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Adds and modifies scripts for determining RPM & stroke

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This commit is contained in:
Patrick McDonagh
2017-04-27 17:16:44 -05:00
parent 269dacb0dc
commit 79549bb499
3 changed files with 257 additions and 76 deletions
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57
calc_spm_ramp.py Normal file
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"""Calculate the time for each stroke and then the SPM."""
nameplate_hz = 120.0
nameplate_rpm = 1200.0
approach_freq = 20
total_stroke_length = 60
offset_top = 2
offset_bottom = 2
accel_time = 2.0
decel_time = 2.0
thread_pitch = 0.5906
def time_for_freq_change(freq_delta, np_hz, ramp_time):
"""Calculate the time required for a frequency change."""
return (freq_delta / np_hz) * ramp_time
def dist_for_freq_change(freq_delta, ramp_time, np_hz, np_rpm, thread_pitch):
"""Calculate the distance required for a frequency change."""
time_required = time_for_freq_change(freq_delta, np_hz, ramp_time)
return 0.75 * freq_delta * (np_rpm / np_hz) * (1.0 / 60.0) * time_required * thread_pitch
def time_for_uniform_freq(freq, distance, np_hz, np_rpm, thread_pitch):
"""Calculate the time required to move a distance at a frequency."""
return distance / (freq * (np_rpm / np_hz) * (1.0 / 60.0) * thread_pitch)
def calculate_stroke_time(stroke_length, upper_offset, lower_offset, run_frequency, ramp_frequency, accel_time, decel_time):
"""Calculate the time it takes to make a full stroke."""
ramp_up_time = time_for_freq_change(run_frequency, nameplate_hz, accel_time)
ramp_up_dist = dist_for_freq_change(run_frequency, accel_time, nameplate_hz, nameplate_rpm, thread_pitch)
ramp_down_time = time_for_freq_change(run_frequency - ramp_frequency, nameplate_hz, decel_time)
ramp_down_dist = dist_for_freq_change(run_frequency - ramp_frequency, decel_time, nameplate_hz, nameplate_rpm, thread_pitch)
turn_time = time_for_freq_change(ramp_frequency, nameplate_hz, decel_time)
turn_dist = dist_for_freq_change(ramp_frequency, decel_time, nameplate_hz, nameplate_rpm, thread_pitch)
run_dist = total_stroke_length - (offset_bottom + offset_top + ramp_up_dist + ramp_down_dist + turn_dist)
run_time = time_for_uniform_freq(run_frequency, run_dist, nameplate_hz, nameplate_rpm, thread_pitch)
stroke_time = 2.0 * (ramp_up_time + run_time + ramp_down_time + turn_time)
return stroke_time
for ramp_i in [0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0]:
print("-----")
print("Ramp Rate: {}".format(ramp_i))
for hz_i in [20.0, 30.0, 40.0, 50.0, 60.0, 70.0, 80.0, 90.0, 100.0, 110.0, 120.0]:
spm = 60 / calculate_stroke_time(total_stroke_length, offset_top, offset_bottom, hz_i, approach_freq, ramp_i, ramp_i)
print("Freq: {} Hz., SPM: {}".format(hz_i, spm))

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pid_testing.py Normal file
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"""
Sample PID calculations.
Tests the algorithm for updating output frequency based on the current SPM.
"""
import matplotlib.pyplot as plt
# Nameplate
nameplate_hz = 120.0
nameplate_rpm = 1200.0
# Setpoints
starting_hz = 20.0
spm_target = 4.0
pid_ramp_limit_large = 1.0
pid_ramp_limit_small = 0.2
pid_ramp_hz_large = 5.0
pid_ramp_hz_small = 1.0
hz_setpoint = starting_hz
def stroke(last_stroke_spm):
"""
Calculate the new output frequency.
Input Parameters:
last_stroke_spm: last strokes SPM
"""
global hz_setpoint, spm_target
error = abs(spm_target - last_stroke_spm)
error_sign = 1 if (spm_target > last_stroke_spm) else -1
if error >= pid_ramp_limit_large:
print("Large change")
hz_setpoint += error_sign * pid_ramp_hz_large
elif error >= pid_ramp_limit_small:
print("Small change")
hz_setpoint += error_sign * pid_ramp_hz_small
return hz_setpoint
def loop():
"""Loop and calculate."""
