TMC5031 DATASHEET (Rev. 1.11 / 2016-APR-28)
43
9.2 Motion Profiles
For the ramp generator register set, please refer to the chapter 0.
9.2.1 Ramp Mode
The ramp generator delivers two phase acceleration and two phase deceleration ramps with
additional programmable start and stop velocities (see Figure 9.1).
Note
The start velocity can be set to zero, if not used.
The stop velocity can be set to ten (or down to one), if not used.
Take care to always set VSTOP identical to or above VSTART. This ensures that even a short
motion can be terminated successfully at the target position.
The two different sets of acceleration and deceleration can be combined freely. A common transition
speed V1 allows for velocity dependent switching between both acceleration and deceleration
settings. A typical use case will use lower acceleration and deceleration values at higher velocities, as
the motors torque declines at higher velocity. When considering friction in the system, it becomes
clear, that typically deceleration of the system is quicker than acceleration. Thus, deceleration values
can be higher in many applications. This way, operation speed of the motor in time critical
applications can be maximized.
As target positions and ramp parameters may be changed any time during the motion, the motion
controller will always use the optimum (fastest) way to reach the target, while sticking to the
constraints set by the user. This way it might happen, that the motion becomes automatically
stopped, crosses zero and drives back again. This case is flagged by the special flag second_move.
9.2.2 Start and Stop Velocity
When using increased levels of start- and stop velocity, it becomes clear, that a subsequent move into
the opposite direction would provide a jerk identical to VSTART+VSTOP, rather than only VSTART. As
the motor probably is not able to follow this, you can set a time delay for a subsequent move by
setting TZEROWAIT. An active delay time is flagged by the flag t_zerowait_active. Once the target
position is reached, the flag position_reached becomes active.
motor
stop
acceleration
phase
v
acceleration phase
deceleration phase
VMAX
D
M
A
X
X
A
M
A
V1
D
1
1
A
VSTOP
VSTART
0
t
-
A
1
VACTUAL
Figure 9.1 Ramp generator velocity trace showing consequent move in negative direction
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