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IMS-MN-LMDA42C_A.pdf
Basics
LMD CANopen
Basics
Mode of Operation
The “LMD CANopen”, which uses DS301 communication profile, is the interface between device
profiles and CAN bus. It was specified in 1995 under the name DS301 and defines uniform
standards for common data exchange between different device types under CANopen.
The DSP402 device profile describes standardized objects for positioning, monitoring, and
settings of drives.
•
Profile position
: defines the positioning of the drive. Speed, position, and acceleration can be
limited, and profiled moves using a trajectory generator are also possible.
•
Homing mode
: describes the various methods to find a home position, reference point, date,
or zero point, on start up, or via an immediate mode command.
•
Profile Velocity
: used to control velocity of the drive with no special regard of the position.
It supplies limit functions and trajectory generation.
•
Profile Torque
: (available on closed loop and absolute encoder models only) defines the
torque control with all related parameters.
•
Cyclic synchronous position mode
: the trajectory generator is located in the control device,
not in the drive device. In cyclic synchronous mode it provides a target position to the drive
device, which performs position control, velocity control, and torque control.
Hybrid Motion Technology (hMT)
NOTE:
hMT is only available on LMD CANopen models with an encoder.
Hybrid Motion Technology is the core control technology that enables the multi-mode
functionality of the LMD by overcoming many of the limitations inherent in stepper systems.
Two major limitations addressed by this technology are:
• Loss of motor synchronization and subsequent stalling.
• Excessive motor heat due to limited current control options.
Loss of Synchronization
Synchronous motion in a stepper motor requires that the lead/lag relationship between the
rotor and stator be /- 2 motor full steps. As this relationship drifts toward the 2 step
point the torque available to the load is reduced, with maximum constant torque available at
the
≤
1 full step point.
Conditions that can cause the stepper motor to lose synchronization and stall are:
Rotor Lags Stator:
• Acceleration is too rapid to apply enough torque to overcome the inertia of the load.
• Transient load condition at velocity (i.e., load being increased on a conveyor).
Rotor Leads Stator:
• Deceleration is too rapid to hold the load within the +/- 2 full step range.
• Overhauling load condition where the momentum of the load is greater than the torque
supplied to maintain constant velocity.
