# Menu 3 − Speed Control and Position Feedback

Mode: RFC‑S

Parameter | 03.001 Final Speed Reference
--- | ---
Short description | Shows the reference at the input to the speed controller
Mode | RFC‑S
Minimum | −VM_SPEED | Maximum | VM_SPEED
Default |  | Units |
Type | 32 Bit Volatile | Update Rate | 4ms write
Display Format | Standard | Decimal Places | 1
Coding | RO, FI, VM, ND, NC, PT

Final Speed Reference (03.001) shows the reference at the input to the speed controller, which is the sum of the Post Ramp Reference (02.001) if the ramp output is not disabled and the hard speed reference (if enabled).

Parameter | 03.002 Speed Feedback
--- | ---
Short description | Displays the speed feedback from the selected feedback source
Mode | RFC‑S
Minimum | −VM_SPEED | Maximum | VM_SPEED
Default |  | Units |
Type | 32 Bit Volatile | Update Rate | 4ms write
Display Format | Standard | Decimal Places | 1
Coding | RO, FI, VM, ND, NC, PT

The speed feedback can be selected with Motor Control Feedback Select (03.026) to be taken from either of the drive position feedback interfaces or from a position feedback interface in a position feedback category option module. It is also possible to selected sensorless speed feedback with RFC Feedback Mode (03.024). Speed Feedback (03.002) shows the level of the speed feedback selected for the speed controller.

The FI attribute is set for this parameter, so display filtering is active when this parameter is viewed with one of the drive keypads. The value held in the drive parameter (accessible via comms or an option module) does not include this filter, but is a value that is obtained over a sliding 16ms period to limit the ripple. The speed feedback includes quantisation ripple given by the following equation in rpm:

> Ripple in Speed Feedback (03.002) = 60 / 16ms / Position resolution

The ripple for a linear system is given by the following equation in mm/s:

> Ripple in Speed Feedback (03.002) = Pole pitch in mm / 16ms / Position resolution

The position resolution for each type of feedback device is defined in the table below.

Position feedback device | Position resolution
AB, AB Servo | 4 x lines per revolution or pole pitch
FD, FR, FD Servo, FR Servo | 2 x lines per revolution or pole pitch
SC, SC Hiperface, SC EnDat, SC SSI, SC Servo | 1024 x sine waves per revolution or pole pitch
EnDat, SSI, BiSS | Comms bits per revolution or pole pitch
Resolver | See P1 Resolver Excitation (03.066)

For example the ripple in Speed Feedback (03.002) when a 4096 line AB type encoder is used is 0.23rpm. It should be noted that no filtering is applied to the speed feedback used by the speed controller or for the position feedback reference system unless the feedback filter for that particular interface is activated by putting a non-zero value in the appropriate set up parameter (i.e. P1 Feedback Filter (03.042) for the P1 drive position feedback interface). The diagram below shows the filtering applied to the speed feedback when this is taken from the P1 drive position feedback interface.

The speed feedback ripple seen by the speed controller and the position feedback reference is given by the following equations when the filter set up value P1 Feedback Filter (03.042) = 0.

> Ripple for a rotary system in rpm = 60 / Speed controller sample time / Position resolution

> Ripple for a linear system in mm/s = Pole pitch in mm / Speed controller sample time / Position resolution

The speed controller sample time is 250µs. If the filter set up value is non-zero the ripple is given by:

> Ripple for a rotary system in rpm = 60 / Filter time / Position resolution

> Ripple for a linear system in mm/s = Pole pitch in mm / Filter time / Position resolution

The description so far covers the P1 drive position feedback interface. Similar filtering is provided with the P2 drive position feedback interface and with position feedback interfaces in position feedback category option modules.

It is not advisable to use the speed feedback filter unless it is specifically required for high inertia applications with high controller gains, or if commutation signals alone are used for feedback, because the filter has a non-linear transfer function. It is preferable to use the current demand filters (Current Reference Filter 1 Time Constant (04.012) or Current Reference Filter 2 Time Constant (04.023)) as these are linear first order filters that provide filtering on noise generated from both the speed reference and the speed feedback. It should be noted that any filtering included within the speed controller feedback loop, either on the speed feedback or the current demand, introduces a delay and limits the maximum bandwidth of the controller for stable operation.