new_spm = 1.0
spm_arr = []
rpm_arr = []
while new_spm != 0.0:
new_spm = float(raw_input("New SPM: "))
hz_sp = stroke(new_spm)
new_rpm = (nameplate_rpm / nameplate_hz) * hz_sp
spm_arr.append(new_spm)
rpm_arr.append(new_rpm)
print("{} SPM, {} RPM".format(new_spm, new_rpm))
fig, ax1 = plt.subplots()
ax1.plot(spm_arr, "b-")
ax1.set_ylabel("SPM", color="b")
ax2 = ax1.twinx()
ax2.plot(rpm_arr, "r-")
ax2.set_ylabel("RPM", color="r")
fig.tight_layout()
plt.show()
loop()

206
speed_testing.py
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from time import sleep
from datetime import datetime
"""Simulates speed testing."""
import matplotlib.pyplot as plt
from time import sleep
from math import ceil
rpm = 200
dt = 0.010 #seconds
dt = 0.050 # seconds
thread_pitch = 0.5906
accel_time = 2 # seconds
decel_time = 2 # seconds
run_speed = 240.0 # Hz
rampdown_speed = 20.0 # Hz
accel_time = 2.0 # seconds
decel_time = 2.0 # seconds
stroke_length = 60 # inches
upper_offset = 9 # inches
lower_offset = 15 # inches
upper_offset = 2 # inches
lower_offset = 2 # inches
motor_full_speed = 120 # Hz
motor_full_speed_hz = 120 # Hz
motor_full_speed_rpm = 1200 # RPM
def ramp_up(i):
speed = (rpm / ramp_time) * (i * dt)
return speed
def sim(run_freq, approach_freq, stroke_limit):
"""Run the main simulation loop."""
strokes = 0
def ramp_distance_sim(rpm, ramp_time):
time_to_rampdown = ((run_freq - rampdown_speed) / motor_full_speed_hz) * decel_time
print("Rampdown Time: {} s.".format(time_to_rampdown))
distance_to_rampdown = 0.75 * (run_freq - rampdown_speed) * (motor_full_speed_rpm / motor_full_speed_hz) * (1.0 / 60.0) * time_to_rampdown * 0.5906
print("Rampdown Distance: {} in.".format(distance_to_rampdown))
time_to_turnaround = (rampdown_speed / motor_full_speed_hz) * decel_time
print("Turn Time: {} s.".format(time_to_turnaround))
distance_to_turnaround = 0.75 * rampdown_speed * (motor_full_speed_rpm / motor_full_speed_hz) * (1.0 / 60.0) * time_to_turnaround * 0.5906
print("Turn Distance: {} in.".format(distance_to_turnaround))
upper_rampdown_target = stroke_length - (upper_offset + distance_to_rampdown)
upper_turnaround_target = stroke_length - (upper_offset + distance_to_turnaround)
upper_offset_target = stroke_length - upper_offset
lower_rampdown_target = lower_offset + distance_to_rampdown
lower_turnaround_target = lower_offset + distance_to_turnaround
print("--")
print("Targets")
print("Lower Offset: {} in.".format(lower_offset))
print("Upper Rampdown Target: {} in.".format(upper_rampdown_target))
print("Turnaround Target: {} in.".format(upper_turnaround_target))
print("Upper Offset: {} in.".format(upper_offset_target))
print("Lower Rampdown Target: {} in.".format(lower_rampdown_target))
print("Lower Turnaround Target: {} in.".format(lower_turnaround_target))
print("--")
position = lower_offset
time = 0.0
dist = 0.0
while time < ramp_time:
speed = (rpm / ramp_time) * time
dist += speed * dt * (1.0 / 60.0) * thread_pitch
time += dt
return dist
def get_ramp_constants(full_speed, accel_time, decel_time):
up_m = full_speed / accel_time
up_b = 0
direction = 1
starting_speed = 0.0 # Hz
speed = starting_speed
last_speed = speed
down_m = -1.0 * full_speed / decel_time
down_b = full_speed
return (up_m, up_b, down_m, down_b)
def strokes(num):
stroke_i = 0
position = 0.0
speed = 0.0
time = 0.0
(ramp_up_slope, ramp_up_intercept, ramp_down_slope, ramp_down_intercept) = get_ramp_constants(motor_full_speed, accel_time, decel_time)
while stroke_i < num:
while position < (stroke_length - upper_offset):
if speed <
stroke_i += 1
def calc_ramp_distance(rpm, ramp_time):
global thread_pitch
return 0.5 * (ramp_time / 60.0) * rpm * thread_pitch
def sim():
speed_array = []
distance_array = []
position_array = []
time_array = []
stroke_part = -1
distance_travelled = 0
start = datetime.now()
accel_index = 0
