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Juno Step Motor Control IC User Guide
67
11
11.Internal Profile Generation
In This Chapter
Juno Cycle Time
Profile Parameter Scaling
Profile Stop Events
Settable Parameters
Juno ICs include an internal profile generator that allows arbitrary contours of the step motor position command to be
generated. The profile generator is used in conjunction with serial host commands to specify move profiles.
To control the profile generator the user specifies a desired target acceleration, deceleration, and velocity. Using these
target parameters Juno’s profile generator performs calculations to determine the instantaneous position, velocity, and
acceleration of the profile at any given moment. These instantaneous profile values are called the commanded values.
During profile execution, some or all of the commanded values will continuously change as the profile is generated.
Figure 11-1:
Internally
Generated
Velocity Profile
The profile is executed by continuously accelerating at the user-specified target acceleration rate until the user-specified
target velocity is reached. The sign of the velocity parameter determines the initial direction of motion. Therefore the
velocity value sent to Juno can have a positive value (for positive direction motion), or a negative value (for negative
direction motion).
The axis decelerates at the user-specified target deceleration when a new velocity is specified with a smaller value (in
magnitude) than the present velocity, or when a new velocity has a sign that is opposite to the present direction of travel.
When a decelerating axis decelerates through a velocity of zero and reverses direction, after crossing through zero
velocity the axis will apply the acceleration target rate rather than the deceleration target rate. Specified acceleration and
deceleration values must always be positive.
Note that if the deceleration target value is set to zero Juno will use the specified acceleration target value for the
deceleration value.
illustrates a complex profile in which the specified velocity and the direction of motion changes several
times.
Velocity
Time
+
_
A1
V1
-D
V3
V2
V4
A1
D
D
-A1
A1
V5
Change
Velocity to V2
Change
Velocity to V3
Change
Velocity to V4
Change
Velocity to V5
A2
Change
Acceleration to
A2