First, let's explain these parameters.
Among the basic parameters of the positioning parameters, there are four related parameters: unit setting, number of pulses per revolution, amount of movement per revolution, and unit multiplier.
Unit settings
This parameter sets the unit of command for positioning control, and can be set to mm, inch, degree, or pulse. If set to pulse, then the positioning command will be issued in pulse units, and we should then focus on how many pulses the program should send. If set to millimeters (mm), then the positioning command can directly instruct the controlled object (such as a leadscrew) to move a certain distance, without needing to worry about how many pulses the program should send.
2. The number of pulses per revolution parameter is set to the number of pulses required per revolution of the motor shaft.
3. The "Traction per Revolution" parameter sets the distance the controlled object (such as a leadscrew) moves when the servo motor rotates one revolution. For example, if the leadscrew pitch is 2mm and the servo motor directly drives the leadscrew without a speed reducer, then the leadscrew moves 2mm when the servo motor rotates one revolution. Therefore, this should be set to 2000um (the aforementioned "unit setting" should be set to mm).
4. Unit multiplier
This parameter allows for adjustments when the movement per revolution exceeds the set range. When using positioning modules like the QD75, the pulses per revolution setting range is 0-65535, while the movement per revolution depends on the unit. If the unit is pulses, the range is 1-65535 pulses; if the unit is mm, the range is 0.1-6553.5µm. Clearly, firstly, if using a JE servo, the pulses per revolution must be set to 131072! Secondly, if the leadscrew pitch exceeds 7mm, the movement per revolution cannot be set.
In QD75, if the displacement of each pulse is less than 1, a change in the command frequency will occur. Smaller settings...
This will increase the variation and may cause machine vibration. If the displacement of each pulse becomes less than 1, then...
The electronic gear function of the drive unit is used and set so that the displacement of each pulse is greater than or equal to 1.
This means that AL*AM/AP>=1.
II. A practical example
One device has a servo axis using an MR-JE motor. The JE motor encoder resolution is 131072, and the lead screw pitch is 20mm. The customer's parameters are: QD75 settings: pulses per revolution set to 1 pulse, movement per revolution set to 10µm, unit multiplier 1; servo amplifier side electronic gear ratio set to 8192/125; Pb: lead screw pitch; n: reduction ratio; Pt: motor encoder resolution (pulses/revolution).
Triangle L0: Feed amount per pulse (mm/pulse)
Triangle S: Feed rate per motor revolution (mm/r)
CMX/CDV = Trigonometric L0 * Pt / Trigonometric S = Trigonometric L0 * Pt / (n * Pb)
CMX/CDV=(0.01*131072)/20=8192/125
The QD75 has its pulses per revolution (AP) set to 1 pulse, its movement per revolution (AL) set to 10µm, and its unit multiplier (AM) set to 1. Therefore, the number of pulses required for one revolution of the motor is: Pulse equivalent = Lead / (Reduction ratio * Number of positioning module pulses per revolution of the servo motor). In this example, pulse equivalent = AL/AP = 0.01/1 = 0.01mm = 10µm. The number of pulses required for one revolution of the servo motor = 20/0.01 = 2000.
The formula is verified again: Servo-side electronic gear ratio CMX/CDV = Motor encoder resolution / One motor revolution
The required number of pulses is 131072/2000 = 8192/125 = 65.536
This involves taking the known motor encoder resolution and screw lead, selecting the pulse equivalent, setting the AP, AL, and AM of the QD75, and then calculating the servo-side electronic gear ratio.
The parameters Xiaoming set are:
The pulse count per revolution is set to 32768 pulses, the movement per revolution is set to 2000µm, and the unit multiplier is set to 10; the electronic gear ratio on the servo amplifier side is set to 4/1.
CMX/CDV = Trigonometric L0 * Pt / Trigonometric S = Trigonometric L0 * Pt / (n * Pb)
CMX/CDV=[(20/32768)*131072]/20=4/1
Because the number of pulses per revolution is set to 32768 pulses, the movement per revolution is set to 2000µm, and the unit multiplier is 10, the number of pulses required for one revolution of the motor is: Pulse equivalent = Lead / (Reduction ratio * Number of pulses per revolution of the servo motor). Pulse equivalent = 20 / 32768 (mm/pulse) Number of pulses per revolution of the servo motor = 20 / (20 / 32768) = 32768
The formula is verified again: Servo-side electronic gear ratio CMX/CDV = Motor encoder resolution / One motor revolution
Required pulse count: 4/1 = 131072/32768 = 4
Xiaoming calculated the pulse equivalent as 20/32768 by setting AP=32768, AL=2000, and AM=10 for QD75, and then calculated the electronic gear ratio according to the formula.
