Robotic control of therapeutic device on body surface considering contact force and moment

For ultrasound therapy, e.g. microbubbles delivery, physical contact between therapeutic device and body surface is important. To guarantee the entire contact of the device, we propose a control method considering contact force and reaction moment using a robotic system and sensors. We used a parallel link robot, which has three links and the holder to determine position and angle of the device. First we eliminated self-weight moment of the device using the sensors. Next we established a series of surface contact controls, which consists of (a) initial contact control, (b) balance contact control, and (c) angle restoration control. Then we performed evaluation experiments using soft material and human body. Contacted area was visualized and evaluated with color ink. Convergence time to the desired position and angle was also evaluated while monitoring contact force and moment. We concluded that the determination of appropriate parameters is important and dominant for the quality of the system.