SYSTEMS AND METHODS FOR CLOSED LOOP CONTROL TO ENSURE A CONSTANT CURRENT OUTPUT WITH A CHANGING LOAD RESISTANCE

• US 20170136242A1
• Filed: 11/17/2016
• Published: 05/18/2017
• Est. Priority Date: 11/18/2015
• Status: Active Grant

• Current Assignee: Case Western Reserve University
• Original Assignee: Case Western Reserve University
• Inventors: Durand, Dominique M.
• Granted Patent: US 10,441,790 B2
• Time in Patent Office: Days
• CPC Class Codes: A61N 1/0551 Spinal or peripheral nerve electrodes
• CPC Class Codes: A61N 1/36128 Control systems
• CPC Class Codes: A61N 1/36139 with automatic adjustment
• CPC Class Codes: A61N 1/3614 based on impedance measurement
• CPC Class Codes: A61N 1/3615 Intensity
• CPC Class Codes: A61N 2/006 for magnetic stimulation of nerve tissue
• CPC Class Codes: A61N 2/02 using magnetic fields produced by coils, including single turn loops or electromagnets A61N2/12 takes precedence
• CPC Class Codes: G05B 19/042 using digital processors G05B19/05 takes precedence
• CPC Class Codes: G05B 2219/45117 Medical, radio surgery manipulator
• CPC Class Codes: G16H 20/30 relating to physical therapies or activities, e.g. physiotherapy, acupressure or exercising
• CPC Class Codes: G16H 20/40 relating to mechanical, radiation or invasive therapies, e.g. surgery, laser therapy, dialysis or acupuncture

Abstract

A closed loop control system automatically ensures that an output of a device is constant. The system can receive an input to set a fixed value for a variable (e.g., a current, a heart rate, a tissue perfusion, an ion level, etc.), and this variable can be delivered to a feedback component. The system can also include the device to deliver the variable to a load. The feedback component can be coupled to the delivery device to sample the output of the delivery device at different times. Based on the sampling, the feedback component can vary a property of the delivery device related to the delivery of the variable to the load to ensure that the variable remains constant at the fixed value. In some instances, the system can be implemented as a stimulator that delivers the constant current of a current source and has a low output impedance of a voltage source.

Claims

1. A system comprising:

a delivery device to deliver a variable to a load; and

a feedback component, coupled to the delivery device, to sample an output of the delivery device at different times and to vary a property of the delivery device related to the delivery of the variable to the load to ensure that the variable remains constant at a fixed value,

wherein the feedback component receives an input to set the fixed value for the variable.

2. The system of claim 1, wherein

the variable comprises a current, wherein the current is analog;

the delivery device comprises;

a voltage source to provide a set point voltage; and

an adjustable gain amplifier to receive the set point voltage and provide the output current to the load; and

the feedback component is coupled to the adjustable gain amplifier to sample a power at different times and vary a gain of the adjustable gain amplifier based on the sampled power.

3. The system of claim 2, wherein the current is independent of an impedance of a load when the impedance of the load changes more slowly than a rate at which the feedback component varies the gain of the adjustable gain amplifier.

4. The system of claim 2, wherein the feedback component determines the power based on the sampled output current and the set point voltage and changes the gain based on the sampled output current to control the power delivered by the voltage source.

5. The system of claim 4, wherein the gain is changed based on a difference between the voltage determined within the feedback circuit and the set point voltage.

6. The system of claim 1, wherein the variable comprises at least one of heart rate, tissue perfusion, and ion level.

7. The system of claim 1, wherein:

the variable comprises a current, wherein the current is digital;

the delivery device comprises;

a microprocessor; and

a digital-to-analog converter to supply the current to the load; and

the feedback component comprises an analog-to-digital converter and the microprocessor to sample a power at different times and vary a property of the microprocessor based on the sampled power.

8. The system of claim 7, wherein the microprocessor adjusts a voltage input to the digital-to-analog converter based on the sampled power.

9. The system of claim 1, wherein the voltage source provides a low output impedance.

10. The system of claim 9, wherein the low output impedance reduces charge accumulation at a tissue-electrode interface.

11. A method comprising:

setting a constant output to provide to a load, wherein the output is provided with a low output impedance;

sampling a variable associated with the output at different times;

controlling a property related to the output based on the sampled variable so that the output to the load remains constant.

12. The method of claim 11, wherein the output comprises an analog current and the variable comprises a power associated with the analog current.

13. The method of claim 11, wherein the output comprises a digital current and the variable comprises a power associated with the digital current.

14. The method of claim 11, wherein the variable or the output comprises at least one of heart rate, tissue perfusion, and ion level.

15. The method of claim 11, wherein the output comprises a current for neural stimulation, the variable comprises a current power supplied to the load, and the property comprises a variable gain of an amplifier.

16. The method of claim 15, wherein the impedance of the load changes more slowly than a rate of the sampling.

17. The method of claim 11, wherein the variable comprises a detected magnetic field.

18. A stimulator with a constant output current and a low output impedance, the stimulator comprising:

a voltage source to provide a set point voltage;

an adjustable gain amplifier to receive the set point voltage and provide the output current independent of a impedance of a load; and

a feedback component, coupled to the adjustable gain amplifier, to sample a power at different times and vary a gain of the adjustable gain amplifier based on the sampled power.

19. The stimulator of claim 18, wherein the wherein the power delivered by the voltage source is controlled by adjusting a gain of the adjustable gain amplifier.

20. The stimulator of claim 18, wherein:

the impedance of the load changes more slowly than a rate at which the feedback component varies the gain of the adjustable gain amplifier.