A recent technique for treating tumors, photodynamic therapy, uses light and light-activated drugs. The treatment first injects a patient with a photosensitized drug that alone is harmless. But shining a laser on tissue saturated with the drug activates it and destroys the tissue.

“To direct the light, we developed a robot that skims a laser head along the patient's skin in circular or elliptical patterns,” says Lebanese University Assistant Professor and team leader Assad Kallassy. “This motion requires controlling motors for three translations and two rotations. Each axis requires a stepper motor.”

LabView from National Instruments, Austin, Texas, (ni.com) controls four of the steppers while a Microchip Technology microcontroller runs the z-axis motor. “We built the dual-processor control system around an NI PCI-7334 motion controller and digital signal processor,” says Kallassy.

The PCI-7334 uses commands coded in NI LabView along with configuration settings from NI's Measurement & Automation Explorer as roadmaps to generate command signals to move the motors.

“Software development began by simplifying our robot configuration for 2D applications and simulating movement and robots using LabView. Then we extrapolated the logic into 3D problems.” Unlike text-based programming languages, LabView uses icons to write applications. That makes software development significantly easier, says Kallassy. “Furthermore, the software has a huge library with many subroutine that we use extensively,” he adds.