Provide constant load using linear exlar motor driven by indradrive


Thread Starter

Austin Cann


I am developing an application where a bosch drive and servo motor
screw in and out a connecting rod. This connecting rod has to be supplied with a constant compressive load of 1490 acting against its motion when it screws out and the constant tensile load of 1490 LBF when motor moves in opposite direction causing the connecting road to screw back in.

This load has to be supplied by another bosch indradrive driving a linear exlar motor.

The connecting rod during the period of its motion may be required to accelerate, decelerate and stop. In all conditions, the application requires the constant load supplied by the Linear exlar motor.
Does this constant load requirement requires only setting the parameters in indradrives? If so, what are these?

Many thanks in advance
Wouldn't it be about a million times cheaper to have a rolling diaphragm ("Bellofram") air cylinder provide the constant resistive force, with a decent sized air accumulator (and good-sized non-restrictive port and piping connecting the diaphragm to the accumulator)? Or two opposed, it sounds like you may need to reverse the force direction.

Or just roll your own with the diaphragm ON the front end of the accumulating volume to eliminate pressure fluctuations caused by screw movement.

Or hell, a couple big chunks of concrete.
We have got to use the indra drives I am afraid.

Costs have been paid, equipment delivered, assembled, ready for some software.
With most of the servos (and in fact even most VFD's) I've used, you can choose a torque (in your case probably a "force") mode that just applies the specified force at the motor, regardless of whether it's moving forward, stalled, or being pulled backward and acting as a brake.

Have no idea what parameters to set up in an Indramat drive to make it work that way though. Why not just ask Bosch or the distributor who supplied the parts, though? They should have the knowledge and they should be willing to help out.
It sounds like you are driving screw device with a motor, and then using the Exlar actuator as the load applying device, si that correct?

If so, and the motor controlling the screw is in position mode, the drive controlling the Exlar actuator could be operated in torque mode, with the torque setting to provide 1490 pounds (that would need to be determined, and somehow calibrated in your system if there is no load cell doing that measurement). Being in torque mode, the drive that is powering the Exlar actuator would not be concerned with position error and following error, so it should not trip. Since the indradrive/Exlar actuator axis will be in constant stall while being backdrive, it is important that axis be sized appropriately to offer more than the 1490 pounds required.

Do you know from where the Indramat and Exlar products were sourced? It is likely that the Indradrive supplier and Exlar rep can assist you with getting such a system operable.

John Walker
i'm not too familiar with indradrive, but all drives have a torque limit, positive, negative, sometimes bipolar. You should be able to set one or all of these to create a constant force, however the issue you may get into is you'll be creating accels and decels in speed to obtain this torque limit. you may need to explain it more to get a better answer i.e. if you truly need to limit it through the full range AND be able to have controlled accels and decels.

Michael Mason

The problem with the Exlar linear actuator is it has a pre-load and cannot even when switched off just freewheel like a servo motor. As an example we have just purchased an Exlar which needs 151kgs of force to move it in or out.

I think it would be best to use Indradrive with Sercos 3 Master Slave and control Exlar as slave to follow Master though CCD by profiling. Use Labview as via TCP/IP to control Master, and Data Acq. if required.
2-axis motion controller - one axis for screw control and second one with Exlar controlled load force will be suggested for right synchronization between controlled screw and applied load also.