Hi everyone!
I am working on an interventional device tester for a project. It’s almost the same thing as in the video.
youtube.com/watch?v=_AqVZz3yv1s
I need help in choosing the correct stepper motor, motor controller and sensors.
Here are the following parameters:
Insertion speed has to be 15mm/s (+/- 10mm/s)
Insertion force: Minimum 5N
The sensor should be able to detect axial force in the range 0-10N. (+/- 0.015N)
If I calculate speed the way you mentioned, I am ignoring resistive forces.
If the test specimen is going through a curve, a resistive force will try to push it opposite the motion of the motor. How do I factor in the resistive forces in doing the calculation? I have to keep track of the resistive force to adjust the torque of the motor to keep the speed constant.
Thank you for your help.
I am still confused about the unipolar and bipolar motor. How do I know which one to choose? The motor has to move in both clockwise and anticlockwise direction.
Stepper motors are rated at number of degrees per step and number of steps per second. This can only translate to a linear speed when you attach a wheel to push the guide wire. Knowing the radius of the wheel, you can use the steps per second and degrees per step to get a maximum radians per second, then multiply that by the radius to get a maximum velocity in mm/s. If the controller does half steps, the speed would be reduced by factor of two. The choice of stepper controller can be made only after you choose a stepper motor (unipolar / bipolar, voltage and max current per coil).
With regard to a sensor which can detect forces on all sides, that’s a bit more difficult and we really don’t have anything out of the box which would work. One way to keep the tip small would be to place “sensor extensions” at the tip and wire them back to the actual sensors which are located outside of the tube itself. For example, have the tip push a solid rod backwards so it contacts a force sensor ()however this would only measure one axis).
That’s beyond the level of support we can provide here. Perhaps someone from the community may be able to give their insight.
