... layouts, 148 , 149 f four-wheeled layouts, 141 148 all-terrain cycles (ATCs), 197 NASA JPL prototype, 144 145 four-wheeled layouts articulated vertical-axis joint, 148 f 149 f chassis link-based pitch averaging ... layouts, 148 , 149 f four-wheeled layouts, 141 148 all-terrain cycles (ATCs), 197 NASA JPL prototype, 144 145 four-wheeled layouts articulated vertical-axis joint, 148 f 149 f chassis link-based pitch averaging ... mechanism, 146 , 147 f chassis pitch averaging mechanism, 147 f wheel-terrain contact, 141 , 142 f 143 f, 148 and ground pressure, 130–131 holonomic motion, 139 negotiable obstacle height, 134 one-wheeled...