Created
March 4, 2018 22:48
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Kerbal Space Program Hovering PID Controller
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import krpc, time, math | |
conn = krpc.connect(name = "PID Hover") | |
vessel = conn.space_center.active_vessel | |
# Find the craft height (altitude from command module and bottom of craft are different) | |
bbox = vessel.bounding_box(vessel.reference_frame) | |
HEIGHT = max(abs(bbox[0][1]), abs(bbox[1][1])) | |
print("Now controlling '" + vessel.name + "'") | |
# We need this for later | |
surf_frame = vessel.orbit.body.reference_frame | |
# Some program constants | |
RATE = 0.1 | |
TGT_ALT = 100 - HEIGHT / 2 | |
# PID constants | |
K_C = 0.25 | |
K_P = -0.03 | |
K_I = 0.01 | |
K_D = -5.5 | |
# The integral and differential component data | |
prev_err = [] | |
prev_alt = vessel.flight().surface_altitude | |
vessel.auto_pilot.engage() | |
timer = 0 | |
while True: | |
# Ensure we're pointing upwards | |
vessel.auto_pilot.target_direction = (1, 0, 0) | |
alt = vessel.flight().surface_altitude | |
# Calculate the PID components | |
integral = sum(prev_err) * RATE | |
proportion = alt - TGT_ALT | |
differential = (alt - prev_alt) * RATE | |
# Sum the components and set the craft throttle | |
throttle = K_C + K_P * proportion + K_I * integral + K_D * differential | |
vessel.control.throttle = throttle | |
# Keep pushing / pulling the integral buffer | |
prev_err.append(alt - TGT_ALT) | |
if len(prev_err) > 1 / RATE: | |
prev_err = prev_err[1:] | |
prev_alt = alt | |
time.sleep(RATE) | |
# Print only occasionally | |
if timer == 10: | |
print("Throttle = " + str(throttle) + "(P = " + str(K_P * proportion) + ", I = " + str(K_I * integral) + ", D = " + str(K_D * differential) + ")") | |
timer = 0 | |
else: | |
timer += 1 |
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