Traversing Assist System for Tracked Vehicles on Rough Terrain Based on Continuous Three-Dimensional Terrain-Scanning

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,, Traversing Assist System for Tracked Vehicles on Rough Terrain Based on Continuous Three-Dimensional Terrain-Scanning Yoshito OKADA, Keiji NAGATANI and Kazuya YOSHIDA Department of Aerospace

1 ,, Traversing Assist System for Tracked Vehicles on Rough Terrain Based on Continuous Three-Dimensional Terrain-Scanning Yoshito OKADA, Keiji NAGATANI and Kazuya YOSHIDA Department of Aerospace Engineering, Tohoku University Aramaki Aza Aoba, Aoba-ku, Sendai, Japan Tracked vehicles are frequently used as Search and Rescue robots. To enhance their traversability on rough terrain, some of them equip active flippers. However, such flippers also increase the operator s workload in case of tele-operation. To eliminate this problem, we have developed a traversing assist system using an autonomous controller for flippers based on continuous three-dimensional terrain-scanning. In our system, realtime terrain slices are obtained using 3 laser range sensors and integrated to generate terrain surface information. In this paper, we introduce the autonomous controller for flippers and validate the traversing assist system through experimental results on actual rough terrain. Key Words : Tracked vehicle, Autonomous operation, Range sensing (1) (2)(3) Kenaf 1 RoboCupRescue (4) Best-mobility award yoshito@astro.mech.tohoku.ac.jp Fig. 1 Tracked vehicle testbed Kenaf equipped with 3 laser range sensors Table 1 Basic specifications of Kenaf Dimensions W400 [mm] L500 [mm] Weight 20 [kg] Length of flippers 235 [mm] Degrees of freedom 6 (2 main tracks and 4 flippers)

2 Fig. 2 A comparison of the proposed controller with the previous one (5) Kenaf Kenaf Kenaf Kenaf Kenaf (6) 90[cm] 2. (5) (5) (1) (2) (3) (1) (2) (3) 3. 2

3 q {p,q} p global = q p local q 1 + p (1) p =[0,x pos,y pos,z pos ] T (2) q =[cos(θ rot /2),x rot sin(θ rot /2), y rot sin(θ rot /2),z rot sin(θ rot /2)] T (3) Fig. 3 Algorithm for autonomous controller for flippers (1) (2) (3) (4) (5) (6) 3 3 x z y (x pos,y pos,z pos ) T p (x rot,y rot,z rot ) T θ rot 3 4 U p q S = {U, p,q} l,r, f n n S l,n,s r,n S f,n S n S n = {S l,n,s r,n,s f,m,s f,m+1,...,s f,n } (4) n 1 m = min{i Z j=i p j+1 p j < L threshold } (5) L threshold S n t t p p = p cur + q cur [0,V cur t,0,0] T q 1 cur (6) V cur {p,q} u {p,q cur } u = q 1 cur (q u q 1 + p p ) q cur (7) S = {U, p,q} S n U n U n = {U l,n,u r,n,u f,m,u f,m+1,...,u f,n} (8) U n U target U target = {u U n L max /2 x L max /2 and W/2 y W/2} (9)

4 L max W 3 5 (5) (5) 2 U target q target U target U target U target u U target,u U target u U target u = q target u qtarget 1 (10) u = u [0,0,0,max(z U target)] (11) U target (1) 3 6 U target u ({U l,n,u r,n} U target) Kenaf (2) 3 7 NE (7) NE Kenaf NE Kenaf 3 8 (3) 1a. NE 1b. NE PID 3 4 t θ re f ω max ω max = C θ cur θ re f (12) t θ cur C 4. 3 Kenaf 4 5 Kenaf L threshold 100[cm]

5 pitch angle [deg] time [sec] Fig. 4 A bump comprising concrete blocks Fig. 6 change in pitch angle on the bump Fig. 5 A complex field comprising randomly positioned concrete blocks t 0.5[sec] Kenaf 10[cm] C (5) Kenaf Fig. 7 snapshots while traversing the bump Kenaf 10[cm/s] [sec] 23[sec]

pitch angle [deg] 25 20 15 10 5 0-5 -10-15 -20-25 Fig. 8 traversing assist manual 0 0.2 0.4 0.6 0.

6 pitch angle [deg] Fig. 8 traversing assist manual elapsed/total [-] change in pitch angle on the complex field roll angle [deg] Fig. 9 traversing assist manual elapsed/total [-] change in roll angle on the complex field Kenaf NEDO Fig. 10 snapshots while traversing the complex field (1) S.Tadokoro, F.Matsuno and A.Jacoff, Special Issues on Rescue Robotics, Advanced Robotics Vol.19 No.3, No.8, (2004) (2) H.Miyanaka, N.Wada, T.Kamegawa, N.Sato, S.Tsukui, H.Igarashi and F.Matsuno, Development of an unit type robot KOHGA2 with stuck avoidance ability, the IEEE International Conference on Robotics and Automation, (2007), pp (3) Y.Tanaka, M.Arai, S.Hirose and S.Tsukui, Development of Souryu-V with Mono-Tread-Crawlers and Elastic- Rods Joint, the IEEE International Workshop on Safety, Security, and Rescue Robotics, (2006) (4) A.Jacoff, E.Messina, B.A.Weiss, S.Tadokoro and Y.Nakagawa, Test Arenas and Performance Metrics for Urban Search and Rescue Robots, the IEEE/RSJ International Conference on Intelligent Robots and Systems, (2003), pp (5) Y.Okada, K.Nagatani and K.Yoshida, Semi-Autonomous Operation of Tracked Vehicles on Rough Terrain using Autonomous Control of Active Flippers, the IEEE/RSJ International Conference on Intelligent Robots and Systems, (2009) (6) K.Nagatani, N.Tokunaga, Y.Okada and K.Yoshida, Continuous Acquisition of Three-dimensional Environment Information for Tracked Vehicles on Uneven Terrain, the IEEE International Workshop on Safety, Security, and Rescue Robotics, (2008), pp (7) S.Hirose, H.Tsukagoshi and K.Yoneda, Normalized Energy Stability Margin: Generalized Stability Criterion for Walking Vehicles, the International Conference on Climbing and Walking Robots, (1998), pp.71 76

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