Magnetic Actuator with Multiple Vibration Components ... - MDPI

actuators Article

Magnetic Actuator with Multiple Vibration Components Arranged at Eccentric Positions for Use in Complex Piping Hiroyuki Yaguchi *, Kazushige Kamata and Hiroshi Sugawara Actuator laboratory, Faculty of Engineering, Tohoku Gakuin University, 1 Chome-3-1 Tsuchitoi, Aoba Ward, Sendai 980-8511, Japan; [email protected] (K.K.); [email protected] (H.S.) * Correspondence: [email protected]; Tel.: +81-223-687-104 Academic Editor: Delbert Tesar Received: 14 April 2016; Accepted: 15 June 2016; Published: 23 June 2016

Abstract: This paper proposes a magnetic actuator using multiple vibration components to perform locomotion in a complex pipe with a 25 mm inner diameter. Due to the desire to increase the turning moment in a T-junction pipe, two vibration components were attached off-center to an acrylic plate with an eccentricity of 2 mm. The experimental results show that the magnetic actuator was able to move at 40.6 mm/s while pulling a load mass of 20 g in a pipe with an inner diameter of 25 mm. In addition, this magnetic actuator was able to move stably in U-junction and T-junction pipes. If a micro-camera is implemented in the future, the inspection of small complex pipes can be enabled. The possibility of inspection in pipes with a 25 mm inner diameter was shown by equipping the pipe with a micro-camera. Keywords: magnetic actuator; pipe inside mover; eccentric position; complex pipe; multiple vibration components

1. Introduction There are several pipes in power generating units and chemical plants. The inspection of existing corrosion and cracks is conducted in a pipe to check the soundness of these pipes. When inspecting from the outside of a pipe by using techniques such as an ultrasonic test method [1,2] or eddy current testing [3,4], it is impossible to estimate minute internal cracks. Therefore, a tool capable of inspecting the condition of a pipe surface is required for safety reasons. In general, a large-diameter-type pipe with a 450 mm internal diameter is used in a power generating unit and is connected to a small pipe with an inner diameter ranging from 25 to 35 mm. Accordingly, a tool capable of inspecting the interior of a 25-mm-internal-diameter pipe is required. Several studies have investigated mechanisms for a robot capable of inspecting such pipes. The mechanisms include devices using piezoelectric elements [5,6], shape-memory alloys [7,8], external magnetic fields [9–11], and electromagnetic motors [12–14]. An actuator combined with an electromagnetic force and mechanical vibration was previously proposed by the authors [15–19]. However, robots capable of inspection in a pipe with an inner diameter of 25 mm have not yet been developed except in a small study [20]. It should be possible to create a micro-motor which generates torque and then transforms it into movement through the complex pipe in the same way as standard actuators, but the torque produced by micro-motors is quite small. This propulsion scheme would therefore require a geared motor with a very complex structure. This paper proposes a new type of magnetic actuator capable of locomotion in a small complex pipe with a U-junction and a T-junction. For movement in a pipe with an inner diameter of less than 25 mm, two vibration components were not attached to the center; this differs from methods in

Actuators 2016, 5, 19; doi:10.3390/act5030019

www.mdpi.com/journal/actuators

Actuators 2016, 5, 5, 1919 Actuators 2016,

2 of 1111 2 of

previous papers [18,19] proposed by the authors. It was confirmed that this magnetic actuator is able previous papers [18,19] proposed by the authors. It was confirmed that this magnetic actuator is able to move in the complex pipe system by using only two amplifiers, one signal generator, and a DC to move in the complex pipe system by using only two amplifiers, one signal generator, and a DC power supply without control units. power supply without control units. Structureof ofaaMagnetic MagneticActuator Actuatorand andVibration VibrationComponents Components 2.2.Structure Figure1 1shows showsthe thevibration vibrationcomponents componentsofofthetheproposed proposed magnetic actuator.Vibration Vibration Figure magnetic actuator. components11and and 22 were frame. Vibration component 3 was at a right components were attached attachedtotoananacrylic acrylic frame. Vibration component 3 attached was attached at angle to vibration components 1 and 2. Vibration components 1 and 2 had permanent magnets and a right angle to vibration components 1 and 2. Vibration components 1 and 2 had permanent magnets springs with thethe same properties. component33were wereslightly slightly and springs with same properties.The Themagnets magnetsand andsprings springs in in vibration vibration component differentcompared comparedwith withthose thoseininvibration vibrationcomponents components1 1and and2.2.Due Duetotothe thedesire desiretotoincrease increasethe the different turning moment in a T-junction pipe, vibration components 1 and 2 were attached off-center on the turning moment in a T-junction pipe, vibration components 1 and 2 were attached off-center on the acrylicplate platewith withananeccentricity eccentricityofof2 2mm. mm.Previous Previoustesting testingshowed showedthat thatthe theeccentric eccentricposition positionhardly hardly acrylic influences the straight motion of the actuator. Since a Charge-Coupled Device (CCD) CCD microinfluences the straight motion of the actuator. Since a Charge-Coupled Device (CCD) micro-camera camera was not available, the actuator was not equipped with a CCD camera, although a previous was not available, the actuator was not equipped with a CCD camera, although a previous study [19] study [19] used a CCD with a cube side of 8.5 mmmass and aoftotal used a CCD camera withcamera a cube shape, a sideshape, lengthaof 8.5length mm and a total 1.2 g.mass of 1.2 g. Vibration component 1

Acrylic plate

7 mm

2 mm

Perm anent magnetΦ5 m m

6 mm

Iron shield

2 mm

Vibration component 3 Iron pole 1

Plan Vibr ation component 3

Vibration component 1 Iron pole 1

Vibr ation component 1 Iron pole 1

Vibration component 2

Acrylic plate

Acrylic plate Vibration component 3


Iron pole 2

Front view

Iron pole 2

Sideview

Figure Figure1.1.Vibration Vibrationcomponents componentsofofthe themagnetic magneticactuator. actuator.

