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Page 430 ï~~The Development of an Automatic Bagpipe Playing Device Hirohisa Ohta, Hiroshi Akita, Motomu Ohtani Waseda university JRE Hitachi Co., Ltd. Satosi Ishicado, and Masami Yamane Waseda university Waseda university Abstract Playing the bagpipe demands quick and accurate movement of fingers and a stable supply of air. The aim of this study is to develop an automatic bagpipe playing device that plays better than humans. In this paper, we present the design and the results of the performance test of the actuator of fingers that uses the step motors. At present,this automatic bagpipe playing device can play about 100 songs such as "Scotland The Brave", "Killworth Hills", and so on. 1. Introduction A bagpipe consists of chanter pipe for playing melodies, three drone pipes for continuous accompaniment, and a bag for storing air to send air continuously to the pipes. The chanter pipe has 8 finger holes, and the holes are only completely closed or opened, there are only 9 musical scales. Besides, grace notes are put in to each melodious note in order to put an accent. Consequently, playing the bagpipe entails control of the movement of the fingers and the supply of air. pipes holes, the width of the finger should be less than 20 mm in order to set them like human hands. 3. Hardware The nearest distance between two finger holes is 20 mm, while the width of the step motor is 45 mm. Consequently, it is impossible to set the finger directly on the axis of the motor. Therefore we used a driving belt to transmit force from the motor to the finger. Consequently, this enables the free setting of the motor by changing the length of the driving belt and enables the disposition of the motor like human hands by setting the m to the right and left alternately. Generally, a step motor is used in order to turn a rotor by exciting each coil one after another for positioning control. But in this study, it is used in order to give a reciprocating motion to the actuator by exciting only part of the coils. Considering the result of the static characteristics test of Fig. 2. it is clear that meeting a demand of nose tip's displacement and force for holding the finger hole is difficult in the case of opening and closing finger hole by simple phase excitation. So phase "B" is allotted to the position at which the finger hole close, and phase "A" is allotted away from the closing point in the direction of the rotation. Position of phase and finger is showed by Fig.3. To obtain the opening and closing motion of the nose tip, phase A and B are used. And to obtain the force for holding the finger hole, phase A is used. So when a finger closes its hole, phase B is excited for blow pipe pipe Fig. 1 Schematic of a bagpipe 2. Actuator's Specifications (1) Quickness of fingertips: The fingertip should open and close the holes in 20 msec with its displacement being more than 4 mm. (This enables playing 128th note at PJ=180.) (2) The force to hold the holes should be more than 100 gf. (3) Considering the intervals of the finger 7P.10 430 ICMC Proceedings 1993
Page 431 ï~~approximately only 10 msec. In this way, current consumption is economized. hole is closed, finger has some torque. Thus, the response in the beginning of its opening motion is slow. torque of specification---- angle of specification 1 phase excitation 0 2 Phase excitation A 1uu 1200 C7' 0 800 400 A AA t ~~~Â~6Â~ V dg I _.. 0 2 4 8 8 angular displacement deg.....input signal 1.4 sec I displacement of nose (a),When a finger closes its hole tip 10 Fig.2 The result of the static characteristic test (I=0.33A) p hase A....-:.'I _ _,........ p h a s e 8........- -........... -.. -.-.. _, -,, Sii............ phase A chanter pipe Fig.3 The relation between phase's positin and finger's position 4. Evaluation of Performance 4.1 Dynamic Characteristic Test The result of the dynamic characteristic test are shown in Fig.4. The response time for closing the finger hole is 7.4 msec, and that for its opening is 10.4 msec. These meet the necessary response time (within 20 msec) of the actuator. The response of opening finger hole is slower than that of its closing because of the by following reasons. (1) When a finger closes its hole, the two phases, A and B, are excited. But for opening a hole, only phase A is excited. (2) When a finger opens its hole, the nose tip is at a stable position of phase A, and the finger has no torque. But when the finger I input signal Idisplacement of nose1 I -. - _I-_. l 10.8 usec (b)lhen a finger closes its hole Fig.4 The result of the dynamic characteristic test 4.2 Consideration of Belt Drive This actuator has a belt drive, which has little influence on moment of inertia. To consider its influence on finger response, we examined the response time in case finger is directly fixed to the pulley of a motor. We found that the response has become a little quicker, but the overshooting of the nose tip when the finger hole is opened or closed has increased. Also, by applying the minimum necessary tension to the belt, a response identical to the case when the finger is fixed to the motor axis can be obtained, thus the use of a timing belt was considered suitable. 5. Summary Through the development of an actuator using a step motor, we can obtain a response time of 7.4 msec when closing a finger hole, and of 10.8 msec when opening a finger hole. The finger hole holding force is 281 gf, in the case finger displacement is 4 mm. In this way, it has become sufficiently possible to play grace notes, and the maintenance of this equipment has been enhanced efficiently. Reference Ohtani et al., 1993] Motomu Ohtani, asami Yamane, Yoshiro Tikahisa. The Development of an Automatic bagpipe Playing Device, Publication of the JSPE 1991 Spring Proceeding:pp361(1991) tip ICMC Proceedings 1993 431 7P.1O