This repository includes scripts that allow the user to conduct thermal ultrasound experiments with closed loop control using a PID with anti-windup control system.
This system requires MATLAB with the Instrument Control Toolbox Support Package that is relevant for the hardware that you will be using. For example, the code as currently written uses the "Instrument Control Toolbox Support Package for Keysight IO Libraries and VISA Interface"
This system is designed to function with the following instruments:
BK Precision 4050 Function / Arbitrary Waveform Generator
Velmex VMX-3 Stepping Motor Controller
Neoptix Fiber Optic Rectal Thermometer
If a different waveform generator, motor controller, or fiber optic thermometer is used, the subroutines used in this code must be modified to the programming syntax of these new pieces of hardware as described in their programming manual.
The ultrasound signal generated needs to be amplified using an RF amplifier that can boost the signal voltage to be sufficient to drive an ultrasound transducer at the target pressure values.
These scripts must all be in the same directory in order to function. The results of any scans or acquisitions made by these scripts will be in this directory, so place this directory in a drive with sufficient available space.
Before running the scripts, the VISA address of the signal generator and oscilloscope must be appended to the list of VISA addresses within the following file:
sub_SG_Initialize.m (for the signal generator)
Consult the programming manual of the signal generator to determine how to find the specific instrument's VISA address. The program should be able to find the connected Velmex motor stage and Neoptix thermometer system automatically.
The signal generator, oscilloscope, and thermometer must be connected to the Matlab computer via USB cables. Using unpowered USB ports may lead to unstable connections that can cause the programs to crash. Use powered USB hubs if possible.
The cables for this system must be connected as such
SG Ch 1 <--> Amplifier In
Amplifier out <--> US Tx
Prior to any experiment, update the transducer, amplifier, safety, and any other hardware parameters values within the following file. It is important to update the amplifier gain values in this script, as it is used to determine the signal generator output for the PID controller:
sub_AllSettings.m
Position both the transducer and hydrophone in a water bath, with the transducer mounted to the motor stage system. Define an ultrasound test signal that can be run safely continuously during alignment. This signal will be used to generate a defined area of heating at the focal point of the transducer such that the transducer can be aligned with the implanted therometer. You can define this waveform manually or you can use the following script:
SetTestingParameter.m
Edit the testing parameters within that file first, then execute the file to apply those changes to the signal generator. That script will throw an error if any value violates the prior defined safety limits.
Manually position the transducer such that a localized area of heating is observed on the Neoptix readout. If using a GUI would be useful in this manual course adjustment of the transducer, then run:
stage_GUI.m
After aligning the transducer to the hydrophone as described above, use the following script to activate the thermal control system:
ThermalGUI.m
Before running the script, open the script file to modify the following key parameters seen under the ThermalGUI_OpeningFcn function as is fit for this application:
% User-defined values for thermal control experiment
handles.PID.TA = 46; % Reference temperature (Celsius) for Scheme A
handles.PID.TB = 37; % Reference temperature (Celsius) for Scheme B
% Default PID with anti-windup constants
handles.PID.Kp = 0.1; % Proportional control
handles.PID.Ki = 0.1; % Integral control
handles.PID.Kd = 0; % Derivative control
handles.PID.Kt = 0.25; % Anti-windup control
% Output of PID controller is peak-to-peak voltage of signal from
% amplifier. This value ranges from 0 to the MaxVppTransducer defined
% below:
handles.MaxVppTransducer = 50;
% This script will use the amplifier gain value defined in
% sub_AllSettings, to determine the appropriate signal generator amplitude.
% So prior to running script, ensure that amplifier gain and any
% transducer or amplifer safety settings are updated in sub_AllSettings
handles.data.schemeprd = 5; % Time (minutes) between scheme switch
When tuning the parameters, take note of the control system architecture for this PID with anti-windup controller:
The values of Kp, Ki, Kd, Kt will likely vary depending on the thermal properties of the target of thermal insonation, and may need to be adjusted empirically while the thermal exposure is running. However, prior to beginning parameter tuning, a rough estimate can be acquired through the use of the Ziegler-Nichols method [1]
[1] Song Y-D. Control of Nonlinear Systems Via PI, PD and PID : Stability and Performance. Vol First edition. Boca Raton, FL: CRC Press; 2018. http://search.ebscohost.com.libproxy1.usc.edu/login.aspx?direct=true&db=nlebk&AN=1913747. Accessed May 21, 2020.
Currently contributing is not suppported, please see future versions at https://github.com/drmittelstein/thermal_control to determine whether this changes.
Please see available versions at https://github.com/drmittelstein/thermal_control
- David Reza Mittelstein - "Modifying ultrasound waveform parameters to control, influence, or disrupt cells" Caltech Doctorate Thesis in Medical Engineering
- Acknowledgements to my colleagues in Gharib, Shapiro, and Colonius lab at Caltech who helped answer questions involved in the development of these scripts.