End Effector Inspection Camera

The end effector mounted camera is used in the detailed visual inspection by the remote operator. The camera is mounted on a ring to the right of the end effector, with the axis of the camera coinciding with the Y axis of the robot's tool frame. This gives the operator the best vantage point for close up inspection of the drum, and allows the inspection of almost the entire visible drum surface without repositioning of the manipulator base.

The requirements for the camera are listed below.

• Minimal weight - Because of the limited payload capability of the end effector (2.2 lb.), the camera should be as light as possible, to allow as great a real payload as possible.
  
  
• Small size - A large bulky camera would interfere with the operation of the manipulator and increase the chance of collisions. Since it is being mounted to the manipulator's wrist, the camera must be small enough so that it does not interfere with rotations of the tool coordinate frame which are used during close inspection of the drum and sampling operations.
  
  
• Low power - Always a desirable characteristic for any component of a mobile battery powered system.
  
  
• Color - Color was deemed essential to the ability of the operator to identify suspect spots.
  
  
• 1/2 inch ccd and S-Video out - It was determined experimentally that an imaging array smaller than 1/2 inch on a color camera would not provide the necessary resolution to decode the bar code at the distance required. Also, separate intensity and color signals (Y/C) were found to be necessary for the image to be of high enough quality to discern 15 mil narrow bars on the bar code labels at the distance specified, hence an S-Video output is required.
  
  
• Rugged design - The camera should be able to withstand the shocks and vibrations associated with powered motion, and the occasional collision.
  
  

Of the many commercially available camera systems surveyed, including manufacturers such as Sony, Panasonic, and Mitsubishi, only the Pulnix TMC-7 with detachable remote head was found to meet all of the requirements. The hardest specification to fulfill was the small size and weight, because the weight and size of the lens must be added to that of the camera. The TMC-7 solves this problem by offering an option to separate the imaging head and lens from the rest of the camera body. A 4 foot cable connects the head to the body.

Only the remote imaging head and lens are mounted on the end effector to reduce the amount of mass carried by the arm and the possibility of interference with the manipulator's motion. The camera body is mounted to the manipulator's shoulder so that it exerts a force only along the negative J1 axis (down along the base joint's shaft) and therefore does not interfere with the robot's operation. The remote head mounting bracket is anchored behind the wrist force sensor, so that it does not interfere with operation of the force sensor during the inspection process.

The relevant specifications of the TMC-7 are listed in the table below.