Method and apparatus for controlling a temperature-controlled probe

• US 6,162,217 A
• Filed: 04/21/1999
• Issued: 12/19/2000
• Est. Priority Date: 04/21/1999
• Status: Active Grant

• Current Assignee: Oratec Interventions Incorporated
• Original Assignee: Oratec Interventions Incorporated
• Inventors: Kannenberg, Donald P., Lisiecki, Andrew I.
• Primary Examiner(s): Dvorak, Linda C. M.
• Assistant Examiner(s): GIBSON, ROY DEAN
• Application Number:
  US09/296,690
• Time in Patent Office: 608 Days
• Field of Search: 606/34, 606/36-40, 606/32-33
• US Class Current: 606/34
• CPC Class Codes: A61B 18/08 by means of electrically-heated probes
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 18/14 Probes or electrodes therefor
• CPC Class Codes: A61B 2017/00084 Temperature
• CPC Class Codes: A61B 2017/00482 with a code
• CPC Class Codes: A61B 2018/00178 Electrical connectors
• CPC Class Codes: A61B 2018/00642 with feedback, i.e. closed loop control
• CPC Class Codes: A61B 2018/00684 using lookup tables
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00791 Temperature
• CPC Class Codes: A61B 2018/00988 Means for storing information, e.g. calibration constants, or for preventing excessive use, e.g. usage, service life counter
• CPC Class Codes: A61B 2018/0237 with a thermoelectric element in the probe for cooling purposes
• CPC Class Codes: A61B 2018/0262 using a circulating cryogenic fluid

Abstract

A method and apparatus to control a power output of a probe connected to a controller in a thermal energy controller system to maintain a target temperature. The system includes a probe, a controller/generator and a means for connecting the probe to the controller. The probe has a thermal element and a temperature sensor. The temperature sensor provides a sensed temperature. The method and apparatus allow the controller to more effectively accommodate different types of probes by providing selectable probe settings for the probes. The controller modifies its operation in response to the selected probe setting. In this way, the power output of each type of probe can be more effectively controlled to better maintain the selected target temperature.

Claims

1. A method for controlling a power output of a probe connected to a system including controller circuitry to maintain a target temperature, the probe having a thermal element and a temperature sensor, the temperature sensor providing a sensed temperature, comprising the steps of:

providing, in a memory, at least one set of probe settings including at least one gain parameter and corresponding to predetermined operating characteristics for a particular probe;

receiving the target temperature;

receiving a first probe setting corresponding to a desired set of operating characteristics for a probe;

selecting a set from the at least one set of probe settings in response to the first probe setting;

generating an error signal by comparing the sensed temperature to the target temperature;

determining an output control signal by applying a control function to the error signal, the control function using the at least one gain parameter from the selected set; and

controlling an amount of power output to the thermal element in response to the output control signal to maintain the target temperature.

2. The method of claim 1 wherein the at least one gain parameter of the at least one set of probe settings includes a set specific proportional gain factor and a set specific integral gain factor, and wherein:

said step of determining an output control signal includes the steps of;

generating a proportional signal by multiplying the error signal by the selected set specific proportional gain factor;

generating an integral signal by integrating the error signal and multiplying the integrated error signal by the selected set specific integral gain factor; and

summing the proportional signal and the integral signal to generate the output control signal.

3. The method of claim 2 wherein the at least one gain parameter of the at least one set of probe settings includes a set specific derivative gain factor, and wherein:

said step of determining the output control signal includes the step of;

generating a derivative signal by applying a derivative function to the sensed temperature to generate an intermediate signal, and multiplying the intermediate signal by the selected set specific derivative gain factor, wherein said step of summing also sums the derivative signal to generate the output control signal.

