Anemometer Calibration Unit - MATLAB Control Script

This MATLAB library serves as the controller for the Anemometer Calibration Unit developed under Dr. Spencer Zimmerman at Stony Brook University. The unit is designed to direct airflow via a nozzle at a specified pitch angle, yaw angle, and airflow rate, controllable via the included script. It is designed to work with genuine Phidgets™ stepper motors/controllers, Phidgets™ digital interface, and a DT9834-BNC Data Acquisition Unit.

A GUI exists for this repository, it can be found here

Purpose

Hot-wire and cold-wire Anemometers are utilized to obtain accurate readings of fluid flow speed and fluid flow angle. The Anemometer Calibration Unit is designed to test these anemometers by subjecting them to a specified fluid flow speed and fluid flow angle. By comparing the parameters produced by the calibration unit to the parameters recorded by the anemometer, it is possible to determine the accuracy of the anemometer (i.e do the anemometer readings match the given conditions?)

Prerequisites & Dependencies

1. Ensure that the correct version of MATLAB is installed on your system. As of May 2025, this code runs on MATLAB 2023b (64-bit Windows 11).

2. Install the MATLAB Support for MiniGW-w64 C/C++ Compiler from the Add-On Explorer page.

3. Install the MATLAB Data Acquisition Toolbox from the Add-On Explorer page.

4. Install the Data Acquisition Toolbox Support Package for National Instruments from the Add-On Explorer page.

5. Download the DT-Open Layers for .NET from Digilent, available here

6. Download the Data Translation DAQ Adaptor for MATLAB® from Digilent, available here:

   This will download a .mltb file, which you need to install using the MATLAB Add-On manager.

   After installation, this may be listed as Data Acquisition Toolbox Support Package for Data Translation Hardware by Digilent.

7. Navigate to C:\Users\{username}\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\Data Acquisition Toolbox Support Package for Data Translation Hardware\+daq\+dt\+internal'

   In AsyncOLChannel.m modify the following lines:

   Line 1:  classdef AsyncOLChannel < matlabshared.asyncio.internal.Channel
   

   Line 21:  [email protected](pluginInfo.devicePath, ...
   

   Line 23:  'Options', channelOptions,...
   

   Line 24:  'StreamLimits', streamLimits);
   

   Line 35:  matlabshared.asyncio.internal.DataEventInfo(remainderIn) );
   

   Line 51:  matlabshared.asyncio.internal.DataEventInfo(remainderOut) );
   

   In ChannelGroupOL.m modify the following line:

   Line 23:  AsynchronousIoChannel = matlabshared.asyncio.internal.Channel.empty();
   

Installation

To install and run this repository locally:

# Clone the repository
git clone https://github.com/moinakdas/anemometer-calibration-unit-controller.git
cd anemometer-calibration-unit

Then, launch MATLAB and run the main.m script

Pre-Operation

Ensure

• The DT9834-BNC DAQ is turned on and operational
• The pitot tube is positioned at the end of the nozzle
• The plenum chamber is plugged in, with both the fan and power switch at the ON position
• The controlling laptop is plugged into the plenum chamber via the included usb c cable

Operation

1. Initialization

The program begins by initializing all connected components using init_wrapper.m. Each device prints its connection status to the terminal:

Interface initialization SUCCESS!
Yaw motor initialization SUCCESS!
Pitch motor initialization SUCCESS!
Gate motor initialization SUCCESS!
Data Acquisition initialization SUCCESS!

[INIT SUCCESS] All components initialized successfully, proceeding to zero motors

2. Zeroing

Each stepper motor is zeroed using limit switches via zeroMotor_wrapper.m. This ensures all motors start from a known reference. The final positions (in steps) are stored and used for future movement:

Pitch motor zeroed at 30000
Yaw motor zeroed at 47111
Gate motor zeroed at 17114

[LOCALIZATION SUCCESS] All motors set to neutral position, ready to execute set

3. Configuration Execution

Motor commands are executed through a configuration matrix in runConfigurationSet.m, where each row defines a [Yaw, Pitch, Velocity] setting. You can modify this matrix directly in main.m, or save it to a csv and import it.

For each configuration:

• Motors move to the specified yaw and pitch angles.
• Gate position is adjusted using PID control to match the desired airflow velocity.
• Live feedback of the PID loop is printed per iteration.