Eachvibration vibrationcomponent component was was composed of a translational spring was Each ofaapermanent permanentmagnet magnetand and a translational spring adhered to to thetheacrylic in the thetranslational translationalspring. spring.The The was adhered acrylicframe. frame.An Anelectromagnet electromagnet was was inserted inserted in translational spring of vibration components 1 and 2 was constructed from stainless steel and had translational spring of vibration components was constructed from stainless steel and hadan diameter of 6.5 mm, a free length of 8 mm, and aand spring constant of k = 1491 Vibration anouter outer diameter of 6.5 mm, a free length of 8 mm, a spring constant of k N/m. = 1491 N/m. component 3 was constructed from stainless steel and had an outer diameter of 4.5 mm, a free Vibration component 3 was constructed from stainless steel and had an outer diameter of 4.5 length mm, 6.5length mm, and spring of k = 1231 N/m.ofThe magnets of vibrationmagnets components a of free of a6.5 mm, constant and a spring constant k =permanent 1231 N/m. The permanent of 1 and 2components were cylindrical magnetized in themagnetized axial direction. The magnets 5 mm in vibration 1 and NdFeB 2 were cylindrical NdFeB in the axial direction.were The magnets diameter 2 mm inand height. That vibration was cylindrical NdFeB magnetized were 5 mmand in diameter 2 mm in of height. Thatcomponent of vibration3 component 3 was cylindrical NdFeBin the axial direction. Thedirection. magnets The weremagnets 5 mm inwere diameter 2 mm inand height. That of the vibration magnetized in the axial 5 mmand in diameter 2 mm in height. That of component 3 was cylindrical NdFeB magnetized in the axial direction and measured 4 mm in the vibration component 3 was cylindrical NdFeB magnetized in the axial direction and measured diameter and 2 mm in height. The surface magnetic flux density written in the data sheet for vibration 4 mm in diameter and 2 mm in height. The surface magnetic flux density written in the data sheet components 1 and 3 was 1360 and 340 360 mT,and respectively. The permanent were shielded with for vibration components and 3 was 340 mT, respectively. Themagnets permanent magnets were

Actuators 2016, 5, 19

3 of 11


3 of 11

shielded with iron to prevent with interference withwhen each other when thecomponents vibration components iron to prevent interference each other the vibration as shown as in shown Figurein1 Figure 1 were vibrated. were vibrated. For components 11 and and 2, 2, the the electromagnet consisted of of an an iron iron core For vibration vibration components electromagnet consisted core with with aa diameter diameter of 2.5 mm and a length of 7 mm with 350 turns of 0.1-mm-diameter copper wire. For vibration of 2.5 mm and a length of 7 mm with 350 turns of 0.1-mm-diameter copper wire. For vibration component 3, the the electromagnet electromagnetconsisted consistedofofan aniron ironcore corewith witha adiameter diameter 2 mm and a length component 3, ofof 2 mm and a length of of 8 mm with 360 turns 0.1-mm-diametercopper copperwire. wire.The Thegap gapbetween betweenthe the electromagnet electromagnet and and the the 8 mm with 360 turns ofof0.1-mm-diameter permanent in the was 33 mm. An iron iron pole to aa location permanent magnet magnet in the static static condition condition was mm. An pole was was attached attached to location 66 mm mm from This iron iron pole pole had an outer mm and and a a free from the the center center of of the the acrylic acrylic plate. plate. This had an outer diameter diameter of of 2.3 2.3 mm free length length of 8.5 mm. mm. As As shown shown in in Figure Figure 2, by using using an an iron iron plate plate with with aa thickness thickness of of 1.5 1.5 mm, mm, electromagnets electromagnets 11 of 8.5 2, by and 2 were magnetically combined. When a direct current of 0.2 A was inputted to electromagnets and 2 were magnetically combined. When a direct current of 0.2 A was inputted to electromagnets 11 and 2, the surface magnetic flux density with the iron plate was 16.69 mT, whereas that without the iron plate was 10.93 mT. mT. Electromagnet 1 Acrylic frame

Vibration component 1 Electromagnet 3 Acrylic plate

Iron plate

Iron plate Vibration component 2

Electromagnet 2 Figure an iron iron plate. plate. Figure 2. 2. Coupling Coupling of of the the electromagnet electromagnet by by an

As shown in Figure 3, the magnetic actuator was composed of the three vibration components, As shown in Figure 3, the magnetic actuator was composed of the three vibration components, four shape-memory-alloy (SMA) (TOKI Corporations, Tokyo, Japan, Trademark: BioMetal) coils four shape-memory-alloy (SMA) (TOKI Corporations, Tokyo, Japan, Trademark: BioMetal) coils labeled A, B, C, and D, two-layer compound materials labeled A, B, C, and D, eight copper conductors, labeled A, B, C, and D, two-layer compound materials labeled A, B, C, and D, eight copper conductors, and an acrylic cap and frame. The compound materials A and B were also attached to vibration and an acrylic cap and frame. The compound materials A and B were also attached to vibration components 1 and 2. The compound materials C and D were also attached to iron poles 1 and 2. The components 1 and 2. The compound materials C and D were also attached to iron poles 1 and 2. The compound materials A and B, which support the actuator in the pipe, were composed of natural compound materials A and B, which support the actuator in the pipe, were composed of natural rubber and silicone rubber. The compound materials measured 50 mm in length, while the thickness rubber and silicone rubber. The compound materials measured 50 mm in length, while the thickness of the natural rubber was 1.5 mm and that of the silicone rubber was 1 mm. Compound materials C of the natural rubber was 1.5 mm and that of the silicone rubber was 1 mm. Compound materials C and D, which turn the actuator in a T-junction pipe, had the same thickness as that of compound and D, which turn the actuator in a T-junction pipe, had the same thickness as that of compound materials A and B, but had a total length of 45 mm. When a direct current is applied to the SMA coil materials A and B, but had a total length of 45 mm. When a direct current is applied to the SMA coil by connection to a DC power supply or a battery, the temperature of the SMA coil becomes higher by connection to a DC power supply or a battery, the temperature of the SMA coil becomes higher than the transition temperature. Accordingly, the SMA coil contracts. This action causes compound than the transition temperature. Accordingly, the SMA coil contracts. This action causes compound materials A, B, C, and D to completely close. Reverse movement is enabled by using the opening and materials A, B, C, and D to completely close. Reverse movement is enabled by using the opening and closing of compound materials A and B, as shown in a previous study [15]. This actuator performs a closing of compound materials A and B, as shown in a previous study [15]. This actuator performs a reciprocating movement in a straight pipe using vibration components 1 and 2. By combining vibration reciprocating movement in a straight pipe using vibration components 1 and 2. By combining vibration components 1 or 2 and 3, this actuator can perform rotary movement in a pipe. In opening and closing components 1 or 2 and 3, this actuator can perform rotary movement in a pipe. In opening and closing compound material C or D, the iron pole becomes a supporting point of the turning movement in a compound material C or D, the iron pole becomes a supporting point of the turning movement in a complex pipe. Table 1 shows the properties of the SMA coil. complex pipe. Table 1 shows the properties of the SMA coil. Figure 4 shows the complete structure of the proposed magnetic actuator. The actuator was Figure 4 shows the complete structure of the proposed magnetic actuator. The actuator was 31 mm 31 mm in length, and the total mass was 7.34 g. The length of the compound material changed from in length, and the total mass was 7.34 g. The length of the compound material changed from 22 mm 22 mm to 30 mm. The actuator can move inside the pipe from 23 mm to 27 mm by the flexibility of to 30 mm. The actuator can move inside the pipe from 23 mm to 27 mm by the flexibility of the the compound material. Figure 5 shows a photograph of the magnetic actuator. compound material. Figure 5 shows a photograph of the magnetic actuator.

