Mobile Robots book 2011 Part 3 potx

A Field Robot with Rotated-claw Wheels 41 retracted inside the wheel body (Now the rotated-claw wheel is the same as conventional circular wheel). It shows that the acceleration varies from -0.13g to 0.13g. Compare Figure 13 with Figure 14, we can see that stability of the rotated-claw wheel under the condition of retracted claws is similar to that of conventional circular wheel. Fig. 12. Plumb direction acceleration curve of Rabbit when the rotated-claw wheels make clockwise rotation on bituminous macadam ground Fig. 13. Plumb direction acceleration curve of Rabbit when the rotated-claw wheels make anticlockwise rotation on bituminous macadam ground Fig. 14. Plumb direction acceleration curve of Rabbit when the rotated-claw wheels rotate with retracted claws on bituminous macadam ground It is obvious that the motion stability under anticlockwise rotation is more stable than that under clockwise rotation. The reason is that the claw can swing into the wheel body under anticlockwise rotation while the hexagon effect causes the bumpiness under clockwise rotation. So the Rabbit should be commanded to move in a backward mode (i.e., all the wheels rotate in anticlockwise direction) on flat hard ground. Mobile Robots - State of the Art in Land, Sea, Air, and Collaborative Missions42 4.2 Performance of climbing obstacles 4.2.1 Dry soil terrain In order to test Rabbit’s motion performance on dry soil terrain with multi-obstacle, we did another experiment as shown in Figure 15. Figure 16 shows the acceleration curve of Rabbit in plumb direction that denotes the acceleration varying from -0.125g to 0.125g. Figure 17 gives the acceleration curve of Rabbit in plumb direction on dry soil when the wheels rotate in clockwise direction. It shows that the acceleration varies from -0.10g to 0.10g. Figure 18 gives the acceleration curve of Rabbit in plumb direction on dry soil when the Rabbit moves under the condition of retracted claws, which shows the acceleration varies from -0.10g to 0.10g. Compare Figure 17 with Figure 18, we can see that stability of the wheel is as good as conventional circular wheel under the condition of retracted claws. It is obvious that the backward mode is smoother than forward mode (i.e., all the wheels rotate in clockwise direction) when Rabbit operates on dry soil. But the two results are approximative. The reason is that the claw can sink into soil and the obstacle-climbing capability is enhanced. So Rabbit should move in a forward mode when operates on dry soil terrain with multi-obstacle. The highest obstacle on dry soil terrain that the robot can climb over is 13cm. The experiments also show that Rabbit can step over the clod or stone whose dimension is equivalent to the diameter of the wheel. Fig. 15. Rabbit moves on dry soil terrain Fig.16. Plumb direction acceleration curve of Rabbit while the robot moves forward on dry soil terrain A Field Robot with Rotated-claw Wheels 43 Fig. 17. Plumb direction acceleration curve of Rabbit while the robot moves backward on dry soil terrain Fig. 18. Plumb direction acceleration curve of Rabbit while wheels rotates under the condition of retracting claws on dry soil terrain 4.2.2 Step terrain When the robot moves on steps terrain, Rabbit should move in a forward mode (i.e., all the wheels rotate in clockwise direction), because the claw can catch step in front of the wheel and help the robot to climb over it easily in the forward mode. Table 1 shows the experimental results in different step height. Step height/cm 2.2 3.9 6.3 8.1 9.0 Result Success Success Success Success Fail Table 1. Experimental results on different height step It is obvious that the rotated-claw wheel can climb over the 8.1cm step that is almost 1.35 times of wheel’s radius as shown in Figure 19. This verifies that the rotated-claw wheel can improve the obstacle-climbing capacity. Fig. 19. Climbing step in a forward mode Mobile Robots - State of the Art in Land, Sea, Air, and Collaborative Missions44 4.2.3 Slope terrain In order to test Rabbit’s motion performance on slope terrain, we did other experiments as shown in Figure 20, in which the Rabbit climbs over slope terrain in a forward mode. Fig. 20. Rabbit climbs over slope terrain in a forward mode Figure 21 and Figure 22 show the angle curve when Rabbit climbs slope terrain in forward mode and backward mode respectively. We can see that Rabbit can climb a slope up to 40° in the