StepperMotor
Speed - Torque Curves for Stepper Motors (orientalmotor.com)
轴承
Stepper motor type¶
- VR
- PM
- HB
PM¶
HB¶
步进电机的原理与特性¶
转矩的产生及负载角¶
PM型电机
Stepper Motor & Drive Circuit Specification/Selection/Test¶
Motor Specification (ME)¶
Based on calculated mechanical requirements, specify: * Torque at planned operational speeds (Plan for 50% margin for tolerances and future requirements.) * Step angle * Step size * General pinion requirements * Duty cycle (full power / low power / off) * Max physical size * Radial load on bearings of motor (consider pulley, coupling, etc.) * Ramp-up/down requirements (e.g. main platen stepper may need to ramp up very fast)
Motor Selection (ME)¶
Consider: * Adequate margin on all specs * Rules of thumb re: current: - Never drive with current >1.4x max current - Avoid using with current <50% of max current (Motor -behavior may not be as consistent as at higher currents.) * Worst case thermal heating due to both: - winding resistance (I2R) - magnetic flux due to current chopping * Preferred vendors * Possible second sourcing * Cost
Driver IC / Circuit Selection (EE)¶
Consider: * Adequate margin on all specs * Thermal heating of IC * Preferred vendors * Possible second sourcing * Cost
Torque Curve Generation¶
Can be generated by either motor vendor or by us: * Use our planned driver IC/circuit * For each step size we’ll use, go up to our max operational frequency or the frequency where the current waveform is no longer chopping, whichever is higher.
Build & Test Prototype System¶
Testing includes: * Measure actual torque of mechanism: - Measure static torque by attaching a torque watch to mech & turning. - Measure dynamic torque using Himmelstein torque transducer at multiple speeds. - How do measurements compare to original calculations? Do we need to modify the motor requirements? * Confirm quality of current waveform: - Tune current setting, decay mode, off time, etc. in driver as required. - Check if operation is ever at a step rate such that the current waveform is no longer chopping. If so, look carefully at how much torque we are really getting out of the motor, especially over the range of motor electrical characteristics (e.g., max inductance that would reduce the peak current reached, and therefore reduce the torque). * Confirm that current used is not excessively above appropriate margin (which can result in unnecessary vibration and acoustic noise). * Confirm appropriate speed ramp-up and ramp-down. * Confirm that overall motion quality is acceptable (ramp-up, steady state, ramp-down) * Search for and document all motor resonance frequencies (with the motor in the system). * Measure max temperatures of motor and driver IC. If possible, use motor samples with thermocouples installed internally to measure the internal winding temperature.
Document all test results, and update analysis/calculations of all tolerances, including mechanical torque load, current-to-torque “conversion” by motor, and electrical characteristics of driver IC/circuit. Perform additional testing as required to validate tolerances (e.g., how do resonant frequencies vary across torque load tolerance? Operation must avoid the entire resonant frequency range.)