If calculated using the following formula, the results of the two settings above are the same:
Electronic gear ratio = Servo-side electronic gear ratio * Pulses per revolution / (Motion per revolution * Unit multiplier)
Substituting the customer's parameters into the formula above: Electronic Gear = (8192/125) * (2000/20) =
32768/5 (all replaced with actual numbers, not the numbers set in QD75)
Substituting Xiao Chen's parameters into the formula above: Electronic Gear = (4/1) * (32768/20) =
32768/5 (Substitute the numbers from QD75 into the calculation.)
Based on the two methods above, the pulse equivalent is different, and the customer's pulse equivalent setting is better:
Customer pulse equivalent = 0.01mm = 10um (to make it more intuitive)
Xiao Chen's pulse equivalent = 0.0006103mm = 0.6103um (the setting is average).
Let's re-understand the customer's settings: If the pulse equivalent is selected as 10um, and the lead is 20mm, then according to the formula: Pulse equivalent = Lead / (Reduction ratio * Number of pulses per revolution of the servo motor).
The number of pulses per revolution of the servo motor is calculated as 20/0.01 = 2000.
Then set AP to 2000, AL=20000, and AM=1. Does that make it easier to understand?
The customer sets AP to 1 pulse, AL to 10µm for the movement per revolution, and AM to 1x. In reality, it's just a matter of simplifying AP and AL. (The above formula applies to pulse-type positioning products such as QD75. For QD77MS, there is no servo-side electronic gear ratio, which means that the movement per revolution, the number of pulses per revolution, and the unit ratio constitute the electronic gear.)
The above example illustrates:
1. The values of the number of pulses per revolution and the amount of movement per revolution can be simplified.
2. If the setting value is out of range, it can be adjusted by the electronic gear ratio and unit multiplier on the servo side.
Pulse equivalent = Lead / (Reduction ratio * Number of driver pulses per revolution of the servo motor). Calculate the pulse.
Equivalent (Electrical positioning accuracy)
The pulse equivalent can also be set manually. When setting the pulse equivalent, be sure to calculate the motor's maximum speed.
The speed is then limited in the PLC to the maximum speed at which the positioning module sends pulses, corresponding to the rated speed of the motor.
The following points are incorrect.
The statement "Pulse equivalent = pitch / (transmission ratio * encoder resolution * electronic gear ratio)" is incorrect.
1) The pulse equivalent is independent of the encoder resolution; the encoder pulse is merely a feedback mechanism to the control pulse.
Tie.
2) The equivalent value will be different depending on the number of pole pairs of the servo!
3) The pulse equivalent is only related to the lead screw pitch, reduction ratio, electronic gear ratio, and the number of control pulses per revolution of the servo.
related!
Given: Slide lead 12mm, motor encoder resolution 20480 pulses/r, controller can receive...
Linear differential signals below 500kpps; can also receive open-collector signals below 100kpps. Motor
Rated speed 3000 r/min
The slide table has a repeatability of +/-0.02mm, and the motor is controlled by the point-to-point pulse generator of the FX3GA body. The motor and slide...
The machine uses a coupling for connection; there is no speed reducer. (FX3GA, open collector 100kpps pulse.)
Option A:
Assume the pulse equivalent is 0.001 mm.
CMX/CDV = Trigonometric L0 * Pt / Trigonometric S = Trigonometric L0 * Pt / (n * Pb)
CMX/CDV=（0.001*20480）/12=128/75=1.7066
It conforms to the range of electronic gear ratios.
f: Frequency of the input pulse (pps)
No: Servo motor speed (r/min)
Pt: Motor encoder resolution (pulses/revolution)
f*CMX/CDV=(No/60)*Pt
No=100000*（128/75）*60/20480=500r/min
When the pulse equivalent is selected as 0.001mm, the servo-side electronic gear ratio is 128/75, and the PLC's highest pulse...