forward mode, in contrast, Rabbit is able to climb a slope just up to 31° in backward mode. Fig. 21. Angle curve when Rabbit climbs slope terrain in forward mode Fig. 22. Angle curve when Rabbit climbs slope terrain in backward mode Comparing Figure 21 and Figure 22, the rotated-claw wheel increases the climbing slop angle up to 9 degree. The reason is that the claw can sink into soil in motion, which enhances physical attraction between the wheel and ground. So Rabbit should move in a forward mode when it moves on slope terrain. A Field Robot with Rotated-claw Wheels 45 4.2.4 Lunar soil simulation In order to adapt to the utilization in planetary, we did experiments on simulated terrain of lunar soil whose material is pozzuolana. The lunar soil is loaded in a trough which has dimensions of 300cm×80cm×60cm as shown in Figure 23. Void ratio (It is defined as the ratio of the volume of all the pores in a material to the volume of all the grain) of the lunar soil is approximately from 0.8 to 1.0, and density of the grain is 2.77g/cm3. Fig. 23. Trough for lunar soil simulation We tested Rabbit’s motion performance on rough terrain and multi-obstacle terrain made up of lunar soil as shown in Figure 24 and Figure 25. The result shows that Rabbit can move freely on simulated lunar soil. Fig. 24. Experiment on rough terrain Mobile Robots - State of the Art in Land, Sea, Air, and Collaborative Missions46 Fig. 25. Experiment on multi-obstacle terrain In addition, we tested Rabbit’s horizontal pulling capacity on simulated lunar soil in both forward and backward modes (Figure 26). The experimental results show that Rabbit can generate maximum pulling forces of 26.5N in forward mode, and 25.1N in backward mode. Fig. 26. Rabbit’s horizontal pull testing 5. Performance comparison According to the available data from literature, we compare the performance of Rabbit with MFEX and Spirit robots. MFEX (Microrover Flight Experiment) was a small rover designed by JPL (Jet Propulsion Laboratory) in 1990s. It was launched to Mars in December 1996 [9]. Spirit is one of the latest Mars rovers designed by JPL. It landed on Mars on January 4, 2004 [10], and finished exploration mission with flying colors in the following years (and still alive). Table 2 lists the data comparison among Rabbit, MFEX, and Spirit. From the table, we can see that maximum slope the Rabbit can climb is larger than that of the other two rovers although Rabbit only equipped with 4 rotated-claw wheels (2 wheels less than the other rovers). In addition, Rabbit can climb over step which is higher than the radius of wheel. Robot name Rabbit MFEX Spirit Mass 10.5Kg 9Kg 176.5Kg Dimensions 57 cm×43 cm×30.9cm 63 cm×48 cm×28cm 140 cm×120 cm×150cm Chassis type Body mounted to rocker through a differential Body mounted to rocker through a differential Body mounted to rocker through a differential A Field Robot with Rotated-claw Wheels 47 Suspension system Springless suspension Springless suspension Rocker-bogie suspension Locomotion system 4 wheels (four steerable) 6 wheels (outer four steerable) 6 wheels (outer four steerable) Maximum speed 0.153m/s 0.02m/s 0.046m/s Operational range 1Km 10m 1Km Layout of wheels Claw-wheel with 120 mm diameter 60 mm width wheels with 130 mm diameter 60 mm width 250 mm diameter Motion control processors One 2407A DSP One Intel 80C85 Max. step height 13cm (Can climb over the step whose height is 1.35 times higher than the radius of the wheel) Less than 6.5cm Less than 12.5cm Maximum slope 40 ° in forward mode, 31 ° in back mode (in soft soil) 32 ° (dry sand) 17 ° (lunar soil simulant) 16 ° at least 30 ° in the nature of the Mars soil and terrain Table 2. Performance comparison of Rabbit, MFEX, and Spirit 6. Conclusion In this paper, we introduce a field robot using the rotated-claw wheel that has strong capacity of climbing obstacles. The experimental results demonstrate that Rabbit can move in different terrain smoothly and climb over step of 8.1cm and slop of 40°. The Rabbit can adopt different moving modes on different terrains. (1) Rabbit should move in backward mode on flat hard ground. (2) Rabbit should move in forward mode on rough, slop, and step terrains. Because the rotated-claw wheel overcomes the disadvantages of conventional mobile robot wheels, it provides a better solution for field and planetary robots. 7. Acknowledgment We thank Wen Li, Gang Sun, and Peng Sun of Beihang University for their valuable help in the experiments of lunar soil simulation. 