The speed ripple seen by the speed controller can be quite high in some cases, for example with a 4096 line encoder the speed ripple is 14.6rpm with a sample time of 250µs. This causes high frequency torque ripple and acoustic motor noise. These effects increase with the level of speed feedback ripple and with the gains used in the speed controller. Therefore high speed feedback ripple usually limits the maximum possible gain settings for the speed controller, and so a position feedback device with high position resolution is usually required for a system with high dynamic performance or stiffness. It should be noted that the ripple caused by feedback quantisation and does not define speed feedback resolution. The speed controller accumulates all pulses from the position feedback, and so the speed controller resolution is not limited by the feedback, but by the resolution of the speed reference.

Parameter | 03.003 Speed Error
--- | ---
Short description | Displays the difference betweent the Final Speed Reference and the Speed Feedback
Mode | RFC‑S
Minimum | −VM_SPEED | Maximum | VM_SPEED
Default |  | Units |
Type | 32 Bit Volatile | Update Rate | 4ms write
Display Format | Standard | Decimal Places | 1
Coding | RO, FI, VM, ND, NC, PT

The speed error is the difference between the final Final Speed Reference (03.001) and the Speed Feedback (03.002), and does not include the effect of the differential term in the speed controller feedback branch.

Parameter | 03.004 Speed Controller Output
--- | ---
Short description | Displays the output from the speed controller
Mode | RFC‑S
Minimum | −VM_TORQUE_CURRENT | Maximum | VM_TORQUE_CURRENT
Default |  | Units | %
Type | 16 Bit Volatile | Update Rate | 4ms write
Display Format | Standard | Decimal Places | 1
Coding | RO, FI, VM, ND, NC, PT

The output of the speed regulator is a torque demand given as a percentage of rated motor torque. It should be noted that this will be modified to take into account in the level of motor flux if field weakening is active before it is converted into the Final Current Reference (04.004).

Parameter | 03.005 Zero Speed Threshold
--- | ---
Short description | Set to the required zero speed threshold
Mode | RFC‑S
Minimum | 0 | Maximum | 200
Default | 5 | Units |
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, BU

If the Speed Feedback (03.002) is at or below the level defined by this parameter in either direction Zero Speed (10.003) = 1, otherwise Zero Speed (10.003) = 0.

Parameter | 03.006 At Speed Lower Limit
--- | ---
Short description | Set to the required minimum at speed threshold
Mode | RFC‑S
Minimum | 0 | Maximum | 33000
Default | 5 | Units |
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, BU

At Speed (10.006) is set if the Speed Feedback (03.002) is on the boundaries or within the at speed window. Above Set Speed (10.007) and Below Set Speed (10.005) are set if the feedback is above or below the window respectively.

If Absolute At Speed Select (03.009) = 0 reference window mode is used.
The "at speed" condition is true if,

> (|Pre-ramp Reference (01.003)| - At Speed Lower Limit (03.006)) ≤ |Speed Feedback (03.002)| ≤ (|Pre-ramp Reference (01.003)| + At Speed Upper Limit (03.007))

(If the lower limit is less than zero then zero is used as the lower limit.)

If Absolute At Speed Select (03.009) = 1 absolute window mode is used.
The "at speed" condition is true if,

> At Speed Lower Limit (03.006) ≤ |Speed Feedback (03.002)| ≤ At Speed Upper Limit (03.007)

Parameter | 03.007 At Speed Upper Limit
--- | ---
Short description | Set to the required maximum at speed threshold
Mode | RFC‑S
Minimum | 0 | Maximum | 33000
Default | 5 | Units |
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, BU

See At Speed Lower Limit (03.006).

Parameter | 03.008 Over Speed Threshold
--- | ---
Short description | Set to the required over speed threshold
Mode | RFC‑S
Minimum | 0 | Maximum | 40000
Default | 0 | Units |
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, BU

If Over Speed Threshold (03.008) is set to a non-zero value it defines the over speed threshold. If the Speed Feedback (03.002) exceeds this threshold in either direction an Over Speed trip is produced. If Over Speed Threshold (03.008) is set to 0.0 the threshold is based on the variable minimum/maximum for the references and is equal to 1.2 x VM_SPEED_FREQ_REF[MAX].

The motor speed and the motor voltage can be monitored to detect if the motor is accelerating in an uncontrolled way because the Position Feedback Phase Angle (03.025) has not been set up correctly. If the Over Speed Threshold (03.008) = 0 then position feedback phase angle error monitoring is enabled. If the Over Speed Threshold (03.008) is not equal to 0 this feature is disabled. It should be noted that phase angle error monitoring is not possible with high saliency motors, and so if Active Saliency Torque Mode (05.066) = 1 then phase angle error detection is suppressed.

