A CONCEPTUAL WHEELED ROBOT FOR IN-PIPE INSPECTION Ioan Dooftei, Mihaita Hoodinca, Emmanuel Mignon Univesité Libe de Buxelles Active Stuctues Laboatoy 50, Av. F.D.Roosevelt, B-1050, Bussels, Belgium. Email: iodooft@ulb.ac.be Abstact: This pape descibes a new concept of mobile obot cuently being developed at ULB as a conceptual vehicle fo in-pipe inspection. A single DC moto located on the cental axis actuates the obot, which consists of two bodies. The otating body has thee double wheels which make an angle of 10 to achieve an helical tajectoy when the moto otates; the body fixed to the stato also possesses thee double wheels oiented paallel to the tube axis, to allow only axial displacements. All the wheels ae mounted on spings in ode to adapt to changing diametes allow the motion into cuve pipes and compensate fo iegulaities on the inne suface of the tube. The obot can move in hoizontal, vetical as well as cuved pipe geometies. Keywods: wheeled obot, in-pipe inspection. 1 Intoduction An impotant application fo obotic systems is the aea of pipe inspection (in the oil, chemical and nuclea industy, the public wate systems, and possibly futue space systems) [1-5]. In this context and on the basis of its expeience in mobile obots the Active Stuctues Laboatoy of Univesité Libe de Buxelles, has developed a new concept of wheeled obot fo in-pipe inspection, called HELI-PIPE. The obot has a numbe of advantages: The vehicle has a vey simple kinematics and uses a single moto. Low enegy consumption, thanks to the simple kinematics. It can move in hoizontal, vetical as well as cuved pipe geometies. The obot can adapt to changing diametes and to small obstacles on the inne suface of the tube. The obot can easily be potected against humid and dity envionments. It can be used fo weld inspection, fault detection, cleaning and epaiing of intenal pipe sufaces, etc. In this pape, a stuctual synthesis, oveall achitectue and kinematics aspects of the HELI-PIPE obot ae pesented. 2 Stuctual Synthesis We will conside fist a plan mechanism with linea joints, shown in figue 1. The joint C 2 is a passive one Figue 1. Plan mechanism with linea joints and it was intoduced just to incease the igidity of the mechanism. It is easy to demonstate that the mechanism has a single degee of feedom (one diving link) (6). If we assume that 1 is the dive, the diven link 2 will have a vetical tanslation along the fame 0, consideed fixed. Figue 2. An equivalent plan mechanism of the obot The elative movements of all the joints, movements descibed by the vectos S, S, S, ae dependent by the elation: A B C
2 2 ( S ) ( S ) = ( S ) 2 C + (1) A B The value of the angle α should satisfy the condition of the auto-blocking phenomenon. In ode to obtain an equivalent plan mechanism fo ou obot, we will develop the mechanism fom figue 1. So, if we intoduce the thee new passive joints B, B, ou mechanism will look as the one 2 3 B4 shown in figue 2. All the guide bas 2 of the joints Bi make the same angle α with the hoizontal guide ba of the joint A. In ode to pepae the next step of the synthesis, we assume that the distance between the 2 cente of two neighbou joints B i is π R, whee 3 R is the intenal adius of the pipe. Also, the distance between the cente of the joints A and B i, along an axis pependicula on the plane of the joints B i, is R (as shown in figue 2.b). Figue 4. Spatial mechanism with otay joints If the plan of the joints B i is olled on a cylinde of adius R, aound the axis A A, as well as the joints B 1, B 4 espectively the axes 1, 2 ae supeposed, will esult a spatial mechanism (see figue 3). Figue 3. Spatial mechanism with linea joints The guide bas of the equidistant joints B i ae some helices, disposed (with the same angle α ) on the extenal suface of a cylinde with a adius R. The linea joints A and C ae tansfomed in a spatial (otay linea) joint A C, disposed on the cental axis of the mechanism. Figue 5. Final mechanism of the obot, without univesal joint: in staight pipe; in cuved pipe
