Temperature Control

Vicki has an internal temperature control algorithms that allows it to intelligently adjust the valve openness in order to reach the target temperature and remain within as close a proximity of it as possible. The main algorithm that is utilized is the Proportionate integral (PI) control algorithms.

This algorithm is the newest and most optimized one available for Vicki devices and is the only one available for firmware >=4.3.

Other algorithms are available for older firmware versions, you can find information on them in the Deprecated temperature control algorithms page.

Proportionate Integral (PI) Control Algorithm

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] = 0x012C = 300

Integral = I / 10 = 300 / 10 = 30

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

Default: I[15:0] = 0x01F4 = 500 = 50°C

GET

Proportional gain - Kp

SET

Byte Index	Byte value - meaning
Byte Index	Byte value - meaning
0	37 - The command code
1	XX[23:16]
2	XX[15:8]
3	XX[7:0]
	XX[23:0] = Kp * 131072 Default: 0x0C0000= 786432 -> Kp = 6

Example command: Setting Kp to 2.74688: 37057E67

2.74688*131072 = 360039 = 0x057E67

GET

Integral gain - Ki

SET

Byte Index	Byte value - meaning
0	3E - The command code
1	XX[23:16]
2	XX[15:8]
3	XX[7:0]
	XX[23:0] = Ki * 131072 Default: 0x020000 = 131072 -> Kpi = 1

Example command: Setting Ki to 0.412678: 0x3E00D34A 0.412678*131072 = 54090 = 0x00D34A

GET

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 command: 0x3F

Example response: 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 command: 0x410F - sets the run period to 15 minutes.

GET

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 for f.w. ≥ 4.6 - 0 deg. C)

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

GET

The is no minimum limit for Thys (it can have a 0 value).

The maximum allowed values is 100, which corresponds to 10 degrees.