As the over-speed trip provides the ultimate protection against against the motor operating beyond the maximum allowable speed, the trip function is time deterministic and will disable the drive within 4ms of the over-speed condition being detected. A phasing angle error can cause uncontrolled accerlation of the motor, but this condition is detected in the non-deterministic background task of the drive firmware. Also phase angle error detection is not avaialble with high saliency motors. Therefore the over-speed trip should be used as the ultimate protection against position feedback phase angle detection.

Parameter | 03.009 Absolute At Speed Select
--- | ---
Short description | Indicates when the motor is running at 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

See At Speed Lower Limit (03.006).

Parameter | 03.010 Speed Controller Proportional Gain Kp1
--- | ---
Short description | Defines the proportional gain for the speed controller
Mode | RFC‑S
Minimum | 0.0000 | Maximum | 200.0000
Default | 0.0100 | Units | s/rad
Type | 32 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 4
Coding | RW

The diagram below shows a generalised representation of the speed controller. The controller includes a feed forward proportional gain (Kp), a feed forward integral gain (Ki), and a differential feedback gain (Kd). The description here refers to the first set of gains for motor map 1 (Speed Controller Proportional Gain Kp1 (03.010), Speed Controller Integral Gain Ki1 (03.011) and Speed Controller Differential Feedback Gain Kd1 (03.012)). See Speed Controller Gain Select (03.016) on how to select a different set of gains.

Proportional gain (Kp) - Speed Controller Proportional Gain Kp1 (03.010)
If Kp is non-zero and Ki is zero the controller will only have a proportional term, and there must be a speed error to produce a torque reference. Therefore, as the motor load increases there will be a difference between the reference and actual speeds. This effect, called regulation, depends on the level of the proportional gain, the higher the gain the smaller the speed error for a given load. If the proportional gain is too high either the acoustic noise produced due to speed feedback quantisation becomes unacceptable, or the closed-loop stability limit is reached.

Integral gain (Ki) - Speed Controller Integral Gain Ki1 (03.011)
The integral gain is provided to prevent speed regulation. The error is accumulated over a period of time and used to produce the necessary torque reference without any speed error. Increasing the integral gain reduces the time taken for the speed to reach the correct level and increases the stiffness of the system, i.e. it reduces the positional displacement produced by applying a load torque to the motor. Unfortunately increasing the integral gain also reduces the system damping giving overshoot after a transient. For a given integral gain the damping can be improved by increasing the proportional gain. A compromise must be reached where the system response, stiffness and damping are all adequate for the application. The integral term is implemented in the form of ∑(Ki x error), and so the integral gain can be changed when the controller is active without causing large transients on the torque reference.

Differential gain (Kd) - Speed Controller Differential Feedback Gain Kd1 (03.012)
The differential gain is provided in the feedback of the speed controller to give additional damping. The differential term is implemented in a way that does not introduce excessive noise normally associated with this type of function. Increasing the differential term reduces the overshoot produced by under-damping, however for most applications the proportional and integral gains alone are sufficient. It should be noted that the differential term is limited internally so that it is ineffective if speed in rpm x Kd x Ki is greater than 170.

To analyse the performance of the speed controller it may be represented as an s-domain model as shown below.

Kc' is the conversion between the speed controller output and the torque producing current reference. A value of unity at the output of the speed controller gives a torque producing current equal to Kc'. The drive automatically compensates the torque producing current reference for flux variations in field weakening, and so Kc' can be assumed to have a constant value even in field weakening. Kc' = Full Scale Current Kc (11.061) x 0.45.

Kt is the torque constant of the motor (i.e. torque in Nm per amp of torque producing current). This value is normally available from the manufacturer for a permanent magnet motor, however, for induction motors the value must be calculated from the motor parameters. In RFC-A mode this calculation is performed by the drive and the result is stored in Torque Per Amp (05.032)

L(s) is the transfer function of the load.

The speed controller calculations are provided for a rotary application. However, for a linear application it is possible to set Torque Per Amp (05.032) to the force per amp and the Motor And Load Inertia (03.018) to the mass, and all the rotary system equations still apply.