8. References Cuilan Li; Peisun Ma; Xueguan Gao & Zhikui Cao. (2005). A new six-wheel lunar robot for uneven surface. Drive System Technique, Vol. 19, No. 1, (Mar. 2005) page numbers(9-13), 1006-8244 (in Chinese) Alessio Salemo; Svetlana Ostrovskaya & Jorge Angeles. (2002). The Development of Quasiholonomic Wheeled Robots, Proceedings of the 2002 IEEE international Conference on Robotics and Automation, Vol.4 , pp. 3514 – 3520, Washington, DC, May. 2002. Mobile Robots - State of the Art in Land, Sea, Air, and Collaborative Missions48 Randel A. Lindemann; Donald B. Bickler; Briand. Harrington; Gary M. Ortiz & Christopher J. Voorhees. (2006). Mars exploration rover mobility development. Robotics & Automation Magazine, IEEE, Vol. 13, No. 2, (Jun. 2006) page numbers (19-26), 1070- 9932. Takashi Kubota; Yoji Kuroda; Yasuharu Kunii & Ichiro Nakatani. (2003). Small, light-weight rover Micro5 for lunar exploration. Acta Astronautica, Vol. 52, No. 2-6, (Jan Mar. 2003) page numbers (447-453), 0094-5765. Fanghu Liu; Jianping Chen; Peisun Ma & Zhikui Cao. (2002). RESEARCH STATUS AND DEVELOPMENT TREND TOWARDS PLANETARY EXPLORATION ROBOTS. Robot, Vol. 24, No. 3, (May. 2002) page numbers (268-275), 1002-0446. (in Chinese) Zongquan Deng; Haibo Gao; Ming Hu & Shaochun Wang. (2003). Design of lunar rover with planetary wheel for surmount obstacle. Journal of Harbin Institute of Technology, Vol. 35, No. 2, (Feb. 2003) page numbers (203-213), 0367-6234. (in Chinese) Zongquan Deng; Haibo Gao; Shaochun Wang & Ming Hu. (2004). Analysis of climbing obstacle capability of lunar rover with planetary wheel. Journal of Beijing University of Aeronautics and Astronautics, Vol. 30, No. 13, (Mar. 2004) page numbers (197-201), 1001-5965. (in Chinese) Ronggang Yue; Shaoping Wang; Zongxia Jiao & Rongjie Kang. (2007). Design and performance simulation of a new type wheel with claws. Journal of Beijing University of Aeronautics and Astronautics, Vol. 33, No. 12, (Dec. 2007) page numbers (1408-1411), 1001-5965. (in Chinese) K. Schilling & C. Jungius. Mobile robots for planetary exploration. (1996). Control Engineering Practice, Vol. 4, No. 4, (Apr. 1996) page numbers (513–524), 0967-0661. (in Chinese) Glenn Reeves & Tracy Neilson. (2005). The Mars Rover Spirit FLASH Anomaly. Aerospace Conference, 2005 IEEE, pp. 4186-4199, Mar. 2005. 3 Mobile Wheeled Robot with Step Climbing Capabilities Gary Boucher, Luz Maria Sanchez Louisiana State University, Department of Chemistry-Physics Shreveport LA, USA 1. Introduction The field of robotics continues to advance towards the ultimate goal of achieving fully autonomous machines to supplement and/or expand human-performed tasks. These tasks range from robotic manipulators that replace the repetitious and less precise movements of humans in factories and special operations to complex tasks which are too difficult or dangerous for humans. Thus an important and ever-evolving area is that of mobile robots. Extensive research has been done in the area of stair-climbing for mobile robotics platforms. Humanoid, wheeled, and tracked robots have all been made to climb stairs, however in most of these cases robots where designed for two dimensional operations and then later utilized or modified for stair climbing. (Herbert, 2008) Although strides have been made into exotic forms of legged robots, the conventional methods, such as wheels or tracks still form the basis for robotic locomotion. The wheeled mobile systems are useful for practical application compared with the legged systems because of the simplicity of the mechanisms and control systems and efficiency in energy consumption (Masayoshi Wada 2006). To better understand the problems faced by mobile ground based robots one must understand the expected terrain that the machine must negotiate. This can range from un-level ground to rocky and irregular terrain and in some cases man-made obstacles such as steps or stairs must be climbed. Each of these applications has unique challenges and solutions. In 2003, Louisiana State University-Shreveport took on the task to create an alternate approach to a rugged terrain robot capable of traversing not only rough terrain, but also man-made obstacles, such as steps and stairs, with the intent to meet the requirement to ascend and descend between levels in a building as in the case of security robots performing their tasks. The project further addressed the issue of observation