UM0289

ST10 firmware

21/29

4.2

Control algorithm

Communication layer after the reception and checking of a complete frame puts the

microcontroller in an execution state in which the right control layer function is involved.

The management of open loop signals is executed with functions that directly act in the

register of PWM signals or through the pins for the right generation of connector signals.

Closed loop operations, are instead managed through three independent ISR where the

reload timing depends on the closed loop time of the specific control.

The speed reference is expressed in terms of encoder pulses, counted in the closed loop

timing imposed, so each ISR works with the actual values of encoder inputs and with PWM

duty cycles to perform a PID action for reach the right value of encoder reference.

Figure 12.

Algorithm block diagram

Figure 12 shows how the two modules interact (through shared memory) to perform

eMotion operations.

The PID algorithm implemented is approximated with the following formula:

Set PWM% to 22% for 6235 driver on connector 2

08-02-2A-16-4A

Set 2ms of control loop time for a 6205 driver on connector 2

0A-02-2B-05-3C

Set control for a DC motor with a 1024/revolution encoder,

connected to the first connector. Set the speed reference to 100

rpm with control parameters of P=0.04,I=0.02,D=0.01

09-0C-1B-CD-04-00-00-64-00-04-

00-02-00-01-6D

Receive the parameters of connector 3 with a BLDC motor with

500/revolution encoder controlled at 200 rpm with P=0.60,

I=0.02,D=0.00 and control loop of 1.2 ms. With actual PWM

signal 10% / 22 Khz

40-0F-3A-01-F4-00-0A-16-02-01-

00-C8-00-3C-00-02-00-00-A9

Frame Description

Value (Hex)

Communication

Layer

Shared

memory

Control

Layer

SERIAL BUFFER

T

n

e

n

e

D

T

k

e

I

n

e

P

n

u

n

K

)

1

(

)

(

)

(

)

(

)

(

1

−

−

⋅

+

⋅

⋅

⋅

+

⋅

=

∑

=