[CONFIG #1] =======================
Yaw motor reached 0 deg
Pitch motor reached 0 deg
Target Velocity: 18
1 | Current = 17.84 | Error = 0.16
2 | Current = 17.80 | Error = 0.20
3 | Current = 17.76 | Error = 0.24
4 | Current = 17.94 | Error = 0.06
5 | Current = 17.95 | Error = 0.05
Velocity reached 17.95m/s
[CONFIG #1 COMPLETE] Holding for 15 seconds...

[CONFIG #2] =======================
Yaw motor reached 0 deg
Pitch motor reached 0 deg
Target Velocity: 10
1 | Current = 9.89 | Error = 0.11
2 | Current = 9.86 | Error = 0.14
3 | Current = 9.95 | Error = 0.05
4 | Current = 10.01 | Error = -0.01
Velocity reached 10.01m/s
[CONFIG #2 COMPLETE] Holding for 15 seconds...

============ [ALL CONFIGS COMPLETE] ============

4. Cleanup

After configuration execution, all motors and devices are safely disengaged via cleanup_wrapper.m. This prevents residual current holding torque or hardware damage:

Yaw motor disengagement SUCCESS!
Pitch motor disengagement SUCCESS!
Gate motor disengagement SUCCESS!
Interface disengagement SUCCESS!
DAQ disengagement SUCCESS!

⚠️ Warning: Interrupting the program (e.g., Ctrl-C) skips cleanup and leaves motors engaged. If this occurs, restart MATLAB and clear cached variables to reinitialize safely.

Usage

For operation, you may modify the main.m script by changing the configuration set matrix (providing different pitch, yaw, and flow speeds), or my utilizing the functions from the table below.

API Reference

Function	Description
cleanup(stepperHandle)	Disengages and releases a Phidget stepper motor.
cleanupInterface(interfaceHandle)	Closes and deletes a Phidget InterfaceKit handle.
getMotorPos(motorHandle)	Returns the current position (steps) of the motor.
initialize(motorID, motorSpeed)	Initializes a Phidget stepper motor with optional speed.
initializeDAQ()	Sets up the DT-9834-BNC DAQ session for analog input.
initializeInterface(interfaceID)	Initializes the Phidget InterfaceKit device.
moveRelative(motorHandle, delta)	Moves the motor relative to its current position by delta steps.
moveToDegYaw(deg, yawHandle, yawZeroStep)	Moves the yaw motor to a specified angle from zero.
moveToDegPitch(deg, pitchHandle, yawZeroStep)	Moves the pitch motor to a specified angle from zero.
moveto(stepperHandle, targetPosition)	Moves the motor to a specific absolute position. ⚠️ WARNING: This function does NOT account for physical limits or the motor's neutral position and could potentially damage the motor if used improperly. Instead use moveToDegPitch() and moveToDegYaw() to move the motors.
readPin(interfaceHandle, pinIndex)	Reads the digital input state (HIGH or LOW) of a pin.
setAllNeutral(yawHandle, pitchHandle, gateHandle, yawZeroStep, pitchZeroStep, gateZeroStep)	Returns all motors to their neutral (resting) position.
setVelocity(vel, gateHandle, daqHandle, gateZeroStep)	Uses PID to adjust the gate to achieve target airflow velocity.
stepper_control(inputArg1, inputArg2)	Placeholder control function for future expansion.
vel_toGateStep(desired_velocity)	Interpolates gate position needed for a desired velocity using calibration data.
voltToVel(voltage, offset)	Converts sensor voltage (with optional offset) to velocity.
zeroMotor(interfaceHandle, motorHandle, delta_1, delta_2, inputIndex)	Zeroes a motor using a limit switch and returns its zero position.
cleanup_wrapper(...)	Safely disengages all devices and prints connection status.
init_wrapper(...)	Initializes all Phidget motors and DAQ, with connection verification.
runConfigurationSet(configSet, holdTime, ...)	Executes a sequence of yaw, pitch, and velocity configurations.
zeroMotor_wrapper(...)	Zeroes all motors (yaw, pitch, gate) using limit switches.

🎥 Watch Demo Video

Relevant Resources for Future Development

• Forum Discussion for Data Acquisition Toolbox modifications (step 7 in Prerequisites & Dependencies)
• Data Translation DAQ Adaptor for MATLAB® Manual PDF
• Phidget21 MATLAB documentation

Future Work

• Implementation of airflow temperature control via PID control of Peltier Chips.
• Use a object-oriented approach for cleaner syntax
• Rewrite this in anything but MATLAB