100,000 pps, the motor speed is 500 r/min, which is below the motor's rated speed; the speed is a bit...
Slow is clearly unacceptable.
Option B: Set the pulse equivalent to 0.01mm.
CMX/CDV = Trigonometric L0 * Pt / Trigonometric S = Trigonometric L0 * Pt / (n * Pb)
CMX/CDV=（0.01*20480）/12=256/15=17.066
It conforms to the range of electronic gear ratios.
f: Frequency of the input pulse (pps)
No: Servo motor speed (r/min)
Pt: Motor encoder resolution (pulses/revolution)
f*CMX/CDV=(No/60)*Pt
No=100000*（256/15）*60/20480=5000r/min
This indicates that when the pulse equivalent is selected as 0.01mm, the servo-side electronic gear ratio is 256/15, and the PLC's highest pulse...
The speed is 100,000 pps, and the motor speed is 5,000 r/min, which exceeds 3,000 r/min. To use this configuration, the maximum number of pulses of the PLC must be limited to 50 kpps. The motor speed is 2,500 r/min.
Option C:
Assume the pulse equivalent is 0.005 mm.
CMX/CDV = Trigonometric L0 * Pt / Trigonometric S = Trigonometric L0 * Pt / (n * Pb)
CMX/CDV=（0.005*20480）/12=128/15=8.533
It conforms to the range of electronic gear ratios.
f: Frequency of the input pulse (pps)
No: Servo motor speed (r/min)
Pt: Motor encoder resolution (pulses/revolution)
f*CMX/CDV=(No/60)*Pt
No=100000*（128/15）*60/20480=2500r/min
This indicates that when the pulse equivalent is selected as 0.005mm, the servo-side electronic gear ratio is 128/15, and the PLC's maximum pulse...
100,000 pps, the motor speed is 2,500 r/min, and the speed is within 3,000 r/min, so there is no need to control the maximum number of pulses of the PLC.
Methods for setting electronic gear ratio and pulse equivalent
1. First, set the pulse equivalent.
Pulse equivalent = Lead / (Reduction ratio * Number of driver pulses per revolution of servo motor)
2. Calculate the electronic gear ratio on the servo side.
CMX/CDV = ΔL0*Pt/ΔS = ΔL0*Pt/(n*Pb) conforms to the range of electronic gear ratios.
3. Verify that the motor speed is equal to or lower than the rated speed when the PLC positioning module is at maximum pulse count. If the motor speed is fine, there is no need to control the PLC's maximum pulse count. Otherwise, the PLC's maximum pulse count needs to be controlled.
f*CMX/CDV=(No/60)*Pt
f: Frequency of the input pulse (pps)
No: Servo motor speed (r/min)
Pt: Motor encoder resolution (pulses/revolution)
f*CMX/CDV=(No/60)*Pt
CMX/CDV = Motor encoder resolution / Number of pulses required for one revolution of the motor
Pulse equivalent = Lead / (Reduction ratio * Number of driver pulses per revolution of servo motor)
The electronic gear ratio of the servo controller is obtained.
Pb: Lead screw pitch; n: Reduction ratio
Pt: Motor encoder resolution (pulses/revolution)
Triangle L0: Feed amount per pulse (mm/pulse)
Triangle S: Feed rate per motor revolution (mm/r)
CMX/CDV = Trigonometric L0 * Pt / Trigonometric S = Trigonometric L0 * Pt / (n * Pb)
f: Frequency of the input pulse (pps)
No: Servo motor speed (r/min)
P: Motor encoder resolution (pulses/revolution)
f*CMX/CDV=(No/60)*Pt
The above is a brief introduction to electronic gear ratios. When designing and selecting a gear ratio, we need to understand the following points.
Data on the slide's lead, maximum speed, repeatability, and load capacity. Selection of a servo motor.
When designing a servo controller, it's essential to understand its power, input voltage, type of received pulses, and the motor's rated speed.
Degree, maximum received pulse value. Host computer, positioning module pulse output type, maximum number of pulses output.
Pulse logic, etc. Our goal is to achieve both accurate motor positioning and high speed. Only then will the machine's UPH (Uptime Per Hour) meet the standard.
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