Questions - accurate positioning of modified start/stop positions for linear actuator

Community General Discussions
1

Hi, I have some questions about a project and was hoping to get some help.

I’m going to be using a servos and a linear actuator to move an object. I think the servo portion I can handle with the dynamixel servos and controllers available here.

For the linear actuator, I like the idea of using a tracked actuator as I want to mount a servo and object on the actuator for movement in Y axis and rotation of the object on plane. I looked at the Frigelli site, but the tracked actuators don’t seem to have potentiometers to control the movement along the track to fine precision. I presume I can move a “fixed” distance based on sending a fix time current pulse, but I’m concerned that may add too much variation. I’ll be performing repetitive actions and I want to move between consistent start/stop Y coordinate points a few hundred times, then modify the start/stop coordinates and move the new path a few hundred times, etc.

The other option seems to be an actuator with potentiometer like robotshop.com/en/12-stroke-150-lbs-force-linear-actuator-w-potentiometer.html along with their LAC, and purchase a linear slide to mount it to separately, rather than using a tracked actuator - firgelliauto.com/downloads/SpecSheetMiniTrackActuator.pdf

Any suggestions here that might help? I’m not sure limit switches will work as I want to change the start/stop end points for each set of repetitions. Setup will connect to PC to coordinate rotation of object with movement along actuator. Will likely use Python scripts.

Thanks in advance for suggestions.

2

You might want to take a look at the Pololu Jrk USB Motor Controller.
It take the potentiometer input and control the motor output, so you can build a controller out ot that.

For example, this board is found in that servo motor.

3

Hi ss25,

What kind of weight will the linear actuator need to handle?
There are L12 linear actuators that take many different signals and one can take PWM so it will always position (internally) at the same time.

Take a look:

But they are conservative when it comes to movement and torque.

For bigger applications you can also consider ServoCity linear actuators:

4

Eric,

The actuator won’t need to handle too much weight. I think servo, mounting plate and object should be under 2 lb total. I need 8"-12" stroke length, so the smaller Firgellis won’t work.

At this point I’m leaning to robotshop.com/en/12-stroke-150-lbs-force-linear-actuator-w-potentiometer.html and fab a track to attach it to that will move a mounting block for servo + object.