It should be noted that the gain levels are compatible with those in Unidrive SP. The internal resolution of the intergral gain parameter is twice that of Unidrive SP. In most applications this makes no difference to the performance, however, with Unidrive SP the internal value is zero (the integral term disabled) if the user parameter is less than 0.05. In Unidrive M the internal integral gain would be zero if Speed Controller Integral Gain Ki1 (03.011) is less than 0.03. However, if Speed Controller Integral Gain Ki1 (03.011) is non-zero and less than 0.03 (i.e. 0.01 or 0.02) the internal value is one, so that the integral term remains active, unless the user deliberately disables this term by setting Speed Controller Integral Gain Ki1 (03.011) to zero.

Parameter | 03.011 Speed Controller Integral Gain Ki1
--- | ---
Short description | Defines the integral gain for the speed controller
Mode | RFC‑S
Minimum | 0.00 | Maximum | 655.35
Default | 0.05 | Units | s²/rad
Type | 16 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 2
Coding | RW, BU

See Speed Controller Proportional Gain Kp1 (03.010).

Parameter | 03.012 Speed Controller Differential Feedback Gain Kd1
--- | ---
Short description | Defines the differential gain for the speed controller
Mode | RFC‑S
Minimum | 0.00000 | Maximum | 0.65535
Default | 0.00000 | Units | 1/rad
Type | 16 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 5
Coding | RW, BU

See Speed Controller Proportional Gain Kp1 (03.010).

Parameter | 03.013 Speed Controller Proportional Gain Kp2
--- | ---
Short description | Defines the proportional gain for the 2nd speed controller
Mode | RFC‑S
Minimum | 0.0000 | Maximum | 200.0000
Default | 0.0100 | Units | s/rad
Type | 32 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 4
Coding | RW

See Speed Controller Proportional Gain Kp1 (03.010).

Parameter | 03.014 Speed Controller Integral Gain Ki2
--- | ---
Short description | Defines the integral gain for the 2nd speed controller
Mode | RFC‑S
Minimum | 0.00 | Maximum | 655.35
Default | 0.05 | Units | s²/rad
Type | 16 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 2
Coding | RW, BU

See Speed Controller Proportional Gain Kp1 (03.010).

Parameter | 03.015 Speed Controller Differential Feedback Gain Kd2
--- | ---
Short description |
Mode | RFC‑S
Minimum | 0.00000 | Maximum | 0.65535
Default | 0.00000 | Units | 1/rad
Type | 16 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 5
Coding | RW, BU

See Speed Controller Proportional Gain Kp1 (03.010).

Parameter | 03.016 Speed Controller Gain Select
--- | ---
Short description | Defines the differential gain for the 2nd speed controller
Mode | RFC‑S
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 0
Coding | RW

If Speed Controller Gain Select (03.016) = 0 then Kp1, Ki1 and Kd1 are used as the speed controller gains. These gains are given by Speed Controller Proportional Gain Kp1 (03.010), Speed Controller Integral Gain Ki1 (03.011) and Speed Controller Differential Feedback Gain Kd1 (03.012) if motor map 1 is selected (i.e. Select Motor 2 Parameters (11.045) = 0), or M2 Speed Controller Proportional Gain Kp1 (21.017), M2 Speed Controller Integral Gain Ki1 (21.018) and M2 Speed Controller Differential Feedback Gain Kd1 (21.019) if motor map 2 is selected (i.e. Select Motor 2 Parameters (11.045) = 1). If Speed Controller Gain Select (03.016) = 1 then Kp2, Ki2 and Kd2 are used as the speed controller gains. These gains are given by Speed Controller Proportional Gain Kp2 (03.013), Speed Controller Integral Gain Ki2 (03.014) and Speed Controller Differential Feedback Gain Kd2 (03.015). When Speed Controller Gain Select (03.016) is changed the gains are changed smoothly between the old and new values over a period of 250ms. This allows the system gains to be switched between two different sets of values without causing significant torque transients.

Parameter | 03.017 Speed Controller Set-up Method
--- | ---
Short description | Defines how the speed controller is set up
Mode | RFC‑S
Minimum | 0 | Maximum | 7
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | 1s read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | Disabled
1 | Bandwidth
2 | Comp Angle
3 | Kp Gain Times 16
4 | Low Performance
5 | Std Performance
6 | High Performance
7 | First Order

0: Disabled
When Speed Controller Set-up Method (03.017) is at its default value of 0, its functions are disabled and it has no effect.

