ClearPath Integrated Servo Motor: Follow Digital Torque Command

[@hassanzaytoon7281]

In my application (winding very thick solid wires), I need to start and stop the motor using some buttons and a microcontroller. I know that during normal operation, the motor follows a digital unipolar PWM torque command in the direction of Input A as long as the Enable signal is high. If the load is suddenly disconnected, the motor will overspeed and shut down based on the maximum speed and overspeed timeout settings. Now, I need to stop the motor while it is running and the load is connected. What happens if I disable the Enable signal? 1) Will the motor overspeed due to the heavy opposite load torque? 2) Or will dynamic braking be triggered based on the maximum speed and overspeed timeout settings, even if the Enable signal is low? If the first scenario occurs, I am thinking that I can keep the Enable signal high while setting the PWM torque command to the minimum value. This way, I would force the motor to overspeed in the opposite direction while the Enable signal is high. Consequently, the motor would stop and shut down, holding the load stationary. Is my expectation correct? If not, what is the best way to stop the motor under a connected load condition?

[@TeknicInc]

Hi Hassan, Before I answer your specific questions, I wanted to provide some background information on ClearPath's Dynamic Braking feature. ClearPath's Dynamic Brake will (when triggered) cause the motor to resist all external motion as long as the motor continues to move. The Dynamic Brake, when active, acts like a viscous damper and applies more resistance the faster the motor spins. ClearPath motors ship configured to automatically engage the Dynamic Brake when disabled (although you can change this functionality through the ClearPath MSP setup software). In your application, whether the motor will come to a complete stop depends on the external forces applied to your motor. If the motor does come to a complete stop, the Dynamic Brake will not "hold" the load in place, but if you don't exert any external forces on the motor, then the motor won't move either. Deciding how best to configure your motor for your application can be nuanced, so I recommend contacting a Teknic engineer to discuss your application-specific requirements. You can reach out to us here: teknic.com/contact/. Regards, Brendan F. - Teknic Servo Systems Engineer

[@akshaykhot-sq3zs]

Is it possible that I set some resistive torque to maintain tension and if unloaded it will wound belt with same rate as load is unloading?

[@TeknicInc]

Hi Akshay Khot, In the operational mode "Follow Digital Torque", you cannot control velocity or acceleration. If the motor is applying a constant torque to maintain tension on a material, and that material breaks, the motor will immediately start to accelerate at a rate determined by how much torque you're commanding (and what the load is). The motor will shut down when the “Max Speed” setting is exceeded for the amount of time defined by the "Over-speed timeout" parameter. The user can modify the “Max Speed” and “Over-speed Timeout” parameters in MSP to suit their application needs. If you are looking for a mode where you can vary the torque limit and velocity, you could take a look at the mode "Follow Digital Velocity: Bipolar PWM Command with Variable Torque". We don't have a demo video for this mode, but there is more information regarding this mode in the ClearPath User Manual: teknic.com/files/downloads/clearpath_user_manual.pdf Regards, Jim W. Teknic Application Engineer

[@akshaykhot-sq3zs]

If motor is maintaining tension in belt for long period in static. Condition will motor heat up?

[@TeknicInc]

Hi Akshay Khot, Yes, the motors can become warm to the touch if they are enabled and applying a constant (static) torque for a certain period of time. The amount of heat that the motor produces depends on a few factors: 1) how much torque is being commanded (and for how long), 2) the ambient air temperature, and 3) any cooling provisions such as a ventilated enclosure or fan. Additionally, there are safety parameters built into the motors to prevent them from overheating or becoming damaged. In most cases, if the static torque is kept below the motor’s continuous torque rating, the motor may heat up but it won't shut down. If the motor applies torque much above the continuous torque for long enough, the motor will, at some point, shut itself down to protect its windings from burning up. Regards, Jim W. Teknic Application Engineer

[@derekrussell9925]

Does Clearpath offer some kind of solution for keeping line tension the same if I were to use a clearpath motor in a winding/rewinding application? For example, if I were to set the servo to one specified torque setting and then wind up a large diameter roll, I would not have the same amount of tension on the material being wound up as the roll diameter changes.

[@TeknicInc]

Hi Derek Russell, Yes, ClearPath motors have been used successfully by Teknic’s customers in web tensioning applications with excellent results. There are a number of ways the ClearPath motors can be used to maintain proper web tension. That said, the optimal method for each application type depends on a number of variables including mechanical design, substrate type, desired tension, and tension range as well as the type and capabilities of the controller. Since there are so many variables to consider (with both machine designs and the potential solutions), it would be suboptimal and potentially misleading to guess at a proper solution. If you want to discuss your application in greater detail or if you have additional questions, please feel free to give us a call at 585-784-7454 or send us a contact request here: www.teknic.com/contact/ Mark D. - Teknic Servo Systems Engineer

[@thomasm964]

I have a Tensile Test Machine that is pulling apart at an object in constant torque and I want the motor to automatically stop when the specimen that it is pulling on breaks (so when there is no more load on the motor or machine). Is there some kind of mode for detecting this load change and stop it from moving?

[@TeknicInc]

Hi Thomas - Yes, the ClearPath-MC operational mode featured in this video ("Follow Digital Torque") has Max Speed and Over-speed Timeout parameters designed to shut the motor down if that speed is exceeded for the time defined by the timeout. The servo would automatically shut itself down (i.e. stop outputting torque) very soon after the specimen breaks as long as these parameters are set appropriately. By default, the servo's dynamic braking feature will quickly slow or stop the axis upon shutdown of the motor. These safety features are discussed and demonstrated starting at 2:07. Just be aware if the tensile tester uses back-drivable mechanics with a vertical load, then additional components may be required to prevent the mechanics from falling when the motor is shutdown, like an electromechanical axis brake. If there are any other motion requirements in addition to the constant torque commands (e.g. positioning or jogging control for loading/unloading specimens, constant velocity strain testing, etc.) then a different operational mode might be required. If you have additional questions you can always call us (585-784-7454) or submit a contact request through our website (teknic.com/contact/). Best regards, Matt C. - Teknic Servo Systems Engineer