In ode to educe the fiction of the joints B i, thee wheels will eplace these linea joints (as shown in figue 4). Also, the linea movement of the joint A C can be eplaced by using thee equidistant wheels, which make contact with the intenal suface of the pipe (see figue 5). In fact, this is the mechanism of the HELI PIPE obot. mounted on spings, the mechanism can adapt to changing diametes allow the motion into cuve pipes and compensate fo iegulaities on the inne suface of the tube. The wheels of the otating body make an angle α to achieve a helical tajectoy when the link 1 otates (see figues 3-4). In fact, the thee helical tajectoies of these wheels look like a scew with thee beginnings. In this case, the movement of the mechanism into cuved pipes geometies is possible only if exist a small axial slippage of the diving wheels. In ode to decease the adius of cuvatue of the pipe geometies and the slippage of the wheels, an univesal joint can connect the two bodies of the obot (figue 6). In this case, in ode to avoid the tuning ove of the bodies, it is necessay to use double wheels (figue 6.b). 3 Oveall Achitectue, Kinematics Figue 6. Final mechanism, with univesal joint: staight, cuved. Many pipes o duct systems have junctions, cones, steps and big changes in thei coss section. The obot, which was built on the basis of mechanism shown in figue 4, is not able to move in complex pipe shapes but it can move in hoizontal, vetical as well as cuved pipe geometies with a elatively wide adius of cuvatue (see figue 5.b). Because all the wheels ae HELI-PIPE (figue 7) is a 160 mm long wheeled obot, with a diamete of 180 mm, fo in-pipe inspection applications. Its kinematics is based on the mechanism shown in figue 5. The obot is actuated by a single DC moto located on the cental axis and it consists of two bodies, one mounted on the shaft of the moto, one fixed to its stato. The otating body has thee double wheels which make an angle of 10 to achieve an helical tajectoy when the moto otates; the body fixed to the stato also possesses thee double wheels oiented paallel to the tube axis, to allow only axial displacements. All the wheels ae mounted on spings in ode to adapt to changing diametes allow the motion into cuved pipes and compensate fo iegulaities on the inne suface of the tube. The obot can move in hoizontal, vetical as well as cuved pipe geometies with a elatively wide adius of cuvatue. The pesent design is made fo tubes of diametes in the ange of 160-180 mm, but it can be easily adapted fo any size of pipes above 50 mm. Fo a complete otation of the moto s shaft, we can wite (see figues 1-4): d = p = 2 π R tanα (2) whee: d is the axial displacement of the obot; p is the step of the helical tajectoy of the diving wheels; α is the angle of these wheels; R is the intenal adius of the tube.
4 Conclusions A new concept of mobile obot has been developed at ULB, as a vehicle fo in-pipe inspection. The vehicle has a vey simple kinematics thanks to a single DC moto (located on the cental axis), that actuates the obot. It consists of two bodies; one mounted on the shaft of the moto, one fixed to its stato. Each body has thee double wheels mounted on spings in ode to adapt to changing diametes allow the motion into cuve pipes and compensate fo iegulaities on the inne suface of the tube. The wheels of the otating body make an angle of 10 to achieve a helical tajectoy when the moto otates. The obot can move in hoizontal, vetical as well as cuved pipe geometies with a elatively wide adius of cuvatue. Refeences Figue 7. HELI-PIPE obot: final design; geneal view Fo a otation with an angle ϕ of the otating body, the axial displacement of the obot is: d ϕ = ϕ R tanα ϕ = ω t whee: ω = 2 π n is the angula speed of the otating body; t is the time; n is the speed of the moto. In these conditions, the elation (3) becomes: (3) [1] K. Taguchi, N. Kawaazaki, Development