1: Bandwidth set-up
If the load is predominantly a constant inertia and constant torque, the drive can calculate the required speed loop gain values, provided the Motor And Load Inertia (03.018) and the Torque Per Amp (05.032) are set-up correctly. If Speed Controller Set-up Method (03.017) = 1 the gain values are calculated to give the required Bandwidth (03.020) and Damping Factor (03.021). The calculated values for Kp and Ki are written to Speed Controller Proportional Gain Kp1 (03.010) and Speed Controller Integral Gain Ki1 (03.011) once per second. The Speed Controller Differential Feedback Gain Kd1 (03.012) is not affected. The gains are calculated from a linear model assuming a pure inertia load, not including unwanted delays in the speed and current controllers. The following equations are used by the drive to calculate the gains.

> Ki = J / (Kc' x Kt) x (2π x ωbw / Kbw)2

> Kp = 2 ξ √[ (Ki x J) / (Kc' x Kt) ]

where:
Kc' = Full Scale Current Kc (11.061) x 0.45
J = Motor And Load Inertia (03.018)
Kt = Torque Per Amp (05.032)
ωbw = Bandwidth (03.020)
ξ = Damping Factor (03.021)
Kwb = √[ (2ξ2 + 1) +√( (2ξ2 + 1)2 + 1) ]

2: Compliance angle set-up
If Speed Controller Set-up Method (03.017) = 2 the speed controller gains are set up based on the required Compliance Angle (03.019) and Damping Factor (03.021)
based on the following equations.

> Ki = 1 / αcomp(rs-1)

> Kp = 2 ξ √[ (Ki x J) / (Kc' x Kt) ]

where:
Kc' = Full Scale Current Kc (11.061) x 0.45
J = Motor And Load Inertia (03.018)
Kt = Torque Per Amp (05.032)
αcomp = Compliance Angle (03.019)
ξ = Damping Factor (03.021)

3: Kp gain times 16
If Speed Controller Set-up Method (03.017) = 3 the selected proportional gain used by the drive is multiplied by 16. This feature was provided in Unidrive SP because the range of the proportional gain parameters was limited. The range has now been increased to allow higher gains to be selected, and so this feature is no longer necessary, but is provided for compatibility with Unidrive SP. It should be noted that if this feature is used the value of gain used by the speed controller (i.e. Speed Controller Proportional Gain Kp1 (03.010) x 16) is limited internally to the maximum for Speed Controller Proportional Gain Kp1 (03.010).

4-6: Low, Standard or High performance
If Speed Controller Set-up Method (03.017) is set to a value from 4 to 6 the Speed Controller Proportional Gain Kp1 (03.010) and Speed Controller Integral Gain Ki1 (03.011) are automatically set up to give the bandwidths given in the table below and a damping factor of unity. These settings give low, standard or high performance.

Speed Controller Set-up Method (03.017) | Performance | Bandwidth
4 | Low | 5Hz
5 | Standard | 25Hz
6 | High | 100Hz

7: First order characteristic
If Speed Controller Set-up Method (03.017) = 7 then Speed Controller Proportional Gain Kp1 (03.010), Speed Controller Integral Gain Ki1 (03.011) and Speed Controller Differential Feedback Gain Kd1 (03.012) are set up to give a closed-loop speed controller response that approximates to a first order system with a transfer function of 1 / (sτ + 1), where τ = 1/ωbw and ωbw = 2π x Bandwidth (03.020). In this case the damping factor is meaningless, and Damping Factor (03.021) and Compliance Angle (03.019) have no effect. The following equations are used by the drive to calculate the gains.

> Ki = J / (Kc' x Kt) x (2π x ωbw / 2)2

> Kp = 2 √[ (Ki x J) / (Kc' x Kt) ]

> Kd = Kp / 4Ki

where:
Kc' = Full Scale Current Kc (11.061) x 0.45
J = Motor And Load Inertia (03.018)
Kt = Torque Per Amp (05.032)
ωbw = Bandwidth (03.020)

Parameter | 03.018 Motor And Load Inertia
--- | ---
Short description | Defines the inertia of the motor and the load for use in the speed controller
Mode | RFC‑S
Minimum | 0.00000 | Maximum | 1000.00000
Default | 0.00000 | Units | kgm²
Type | 32 Bit User Save | Update Rate | 1s read
Display Format | Standard | Decimal Places | 5
Coding | RW

The Motor And Load Inertia (03.018) represents the total inertia driven by the motor. This is used to set the speed controller gains (see Speed Controller Set-up Method (03.017)) and to provide torque feed forwards during acceleration when required (see Torque Mode Selector (04.011)).

