Robot Mechanisms and Mechanical Devices Illustrated - Profe Saul

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184 Chapter 5 Tracked Vehicle Suspensions and Drivetrains very capable layout results. The main chassis is geared to the shared axle so it is always at the half-angle between the front and rear tracks, which allows it to be raised up yet still be level when folding both tracks down. This trick raises the entire chassis, but it also offloads the weight of the robot from the track guide blades, increasing rolling efficiency when high traction is not needed. This reconfigurable layout combines the high mobility of tracks with good smooth-road rolling efficiency. There are two basic layouts for four-tracked vehicles. They are both train-like in that there are two two-tracked modules connected by some sort of joint. The two modules must be able to move in several directions relative to each other. They can pitch up and down, yaw left and right, and, ideally, roll (twist). The simplest connection that allows all three degrees of freedom is the ball joint. If the joint is passive, steering is accomplished in the same way as a two-tracked vehicle, except that now both modules must turn at just the right time to keep skidding between the modules to a minimum. This turns out to be tricky. The ball joint also limits the range of steering angle simply because the socket must wrap around the ball enough to adequately capture it. A universal joint has a greater range of motion, and is easier to use if the joint is to be powered. The articulated joint, an active universal joint, overcomes the steering problem by allowing the tracks to rotate at whatever speed limits skidding. This steering method makes this layout very agile. The Hagglund Bv206, which uses this layout, is considered nearly unstoppable in almost any terrain from soft snow to steep hills. It is even amphibious, propelled through the water by the tracks. Because it cannot be skid steered, it can’t turn in place. Nevertheless, it is a very capable layout. Steering the Hagglund Bv206 is done with a standard steering wheel, which turns the articulated joint and forces the two modules to bend. The tracks are driven through limited slip differentials, allowing the inner and outer tracks in each module to travel at different speeds just like in an Ackerman steered wheeled vehicle. Six-Tracked Drivetrains There is at least one track layout (Figure 5-18) incorporated on an existing telerobotic vehicle that uses six tracks. It is an extension of the Urbie design, but was actually invented before Urbie’s layout. The twotracked layout is augmented by flipper tracks on both the front and back, independently tilted, but whose tracks are driven by the main track motors. This layout allows the vehicle to stand up like the one
Chapter 5 Tracked Vehicle Suspensions and Drivetrains 185 Figure 5-18 Six-tracked, double flippers shown in Figure 5-17. The double flippers extend the length of the twotracked base unit by almost a factor of two, facilitating crossing wide crevasses and climbing stairs, yet still being able to turn in place in a small aisle.
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vi Contents Commutation 34 Installa
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viii Contents Chapter 4 Wheeled Veh
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x Contents Industrial Robots 258 In
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xii Introduction a unique robot. Wh
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xiv Introduction outdoor and indoor
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xvi Introduction Rapid prototyping
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xviii Introduction Because the phot
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xx Introduction Meanwhile, the opaq
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xxii Introduction Laminated-Object
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xxiv Introduction Figure 5 Fused De
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xxvi Introduction ton. This process
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xxviii Introduction Figure 8 Ballis
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xxx Introduction laser fusing of ce
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xxxii Introduction material to form
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4 Chapter 1 Motor and Motion Contro
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10 Chapter 1 Motor and Motion Contr
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72 Chapter 2 Indirect Power Transfe
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100 Chapter 2 Indirect Power Transf
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110 Chapter 3 Direct Power Transfer
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130 Chapter 4 Wheeled Vehicle Suspe
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Page 228 and 229: 190 Chapter 6 Steering History In t
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Page 240 and 241: 202 Chapter 7 Walkers when crossing
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Page 252 and 253: 214 Chapter 7 Walkers ROLLER-WALKER
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Page 258 and 259: 220 Chapter 8 Pipe Crawlers and Oth
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234 Chapter 9 Comparing Locomotion
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236 Chapter 9 Comparing Locomotion
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242 Chapter 10 Manipulator Geometri
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266 Chapter 11 Proprioceptive and E
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292 Index CAM-LEM, Inc., xxiii camm
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294 Index (ground pressure cont.) a
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296 Index (mobility systems cont.)
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298 Index shear pin torque limiters
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About the Author Paul E. Sandin is
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Robot Mechanisms and Mechanical Devices Illustrated - Profe Saul

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