Menu 31 − AMC General Set-up

Mode: RFC‑S

System components

The diagram below shows the format and interface for the Advance Motion Controller.

The Advanced Motion Controller includes its own profile generator and combines the speed feed-forwards from the profile with the output of its position control loop to give a single speed reference in 0.1rpm or 0.1mm/s units. The conversion to the output speed is based on the set-up parameters of the position feedback selected to control the motor.

The Advanced Motion Controller is made up from the components shown in the diagram below. Individual menus are provided for each of the components.

Function Description
Master Position

The master position can be used as the input to the Cam or electronic gearbox functions and can be derived as follows:

From a position feedback interface in the drive or a position feedback interface in an option module.
As a speed (normally fixed) so that it can be used to create a time based profile.
As a user position value from a parameter.

Slave Position

The slave position is used as the feedback for the position control loop and can be derived as follows:

From a position feedback interface in the drive or a position feedback interface in an option module.
As a user position value from a parameter.

Reference selector The reference selector is used to select the input to the profile generator. In addition to the output from the Cam or electronic gearbox functions, a position or speed reference can be selected. The stop reference is a position that is constantly updated to provide a target when the system is to stop under the constraints of the profile generator. The homing system can provide a reference at the input to the profile generator during a homing routine.
Cam The Cam function uses a table to define the movement of the slave with respect to the master. The Cam table consists of a number of segments. Interpolation functions are provided to define the type of movement required by the slave within each segment.
Cam Table The Cam table is used by the Cam to define the required movement of the slave in response to the movement of the master.
Electronic gearbox The electronic gearbox allows the slave to be locked to the master including a gearbox ratio. The profile generator is used during the transition between the unlocked and locked states to control the acceleration of the slave.
Profile generator The input to the profile generator is a target that it attempts to attain within the required constraints. These constraints include the maximum linear acceleration/deceleration, jerk and speed. The target for the profile generator can be a position, a speed, or a position and a speed. The outputs of the profile generator include a speed that is used directly as a speed feed-forward term, acceleration that is used to derive the torque or acceleration feed-forward terms and a position that is used as the input to a position control loop.
Position control loop The position control loop modifies the motion controller output speed to correct the slave position and compensate for deviations from the required profile due to control system and load effects.
Homing system The homing system can move the slave under the constraints of the profile generator to find the home position. Once the home position is detected the system can be offset so that the required position is seen at the homing point.
Control and status The control and status system provides overall control for the motion controller and gives status information with a number of flags.

Position units

Position feedback from a drive or option module position feedback interface is given as a 32 bit signed value (normalised position) including the effect of the marker input for the interface (if relevant). The number of bits that represent turns (for a rotary position feedback device) or motor poles (for a linear position feedback device) can be selected for each position feedback device with a parameter in the set-up menu for that interface. Position is represented in the Advanced Motion Controller as a 32 bit signed value. Conversion ratios can be applied to the master position (AMC Master User Units Ratio Numerator (31.004) / AMC Master User Units Ratio Denominator (31.005)), the slave position (AMC Slave User Units Ratio Numerator (31.006) / AMC Slave User Units Ratio Denominator (31.007)) and the motion controller output (AMC Output User Units Ratio Numerator (31.008) / AMC Output User Units Ratio Denominator (31.009)). The slave position can be provided by the encoder used to control the motor or from an additional encoder attached to the load (i.e. dual loop configuration) as shown below.

The input ratios should be used to convert the normalised master and slave position to the required user units used for position within the motion controller and the output ratio should be setup to convert from user units to the normalised position units for the feedback device used to control the motor. If the slave feedback is derived from the position feedback used to control the motor the output ratio will be the inverse of the slave ratio. In a dual loop configuration the output ratio must be setup to correct for any differences between the configuration of the normalised units and the speed of the slave (load) and motor feedback, i.e. mechanical gearing. The conversion from position units to user units (input ratio) and from user units back into position units (output ratio) is demonstrated in the following examples. In these examples the parameter references refer to a feedback device connected to the drives P1 or P2 interface but any drive or option module interface can be used.    