It is possible to measure the inertia as part of the auto-tune process (see Auto-tune (05.012)).

Parameter | 03.019 Compliance Angle
--- | ---
Short description | Defines the required angular displacement when the drive delivers a torque producing current equivalent to Kc'
Mode | RFC‑S
Minimum | 0.0 | Maximum | 360.0
Default | 4.0 | Units | °
Type | 16 Bit User Save | Update Rate | 1s read
Display Format | Standard | Decimal Places | 1
Coding | RW

The Compliance Angle (03.019) is the required angular displacement when the drive delivers a torque producing current equivalent to Kc', i.e. Full Scale Current Kc (11.061) x 0.45, with no field weakening. The value of this parameter is used to automatically determine the speed controller gains if required. See Speed Controller Set-up Method (03.017).

Parameter | 03.020 Bandwidth
--- | ---
Short description | Defines the theoretical 3dB point on the closed-loop gain characteristic of the speed controller as a second order system
Mode | RFC‑S
Minimum | 5 | Maximum | 1000
Default | 10 | Units | Hz
Type | 16 Bit User Save | Update Rate | 1s read
Display Format | Standard | Decimal Places | 0
Coding | RW

The Bandwidth (03.020) is defined as the theoretical 3dB point on the closed-loop gain characteristic of the speed controller as a second order system. At this point the phase shift is approximately 60°. The value of Bandwidth (03.020) is used to automatically determine the speed controller gains if required. See Speed Controller Set-up Method (03.017).

Parameter | 03.021 Damping Factor
--- | ---
Short description | Defines the factor for the response of the system to a torque transient
Mode | RFC‑S
Minimum | 0.0 | Maximum | 10.0
Default | 1.0 | Units |
Type | 8 Bit User Save | Update Rate | 1s read
Display Format | Standard | Decimal Places | 1
Coding | RW

Damping Factor (03.021) defines this factor for the response of the system to a torque transient, and so if the Damping Factor (03.021) is unity, the response to a load torque transient is critically damped. The closed-loop step response of the speed controller gives approximately 10% overshoot with unity damping factor. Damping Factor (03.021) is used to automatically determine the speed controller gains if required. See Speed Controller Set-up Method (03.017).

Parameter | 03.022 Hard Speed Reference
--- | ---
Short description | Defines a reference value which does not pass through the ramp system
Mode | RFC‑S
Minimum | −VM_SPEED_FREQ_REF | Maximum | VM_SPEED_FREQ_REF
Default | 0.0 | Units |
Type | 32 Bit User Save | Update Rate | 250µs read
Display Format | Standard | Decimal Places | 1
Coding | RW, VM

The Hard Speed Reference (03.022) is a reference value which does not pass through the ramp system, but is added directly to the Post Ramp Reference (02.001).The Hard Speed Reference (03.022) is only added when selected by the Hard Speed Reference Select (03.023) and the Reference On (01.011) is active.

Parameter | 03.023 Hard Speed Reference Select
--- | ---
Short description | Set to 1 to enable the use of the hard speed reference
Mode | RFC‑S
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 0
Coding | RW

See Hard Speed Reference (03.022).

Parameter | 03.075 Initialise Position Feedback
--- | ---
Short description | Set to 1 to re-initialise any position feedback device connected
Mode | RFC‑S
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit Volatile | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, NC

If Initialise Position Feedback (03.075) is set to one any position feedback devices connected to the drive position feedback interfaces or any position feedback category option modules will be re-initialised.

Parameter | 03.076 Position Feedback Initialized
--- | ---
Short description | Indicates the initialisation state of position feedback devices connected
Mode | RFC‑S
Minimum | 0 (Display: 0000000000) | Maximum | 1023 (Display: 1111111111)
Default | 0 (Display: 0000000000) | Units |
Type | 16 Bit Volatile | Update Rate | Background write
Display Format | Binary | Decimal Places | 0
Coding | RO, NC, PT

Position Feedback Initialized (03.076) contains flags that represent the initialisation state of position feedback devices connected to the drive position feedback interfaces or position feedback interfaces on position feedback category option modules. One indicates that the interface is initialised and zero indicates that the interface is not initialised. The flags are assigned as shown below.

