Algorithm 3 - Proportional Integral

This algorithm is an implementation of a typical PI algorithm.

$$ValveOpening [\%] = Kp * e + Ki*\sum_{}^{}e$$

Both the proportional gain Kp and the integral gain Ki can be set with 5 decimal places after the comma.

The algorithm will run on 3 occasions:

- Periodic run (by default every 10 minutes)

- New target temperature is set

- T(measured) - T(target) > 2 degrees Celsius

$$Integral = \sum_{}^{}e$$

There's a software hysteresis in place, which prevents the movement of the motor unless the error is > Thys.

The implementation does not have integral reset time - it integrates all previous errors. There's an integral anti wind-up and anti wind-down in place, which limits the integral to 0-50 degrees by default. You can change the maximum value via the command below, increasing the error limit.

Maximum allowed Integral value

SET

Byte Index	Byte value - meaning
Byte Index	Byte value - meaning
0	4C - The command code
1	XX - I[15:8]
2	XX -I[7:0]

Example command: 0x4C012C

I[15:0] = 012C[HEX] = 300

Integral = I[DEC] / 10 = 300 / 10 = 30

The error is set to its maximum allowed value of 30°C

Default: I[15:0] = 01F4[HEX] = 500[DEC] = 50°C

GET

Byte index	Sent request	Response - Meaning
0	4D – The command code.	4D – The command code.
1		XX - I[15:8]
2		XX -I[7:0]

Example command response: 0x4D03E8

I[15:0] = 03E8[HEX] = 1000

Integral = I[DEC] / 10 = 1000 / 10 = 100

The error is set to its maximum allowed value of 100°C

Default: I[15:0] = 01F4[HEX] = 50[DEC] = 50°C

Proportional gain - Kp

SET

Byte Index	Byte value - meaning
Byte Index	Byte value - meaning
0	37 - The command code
1	A[23:16]
2	A[15:8]
3	A[7:0]
	A[23:0] = Kp * 131072 (default value Kp = 6)

Example downlink: Setting Kp to 2.74688: 37 05 7E 67

2.74688*131072 = 360039 = 0x05 7E 67

GET

Byte index	Sent request	Response - Meaning
0	36 – The command code.	36 – The command code.
1		A[23:16]
2		A[15:8]
3		A[7:0]
		Kp = A[23:0]/131072

Uplink example: 0x36123456

A[23:0] = 0x123456 = 1193046

Kp = 1193046 / 131072 = 9.1

Integral gain - Ki

SET

Byte Index	Byte value - meaning
0	3E - The command code
1	B[23:16]
2	B[15:8]
3	B[7:0]
	B[23:0] = Ki * 131072 (default value: Ki = 1)

Example downlink: Setting Ki to 0.412678: 3E 00 D3 4A 0.412678*131072 = 54090 = 0x00D34A

GET

Byte index	Sent request	Response - Meaning
0	3D – The command code.	3D – The command code.
1		B[23:16]
2		B[15:8]
3		B[7:0]
		Ki = B[23:0]/131072

Example uplink: 0x3D112233

B[23:0] = 0x112233 = 1122867

Ki = 1122867/131072 = 8.57

Get the value of the integral

Byte index	Sent request	Response - Meaning
0	3F – The command code.	3F – The command code.
1		Integral [15:8]
2		Integral [7:0]

The value of the integral is pre-multiplied by 10 by the device, so it can use 0,1 resolution.

Example uplink:

If the integral is 2.5, the complete command response is going to be: 0x3F0019

Integral [15:0] = 0x0019 = 25

Integral = 25/10 = 2.5

PI run period

SET

Byte Index	Byte value - meaning
0	41 - The command code
1	XX = Run period in minutes. (default value: 10 minutes)

Example downlink:

0x410F - sets the run period to 15 minutes.

GET

Byte index	Sent request	Response - Meaning
0	40 – The command code.	40 – The command code.
1		XX - Run period in minutes.

Example uplink:

0x400B - the run period is 11 minutes

Temperature hysteresis (Thys)

SET

Byte Index	Byte value - meaning
0	43 - The command code
1	XX = Temperature hysteresis value (Thys), multiplied by 10. (default value: 0.2 deg. C)

Min. acceptable value of Thys is 0.2C

Example downlink:

0x4303 - sets the temperature hysteresis to 0.3 degrees Celsius.

GET

Byte index	Sent request	Response - Meaning
0	42 – The command code.	42 – The command code.
1		XX - Temperature hysteresis value, multiplied by 10.

Example uplink:

0x42FF - The temperature hysteresis is 1.6 degrees Celsius.