Method and apparatus for controlling medical fluid pressure

1. A method of controlling pressure in a medical fluid pump comprising the steps of:

controlling a pump member according to a predetermined acceleration during a first portion of a pump stroke; and

adaptively changing the pump member velocity during a second portion of the pump stroke.

2. The method of claim 1 , which further includes the step of controlling a pump member deceleration during the first portion of the stroke.

3. The method of claim 1 , wherein the pump stroke is a patient fill stroke.

4. The method of claim 1 , wherein controlling the pump member acceleration includes moving the member at a rate of acceleration until a predefined velocity is reached.

5. The method of claim 1 , which includes the step of beginning the pump stroke at an initial, non-zero velocity.

6. The method of claim 1 , which includes the step of dividing the second portion into at least two sub-portions and adaptively changing the pump member velocity differently for the different sub-portions.

7. The method of claim 1 , which includes the step of adaptively changing the pump member velocity to correct for overshooting a pressure set point.

8. The method of claim 1 , which includes the step of adaptively changing the pump member velocity to achieve a pressure set point.

9. The method of claim 1 , which includes the step of adaptively changing the pump member velocity to achieve a desired end of stroke velocity.

10. The method of claim 1 , wherein adaptively changing the pump member velocity includes determining an error between a desired pressure and an actual pressure and performing an error compensating for the determined error.

11. The method of claim 10 , which includes the step of storing the error compensation for use in a subsequent pump stroke.

12. The method of claim 10 , which includes the step of adjusting the error compensation during a subsequent stroke.

13. The method of claim 10 , which includes the step of adjusting the error compensation during a subsequent stroke based on an error determination made during the subsequent stroke.

14. The method of claim 1 , wherein adaptively changing the pump member velocity includes changing the velocity based on at least one parameter selected from the group consisting of: a beginning pump member acceleration, a pressure proximity threshold, a rate of pressure change, a maximum pump member velocity, a pump member deceleration, a proportional coefficient, a derivative coefficient and an integral coefficient.

15. The method of claim 14 , which includes changing the velocity based on different ones of the parameters during different sub-portions of the second portion of the stroke.

16. A method of controlling pressure in a medical fluid pump comprising the steps of:

effecting a pump member acceleration and deceleration during a first portion of a pump stroke, the acceleration and deceleration determined before the first portion;

using a first set of factors determined during a second portion of the pump stroke to change the pump member velocity during the second portion; and

using a second set of factors determined during a third portion of the pump stroke to change the pump member velocity during the third portion.

17. The method of claim 16 , wherein the first set of parameters corrects an overshoot or undershoot in actual pressure with respect to a desired pressure caused during the first portion of the pump stroke.

18. The method of claim 16 , wherein the second set of parameters causes an actual pressure to oscillate about a desired pressure.

19. The method of claim 16 , wherein the pump stroke is a first pump stroke and which includes bypassing the acceleration/deceleration of the first portion of the first stroke, and using only the adaptive control of the second and third portions of the first stroke, during all of a second pump stroke.

20. The method of claim 16 , which includes adapting at least one of the first and second sets of parameters to compensate for a system variable selected from the group consisting of: patient physiology, fluid supply elevation, fluid supply level and fluid drain level.

21. An automated medical fluid system comprising:

a medical fluid pump; and

a controller that operates with the medical fluid pump to:

effect a pump member acceleration during a first portion of a pump stroke, the acceleration determined before the first portion;

use a first set of factors determined during a second portion of the pump stroke to change the pump member velocity during the second portion; and

use a second set of factors determined during a third portion of the pump stroke to change the pump member velocity during the third portion.