Spline Relative Sine Move

Character: w
Decimal: 119
Hexadecimal: 0x77
Command Value: Offset from the Spline that the Slave Must Move to

Note: This command is only available in the special ’r;SI’ RMC100 CPU firmware (e.g. 20020624SI). ’r;SI’ firmware is available only on request, as it useful only for special applications. It may not be compatible with standard firmware.

This command moves an axis from its current position to a position relative to a spline. The spline must previously have been loaded to the RMC.

This command carries out two actions:

It activates the spline currently in the RMC.
It then superimposes a sine move from the current position to an offset from the spline. Note that the offset can be zero, moving the axis onto the spline.

The Spline Relative Sine Move (w) command parameters are defined as follows:

Command Parameter	Description
Mode	The superimposed and gear bits must be set.
Acceleration	Time/Distance Select: If the Speed parameter is zero, this parameter specifies the time for this move to complete.
Deceleration	Spline Position: Specifies the position of the leftmost point of the spline. This effectively shifts the spline right or left as viewed on the curve tool, providing a starting point other than the default of zero.
Speed	Master Move Distance: The sine move occurs as the master moves this distance. If this parameter is zero, the sine move will be based on time. Note that this value can be negative.
Command Value	Offset: This is the distance the slave must move from the spline.

Why Bother?

This command can be used to transition from one spline to the next if the start and end points are not the same. This command can also be used when changing splines on the fly. If this command is issued while already following a spline, it will move to the specified offset to the new spline.

To carry out his command, the RMC performs the following steps:

1. First the RMC calculates where to index into the spline table. This is done by using the master axes current position and subtracting the DECEL field to get the X index in the curve tool. For example, if the master is at 500 position units and the minimum position (DECEL field) is 400 position units, the X index would be 100 position units. NOTE: Never let the master position go below the minimum or maximum positions!

2. The RMC uses the X index (or master position) to interpolate a position from the spline to find the Y position (spline position).

3. The Command Value (spline offset) is added to the Y position to get the destination to where the slave must move.

4. The relative distance between the slave’s destination and current position is calculated.

5. The speed field determines how the sine move is executed as a function of the change in the master's position.

The slave now initializes two target generators. One calculates the current spline position as a function of the master's X index. The other starts the sine move that will move the relative distance calculated in step 4. The resulting speeds and differences in position are summed to make a smooth move that converges at the offset from the spline.
Once the axis position has reached the offset spline position, the axis will continue to follow the spline at the offset given the Command Value.