Injector position sensing
Injection systems can include a reservoir, a plunger mounted within the reservoir, and a plunger shaft including engaging the plunger within the reservoir. A motor can be coupled to the plunger shaft and can be configured to cause the plunger and plunger shaft to move within the reservoir. Systems can include a first encoder and a second encoder and a controller array in communication with the first and second encoders. The controller array can receive outputs from the first and second encoders representative of the position of the motor. Outputs from one encoder can be used to confirm the accuracy of the output of the other encoder. The controller can compare the outputs from the encoders, and, if the difference in the outputs is greater than a predetermined amount, disable operation of the motor.
1. An injection system comprising:
a reservoir including an inner surface;
a plunger mounted within the reservoir and including an outer surface configured to engage with the inner surface of the reservoir;
a plunger shaft including a terminal portion configured to engage the plunger within the reservoir;
a motor coupled to the plunger shaft and configured to cause the plunger shaft and plunger to move linearly within the reservoir when the motor is actuated;
a multi-turn encoder in communication with the motor and configured to output a multi-turn encoder value representative of a rotational position of the motor;
a single-turn encoder in communication with the motor and configured to output a single-turn encoder value representative of a rotational position of the motor; and
a controller array configured to:
receive the multi-turn encoder value from the multi-turn encoder;
receive the single-turn encoder value from the single-turn encoder; and
determine a position of the plunger within the reservoir based on at least one of the multi-turn encoder value and the single-turn encoder value.
2. The injection system of claim 1 , wherein the controller array is further configured to:
compare the rotational position represented by the multi-turn encoder value and the rotational position represented by the single-turn encoder value; and
if the difference between the compared rotational positions is greater than a predetermined amount, disable the motor.
3. The injection system of claim 1 , wherein the single-turn encoder value from the single-turn encoder comprises two signals in quadrature.
4. The injection system of claim 3 , wherein the controller array comprises a quadrature counter and is configured to control operation of the motor based on a quadrature counter value.
5. The injection system of claim 4 , wherein the controller array is further configured to:
compare the quadrature counter value to the multi-turn encoder value and/or the single-turn encoder value; and
if the difference between the quadrature counter value and the multi-turn encoder value and/or the difference between the quadrature counter value and the single-turn encoder value is greater than a predetermined value, disable operation of the motor.
6. The injection system of claim 4 , wherein, upon startup of the system, the controller array is configured to compare the multi-turn encoder value and the single-turn encoder value, and if the difference between the multi-turn encoder value and the single-turn encoder value is below a predetermined value, enable operation of the motor.
7. The injection system of claim 1 , wherein the controller array comprises a first controller and a second controller.
8. The injection system of claim 7 , wherein:
the first controller is configured to:
receive a first multi-turn encoder value from the multi-turn encoder;
receive a first single-turn encoder value from the single-turn encoder; and
compare the first multi-turn encoder value to the first single-turn encoder value to determine a first comparison value;
the second controller is configured to:
receive a second multi-turn encoder value from the multi-turn encoder;
receive a second single-turn encoder value from the single-turn encoder; and
compare the second multi-turn encoder value to the second single-turn encoder value to determine a second comparison value; and
wherein the first controller or the second controller is further configured to disable the motor if:
(i) the first comparison value is greater than a predetermined threshold;
(ii) the second comparison value is greater than a predetermined threshold;
and/or (iii) the difference between the first comparison value and the second comparison value is greater than a predetermined threshold.
9. The injection system of claim 1 , further comprising a reservoir position sensor in communication with the controller array, and wherein the controller array is configured to:
receive reservoir position data from the reservoir position sensor;
compare the received reservoir position data to the determined position of the plunger based on at least one of the multi-turn encoder value and the single-turn encoder value; and
if the difference between the received reservoir position data and the determined position of the plunger is greater than a predetermined amount, disable operation of the motor.
10. The injection system of claim 1 , wherein the multi-turn encoder and the single-turn encoder are mounted to the motor.
11. The injection system of claim 1 , wherein, upon startup of the system, the controller array is configured to detect a position of the plunger within the reservoir.
12. The injection system of claim 11 , wherein the controller array is configured to
(i) save determined position information representative of the position of the plunger within the reservoir in memory upon disabling and/or shutting down the system such that the detecting the position of the plunger within the reservoir upon startup comprises recalling the saved position information; and/or
(ii) receive an initial multi-turn encoder value from the multi-turn encoder and/or an initial single-turn encoder value from the single-turn encoder upon enabling or starting up the system; such that the detecting the position of the plunger within the reservoir upon startup comprises determining an initial position of the plunger based on the received initial multi-turn encoder value and/or the initial single-turn encoder value.
13. The injection system of claim 1 , wherein the controller array is further configured to cause the motor to move the plunger shaft such that the plunger moves to a predetermined location within the reservoir based on feedback from the determined position of the plunger within the reservoir.
14. The injection system of claim 13 , further comprising a host computer in communication with the controller array, and wherein the controller array is configured to cause the motor to move the plunger shaft such that the plunger moves to the predetermined location within the reservoir in response to a command signal received from the host computer.
15. A method of operating an injection system comprising:
receiving a multi-turn encoder signal representative of a rotational position of a motor, the motor being configured to impart linear motion of a plunger shaft and a corresponding plunger within a reservoir in the injection system;
receiving a single-turn encoder signal representative of an absolute rotational position of the motor;
determining a position of the plunger within the reservoir of the injection system based on one of the received multi-turn encoder signal and the received single-turn encoder signal; and
confirming the determined position of the plunger within the reservoir based on the other of the received multi-turn encoder signal and the received single-turn encoder signal.
16. The method of claim 15 , wherein confirming the determined position of the plunger within the reservoir based on the other of the received multi-turn encoder signal and the single-turn encoder signal comprises comparing the received single-turn encoder signal to the received multi-turn encoder signal.
17. The method of claim 16 , further comprising, if the difference between the single-turn encoder signal and the multi-turn encoder signal is greater than a predetermined amount, disabling operation of the motor.
18. The method of claim 15 , wherein the single-turn encoder signal comprises a first signal and a second signal in quadrature, and wherein the method further comprises providing an electrical signal to the motor to control operation of the motor, the electrical signal having at least one parameter that is based on the received first and second signals.
19. An injection system comprising:
a plunger within a reservoir;
a plunger shaft configured to operatively engage the plunger;
a motor configured to move the plunger shaft longitudinally with respect to the reservoir such that, when the motor is actuated and when the plunger shaft engages the plunger, the plunger is moved longitudinally within the reservoir;
a first encoder coupled to the motor and configured to provide a first output representative of a position of the motor;
a second encoder coupled to the motor and configured to provide a second output representative of the position of the motor;
a controller array in communication with the motor, the first encoder, and the second encoder, the controller array being configured to:
receive the first output from the first encoder;
receive the second output from the second encoder;
compare the first output to the second output; and
if the difference between the first output and the second output is greater than a predetermined amount, disable operation of the motor.
20. The injection system of claim 19 , wherein the controller array is further configured to:
determine an absolute position of the plunger within the reservoir based on the first output, the second output, or a combination of the first output and the second output; and
repeatedly receive updated first and second outputs from the first and second encoders, respectively, and update the determined absolute position of the plunger within the reservoir based on the updated first output, the updated second output, or a combination of the updated first output and the updated second output.