Robot Mechanisms and Mechanical Devices Illustrated - Profe Saul

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142 Chapter 4 Wheeled Vehicle Suspensions and Drivetrains Figure 4-11 rocker Simple longitudinal The longitudinal rocker design divides the entire vehicle right down the middle and places a passive pivot joint in between the two halves. This joint is connected on each end to a rocker arm, which in turn carry a wheel at each of their ends. This layout allows the rocker arms to pivot when any wheel tries to go higher or lower than the rest. This passive pivoting action keeps the load on all four wheels almost equal, increasing mobility simply by maintaining driving and braking action on all wheels at all times. Longitudinal rocker designs are skid steered, with the wheels on each side usually mechanically tied together like a simple skid steer, but sometimes, to increase mobility even further, the wheels are independently powered. Figure 4-11 shows the basic layout, developed by Sandia Labs for a vehicle named Ratler. The well-known forklift industrial truck uses a sideways version of the rocker system. Since its front wheels carry most of all loads lifted by the vehicle, structurally tying the wheels together is a more robust layout. These vehicles have four wheels without any suspension, and, therefore, require some method of keeping all the wheels on the ground. The most common layout has the front wheels tied together and a rocker installed transversely and coupled to the rear wheels, which are usually the steering wheels. Figure 4-12 shows this layout. The weakness of the forklift is that it is usually only two-wheel drive. This works well for its application, and because so much of the weight of the vehicle is over the front wheels. In general, though, powering all four wheels provides much higher mobility. In a two-wheel drive vehicle, the driven wheels must provide traction not only for whatever they are trying to get over, but also must push or pull the non-driven wheels. Many of the wheeled layouts are complex enough that they require a motor for
Chapter 4 Wheeled Vehicle Suspensions and Drivetrains 143 Figure 4-12 Rear transverse rocker, rear steer every wheel. Although this seems like a complicated solution from an electrical and control standpoint, it is simpler mechanically. Steering with the rear wheels is effective for a human controlled vehicle, especially in an environment with few obstacles that must be driven around. The transverse rocker layout can also be used with a front steered layout (Figure 4-13) which makes it very much like an automobile. Couple this layout with all wheel drive, and this is a good performer. Figure 4-13 Rear transverse rocker, front steer
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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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192 Chapter 6 Steering History and
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194 Chapter 6 Steering History Figu
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196 Chapter 6 Steering History Figu
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198 Chapter 6 Steering History forc
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202 Chapter 7 Walkers when crossing
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204 Chapter 7 Walkers Figure 7-1 On
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206 Chapter 7 Walkers Figure 7-4 Tw
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208 Chapter 7 Walkers and the relat
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210 Chapter 7 Walkers Figure 7-10 E
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212 Chapter 7 Walkers Figure 7-12 T
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214 Chapter 7 Walkers ROLLER-WALKER
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216 Chapter 7 Walkers Walkers have
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220 Chapter 8 Pipe Crawlers and Oth
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230 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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