# Menu 39 − AMC Position Control Loop

Mode: RFC‑S

Position control loop

Parameter | 39.001 AMC External Reference Select
--- | ---
Short description | Selects between using the position, speed and acceleration references from the output of the profile generator, or from external references
Mode | RFC‑S
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

If AMC External Reference Select (39.001) = 0 the position, speed and acceleration reference for the position control loop are taken from the output of the profile generator. However, it is possible to provide these references from an external application (i.e. an applications category module program). If AMC External Reference Select (39.001) = 1 the position reference is taken from AMC External Position Reference (39.002), the speed reference is taken from AMC External Speed Reference (39.004) and the acceleration reference is taken from AMC External Acceleration Reference (39.014).

Parameter | 39.002 AMC External Position Reference
--- | ---
Short description | Defines the external position reference
Mode | RFC‑S
Minimum | -2147483648 | Maximum | 2147483647
Default | 0 | Units | UU
Type | 32 Bit Volatile | Update Rate | AMC sample rate read
Display Format | Standard | Decimal Places | 0
Coding | RW

See AMC External Reference Select (39.001).

Parameter | 39.004 AMC External Speed Reference
--- | ---
Short description | Defines the external speed reference
Mode | RFC‑S
Minimum | −VM_AMC_SPEED | Maximum | VM_AMC_SPEED
Default | 0.00 | Units | UU/ms
Type | 32 Bit Volatile | Update Rate | AMC sample rate read
Display Format | Standard | Decimal Places | 2
Coding | RW, VM

See AMC External Reference Select (39.001).

Parameter | 39.005 AMC Inertia Compensation Mode
--- | ---
Short description | Selects the inertia compensation mode used by the position control loop
Mode | RFC‑S
Minimum | 0 | Maximum | 2
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | None
1 | Acceleration
2 | Torque

AMC Inertia Compensation Mode (39.005) selects the inertia compensation mode as shown below.

0 (None)

No inertia compensation.

1 (Acceleration feed-forwards)

When acceleration feed-forwards is selected a gain term is automatically calculated based on the currently active drive speed controller gains, Motor And Load Inertia (03.018) and Torque Per Amp (05.032). The acceleration feed-forwards term is intended to cancel the effect of the speed controller time constant and give a faster position control loop response. The acceleration feed-forwards term is only compatible with a first order speed controller, i.e. Speed Controller Set-up Method (03.017) = 7.

2 (Torque feed-forwards)

When torque feed-forwards is selected the acceleration from the profile generator is used to define the torque feed-forwards. The Motor And Load Inertia (03.018), Torque Per Amp (05.032) and the output user units ratio are used to convert from acceleration to torque. It should be noted that the Inertia Compensation Torque (02.038) is added to the output of the speed controller when Inertia Compensation Enable (04.022) = 1.

Parameter | 39.007 AMC Position Control Loop Kp Gain
--- | ---
Short description | Defines the proportional gain of the position control loop
Mode | RFC‑S
Minimum | 0.000 | Maximum | 500.000
Default | 25.000 | Units |
Type | 32 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 3
Coding | RW

AMC Position Control Loop Kp Gain (39.007) is the proportional gain with units of (User units/s) / User units. A AMC Position Control Loop Kp Gain (39.007) of unity and a AMC Position Error (39.008) of one User unit will give a position control loop speed of 1 User unit/s.

Parameter | 39.008 AMC Position Error
--- | ---
Short description | Shows the position error between the final position reference and the AMC slave position
Mode | RFC‑S
Minimum | −VM_AMC_POSITION | Maximum | VM_AMC_POSITION
Default |  | Units | UU
Type | 32 Bit Volatile | Update Rate | 4ms write
Display Format | Standard | Decimal Places | 0
Coding | RO, FI, VM, ND, NC, PT

AMC Position Error (39.008) gives the difference between the final position reference and the AMC Slave Position (33.004) in User units.

Parameter | 39.009 AMC Position Control Loop Speed Clamp
--- | ---
Short description | Defines the maximum speed output from the position control loop
Mode | RFC‑S
Minimum | 0.00 | Maximum | VM_AMC_SPEED_UNIPOLAR
Default | 109.20 | Units | UU/ms
Type | 32 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 2
Coding | RW, VM

The default value of 109.2 UU/ms is the equivalent of 100rpm for a feedback device with 16 normalised position bits per revolution and a user unit ratio of unity.

The AMC Position Control Loop Speed Clamp (39.009) defines the maximum positive or negative speed output from the position control loop in User units/ms.

Parameter | 39.010 AMC Speed Feed-forwards Gain
--- | ---
Short description | Defines the speed feed-forward gain
Mode | RFC‑S
Minimum | 0.000 | Maximum | 2.000
Default | 1.000 | Units |
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 3
Coding | RW

Normally the speed feed-forwards is used directly to provide the speed reference for the drive, with the position controller used as a trim to compensate for system and load effects to give the correct position. The default value of AMC Speed Feed-forwards Gain (39.010) is unity, but in some applications it may be necessary to reduce the speed feed-forward component to reduce overshoot.

