Sevcon Dragon8 User Manual

Doc. # 177/52705
Rev. 1.0
68
Speed
Actual Speed
Speed Limit
Vehicle wheels lock, but rather than
stepping down speed limit, it ramps
down at the maximum speed limit
deceleration rate as specified in
object 291E. When wheels recover,
the motor control will allow them to
rotate again.
Figure 30 - Example of behaviour of speed limit when drive wheels are locked
WARNING: It is important to consider the behaviour of the vehicle under all drive conditions,
including when traction is lost due to locking of the drive wheels. When testing a vehicle, check
that the vehicle behaves in a safe manner when performing harsh braking on low-friction surfaces
such as gravel.
Controlled roll-off
WARNING: Controlled Roll-Off is not recommended for on-highway vehicles as it can cause the
traction motor/wheel to remain locked or brake severely if the wheel is momentarily locked due
to loss of traction on a slippery surface and/or mechanical braking.
Controlled roll-off limits a vehicle to a slow, safe speed if it starts to move without any operator input.
Primarily, it is to prevent uncontrolled movement if a vehicle’s brakes fail on an incline. Controlled roll-
off operates whether the operator is present or not.
Configure the following at object 2930
h
:
• Enable/disable controlled roll-off
• Set a roll-off maximum speed
• Set a roll-off maximum torque
Alternatively, Dragon8 can apply an electromagnetic brake if one is mapped and roll-off is detected.
Refer to ‘Electro-mechanical brake’ on page 73 for more information.
Hill hold
WARNING: Hill Hold is not recommended for on-highway vehicles as it can cause the traction
motor/wheel to remain locked or brake severely if the wheel is momentarily locked due to loss of
traction on a slippery surface and/or mechanical braking.
A vehicle on a hill can be held at a standstill for a configurable time when the operator selects neutral. At
the end of this time or if the seat switch indicates the operator is not present, hill hold terminates and the
vehicle can start to move if parked on an incline. If enabled, the system will enter controlled roll-off
after hill hold.
You can set the hill hold delay at object 2901
h
. Set the hill hold delay to 0 to disable this feature.
In speed mode, drive torque is disabled whilst neutral braking to stop. However, drive torque must be
re-enabled when entering Hill Hold to allow torque to be applied to hold on the incline. Set the speed to
re-enable drive torque at 2908
h
.

Sevcon Dragon8 Specifications

General

Brand	Sevcon
Model	Dragon8
Category	Controller
Language	English