MoveRelative() [2/3]

void MoveRelative	(	double	relativePosition,
		double	vel,
		double	accel,
		double	decel,
		double	jerkPct )

Description:

MoveRelative command a relative point-to-point motion, with an S-Curve velocity profile. Axis will move relative increment distance from the currently commanded position.

S-Curve Velocity Profile

Parameters

relativePosition	A relative increment, positive or negative.
vel	Maximum velocity, UserUnits/second.
accel	Maximum acceleration , UserUnits/second/second. (peak up to 2× accel when jerkPercent = 100, see below)
decel	Maximum deceleration , UserUnits/second/second. (peak up to 2× decel when jerkPercent = 100, see below)
jerkPct	Jerk Percent, which defines the percentage of acceleration time which is smoothed, 0.0 to 100.0 .

Note

In most cases, a servo motor has a feedback device mounted. Depending on feedback device resolution, one motor shaft rotation will produce fixed value of counts. Example: motor has a resolution of 8192 counts. This means if 8192 is entered as distance to move, motor will move single revolution. User can implement UserUnitsSet() to change to a different unit (ex: mm, inches, etc) from encoder counts.

Note

Non-Blocking Execution Motion commands return instantly and do not pause code execution. Use MotionDoneWait() post-call to block execution until motion completes, or MotionDoneGet() to poll for completion.

Warning

Using a non-zero JerkPercent increases the maximum acceleration above the user-specified average.
If your system can’t handle the higher peak, you risk overshoot or excessive load. The relation between average acceleration and maximum acceleration is:

\[ Maximum Acceleration \;=\; \frac{accel}{1 - \bigl(jerkPercent \times 0.005\bigr)} \]

• accel: the requested (average) acceleration value given in the MoveSCurve command.
• jerkPercent: the percent of time with non-zero jerk (0–100) given in the MoveSCurve command.
• Maximum Acceleration: the resulting peak commanded acceleration.

See the S-Curve Motion concept page for more information.

Warning

Using a non-zero JerkPercent increases the maximum deceleration above the user-specified average.
If your system can’t handle the higher peak, you risk overshoot or excessive load. The relation between average deceleration and maximum deceleration is:

\[ Maximum Deceleration \;=\; \frac{decel}{1 - \bigl(jerkPercent \times 0.005\bigr)} \]

• decel: the requested (average) deceleration value given in the MoveSCurve command.
• jerkPercent: the percent of time with non-zero jerk (0–100) given in the MoveSCurve command.
• Maximum Deceleration: the resulting peak commanded deceleration.

See the S-Curve Motion concept page for more information.

Part of the Motion method group. See the S-Curve Motion concept page for more information.

Sample Code:

RelativeMotion

      axis.MoveRelative(Constants.POSITION, Constants.VELOCITY, Constants.ACCELERATION, Constants.DECELERATION, Constants.JERK_PERCENT);  // Command a relative to the current position
      axis.MotionDoneWait(); // Wait for motion to finish. (the motion should take 2.5 seconds)
 
      var cmdPositionAfterMove = axis.CommandPositionGet(); // The command position should be equal to Constants.POSITION
 
      // Move back to the start position by moving negative relative to current position
      axis.MoveRelative(-1 * Constants.POSITION, Constants.VELOCITY, Constants.ACCELERATION, Constants.DECELERATION, Constants.JERK_PERCENT);
      axis.MotionDoneWait();

RapidSetup:

Go to axis screen->Motion Profile box (left) to select type of motion
Go to axis screen->Motion Parameters box (right) to select values for motion

Motion Scope:

Relative move profile shown below:

See also

Point to Point, MoveSCurve, MoveTrapezoidal, MoveVelocity, MovePT, MovePVT

Examples

DifferenceOfPositionUserLimit.cpp, MathBlock.cs, Motion.cs, MotionHold.cs, MotionHoldReleasedBySoftwareAddress.cpp, and PointToPoint.cpp.