34
Intern Team Project #2 A/D Modelling Obi Michael, Nicholas Gill, and Frank Oh
Intern Team Project #2A/D Modelling
Obi Michael, Nicholas Gill, and Frank Oh
-- Cummins Confidential --2
Outline
I. A/D Modelling Project Introduction/ Background
II. A/D Modelling Approach
III. AAD and RAD Simulink Diagrams
IV. Steady State and Transient Response Results
V. Test Cases and Simulation Results
VI. Tuning
VII. Challenges/References/ Resources
-- Cummins Confidential --3
Outline
I. A/D Modelling Project Introduction/ Background
II. A/D Modelling Approach
III. AAD and RAD Simulink Diagrams
IV. Steady State and Transient Response Results
V. Test Cases and Simulation Results
VI. Tuning
VII. Schedule/Challenges/References/ Resources
-- Cummins Confidential --4
A/D Modelling Project Introduction/ Background
Definition– A/D (Analog-to-Digital) is an electronic conversion process in which an analog
signal is converted into a digital signal.
Goal– Design A/D circuits using Simulink similar to A/D pins on the ECM and also
design test cases which can be run on the models to understand the electrical characteristics of those pins.
Value– A/D Modelling simulates the internal circuitry of the ECM along with the sensor/
actuator to understand the electronic characteristics of the pin and/or the actuators/ sensors.
– A/D models could be used for tuning the out of range values for the sensors in software.
-- Cummins Confidential --5
Outline
I. A/D Modelling Project Introduction/ Background
II. A/D Modelling Approach
III. AAD and RAD Simulink Diagrams
IV. Steady State and Transient Response Results
V. Test Cases and Simulation Results
VI. Tuning
VII. Challenges/References/ Resources
-- Cummins Confidential --6
A/D Modelling Approach
Read specs on sensors to be modeled.– AAP (Ambient Air Pressure) Sensor– CT (Coolant Temperature) Sensor
Two sensor connection circuits were modeled in Simulink– RAD (Ratiometric Analog-Digital) Circuit
• Pressure sensor connection circuit.• Input is a variable voltage
– AAD (Absolute Analog-Digital) Circuit• Temperature sensor connection circuit.• Input is a variable resistance.
-- Cummins Confidential --7
Outline
I. A/D Modelling Project Introduction/ Background
II. A/D Modelling Approach
III. AAD and RAD Circuit & Simulink Diagrams
IV. Steady State and Transient Response Results
V. Test Cases and Simulation Results
VI. Tuning
VII. Challenges/References/ Resources
-- Cummins Confidential --8
AAD Circuit (Confidential)
• CT Sensor Input• Variable Resistance
• Output Voltage• Input to ECM microcontroller
-- Cummins Confidential --9
AAD Simulink Circuit • Function block: Matlab Code• Temperature Relationship• Loops through all temperatures
-- Cummins Confidential --10
Function Block Code
-- Cummins Confidential --11
AAD Temperature-Resistance relationship
TemperatureTolerance
Nominal Resistance
-- Cummins Confidential --12
RAD Circuit (Confidential)
• AAP Sensor Input• Variable Voltage
• Output Voltage• Input to ECM Microcontroller
-- Cummins Confidential --13
RAD Circuit Design Simulink• Function block: Matlab Code• Pressure Relationship• Loops through all Pressure
-- Cummins Confidential --14
Pressure Relationship Function Block Code
• RAD Pressure – Voltage Relationship
• Tolerance
-- Cummins Confidential --15
Outline
I. A/D Modelling Project Introduction/ Background
II. A/D Modelling Approach
III. AAD and RAD Simulink Diagrams
IV. Steady State and Transient Response Results
V. Test Cases and Simulation Results
VI. Tuning
VII. Challenges/References/ Resources
-- Cummins Confidential --16
AAD (CT Sensor) Circuit Simulation Approach
Logged Input Resistance and Output Voltage using Simulink.– Output Voltage was converted to counts
– Counts was converted to temperature using calterm table (C_AIP_CT_Linear_Y).
Plotted Graph of Temperature vs. Resistance.– The graph was compared to original graph from CT sensor specification sheet
information.
-- Cummins Confidential --17
AAD Steady State Specs sheet Vs. Simulation (Temp. - °C, Resistance - Ω)
-- Cummins Confidential --18
RAD (AAP Sensor) Circuit Simulation Approach
Input Voltage and Output Voltage were logged using Simulink.– Output Voltage was converted to counts – Counts was converted to Pressure (kPa) using calterm table (C_AAP_SensorY).
