xiaomupeng2009 Posted March 6, 2011 Share Posted March 6, 2011 when I adjust the pid parameters, what is it relationship between the step move size and time and the motor accuracy? because different step move size and time will have different PID parameters for the same motor! how can i konw which move size and time will be the most suitable? Link to comment Share on other sites More sharing options...
Sina.Sattari Posted March 6, 2011 Share Posted March 6, 2011 xiaomupeng2009, When you do a step move, by default the tuning software is showing the commanded position and actual position of the motor. You can also select to see the "Servo Command" on the right hand vertical axis. This will help you identify an acceptable step size. The servo effort shows how the PMAC is responding to the step command by commanding different torque/force command to the amplifier. The size of the step and the time to achieve that is concluded as the bandwidth of the system. If you perform an auto tuning, the Tuning software will give you a conservative bandwidth. When you try to tune your motor manually, try to get to 4 times the bandwidth that auto tuning came up with. (bandwidth is shown as natural frequency under the step result graph) Through out the step tests, you have to make sure that your servo command is not being saturated for a long time during the step move. Although by definition, you'll have an instantaneous saturation in servo command at the beginning of the step move, if your Kp is too high or step is too big, you'll have saturation. A step size for a rotary motor is about 1/2 revolution and for a linear motor, is about 1/4 to 1/2 of electrical cycle length. Regards, Link to comment Share on other sites More sharing options...
xiaomupeng2009 Posted March 8, 2011 Author Share Posted March 8, 2011 xiaomupeng2009, When you do a step move, by default the tuning software is showing the commanded position and actual position of the motor. You can also select to see the "Servo Command" on the right hand vertical axis. This will help you identify an acceptable step size. The servo effort shows how the PMAC is responding to the step command by commanding different torque/force command to the amplifier. The size of the step and the time to achieve that is concluded as the bandwidth of the system. If you perform an auto tuning, the Tuning software will give you a conservative bandwidth. When you try to tune your motor manually, try to get to 4 times the bandwidth that auto tuning came up with. (bandwidth is shown as natural frequency under the step result graph) Through out the step tests, you have to make sure that your servo command is not being saturated for a long time during the step move. Although by definition, you'll have an instantaneous saturation in servo command at the beginning of the step move, if your Kp is too high or step is too big, you'll have saturation. A step size for a rotary motor is about 1/2 revolution and for a linear motor, is about 1/4 to 1/2 of electrical cycle length. Regards, i am sorry! i want to what is it electrical cycle length?can you tell me the detail? thank you! Link to comment Share on other sites More sharing options...
Guest majidy Posted March 8, 2011 Share Posted March 8, 2011 xiaomupeng2009, When you do a step move, by default the tuning software is showing the commanded position and actual position of the motor. You can also select to see the "Servo Command" on the right hand vertical axis. This will help you identify an acceptable step size. The servo effort shows how the PMAC is responding to the step command by commanding different torque/force command to the amplifier. The size of the step and the time to achieve that is concluded as the bandwidth of the system. If you perform an auto tuning, the Tuning software will give you a conservative bandwidth. When you try to tune your motor manually, try to get to 4 times the bandwidth that auto tuning came up with. (bandwidth is shown as natural frequency under the step result graph) Through out the step tests, you have to make sure that your servo command is not being saturated for a long time during the step move. Although by definition, you'll have an instantaneous saturation in servo command at the beginning of the step move, if your Kp is too high or step is too big, you'll have saturation. A step size for a rotary motor is about 1/2 revolution and for a linear motor, is about 1/4 to 1/2 of electrical cycle length. Regards, i am sorry! i want to what is it electrical cycle length?can you tell me the detail? thank you! Electrical Cycle is what is also called commutation cycle and is equal to the number of counts that motor travels per one full sinewave. It is equal to number of counts per mechanical revolution divided by number of pole pairs. If you don't have the specification of the motor, You can measure this by energizing each phase of the 3 phase motor sequentially and measuring the number of counts like this: Step1:Energizing Phase U (when Motor locks, this is your reference point) Step2:Energizing Phase V Step3:Energizing Phase W Step4:Energizing Phase U (when motor locks, measure the total number of counts motor traveled and this is your electrical cycle length) Link to comment Share on other sites More sharing options...
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