Using Di Driver System To Control Fuel Pressure - National Instruments NI DIDS-2103 User Manual

3.4 Using DI Driver System to Control Fuel Pressure

The DI Driver System supports a common rail pressure control feature with optional NI 9758 PFI Driver and NI
9201 analog input modules. A typical common rail high pressure fuel system consists of a high pressure, cam-
drivven pump, connected to a fuel rail which supplies fuel to each injector. The high pressure pump has an Inlet
Metering Valve (IMV) which is a solenoid proportional valve that meters the fuel to the inlet of the pump. The IMV
is controlled with a lowside driver channel via PWM operation. The fuel rail has a pressure sensor connected to the
end, providing analog pressure feedback to the NI 9201 analog input module for rail pressure PID control. The rail
pressure PID control function generates a PWM duty cycle to maintain a specified rail pressure setpoint.
Some common rail fuel systems will have a High Pressure Valve (HPV) on the rail as a bleed valve to provide fuel
flow through the system for stable pressure control. The HPV is also a proportional solenoid valve controlled with a
lowside driver channel via PWM operation.
Refer to the Rail Pressure Control Setup window for details about configuring the rail pressure control function.
Typical IMV and HPV solenoids require up to 3A continuous current operation. Therefore it is important to utilize
the LS channel locking feature which locks LS1 with LS2 and locks LS3 with LS4 via the PFI and LS Driver Setup
window. The locked channel pairs can be used to operate the IMV and HPV with up to 3A continuous current. Figure
3.4.a shows an example wiring diagram for wiring an IMV to a locked LS1 and LS2 pair, and wiring a HPV to a
locked LS3 and LS4 pair.
Any of the four NI 9201 analog inputs can be assigned to the rail pressure control feedback via the Rail Pressure
Control Setup window.
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