of In-Pipe Locomotion Robot, Poceedings of the 1991 IEEE, pp. 297-302; [2] Th. Robfman, F. Pfeiffe, Contol an Design of a Pipe Cawling Robot, IFAC 96, Poceedings of the 13 th Wold Conges, June 30 July 5, 1996, San Fancisco, USA, pp. 465-470; [3] K. Suzumoi, K. Hoi, T. Miyagawa, A Diect-Dive Pneumatic Stepping Moto fo Robots: Designs fo Pipe-Inspection Micoobots and fo Human-Cae Robots, Poceedings of the 1998 IEEE, May 1998, Leuven, Belgium, pp. 3047-3052; [4] T. Miyagawa, K. Suzumoi, M. Kimua, Y. Hasegawa, Development of Mico Inspection Robot fo Small Piping, JRSJ, Vol. 17, No. 3, pp. 79-85; [5] W. Neubaue, A Spide-Like Robot that Climbs Vetically in Ducts o Pipes, IROS 94; [6] H. H. Mabie, Ch. F. Reinholtz, Mechanismes and Dynamics of Machiney, John Wiley & Sons, Inc., New Yok, 1987. d ϕ = 2 π R n t tanα (4) The axial speed of the obot will be: = 2 π R n tan α = p n (5) S C
SPIDY - A MOTORLESS MICRO WALKING ROBOT Ioan Dooftei, Jean-Maie Cloquet Univesité Libe de Buxelles Active Stuctues Laboatoy 50, Av. F.D.Roosevelt, B-1050, Bussels, Belgium. Email: iodooft@ulb.ac.be Abstact: This pape descibes a lightweight, six-legged mico-walking obot cuently being developed at ULB. The obot has six legs with two active degees of feedom pe leg and equies no motos fo its movement. The movement is achieved by heating small memoy alloy wies (muscle wies) of 50 µ m diamete, acting as tendons fo each leg of the obot. Elastic ubbe wies ae used to etun the links of the leg to the initial position, when the muscle wies ae no moe poweed. All the legs ae mounted diectly on the electonic boad without any othe fames. The contol boad of the mico walking vehicle is vey simple and it is based on an 8-bit mico-contolle (PIC16F84). Thanks to this, the obot can walk fowad/backwad and tun left/ight. Keywods: walking obot, muscle wies, SMA. 1 Intoduction Supeio teain adaptability has made legged obots candidate fo exploation and inspection semiautonomous vehicle [1], [2]. The legged vehicles offe attactive capabilities in tems of agility and obstacle avoidance. Also, the use of legs is convenient fo locomotion on soft gound whee the pefomance of wheels and tacks ae consideably educed, paticulaly in low gavity; indeed the net thust capability of a leg is inceased by the gound compaction while that of a wheel is educed. As we can see fom the technical liteatue, walking obots with one, two, thee, fou, six o eight legs have been built. The numbe of legs affects some chaacteistics of the walking obots, such as: the stability, the efficiency, the possibility of walking with fewe legs when some of these ae out of ode (edundancy), the quality of the obot contol, the pice, the weight, the gait, etc. (3). A wide vaiety of pototypes have been constucted with vaious sizes and achitectues [4], [5]. Shape Memoy Alloys can exhibit lage changes in shape when heated and cooled (capable of lifting thousands of times thei own weight) and can eplace motos and solenoids fo ceating motion in many devices, even obots [6], [7], [8]. They can be heated diectly with electicity and cab be used to ceate a wide ange of motions, opeating quickly and with pecise contollability. In this context and on the basis of its expeience in walking machines, the Active Stuctues Laboatoy of Univesité Libe de Buxelles has developed a concept of lightweight six-legged mico walking vehicle, called SPIDY. In this pape, some stuctual and kinematics aspects as well as types of gaits implemented on SPIDY obot ae pesented. 2 Oveall Achitectue, Kinematics Six legs offe a good compomise between weight and electomechanical complexity, on one hand, and stability, velocity and the vaiety of gaits, on the othe Fig. 1. Stuctual scheme of GENGHIS obot hand. The kinematic achitectue of the pesent vehicle was used oiginally on a mico walking machine called GENGHIS (figue 1), developed at MIT [8]; a simila achitectue was also used fo one of ou pevious pototypes [9].
