Panasonic A6 Motor & Driver Instruction 3.1.4 Outline of mode — Full-closed Control Mode

Abstract

In this full-closed control, you can make a position control by using a external scale mounted externally which detects the position directly and feeds it back. With this control, you can control without being affected by the positional variation due to the ball screw error or temperature and you can expect to achieve a very high precision positioning in sub-micron order.

We recommend the external scale division ratio of 1/40 ≤ External scale division ration ≤ 1280

Cautions on Full-Closed Control

1. Enter the command pulses making the external scale as a reference.
   If the command pulses do not match to the external scale pulses, use the command divivion/multiplication function (Pr0.09 to Pr0.10) and setup so that the command pulses after division/multiplication is based on the external scale reference.
2. The A5 series supports the external scale of A- and B-phase output type and serial communication type. Initialize the parameters according to the following procedures and write to EEPROM and turn on power.
3. When using a scale of A- and B- phase output type, correctly connect it so that the totating direction of the motor (CW/CCW) and A-phase and B-phase of the external scale have the following relationship.
   

<How to make an initial setup of parameters related to external scale>

1. Turn on the power after checking the wiring.
2. Check the values (initial) feedback pulse sum and external feedback pulse sum with the front panel.
3. Move the work and check the travel from the initial values of the above (2).
4. If the travel of the feedback pulse sum and the external scale feedback pulse sum are reversed in positive and negative, set up the reversal of external scale direction (Pr3.26) to 1.
5. Set up the external scale division ratio Pr3.24/Pr3.25 based on the design values.
   External scale division ratio = (Encoder resolution per motor revolution [pulse])/(External scale's resolution per motor revolution [pulse]) = Pr3.24/Pr3.25
   If a wrong scale is applied, difference between the position calculated by using encoder feedback pulses and the position calculated by using external scale pulses as moving distance increases: Larger difference will cause excessive deviation error protect.
6. Set up appropriate value of hybrid deviation excess (Pr3.28) in command unit, in order to avoid the damage to the machine.
   * A6-sereies driver calculates the difference between the encoder position and the external scale position as hybrid deviation, and is used to prevent the machine runaway or damage in case of the external scale breakdown or when the motor and the load is disconnected.
   If the hybrid deviation excess range is too wide, detection of the breakdown or the disconnection will be delayed and error detection effect will be lost. If this is too narrow, it may detect the normal distortion between the motor and the machine under normal operation as an error.
   *When the external scale division ration is not correct, hybrid deviation excess error (Err25.0) may occur especially when the work travels long distance, even though the external scale and the motor position matches.
   In this case, widen the hybrid deviation excess range by matching the external sscale division ratio to the closest value.

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Related page → •P.3-19 "Control Block Diagram" • P.3-22 "Wiring Diagram to the connector, X4" • P.3-35 "Inputs and outputs on connector X4" • P.4-6 to P.4-85 "Details of parameter"

(1) Selection of external scale type

Select the type of external scale to be used.

• Relevant parameters

Parameter No.	Title	Range	Function
Pr3.18	External scale selection	0 to 6	Select the type of external scale.
Pr3.26	Reversal of direction of external scale	0 to 3	Reverse the direction of external scale, feedback counter.

Note → For details of these parameters, refer to P.4-6 to P.4-85 "Details of parameter".

(2) Setup of external scale division ratio

Set up the division ratio of encoder resolution and external scale resolution.

• Relevant parameters

Parameter No.	Title	Range	Function
Pr3.24	Numberator of external scalel division	0 to 223	Set up the numerator of the external scale dividing setup.
Pr3.25	Denominator of external scale division	0 to 223	Set up the Denominator of the external scale dividing setup.

Note → For details of these parameters, refer to P.4-6 to P.4-85 "Details of parameter".

(3) Setup of hybrid excessive deviation

This function detects the positional difference between the motor (encoder) and load (external scale) and enables the hybrid excessive deviation protection if the differene exceeds Pr3.28 "Hybrid excessive deviation setup".
Hybrid excessive deviation is mainly caused by feedback scale error, wrong connection and loose connection between the motor and load.

• Relevant parameters

Parameter No.	Title	Range	Function
Pr3.28	Hybrid deviation excess setup	1 to 227	You can setup the permissible gap (hybrid deviation) between the present motor position and the present external scale position.
Pr3.29	Hybrid deviation clear setup	0 to 100	As the motor turns the number of revolutions set by this parameter, the hybrid deviation is cleared to 0.

Note → For details of these parameters, refer to P.4-6 to P.4-85 "Details of parameter".