

• a) generating a first electric signal indicative of the amount that the drive shaft of the electric motor means rotates;
• b) generating a second electric signal indicative of the angular position of the robotic arm by multiplying the number of drive shaft rotations by the gear ratio between the drive shaft of the motor means and the output shaft of the drive train, and
• c) modulating the amount of electric current conducted through the electric motor means by means of said second electric signal, and
• d) terminating the flow of current through said electric motor means when said second electric signal indicates that said arm has been moved to a desired position.