Interfacing The Proportional Current Driver - Curtis 1298 User Manual

7 — VCL
Fig. 20
Proportional driver processing.
100

INTERFACING THE PROPORTIONAL CURRENT DRIVER

In the 1298, the proportional current driver is used for the lowering valve; see
Figures 15 and 16, on page 50. For other connections, VCL can directly interface
the proportional current driver (PD), as shown in Figure 20. VCL can change
the working parameters of the PD and can provide the command.
Depending on how the PD system is to be used, certain parameters need
to be set; they can be set via the 1311 handheld programmer or via VCL.
1. PD_Enable must be set On for current control, otherwise
the PD_Output will be controlled by the VCL function
Put_PWM(PWM5,xxxx), which is voltage control.
2. Hyd_Lower_Enable must be set On to use the throttle input
to control lowering in a hydraulic lift/lower system.
3. Hyd_Lower_Enable must be set Off to allow using a VCL
variable (VCL_PD_Throttle) as the PD command.
Once the PD parameters are set, the PD_Throttle variable will be mapped
between PD_Min_Current and PD_Max_Current and sent to the dither
function. Note that Mapped_Throttle is inverted; lowering its value (making
it more negative) increases the PD_Throttle value.
The Dither function adds and subtracts from the current command to
the PD based on PD_Dither_Percent, at a rate set by PD_Dither_Period.
The dithered current command is compared to the present PD_Current
and the error is fed into a PI controller. The feedback gains are set by the param-
eters PD Kp (proportional gain) and PD Ki (integral gain). The output of the
PI controller becomes the driver's pulse width modulation, thus controlling the
average current of the driver. This final output is the VCL variable PD_Output,
which is displayed in the 1311 Monitor» Inputs menu as PD PWM.
Curtis 1298 Manual,
11
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