capabilities to handle obstacles in the robot’s path. In conjunction with our Computer Science CSC 410 course in robotics, the LSUS Department of Chemistry-Physics took up the challenge to develop a robotic design that would meet these requirements. The criteria that factored into the initial concept phase of the project were the following: First the robot must be robust, capable of extended service in rugged environments and carry its own power source. Secondly, the robot must also have versatile vision systems which can relay the video information back to the operator via radio signals Mobile Robots - State of the Art in Land, Sea, Air, and Collaborative Missions50 or a fibre optic link. Thirdly, the device should have the ability to climb steps and stairs for changing floors in a building. The challenge was then handed to the students A robot using more than four wheels could compete with some tracked devices if the wheels are driven simultaneously. One approach considered to meet this requirement was through the use of a hydraulic motor on each wheel. This would allow all wheels to derive their rotation from one single power source. A central hydraulic pump generating a constant flow of fluid could provide the source to power the device. This concept was first patented by Joseph Joy in 1946 (Joy, 1946). Joy described a 16 wheel automobile capable of being driven by 8 hydraulic motors powered by a single engine and hydraulic pump. Such a scheme for driving a robot would require two hydraulic pumps and two sets of motors, one set for the left and one for the right side of the robot. The differential drive would then allow turning much the same way as tank treads. The motors could be in series on each side and therefore produce the same rotation for the volume of fluid pumped. Hydraulic pumps and motors were ruled out in the LSUS robot due to cost and the shear bulk of two hydraulic systems with proportional rate of flow control. The concept of wheel sets that can rotate is also not new. As far back as 1932 Raphael Porcello patented their use in numerous mobile devices from baby carriages to landing gear for airplanes (Porcello, 1932). Although not driven, these wheel sets demonstrated the versatility of allowing wheels to be grouped together and have their individual axels fixed at a certain common radius from the axes of wheel set rotation. The LSUS design consensus centered on using sets of two wheels that used parallel individual axels each offset a given radius from the wheel set axis of rotation. In this way, the wheels could revolve and also be powered from a source of angular speed and torque. The wheels sets could also revolve in any direction independent of the rotation of the wheels. This design seemed to satisfy the primary requirements for the robot for both rough terrain and stair climbing. 2. Related Work In 1991 King et al patented a method of stair climbing using a robot with rotating wheel sets (King et al, 1991). This device used two sets of two wheels each for stepping and used a larger front wheel to ride up and over oncoming steps. This larger wheel was forced by the rotating rear wheel sets. This novel approach used counter rotation between the rear wheel sets and the individual wheels in the sets. Thus, if properly geared, each wheel set would “step” motionless on each stair step without rotating relative to the stairs. This requires the proper ratio of wheel set speed and rotational speed for the tires. The early work by King et al was followed by several unique approaches to rotating wheel sets for stair climbing robots. Andrew Poulter set forth the concept of a robotic all-terrain device that consisted of two elliptical halves or “clam shells” that supported the drive mechanism for two wheels (Poulter, 2006). These clam shells were articulated as connected together with a common shaft. In this way, the robot could almost continuously have all four wheels in touch with the surface. Although not intended for stair climbing this device demonstrated articulated wheel sets. Poulter also used a long boom situated between the two clam shells that could be rotated to right the vehicle should it topple over or need to raise the forward or rear wheel sets. This [...]