Abstract: In the process of using high intensity focused ultrasound (HIFU) system to ablate tumor tissue, the irradiation trajectory needs to be optimized based on tumor’s shape. So the tumor can be effectively treated in the shortest time. Based on the first-order-Taylor series interpolation algorithm, the actual "linear velocity" concept was proposed, and the linear velocity error was improved for any kind of movement along parametric curves. The new control method can also effectively maintain the step-size shift and chord deviation within the permitted range. Particularly, the derivative of interpolation algorithm for spatial spiral trajectory was explained in details and its accuracy was analyzed. The μC/OS II RTOS kernel was used to control the movement, and some movement, such as straight line, ellipse, spirals, etc., were realized to validate the proposed interpolation method and accuracy evaluation method. The experiments show that the stability of the linear velocity is also verified and it can also effectively maintain the step-size shift and chord deviation within the permitted range.  

Key words: mobile mechanism, parametric equation, linear velocity, error analysis, spiral