Robot Mechanisms and Mechanical Devices Illustrated - Profe Saul

146 Chapter 4 Wheeled Vehicle Suspensions and Drivetrains
Figure 4-15
mechanism
Pitch averaging
vehicle traverses bumpy terrain. If you attach the chassis to this gear, the
pitch angle of the chassis is half the pitch angle of either side rocker. This
pitch averaging effectively reduces the pitching motion of the chassis,
maintaining it at a more level pose as either side of the suspension system
travels over bumps. This can be advantageous in vehicles under
camera control, and even a fully autonomous sensor driven robot can
benefit from less rocking motion of the main chassis. This mechanism
also tends to distribute the weight more evenly on all four wheels,
increasing traction, and, therefore, mobility. Figure 4-15 shows the basic
mechanism and Figure 4-16 shows it installed in a vehicle.
Another mechanical linkage gives the same result as the differentialbased
chassis pitch-averaging system. See figure 4-17. This design uses
a third rocker tied at each end to a point on the side rockers. The middle
of the third rocker is then tied to the middle of the rear (or front) of the
chassis, and, therefore, travels up and down only half the distance each
end of a given rocker travels. The third rocker design can be more volumetrically
efficient and perhaps lighter than the differential layout.
Another layout that can commonly be found in large industrial vehicles
is one where the vehicle is divided into two sections, front and rear,
each with its own pair of wheels. The two sections are connected through