Actuators 2016, 5, 19 Actuators Actuators 2016,2016, 5, 195, 19

4 of 11 4 of 411of 11

Compound Compound material material D D

Compound Compound material material B B Copper Copper conductor conductor SMA-A SMA-A

Compound Compound material material A A

Natural Natural rubber rubber Silicone Silicone rubber rubber 1 mm 1 mm

Compound Compound material material C C

Copper Copper conductor conductor

1.5 mm 1.5 mm

Compound material Compound material

PlanPlan Acrylic Acrylic cap cap

Acrylic Acrylic cap cap


SMA-A SMA-A


Compound Compound material material C C

SMA-B SMA-B Compound Compound material material B B SMASMAD D

SMA-B SMA-B SMA-A SMA-A

SMA-D SMA-D

Compound Compound material material D D

Front Front viewview

Compound Compound material material B B

SideSide viewview

Figure 3. Structure of the magnetic actuator. Figure 3. of magnetic actuator. Figure 3. Structure Structure of the the magnetic actuator. Table 1. Properties of the shape-memory-alloy (SMA) Table 1. Properties of the the shape-memory-alloy (SMA) coil.coil. Table 1. Properties of shape-memory-alloy (SMA) coil.

6 mm

o

31 mm

19 mm 19 mm

23 mm 27 mm 23 mm 27~mm

~

FigureSize 4. Sizethe of the magnetic actuator. Figure Figure 4. 4. Size of of the magnetic magnetic actuator. actuator.

31 mm

o 10 10

400 Ω

60–65 ˝ C

150 µm

6 mm

0.62 mm

4 mm

SMA coil

Diameter of Wire Transformation Transformation Point Resistance Resistance Meter Outer Diameter Diameter of Wire Point Per Per Meter Outer Diameter Outer Diameter Diameter of Wire Transformation Point Resistance Per Meter 60–65 0.620.62 mmmm 150 150 μm μm 60–65 °C °C 400 400 Ω Ω

4 mm

SMA SMA coilcoil

Actuators 2016, 5, 19 Actuators 2016, 5, 19 Actuators 2016, 5, 19

5 of 11 5 of 11 5 of 11

Figure 5. Photograph of magnetic actuator. Figure Figure5.5.Photograph Photographofofmagnetic magneticactuator. actuator.

3. Principle of Linear and Rotational Motion 3.3. Principle Principle of of Linear Linear and and Rotational Rotational Motion Motion It is assumed that SMA coils B, C, and D contract, compound materials B, C, and D are ItItisisassumed thatthat SMA coilscoils B, C, B, andC,D and contract, compound materials B, C, and D are completely assumed SMA compound and D are completely closed, and only compound materialDAcontract, is open, as shown inmaterials Figure 6. B, TheC,principle of closed, and only compound material A is open, as shown in Figure 6. The principle of6.linear locomotion completely closed, and only compound material A is open, as shown in Figure The principle of linear locomotion for this magnetic actuator was demonstrated in a previous study [16]. The frictional for this magnetic actuator was demonstrated in a previous study [16]. The frictional force between the linearbetween locomotion this magnetic actuator waspipe demonstrated in a alternately previous study [16].one Theperiod frictional force the for compound material and the wall changes during of compound material and the pipe wall changes alternately during one period ofduring vibration, asperiod shownof force between the compound material and the pipe wall changes alternately one vibration, as shown in Figure 6a,b. invibration, Figure 6a,b. as shown in Figure 6a,b.

z z

z z

Compound Compound A material material A

Direction of Direction mass m of mass m

Compound Compound material A material A

Direction of Direction mass m of mass m

Sliding Sliding

Sliding Sliding

No No sliding sliding

No No sliding sliding

(a) (a)

(b) (b)

Figure 6. Principle of linear locomotion. (a) Linear movement; (b) No linear movement. Figure6.6.Principle Principleofoflinear linearlocomotion. locomotion.(a) (a)Linear Linearmovement; movement;(b) (b)No Nolinear linearmovement. movement. Figure