4. The method of claim 1 wherein the at least one gain parameter of the at least one set of probe settings includes a set specific proportional gain factor, a set specific integral gain factor and a set specific derivative gain factor, and wherein:

said step of determining an output control signal includes the steps of;

generating a proportional signal by multiplying the error signal by the selected set specific proportional gain factor;

generating an integral signal by integrating the error signal and multiplying the integrated error signal by the selected set specific integral gain factor;

generating a derivative signal by comparing the sensed temperature to a previous sensed temperature and applying a derivative function to generate an intermediate signal and multiplying the intermediate signal by the selected set specific derivative gain factor; and

summing the proportional signal, the integral signal and the derivative signal to generate the output control signal.

5. The method of claim 1 further comprising the step of:

limiting the output control signal to a predetermined output value when the output control signal exceeds a predetermined threshold.

6. The method of claim 2 further comprising the step of:

when the predetermined output value exceeds a predetermined threshold value, disabling said step of generating the integral signal.

7. The method of claim 2 further comprising the steps of:

determining an antiwindup difference by subtracting a maximum predetermined output control value from the output control signal;

generating an antiwindup adjustment signal by multiplying the antiwindup difference by an antiwindup gain factor; and

generating a modified error signal by subtracting the antiwindup adjustment signal from the error signal,

wherein said step of generating an integral signal integrates the modified error signal by the integral gain factor.

8. The method of claim 1 further comprising the steps of:

receiving a ramp parameter corresponding to a particular profile at which to ramp up the output power; and

changing the target temperature in response to the ramp parameter.

9. The method of claim 8 further comprising the steps of:

receiving a switch setting corresponding to a particular profile at which to ramp up the output power; and

changing the target temperature in response to the switch setting.

10. The method of claim 9 wherein said step of selecting the set from the at least one set of probe settings selects a first set of probe settings in response to the switch setting, and further comprising the steps of:

determining an intermediate target temperature in response to the switch setting; and

selecting a second set of probe settings in response to the switch setting when the intermediate target temperature is reached.

11. The method of claim 1 wherein the at least one gain parameter of the at least one set of probe settings includes a set specific derivative gain factor, and further comprising the step of:

generating a derivative signal by multiplying the sensed temperature by a first predetermined signal, subtracting a temporary integral signal generated from a previous sensed temperature to generate an intermediate signal, and multiplying the intermediate signal by the selected set specific derivative gain factor.

12. The method of claim 1 wherein the at least one set of probe settings includes a set specific default target temperature and a set specific default maximum output power, and wherein said step of receiving the target temperature sets the target temperature to the selected set specific default target temperature, and wherein said step of controlling the amount of power output to the thermal element clamps the power output to the selected set specific default maximum output power.

13. A method for controlling a power output of a probe connected to a system including controller circuitry to maintain a target temperature, the probe having a thermal element and a temperature sensor, the temperature sensor providing a sensed temperature, comprising the steps of:

providing, in a memory, at least one set of probe settings including at least one gain parameter and corresponding to predetermined operating characteristics for a particular probe, the at least one gain parameter including a set specific proportional gain factor, a set specific integral gain factor and a set specific derivative gain factor;

receiving the target temperature;

receiving a first probe setting corresponding to a desired set of operating characteristics for a probe;

selecting a set from the at least one set of probe settings in response to the first probe setting;

receiving a sensed temperature;

generating an error signal by comparing the sensed temperature to the target temperature;

generating a proportional signal by multiplying the error signal by the selected set specific proportional gain factor;

generating an integral signal by integrating the error signal and multiplying the integrated error signal by the selected set specific integral gain factor;

generating a derivative signal by comparing the sensed temperature to a previous sensed temperature and applying a derivative function to generate an intermediate signal and multiplying the intermediate signal by the selected set specific derivative gain factor;

summing the proportional signal, the integral signal and the derivative signal to generate the output control signal;

controlling an amount of power output to the thermal element in response to the output control signal to maintain the target temperature;

determining an antiwindup difference by subtracting a maximum predetermined output control value from the output control signal;

generating an antiwindup adjustment signal by multiplying the antiwindup difference by an antiwindup gain factor; and

generating a modified error signal by subtracting the antiwindup adjustment signal from the error signal, wherein said step of generating the integral signal integrates the modified error signal by the integral gain factor.

