Development of a violin playing robot and its sound volume and pitch controls

Abstract

We developed a violin playing robot that consists of a bow mechanism and a string shifting mechanism and operates by sound feedback control. The bow mechanism was developed as a 2-degree-of-freedom moving mechanism that can independently adjust bow speed and bow pressure. The string shifting mechanism was also developed as a rigid mechanism that can withstand the high speed motion of the bowing mechanism. By using this mechanism, the robot can play the sound from the first string to the third string. In addition, we created a real-time sound volume control system. The element from the bow speed to the sound volume was modelled, and a PID controller was designed so that the constant control of the sound volume was achieved. Feedforward control of the sound volume, feedback control, and the combination control of both were performed for the constant sound volume. As a result of comparing setting time and standard deviation for target sound volume on the three methods, we confirmed that the combination control is superior. Furthermore, we created an on-line sound pitch control system to adjust the pitch by changing a finger position. It confirmed that the sound pitch can be adjusted quickly without overshoot.