Graph of Pressure Vs. Voltage was plotted.– The graph was compared to original graph from spec sheet information.
-- Cummins Confidential --19
RAD Steady State Calculation Vs. Simulation
-- Cummins Confidential --20
Transient Response Analysis (RAD)
• Unit Step Input Transient response.• It takes 2.2ms for output voltage to reach desired value.
-- Cummins Confidential --21
Outline
I. A/D Modelling Project Introduction/ Background
II. A/D Modelling Approach
III. AAD and RAD Simulink Diagrams
IV. Steady State and Transient Response Results
V. Test Cases and Simulation Results
VI. Tuning
VII. Challenges/References/ Resources
-- Cummins Confidential --22
Test Case 1: AAD Circuit (CT Sensor) – Voltage Supply Change Effect New ECMs would have a 5 V voltage supply.
– Old ECMs had a 5.175 V supply.
Simulation was done to see if there would be a major change in the output for a voltage supply change.
Voltage Supply
-- Cummins Confidential --23
AAD Simulation
-- Cummins Confidential --24
AAD Simulation Comments
5.175 V graph has different X,Y points than 5 V graph– For Example,
• corresponds to -25°C on 5 V graph• Ω corresponds to -48°C on 5.175 V graph
Voltage Supply change would result in change in the ECM software/calibration for the CT sensor.
-- Cummins Confidential --25
Test Case 2: RAD Circuit (AAP Sensor) – Pull-down Resistor Effect Some ECM’s do not have the 47.5 KΩ resistor in the RAD
circuit for the pressure sensors. Simulation was done to see if this resistor actually affects
the output voltage of the RAD circuit.
Pull-down Resistor
-- Cummins Confidential --26
RAD Circuit Simulation
-- Cummins Confidential --27
RAD Circuit Simulation Comments
Although Simulation shows that the pull-down resistors do not affect the response of the circuit, it is still important.
Pull-down resistor prevents microcontroller from reading an unknown state when the AAP sensor input pin is floating.– Improves accuracy and reliability of readings.
Floating Sensor InputMicrocontroller Pin
-- Cummins Confidential --28
Outline
I. A/D Modelling Project Introduction/ Background
II. A/D Modelling Approach
III. AAD and RAD Simulink Diagrams
IV. Steady State and Transient Response Results
V. Test Cases and Simulation Results
VI. Tuning
VII. Challenges/References/ Resources
-- Cummins Confidential --29
Tuning
Tuning is adjusting certain parameters in an attempt to make certain features or hardware components perform optimally.– Proper tuning can prevent false failures from occurring and to
help us better catch failures when they do occur.
For this project we attempted to tune the OORL and OORH values for the AAP and CT sensors
-- Cummins Confidential --30
Tuning (AAD)
AAD (Coolant Temperature Sensor)– Highest and lowest limits for resistance was calculated with
tolerances from spec sheet.– Resistances were corresponded with simulated graphs to derive
the temperatures.– Actual Out of Range Tuning values from calterm.
Calculated Temperature LimitsLower Limit -47°C 420,000 Ω Upper Limit 150°C 163 ΩCalterm Out-Of-Range Temperature Sensor CalibrationLower Limit -48.92°C Upper Limit 150°C
-- Cummins Confidential --31
Tuning (RAD)
RAD (Ambient Air Pressure)– Highest and lowest limits for input voltage was calculated with
tolerances from spec sheet.– Input Voltage limits were corresponded with simulated graphs to
derive the temperatures– Actual Out of Range Tuning values from calterm
Calculated Pressure LimitsLower Limit 43.5 kPa 0.45 VUpper Limit 113.6 kPa 4.7 VCalterm Out-Of-Range Pressure Sensor CalibrationLower Limit 40.8 kPa Upper Limit 114.3 kPa
-- Cummins Confidential --32
Outline
I. A/D Modelling Project Introduction/ Background
II. A/D Modelling Approach
III. AAD and RAD Simulink Diagrams
IV. Steady State and Transient Response Results
V. Test Cases and Simulation Results
VI. Tuning
VII. Challenges/References/ Resources
-- Cummins Confidential --33
Challenges
Software version Differences– Frank (Matlab R2013b), Obi and Nick (Matlab R2010a)
Learn Simulink Balancing time for individual team projects and group
projects.
-- Cummins Confidential --34
Special Thanks to…
Shashi Singh – HMLD Off-Highway Controls Customer Engineer.
Managers and Project Stakeholders. 2014 Group Intern Project Presentation. Mathworks.com
