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import sys
import time
import pytest
from simple_pid import PID
def test_zero():
pid = PID(1, 1, 1, setpoint=0)
assert pid(0) == 0
def test_P():
pid = PID(1, 0, 0, setpoint=10, sample_time=None)
assert pid(0) == 10
assert pid(5) == 5
assert pid(-5) == 15
def test_P_negative_setpoint():
pid = PID(1, 0, 0, setpoint=-10, sample_time=None)
assert pid(0) == -10
assert pid(5) == -15
assert pid(-5) == -5
assert pid(-15) == 5
def test_I():
pid = PID(0, 10, 0, setpoint=10, sample_time=0.1)
time.sleep(0.1)
assert round(pid(0)) == 10.0 # Make sure we are close to expected value
time.sleep(0.1)
assert round(pid(0)) == 20.0
def test_I_negative_setpoint():
pid = PID(0, 10, 0, setpoint=-10, sample_time=0.1)
time.sleep(0.1)
assert round(pid(0)) == -10.0
time.sleep(0.1)
assert round(pid(0)) == -20.0
def test_D():
pid = PID(0, 0, 0.1, setpoint=10, sample_time=0.1)
# Should not compute derivative when there is no previous input (don't assume 0 as first input)
assert pid(0) == 0
time.sleep(0.1)
# Derivative is 0 when input is the same
assert pid(0) == 0
assert pid(0) == 0
time.sleep(0.1)
assert round(pid(5)) == -5
time.sleep(0.1)
assert round(pid(15)) == -10
def test_D_negative_setpoint():
pid = PID(0, 0, 0.1, setpoint=-10, sample_time=0.1)
time.sleep(0.1)
# Should not compute derivative when there is no previous input (don't assume 0 as first input)
assert pid(0) == 0
time.sleep(0.1)
# Derivative is 0 when input is the same
assert pid(0) == 0
assert pid(0) == 0
time.sleep(0.1)
assert round(pid(5)) == -5
time.sleep(0.1)
assert round(pid(-5)) == 10
time.sleep(0.1)
assert round(pid(-15)) == 10
def test_desired_state():
pid = PID(10, 5, 2, setpoint=10, sample_time=None)
# Should not make any adjustment when setpoint is achieved
assert pid(10) == 0
def test_output_limits():
pid = PID(100, 20, 40, setpoint=10, output_limits=(0, 100), sample_time=None)
time.sleep(0.1)
assert 0 <= pid(0) <= 100
time.sleep(0.1)
assert 0 <= pid(-100) <= 100
def test_sample_time():
pid = PID(setpoint=10, sample_time=10)
control = pid(0)
# Last value should be returned again
assert pid(100) == control
def test_time_fn():
pid = PID()
# Default time function should be time.monotonic, or time.time in older versions of Python
if sys.version_info < (3, 3):
assert pid.time_fn == time.time
else:
assert pid.time_fn == time.monotonic
i = 0
def time_function():
nonlocal i
i += 1
return i
pid.time_fn = time_function
for j in range(1, 5):
# Call pid a few times and verify that the time function above was used
pid(0)
assert pid._last_time == j
def test_time_fn_notime():
# Deliberately prevent the time module from being imported
import sys
sys.modules['time'] = None
with pytest.raises(ModuleNotFoundError):
# Must specify a time_fn if time is not available
_ = PID()
# We can still create a PID if we specify our own time_fn
_ = PID(time_fn=lambda: 0)
# Restore time module so the following tests can use it
sys.modules['time'] = time
def test_starting_output():
# If the PID is started with a system already at the setpoint, we can give it our best guess
# for which output it should start at
pid = PID(1, 0, 0, setpoint=10, starting_output=25)
assert pid(10) == 25
def test_auto_mode():
pid = PID(1, 0, 0, setpoint=10, sample_time=None)
# Ensure updates happen by default
assert pid(0) == 10
assert pid(5) == 5
# Ensure no new updates happen when auto mode is off
pid.auto_mode = False
assert pid(1) == 5
assert pid(7) == 5
# Should reset when reactivating
pid.auto_mode = True
assert pid._last_input is None
assert pid._integral == 0
assert pid(8) == 2
# Last update time should be reset to avoid huge dt
pid.auto_mode = False
time.sleep(1)
pid.auto_mode = True
assert pid.time_fn() - pid._last_time < 0.01
# Check that setting last_output works
pid.auto_mode = False
pid.set_auto_mode(True, last_output=10)
assert pid._integral == 10
def test_separate_components():
pid = PID(1, 0, 1, setpoint=10, sample_time=0.1)
assert pid(0) == 10
assert pid.components == (10, 0, 0)
time.sleep(0.1)
assert round(pid(5)) == -45
assert tuple(round(term) for term in pid.components) == (5, 0, -50)
def test_clamp():
from simple_pid.pid import _clamp
assert _clamp(None, (None, None)) is None
assert _clamp(None, (-10, 10)) is None
# No limits
assert _clamp(0, (None, None)) == 0
assert _clamp(100, (None, None)) == 100
assert _clamp(-100, (None, None)) == -100
# Only lower limit
assert _clamp(0, (0, None)) == 0
assert _clamp(100, (0, None)) == 100
assert _clamp(-100, (0, None)) == 0
# Only upper limit
assert _clamp(0, (None, 0)) == 0
assert _clamp(100, (None, 0)) == 0
assert _clamp(-100, (None, 0)) == -100
# Both limits
assert _clamp(0, (-10, 10)) == 0
assert _clamp(-10, (-10, 10)) == -10
assert _clamp(10, (-10, 10)) == 10
assert _clamp(-100, (-10, 10)) == -10
assert _clamp(100, (-10, 10)) == 10
def test_repr():
pid = PID(1, 2, 3, setpoint=10)
new_pid = eval(repr(pid))
assert new_pid.Kp == 1
assert new_pid.Ki == 2
assert new_pid.Kd == 3
assert new_pid.setpoint == 10
def test_converge_system():
pid = PID(1, 0.8, 0.04, setpoint=5, output_limits=(-5, 5))
pv = 0 # Process variable
def update_system(c, dt):
# Calculate a simple system model
return pv + c * dt - 1 * dt
start_time = time.time()
last_time = start_time
while time.time() - start_time < 120:
c = pid(pv)
pv = update_system(c, time.time() - last_time)
last_time = time.time()
# Check if system has converged
assert abs(pv - 5) < 0.1
def test_converge_diff_on_error():
pid = PID(1, 0.8, 0.04, setpoint=5, output_limits=(-5, 5), differential_on_measurement=False)
pv = 0 # Process variable
def update_system(c, dt):
# Calculate a simple system model
return pv + c * dt - 1 * dt
start_time = time.time()
last_time = start_time
while time.time() - start_time < 12:
c = pid(pv)
pv = update_system(c, time.time() - last_time)
last_time = time.time()
# Check if system has converged
assert abs(pv - 5) < 0.1
def test_error_map():
import math
def pi_clip(angle):
"""Transform the angle value to a [-pi, pi) range."""
if angle > 0:
if angle > math.pi:
return angle - 2 * math.pi
else:
if angle < -math.pi:
return angle + 2 * math.pi
return angle
sp = 0.0 # Setpoint
pv = 5.0 # Process variable
pid = PID(1, 0, 0, setpoint=0.0, sample_time=0.1, error_map=pi_clip)
# Check if error value is mapped by the function
assert pid(pv) == pi_clip(sp - pv)
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