User Manual

Global Power Configuration Parameters
Advanced Digital Motor Controller User Manual 89
Short Circuit Protection
The controller has got two levels of short circuit protection software and hardware
protection. Some Roboteq controllers includes a circuit that will detect very high current
surges that are consistent with short circuits conditions. Check with controller datasheet
for details.
The firmware utilizes the current sensors in order to detect short circuit. When such a
condition occurs, the power transistor for the related motor channel is cut off within a
PWM period time. The short fault will remain off until the command is brought back to
idle.
The protection is very effective but has a few restrictions:
Only shorts between two motor outputs of the same channel are detected. Shorts
between a motor wire and VMot are also detected. Shorts between motor output and
Ground are not detected.
It is noted that the software short circuit triggering is affected also from the load induc-
tance values and input battery voltage level.
Since the controller can handle very large current during its normal operation, Only direct
short circuits between wires will cause a sufficiently high current for the detection to
work. Short circuits inside motors or over long motor wires may go undetected.
Mixed Mode Select
Mixed mode is available as a configuration option in dual channel controllers to create
tank-like steering when one motor is used on each side of the robot: Channel 1 is used for
moving the robot in the forward or reverse direction. Channel 2 is used for steering and
will change the balance of power on each side to cause the robot to turn. Figure 7-2 below
illustrates how the mixed mode motor arrangement.
Controller
FIGURE 7-2. Effect of commands to motor examples in mixed mode
The controller supports 3 mixing algorithms with different driving characteristics. The table
below shows how each motor output responds to the two commands in each of these
modes.