On-the-fly position calibration of a robotic arm

A robotic device with a position sensing apparatus, comprising:

• a base;
• a robotic arm movably mounted to said base;
• a servo mechanism configured to cause movement of said robotic arm to move relative to said base through a range of motion along a predetermined path;
• position encoder means for sensing a relative position between said robotic arm and said base and producing a position signal indicating said relative position;
• an interrupt flag coupled to one of said robotic arm and said base;
• interrupt sensor means, coupled to the other one of said robotic arm and said base, for sensing said interrupt flag when said robotic arm moves through a verification position and for producing a position verification signal indicative thereof;
• and
• controller means, coupled to said position encoder means and said interrupt sensor means, for receiving said position signal and said position verification signal and for comparing the relative position indicated by said position encoder with said verification

A method for monitoring the positional integrity of a robotic device having a motor for driving the robotic device through a range of motion along a predetermined, fixed path with respect to a base including a verification position, the device including a position encoder which senses a relative position between the robotic device and the base, and produces a position signal indicating the relative position, an interrupt flag attached to one of the robotic device and the base, and an interrupt sensor means attached to the other one of the robotic device and the base, the method comprising the steps of:

• (1) detecting the interrupt flag with the interrupt sensor means when the robotic device moves through the verification position;
• (2) producing a position verification signal when the interrupt flag is detected by the interrupt sensor means;
• (3) recording the relative position of the robotic device indicated by the position encoder at the time the interrupt flag is detected;
• (4) comparing said relative position with a predetermined value;
• and
• (5) generating an error signal if the difference between said relative position and said predetermined value exceeds a fixed amount.