Hyundai Yanmar TNV Series Manual page 59

CONTROL SYSTEM
Figure 2-29 shows the engine speed control block diagram.
[Speed control]
The deviation of the actual engine speed (Nrpm) from the target engine speed (Nset) is used to determine
the target rack position (Rset) with PID control. The target rack position is the basis for providing torque
limitation or rack motion delay adjustment for transition control (described later).
[Rack position control]
The deviation of the actual rack position (Ract) from the target rack position (Rset) is used to determine the
target current (Iset) with PID control. To check that the control system of the Eco-governor works properly,
use the service tool to make sure that Ract is approximately equal to Rset while the engine is running.
[Current control]
The deviation of the actual current (Iact) from the target current (Iset) is used to determine the target PWM
duty ratio with PID control. Current control helps improve the motion responsiveness of the rack or facilitate
diagnostics of the rack solenoid
Nset
Target
Speed
Transition control
The Eco-governor delays the rack motion at engine start or during acceleration in order to minimize the
emission of black smoke. See Figure 2-30.
Mech. Gov.
Eco-Gov.
2-40
PI-D PI-D
P
（Droop）
Target Position
Rset
I +
-D
Rack Position Sensor:Ract
Engine Speed Sensor:Nrpm
・Limit
・Delay
Figure 2-29 Engine speed control block diagram
Starting
0 200 400
Cut Excess Fuel
Figure 2-30 Transition control
Target Current
Iset
PID PID
Current Sensor:Iact
Full Q
Mech. Gov.
Eco-Gov. Eco-G -Gov.
600 800 1000
TNV Application Manual
Solenoid Rack Engine
current position speed
Solenoid Pump Engine
Acceleration
1200 1400
-1
Speed min