SPIDY is a 55 g, 10.5 cm long, 14 cm wide and 6 cm high walking obot. It has six legs with two active degees of feedom pe leg (see figue 2) in ode to minimize its complexity and equies no motos fo its movement. Fig. 3. SPIDY obot: design; geneal view Fig. 2. Kinematics of a leg: stuctue; design The movement of the obot (figue 3) is achieved by heating small shape memoy alloy wies (muscle wies) of 50 µm diamete, which ae attached to each leg of the obot. Elastic ubbe wies ae used to etun the links of the leg to the initial position, when the muscle wies ae no moe poweed. Although the tajectoy can neve be a staight line because of the simple kinematics, the slippage does not cause any paticula mechanical poblem because of the small weight of the vehicle. Thanks to the small diamete of the SMA wies, a cycle time of about 1 sec can be achieved. Each leg has two muscle wies, one fo each d.o.f., and two elastic ubbe wies. As we can see in figue 2.a, one muscle wie otates the joint α in one diection (indicated by the lette a) and one ubbe wie in the opposite diection, indicated by the lette a (when the SMA is not poweed any moe). The same thing will also happen fo the joint β. All the legs ae mounted diectly on the electonic boad without any othe fames (figue 3), in ode to simplify the achitectue of the obot. The otating angles of the links depend of the leg stuctue but also of the value of the wies defomations. So, fo a given leg stuctue, the value of the otating angle depends diectly of the length of
the muscle wie.in ode to incease the lengths of the wies (to incease the stokes of the legs) and to keep small oveall dimensions fo the obot, some pulley wheels ae integated in the stuctue of the leg (see figue 2). 3 Contol The contol boad of the mico walking vehicle (see figue 4) is vey simple and it is based on an 8-bit mico-contolle (PIC16F84). This kind of micocontolle is vey used fo small applications because of a vey good pefomance/cost atio. Moe, it has Flash pogam memoy (this is vey useful fo applications which need to change the pogam many times), numbe of the PIC is limited to 8, only the tipod gait was implemented. 4 Conclusions A mico-walking obot diven by SMA has been developed. The movement of the obot is achieved by heating SMA of 50 µm diamete, which ae attached to each leg of the obot. Elastic ubbe wies ae used to etun the links of the leg to the initial position, when the muscle wies ae no moe poweed. All the legs ae mounted diectly on the electonic boad without any othe fames. The contol boad of the mico walking vehicle is based on an 8-bit mico-contolle (PIC16F84). Refeences [1] MARSNET, Repot on the phase A study, ESA Publication SCI(93)2, Apil 1993; [2] ROSETTA epot, ESA Publication SCI(93)7, Septembe 1993; [3] D. J. Todd, Walking Machines: an Intoduction to Legged Robots, Kogan page, London, 1985; [4] Special Issue on Legged Locomotion, Intenational Jounal Robotics Reseach 9(2), 1990; [5] Robotics in Nuclea Facilities, Special Issue, SMIRT - 11, Tokyo, 1991; Fig. 4. Contol achitectue educes the numbe of extenal components and opeates ove the standad voltage ange. Fo a SMA with 50 µm diamete and a linea esistance of 510 Ω/m, the ecommended cuent is 50 ma. As a function of the type of gait, which will give us the total length of the muscle wie poweed at one moment, we can compute the necessay voltage using the basic equation of electicity (Ohm s Law). The contol boad will be connected to a PC though a seial adio link (opeating ange 10m); the PC acts as Man-Machine Inteface and contols the walking. At this time, it is connected diectly (by an umbilical cable) to a powe supply souce. Thanks to this contol boad, the obot can walk fowad/backwad and tun left/ight. Because the bit [6] R. G. Gilbetson, Muscle Wies Poject Book, 3 d edition, Mondo-tonics, Inc. San Anselmo, USA 1996; [7] J. M. Conad, J. W. Mills, Stiquito - Advanced Expeiments with a Simple and Inexpensive Robot, USA, 1997; [8] J. M. Conad, J. W. Mills, Stiquito fo Beginnes - An Intoduction to Robotics, USA, 1999; [9] R. A. Books, A Robot that Walks; Emegent Behavios fom a Caefully Evolved Netwok, IEEE Intenational Confeence on Robotics and Automation, 1989.