All vibration components were driven at the same frequency. When a sinusoidal electric current All vibration components were driven at the same frequency. When a sinusoidal electric current was applied to thecomponents electromagnet, displacement of the vibration component synchronized in the All vibration werethe driven at the same frequency. When a sinusoidal electric current was applied to the electromagnet, the displacement of the vibration component synchronized in an the current waveform. Figure 7 showsthe thedisplacement displacements 1, 2, and 3 when was applied to the electromagnet, of of thevibration vibrationcomponents component synchronized in the current waveform. Figure 7 shows the displacements of vibration components 1, 2, and 3 when an electric waveform. current is applied electromagnets 1, 2, and of 3, respectively. This figure results current Figure to 7 shows the displacements vibration components 1, shows 2, and 3the when an electric current is applied to electromagnets 1, 2, and 3, respectively. This figure shows the results when the displacements of electromagnets vibration components and 3 wereThis synchronized. this condition, electric current is applied to 1, 2, and 1, 3, 2, respectively. figure showsInthe results when when the displacements of vibration components 1, in 2, Figure and 3 were synchronized. In this condition, the actuator rotated in a clockwise direction, as shown 7. This actuator can turn in a counterthe displacements of vibration components 1, 2, and 3 were synchronized. In this condition, the actuator the actuator rotatedby in achanging clockwise direction, as shownvibration in Figurecomponents 7. This actuator can turn a counterclockwise phaseinbetween as in shown in a rotated in adirection clockwise direction, asthe shown Figure 7. This actuator can turnby in a180°, counter-clockwise clockwise direction by changing the phase between vibration components by 180°, as shown in a ˝ , as shown previous study [16]. Thus, the magnetic actuator undergoes linearby and movement based direction by changing the phase between vibration components 180rotational in a previous previous study [16]. Thus, the magnetic actuator undergoes linear and rotational movement based on the [16]. difference frictional force between the forward andand backward movement of the compound study Thus,inthe magnetic actuator undergoes linear rotational movement based on the on the difference in frictional force between the forward and backward movement of the compound material. difference in frictional force between the forward and backward movement of the compound material. material.

component 1 x

material A (Contact)

y

Actuators 2016, 5, 19 Actuators 2016, 5, 19

y

6 of 11 6 of 11


Vibration Vibration com component 1ponent 3

Vibration com ponent Vibration component 1 2 x

Compound Compound Pipematerial C (No contact) material A (Contact)

(a)y

(b)

Figure 7. Principle of rotational motion. (a) Vibration of components; (b) Production of moment by vibration. y

Vibration component 3 In summary, this magnetic actuator can Vibration move with straight movement if vibration components Compound material C component 2 Vibration 1 and 2 are driven. The actuator is able to rotate in the pipe by changing the phase difference of the (No contact) com ponent 3 displacement between vibration component 3 and vibration components 1 and 2. The compound materials convert the force generated by the vibration components into one-way movement. By the (a) (b) use of flexible materials, this actuator can move in the pipe with different diameters of 23 mm to 27 mm. Reversible movement is enabled by using the opening and closing of compound materials A Figure 7. ofofrotational motion. (a)(a) Vibration of of components; (b)(b) Production of moment by Figure 7. Principle Principle rotational motion. Vibration components; Production of moment and B, as shown in a previous study [15]. vibration. by vibration. 4. Basic Locomotive of Magnetic In summary, thisCharacteristics magnetic actuator can moveActuator with straight movement if vibration components In summary, this magnetic actuator can move with straight movement if vibration components 1 1 and 2 are driven. The actuator is able to rotate in the pipe by changing the phase difference of the and 2An areexperimental driven. The test actuator is able to rotate in the by changing of the was conducted by using thepipe apparatus shownthe in phase Figuredifference 8. The resonant displacement between vibration component 3 and vibration components 1 and 2. The compound displacement between vibration component 3 and vibration by components 1 and 2.apparatus. The compound frequency of the magnetic actuator was 140 Hz as measured the experimental In this materials convert the force generated by the vibration components into one-way movement. By the materials convert force cables generated bycables the vibration into one-way movement. theSMA use measurement, 12the electric (four to threecomponents electromagnets and eight cables to By four use of flexible materials, this actuator can move in the pipe with different diameters of 23 mm to of flexible materials, this actuator can move in the pipe with different diameters of 23 mm to 27 mm. wires) were used. A photograph of the experimental setup is shown in Figure 9. A CCD micro-camera 27 mm. Reversible movement is enabled by using the opening and closing of compound materials A Reversible movement is of enabled using the opening and closing of compound materials A and B, as with an outer diameter 8 mm by and a length of 10 mm was not available, as mentioned previously. and B, as shown in a previous study [15]. shown a previous study Instead,inan additional mass[15]. of 2 g was loaded in the actuator to represent two micro-cameras, and measurements were carried out. 4. Basic Locomotive Characteristics of Magnetic Actuator 4. Basic Locomotive Magnetic Actuator Figure 10 showsCharacteristics the relationshipofbetween the load mass and the vertical upward speed for a An experimental test was conducted by using the apparatus shown in Figure Figure 8.electromagnet The resonant resonant straight pipe with an inner diameter of 24 and 26 mm when the input current into the An experimental test was conducted by using the apparatus shown in 8. The frequency of the magnetic actuator was 140 Hz as measured by the experimental apparatus. In this this of vibration 1 and 2 waswas 0.3 140 A. In electric apparatus. current capable of frequency ofcomponents the magnetic actuator Hzthis as actuator, measuredthe bymaximum the experimental In measurement, 12 electric cables (four cables to three electromagnets and eight cables to four SMA input is 0.3 A. After this, the speed of the actuator was measured with an electric current of 0.3 A. measurement, 12 electric cables (four cables to three electromagnets and eight cables to four SMA wires) were indicates used. A A photograph photograph of the the experimental experimental setup is shown shown in40.5 Figure 9. A CCD micro-camera This figure that the magnetic actuator wassetup able to climb at mm/s a load wires) were used. of is in Figure 9. Awhen CCD pulling micro-camera with an outer diameter 88 mm mmdiameter and 10 was as massan of outer 20 g through anof of 26 of mm. The of available, the actuator for the casepreviously. of no load with diameter ofinner and aa length length of 10 mm mm speed was not not available, as mentioned mentioned previously. Instead, an additional mass g was was loaded loaded in2the the actuator to represent represent two micro-cameras, micro-cameras, and was 70.2 an mm/s. Since vibration 1 and were not attached to the center of the acrylic plate, Instead, additional mass of of components 22 g in actuator to two and measurements were carried out. this magnetic actuator demonstrated moderately high performance. measurements were carried out. Figure 10 shows the relationship between the load mass and the vertical upward speed for a straight pipe with an inner diameter of 24 and 26 mm when the input current into the electromagnet of vibration components 1 and 2 was 0.3 A. In this actuator, the maximum electric current capable of Amplifier input is 0.3 A. After this, the speed of the actuator was measured with an electric current of 0.3 A. 2ch. Power meter This figure indicates that the magnetic actuator was able to climb at 40.5 mm/s when pulling a load Amplifier mass of 20 g through an inner diameter of 26 The speed of the actuator for the case of no load DCmm. power supply was 70.2 mm/s. Since vibration components 1 and 2 were not attached to the center of the acrylic plate, this magnetic actuator demonstrated moderately high performance. 2ch. function generator Amplifier Figure 8. 8. Experimental Experimental apparatus. apparatus. Figure 2ch. Power meter Amplifier DC power supply Figure 10 shows the relationship between the load mass and the vertical upward speed for a straight pipe with an inner diameter of 24 and 26 mm when the input current into the electromagnet 2ch. of vibration components 1 and 2 was 0.3 A. In this actuator, the maximum electric current capable function of input is 0.3 A. After this, the speed of the actuator was measured with an electric current of 0.3 A. generator This figure indicates that the magnetic actuator was able to climb at 40.5 mm/s when pulling a load mass of 20 g through an inner diameter of 26 mm. The speed of the actuator for the case of no load Figure 8. Experimental apparatus.