Example 1 - Rotary encoder

Position feedback configuration and user units requirements:

The slave user units ratio can be setup to convert the 32 bit normalised position into 35.7μm units as follows:

AMC Slave User Units Ratio Numerator (31.006) = 107

AMC Slave User Units Ratio Denominator (31.007) = 216 x 357 = 23396352

The output ratio is the inverse of the input ratio:

AMC Output User Units Ratio Numerator (31.008) = 216 x 357 = 23396352 

AMC Output User Units Ratio Denominator (31.009) = 107

Example 2: Linear Encoder

Position feedback configuration and user units requirements:

The slave user units ratio can be setup to convert the 32 bit normalised position into 0.001mm units as follows:

AMC Slave User Units Ratio Numerator (31.006) = 107

AMC Slave User Units Ratio Denominator (31.007) = 230

The output ratio is the inverse of the input ratio:

AMC Output User Units Ratio Numerator (31.008) = 230

AMC Output User Units Ratio Denominator (31.009) = 107

Example 3 - Rotary encoders with different motor and slave feedback devices (i.e. dual loop configuration)

 Position feedback configuration and user units requirements:

The slave user units ratio can be setup to convert the 32 bit normalised position into 0.001 degree units as follows:

AMC Slave User Units Ratio Numerator (31.006) = 360000

AMC Slave User Units Ratio Denominator (31.007) = 220

In this example the output ratio is setup to convert from user units to the normalised position units for the motor feedback and must include the inverse of the gear ratio to ensure that the required output speed is seen at the slave feedback.

AMC Output User Units Ratio Numerator (31.008) = 216 x 16

AMC Output User Units Ratio Denominator (31.009) = 360000

 

Speed units

Speed parameters are 32 bit values specified in User units/ms with a range from -231 to 231-1. The speed parameters have two decimal places. If PosBits are the number of bits representing the number of counts per revolution for a rotary position feedback device then the speed resolution is calculated as follows:

Speed resolution  

= 0.01 user units/ms
= (0.01 / User units ratio) PosBits/ms 
= (0.01 / 2PosBits / User units ratio) revs/ms 
= (10 / 2PosBits / User units ratio) revs/s 
= (600 / 2PosBits / User units ratio) rpm

If PosBits are the number of bits representing the counts per pole pitch (PolePitch) for a linear feedback device then the speed resolution is calculated as follows:

Speed resolution  

= 0.01 user units/ms 
= (0.01 / User units ratio) PosBits/ms
= (0.01 / 2PosBits / User units ratio) poles/ms
= (0.01 x PolePitch / 2PosBits / User units ratio) mm/ms
= (10 x PolePitch / 2PosBits / User units ratio) mm/s

The speed resolution and the maximum speed can be calculated using the equations in the table below.

Speed Calculation Units
Resolution with rotary position feedback device (600 / 2PosBits) / User units ratio rpm
Maximum speed with rotary position feedback device Resolution x 231-1 rpm
Resolution with linear position feedback device (10 x PolePitch / 2PosBits) / User units ratio mm/s
Maximum speed with linear position feedback device Resolution x 231-1 mm/s

The resolution can be used to relate the parameter value to the speed of the position feedback device as follows.

Speed parameter value = Speed of position feedback device / Resolution

The table below shows the speed resolution and the maximum possible speed for a rotary application in rpm and for a linear application with a pole pitch of 50mm in mm/s with a user units ratio of unity. A user units ratio of more than unity will not change the resolution, but a user units ratio of less than unity will make the resolution coarser.

