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M4120170509EN
UI Robot Technology Co. Ltd.
UIM24102/04/08-IE
Note: Setting the Maximum Starting Speed or the Maximum Cessation Speed to 0(zero) will force
the controller use Linear Acceleration / Deceleration Control Algorithm.
7.5 S-curve Displacement Control
S-curve displacement control essentially is the displacement control under the linear
acceleration and deceleration speed control. The name is originated from the shape of the
motion trajectory. The original S-curve displacement control is the acceleration-coast-
deceleration speed control. In the entire trajectory, there is no knee point, which makes the
motion very smooth without impact or vibration. The control process is shown in figure 7-
9.
Figure7-9: S-curve Relative Displacement Control (case 1)
In the control process, UIM241XX’s advance motion control module will continuously
calculate the deceleration happening point (time) and then perform the deceleration to
guarantee that when desired displacement is reached, the speed is right zero. The entire
calculation time is around 20 micro-seconds with 64bit accuracy. In practice, when the
desired displacement is small and the desired speed is high, deceleration starts before the
desired speed is achieved to ensure that the speed decelerate to right zero when desired
displacement is completed. The process is shown in figure 7-10.
T
（
Time
）
Speed
Uniform Acceleration
Desired Speed
Trajectory
T
（
Time
）
Angular
Displacement
Uniform Deceleration
Start Position
Stop Position