Bit | Position feedback interface
0 | P1 Drive
1 | P2 Drive
2 | P1 Option slot 1
3 | P2 Option slot 1
4 | P1 Option slot 2
5 | P2 Option slot 2
6 | P1 Option slot 3
7 | P2 Option slot 3
8 | P1 Option slot 4
9 | P2 Option slot 4

If no option module, or an option module other than a position feedback category module, is fitted in an option slot then the relevant flag is always set to one. If an attempt is made to enable the drive when any of the flags are zero the drive initiates an Encoder 7 trip. If a drive reset is initiated, the bits in Position Feedback Initialized (03.076) are checked, and if any position feedback devices are not initialised an attempt is made to initialise them.

The table below shows the initialisation process for different position feedback devices that can be connected to the drive.

Encoder types | Initialisation process
AB, FD, FR Resolver | None. Initialisation is immediate and is always successful. The position feedback is set to zero on initialisation.
AB Servo FD Servo FR Servo SC Servo | The absolute position used to control a motor can only be defined accurately after two different changes of state of the UVW commutation signals. Initialisation resets the system that ensures that the UVW signals alone will be used to define the motor position until the encoder has moved through two valid commutation signal state changes. Initialisation is immediate and is always successful. The position feedback is set to zero on initialisation.
SC | The SINCOS interpolation system must be initialised. Initialisation is immediate and is always successful. The position feedback is set to zero on initialisation.
SC Hiperface SC EnDat SC SSI | Auto-configuration if required except SC SSI. The absolute position must be obtained via comms. This may cause a large change in position feedback. The SINCOS interpolation system must be initialised. This may have a small effect on the position feedback.
EnDat BiSS SSI | Auto-configuration if required except SSI. The absolute position must be obtained via comms. This may cause a large change in position feedback.
SC SC | The absolute position used to control a motor is obtained from the sine and cosine signals provided for one revolution until the marker pulse occurs. The position obtained from the marker pulse is assumed to be a position of zero. Once a marker has occurred the incremental position is used and the single turn sine wave signals are ignored. When the position feedback device is initialised the single turn sine wave signals are used again until another marker event occurs. No part of the initialisation process affects the position feedback seen in parameters, except that the SINCOS interpolation system must be initialised which may have a small effect on the position feedback. Initialisation is immediate and is always successful.

Parameter | 03.078 Sensorless Mode Active
--- | ---
Short description |
Mode | RFC‑S
Minimum | 0 | Maximum | 1
Default |  | Units |
Type | 1 Bit Volatile | Update Rate | 4ms write
Display Format | Standard | Decimal Places | 0
Coding | RO, ND, NC, PT

If Sensorless Mode Active (03.078) = 0 it indicates that the position feedback selected with Motor Control Feedback Select (03.026) is being used for motor control. If Sensorless Sensorless Mode Active (03.078) = 1 it indicates that the sensorless algorithm is being used instead. See RFC Feedback Mode (03.024) for more information.

Parameter | 03.079 Sensorless mode filter
--- | ---
Short description | Sensorless mode filter
Mode | RFC‑S
Minimum | 0 | Maximum | 4
Default | 0 | Units | ms
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | 4
1 | 8
2 | 16
3 | 32
4 | 64

When sensorless mode is active the measured speed can include some ripple, which increases as the drive passes into field weakening. A filter is applied to the estimated speed and Sensorless mode filter (03.079) defines the time constant. The default time constant is 4ms, but this can be extended to improve the filtering. This is particularly useful when using standard ramp or spinning start with a low friction high inertia load, and can prevent over voltage trips when the drive has no braking resistor.

Parameter | 03.080 Sensorless Position
--- | ---
Short description |
Mode | RFC‑S
Minimum | -2147483648 | Maximum | 2147483647
Default |  | Units |
Type | 32 Bit Volatile | Update Rate | 4ms write
Display Format | Standard | Decimal Places | 0
Coding | RO, ND, NC, PT

Whether the drive is operating with or without position feedback Sensorless Position (03.080) gives the motor position where the least significant 16 bits represent a movement equivalent to one pole of the motor. The most significant 16 bits represent turns where one turn is the movement associate with one pole. For example in a rotary application with a 4 pole motor, the movement associated with one pole is a mechanical movement of 180°. In RFC-A mode Sensorless Position (03.080) is aligned with the motor flux and voltages, but this has no fixed relationship to the mechanical position of the rotor.