Editing Setting up parellel motors (two motors driving one gantry)
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| Motors tend to fight against each other during operation due to lead screw pitch error or feedback device inaccuracies || This is not a problem in systems where some mechanical flexibility is present between the parallel motors. Flexibility reduces the fighting force to insignificantly small. | | Motors tend to fight against each other during operation due to lead screw pitch error or feedback device inaccuracies || This is not a problem in systems where some mechanical flexibility is present between the parallel motors. Flexibility reduces the fighting force to insignificantly small. | ||
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− | | Servo motor tuning may need to be done for single axis at the time. || This is possible due to the same mechanical flexibility reason as above servo fighting issue. The trick is to use very small travel when tuning the motors to avoid causing excess bending forces to the mechanics | + | | Servo motor tuning may need to be done for single axis at the time. || This is possible due to the same mechanical flexibility reason as above servo fighting issue. The trick is to use very small travel when tuning the motors to avoid causing excess bending forces to the mechanics. |
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− | | Motor fault stopping must be synchronized to avoid only one motor driving the axis and | + | | Motor fault stopping must be synchronized to avoid only one motor driving the axis and one acting only as load which may cause excessive stress to mechanics. || This is possible by electrically wiring fault stop output signal to parallel axis enable input (some external logic may be needed). Another way is to connect fault output to the master [[controller]] which will disable all axis with low latency once fault occurs. See more info in the next chapter. |
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| Motor initialization must not produce any uncontrolled motion. || This is problem only with AC/BLDC motors without Hall sensors and [[homing]] function with automatic start after drive power-on. See more info in the next chapter. | | Motor initialization must not produce any uncontrolled motion. || This is problem only with AC/BLDC motors without Hall sensors and [[homing]] function with automatic start after drive power-on. See more info in the next chapter. | ||
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==Setting up== | ==Setting up== | ||
Servo tuning for parallel motors requires special attention as motors are not allowed to move freely without synchronism. However tuning the motors separately is usually still possible as gantry has some flexibility allowing one motor move just enough for tuning purposes. | Servo tuning for parallel motors requires special attention as motors are not allowed to move freely without synchronism. However tuning the motors separately is usually still possible as gantry has some flexibility allowing one motor move just enough for tuning purposes. | ||
− | + | ?==Note on AC/BLDC/linear motors=== | |
Unlike DC motors, AC & BLDC & linear motors (synchronous motors) require alignment of magnetic angle/position to windings, a.k.a [[Phasing a.k.a. phase search|phasing]]. This can be generally achieved by using one of the following methods: | Unlike DC motors, AC & BLDC & linear motors (synchronous motors) require alignment of magnetic angle/position to windings, a.k.a [[Phasing a.k.a. phase search|phasing]]. This can be generally achieved by using one of the following methods: | ||
#By driving current to windings and letting motor to settle to certain magnetic angle | #By driving current to windings and letting motor to settle to certain magnetic angle | ||
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It is highly recommended to do basic setup of motors with unconnected load (non mounted shaft). Basic setup includes setting motor parameters, torque tuning and, most importantly, testing motor's ability to stand still in position mode from the moment of power-up to entering into step response tuning. | It is highly recommended to do basic setup of motors with unconnected load (non mounted shaft). Basic setup includes setting motor parameters, torque tuning and, most importantly, testing motor's ability to stand still in position mode from the moment of power-up to entering into step response tuning. | ||
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