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https://gitee.com/mirrors_PX4/PX4-Autopilot.git
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a5cc4bcd08
Update the model for the standard configuration based on the model from Sensirion and add also an option to do the tube pressure loss correction from Sensirion for other configurations.
110 lines
3.3 KiB
Python
110 lines
3.3 KiB
Python
"""
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Copyright (c) 2017, Sensirion AG
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright notice, this
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list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation
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and/or other materials provided with the distribution.
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* Neither the name of Sensirion AG nor the names of its
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contributors may be used to endorse or promote products derived from
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this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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"""
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# formula for metal pitot tube with round tip as here: https://drotek.com/shop/2986-large_default/sdp3x-airspeed-sensor-kit-sdp31.jpg
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# and tubing as provided by px4/drotek (1.5 mm diameter)
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import numpy as np
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import matplotlib.pyplot as plt
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P_cal=96600. #Pa
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P_amb=96600. #dummy-value, use absolute pressure sensor!!
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## differential pressure, sensor values in Pascal
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dp_SDP33_raw=np.linspace(0,80,100)
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dp_SDP33=dp_SDP33_raw*P_cal/P_amb
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## total length tube in mm = length dynamic port+ length static port; compensation only valid for inner diameter of 1.5mm
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l_tube=450
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## densitiy air in kg/m3
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rho_air=1.29
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## flow through sensor
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flow_SDP33=(300.805 - 300.878/(0.00344205*dp_SDP33**0.68698 + 1))*1.29/rho_air
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## additional dp through pitot tube
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dp_Pitot=(0.0032*flow_SDP33**2 + 0.0123*flow_SDP33+1.)*1.29/rho_air
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## pressure drop through tube
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dp_Tube=(flow_SDP33*0.674)/450*l_tube*rho_air/1.29
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## speed at pitot-tube tip due to flow through sensor
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dv=0.125*flow_SDP33
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## sum of all pressure drops
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dp_tot=dp_SDP33+dp_Tube+dp_Pitot
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## computed airspeed without correction for inflow-speed at tip of pitot-tube
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airspeed_uncorrected=np.sqrt(2*dp_tot/rho_air)
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## corrected airspeed
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airspeed_corrected=airspeed_uncorrected+dv
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## just to compare to value without compensation
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airspeed_raw=np.sqrt(2*dp_SDP33/rho_air)
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plt.figure()
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plt.plot(dp_SDP33,airspeed_corrected)
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plt.xlabel('differential pressure raw value [Pa]')
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plt.ylabel('airspeed_corrected [m/s]')
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plt.show()
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##plt.figure()
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##plt.plot(dp_SDP33,airspeed_corrected/airspeed_raw)
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##plt.xlabel('differential pressure raw value [Pa]')
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##plt.ylabel('correction factor [-]')
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##plt.show()
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##
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##
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##
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##plt.figure()
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##plt.plot(airspeed_corrected,(airspeed_corrected-airspeed_raw)/airspeed_corrected)
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##plt.xlabel('airspeed [m/s]')
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##plt.ylabel('relative error [-]')
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##plt.show() |