Command: Gear Position (Clutch by Time) (30)

See the Commands Overview topic for basic command information and how to issue commands from PLCs, HMIs, etc.

Command Parameters

Description

This command gears the axis to the Master Register, using the value in this register as the master position. Typically the master register is the Target or Actual Position of another axis.

When this command is issued, the RMC uses the current gear ratio or determines the current gear ratio by comparing the velocities of the master and slave. The gear ratio is then ramped from its current effective ratio to the requested ratio, in the time specified by the Clutch Time parameter. The ratio is determined by the Numerator and Denominator.

If the master register is not a Target or Actual Position, the Gear Position (Clutch by Time) (30) command will assume an initial gear ratio of 0:1. This may cause a jerk in the motion of the geared axis if it is already moving.

If the master is moving very slowly or nearly stopped when this command is issued, the initial gear ratio may be very large. There are two ways to avoid this problem:

• Use a different gearing command, such the Gear Pos (Clutch by Rate) (39) command.

• First issue this command with a 0:1 ratio and a time of zero, then immediately issue this command again with the desired gear ratio and clutch time.

If both axes are stopped or moving very slowly, this command can be issued with a Clutch Time of zero. If either of the axes are moving, a Clutch Time of zero may cause a sudden jerk.

See the Gearing Overview topic for general information about gearing, including Gear Ratio, Clutching and possible Gear Masters.

Gear Position (Clutch by Time) Example

In this example, Axis 1 (slave) gears to Axis 0 (master) at a 1:1 ratio. Both axes start at 0 pu. The master starts moving at time 0. At 0.2 seconds, the following Gear Pos (Clutch by Time) command is issued to the slave.

Numerator = 1

Denominator = 1

Master Register = _Axis[0].TarPos

Clutch Time = 0.2 sec

The plot below shows how the slave moves.

At 0.2 seconds, when the command was issued to the slave, it began ramping up the velocity such that slave reached the specified gear ratio at 0.4 seconds.

Applications Not Suitable for Clutch by Time

The Gear Position command clutches based on time, which means it will reach the requested gear ratio in the time specified. This command is not well-suited for the following types of applications:

• If Position at which Axis Reaches Gear Ratio is Important
  The Gear Pos (Clutch by Time) command does not directly specify the position at which the gear ratio will be reached. If the axis must reach the requested gear ratio at a certain position, such as in flying cut-off applications, use the Gear Pos (Clutch by Distance) (32) command instead.

• If Maximum Velocity or Acceleration Must be Specified
  The Gear Pos (Clutch by Time) command does not limit the velocity or acceleration. If you need to limit the velocity or acceleration, use the Gear Pos (Clutch by Rate) (39) instead.

Specifying a Register Address

When issuing this command from anywhere other than RMCTools, the addresses in the Master Register command parameter must be entered as an integer value.

RMC addresses are represented in IEC format as:

%MDfile.element, where file = file number, and element = element number.

Use the following equation to convert a register address to integer format, N:

N =  file * 4096 + element

Example:

Register address %MD8.33 is 8*4096 + 33 = 32801.

Target Generator State Bits

The Target Generator bits in the Status Bits register indicate which portion of the motion the axis is currently in. These bits are useful when programming complex motion sequences.

Target Generator Done bit

Indicates the clutching is complete and the gear ratio is now locked, which occurs when the Time expires.

Target Generator State A and B bits

See Also

Gearing Overview | List of Commands | Commands Overview

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