Page 210 - Mechatronics with Experiments

196 MECHATRONICS

(a)
Differential
Engine Transfer Parking brake
gear
Transmission
Differential
Rear axle
Center axle
Differential

Front axle
(b)
FIGURE 3.33: Powertrain of an articulated truck: Volvo Model A series, (a) picture of the
articulated truck showing the powertrain, (b) powertrain components: engine, transmission
with torque converter, differentials, (front, center, rear, inter axle (two of them)) and multi disc
brakes. Each differential has locking mechanism under operator (or ECM) control for traction
control purposes (Reproduced with permission from Volvo Trucks).

of the vehicle (too much accelleration or deceleration). Therefore, a good balance must
be found between a “smooth yet fast enough gear shift.” The clutch/brake modulation is
accomplished by controlling the solenoid operated valves that control the pressure in the
respective control cylinders of the clutches/brakes Figure 3.31. Each valve used to control
one of the clutch/brake is proportionally operated. It has at least three ports: the pump
pressure supply port, tank pressure supply port, output pressure port. By controlling the
position of the valve spool, the output pressure of the valve is proportionally controlled
between the pump supply pressure port and tank pressure port. Such valves are referred to as
electronically controlled pressure control (ECPC) valves. The logic of pressure modulation
may be open loop based on a time profile or closed loop based on measured pressure
feedback. Automatic transmission control algorithms have different names based on the
type of control logic they implement in the “gear selection algorithm” block (Figure 3.32a)
such as full throttle shift, part throttle shift, controlled throttle shift.

3.8.7 Example: Powertrain of Articulated Trucks

An articulated truck powertrain is shown in Figures 3.33 and 3.34 where a picture of
an articulated truck is shown along with the components of powertrain. The powertrain
components are