7 of 11

was 70.2 mm/s. Since vibration components 1 and 2 were not attached to the center of the acrylic plate, this magnetic demonstrated moderately high performance. Actuators 2016, actuator 5, 19 7 of 11 Actuators 2016, 5, 19 Actuators 2016, 5, 19

7 of 11 7 of 11

Vertical upward speed (mm/s) Vertical upward speed (mm/s) Vertical upward speed (mm/s)

Figure 9. Photograph of experimental apparatus. Figure apparatus. Figure9.9.Photograph Photograph of of experimental experimental apparatus. Figure 9. Photograph of experimental apparatus.

80 80 80 60 60 60 40 40 40 20 20 20

○ : 26 mm ○ : 26 mm △ ○ :: 24 26 mm mm △ : 24 mm △ : 24 mm

0 0 0

10 10 10 (g) Load mass Load mass (g) Load mass (g)

20 20 20

Figure 10. Relationship between load mass and vertical upward speed. Figure 10.Relationship Relationship between load load mass and vertical upward speed. Figure and vertical verticalupward upwardspeed. speed. Figure10. 10. Relationshipbetween between load mass mass and

Speed (mm/s) Speed (mm/s) Speed (mm/s)

Figure 11 shows the relationship between the tilt angle α of the straight pipe and the speed with Figure 11 shows the relationship between the tilt angle α of the straight pipe and the speed with Figure 11 shows therelationship relationship betweenof the tilt α the pipe speed with Figure shows the between the angle α of ofwhen thestraight straight pipeand andthe the speed with regard to a11straight pipe with inner diameters 24tilt and 26 mm the actuator had no load mass. regard to a straight pipe with inner diameters of 24 and 26 mm when the actuator had no load mass. regard a straight pipe with inner diameters of mm when had nono load mass. The tilt α was varied from −90° (straightof down) to26 90° (straight up). In this figure, the vertical regard to to aangle straight pipe with inner diameters 24 and and 26 mm whenthe theactuator actuator had load mass. The tilt angle α was varied from −90° (straight down) to 90°˝ (straight up). In this figure, the vertical ˝the The angle αwas was51.6 varied from −90° (straight down) to InInthis figure, the vertical upward speed mm/s when inner diameter of90° the(straight pipe wasup). 24 mm and the input current The tilttilt angle α was from ´90 (straight down) to this figure, the vertical upward speed wasvaried 51.6 mm/s when the inner diameter of90 the (straight pipe was up). 24 mm and the input current upward speed was 51.6 mm/s when the inner diameter diameter the pipe was 2424 mm and the input current was 0.3speed A. Forwas the pipe with anwhen innerthe diameter of 24 mm,of the speed when moving straight down was upward 51.6 mm/s inner of the pipe was mm and the input was 0.3 A. For the pipe with an inner diameter of 24 mm, the speed when moving straight downcurrent was was 0.3 A. For the pipe with an inner diameter of 24 mm, the speed when moving straight down was about 2.16 times that when moving straight up. wasabout 0.3 A. Fortimes the pipe with an inner straight diameter of 24 mm, the speed when moving straight down was 2.16 that when moving up. about 2.16 times that whenmoving movingstraight straightup. up. about 2.16 times that when ○ : 26 mm ○ : 26 mm △ ○ :: 24 26 mm mm △ : 24 mm △ : 24 mm

200 200 200

100 100 100

0 0 0-90 -90 -90

-60 -60 -60

-30 0 30 -30 0 30 -30 0 30 Tilt angle (deg.) Tilt angle (deg.) Tilt angle (deg.)

60 60 60

90 90 90

Figure 11. Relationship between tilt angle and speed. Figure 11. Relationship between tilt angle and speed. Figure11. 11.Relationship Relationship between between tilt Figure tilt angle angleand andspeed. speed.

Figure 12 shows the relationship between the input current and the vertical upward speed for Figure 12 shows the relationship between the input current and the vertical upward speed for Figure pipe 12 shows relationship between thewhen input the current the vertical speed for the straight with the an inner diameter of 24 mm inputand current into theupward electromagnet of the straight pipe with an inner diameter of 24 mm when the input current into the electromagnet of the straight pipe with an inner diameter of 24 The mm vertical when the input current into 19.2 the electromagnet of vibration components 1 and 2 was changed. upward speed was mm/s when the vibration components 1 and 2 was changed. The vertical upward speed was 19.2 mm/s when the vibration components 1 and 2 was changed. The vertical upward speed was 19.2 mm/s when the


8 of 11

60

Vertical upward speed (mm/s)

Vertical upward speed (mm/s)

Figure 12 shows the relationship between the input current and the vertical upward speed for 2016, 5, 19with an inner diameter of 24 mm when the input current into the electromagnet 8 of 11 of theActuators straight pipe Actuators 2016, 5, 19 8 of 11 the vibration components 1 and 2 was changed. The vertical upward speed was 19.2 mm/s when input current was 0.2 A. On the other hand, it was 38.1 mm/s when the input current was 0.25 A. The input current was 0.2 A. On the other hand, it was 38.1 mm/s when the input current was 0.25 A. The input currentspeed was 0.2 A. On the other hand, itproportionally was 38.1 mm/s to when the input current was 0.25 A. The vertical upward of the actuator increases the value of the input current. When verticalvertical upward speed of the actuator increases proportionally to the value of the input current. When upward speed of the actuator increases proportionally to the value ofactuator the inputcan current. When input current into the electromagnet is low, low, such such as 0.2 A, this magnetic hardly pull thethe input into the is actuator can hardly the current input current intoelectromagnet the electromagnet is low, suchasas0.2 0.2A, A,this this magnetic magnetic actuator can hardly pullpull the load mass. the load themass. load mass.