Turns bits Position bits Resolution (rpm) Maximum speed (rpm) Resolution (mm/s) Maximum speed (mm/s)
8 24 3.58x10-5 7.68x104 2.98x10-5 6.40x104
12 20 5.72x10-4 1.23x106 4.77x10-4 1.02x106
16 16 9.16x10-3 1.97x107 7.63x10-3 1.64x107
20 12 1.46x10-1 3.15x108 1.22x10-1 2.62x108
24 8 2.34 5.03x109 1.95 4.19x109

To allow the profile generator to work at the minimum acceleration (0.001 user units/ms/ms) the internal speed resolution used by the profile generator is defined by the minimum acceleration unit. When the profile generator is enabled (AMC Profile Disable (38.005) = 0) the maximum speed can be limited by the output of the profile generator. As above, the maximum profile speed is calculated from the speed resolution and the internal speed resolution of the profile generator is calculated as follows:

Profile speed resolution = Speed resolution / 10.24 x (1ms / AMC Rate Selected (31.013)) 

The table below shows the internal profile speed resolution and the maximum speed when AMC Rate Selected (31.013) = 250μs.

Turns bits Position bits Profile Internal Resolution (rpm) Profile Maximum Speed (rpm) Profile Internal Resolution (mm/s) Profile Maximum Speed (mm/s)
8 24 8.73x10-7 1.87x103 7.28x10-7 1.56x103
12 20 1.40x10-5 3.00x104 1.16x10-5 2.50x104
16 16 2.24x10-4 4.80x105 1.86x10-4 4.00x105
20 12 3.58x10-3 7.68x106 2.98x10-3 6.40x106
24 8 5.72x10-2 1.23x108 4.77x10-2 1.02x108

If a higher maximum profile speed is required the resolution can be decreased by using a user unit ratio less than unity or AMC Rate Selected (31.013) can be increased.


Acceleration units

Acceleration parameters are 32 bit values specified in User units/ms/ms with a range from 0 to 230 - 1. The acceleration parameters have 4 decimal places. If PosBits are the number of counts per revolution for a rotary position feedback device then the acceleration resolution is calculated as follows:

Acceleration resolution

= 0.001 user units/ms/ms
= (0.001 / User units ratio) PosBits/ms/ms 
= (0.001 / 2PosBits / User units ratio) revs/ms/ms 
= (1000 / 2PosBits / User units ratio) revs/s/s 
= (60000 / 2PosBits / User units ratio) rpm/s

If PosBits are the number bits representing the counts per pole pitch (PolePitch) for a linear feedback device then the acceleration resolution is calculated as follows:

Acceleration resolution

= 0.001 user units/ms/ms 
= (0.001 / User units ratio) PosBits/ms/ms
= (0.001 / 2PosBits / User units ratio) poles/ms/ms
= (0.001 x PolePitch / 2PosBits / User units ratio) mm/ms/ms
= (1000 x PolePitch / 2PosBits / User units ratio) mm/s2

The acceleration resolution and the maximum acceleration can be calculated using the equations in the table below.

Acceleration Calculation Units
Resolution with rotary position feedback device (60000 / 2PosBits) / User units ratio rpm/s
Maximum acceleration with rotary position feedback device Resolution x 230-1 rpm/s
Resolution with linear position feedback device (1000 x PolePitch / 2PosBits) / User units ratio mm/s2
Maximum acceleration with linear position feedback device Resolution x 230-1 mm/s2

The resolution can be used to relate the parameter value to the acceleration of the position feedback device as follows:

Acceleration parameter value = Acceleration of position feedback device / Resolution

The table below shows the minimum and maximum time that can be set up to acceleration from zero to 3000rpm for a rotary application and zero to 1m/s for a linear application with a user units ratio of unity. A user units ratio of more than unity will not change the resolution, but a user units ratio of less than unity will make the resolution coarser.

Turns bits Position bits Maximum acceleration time to 3000rpm (s) Minimum acceleration time to 3000rpm (s) Maximum acceleration time to 1ms-1 (s) Minimum acceleration time to 1ms-1 (s)
8 24 8.39x105 7.81x10-4 3.36x105 3.13x10-4
12 20 5.24x104 4.88x10-5 2.10x104

1.95x10-5

16 16 3.28x103 3.05x10-6 1.31x103 1.22x10-6
20 12 2.05x105 1.91x10-7 8.19x101 7.63x10-8
24 8 1.28x101 1.19x10-8

5.12

4.77x10-9