decel_index = 0
speed = 0
while strokes != stroke_limit:
last_speed = speed
if direction == 1:
if position < upper_rampdown_target:
# below offset and rampdown distance, ramp up to setpoint, then run at setpoint
if stroke_part != 0:
stroke_part = 0
print("{} - {}".format(stroke_part, position))
if speed < run_freq:
speed += (motor_full_speed_hz / accel_time) * dt
if speed > run_freq:
speed = run_freq
elif position >= upper_rampdown_target and position < upper_turnaround_target:
# between rampdown distance and turnaround distance, ramp to rampdown speed, then run at rampdown speed
if stroke_part != 1:
stroke_part = 1
print("{} - {}".format(stroke_part, position))
if speed > rampdown_speed:
speed += -1.0 * (motor_full_speed_hz / decel_time) * dt
elif position >= upper_turnaround_target:
# above turnaround distance, ramp to 0 and change direction
if stroke_part != 2:
stroke_part = 2
print("{} - {}".format(stroke_part, position))
if speed > 0:
speed += -1.0 * (motor_full_speed_hz / decel_time) * dt
if speed <= 0:
speed = 0
direction = -1
accel_distance = calc_ramp_distance(rpm, accel_time)
decel_distance = calc_ramp_distance(rpm, decel_time)
while distance_travelled < stroke_length:
if distance_travelled < accel_distance:
speed = (rpm / accel_time) * (accel_index * dt)
accel_index += 1
elif distance_travelled < (stroke_length - decel_distance):
speed = rpm
else:
speed = -1 * (rpm / decel_time) * (decel_index * dt) + rpm
decel_index += 1
delta_x = speed * (dt / 60.0) * thread_pitch
distance_travelled += delta_x
speed_array.append(speed)
distance_array.append(distance_travelled)
print(speed, distance_travelled)
sleep(dt)
elif direction == -1:
if position > lower_rampdown_target:
# above offset and rampdown distance, ramp up to setpoint (negative), then run at setpoint
if stroke_part != 3:
stroke_part = 3
print("{} - {}".format(stroke_part, position))
if speed > (-1.0 * run_freq):
speed += -1.0 * (motor_full_speed_hz / accel_time) * dt
if speed < (-1.0 * run_freq):
speed = -1.0 * run_freq
elif position > lower_turnaround_target and position <= lower_rampdown_target:
# between turnaround distance and rampdown distance, ramp ro rampdown speed, then run at rampdown speed
if stroke_part != 4:
stroke_part = 4
print("{} - {}".format(stroke_part, position))
if speed < (-1.0 * rampdown_speed):
speed += 1.0 * (motor_full_speed_hz / decel_time) * dt
elif position <= lower_turnaround_target:
# below turnaround distance, ramp to 0 and change direction
if stroke_part != 5:
stroke_part = 5
print("{} - {}".format(stroke_part, position))
if speed < 0:
speed += 1.0 * (motor_full_speed_hz / decel_time) * dt
if speed >= 0:
speed = 0
direction = 1
strokes += 1
end = datetime.now()
delta_x = (speed + last_speed) / 2.0 * (motor_full_speed_rpm / motor_full_speed_hz) * (dt / 60.0) * thread_pitch
# delta_x = speed * (motor_full_speed_rpm / motor_full_speed_hz) * (dt / 60.0) * thread_pitch
position += delta_x
time += dt
speed_array.append(speed * (motor_full_speed_rpm / motor_full_speed_hz))
position_array.append(position)
time_array.append(time)
print("Time: {} sec., Position: {} in., Speed: {}".format(time, position, speed * (motor_full_speed_rpm / motor_full_speed_hz)))
# sleep(dt)
stroke_time = end - start
print("Took {} seconds".format(stroke_time))
plt.plot(speed_array)
plt.plot(distance_array)
SPM = 60.0 / (time / strokes)
max_position = max(position_array)
min_position = min(position_array)
print("Max: {}, Min: {}".format(max_position, min_position))
print("SPM: {}".format(SPM))
fig, ax1 = plt.subplots()
ax1.plot(time_array, speed_array, "b-")
ax1.set_ylabel("RPM", color="b")
ax2 = ax1.twinx()
ax2.plot(time_array, position_array, "r-")
ax2.set_ylabel("in.", color="r")
fig.tight_layout()
plt.show()
# calculate SPM using ramp time and RPM setpoint
sim()
sim(run_speed, rampdown_speed, 1)