50

60 50

40 40 △△: 24 : 24mm mm

30 30 20 20 10 10 0 0 0.20.2

0.25 0.25

0.3 0.3

Input current(A) (A) Input current Figure 12. Relationship between tiltangle angleand andspeed. speed. Figure 12.Relationship Relationship between tilt Figure 12. between tilt angle and speed.

5. Movement in a Complex Pipe Movement inaaComplex Complex Pipe 5. 5.Movement in Pipe Figure 13 shows details of a curved pipe with a curved part and step parts of 1 mm in the pipe. Figure shows detailsofofa acurved curvedpipe pipewith with acurved curvedpart partand andstep stepparts partsof of 11 mm mm in in the the pipe. pipe. In Figure 1313 shows details In addition, the diameters of the curved part andathat of an entrance part for this pipe were different. In addition, the diameters of the curved part and that of an entrance part for this pipe were different. addition, the diameters of the curved part and that of an entrance part for this pipe were different. Step of 1 mm

Detail of section A-A'

A ' A' L = 60 mm

L = 60 mm 35 mm 35 mm

A

26.2 mm

Step of 1 mm

Step of 1 mm

A

24.2 mm

24.2 mm 33 mm 33 mm Detail of section A-A'

26.2 mm

33 mm

24.2 mm

33 mm

24.2 mm

Step of 1 mm

26.2 mm 33mm mm 26.2

33 mm Figure 13. Detail of a curved pipe. Figure 13. Detail of a curved pipe. Figure 13. Detail of a curved pipe. This actuator required movement ability over a wide range of inner diameters ranging from 24.2 toactuator 26.2 mm. This movement complex pipe was over made polyvinyl chloride. The coefficient of friction This actuator required ability a of wide range of inner diameters ranging from 24.2 This required movement ability over a wide range of inner diameters ranging from the complex two rubber armswas andmade the inner wall of the pipe was 0.6. Thecoefficient distance of of thefriction measurement to 24.2 26.2between mm. This pipe of polyvinyl chloride. The between to 26.2 mm. This complex pipe was made of polyvinyl chloride. The coefficient of friction set asarms 60 mmand for the one inner curvedwall part of and two straight parts. Thedistance measurements the average speeds thebetween twowas rubber pipe waspipe 0.6.was The of theofof measurement was set the two rubber arms and the innerthe wall of the 0.6. The distance the measurement were carried out for two moving patterns in the horizontal and vertical directions as shown in as was 60 mm for60one andpart twoand straight parts. parts. The measurements of the speeds were set as mmcurved for onepart curved two straight The measurements ofaverage the average speeds Figure 14. In the case of pattern II compared with pattern I, the body of the magnetic actuator in the carried for two patternspatterns in the horizontal and vertical directions as shown Figure were out carried out moving for two moving in the horizontal and vertical directions as in shown in 14. pipe was turned 90°. Because the coefficient of friction between the two rubber arms and the inner In Figure the case compared pattern I, the body magnetic actuatoractuator in the pipe was 14.ofInpattern the caseIIof pattern II with compared with pattern I, of thethe body of the magnetic in the wall of the pipe do not change, this actuator can move underwater if all vibration components are pipepacking was 90°. Because the coefficient of friction between the two rubber arms and the inner turned 90˝ . turned Because the coefficient of friction between the two rubber arms and the inner wall possibility. In this case, it is expected that the speed of the actuator hardly changes as of of the pipe do air notwhen change, this actuator can move all vibration components are thewall pipe do not this actuator can move underwater all vibration components packing compared change, with the same electric current was underwater inputifinto theif electromagnet of the are vibration packing possibility. In this case, it is expected that the speed of the actuator hardly changes as possibility. In this case, it is expected that the speed the actuator hardly changes as compared with components. However, the actuator cannot move inofoil because the coefficient of friction is very small. compared with air when the same electric current was input into the electromagnet of the vibration In the have tocurrent discusswas the frictional force to realize movementofinthe oil. vibration components. air when thefuture, samewe electric input into the electromagnet

components. However, the actuator cannot move in oilcoefficient because the friction is very small. However, the actuator cannot move in oil because the ofcoefficient friction is of very small. In the future, In the future, we have to discuss the frictional force to realize movement in oil. we have to discuss the frictional force to realize movement in oil.


9 of 11

Table 2 shows the average speed for the two movement patterns for the actuator measured in Actuators 5, 19 the2016, horizontal and vertical directions. The experimental results show that for both patterns, the9 of 11

average speed of the magnetic actuator exceeded 60 mm/s.


9 of 11

Table 2 shows the average speed for the two movement patterns for the actuator measured in the horizontal and vertical directions. The experimental results show that for both patterns, the average speed of the magnetic actuator exceeded 60 mm/s.

(a)

(b)

Figure 14. Two moving patterns in the curved pipe. (a) Pattern I; (b) Pattern II.

Figure 14. Two moving patterns in the curved pipe. (a) Pattern I; (b) Pattern II. Table 2. Average speed for two patterns of movement.

Table 2 shows the average speed for the two movement patterns for the actuator measured in the Upward Updown Left Right horizontal and vertical directions. The experimental results show that for both patterns, the average Pattern I (mm/s) 43.8 88.8 63.5 70.8 speed of the magnetic actuator exceeded 60 mm/s.