14. A system for controlling the power output of a probe connected to the system to maintain a temperature, the probe having a thermal element, and a temperature sensor providing a sensed temperature, comprising:

a processor; and

a memory storing at least one set of probe settings, the at least one set including at least one gain parameter and corresponding to a predetermined operating characteristics for a particular probe,

the memory also storing instructions that cause the processor to;

receive a target temperature value;

receive a first probe setting corresponding to a desired set of operating characteristics for a probe;

select a set of the probe settings in response to the first probe setting;

generate an error value by comparing the sensed temperature value to the target temperature value; and

determine an output control value by applying a control function to the error value, the control function using the at least one gain parameter from the selected set whereby an amount of power is outputted to the thermal element in response to the output control value to maintain the temperature.

15. The system of claim 14 wherein the at least one gain parameter of the sets of probe settings includes a set specific proportional gain factor and a set specific integral gain factor, and wherein:

the instructions that determine the output control value includes instructions to;

generate a proportional value by multiplying the error value by the selected set specific proportional gain factor;

generate an integral signal by integrating the error value and multiplying the integrated error value by the selected set specific integral gain factor;

generate a derivative value by comparing the sensed temperature value to a previous sensed temperature value and applying a derivative function to generate an intermediate value and multiplying the intermediate value by the selected set specific derivative gain factor; and

sum the proportional value, the integral value and the derivative value to generate the output control value.

16. The system of claim 14 wherein the memory further includes instructions to limit the output control value to a predetermined output value when the output control value exceeds a predetermined threshold.

17. The system of claim 14 wherein the memory further includes instructions to:

receive a switch setting corresponding to a particular profile at which to ramp up the output power; and

change the target temperature in response to the switch setting.

18. A computer program product for controlling a power level of a probe connected to a medical device computer system, the computer program product for use in conjunction with the computer system, the computer program product comprising a computer readable storage medium and a computer program mechanism embedded therein, the computer program mechanism comprising:

at least one set of probe settings including at least one gain parameter and corresponding to a predetermined operating characteristics for a particular probe;

a first set of instructions that receive a target temperature value;

a second set of instructions that receive a first probe setting corresponding to a desired set of operating characteristics for a probe;

a third set of instructions that select a set from the at least one set of probe settings in response to the first probe setting;

a fourth set of instructions that receive a sensed temperature value;

a fifth set of instructions that generate an error value by comparing the sensed temperature value to the target temperature value;

a sixth set of instructions that determine an output control value by applying a control function to the error value, the control function using the at least one gain parameter from the selected set; and

a seventh set of instructions that cause an amount of power to be outputted to a thermal element in response to the output control value.

19. The computer program product of claim 18 wherein the at least one gain parameter of the at least one set of probe settings includes a set specific proportional gain factor and a set specific integral gain factor, and wherein:

the instructions that determine the output control value include instructions to;

generate a proportional value by multiplying the error value by the selected set specific proportional gain factor;

generate an integral signal by integrating the error value and multiplying the integrated error value by the selected set specific integral gain factor;

generate a derivative value by comparing the sensed temperature value to a previous sensed temperature value and applying a derivative function to generate an intermediate value and multiplying the intermediate value by a selected set specific derivative gain factor; and

sum the proportional value, the integral value and the derivative value to generate the output control value.

20. The computer program product of claim 18 wherein the computer program mechanism further includes instructions to limit the output control value to a predetermined output value when the output control value exceeds a predetermined threshold.

21. The computer program product of claim 18 wherein the computer program mechanism further includes instructions to:

receive a switch setting corresponding to a particular profile at which to ramp up the output power; and

change the target temperature value in response to the switch setting.