Follow Spline Segment Command

Character: f
Decimal: 102
Hexadecimal: 0x66
Command Value: Unused

This command will begin following the next available spline segment. If there is only one spline segment loaded, then this segment will be repeated even if it has already been followed. See also the Follow Spline Relative command.

This command does not use Accel, Decel, Speed, and Command Value. These unused fields should be set to 0 for forward compatibility. However, the following bits of the Mode word are used: Graph Disable, Monitor Pressure, Rotational, and Geared bits. Each should be adequately described in the Mode word topic, but see the description below for more information on Gearing a spline.

The In Position bit of the Status will be cleared when this command begins and will be set when the axis reaches the end of the spline. The State A and State B status bits will be cleared throughout the spline.

The axis must already be at the position of the first spline point (the Follow Spline Relative command does not require this). This can be ensured by the programmable controller by giving a Go (G) command to the first location and waiting for the In Position status bit to be on or for State A and State B status bits to both be off. This is left as the user’s responsibility to allow the user to control the manner that the axis moves to the first location.

This command can fail for the following reasons, as indicated by the Parameter Error bit in the Status word:

The axis is not stopped when the command was issued. The axis is stopped when State A and State B status bits are off.
The axis is not at the location of the first point in the spline. The Target Position must be equal to the Command Position which must be equal to the first position of the spline.
There is no spline segment available to follow.

The rate at which the axis moves through the spline is determined in the following manner:

If the Mode word has the Geared Mode bit set, the spline is geared to another axis. Gearing a spline is most useful when geared to an axis in speed control, or an independent quadrature input.

Note: In RMC100 CPU firmware dated prior to 19990625 (or beta firmware dated prior to 19980827B) the Geared Mode bit is ignored and therefore assumed to be cleared.

The gearing relationship works as follows:

The master axis is given by the Gear Master Select bits in the Mode word.
The slave axis may be geared based on the master axis’s actual or target position. Select this with the Gear Type bit in the Mode word.
Once the gearing has been set up, each position unit that the master axis increases results in the slave axis moving forward one time unit in the spline. Similarly, when the master axis position decreases by a position unit, the slave axis moves backward one time unit in the spline.
If the Mode word is cleared and the module has a Sensor DI/O with an Edge or Quadrature counter enabled, the spline is geared to this counter. Each time interval represents one counter tick. For a quadrature counter, reversing the direction of the quadrature counts reverses the direction the spline is interpolated (forward vs. backward).
If the Mode word is cleared and the module does not have an enabled Sensor DI/O counter, the spline is interpolated at a fixed rate based on time. Each time interval represents one millisecond.

Addendum for Special Firmware ’r;SI’ (e.g. 19980827SI)

This firmware is available only on request, as it useful only for special applications. This firmware includes superimposed mode. The above description of this command is appended in the following ways:

The Geared Mode bit is used, despite the note about firmware versions.
The Superimposed Mode bit is used as follows:

If set, the move may be superimposed on top of a Geared move, a Speed Control move, a Sine Move, or another Spline. If cleared, the spline will be the only move. Notice, that if the axis is stopped, the Superimposed bit may still be used without harm.
If set, the Status word’s State A and B bits will not be affected. However, the In Position bit will be affected. If cleared, the State A and B bits will be cleared during the spline.
If set, the entire spline is performed as relative to the current position. Therefore, the entire spline is adjusted to start at zero position, and then the curve is added to any other motion being performed on the axis. If cleared, the spline is assumed to be absolute and the axis must be at the first spline position before beginning the spline. This can be ensured by first issuing a Go (G) command to the first spline location.