... CA, USA, May 19- 23, 2008 Masayoshi Wada “Studies on 4WD Mobile Robots Climbing Up a Step” Proceedings of the 2006 IEEE International Conference on Robotics and Biomimetics December 17 - 20, 2006, Kunming, China Joseph Joy “Automotive Vehicle” Patent 239 332 4 Application September 18,1982, Serial No 458,886 I1 Claims (a.18 0-17) Raphael Porcello “Wheeled Device” Patent 1887427 April 6, 1 932 Edward G King,... board shows a standard microcontroller board connected to a board housing the V-Stamp The VStamp board has a Maxim RS- 232 driver IC for connection of the device to both the outside programming computer and also the microcontroller The V-Stamp uses a 3. 3 volt power supply and has a 0 to 3. 3V serial connection that is relatively easy to connect to any standard microcontroller The V-Stamp operates in several... reduction The wheel-set rotation around a central axel delivers the articulation needed to conform to terrain contour Figure 3( a) and 3( b) show the side and top profile of the wheel sets used on WHEELMA a) b) Fig 3. (a) Side View of Wheel Set (b) Top View of Wheel Set 54 Mobile Robots - State of the Art in Land, Sea, Air, and Collaborative Missions This design further allows fulfillment of the above... Sydney University, pp.225- 234 Lauria, Piguet and Siegwart, R “Octopus – An Autonomous Wheeled Climbing Robot” Proceedings of the Fifth International Conference on Climbing and Walking Robots, 2002 CSG Network (2008) http://www.csgnetwork.com/hamfreqtable.html :accessed Aug 2008 62 Mobile Robots - State of the Art in Land, Sea, Air, and Collaborative Missions 4 Cable-Climbing Robots for Power Transmission... selectable Secondarily, you can record up to 33 minutes of sound into the RC86L60F4I version of the V-Stamp and play it back on defined boundaries The user can use Indexes or Tags which allow the user to utilize either ASCII text labels or serial numbers for each word or phrase recorded In designing the voice system provisions were made to connect an RS- 232 cable directly to the V-Stamp for entering... shows the base station along with associated switches, receiver controls, and TV for monitoring returning video from the robot 56 Mobile Robots - State of the Art in Land, Sea, Air, and Collaborative Missions Fig 4 Wheelma Resting on Inner Wheels Fig 5 Controls Station Mobile Wheeled Robot with Step Climbing Capabilities 57 4 Vision System and Directional Orientation Many robotic designs rely on either... Shackelord, Jr., Finksburg; Leo M Kahl, Baltimore, all of Md Patent 49 939 12 February 19,1991 Andrew R Poulter 80128 United States “Rugged Terrain Robot”Patent (10) Patent NO.: US 7,011,171-BI Poulter (45) Mar 14,2006 Yasuhiko Eguchi “Stairway Ascending/Descending Vehicle Having an Arm Member with a Torque Transmitting Configuration” Patent 5 833 248 Nov 10,1998 Ray A Jarvis, “Autonomous Navigation of a Martian... Electronically Engineered Linear Motion Apparatus), the LSUS designed robot that uses the Eguchi concept Fig 1 Wheelma Robot based on Eguchi system 52 Mobile Robots - State of the Art in Land, Sea, Air, and Collaborative Missions Extreme examples of wheeled robots use multiple wheel drive that is articulated not in a rotary manner but in a vertical manner A vertically wheel articulated system is seen in... precisely from close distances to the line that are not accessible by a mobile platform such as a helicopter or even an unmanned aerial vehicle (UAV) Hence, power companies have endeavored to make especial cable-climbing robots to accomplish inspection tasks from close distances to the hot line Thanks to technological advances, utilizing robots as reliable substitutes for human beings in hazardous environments... through investigation of their symptoms Most of the line problems produce unusual partial discharges Whenever the electric field intensity on the line surface exceeds the breakdown strength of air, electrons in the air around the conductor ionize the gas molecules and partial discharges, namely corona effects, occur High frequency partial discharges produce radio noise in ultra-high frequency range, as well . surmount obstacle. Journal of Harbin Institute of Technology, Vol. 35 , No. 2, (Feb. 20 03) page numbers (2 03- 2 13) , 036 7-6 234 . (in Chinese) Zongquan Deng; Haibo Gao; Shaochun Wang & Ming. contour. Figure 3( a) and 3( b) show the side and top profile of the wheel sets used on WHEELMA. a) b) Fig. 3. (a) Side View of Wheel Set (b) Top View of Wheel Set Mobile Robots - State. Maxim RS- 232 driver IC for connection of the device to both the outside programming computer and also the microcontroller. The V-Stamp uses a 3. 3 volt power supply and has a 0 to 3. 3V serial