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+--- Thread: PID Thermostat - cooling mode (/showthread.php?tid=333)
PID Thermostat - cooling mode - hebeanflorin - 29.06.2016
I have a LM2 and I try to use the PID script:
http://openrb.com/example-pid-thermostat-with-lm2/
In heating mode it's work great but in cooling mode it's not working ( the value output =0)
Can you tell me what I need to do?
RE: PID Thermostat - cooling mode - admin - 29.06.2016
Try setting inverted = true on line 5.
RE: PID Thermostat - cooling mode - hebeanflorin - 29.06.2016
(29.06.2016, 07:19)admin Wrote: Try setting inverted = true on line 5.
Thks. I try this but the value output it's still =0.
RE: PID Thermostat - cooling mode - admin - 29.06.2016
Just did a quick simulation and it work correctly for cooling. Have you changed any of the gain values or any other parameters like min/max? Enabling inverted mode just sets all gains to be negative.
RE: PID Thermostat - cooling mode - hebeanflorin - 29.06.2016
I changed only the value for line 5, inverted=true. I still got the valuea output=0 (you can see in the picture attached).
The resident script that I use is this:
-- init pid algorithm
if not p then
p = PID:init({
inverted=true,
current = '10/1/3',
setpoint = '10/1/0',
output = '10/1/2'
})
end
-- run algorithm
p:run()
The script that I use is this:
PID = {
-- default params
defaults = {
-- invert algorithm, used for cooling
inverted = true,
-- minimum output value
min = 0,
-- maximum output value
max = 100,
-- proportional gain
kp = 1,
-- integral gain
ki = 1,
-- derivative gain
kd = 1,
}
}
-- PID init, returns new PID object
function PID:init(params)
local n = setmetatable({}, { __index = PID })
local k, v
-- set user parameters
n.params = params
-- copy parameters that are set by user
for k, v in pairs(PID.defaults) do
if n.params[ k ] == nil then
n.params[ k ] = v
end
end
-- reverse gains in inverted mode
if n.params.inverted then
n.params.kp = -n.params.kp
n.params.ki = -n.params.ki
n.params.kd = -n.params.kd
end
return n
end
-- resets algorithm on init or a switch back from manual mode
function PID:reset()
-- previous value
self.previous = grp.getvalue(self.params.current)
-- reset iterm
self.iterm = 0
-- last running time
self.lasttime = os.time()
-- clamp iterm
self:clampiterm()
end
-- clamps iterm value
function PID:clampiterm()
self.iterm = math.max(self.iterm, self.params.min)
self.iterm = math.min(self.iterm, self.params.max)
end
-- clamp and set new output value
function PID
etoutput()local t, object, value
self.output = math.max(self.output, self.params.min)
self.output = math.min(self.output, self.params.max)
value = math.floor(self.output)
local t = type(self.params.output)
-- write to output if object is set
if t == 'string' or t == 'table' then
if t == 'string' then
self.params.output = { self.params.output }
end
for _, output in ipairs(self.params.output) do
grp.write(output, value, dt.scale)
end
end
end
-- algorithm step, returns nil when disabled or no action is required, output value otherwise
function PID:run()
local result
-- get manual mode status
local manual = self.params.manual and grp.getvalue(self.params.manual) or false
-- in manual mode, do nothing
if manual then
self.running = false
-- not in manual, check if reset is required after switching on
elseif not self.running then
self:reset()
self.running = true
end
-- compute new value if not in manual mode
if self.running then
-- get time between previous and current call
local now = os.time()
self.deltatime = now - self.lasttime
self.lasttime = now
-- run if previous call was at least 1 second ago
if self.deltatime > 0 then
result = self:compute()
end
end
return result
end
-- computes new output value
function PID:compute()
local current, setpoint, deltasc, deltain, output
-- get input values
current = grp.getvalue(self.params.current)
setpoint = grp.getvalue(self.params.setpoint)
-- delta between setpoint and current
deltasc = setpoint - current
-- calculate new iterm
self.iterm = self.iterm + self.params.ki * self.deltatime * deltasc
self:clampiterm()
-- delta between current and previous value
deltain = current - self.previous
-- calculate output value
self.output = self.params.kp * deltasc + self.iterm
self.output = self.output - self.params.kd / self.deltatime * deltain
-- write to output
self
etoutput()-- save previous value
self.previous = current
return self.output
end
RE: PID Thermostat - cooling mode - admin - 29.06.2016
The same script is working correctly on my device. What sleep interval do you have set for PID resident script. Is there anything in the Error log tab?
RE: PID Thermostat - cooling mode - hebeanflorin - 29.06.2016
Sleep interval (seconds)=10
I have some errors in Error log Tab ( attached).
RE: PID Thermostat - cooling mode - admin - 29.06.2016
Looks like your PID user library has some errors, maybe you have deleted some code by accident?
RE: PID Thermostat - cooling mode - hebeanflorin - 29.06.2016
The code is the same with this: http://openrb.com/example-pid-thermostat-with-lm2/#codesyntax_1
I don't know if I need to copy this:
Usage
p = PID:init(parameters)
p:run()
I deleted all empty spaces and now it's working!