26 mm

Pattern II (mm/s) 42.2 67.5 57.3 53.1 (a) (b) Table 2. Average speed for two patterns of movement. Figure 15 shows a schematic of a complex pipe with a T-junction, an inner diameter of 26 mm, Figure 14. Two moving patterns in the curved pipe. (a) Pattern I; (b) Pattern II. and steps of 1 mm. As mentioned above, compound material A only opened in the pipe. Before the Upward Updown Left Right actuator moves into the T-junction, the actuator must rotated the pipe by controlling the phase Table 2. Average speed for twobe patterns of in movement. Patternbetween I (mm/s) 43.8 88.8 63.5 in the initial 70.8 difference the three vibration components and it must be placed condition, as Upward Updown Pattern II (mm/s) 57.3 53.1 shown in Figure 15. The supply42.2 of direct current 67.5 into SMA coil C Left attached onRight iron pole 1 was first I (mm/s) 88.8 due to63.5 70.8 stopped. After a Pattern few seconds, compound43.8 material C opened the elastic restoring force of the Pattern II (mm/s) 42.2 67.5 57.3 53.1 material15 itself. Accordingly, the tip compound material contact with the inner wall of Figure shows a schematic of aofcomplex pipe withCa made T-junction, an inner diameter ofthe 26 mm, pipe. In this initial condition, vibration component 1 (compound material A) was driven, and a and stepsFigure of 1 mm. As mentioned above, compound material A only opened in the pipe. Before the 15 shows a schematic of a complex a T-junction, diameterpoint of 26 mm, rotational torque acted on the main body ofpipe the with actuator, because an theinner supporting was actuator into theAs T-junction, actuator mustmaterial be rotated in the pipe in by controlling thethe phase andmoves steps of 1 mm. mentionedthe above, compound A only opened Before compound material C. Consequently, the actuator can turn in the left direction in the the pipe. T-junction pipe difference between the three vibration components and it must be placed in the initial condition, actuator moves into the T-junction, the actuator must be rotated in the pipe by controlling the phase as shown in Figure 15. By changing the initial condition due to the rotation of the actuator as as shown in Figure 15. The supply of into coil attached ironcondition, pole 1 was difference between theactuator three vibration andSMA it must beCplaced in theon initial as first mentioned above, this candirect turncomponents incurrent the right direction. shown in Figure The supply of directmaterial current into SMA coil C attached on iron pole 1 was first stopped. After a few 15. seconds, compound C opened due to the elastic restoring force of the stopped. a few seconds, material C opened due to thecontact elastic restoring of the material itself.After Accordingly, thecompound tip of compound material C made with theforce inner wall of material itself. Accordingly, the vibration tip of compound material C made contact with the of theand a the pipe. In this initial condition, component 1 (compound material A)inner waswall driven, pipe. In this initial condition, vibration component 1 (compound material A) was driven, and a rotational torque acted on the main body of the actuator, because the supporting point was compound rotational torque acted on the main body of the actuator, because the supporting point was material C. Consequently, the actuator can turn in the left direction in the T-junction pipe as shown in compound material C. Consequently, the actuator can turn in the left direction in the T-junction pipe Supporting Figure By changing condition due tocondition the rotation asthe mentioned above, as15. shown in Figure the 15. initial By changing the initial due of to the the actuator rotation of actuator as point this actuator can turn in the right direction. mentioned above, this actuator can turn in the right direction.

26 mm

Initial condition

Side view Supporting point Figure 15. Actuator moving in a T-junction.Initial

condition

Side view

Figure 15. Actuator moving in a T-junction.

Figure 15. Actuator moving in a T-junction.

Actuators 2016, 5, 19 Actuators 2016, 5, 19

10 of 11 10 of 11

As shown shown in in Figure Figure 16, 16, the the movement movement speed speed in in the the horizontal horizontal and and vertical vertical directions directions in in the the pipe pipe As with a T-junction was measured when the input current to vibration components 1 and 2 was 0.3 A. with a was measured when the input current to vibration components 1 and 2 was 0.3 A. Since the the distance distance between between the the Table 3 shows the average speeds for the eight movement patterns. Since center of vibration component 1 or 2 and the center of iron pole 1 or 2 was 8 mm, the magnetic actuator center of vibration and the center of iron pole 1 or 2 was 8 mm, the magnetic actuator could turn turn smoothly smoothly in the small complex pipe. could

Up B Right A

Left A

Down A

Right B

Left B

Up A

Down B

(a)

(b)

(c)

(d)

Figure Figure 16. 16. Eight Eight movement movement patterns patterns of of the the actuator. actuator. (a) (a)Horizontal Horizontaldirection; direction;(b) (b)Vertical Vertical direction; direction; (c) Horizontal direction; (d) Vertical direction. (c) Horizontal direction; (d) Vertical direction. Table Table 3. 3. Average Average speeds speeds for for the the eight eight patterns patterns considered. considered.

Left A Left ARight A Right A Left B Left B Right BRight B

Speed (mm/s) 32.97 32.97 33.71 33.71 25.2 25.2 27.27 27.27

Speed (mm/s)

Speed (mm/s) Up A 17.08 Speed (mm/s) 17.08 Down Up A A 29.41 Down A 29.41 Up B 20.13 Up B 20.13 DownDown B B 38.4 38.4

6. Conclusions 6. Conclusions A new type of magnetic actuator is proposed that is capable of locomotion in a complex pipe A new type of magnetic actuator is proposed that is capable of locomotion in a complex pipe with with an inner diameter of 25 mm. Due to the desire to increase the turning moment in a T-junction an inner diameter of 25 mm. Due to the desire to increase the turning moment in a T-junction pipe, pipe, vibration components were attached off-center on an acrylic plate with an eccentricity of vibration components were attached off-center on an acrylic plate with an eccentricity of 2 mm. The 2 mm. The experimental results show that the magnetic actuator was able to move at 40.6 mm/s while experimental results show that the magnetic actuator was able to move at 40.6 mm/s while pulling a pulling a load mass of 20 g in a pipe with an inner diameter of 26 mm. In addition, by using the three load mass of 20 g in a pipe with an inner diameter of 26 mm. In addition, by using the three vibration vibration components of the magnetic actuator, the magnetic actuator was able to turn in a small components of the magnetic actuator, the magnetic actuator was able to turn in a small complex pipe complex pipe with a T-junction. If a micro-camera with an outer diameter of 8 mm and a length of 10 with a T-junction. If a micro-camera with an outer diameter of 8 mm and a length of 10 mm is available mm is available in the future, inspection of a small complex pipe can be enabled. in the future, inspection of a small complex pipe can be enabled. Author Contributions: Hiroyuki Yaguchi initiated and supervised the development of the magnetic actuator Author Contributions: HiroyukiKamata Yaguchiand initiated and supervised the development of the magnetic and and wrote the paper, Kazushige Hiroshi Sugawara performed the design, assembly andactuator integration wrote the paper, Kazushige Kamata and Hiroshi Sugawara performed the design, assembly and integration of of the prototype. the prototype. Conflicts Interest: The no conflict conflict of of interest. interest. Conflicts of of Interest: The authors authors declare declare no

References References 1. 1. 2. 2. 3. 3. 4. 4. 5.

