Wesley BC-620-4CA - Manual (Page 98)

94 Curtis 1234/36/38 Manual,
OS
11
Brake Processing
Brake processing is optional as it can be turned Off (by setting Brake_Pedal_En-
able = Off, see page 45). If turned On, brake processing can be done with or
without VCL. Any non-zero brake command will then override the throttle signal
and the motor controller will brake to a stop as determined by the parameters
Brake Current Limit (page 39) and Brake Taper Speed (page 36).
The lower part of Figure 14 shows the brake signal processing section.
The brake signal chain flows from left to right starting with the physical brake
pot. The voltage on the brake wiper input (pin 17) is input into the control-
ler and has the VCL variable name Pot2_Raw which is displayed in the 1311
Monitor
» Inputs menu. This brake signal is then modified by the Brake Type
Processing and Brake Mapping blocks.
The Brake Type Processing block uses the Brake_Type parameter (page 45)
and the brake potentiometer input (Pot2_Raw) to create a signed 16-bit variable.
This brake signal then passes to the Brake Mapping block, which re-shapes the
brake signal according to the various Brake Menu parameters (page 45).
The signal then passes through a selector switch. If the Brake_Type pa-
rameter is set to 5 (Brake Type = VCL input, see page 45), the Brake Mapping
block output signal is ignored and the command comes from the VCL variable
VCL_Brake. The VCL program manipulates the VCL_Brake variable to get a
brake command. Custom braking functions can be set up in this fashion; e.g.,
braking based on a switch position or an internal fault. The brake potentiometer
can still be used, but must be set up using the Setup_Pot() function. When the
Brake Type is set to 1–4, the variable VCL_Brake does nothing and the Brake
Mapping block output signal passes through.
After the “Brake Type = 5” switch, the brake signal passes through a limiter
which limits the brake signal to a range of 0–100% (0–32767). After the limiter
the brake signal is a VCL variable called Mapped_Brake, which is displayed in
the 1311 Monitor
» Inputs menu. Checking the value of Mapped_Brake using
the 1311 is a good way to see if your Brake Menu parameters are set correctly.
A VCL program can control the brake by changing the variable VCL_Brake
(only if Brake Type = 5).
The brake signal then goes through a second selector switch that will set
the brake signal = 0% if the Brake Pedal Enable parameter (page 45) is set Off.
If set On then the brake signal will pass through. The brake signal after this
second selector switch is a VCL variable called Brake_Command, which is
displayed in the 1311 Monitor
» Inputs menu.
Brake_Command is the final value of the brake signal chain that is input
to the Control Mode Processing block; see Figure 15. Checking the value of
Brake_Command using the 1311 is a good way to see the final brake signal.
If Brake_Command is non-zero in Speed Mode Express or Speed Mode, the
throttle signal will be set to 0%.
7 — VCL