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Help needed on motor load performance

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I am using Sensored BLDC motors for some robotic movements. I am using ball screw mechanism for lifting a pedal up and down and I am driving my motors using motor drivers. On the pedal, there will be always a very high load, placed on it.

Now, my motor can lift up the pedal with my desired speed accurately but while going downward, the pedal just goes down freely overcoming the output speed of the motor. In other words, when the motors are on downward rotation, they can’t hold the weight of the load and fail to conform to the desired downward velocity; instead they just let the pedal goes down freely until it reaches the lower threshold.

For your information, this problem happens to my system in both directions. That's to say, while the pedal is on its upward move, if I try to pull the pedal up with my hand then also the motor fails to keep up the input speed. I am meaning that, in both directions, if I give any force toward the motor's rotating direction, it completely fails to comply with the desired input speed. Otherwise, it works fine.

Please let me know if you have any further query

Thanks in advance

Figures from my motor driver manual

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