Kurosumi, Defect Identification Identification of Kurosumi, Y.; Y.; Yoshiara, Yoshiara, T. T. Defect of Carbon Carbon Steel Steel Testpieces Testpieces by by Using Using Pattern Pattern Recognition Recognition through Ultrasonic Inspection. INSS J. 1995, 2, 127–137. through Ultrasonic Inspection. INSS J. 1995, 2, 127–137. Kalyanasundram, P.High HighSensitivity Sensitivity Detection Classification of Defects in Austenitic Weldments Kalyanasundram, P. Detection andand Classification of Defects in Austenitic Weldments Using Using Cluster Analysis and Pattern Recognition. J. Nondestrct. Test. 1991, 33, 6. Cluster Analysis and Pattern Recognition. J. Nondestrct. Test. 1991, 33, 6. Junji, Junji, K.; K.; Manabu, Manabu,O.; O.;Hiroshi, Hiroshi,H. H.Multi-Bank Multi-BankMulti-Coil Multi-CoilProbe Probefor forHeat HeatExchanger ExchangerTube TubeEddy EddyCurrent CurrentTest Test using Uniform Eddy Current. Jpn. Soc. Non-Destr. Insp. 2004, 53, 366–372. using Uniform Eddy Current. Jpn. Soc. Non-Destr. Insp. 2004, 53, 366–372. TakagiI, Technologies forfor Thick Metal Structures Institute of Fluid Science. Jpn. TakagiI, T.; T.; Endo, Endo,H. H.Eddy EddyCurrent Current Technologies Thick Metal Structures Institute of Fluid Science. Soc. Non-Destr. Insp. 2014, 6, 10. Jpn. Soc. Non-Destr. Insp. 2014, 6, 10. Saito, H.; Sato, K.; Kudo, K.; Sato, K. Fundamental Study of Mover Travel inside a Small Diameter Pipe. Trans. Japan Soc. Mech. Eng. 2000, 66, 346–353.


5. 6. 7.

8.

9. 10. 11. 12.

13. 14. 15. 16. 17. 18. 19. 20.

11 of 11

Saito, H.; Sato, K.; Kudo, K.; Sato, K. Fundamental Study of Mover Travel inside a Small Diameter Pipe. Trans. Japan Soc. Mech. Eng. 2000, 66, 346–353. [CrossRef] Fujita, J.; Shiraogawa, Y.; Yamamoto, S.; Kato, T. Study of Mobile Mechanism with Elastic Fibers by Using Vibration. Trans. Japan Soc. Mech. Eng. 2004, 70, 22–26. [CrossRef] Kwon, J.; Park, S.; Kim, B.; Park, J. Bio-Material Property Measurement System for Locomotive Mechanism in Gastro-Intestinal Tract. In Proceedings of the IEEE International Conference on Robotics and Automation (ICRA), Barcelona, Spain, 18–22 April 2005; pp. 1315–1320. Reynaerts, D.; Peilw, J.; Van Brussel, H. Design of a Shape Memory Actuated Gastrointestinal Intervention System. In Proceedings of the 6th International Symposium on Micro Machine and Human Science, Leuven, Belgium, 8–11 September 1996. Kim, J.; Kim, M.J.; Yoo, J.; Kim, S.J. Novel Motion Modes for 2-D Locomotion of a Microrobot. IEEE Trans. Magn. 2014, 50. [CrossRef] Choi, K.; Jang, G.; Jeon, S.; Nam, J. Capsule-Type Magnetic Microrobot Actuated by an External Magnetic Field for Selective Drug Delivery in Human Blood Vessels. IEEE Trans. Magn. 2014, 50. [CrossRef] Kim, S.H.; Shin, J.W.; Ishiyama, K. Multiscale Magnetic Spiral-Type Machines for Fluid Manipulation. IEEE Trans. Magn. 2014, 50. [CrossRef] Guo, S.; Sawamoto, J.; Pan, Q. A Novel Type of Microrobot for Biomedical Application. In Proceedings of the 2005 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS2005), Edmonton, AB, Canada, 2–6 August 2005; pp. 2265–2270. Miyagawa, T.; Iwatski, N. Moving Characteristics in Bent Pipes of In-Pipe Mobile Robot with Wheel Drive Mechanism using Planetary Gear Drive. J. Jpn. Soc. Precis. Eng. 2008, 74, 1346–1350. [CrossRef] Guo, J.; Guo, S.; Wei, X.; Wang, Y. Development of Wireless Endoscope with Symmetrical Motion Characteristics. Int. J. Adv. Robot. Syst. 2014, 11. [CrossRef] Yaguchi, H.; Sato, N. Globular Magnetic Actuator Capable of Freely Movement in a Complex Pipe. IEEE Trans. Magn. 2010, 46, 1350–1355. [CrossRef] Yaguchi, H.; Sato, N.; Shikoda, A. Magnetic Actuator Group of Globular Type Capable of Free Movement in a Complex Pipe. IEEE Trans. Magn. 2011, 47, 4159–4162. [CrossRef] Yaguchi, H.; Kamata, K. In-piping Magnetic Actuator Capable of Inspection in a Thin Complex Pipe. Mech. Eng. Res. 2012, 2, 1–9. [CrossRef] Yaguchi, H.; Sasaki, K. New Type of Magnetic Actuator System for Inspection in a Complex Pipe. IEEE Trans. Magn. 2013, 47, 4159–4162. [CrossRef] Yaguchi, H. Magnetic Actuator Capable of Inspection in a Complex Pipe by Phase Control of Multiple Electromagnetic Vibration Components. IEEE Trans. Magn. 2015, 51. [CrossRef] Wang, Q.; Li, J.; Liu, Y.F.; Qian, Z.Q.; Cao, L.; Zhang, W.J. A Systematic and Rational Design Approach for Compliant Amplification Mechanisms. In Proceedings of the IEEE 10th Conference on Industrial Electronics and Applications, Auckland, New Zealand, 15–17 June 2015; pp. 74–78. © 2016 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).