Parameter | 39.011 AMC Output Speed Clamp
--- | ---
Short description | Defines the final speed clamp for the output speed from the AMC
Mode | RFC‑S
Minimum | −VM_SPEED_FREQ_REF | Maximum | VM_SPEED_FREQ_REF
Default | 1000.0 | Units |
Type | 32 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 1
Coding | RW, VM

AMC Output Speed Clamp (39.011) provides a final clamp on the output speed in drive speed parameter units (i.e. rpm or mm/s).

Parameter | 39.012 AMC Output Speed
--- | ---
Short description | Shows the final output speed from the AMC
Mode | RFC‑S
Minimum | −VM_SPEED_FREQ_REF | Maximum | VM_SPEED_FREQ_REF
Default |  | Units |
Type | 32 Bit Volatile | Update Rate | 4ms write
Display Format | Standard | Decimal Places | 1
Coding | RO, FI, VM, ND, NC, PT

AMC Output Speed (39.012) is the final output from the Advanced Motion Controller in 0.1rpm or 0.1mm/s. Although the update rate for this parameter is 4ms the output speed is written to the Hard Speed Reference (03.022) at the sample rate selected in AMC Rate Select (31.012) using an internal routing method. The output speed is written in internal units (232cpr/250μs) to increase the maximum speed resolution to 5.59e-5rpm or Pole Pitch x 9.31e-7mm/s. The value shown in Hard Speed Reference (03.022) will reflect the speed written by the internal routing method but will be updated at a slower rate than what the drive is actually using.

Parameter | 39.013 AMC Output Invert
--- | ---
Short description | Set to 1 to invert the AMC output speed
Mode | RFC‑S
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

If AMC Output Invert (39.013) = 1 then AMC Output Speed (39.012) and the output torque (AMC Inertia Compensation Mode (39.005) = 2) is inverted.

Parameter | 39.014 AMC External Acceleration Reference
--- | ---
Short description | Defines the external acceleration reference
Mode | RFC‑S
Minimum | −VM_AMC_RATE | Maximum | VM_AMC_RATE
Default | 0.000 | Units | UU/ms²
Type | 32 Bit Volatile | Update Rate | AMC sample rate read
Display Format | Standard | Decimal Places | 3
Coding | RW, VM

See AMC External Reference Select (39.001).

Parameter | 39.015 AMC External Reference Mode
--- | ---
Short description | Set to 1 to enable external reference mode. This mode of operation is intended to be used with an external motion controller.
Mode | RFC‑S
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

AMC External Reference Mode (39.015) can be used to modify the operation of the Advanced Motion Controller when an external profile generator is being used to provide the references for the position control loop. When an external profile is used it is important that the profile is always synchronised to AMC Slave Position (33.004) and the outputs of the profile are written to the external references before the drive is enabled. If this is not done the position error may cause the slave to move.

If AMC External Reference Mode (39.015) = 0 the external references are always used when selected (AMC External Reference Select (39.001) = 1) and no other changes are made to the operation of the Advanced Motion Controller.

If AMC External Reference Mode (39.015) = 1 the following apply when the external references are selected. This mode of operation is intended to be used with an external motion controller, such as the MCi option module.

1. The state machine described in AMC External Control State (39.016) is enabled. AMC External Control State (39.016) provides the state of the drive (unhealthy or disabled), indicates the active reference, the status of a homing routine and if an error has occurred, i.e. the stop reference has been selected while the external reference or homing routine was active, a limits has become active, etc. To synchronise the external profile with the slave position AMC External Control State (39.016) should be in one of the stopped states. In a stopped state the reference selector is set to stop and AMC Profile Input Position (38.006) = AMC Profile Output Position (38.008) which ensures that the external profile can be updated without introducing a position error when the external reference is activated.
2. The external references are not used when AMC Reference Select (34.007) is set to stop or home. This allows the on-board profile generator to perform a stop or homing routine without having to change AMC External Reference Select (39.001).
3. When the external references are being used the outputs of the on-board profile generator are set to the slave position, speed and acceleration. This allows the stop reference to be selected while the slave is moving and for a ramped stop to be performed.
4. AMC Reference Select (34.007) is set to stop when the drive is disabled. This ensures that the slave will be held at the slave position until the external profile is synchronised and is ready to provide the external reference.
5. AMC Profile Input Position (38.006) displays the rollover position when rollover mode is enabled (AMC Profile Output Position (38.008) > 0). This allows the external profile to be synchronised with the internal (AMC Profile Output Position (38.008)) and rollover (AMC Slave Position (33.004)) positions.
6. If a hardware or software limit is active and the output speed due to the position error or velocity feedforwards is towards the active limit AMC Output Speed (39.012) is set to zero and AMC Reference Select (34.007) is set to stop.

Parameter | 39.016 AMC External Control State
--- | ---
Short description | Shows the current state of the AMC when AMC external reference mode is enabled
Mode | RFC‑S
Minimum | 0 | Maximum | 17
Default |  | Units |
Type | 8 Bit Volatile | Update Rate | 4ms write
Display Format | Standard | Decimal Places | 0
Coding | RO, ND, NC, PT

AMC External Control State (39.016) shows the current state of the state machine shown in the diagram below. This state machine is active when AMC External Reference Mode (39.015) is set. See AMC External Reference Mode (39.015) for a description of how the state machine is used.