Automated inspection of spar web in hollow monolithic structure

A method for moving a distal portion of a modified scissor lift mechanism to a target vertical position, the vertical position of the distal portion relative to a starting vertical position being a nonlinear function of rotation of a horizontal lead screw coupled to a motor, comprising:

• (a) calculating a lead screw rotation angle required to achieve a specified extension height of the modified scissor lift mechanism using an inverse kinematics equation in which extension height is an input variable;
• (b) instructing the lead screw motor to rotate a required number of turns to reach the calculated lead screw rotation angle;
• (c) monitoring whether the number of lead screw motor rotations indicates that the target vertical position has been reached;
• and
• (d) stopping the motor when the target vertical position, as determined by lead screw rotation angle, has been reached.

A lifting system comprising:

• a lead screw in horizontal orientation;
• a motor coupled to said lead screw for driving rotation of said lead screw;
• a modified scissor lift mechanism coupled to said lead screw, a vertical position of a distal portion of said modified scissor lift mechanism being a nonlinear function of rotation of said lead screw;
• an encoder for measuring each rotation of the lead screw through a predetermined angle into a respective rotation encoder pulse, and
• a computer system programmed to control said motor in accordance with a motion control algorithm comprising:
• (a) calculating a lead screw rotation angle required to achieve a specified extension height of the modified scissor lift mechanism using an inverse kinematics equation in which extension height is input variable;
• (b) instructing the lead screw motor to rotate a required number of turns to reach that the calculated lead screw rotation angle;
• (c) monitoring whether the number of lead screw motor rotations indicates that the target vertical position has been reached;
• and
• (d) stopping the motor when the target vertical position, as determined by lead screw rotation angle, has been reached.

A system comprising:

• a hollow composite structure comprising a spar web and first and second skins;
• a tractor vehicle disposed under said second skin, said tractor vehicle comprising a first frame, a plurality of wheels rotatably mounted to said first frame and in contact with said second skin, first and second magnet poles mounted on said first frame;
• a first trailer vehicle disposed above said second skin and on one side of said spar web, said first trailer vehicle comprising a second frame, a plurality of wheels rotatably mounted to said second frame and in contact with said second skin, a third magnet pole carried by said second frame and magnetically coupled to said first magnet pole through said second skin, a horizontal lead screw, a motor coupled to said lead screw for driving rotation of said lead screw, a modified scissor lift mechanism coupled to said lead screw, a payload platform pivotably coupled to a distal portion of said modified scissor lift mechanism, and a non-destructive inspection sensor mounted to said payload platform, wherein a vertical position of said distal portion of said modified scissor lift mechanism is a nonlinear function of rotation of said lead screw;
• and
• a second trailer vehicle disposed above said second skin and on another side of said spar web, said second trailer vehicle comprising a third frame, a plurality of wheels rotatably mounted to said third frame and in contact with said second skin, a fourth magnet pole magnetically coupled to said second magnet pole through said second skin.